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Relationship betweenlimb movement speed andassociated contraction ofthe trunk musclesPAUL W. HODGES & CAROLYN A. RICHARDSONPublished online: 10 Nov 2010.

To cite this article: PAUL W. HODGES & CAROLYN A. RICHARDSON (1997)Relationship between limb movement speed and associated contraction of thetrunk muscles, Ergonomics, 40:11, 1220-1230, DOI: 10.1080/001401397187469

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Relationship between limb movement speed and associated

contraction of the trunk muscles

PAUL W. HODGES and CAROLYN A. RICHARDSON

Department of Physiotherapy, The University of Queensland 4072, Australia

Keywords: Lumbar spine; Abdominal muscles; Posture; Movement; Acceleration.

Rapid shoulder movement is preceded by contraction of the abdominal musclesto prepare the body for the expected disturbance to postural equilibrium andspinal stability provoked by the reactive forces resulting from the movement. Themagnitude of the reactive forces is proportional to the inertia of the limb. The aimof the study was to investigate if changes in the reaction time latency of theabdominal muscles was associated with variation in the magnitude of the reactiveforces resulting from variation in limb speed. Fifteen participants performedshoulder ¯ exion at three diŒerent speeds (fast, natural and slow). The onset ofEMG of the abdominal muscles, erector spinae and anterior deltoid (AD) wasrecorded using a combination of ® ne-wire and surface electrodes. Mean and peakvelocity was recorded for each limb movement speed for ® ve participants. Theonset of transversus abdominis (TrA) EMG preceded the onset of AD in only thefast movement condition. No signi® cant diŒerence in reaction time latency wasrecorded between the fast and natural speed conditions for all muscles. Thereaction time of each of the abdominal muscles relative to AD was signi® cantlydelayed with the slow movement compared to the other two speeds. The resultsindicate that the reaction time latency of the trunk muscles is in¯ uenced by limbinertia only with limb movement below a threshold velocity.

1. Introduction

Rapid movement of the upper limb produces a complex interplay of dynamic forces

acting on the trunk and body, including inertial reactive forces between the

segments, linear centrifugal forces and torsional movements (Aruin and Latash 1995,

Horak et al. 1984). These dynamic reactive forces exerted on the supporting segment

act in an opposite direction to those producing the movement and lead to postural

disturbance (Bouisset and Zattara 1987). This disturbance aŒects both the

relationship of the body to the base of support and the relationship between

adjacent segments (Massion 1992). The in¯ uence of these reactive forces is

particularly signi ® cant for the multisegmented spine since the range of motion

around the neutral position of each segment is unconstrained by the passive

structures and is dependent on muscular control (Panjabi 1992).

Postural responses to counteract the eŒect of the dynamic reactive forces are

initiated prior to the onset of contraction of the muscles responsible for

movement of the limb (Belen’kii et al. 1967, Cordo and Nashner 1982, Lee et al.

Address for correspondence: Paul Hodges, Department of Neuroscience, Karolinska

Institute, Box 5626, S-113 46 Stockholm, Sweden. Tel: + 46 8 402 2242; Fax: + 46 8 402 2287;

E-mail: Paul.Hodges@ neuro.ki.se

ERGONOMICS, 1997, VOL. 40, NO. 11, 1220 ± 1230

0014± 0139/97 $12 × 00 Ó 1997 Taylor & Francis Ltd

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1987). These responses are referred to as `anticipatory ’ postural responses (Aruin

and Latash 1995). Studies evaluating the anticipatory response of the muscles of

the trunk associated with movement of the upper limb indicate contraction of

either the erector spinae (ES) prior to upper limb ¯ exion (Aruin and Latash 1995,

Belen’kii et al. 1967, Friedli et al. 1984, Zattara and Bouisset 1988) or contraction

of the rectus abdominis (RA) preceding upper limb extension (Aruin and Latash

1995, Friedli et al. 1984). Contraction of transversus abdominis (TrA) has been

found to be the ® rst trunk muscle active irrespective of the direction of movement

(Hodges and Richardson 1996, 1997). TrA may contribute to stabilization and

protection of the spine through either its role in the production of intra-

abdominal pressure (Cresswell et al. 1992) or tensioning the thoracolumbar fascia

(Tesh et al. 1987).

The dynamic reactive forces resulting from upper limb movement are equal in

magnitude and opposite in direction to the forces producing the movement (Bouisset

and Zattara 1987). Since the magnitude of the dynamic reactive forces and the

resulting perturbation are dependent on the inertia of the limb (Lee et al. 1987) it

would be expected that the postural response of the trunk muscles would be

temporally scaled to compensate for the changes in limb speed (Gahe ry and

Massion 1981). When comparing fast and slow movements, this relationship has

been identi ® ed for the biceps femoris and ES muscles (Horak et al. 1984). However,

when the reaction time latency of trunk and lower limb muscles was compared over

a wide range of speeds the reaction time of the lower limb postural muscles was

correlated with upper limb accelertion only at speeds greater than 70 ± 90 8 /s (Lee et

al. 1987). With slower movement, there was no relationship between acceleration

and latency and up to 50% of the trials had no postural muscle response. In contrast

to the lower limb postural muscles, the reaction time latency of ES was constant for

faster speeds and was correlated with limb speed for the slow conditions (Lee et al.

1987). Clearly diŒerences exist in the relationship between upper limb movement

speed and reaction time latency for trunk and lower limb postural muscles. Animal

studies have also identi® ed diŒerences in the response of the trunk and lower limb

muscles with movements at diŒerent velocities, suggesting separate control within

the central nervous system (Burbaud et al. 1988). No studies have evaluated the

relationship between abdominal muscle reaction time latency and limb movement

speed.

The aim of the current study was to investigate the in¯ uence of speed of limb

movement on reaction time latency of the trunk muscles. It was hypothesized that

the abdominal muscles would respond in a similar manner to ES and have a constant

reaction time for speeds other than slow movement. A precise understanding of the

normal function of the stabilizing mechanism of the spine with varying demands is

essential for the evaluation of dysfunction and risk of injury in the workplace.

2. Materials and methods

2.1. Participants

The study involved 15 participants (9 males, 6 females) aged 20 × 6 6 2 × 3 years with

height and weight of 1 × 74 6 0 × 09 m and 69 6 11 kg, respectively and of average

activity level. Participant s were excluded if they had a history of low-back pain, gross

postural abnormality or signi® cant neurologica l or respiratory condition. The study

was approved by the Medical Research Ethics Committee of the University of

Queensland.

1221Limb movement speed and trunk muscle contraction

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2.2. Electromyographic recordings

Fine-wire electromyography (EMG) electrodes were inserted into TrA, abdominis

obliquus externus (EO) and abdominis obliquus internus (IO) under the guidance of

real-time ultrasound imaging. This technique has been described in detail elsewhere

(DeTroyer et al. 1990, Hodges and Richardson 1997). The electrodes were inserted at

consistent sites with the TrA electrode placed 2 cm anterior to the intersection of a

line drawn cephalad from the anterior superior iliac spine (ASIS) and the distal

border of the rib cage, the IO electrode was placed 2 cm superior and medial to the

ASIS and the EO electrode was placed midway between the iliac crest and distal

border of the rib cage in the mid-axillary line. The electrode insertions were

performed under the supervision of an experienced medical practitioner.

The activity of RA, ES and anterior deltoid (AD), as the prime mover of

shoulder ¯ exion, was recorded using silver/silver chloride electrodes following

careful skin preparation to reduce the skin impedance to below 5 k X . The electrodes

were placed parallel to the muscle ® bres with an interelectrode distance of 12 mm at

1 cm lateral to the L4-5 interspace for ES, either side of a line drawn between the

right and left ASIS close to the midline in a caudo-medial direction for RA and

centrally over the palpated muscle belly of AD.

The EMG data was recorded using an AMLAB analog workstation (Associative

Measurements, North Ryde, Australia) with 12-bit analogue to digital conversion.

Data was sampled at 2000 Hz and bandpass ® ltered at 20 ± 1000 Hz.

2.3. Kinematic recordings

Limb movement velocity was recorded using a Position-Velocity Transducer

(UniMeasure, Corvalis, USA) which measures both the velocity and distance of

displacement of a cable from the transducer. Owing to the slight resistance provided

by the cable at the initiation of movement and the indication in the literature that

limb loading may in¯ uence the onset of postural muscle activity (Friedli et al. 1984),

the limb velocity evaluation was conducted during a separate trial to the EMG

evaluation . For this study ® ve participants were randomly selected from the initial

participant group. The angular velocity about the approximate centre of rotation of

the glenohumeral joint was calculated using the linear velocity and position data

from the transducer (appendix) . Kinematic data was sampled at 100 Hz and stored

on computer for later analysis .

2.4. Experimental procedure

All movements were performed in the standing position with the feet placed on the

sensors of a force platform (SMS Healthcare, Birmingham, UK), which provided

auditory feedback of the weight-bearing status to ensure that equal weight bearing

was maintained.

Ten repetitions of shoulder ¯ exion were performed in response to a visual

stimulus at each of three diŒerent speeds to approximately 60 8 with the emphasis on

the speed of movement rather than the distance travelled. A warning stimulus

preceded the stimulus to move by a random period of between 0 × 5 ± 4 s. The order of

the speed conditions was randomized. The participant rested in the sitting position

between each set of 10 movements. The limb speeds were similar to those used by

Rogers and Pai (1990) involving fast, natural and slow movement. Limb movement

speed could not be more speci® cally controlled by providing a pacing guide, since

changes in behavioura l constraint in¯ uence the sequence and temporal features of

1222 P. W. Hodges and C. A. Richardson

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the anticipatory postural muscle response (Lee et al. 1987). The speed conditions

involved in the current study were:

(1) Fast Ð movement performed as fast as possible.

(2) Natural Ð movement performed at a speed natural to the participant . This

speed condition was used to identify the temporal parameters of the

anticipatory postural muscle response at a functional speed at a velocity

intermediate between the other two conditions .

(3) Slow Ð movement performed at a speed taking approximately 2 s to

complete the 60 8 of movement (i.e. 30 8 /s). The movement speed was

demonstrated to the participant by the examiner.

For the performance of the limb velocity study, the participant s adopted a similar

starting position to the EMG trial. However, since the device could not account for

displacement of the shoulder, the participant was positioned with the thoracic spine

in contact with a ® xed vertical bar and instructed to maintain contact during the

procedure. In this way only minimal displacement of the axis of the shoulder was

permitted. The cable was attached to the right forearm by a strap placed 0 × 5 m from

the tip of the acromion. Using identical instructions to the EMG trial, each

participant performed ten repetitions at each of the three speeds. The distance from

cable outlet to the centre of rotation of the glenohumeral joint (approximated as the

position of the tip of the acromion process) was measured for the angular velocity

calculation (appendix) .

2.5. Data analysis

The onset of EMG of each of the muscles evaluated formed the basis of the analysis .

The onset time was calculated mathematically by computer using MATLAB

software (The Math Works, Natick, USA) based on an algorithm that identi® ed the

point where the mean EMG amplitude was greater than 2 standard deviations from

the mean background EMG recorded for the 25 ms prior to the warning stimulus

(Hodges and Bui 1997). Both the reaction time and the time of onset of each of the

trunk muscles relative to AD were evaluated. Consistent with previous studies, onset

of trunk muscle activity occurring between 100 ms before to 50 ms after AD were

considered to be anticipatory (Aruin and Latash 1995, Hodges and Richardson

1997).

The calculation of the angular velocity of the limb from the linear velocity and

position was performed using MATLAB software and the formulae outlined in the

appendix. The peak and mean velocity were calculated for each limb movement and

the mean of the ten repetitions was used for analysis.

Comparison of the reaction time (time from movement stimulus to EMG onset),

the latency between the time of onset of EMG activity of each of the trunk muscles

and AD and the mean and peak velocity between limb movement speed conditions

was conducted using a repeated measures ANOVA. The number of trials in which a

response was recorded for each muscle was an additional parameter evaluated.

3. Results

3.1. Variation in sequence of muscle contraction between speeds of movement

With decreasing limb movement speed the reaction time of each muscle, except RA,

was increased (p<0 × 01) (® gure 1) indicating an inverse relationship between the

1223Limb movement speed and trunk muscle contraction

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abdominal muscle reaction time latency and the limb acceleration. However, there

was no signi ® cant diŒerence in the reaction time of any of the muscles between the

natural and fast conditions . The reaction time latency of each of the muscles, except

RA, was signi ® cantly increased in the slow movement condition. It is also notable

that the variability of the reaction time was markedly increased in this condition. In

many of the trials at the slower speeds the EMG magnitude increased slowly rather

than the rapid increase noted for the fast movements making determination of the

onset of EMG more variable . The reaction time of RA failed to follow the same

variation with changes in arm acceleration with no signi ® cant diŒerence reported

between the three conditions . However, with movement at the slow speed this

reaction time is based on only 12 trials of the total 150 recorded due to the

infrequency of contraction of this muscle at this speed.

Although TrA was the only muscle found to be active prior to AD in the fast

limb movement condition, the onset of contraction of ES and IO fell within the

criteria for anticipatory muscle contraction (table 1). TrA failed to be active prior to

AD with movement at natural or slow speeds, however TrA and ES were active

within the anticipatory criteria in the natural speed condition. No trunk muscle

contraction occurred prior to 50 ms after AD with movement at the slow speed due

to the disproportionate increase in reaction time of the trunk muscles compared to

AD. The times of onset of the muscles relative to the AD were not signi® cantly

diŒerent between the fast and natural movement conditions .

3.2. Variation in frequency of contraction between speeds of movement

As the speed of limb movement decreased, the activity of one or more of the

trunk muscles was frequently absent in a number of repetitions. The frequency of

response for each muscle across movement speeds is presented in ® gure 2. With

Figure 1. EMG data of a representative participant for all muscles averaged over tenrepetitions at each of the three movement speeds. The time of alignment of the traces atthe onset of EMG activity of anterior deltoid (AD) is noted by the ® ne dashed line atzero. The onset of TrA is noted by the heavy dashed line. Note the non-signi® cant delayin onset of contraction of each of the trunk muscles between the fast and natural speedconditions and the absence of trunk muscle response with slow movement. EMG is inarbitrary units.

1224 P. W. Hodges and C. A. Richardson

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movement at the slow speed it was uncommon for activity to be recorded in RA

with contraction reported in only 8% of the trials. In contrast, ES was frequently

active at all speeds of movement. Movement at the natural speed varied little

from the fast condition with few trials resulting in inactivity of any of the trunk

muscles. The only exception was RA, which was inactive in 43% of the

repetitions at this speed.

3.3. Kinematic data

The mean and peak velocity data are presented in table 2. The mean velocity for the

slow movement category was approximate ly 10 8 /s faster than the movement

demonstrated to the participant by the examiner. Considering the lenient control of

the limb velocity for the natural and slow conditions the variation between

Figure 2. Frequency of EMG response of each of the trunk muscles with variation in thespeed of limb movement. Note the decreasing frequency of response as the speed of limbmovement is reduced.

Table 1. Variation in the latency between the EMG onset of AD and each of the trunkmuscles between limb speed conditions (mean 6 SD) (negative values indicate contractionof the trunk muscle prior to the AD).

TrA IO EO RA ES

FastNaturalSlowF value

Ð 32 6 3719 6 81

275 6 4296 × 41*

14 6 5854 6 61

431 6 25735 × 06**

60 6 56109 6 97296 6 408

5 × 57*

57 6 54230 6 23677 6 444 × 76*

18 6 3930 6 67

212 6 10228 × 61**

TrA : transversus abdominus; IO : abdominus obliquus internus; EO : abdominus obliquusexternus; RA : rectus abdominus; ES : erector spinae.

*p< 0 × 05; **p< 0 × 0001.

1225Limb movement speed and trunk muscle contraction

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participant s was low. Both the mean and peak velocity were signi® cantly diŒerent

between each movement speed condition.

4. Discussion

The results support the hypothesis that changes in the magnitude of the reactive

forces acting on the spine in¯ uence the temporal relationship between the prime

mover of the upper limb and the associated contraction of the trunk muscles only

with movement at a slow speed. No signi® cant diŒerence was found between rapid

and self-paced movements. Therefore, anticipatory contraction of the abdominal

muscles accompanies normal functional movement and is not restricted to rapid limb

movements.

4.1. Methodologica l considerations

It is acknowledged that the movement speeds used in the current study and the study

of Rogers and Pai (1990) are somewhat arbitrarily de® ned and subject to

interpretation of the instructions for each condition by the individua l participants .

However, early pilot studies indicated that the activation pattern within each speed

class was robust and consistent over a range of velocities. As previously mentioned,

control of the speed of movement by tracing a marker with the hand changes the

behavioura l constraint of the task and has been shown to alter the sequence of

muscle contraction while velocity remained constant. Lee et al. (1987) reported

coincident biceps femoris and AD contraction when movement was guided and

contraction of biceps femoris preceding AD when the movement was unconstrained.

On this basis it was inappropriat e to further control the limb movement speed.

Owing to the resistance provided by the Position-Velocity Transducer cable at

the initiation of movement it was not appropriate to record the EMG data during

the same trial as the kinematic analysis . Although the resulting data may not

perfectly represent the movement speed in the EMG trial, it was anticipated that any

diŒerences would be minor. The participants who took part in the limb velocity trial

were randomly selected from the EMG data group and all instructions were identical

to those in the EMG trial and indicated a low variation between participant s for

each speed.

4.2. In¯ uence of speed of movement on associated postural muscle activity

The results support the ® ndings of a previous study indicating contraction of TrA

prior to the prime mover of shoulder ¯ exion (Hodges and Richardson 1997).

Although the contraction of TrA failed to occur prior to AD in the natural speed

condition the onset did occur within the 50 ms criteria for anticipatory muscle

Table 2. Mean and peak angular velocity of limb movement for each limb movement speedcondition (mean(SD)).

Limb speed condition Peak angular velocity Mean angular velocity

SlowNaturalFastF value

65 × 73 (18 × 2)265 × 22 (57 × 7)515 × 67 (97 × 89)

64 × 09*

40 × 38 (7 × 5)153 × 96 (34 × 5)309 × 1 (56 × 5)

69 × 62*

*p< 0 × 001.

1226 P. W. Hodges and C. A. Richardson

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contraction. In contrast, the onset of contraction of the trunk muscles with the slow

movement condition occurred after the onset of movement allowing time for the

response to be mediated by re¯ ex activity. The slow speed was the only condition in

which the speed of limb movement fell below the 100 8 /s threshold identi® ed by

Horak et al. (1984) as the point where onset of the paraspinal muscles failed to occur

in `anticipation ’ of the prime mover. Correspondingly the trunk muscle activation in

the slow movement condition represents a diŒerent control strategy to that

associated with the more rapid limb movements in which the response is

preprogrammed. This has also been identi® ed for lower limb movement at diŒerent

speeds (Rogers and Pai 1990).

The failure to ® nd a signi ® cant change in the temporal relationship between the

two faster movement condition s is consistent with the ® nding of Lee et al. (1987)

indicating a constant reaction time of ES with fast movement. This indicates that,

unlike the lower limb postural muscle, the muscles of the trunk that were

investigated are not in¯ uenced by the speed of limb movement or the magnitude

of the reactive forces above a certain unde ® ned threshold. The contrasting in¯ uence

of upper limb movement velocity on lower limb and trunk muscles identi® ed in the

current study suggests that postural muscles of each region may be acting to control

diŒerent components of the postural perturbation. This proposal is consistent with

the previously suggested diŒerences in the central nervous system control of the

postural responses of the segments (Burbaud et al. 1988, Lee et al. 1987). The

contribution of each to the control of dynamic reactive forces and compensation for

changes in body con® guration warrants further investigation . In contrast to the

temporal evaluation , animal and human studies have found a high correlation

between the amplitude of EMG of lower limb and trunk postural muscles with

increasing limb velocity (Burbaud et al. 1988, Lee et al. 1987).

Limb movement inertia and the magnitude of reactive forces may also be altered

by adding a load to the moving limb. The results of studies investigating changes in

load have been inconclusive . Studies have reported results ranging from minimal

in¯ uence of limb loading on the sequence of muscle activation (Horak et al. 1984) to

a contrasting in¯ uence of increased inertia on the reaction time latency of the ES and

biceps femoris muscles with biceps femoris being in¯ uenced to a greater extent than

ES (Friedli et al. 1984). A further study has reported an increase in the period

between the onset of postural muscle activity and the initiation of movement with

increased force of movement (Be raud and Gahe ry 1995).

The high frequency of trials in which a response was not recorded for each of the

trunk muscles with slow movement is consistent with previous studies indicating an

absence of anticipatory responses with slow movement (Crenna et al. 1987, Horak et

al. 1984, Lee et al. 1987). It has been suggested that passive mechanical forces from

inertia and relaxed trunk muscles may be su� cient to resist the low forces associated

with the slow movement condition (Lee et al. 1987).

The reported high variabilit y with movements at slow speeds is also consistent

with earlier ® ndings (Horak et al. 1984, Lee et al. 1987). Lee et al. (1987) suggest that

this may be related to the accuracy of EMG onset identi® cation. The initiation of

slow movement occurs with a slow increase in EMG amplitude compared to the

large burst associated with rapid movement. The delay in reaching the de® ned

threshold may delay and vary the identi ® ed onset point (Lee et al. 1987). In addition,

the low signal-to-noise ratio associated with the low amplitude of the EMG signal

increases the variabilit y of the onset identi® cation (DiFabio 1987). Since the onset of

1227Limb movement speed and trunk muscle contraction

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each of the muscles was similarly aŒected, including AD, the net in¯ uence is likely to

be minimal. Furthermore, visual inspection of the EMG traces con® rmed the validity

of this method of onset determination and any traces for which the computer-derived

onset was obviously incorrect were rejected.

4.3. Conclusion and implications for future research

This study has provided evidence for one of the mechanisms used by the central

nervous system to protect the back from injury and how this is aŒected by variation

in the magnitude of the forces acting on the spine as a result of limb movement.

Recent evidence suggests that the timing of contraction of the trunk muscles

(particularly TrA) is delayed in people with low-back pain (Hodges and Richardson

1996). Thus, understanding of the normal response of the trunk muscles and how

this is in¯ uenced by variation in movement parameters provides a basis for the

investigation of the e� ciency of this control system in an ergonomic environment.

The main conclusions that arise from this investigation are:

(1) Upper limb movement parameters have a limited in¯ uence on the reaction

time latency of the associated trunk muscle response indicating that these

muscles control a diŒerent component of the postural disturbance than the

lower limb postural muscles.

(2) Preprogrammed trunk muscle activity is associated with both self-paced and

rapid upper limb movement.

(3) The results provide initial normative data of the response of the trunk

muscles preparing the body for the postural disturbance provoked by limb

movement in a variety of conditions on which to base future workplace

evaluations.

Acknowledgements

The authors would like to thank Dr D. Cooper, Dr K. Frawley and Dr A. Toneki for

supervision of the insertion of the ® ne-wire electrodes, B. Bui for technical assistance

and I. Horton for statistical advice. This study was funded by the Menzies

Foundation , the Physiotherapy Research Foundation and the Dorothy Hopkins

Clinical Research Award.

ReferencesARUIN, A. S. and LATASH, M. L. 1995, Directional speci® city of postural muscles in feed-

forward postural reactions during fast voluntary arm movements, Experimental BrainResearch, 103, 323 ± 332.

BELEN’KII, V., GURFINKEL, V. S. and PALTSEV, Y. 1967, Elements of control of voluntarymovements, Bio® zika, 12, 135 ± 141.

BEÂ RAUD, P. and GAHEÂ RY, Y. 1995, Relationships between the force of voluntary leg movementsand the associated postural adjustments, Neuroscience Letters, 194, 177 ± 180.

BOUISSET, S. and ZATTARA, M. 1987, Biomechanical study of the programming of anticipatorypostural adjustments associated with voluntary movement. Journal of Biomechanics, 20,735 ± 742.

BURBAUD, P., GARANX, F., GROSS, C. and BIOULAC, B. 1988, Postural adjustments in themonkey: eŒects of velocity on EMG sequence, Neuroscience Letters, 84, 51 ± 56.

CORDO, P. J. and NASHNER, L. M. 1982, Properties of postural adjustments associated withrapid arm movements, Journal of Neurophysiology, 47, 287 ± 308.

CRENNA, A., FRIGO, C., MASSION, J. and PEDOTTI, A. 1987, Forward and backward axialsynergies in man, Experimental Brain Research, 65, 538 ± 548.

1228 P. W. Hodges and C. A. Richardson

Dow

nloa

ded

by [

Uni

vers

itaet

s un

d L

ande

sbib

lioth

ek]

at 0

5:20

02

Janu

ary

2014

CRESSWELL, A. G., GRUNDSTROM, H. and THORSTENSSON , A. 1992, Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man, ActaPhysiologica Scandinavica, 144, 409 ± 418.

DETROYER, A., ESTENNE, M., NINANE, V., VANGANSBEKE, D. and GORINI, M. 1990, Transversusabdominis muscle function in humans, Journal of Applied Physiology, 68, 1010 ± 1016.

DIFABIO, R. P. 1987, Reliability of computerised surface electromyography for determiningthe onset of muscle activity, Physical Therapy, 67, 43 ± 48.

FRIEDLI, W. G., HALLET, M. and SIMON, S. R. 1984, Postural adjustments associated with rapidvoluntary arm movements. 1. Electromyographic data, Journal of Neurology,Neurosurgery and Psychiatry, 47, 611 ± 622.

GAHEÂ RY, Y. and MASSION, J. 1981, Co-ordination between posture and movement, Trends inNeuroscience, 4, 199 ± 202.

HODGES, P. W. and BUI, B. 1997, A comparison of computer based methods for thedetermination of onset of muscle contraction using electromyography, Electroencepha-lography and Clinical Neurophysiology, 101, 511 ± 519.

HODGES, P. W. and RICHARDSON, C. A. 1996, Ine� cient muscular stabilisation of the lumbarspine associated with low back pain: a motor control evaluation of transversusabdominis, Spine, 21, 2640 ± 2650.

HODGES, P. W. and RICHARDSON, C. A. 1997, Feedforward contraction of transversusabdominis is not in¯ uenced by the direction of arm movement, Experimental BrainResearch , 114, 362 ± 370.

HORAK, F. B., ESSELMAN, P., ANDERSON, M. E. and LYNCH, M. K. 1984, The eŒects ofmovement velocity, mass displaced, and task certainty on associated posturaladjustments made by normal and hemiplegic individuals, Journal of Neurology,Neurosurgery and Psychiatry, 47, 1020 ± 1028.

LEE, W. A., BUCHANAN, T. S. and ROGERS, M. W. 1987, EŒects of arm acceleration andbehavioural conditions on the organisation of postural adjustments during arm ¯ exion,Experimental Brain Research, 66, 257 ± 270.

MASSION, J. 1992, Movement, posture and equilibrium: interaction and coordination, Progressin Neurobiology, 38, 35 ± 56.

PANJABI, M. M. 1992, The stabilising system of the spine. Part II. Neutral zone and instabilityhypothesis, Journal of Spinal Disorders, 5, 390 ± 397.

ROGERS, M. W. and PAI, Y. C. 1990, Dynamic transitions in stance support accompanying leg¯ exion movements in man, Experimental Brain Research, 81, 398 ± 402.

TESH, K. M., SHAWDUNN, J. and EVANS, J. H. The abdominal muscles and vertebral stability,Spine, 12, 501 ± 508.

ZATTARA , M. and BOUISSET, S. 1988, Posturo-kinetic organisation during the early phase ofvoluntary upper limb movement. I. Normal subjects, Journal of Neurology,Neurosurgery and Psychiatry, 51, 956 ± 965.

Appendix

Formulae for calculation of the angular limb velocity ( x ) from linear velocity (V)

and position (D) output of the transducer where Vh is the calculated linear velocity

vector at the cable attachment to the arm. Refer to ® gure 3 for de® nition of the other

parameters.

L2= R

2+ D

2Ð 2RDcos b (1)

b = cos Ð 1((R2+ D

2Ð L

2)/(2RD))

tan b = C2/D (2)

C2= Dtan b

cos b = D/C1 (3)

C1= D/cos b

1229Limb movement speed and trunk muscle contraction

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Vh/C1= V/C2 (4)

Vh/D/cos b = V/Dtan b (2) & (3) in (4)

Vh= V/sin b

Vh= R x (5)

x = Vh/Rx = (V/sin b )/R (4) in (5)

Figure 3. Parameters used for the calculation of the angular velocity of limb movement fromthe linear velocity and displacement data.

1230 P. W. Hodges and C. A. Richardson

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