Chronology of postural and focal component of muscular activity during manual wheelchair propulsion initiation: effect of different trajectories and velocities S. Chikh*, M-A. Dupuy*, C. Garnier*, E.Watelain*‡, E.Simoneau*, P.Pudlo* * Université Lille Nord de France, UVHC, LAMIH, CNRS-UMR 8201, F-59313 Valenciennes ‡ HandiBio, Université du Sud Toulon-Var, BP 20132 – F-83957 La Garde Cedex Keywords: Muscular Pattern; EMG; wheelchair; Anticipatory Postural Adjustment; Compensatory Postural Adjustment Procedure: At an auditory GO signal given by the experimenter, the participant had to perform an 1. Introduction indicated displacement over 3m. Muscular activity during manual wheelchair 12 experimental conditions were studied as a result propulsion was studied by several researchers. For of 3 possible directions (front F, left L or right R example, Mulroy et al. (2004) studied the effect of directions), 2 speeds (spontaneous SS or maximum Spinal Cord Injury (SCI) level on the functional speed MS) and 2 possible initial hands positions activity of shoulder during propulsion. Similarly, (Reach-To-Push: hands on the thighs HT or Push: abdominal and back muscles were studied by Yang hands on the handrails HH, see Figure 1). For each et al. (2006). More recently, in 2012, Kloosterman condition, the subject had to perform two trials, all et al. determined the influence of power-assisted presented in a completely randomized order. propulsion on shoulder muscle activation patterns and explored the effectiveness of power-assisted propulsion in preventing shoulder injuries. A movement can be decomposed in two main components: the focal (FC), in charge of the execution and the postural component (PC), in charge of both anticipatory postural adjustments (APA) and compensatory postural adjustments (CPA). In order to assess each component activity, Bouisset & Do (2008) have also determined that Reach-To-Push (HT) Push (HH) APA can be defined either with respect to EMGs, Figure 1: Experimental setup and the two initial i.e. the time interval between postural and focal positions of the hands. muscle EMG onset or with respect to biomechanical variables, i.e. the time interval Electromyography: between global dynamics onset and focal The electromyographic activity of shoulder and movement onset. Begongiari et al. (2011) trunk muscles was recorded using Bipolar Zero determined that APA corresponds to the activity of wire 16-channel EMG AURION amplifier. The raw PC between 200 ms before and 50 ms after the signals were digitized at a sampling rate of onset of movement initiation. The activity after 2000 Hz, filtered with a second order band-pass50 ms, called CPA, is a reactive response to filter of 10-500Hz. The electrodes were FOAM postural perturbations. Ag/AgCL- oval 32mm * 36mm and were placed on It seems necessary to investigate the chronological muscles of the left hand side (dominant hand) on order of postural and focal muscle activation for a motor points: i) focal component FC: anterior better understanding of the kinetic capacities of deltoids (AD), middle deltoids (MD), posterior each component during manual wheelchair deltoids (PD), pectoralis major (PM), long head of propulsion. The purpose of this study was then to biceps brachialis (BB), long head of triceps determine the muscular pattern of PC and FC brachialis (TB), brachialis (B), Serratus anterior according to different trajectories and velocities of (SA), latissimus dorsi (LD); ii) postural component displacements. This research is an exploratory PC: rectus abdominis (RA), obliquus externus study on one case. (EO), erector spinae thoracic (EST), erector spinae lumbar (ESL), upper trapezius (UP). The onset of 2. Methods the signal was determined by the first muscle being Participants: One healthy young male has activated:. The muscle is considered active when voluntarily participated in this study (age 25 yrs; the amplitude exceeds twice the base line activity. mass 102 kg; height 1.75m). The activation sequences were then automatically identified but visually verified. *Soufien CHIKH. Email:[email protected]

strategies for the same movement depending on the execution speed.

3.Results and Discussion Times conditions

HH_MS_F HT_MS_F

0ms

50ms

4. Conclusions

PD AD-BB-TB -LD- SA-B-PM-ESLRA-EO-EST-UP SA-B-PM-RA-EO-EST-ESL

TB-UP-MDPD-

AD-BB-LD

A : Effect of hands position (Front direction / Maximum speed). Muscles Framed = active muscles after 50ms for HH and before 50ms for HT. Muscles underlined = CPA. Times conditions

0ms

50

HH_MS_

R

PM-SA-LDESL-B

HH_MS_

F

MD

PD

AD-BB -B-PM-TB -SA-LD-ESLRA-EO-UP-EST

HH_MS_

L

PD-LD

B-MD-BBTB-EST-UP

AD -PM-SA-RA-EO-ESL

-PD-MD

TB-UP-RA-BB

B : Effect of trajectories (Handrail / Maximum speed). Muscles Framed = APA. Muscles underlined = CPA. PD=eg of same muscle differently active function of trajectories Times conditions

SS_F

HH_

MS_F

HH_

< 0ms

0ms

50

Muscles OFF

UP (-30ms)

ADMD

PD-BBTB-LD

SA-B- PM

RA-EO-ESTESL-

MD

PD

AD-BB-B-PMTB-UP-SA-LDESL RA-EOEST

C : Effect of velocities (Handrail / Front direction). Muscles OFF= inactivated. Muscles underlined= muscle of CP.

Table 1, examples of : A) Effect of initial hands position, B) Effect of trajectories, C) Effect of velocities on muscular activities. The results (Table1A-B-C) showed an anticipated (CP before 50ms) and compensatory (CP after 50ms) muscular activity during manual wheelchair propulsion initiation, with the activation of ESL, RA, EO, EST and UP. The two trials did not show any difference on muscular activities and suggest that the sequence of events is reproducible. We consider that no fatigue could be induced. Hands position (Table 1A): the muscular recruitment was different between both conditions: Push and Reach-to-push: AD-BB-LD and TB were activated after 50ms for HH and before 50ms for HT. The difference between movement parameters influences muscular recruitment. Trajectories (Table 1B). CP was influenced by the trajectory: EO, ESL, EST, RA and UP were not activated for front direction. For left and right directions, it was not the same muscles and chronological activation. For example, EST showed an activation in the left or right direction but not for the front one (at SS). The PD showed a different chronology activity between F, L, and R trajectories. Spontaneous vs maximum speed (Table 1C): All muscles were activated at MS but not at SS (RA, EO, ESL and EST were activated only in two of the six displacements). This result suggests several

This preliminary study showed that muscular pattern of focal and postural components were influenced by hands position (AD-BB-TB and LD activated after 50ms for HH and before 50ms for HT), trajectories (no activity for EST at F direction, and for PD, the activity was different between F, R, and L trajectories) and speed (RA-EO-EST and ESL activated only with MS, and not with SS). Thus, all initial conditions conduct to specific muscular chronology in the healthy participant of this study. Also, this study allows to compare the activity of PC (Yang et al. 2006) and the FC (Mulroy et al. 2004), and synthesize an anticipatory muscular activity. More studies will be necessary involving a greater number of healthy subjects, as well as participants with spinal cord injury (SCI) to study the effect of level of SCI on chronology of postural and focal muscles activity. It is also planned to investigate kinematic parameters simultaneously to EMG activities.

Acknowledgments This research was supported by International Campus on Safety and Intermodality in Transportation, the Nord/Pas-de-Calais Region, the European Community, the Regional Delegation for Research and Technology, the Ministry of Higher Education and Research and the National Center for Scientific Research.

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