Journal of Electromyography and Kinesiology
Volume 22, Issue 1 , Pages 1-12, February 2012

Methodology of electromyographic analysis of the trunk muscles during walking in healthy subjects: A literature review

Vrije Universiteit Brussel, Faculty of Physical Education and Physiotherapy, Advanced Rehabilitation Technology and Science (ARTS), Belgium

Received 3 November 2010; received in revised form 4 March 2011; accepted 13 April 2011. published online 30 May 2011.

Article Outline

Abstract 

Purpose

To review and discuss the literature about the use of trunk muscle electromyography – including the use of surface or fine-wire electrodes, site of application and muscle selection – during gait analysis in healthy subjects.

Methods

The databases Pubmed, Web of Knowledge and Cochrane Library were searched. Articles were included when EMG activity of at least one trunk muscle was measured in healthy subjects during walking.

Results

In the 33 selected articles 491 healthy subjects walked with different velocities on a treadmill and/or overground. The activity of the M. erector spinae, M. multifidus, M. obliquus externus and internus, M. rectus abdominus, M. trapezius, M. latissimus dorsi, M. transversus abdominus, M. iliopsoas and M. quadrates lumborum was measured. Twenty-nine studies used surface electrodes, one study fine-wire electrodes, and the other three studies used a combination. There is no consensus on the exact placement site of the electrodes.

Conclusion

Surface electrodes were used more often than fine-wire electrodes and the descriptions of the electrode locations were mostly vague and not consistent among the different studies. There is need for further research to make specific recommendations about the type of electrodes in combination with the optimal locations of application of these electrodes.

Keywords: Electromyographic activity, Trunk muscles, Gait

 

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1. Introduction 

Gait recovery is one of the most important goals for rehabilitation (Carda et al., 2009, Globas et al., 2009, Kelleher et al., 2009). Gait analysis is meaningful to specify the rehabilitation outcome and the therapeutic goals (Jackson et al., 2008). Clinical assessment by means of the 10-m walk test, the 6-min walk test and the Functional Independence Measure-Locomotor (FIM-L) may give an overall evaluation of the patient’s gait (Jackson et al., 2008), but for a qualitative in-depth evaluation, there is a need of biomechanical analysis (Frigo and Crenna, 2009, Mcginley et al., 2009). For this purpose, electromyography (EMG) is a frequently used technique to evaluate the activity of the human muscles during different motor tasks (Frigo and Crenna, 2009).

Compared to the extensive evidence that exists on EMG activity of the lower limb muscles and their spinal regulation mechanisms (central pattern generators), only a few studies have been conducted with relation to the activity of the trunk muscles during walking (Capaday, 2002, Dietz, 2008). Moreover, the type of electrodes and the electrode locations used for the trunk muscles are not consistent in different studies (De Seze and Cazalets, 2008).

However, trunk control is very important during gait (Kendall et al., 2005), since two thirds of the body mass is situated above the waist and because of the relevancy of gait control and falls in patients and in the elderly (Grabiner et al., 2008). The trunk musculature consists of different layered groups of moving and stabilizing muscles (Kendall et al., 2005). It is a behavioral challenge for humans to maintain equilibrium, which requires adequate coordination between head, trunk and leg movements. The back muscles keep the trunk erect and provide an appropriate equilibrium between flexibility and stiffness during walking. Trunk muscles are sequentially activated by a motor command running along the spinal cord during various types of locomotion or rhythmic motor tasks (De Seze et al., 2008). Virtually all muscles work together to create the ‘balance’ in stiffness needed to ensure sufficient stability in all degrees of freedom (Mcgill et al., 2003).

There are two general recommendations on the placement of surface EMG electrodes: (1) with respect to the longitudinal location of the sensor on the muscle, place the sensor halfway the (most) distal motor endplate zone and the distal tendon and (2) with respect to the transversal location of the sensor on the muscle, place the sensor at the surface away from the ‘edge’ with other subdivisions or muscles so that the geometrical distance of the muscle to these subdivisions and other muscles is maximized (Seniam, 2010). For dynamic contractions, this location represents a balance between two competing factors: (1) the need to compensate for muscle shortening, which can bring the innervation zone closer to the electrode and (2) the necessity to avoid the increased contribution from potentials generated by the muscle fiber-tendon end effects (Kamen and Gabriel, 2010; Martin and Macisaac, 2006, Schulte et al., 2004). SENIAM recommended applying the inter-electrode distance of bipolar surface EMG electrodes with an inter-electrode distance of 20mm. This could avoid unstable recordings due to tendon and motor endplate effects (Seniam, 2010).

Despite the international recommendations on the placement of the surface EMG electrodes on the muscle belly (Hermens et al., 1999, Seniam, 2010) and studies to determine the best electrode locations for the trunk muscles (De Nooij et al., 2009, De Seze and Cazalets, 2008) the literature is not consistent on these recommendations, what makes it difficult to compare the results of different studies.

A number of studies reported the importance of the electrode location site in different parts of the human body like the head and neck musculature (Armijo-Olivo et al., 2007, Castroflorio et al., 2005, Falla et al., 2002, Sommerich et al., 2000), the lower limb musculature (Campanini et al., 2007, Hogrel et al., 1998, Roy et al., 1986), the upper limb musculature (Cote and Mathieu, 2000, Li and Sakamoto, 1996, Mercer et al., 2006), and the back musculature (De Seze and Cazalets, 2008). The authors of the different studies reported that the electrodes should be placed with extreme care and consistency to reduce cross-talk of adjacent muscles and to make the reproducibility of the EMG protocol and the comparability between different studies possible. In most of previous studies the effect of electrode location has been investigated in isometric contractions, but the study of Campanini et al. (2007) reported the effect of electrode location on EMG signal envelope in leg muscles during gait. They concluded that the estimate of muscle activation intensity during gait from surface EMG is variable with location of the electrodes while timing of muscle activity is more robust to electrode displacement and can be reliably extracted in those cases in which crosstalk is limited (Campanini et al., 2007).

No former reviews were found in the literature about the electrode placement on the trunk muscles during gait. It would be interesting to come to a consensus in the literature about the application site for the EMG electrodes on the trunk muscles, and to formulate specific recommendations to make the EMG protocols in different studies more homogenous, to increase the reproducibility of the protocols and to make the data of the EMG measurements in different populations more comparable.

The aim of the present paper is to review the literature regarding the EMG registration of the activity of the trunk muscles during gait analysis in healthy subjects. We will review and discuss the muscle selection, the use of surface or fine-wire electrodes and the application sites of the electrodes in order to establish a recommendation for optimal localization of the electrodes.

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2. Research questions 

The research questions of this review are:

1.Which trunk muscles have been EMG-recorded during walking over ground or on a treadmill in healthy subjects?

2.Which trunk muscles were measured with surface electrodes or fine-wire electrodes, respectively?

3.What are the exact anatomical locations described in the literature for placement of the fine-wire and surface electrodes?

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3. Methods 

3.1. Search strategy 

A computerized search in different electronic databases was conducted such as: Pubmed (Medline), Web of Knowledge (Web of Science) and Cochrane Library (Cochrane Controlled Trials Register) for English, French, German and Dutch articles published before March 2010. Mesh-terms and Key-words were used and sorted following the PICO (Population, Intervention, Comparison, Outcome) method (Table 1) (Cbo, 2010). Beside the electronic databases, the reference lists in the articles and narrative reviews were scanned separately for relevant publications.

Table 1. Mesh-terms and Key-words were sorted following the PICO (Population, Intervention, Comparison, Outcome) method and introduced in different databases (Pubmed, Web of Science and Cochrane Library).
P (Population)I (Intervention)C (Comparison)O (Outcome)
Healthy AND adults(“Walking”[Mesh] OR “Gait”[Mesh] OR walk OR “Locomotion”[Mesh]) AND (treadmill OR over ground OR walkway OR floor)/(“Electromyography”[Mesh] OR muscle activity) AND (“Abdominal Muscles”[Mesh] OR “Back”[Mesh] OR “Muscle, Skeletal”[Mesh] OR trunk)

3.2. In- and exclusion criteria 

Included were clinical trials or case reports with healthy adult (+18years) subjects without gait problems, walking (not running) independently over ground or on a treadmill while EMG activity of at least one abdominal and/or back muscle (excluding cervical muscles) was recorded with the use of fine-wire and/or surface electrodes. Studies investigating subjects with orthopedic or neurological problems or any other cause of gait dysfunction as well as studies on children (−18years) or animals were excluded.

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4. Results 

Ultimately, 33 studies were included in this review, of which 32 English articles and 1 German article (Table 2). The flowchart (Fig. 1) presents an overview of the search strategy.

Table 2. Descriptive analysis: In the 33 selected studies 491 healthy subjects walked with different velocities (1–9kmph) on a treadmill (22 studies), overground (six studies) or both (four studies). Twenty-four studies (72.7%) described an exercise-period (familiarization) before measuring. 29 studies used surface electrodes, one study fine-wire electrodes and the other three used a combination.
Author (year)StudyEMG
Aim of the studyHealthy subjectsWalking speed (kmph)TM/OGFam. (min)S/FWElectrode type (active diameter)Side
Anders et al., 2007Trunk muscle activation patterns during walking152/3/4/5/6TM5sAg–AgCI (10mm)R+L
Anders et al., 2009Sex-specific co-ordination patterns of trunk muscles1062/3/4/5/6TM5sAg–AgCI (10mm)R+L
Barton et al., 2009Effect of heel lifts on trunk muscle activation154±0.58OG (8m WW)YessAg–AgCI (15mm)L
Cappellini et al., 2006Motor patterns in walking and running8 (=Ivanenko et al., 2008)3/5/7/9TMFews/R
Carlson et al., 1988Back muscle activity during voluntary modifications of trunk movements95.4TMYessBipolarR+L
Ceccato et al., 2009Trunk activity during gait initation and walking9NaturalOG (11m WW)/sTripolar (10mm)R+L
Cromwell et al., 1989Loads on lumbar trunk during walking1072/120 steps/minOG (8.25m WW)/sBipolar Ag–AgCIR+L
Cromwell et al., 2001Kinematic and EMG patterns of upper body8NaturalOG (4.57m WW)/sBipolar Ag–AgCI (8mm)R
De Seze et al., 2008Sequential activation of axial muscles during rhythmic behavior95TM2sTripolar (10mm)R (+L)?
De Seze and Cazalets, 2008Skin electrode placement ES35?/sTripolar (10mm)?
Dofferhof and Vink, 1985Stabilisation function ES during walking with loading trunk64/5.5 (TM)/±4(OG)TM/OG (10m WW) (n=4)/sAg (6mm)R+L
Finch et al., 1991Influence of body weight support on gait104.9TM20s/R
Ivanenko et al., 2004Muscle activation patterns during locomotion at different speeds and gravitational loads6 (ES n=5; RA n=4; OE n=3; RA n=2; LD n=3; TRAP n=l)1/2/3/5TMFews/R?
Ivanenko et al., 2005Coordination of locomotion with voluntary movements8 (ES Tl n=5, T9 n=4, L2 n=8; LD n=8; RA n=7, OE n=8, OI n=4; TRAP sup.Natural (5.2±0.8) (OG) / 5/ 1–7 (TM)OG (7m WW) (n=8) /TM (n=3)Few (OG)s/R
Ivanenko et al., 2006Spinal cord maps of spatiotemporal α-motoneuron activity13 (ES Tl n=6, T9 n=5, L2 n=12; LD n=12; RA n=ll, OE n=12, OI n=5; TRAP sup. n=8, inf. n=5; ILIO n=6)1/ 2/ 3/ 5/ 7 / (n=3) linearly ↑and ↓ speed 1 to 7 kmph (steps of 0.4)TMFews/R
Ivanenko et al., 2008Spatiotemporal organization of α-motoneuron activity8 (=Cappellini et al., 2006)3/ 5/ 7/ 9 / linearly ↑ and ↓ speed 3 to 10 kmph (steps of 0.4) (TM) / (n=4) 3.4-TM/OG (7m WW)Fews/R
Lamoth et al., 2006aConsequences of low back pain on trunk-pelvis coordination.14Natural / 1.4 to 7 (↑ 0.8)TMFewsAg–AgCI (10mm)R+L
Lamoth et al., 2006bTrunk-pelvis coordination and ES activity in low back pain126.2/1.4/3.8/5.4/2.2/4.6TMFewsAg–AgCI (10mm)R+L
Li and Hong, 2007Walking in negative-heeled shoes134.79TM/sAg–AgCIR or L
Masumoto et al., 2004EMG analysis of walking in water63.6/4.79/6TMYessAg–AgCI (8mm)R
Merkle et al., 1998Factor analysis to identify neuromuscular synergies106.4TM/s/L
Olson, 2010Trunk extensor fatigue14PreferredOG (10m WW)/sBipolar Ag-AgCI (10mm2)R
Prentice et al., 2001Artificial neural network model14.6OG (12m WW)/s/R+L?
Saunders et al., 2004Postural and respiratory activation of trunk muscles7 (=Saunders et al., 2005)3.6/7.2TM2FW/SBipolar Ag–AgCI/ Teflon, stainless steel 75μm (0.7×32mm or 0.7x70mm)R/R+L
Saunders et al., 20053D lumbo-pelvic kinematics and trunk muscle EMG across range of speeds7 (=Saunders et al., 2004)3.6/7.2TM2FW/S/Ag–AgCIR/R
Shung et al., 2009Shock waves and muscle activity at initial contact on walk-run transition3080/ 90/ 100/ 110/ 120% of preferred speed (1.86±0.14)TM2s/?
Thorstensson et al., 1982Movements and muscle activity patterns of the trunk at various speeds73.6–9TMYesFW(/S ⁎)Bipolar, Teflon, stainless steel (150μm)R+L
van der Hulst et al., 2010Trunk muscle activity in low back pain321.4–5.4 Cr (↑ 0.8)TMMax. 5sBiPolarR+L
Vink and Karssemeijer, 1988Low back muscle activity and pelvic rotation during walking114TM10sBipolar gold (7.5mm)R+L
Vogt and Banze, 1999Trunk and head muscles during gait over-ground and on treadmill204.5 (TM)/4.75±1.69 (OG)TM/OG (8m WW)10 to 15 (TM), Yess/R+L
Vogt et al., 2003Neuromuscular control of walking with low back pain164.5TMYessAg–AgCIR or L
Waters and Morris, 1972Electrical activity of trunk muscles during walking104.39/5.29TMYesFWStainless steelR
White and Mcnair, 2002Cluster analysis to identify patterns of activity384TM10–15s/R

TM: treadmill, OG: overground, Fam.: familarization period, R: right, L: left, ES: erector spinae, LD: latissimus dorsi, TRAP: trapezius, sup.: superior part, inf.: inferior part, RA: rectus abdominus, OE: obliquus externus, OI: obliquus internus, ILIO: iliopsoas, S: surface electrodes, FW: fine-wire electrodes.

⁎This study only reported: “In some experiments surface electrodes were used also for the back muscles (placed in a mid position at L4 level)”.

  • View full-size image.
  • Fig. 1. 

    Flow chart search strategy. A computerized search in different electronic databases was conducted: Pubmed, Web of Knowledge and Cochrane Library. Beside the electronic databases, the reference lists in the articles and narrative reviews were scanned separately for relevant publications. 33 studies were ultimately included in the review.

4.1. Descriptive analysis 

The main characteristics of the study protocols and EMG measurements are presented in Table 2.

In the 33 different studies that were included, a total of 491 healthy subjects were measured for trunk EMG during walking. The studies of Cappellini et al. (2006) and Ivanenko et al. (2008) used the same group of subjects during their tests, and so did the two studies of Saunders et al., 2004, Saunders et al., 2005 (Cappellini et al., 2006, Ivanenko et al., 2008, Saunders et al., 2004, Saunders et al., 2005). In six studies the subjects walked overground on a walkway, in 22 studies they walked on a treadmill and in four studies over-ground and treadmill walking were combined. In one study no specification was given about the surface (treadmill or over ground) the subjects walked on during the tests (De Seze and Cazalets, 2008). There was a great variability in the walking velocity. In the over-ground trials subjects walked at their natural preferred speed while in the treadmill trials the subjects walked at different determined speeds between 1 and 9kmph. Twenty-four studies (72.7%) described an exercise-period (familiarization) before measuring. As reported in Table 2 there was a large variation in the protocols used in the studies.

4.2. Research question 1: which trunk muscles have been EMG-recorded during walking over ground or on a treadmill in healthy subjects? 

In 18 studies (54.5%) abdominal and back muscles were recorded while in 15 studies (45.5%) only the back muscles were recorded. The following back muscles were examined: the M. erector spinae (ES) on different spinal levels in 33 studies, the M. multifidus (MF) in eight studies, the M. latissimus dorsi (LD) in six studies, the M. trapezius (TRAP) in seven studies and the M. quadratus lumborum (QL) in one study. The following abdominal muscles were recorded: the M. rectus abdominus (RA) in 17 studies, the M. obliquus externus (OE) in 15 studies, the M. obliquus internus (OI) in 11 studies, the M. transverses abdominus (TA) in two studies and the M. iliopsoas (ILIO) in four studies.

4.3. Research question 2: which trunk muscles were measured with surface electrodes or fine-wire electrodes, respectively? 

Twenty-nine studies (87.9%) used surface EMG electrodes and one study exclusively used fine-wire EMG electrodes (Waters and Morris, 1972). Two other studies used a combination of surface and fine-wire EMG electrodes, but the two techniques were never used in combination on the same muscle (Saunders et al., 2004, Saunders et al., 2005). Only in one study fine-wire electrodes and surface electrodes were used for measurements of the back muscles (Thorstensson et al., 1982). Table 3 presents an overview of the application of surface and fine-wire electrodes for the different muscles. The LD, TRAP and ILIO were only measured with the use of surface electrodes, the QL and TA only with the use of fine-wire electrodes.

Table 3. Overview of the type of electrodes used in different trunk muscles. Surface electrodes were more used than fine-wire electrodes. The LD, TRAP and ILIO were only measured with the use of surface electrodes, the QL and TA only with the use of fine-wire electrodes.
Trunk muscleNumber of studies using surface electrodes (number of subjects)Number of studies using fine-wire electrodes (number of subjects)
ES31 (478)2 (17)
MF4 (138)4 (31)
LD6 (43)0 (0)
TRAP7 (43)0 (0)
QL0 (0)1 (10)
RA16 (292)1 (10)
OE12 (269)3 (24)
OI8 (199)3 (24)
TA0 (0)2 (14)
ILIO4 (27)0 (0)

ES: erector spinae, MF: multifidus, LD: latissimus dorsi, TRAP: trapezius, QL: quadratus lumborum, RA: rectus abdominus, OE: obliquus externus, OI: obliquus internus, TA: transverses abdominus, ILIO: iliopsoas.

4.4. Research question 3: what are the exact anatomical locations described in the literature for placement of the fine-wire and surface electrodes? 

There is no consensus regarding the anatomical placement site of the electrodes on the different muscles of the trunk. Some studies presented no information at all on the exact location of the electrodes placement (Prentice et al., 2001, Shung et al., 2009) while other studies described in detail the precise locations (De Seze et al., 2008, De Seze and Cazalets, 2008, Waters and Morris, 1972, White and Mcnair, 2002). Some studies only referred to other studies about the used placement protocol (Anders et al., 2009, Prentice et al., 2001, Shung et al., 2009, Vogt et al., 2003). Most of the studies give a vague description or only report that the electrodes were placed over the muscle belly or with a specific inter-electrode distance. Table 4 presents an overview of the different reported electrode locations for EMG of the trunk muscles.

Table 4. Overview of different described locations for electrode placement. There is no consensus regarding the anatomical placement site of the electrodes on the different muscles of the trunk. Some studies described in detail the precise locations, while others studies gave no information or only referred to other studies.
Mm.FW/SAuthor (year)Electrode location
(A) Back muscles
ESSAnders et al., 2007(Longissimus) over palpable bulge of muscle (±3cm lateral to midline) lower electrode at L1 level, vertical, IED: 2.5cm
Anders et al., 2009IED: 2.5cm
Barton et al., 2009L4–5 level. One electrode 3cm lateral to L4 SP, another directly above it
Cappellini et al., 2006Over muscle belly at T1, T9 and L2, 2cm lateral to SP
Carlson et al., 1988Level of L3 vertebra
Ceccato et al., 2009Various spine levels (C7, T3, T7, T12 and L3)
Cromwell et al., 1989±Muscle fiber direction, L3 vertebra l level, 3cm lateral to midline
Cromwell et al., 20013cm Lateral to midline at L3 level, IED: 2.1cm
De Seze et al., 2008C7, T3, T7, T12 and L4 level, 2 horizontal points 2 and 3cm from SP of C7 and L4 resp., electrodes on line between them, IED: 1cm
De Seze and Cazalets, 2008Two horizontal points 2 and 4cm from SP of C7 and L4, resp., electrodes on line between them. C7 (prominent SP located at base of nape), T3 (at level of medial angel of scapula), T12 (prominent SP located at thoraco-lumbar junction) and L4 (at level of iliac crest), IED: 1cm
Dofferhof and Vink, 1985Lower electrode of lateral pairs (Iliocostalis) 8cm above interspinal line and 5cm from median plane
Finch et al., 19912cm Lateral to L4–5 interdiskal space, IED: 2cm
Ivanenko et al., 2004L1–L2 level over muscle belly
Ivanenko et al., 2005, Ivanenko et al., 2006, Ivanenko et al., 2008Over muscle belly, T1, T9 and L2, 2cm lateral to SP
Lamoth et al., 2006a(Mainly longissimus) at level of T12, L2 and L4 SP, 3cm lateral from vertebra l column, IED: 2cm
Lamoth et al., 2006bLeft and right of L2 and L4 SP, 3cm lateral from vertebral column, IED: 2cm
Li and Hong, 2007IED of 3cm
Masumoto et al., 2004Longitudinally along muscle fibers, L4 level, over middle point of venter, IED: 2cm
Merkle et al., 1998Over belly
Olson, 2010Parallel with fiber orientation, at L3 level 3cm from L3 SP, IED: 2.5cm
Saunders et al., 2004, Saunders et al., 2005Parallel with muscle fibers, 4cm lateral to midline at level of L2 SP, IED: 1.2cm
Shung et al., 2009, Prentice et al., 2001/
van der Hulst et al., 2010Parallel with muscle fibers, 3cm lateral to 1st lumbar SP and 3cm lateral to 4 th lumbar SP
Vink and Karssemeijer, 19883cm (Spinalis and longissimus), 6cm (longissimus) and 8–9cm (iliocostalis) lateral to L1, 1cm medial to lateral border of ES, 6cm (longissimus) lateral to L3
Vogt and Banze, 1999L3 and T9, longitudinal with fibers
Vogt et al., 2003Longitudinally over muscles, L3 and T12 level, IED: 2cm
White and Mcnair, 2002±Parallel to direction of fibers, lumbar at level of L4/5 interspace, 2cm lateral to midline, IED: 1cm
FWThorstensson et al., 1982Longissimus: 4–5cm lateral to SP, at level of L4 vertebra
Waters and Morris, 1972IL: over 11th and 12th rib, 1/4 distance from angle of rib to spine / IT: over 6th and 7th rib, 1/4 distance from angle of rib to spine / LT: over 9th and 10th rib, 1/2 distance from angle of rib to spine / rotatores: 1cm lateral to 10 th thoracic SP and 2cm below electrode 1, IED: 2cm
MFSAnders et al., 2007Lumbalis: 1cm medial from line between PSIS and 1st palpable lumbar SP, lower electrode at L4 level, parallel to line, IED: 2.5cm
Anders et al., 2009IED: 2.5cm
Dofferhof and Vink, 19852cm Above line passing through both PSIS and at distance of 1.5cm from median plane
Vink and Karssemeijer, 19883cm Lateral to L1 and L3
FWSaunders et al., 2005Deep and superficial: at level of lamina of L4
Saunders et al., 2004Deep and superficial: at level of lamina of L4, ±4cm lateral from midline
Thorstensson et al., 1982Just lateral to SP, at level of L4 vertebra
Waters and Morris, 19722 and 3cm below line joining iliac crests, 1cm lateral to 5th lumbar SP, IED: 2cm
LDSDe Seze et al., 2008, De Seze and Cazalets, 2008Over muscular curve at T12 and along line connecting most posterior point of posterior axillary fold and S2 SP, IED: 2cm
Ivanenko et al., 2004, Ivanenko et al., 2005, Ivanenko et al., 2006Over muscle belly
TRAPSCappellini et al., 2006, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005Over muscle belly, inferior and superior portions
De Seze et al., 2008, De Seze and Cazalets, 2008Over muscular curve, IED: 1cm
Ivanenko et al., 2004Over muscle belly
QLFWWaters and Morris, 19721 and 2cm above and resp. 1 and 2cm lateral to PSIS, IED: 2cm

(B) Abdominal muscles
RASAnders et al., 2007Upper part: 4cm lateral navel, lower electrode at navel level, vertical, IED: 2.5cm
Anders et al., 2009IED: 2.5cm
Cromwell et al., 1989±Muscle fiber direction, L3 vertebral level, 2cm lateral to umbilicus
Cromwell et al., 20012cm Lateral to umbilicus, IED: 2.1cm
Ivanenko et al., 2004Over muscle belly, middle and superior portions
Ivanenko et al., 2005, Ivanenko et al., 2006, Ivanenko et al., 2008, Cappellini et al., 2006Over muscle belly (superior portior), 3cm lateral to umbilicus
Li and Hong, 2007; Cappellini et al., 2006IED: 3cm
Masumoto et al., 2004Longitudinally along muscle fibres, over middle point of venter, IED: 2cm
Olson, 2010Parallel with fiber orientation, 3cm lateral to umbilicus, IED: 2.5cm
Saunders et al., 2004On either side of a line between right and left ASIS, 2cm lateral to umbilicus
Saunders et al., 2005Parallel with muscle fibres, above and below line between ASIS, 2cm lateral to midline, IED: 1.2cm
van der Hulst et al., 20103cm Lateral to midline, midway between processus xyphoideus and umbilicus
White and Mcnair, 2002±Parallel to direction of fibres, at level of ASIS, 2cm lateral to midline, IED: 1cm
FWWaters and Morris, 19721cm Lateral to linea alba (in centre of muscle segment) and 2cm superior to umbilicus, IED: 2cm
OESAnders et al., 2007Directly below most inferior point of costal margin, on line to opposite pubic tubercle, IED: 2.5cm
Anders et al., 2009IED: 2.5cm
Barton et al., 2009Just below most inferior aspect of coastal margin in line with contralateral pubic tubercle
Cromwell et al., 1989±Muscle fiber direction, L3 vertebral level, lateral portion: just above iliac crest, medial portion: 3cm superior to ASIS
Ivanenko et al., 2004, Ivanenko et al., 2005, Ivanenko et al., 2006, Ivanenko et al., 2008, Cappellini et al., 2006,Over muscle belly
Olson, 2010Parallel with fiber orientation, midway between last costal rib and iliac crest at level of umbilicus, IED: 2.5cm
van der Hulst et al., 2010±15cm Lateral to midline, in lower 1/3 part between ASIS and distal border of rib cage
White and Mcnair, 2002±Parallel to direction of fibres, just below rib cage at inferior angle of ribs, IED: 1cm
FWSaunders et al., 2004, Saunders et al., 2005Midway between ASIS and distal border of rib cage
Waters and Morris, 1972Along lower costal margin between anterior axillary and midclavicular lines, IED: 2cm
OISAnders 2007Along horizontal line between both ASIS, medial from inguinal ligament, IED: 2.5cm
Anders 2009IED: 2.5cm
Barton et al., 20091cm inferomedially to left ASIS in line with right ASIS
Cappellini et al., 2006, Ivanenko et al., 2005, Ivanenko et al., 2006, Ivanenko et al., 2008Over muscle belly
White and Mcnair, 2002±Parallel to fiber-direction, 2cm inferior to line joining left and right ASIS, medial to inguinal ligament, lateral to lateral border of rectus sheath, IED: 1cm
FWSaunders et al., 2004, Saunders et al., 2005Midway between ASIS and distal border of rib cage
Waters and Morris, 19723cm Above and perpendicular to inguinal ligaments and 4cm medial to ASIS, IED: 2cm
TAFWSaunders 2004 & 2005Midway between ASIS and distal border of rib cage
ILIOSIvanenko et al., 2005, Ivanenko et al., 2006, Ivanenko et al., 2008, Cappellini et al., 2006Over muscle belly

ES: erector spinae, MF: multifidus, LD: latissimus dorsi, TRAP: trapezius, QL: quadratus lumborum, RA: rectus abdominus, OE: obliquus externus, OI: obliquus internus, TA: transverses abdominus, ILIO: iliopsoas, SP: spinous process, IL: iliocostalis lumborum, IT: iliocostalis thoracic, LT: longissimus thoracic, S: Surface electrodes, FW: Fine-wire electrodes, SP: Spinous process, PSIS: posterior superior iliac spine, ASIS: anterior superior iliac spine, IED: inter-electrode distance.

4.4.1. Musculus erector spinae 

For the ES, surface electrodes were placed on different levels of the spine: C7 (Ceccato et al., 2009, De Seze et al., 2008, De Seze and Cazalets, 2008), T1 (Cappellini et al., 2006, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005), T3 (Ceccato et al., 2009, De Seze et al., 2008, De Seze and Cazalets, 2008), T7 (Ceccato et al., 2009, De Seze et al., 2008), T9 (Cappellini et al., 2006, Ivanenko et al., 2005, Ivanenko et al., 2006, Ivanenko et al., 2008, Vogt and Banze, 1999), T12 (Ceccato et al., 2009, De Seze et al., 2008, De Seze and Cazalets, 2008, Lamoth et al., 2006b, Vogt et al., 2003), L1 (Anders et al., 2007, Van Der Hulst et al., 2010, Vink and Karssemeijer, 1988), L1–L2 (Ivanenko et al., 2004), L2 (Cappellini et al., 2006, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005, Lamoth et al., 2006a, Lamoth et al., 2006b, Saunders et al., 2004, Saunders et al., 2005), L3 (Carlson et al., 1988, Ceccato et al., 2009, Cromwell et al., 1989, Cromwell et al., 2001, Olson, 2010, Vink and Karssemeijer, 1988, Vogt and Banze, 1999, Vogt et al., 2003), L4 (De Seze et al., 2008, De Seze and Cazalets, 2008, Lamoth et al., 2006a, Lamoth et al., 2006b, Masumoto et al., 2004, Van Der Hulst et al., 2010) and L4–L5 (Barton et al., 2009, Finch et al., 1991, White and Mcnair, 2002). The electrodes were placed on the ES with an inter-electrode distance of 3cm (Li and Hong, 2007), 2.5cm (Anders et al., 2009, Anders et al., 2007, Olson, 2010), 2.3cm (Van Der Hulst et al., 2010), 2.1cm (Cromwell et al., 2001), 2cm (Finch et al., 1991, Lamoth et al., 2006a, Lamoth et al., 2006b, Masumoto et al., 2004, Vogt et al., 2003), 1.2cm (Saunders et al., 2004, Saunders et al., 2005) and 1cm (De Seze et al., 2008, De Seze and Cazalets, 2008, White and Mcnair, 2002).

Fine-wire electrodes were implanted with an inter-electrode distance of 2cm (Waters and Morris, 1972) on the level of the 11th and 12th rib, 9th and 10th rib, 6th and 7th rib, 10th thoracic spinous process (Waters and Morris, 1972) and at the level of L4, 4–5cm lateral to the spinous process (Thorstensson et al., 1982).

4.4.2. Musculus multifidus 

For the MF, there was a multitude of protocols for surface electrode placement: one electrode 1cm medial from the line between the posterior superior iliac spine and the 1st palpable lumbar spinous process, the other electrode at L4 level parallel to the line (Anders et al., 2007), 2cm above a line passing through both posterior superior iliac spines and at a distance of 1.5cm from the medial plane (Dofferhof and Vink, 1985) and 3cm lateral to L1 and L3 (Vink and Karssemeijer, 1988). The surface electrodes were placed with an inter-electrode distance of 2.5cm (Anders et al., 2009, Anders et al., 2007). The deep and superficial MF have also been evaluated with fine-wire electrodes (Saunders et al., 2004, Saunders et al., 2005). The fine-wire electrodes were placed 2cm apart, 2 and 3cm below the line joining the iliac crests (Waters and Morris, 1972) at the level of the lamina of L4 (Saunders et al., 2004, Saunders et al., 2005, Thorstensson et al., 1982) or L5 (Waters and Morris, 1972). Thorstensson et al. (1982) placed them just laterally, Waters and Morris (1972) 1cm laterally and Saunders et al. (2004) 4cm laterally to the spinous processes.

4.4.3. Musculus latissimus dorsi 

The surface electrode location for the LD was described as over the muscle belly (Cappellini et al., 2006, Ivanenko et al., 2004, Ivanenko et al., 2006, Ivanenko et al., 2005), more precisely, over the muscular curve at the T12 level and along a line connecting the most posterior point of the posterior axillary fold and the S2 spinous process, with an inter-electrode distance of 1cm (De Seze et al., 2008, De Seze and Cazalets, 2008).

4.4.4. Musculus trapezius 

For the TRAP, the electrodes were placed over the muscle belly (Cappellini et al., 2006, De Seze et al., 2008, De Seze and Cazalets, 2008, Ivanenko et al., 2004, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005), on the inferior and superior portions (Cappellini et al., 2006, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005) with an inter-electrode distance of 1cm (De Seze et al., 2008, De Seze and Cazalets, 2008).

4.4.5. Musculus quadratus lumborum 

Only Waters and Morris (1972) described a location for placing fine-wire electrodes on the QL: 2cm separated, 1 and 2cm above and respectively 1 and 2cm lateral to the posterior superior iliac spine (Waters and Morris, 1972).

4.4.6. Musculus rectus abdominus 

The placement of the electrodes for recording the RA varied with some researchers locating the electrodes on the level of the umbilicus, 2cm (Cromwell et al., 1989, Cromwell et al., 2001), 3cm (Cappellini et al., 2006, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005, Olson, 2010) or 4cm laterally (Anders et al., 2007) to the umbilicus. Others lowered the location to the level of the anterior superior iliac spines, 2cm laterally (Saunders et al., 2004, Saunders et al., 2005, White and Mcnair, 2002) to the midline. Van der Hulst et al. (2010) described the location above the umbilicus, 3cm laterally to the midline, midway between the processus xyphoideus and umbilicus (Van Der Hulst et al., 2010). The inter-electrode distance for the RA was 1cm (White and Mcnair, 2002), 1.2cm (Saunders et al., 2005), 2cm (Masumoto et al., 2004), 2.1cm (Cromwell et al., 2001), 2.5cm (Anders et al., 2009, Anders et al., 2007, Olson, 2010) or 3cm (Li and Hong, 2007), placed over the muscle belly (Cappellini et al., 2006, Ivanenko et al., 2004, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005). The orientation was described as parallel with the direction of the fibers (Cromwell et al., 1989, Masumoto et al., 2004, Olson, 2010, Saunders et al., 2005, White and Mcnair, 2002).

Waters and Morris (1972) described the locations for the 2 fine-wire electrodes 2cm apart, the first 1cm laterally to the linea alba (in center of muscle segment) and the other 2cm superior to the umbilicus (Waters and Morris, 1972).

4.4.7. Musculus obliquus externus 

The surface electrodes were placed just below the rib cage at the inferior angle of the rib (Anders et al., 2007, White and Mcnair, 2002), on a line to the opposite pubic tubercle (Anders et al., 2007, Barton et al., 2009) or lower, midway between the last costal rib and the iliac crest at the level of the umbilicus (Olson, 2010) or even lower just above the iliac crest and 3cm superior to the anterior superior iliac spines (Cromwell et al., 1989) or in the lower 1/3 part between the anterior superior iliac spines and the distal border of the rib cage (Van Der Hulst et al., 2010). The inter-electrode distance for the OE was between 1 (White and Mcnair, 2002) and 2,5cm (Anders et al., 2009, Anders et al., 2007, Olson, 2010) with the electrodes placed parallel with the fiber orientation (Cromwell et al., 1989, Olson, 2010, White and Mcnair, 2002) over the muscle belly (Cappellini et al., 2006, Ivanenko et al., 2004, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005).

The fine-wire electrodes were placed 2cm apart and 2cm along the lower costal margin between the anterior axillary and mid-clavicular lines (Waters and Morris, 1972) or on the midway between the anterior superior iliac spine and the distal border of the rib cage (Saunders et al., 2004, Saunders et al., 2005).

4.4.8. Musculus obliquus internus 

The surface electrodes were placed 1cm (Barton et al., 2009) or 2cm (White and Mcnair, 2002) inferiorly and medially to the anterior superior iliac spine on a line joining both anterior superior iliac spines (Anders et al., 2009, Barton et al., 2009, White and Mcnair, 2002), medial from the inguinal ligament (Anders et al., 2007, White and Mcnair, 2002), but lateral to the lateral border of the rectus sheath (White and Mcnair, 2002). The site of placement of the surface electrodes for the OI was, with an inter-electrode distance between 1cm (White and Mcnair, 2002) and 2.5cm (Anders et al., 2009, Anders et al., 2007), parallel to the direction of the fibers (White and Mcnair, 2002) over the muscle belly (Cappellini et al., 2006, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005).

Regarding the fine-wire electrodes, Waters and Morris (1972) reported that they placed the two electrodes 2cm apart; one 3cm above and perpendicular to the inguinal ligament and one 4cm medial to the anterior superior iliac spine (Waters and Morris, 1972). Saunders et al., 2004, Saunders et al., 2005 described that the fine-wire electrodes were placed on the midway between the anterior superior iliac spine and the distal border of the rib cage.

4.4.9. Musculus transversus abdominus 

The two studies in which TA was evaluated described the placement site of the fine-wire electrodes midway between the anterior superior iliac spine and the distal border of the rib cage (Saunders et al., 2004, Saunders et al., 2005).

4.4.10. Musculus iliopsoas 

The only information about the electrode placement of the ILIO found in the investigated articles was a simple indication of the placement of the surface electrodes over the muscle belly (Cappellini et al., 2006, Ivanenko et al., 2006, Ivanenko et al., 2008, Ivanenko et al., 2005).

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5. Discussion 

This review presents an overview of data found in the literature covering the use of EMG to evaluate the trunk muscles during gait analysis in healthy subjects. Different topics like muscle selection, the application of surface or fine-wire electrodes and the electrode locations were reported.

All the included studies measured one or more trunk muscles during walking in healthy subjects, but there was a large variation in protocols and aims of the studies (Table 2). Because of this reason the EMG data reported in the individual studies were not comparable. For instance in a few papers differences in EMG data between walking with different kind of shoes, between patients and healthy subjects, between walking and performing different tasks or between different velocities of walking were reported. It is possible that the EMG data obtained during gait are insensitive to minor variations in electrode placement, but it is not possible to compare the results of the included studies due to the variation in protocols and objectives of the studies.

5.1. Trunk muscles 

The most frequently measured trunk muscles were the ES, RA, OE and OI. The MF, LD, TRAP, ILIO, TA and QL were measured only in some studies. A majority of the studies focused on the EMG activity of the lower limb muscles including one or two back or abdominal muscles, mainly the ES or the RA. Only a few studies specifically assessed the trunk muscles. In our opinion, the choice of the recruited trunk muscles was determined in most studies by the anatomical position of the trunk muscle in relation to the applicability of the surface electrodes. Likely, the capabilities of the available equipment, such as the number of channels for measuring the EMG, play an important role in the number of muscles selected for measurement.

5.2. Surface electrodes and fine-wire electrodes 

In the 33 selected studies, back and/or abdominal muscles were generally measured using surface EMG and occasionally by means of fine-wire electrodes. The LD, TRAP and ILIO were exclusively measured with surface electrodes while the QL and the TA were exclusively measured with fine-wire electrodes.

We can distinguish different types of electrodes such as: surface and fine-wire electrodes, and a further classification of surface electrodes can be made into: dry and wet electrodes. Wet electrodes are currently preferred for surface EMG applications. The Ag–AgCl electrode is highly stable and the junction with gel exhibits a lower noise level with respect to other metallic electrodes (Merletti et al., 2009). If reported, in almost all studies using surface electrodes, bi- or tripolar Ag–AgCl wet surface electrodes were applied. In some studies no information was given about the materials and sizes of the surface electrodes. Different authors discussed the problem of the ‘optimal’ types of electrodes (surface or fine-wire), for measuring superficial or deeper layer muscles in different situations (for example static or dynamic tests), but there is no consistent conclusion in the literature (Benhamou et al., 1995, Chapman et al., 2010, Giroux and Lamontagne, 1990, Kadaba et al., 1985, Merletti and Farina, 2009). The inconsistency relates to the reproducibility and the reliability is higher for surface electrodes compared to intramuscular wire electrodes (Giroux and Lamontagne, 1990, Kadaba et al., 1985), specifically in measurements of the activity of superficial muscles (Giroux and Lamontagne, 1990). However, there is no consistent correlation between surface and fine-wire electrode EMG values for the same muscle (Jaggi et al., 2009, Kadaba et al., 1985, Perry et al., 1981). The global patterns of muscle recruitment are generally consistent if measured with surface or intramuscular electrodes, but surface EMG recordings can be characterized by additional myoelectric content or “crosstalk” (Chapman et al., 2010). A surface electrode cannot relate to a single muscle if others are in close proximity, but represent in that case muscle group activity (Perry et al., 1981). When surface electrodes were placed over the MF, they were more sensitive to the activity in the adjacent longissimus than to activity in the underlying muscles (Chapman et al., 2010). Stokes et al. (2003) concluded that accurate measurement of the MF requires intra-muscular electrodes instead of surface electrodes to reduce the signal contamination from adjacent muscles significantly (Stokes et al., 2003). It is likely that the co-activation of multiple dorsal trunk muscles, in combination with ‘crosstalk’ between signals from adjacent muscles leads to a misleading impression that surface electrodes are sensitive to activity of deep muscles (Chapman et al., 2010). The insertion of electrodes into muscles (fine-wire EMG) allows the detection of electric potentials close to the muscle fibers, limiting the effect of the volume conductor (Merletti and Farina, 2009). It is clear that one disadvantage of surface EMG is that it is not always possible to measure individual muscles. On the other hand a disadvantage of fine-wire EMG is that it can sample from only a small number of motor units and consequently does not represent the whole muscle (Benhamou et al., 1995). Merletti et al. (2009) reviewed the literature about the technology and instrumentation for detection and conditioning of the surface EMG signal. They reported that a typical limitation of surface EMG recording techniques is represented by the lack of spatial selectivity. A poor spatial selectivity is the indetermination of sources that are closely located in the muscle or deep into it, and this limits the extraction of information to global muscle activity. Conversely, spatial filter design enhances the spatial selectivity of surface recordings by limiting the detection volume and making individual sources more separable (Merletti et al., 2009). The signal energy in surface EMG will be dominated by activity in motor units that have muscle fibers located within 10–12mm of the recording electrode (Fuglevand et al., 1992). It also seems that recording from a muscle lying below another one, even when it is only slightly active, will present great difficulties (Lynn et al., 1978).

Furthermore, there are the artifacts created by skin motion during dynamic evaluations, especially in movements with a great range of motion. Muscle movement introduces additional factors of variability in surface EMG that complicate detection and interpretation of the signals such as shortening of the muscle fibers with the consequent relative shift between muscle fibers and detection system (Merletti et al., 2010a). According Benhamou et al. (1995) and Stokes et al. (2003), these artifacts can be avoided by the use of fine-wire electrodes that are flexible and move with the muscle (Benhamou et al., 1995, Stokes et al., 2003). During walking, the trunk moves in a dynamic manner, but the extent of the movements is limited. Hence the problem of moving of the electrodes over the skin is restricted.

No studies were found that measured the trunk muscle activity with surface and fine-wire electrodes during the same walking protocol, whether or not at the same time. But, when subjects were asked to perform a wide variety of flexor tasks, extensor tasks, lateral bending tasks, twisting tasks and internal/external hip rotation during measurements of the ILIO, QL, OE, OI and TA with surface and intramuscular electrodes, the results indicated that selected surface electrodes adequately represent the amplitude of deep muscles. This always within 15% root mean square differences or less, with the exception of ILIO where differences of up to 20% were observed, but only in certain maximum voluntary contraction efforts (Mcgill et al., 1996).

Although surface electrodes are easier, faster and cheaper to work with, it has not yet been proven that they give invalid results in comparison with the other type of electrodes. Hence, it is understandable that most studies in this review used surface electrodes. As could be expected superficial flat muscles, such as the LD, TRAP and RA, were exclusively or almost exclusively measured with surface electrodes and deeper muscles, such as the MF, OE, OI, QL and TA were almost exclusively measured with fine-wire electrodes.

5.3. Electrodes location site 

In this review, a large variation of different application sites were described for the trunk muscles. A relevant question is to what extend the different formulations of the electrode localizations lead to identical positions taking into account the anthropometric characteristics of the subjects. Moreover, in the various studies it is impossible to determine the applied electrode locations because not enough information is given. Example for the ES, Carlson et al. (1988) described the location “at the level of the L3 vertebra”, but there is no specification about the lateral distance to the spine (Carlson et al. (1988) and Merkle et al. (1998) reported the location as “over the muscle belly” (Merkle et al., 1998).

Sommerich et al. (2000) described two approaches in locating surface electrodes: muscle-specific sites and location-specific sites (Sommerich et al., 2000). In this study a description for the RA like “over the muscle belly, middle and superior portions” (Ivanenko et al., 2004) can be an example of the muscle-specific sites and “3cm lateral to midline, midway between the processus xyphoideus and umbilicus” (Van Der Hulst et al., 2010) can be an example of the location-specific sites. Most of the descriptions in the studies were location-specific or a combination of both methods. Sommerich et al. (2000) indicate that location-specific sites may be appropriate when interest is in levels of activity in a muscle group, but crosstalk from adjacent muscles is more likely than in muscle-specific location (Sommerich et al., 2000).

The localization of the electrode placement is difficult for the back and abdominal muscles because of their multilayer structure and their mostly flat presence. A cadaver study to determine the best electrode location for the back muscles on an anatomical base, in order to avoid cross-talking during measurement was done. In this way more precise locations of electrode placement sites for surface electrodes were defined (De Seze and Cazalets, 2008). Beside cadaver studies, in vivo studies were done to determine the best electrode locations. De Nooij et al. (2009) evaluated the influence of electrode location on surface EMG amplitude of the ES pars longissimus dorsi by placing additional electrodes on 16 healthy subjects during five different tasks (standing, forward flexion, re-extension, unsupported sitting and arm/leg lifting). Two electrodes were located according to the SENIAM guidelines for electrode positions and substantial cranial, caudal and lateral electrode dislocations were simulated by placing four additional electrodes. They concluded that lateral dislocation results in an average decrease of 18% in surface EMG amplitude, that caudal and cranial dislocation does not cause a change in surface EMG amplitude and that the variability caused by electrode dislocation is comparable to the variability caused by repetitions of tasks or by electrode repositioning (De Nooij et al., 2009). The studies in our review reported the electrode placement for the ES on a distance from 2 to 9cm lateral from the spine, what in accordance to the study of De Nooij et al. (2009) would give changes in SEMG amplitude. We did not find any in vivo tests, where different types of electrodes were placed on different locations of the trunk during walking in healthy subjects. Such an experimental setup could be interesting to define specific recommendations and guidelines for electrode application of the trunk muscles.

5.4. Inter-electrode distance 

The inter-electrode distance is the center-to-center distance between the conductive areas of the electrodes (Seniam, 2010). Changes in inter-electrode distance between 2 and 4cm (over the innervations zone) and 4cm (distal of the innervations zone) for the vastus lateralis (Beck et al., 2009), and 2, 4 or 6cm for the biceps brachii muscles (Beck et al., 2005) did not influence normalized EMG data. A test based on computer simulations and experimental data concluded that when a single electrode pair is used, the inter-electrode distance must be small with respect to the distance between the innervation zone and the tendon, and neither electrode of the pair should be over the innervation zone for the entire range of the movement, otherwise they may be highly affected by small geometrical changes (Mesin et al., 2009). When the inter-electrode distance is shorter than 5mm there is a practical limit associated with a greater risk that the electrolyte gel will form a salt bridge between the two recording surfaces across the skin. This will reduce the potential difference between the two electrodes, and the observed EMG amplitude will be much lower than expected (Kamen and Gabriel, 2010). When reported, the inter-electrode distance varied in the different studies of this review from 1 to 3cm, which are only small differences taking into account the size of the electrodes in the studies (conductive area of the electrodes: r=3–7.5mm) (Table 2).

Different modalities of skin preparation were reported in the selected studies. Proper skin preparation is necessary to reduce the electrode-gel-skin impedance and the imbalance between the impedance of two electrodes. Different preparations may lead to different impedance values, and the degree of impedance reduction due to skin treatment is not consistent in different individuals and for different experiments (Merletti et al., 2010b).

In this review only studies on healthy subjects were described during walking. Apart from these studies, trunk muscle activity is also measured in some patient populations for instance with low back pain or neurological disorders, and during other motor tasks, like force tests or lifting exercises (Mcgill et al., 1996, Van Dieen et al., 2003). An overview of all the studies measuring trunk EMG during all the different motor tasks would be interesting, but is beyond the scope of this review.

We conclude that: (1) the most frequently measured trunk muscles during gait were the ES, RA, OI and OE, (2) surface electrodes were used more frequently than fine-wire electrodes and (3) the descriptions of the electrode locations were mostly vague and not consistent among the different studies. We can conclude that at present no consistent information is available in the literature in order to give specific recommendations for optimal localization of EMG electrodes. There is a need for further research to make specific recommendations about the type of electrodes in combination with the optimal locations of application.

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Acknowledgements 

Thanks to Drs. Ph. Van der Veen and L. Denuelin for helping with the redaction of this paper.

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References 

  1. Anders C, Wagner H, Puta C, Grassme R, Scholle HC. Healthy humans use sex-specific co-ordination patterns of trunk muscles during gait. Eur J Appl Physiol. 2009;105(4):585–594
  2. Anders C, Wagner H, Puta C, Grassme R, Petrovitch A, Scholle H-C. Trunk muscle activation patterns during walking at different speeds. J Electromyogr Kinesiol. 2007;17(2):245–252
  3. Armijo-Olivo S, Gadotti I, Kornerup M, Lagravere MO, Flores-Mir C. Quality of reporting masticatory muscle electromyography in 2004: a systematic review. J Oral Rehabil. 2007;34(6):397–405
  4. Barton CJ, Coyle JA, Tinley P. The effect of heel lifts on trunk muscle activation during gait: a study of young healthy females. J Electromyogr Kinesiol. 2009;19(4):598–606
  5. Beck TW, Housh TJ, Cramer JT, Weir JP. The effects of interelectrode distance over the innervation zone and normalization on the electromyographic amplitude and mean power frequency versus concentric, eccentric, and isometric torque relationships for the vastus lateralis muscle. J Electromyogr Kinesiol. 2009;19(2):219–231
  6. Beck TW, Housh TJ, Johnson GO, Weir JP, Cramer JT, Coburn JW, et al. The effects of interelectrode distance on electromyographic amplitude and mean power frequency during isokinetic and isometric muscle actions of the biceps brachii. J Electromyogr Kinesiol. 2005;15(5):482–495
  7. Benhamou MA, Revel M, Vallee C. Surface electrodes are not appropriate to record selective myoelectric activity of splenius capitis muscle in humans. Exp Brain Res. 1995;105(3):432–438
  8. Campanini I, Merlo A, Degola P, Merletti R, Vezzosi G, Farina D. Effect of electrode location on emg signal envelope in leg muscles during gait. J Electromyogr Kinesiol. 2007;17(4):515–526
  9. Capaday C. The special nature of human walking and its neural control. Trends Neurosci. 2002;25(7):370–376
  10. Cappellini G, Ivanenko YP, Poppele RE, Lacquaniti F. Motor patterns in human walking and running. J Neurophysiol. 2006;95(6):3426–3437
  11. Carda S, Cisari C, Invernizzi M, Bevilacqua M. Osteoporosis after stroke: a review of the causes and potential treatments. Cerebrovasc Dis. 2009;28(2):191–200
  12. Carlson H, Thorstensson A, Nilsson J. Lumbar back muscle activity during locomotion: effects of voluntary modifications of normal trunk movements. Acta Physiol Scand. 1988;133(3):343–353
  13. Castroflorio T, Icardi K, Torsello F, Deregibus A, Debernardi C, Bracco P. Reproducibility of surface emg in the human masseter and anterior temporalis muscle areas. Cranio. 2005;23(2):130–137
  14. Cbo (kwaliteitsinstituut voor de gezondheidszorg), 2010. http://www.cbo.nl/.
  15. Ceccato J-C, De Seze M, Azevedo C, Cazalets J-R. Comparison of trunk activity during gait initiation and walking in humans. PLoS One. 2009;4(12):e8193
  16. Chapman AR, Vicenzino B, Blanch P, Knox JJ, Hodges PW. Intramuscular fine-wire electromyography during cycling: repeatability, normalisation and a comparison to surface electromyography. J Electromyogr Kinesiol. 2010;20(1):108–117
  17. Cote J, Mathieu PA. Mapping of the human upper arm muscle activity with an electrode matrix. Electromyogr Clin Neurophysiol. 2000;40(4):215–223
  18. Cromwell R, Schultz AB, Beck R, Warwick D. Loads on the lumbar trunk during level walking. J Orthop Res. 1989;7(3):371–377
  19. Cromwell RL, Aadland-Monahan TK, Nelson AT, Stern-Sylvestre SM, Seder B. Sagittal plane analysis of head, neck, and trunk kinematics and electromyographic activity during locomotion. J Orthop Sports Phys Ther. 2001;31(5):255–262
  20. De Nooij R, Kallenberg LaC, Hermens HJ. Evaluating the effect of electrode location on surface emg amplitude of the m. Erector spinae p. Longissimus dorsi. J Electromyogr Kinesiol. 2009;19(4):e257–e266
  21. De Seze M, Falgairolle M, Viel S, Assaiante C, Cazalets J-R. Sequential activation of axial muscles during different forms of rhythmic behavior in man. Exp Brain Res. 2008;185(2):237–247
  22. De Seze MP, Cazalets J-R. Anatomical optimization of skin electrode placement to record electromyographic activity of erector spinae muscles. Surg Radiol Anat. 2008;30(2):137–143
  23. Dietz V. Body weight supported gait training: from laboratory to clinical setting. Brain Res Bull. 2008;76(5):459–463
  24. Dofferhof AS, Vink P. The stabilising function of the mm. Iliocostales and the mm. Multifidi during walking. J Anat. 1985;140:329–336[Pt 2]
  25. Falla D, Dall’alba P, Rainoldi A, Merletti R, Jull G. Repeatability of surface emg variables in the sternocleidomastoid and anterior scalene muscles. Eur J Appl Physiol. 2002;87(6):542–549
  26. Finch L, Barbeau H, Arsenault B. Influence of body weight support on normal human gait: development of a gait retraining strategy. Phys Ther. 1991;71(11):842–855[discussion 855]
  27. Frigo C, Crenna P. Multichannel semg in clinical gait analysis: a review and state-of-the-art. Clin Biomech (Bristol, Avon). 2009;24(3):236–245
  28. Fuglevand AJ, Winter DA, Patla AE, Stashuk D. Detection of motor unit action potentials with surface electrodes: influence of electrode size and spacing. Biol Cybern. 1992;67(2):143–153
  29. Giroux B, Lamontagne M. Comparisons between surface electrodes and intramuscular wire electrodes in isometric and dynamic conditions. Electromyogr Clin Neurophysiol. 1990;30(7):397–405
  30. Globas C, Macko RF, Luft AR. Role of walking-exercise therapy after stroke. Expert Rev Cardiovasc Ther. 2009;7(8):905–910
  31. Grabiner MD, Donovan S, Bareither ML, Marone JR, Hamstra-Wright K, Gatts S, et al. Trunk kinematics and fall risk of older adults: translating biomechanical results to the clinic. J Electromyogr Kinesiol. 2008;18(2):197–204
  32. Hermens HJ, Frederiks B, Merletti R, Stegeman D, Blok J, Rau G, et al. European recommendation for surface electromyography. 2nd edition. Roessingh Research and Development bv; 1999;
  33. Hogrel JY, Duchene J, Marini JF. Variability of some semg parameter estimates with electrode location. J Electromyogr Kinesiol. 1998;8(5):305–315
  34. Ivanenko YP, Poppele RE, Lacquaniti F. Five basic muscle activation patterns account for muscle activity during human locomotion. J Physiol. 2004;556(Pt 1):267–282
  35. Ivanenko YP, Poppele RE, Lacquaniti F. Spinal cord maps of spatiotemporal alpha-motoneuron activation in humans walking at different speeds. J Neurophysiol. 2006;95(2):602–618
  36. Ivanenko YP, Cappellini G, Poppele RE, Lacquaniti F. Spatiotemporal organization of alpha-motoneuron activity in the human spinal cord during different gaits and gait transitions. Eur J Neurosci. 2008;27(12):3351–3368
  37. Ivanenko YP, Cappellini G, Dominici N, Poppele RE, Lacquaniti F. Coordination of locomotion with voluntary movements in humans. J Neurosci. 2005;25(31):7238–7253
  38. Jackson AB, Carnel CT, Ditunno JF, Read MS, Boninger ML, Schmeler MR, et al. Outcome measures for gait and ambulation in the spinal cord injury population. J Spinal Cord Med. 2008;31(5):487–499
  39. Jaggi A, Malone AA, Cowan J, Lambert S, Bayley I, Cairns MC. Prospective blinded comparison of surface versus wire electromyographic analysis of muscle recruitment in shoulder instability. Physiother Res Int. 2009;14(1):17–29
  40. Kadaba MP, Wootten ME, Gainey J, Cochran GV. Repeatability of phasic muscle activity: performance of surface and intramuscular wire electrodes in gait analysis. J Orthop Res. 1985;3(3):350–359
  41. Kamen G, Gabriel D, Essentials of electromyography . Human Kinetics. 2010;ISBN:13:9780736067126
  42. Kelleher KJ, Spence W, Solomonidis S, Apatsidis D. Ambulatory rehabilitation in multiple sclerosis. Disabil Rehabil. 2009;31(20):1625–1632
  43. Kendall FP, Mccreary EK, Provance PG, Rodgers MM, Romani WA. Muscles testing and function with posture and pain. 5th edition. Lippincott Williams & Wilkins; 2005;
  44. Lamoth CJC, Daffertshofer A, Meijer OG, Beek PJ. How do persons with chronic low back pain speed up and slow down? Trunk-pelvis coordination and lumbar erector spinae activity during gait. Gait Posture. 2006;23(2):230–239
  45. Lamoth CJC, Meijer OG, Daffertshofer A, Wuisman PIJM, Beek PJ. Effects of chronic low back pain on trunk coordination and back muscle activity during walking: changes in motor control. Eur Spine J. 2006;15(1):23–40
  46. Li JX, Hong Y. Kinematic and electromyographic analysis of the trunk and lower limbs during walking in negative-heeled shoes. J Am Podiatr Med Assoc. 2007;97(6):447–456
  47. Li W, Sakamoto K. The influence of location of electrode on muscle fiber conduction velocity and emg power spectrum during voluntary isometric contraction measured with surface array electrodes. Appl Human Sci. 1996;15(1):25–32
  48. Lynn PA, Bettles ND, Hughes AD, Johnson SW. Influences of electrode geometry on bipolar recordings of the surface electromyogram. Med Biol Eng Comput. 1978;16(6):651–660
  49. Martin S, Macisaac D. Innervation zone shift with changes in joint angle in the brachial biceps. J Electromyogr Kinesiol. 2006;16(2):144–148
  50. Masumoto K, Takasugi S-I, Hotta N, Fujishima K, Iwamoto Y. Electromyographic analysis of walking in water in healthy humans. J Physiol Anthropol Appl Human Sci. 2004;23(4):119–127
  51. Mcgill S, Juker D, Kropf P. Appropriately placed surface emg electrodes reflect deep muscle activity (psoas, quadratus lumborum, abdominal wall) in the lumbar spine. J Biomech. 1996;29(11):1503–1507
  52. Mcgill SM, Grenier S, Kavcic N, Cholewicki J. Coordination of muscle activity to assure stability of the lumbar spine. J Electromyogr Kinesiol. 2003;13(4):353–359
  53. Mcginley JL, Baker R, Wolfe R, Morris ME. The reliability of three-dimensional kinematic gait measurements: a systematic review. Gait Posture. 2009;29(3):360–369
  54. Mercer JA, Bezodis N, Delion D, Zachry T, Rubley MD. Emg sensor location: does it influence the ability to detect differences in muscle contraction conditions?. J Electromyogr Kinesiol. 2006;16(2):198–204
  55. Merkle LA, Layne CS, Bloomberg JJ, Zhang JJ. Using factor analysis to identify neuromuscular synergies during treadmill walking. J Neurosci Methods. 1998;82(2):207–214
  56. Merletti R, Farina D. Analysis of intramuscular electromyogram signals. Philos Transact A Math Phys Eng Sci. 2009;367(1887):357–368
  57. Merletti R, Botter A, Troiano A, Merlo E, Minetto MA. Technology and instrumentation for detection and conditioning of the surface electromyographic signal: state of the art. Clin Biomech (Bristol, Avon). 2009;24(2):122–134
  58. Merletti R, Botter A, Cescon C, Minetto MA, Vieira TM. Advances in surface emg: recent progress in clinical research applications. Crit Rev Biomed Eng. 2010;38(4):347–379
  59. Merletti R, Aventaggiato M, Botter A, Holobar A, Marateb H, Vieira TM. Advances in surface emg: recent progress in detection and processing techniques. Crit Rev Biomed Eng. 2010;38(4):305–345
  60. Mesin L, Merletti R, Rainoldi A. Surface emg: the issue of electrode location. J Electromyogr Kinesiol. 2009;19(5):719–726
  61. Olson MW. Trunk extensor fatigue influences trunk muscle activities during walking gait. J Electromyogr Kinesiol. 2010;20(1):17–24
  62. Perry J, Easterday CS, Antonelli DJ. Surface versus intramuscular electrodes for electromyography of superficial and deep muscles. Phys Ther. 1981;61(1):7–15
  63. Prentice SD, Patla AE, Stacey DA. Artificial neural network model for the generation of muscle activation patterns for human locomotion. J Electromyogr Kinesiol. 2001;11(1):19–30
  64. Roy SH, De Luca CJ, Schneider J. Effects of electrode location on myoelectric conduction velocity and median frequency estimates. J Appl Physiol. 1986;61(4):1510–1517
  65. Saunders SW, Rath D, Hodges PW. Postural and respiratory activation of the trunk muscles changes with mode and speed of locomotion. Gait Posture. 2004;20(3):280–290
  66. Saunders SW, Schache A, Rath D, Hodges PW. Changes in three dimensional lumbo-pelvic kinematics and trunk muscle activity with speed and mode of locomotion. Clin Biomech (Bristol, Avon). 2005;20(8):784–793
  67. Schulte E, Farina D, Merletti R, Rau G, Disselhorst-Klug C. Influence of muscle fibre shortening on estimates of conduction velocity and spectral frequencies from surface electromyographic signals. Med Biol Eng Comput. 2004;42(4):477–486
  68. Seniam, (SENIAM, Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles) 2010. http://www.seniam.org.
  69. Shung K, De Oliveira CG, Nadal J. Influence of shock waves and muscle activity at initial contact on walk-run transition evaluated by two models. J Appl Biomech. 2009;25(2):175–183
  70. Sommerich CM, Joines SM, Hermans V, Moon SD. Use of surface electromyography to estimate neck muscle activity. J Electromyogr Kinesiol. 2000;10(6):377–398
  71. Stokes IaF, Henry SM, Single RM. Surface emg electrodes do not accurately record from lumbar multifidus muscles. Clin Biomech (Bristol, Avon). 2003;18(1):9–13
  72. Thorstensson A, Carlson H, Zomlefer MR, Nilsson J. Lumbar back muscle activity in relation to trunk movements during locomotion in man. Acta Physiol Scand. 1982;116(1):13–20
  73. Van Der Hulst M, Vollenbroek-Hutten MM, Rietman JS, Hermens HJ. Lumbar and abdominal muscle activity during walking in subjects with chronic low back pain: support of the “guarding” hypothesis?. J Electromyogr Kinesiol. 2010;20(1):31–38
  74. Van Dieen JH, Selen LPJ, Cholewicki J. Trunk muscle activation in low-back pain patients, an analysis of the literature. J Electromyogr Kinesiol. 2003;13(4):333–351
  75. Vink P, Karssemeijer N. Low back muscle activity and pelvic rotation during walking. Anat Embryol (Berl). 1988;178(5):455–460
  76. Vogt L, Banze W. Vergeleichende oberflächen-elektromyographische untersuchung ausgewählter rumph-und hüftmuskeln beim gehen auf der freien gehstrecke und dem laufbandergometer. Free level versus treadmill ambulation; an electromyographic study of lumbar spine and hip muscles. Deutsche Zetischrift für Sportmedizin. 1999;50(3):84–88
  77. Vogt L, Pfeifer K, Banzer W. Neuromuscular control of walking with chronic low-back pain. Man Ther. 2003;8(1):21–28
  78. Waters RL, Morris JM. Electrical activity of muscles of the trunk during walking. J Anat. 1972;111(Pt 2):191–199
  79. White SG, Mcnair PJ. Abdominal and erector spinae muscle activity during gait: the use of cluster analysis to identify patterns of activity. Clin Biomech (Bristol, Avon). 2002;17(3):177–184
biography

Eva Swinnen obtained her Diploma of Master in the Rehabilitation Sciences and Physiotherapy at the Vrije Universiteit Brussel in 2005. After her graduation she worked as a physiotherapist in a private practice and in a rehabilitation centre. From 2006 until 2008 she worked as an academic assistant at the physiotherapy department of the faculty of Physical Education and Physiotherapy at the Vrije Universiteit Brussel. On January 1, 2009 she started her Ph.D. project as part of the ALTACRO (Automated Locomotion Training using an Actuated Compliant Robotic Orthosis) project. Her work is situated in the domain of neurological rehabilitation and biomechanics.

biography

Jean-Pierre Baeyens has a Ph.D. in Rehabilitation Sciences and Physical Therapy and master degrees in Biomedical Engineering, Manual Therapy and Art History. He is head of the laboratory of Biomechanics of the Vrije Universiteit Brussel. His biomechanics research interest focuses primarily in motor learning and RSI in musicians, handball throwing, and intra articular kinematics of shoulder and elbow.

biography

Romain Meeusen, (Ph.D.) is head of the department of Human Physiology and director of the Human Performance lab at the Vrije Universiteit Brussel. His research interest is focussed on “Exercise and the Brain” exploring the influence of neurotransmitters on human performance and training. Recent work is focussing on thermoregulation, Overtraining Syndrome and Neurogenesis. He teaches on exercise physiology, training and coaching and sports physiotherapy. He is President of the Belgian Federation of Sports Physiotherapy, Board member of the European College of Sport Science (ECSS) and Board member of the American College of Sports Medicine (ACSM).

biography

Eric Kerckhofs received his Ph.D. in Rehabilitation Sciences and Physical Therapy and Master degree in Clinical Psychology at the Vrije Universiteit Brussel (Belgium). He is affiliated as a professor in neurological rehabilitation and rehabilitation psychology to that same university since 2001. His research is situated in the domain of neurological rehabilitation of patients with stroke, Parkinson’s disease or multiple sclerosis.

PII: S1050-6411(11)00059-9

doi:10.1016/j.jelekin.2011.04.005

Journal of Electromyography and Kinesiology
Volume 22, Issue 1 , Pages 1-12, February 2012

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