Relationship between changes in tracking performance and timing and amplitude of biceps and triceps EMG following training in a planar arm robot in a sample of people with post-stroke hemiplegia

Burridge, Jane, Freeman, Chris, Hughes, Ann-Marie, Rogers, Eric, Lewin, Paul and Chappell, Paul (2010) Relationship between changes in tracking performance and timing and amplitude of biceps and triceps EMG following training in a planar arm robot in a sample of people with post-stroke hemiplegia. ISEK 2010: The XVIII Congress of the International Society of Electrophysiology and Kinesiology, Aalborg, Dominica. 15 - 18 Jun 2010.

Abstract

AIM: To investigate changes in motor performance (target tracking), timing and amplitude of biceps and triceps muscle activity (EMG), in a sample of people with upper limb hemiplegia following stroke, before and after training in a planar robot.

METHODS: In a planar robot, in which the arm was supported by a hinged arm-holder and constrained to move in 2 dimensions, five chronic stroke participants practiced a subset (chosen to be appropriate to ability) of nine tracking tasks in which trajectory (orientation and length), speed and resistance to movement were varied during 18 (n=3) and 25 (n=2) one-hour training sessions. During tracking, electrical stimulation (ES) (40Hz biphasic, fixed amplitude, variable pulse-width; 0-300µs) was delivered via a commercially available CE marked stimulator using surface self-adhesive electrodes to the triceps muscle. Iterative Learning Control (ILC) algorithms were applied to reduce tracking error on consecutive trials by adjusting the pulse width and timing of ES. Immediately before training and after session 18, EMG and tracking performance (without ES) data were recorded during nine tasks. EMG signals were recorded from seven muscles including triceps and biceps using Noraxon Dual Ag-AgCl snap electrodes positioned according to SENIAM guidelines. EMG signals for each muscle were also recorded during maximum voluntary isometric contraction (MVIC). EMG signals were sampled at 1500Hz, amplified x2 at the electrodes to reduce the signal to noise ratio. Further EMG signal processing was performed using Matlab (7.2.0.232). Data were zero-phase filtered, using a fourth order Butterworth filter with passband 10-500Hz, then full wave rectified and smoothed using a moving average filter with 0.1s window. EMG data was normalised using the MVIC.

RESULTS: Analysis of the pre intervention EMG data showed that, for all stroke participants, timing and amplitude of peak EMG activity in biceps and triceps during all tasks differed from the mean of neurologically intact participants (n=8) (p<0.05), using data recorded under the same conditions. Analysis of pre intervention and post session18 EMG data, showed statistically significant (p<0.05) changes (mean of all tracking tasks) in timing and amplitude of biceps and timing of triceps EMG towards those of neurologically intact participants. Changes in tracking performance showed a statistically significant (p<0.03) reduction in error of the 9 tasks. An association between improved tracking performance and changes in timing and amplitude of EMG was identified. A statistically significant interaction (ANOVA) between tracking and timing of biceps (p=0.03) and tracking and amplitude of triceps (p=0.04) was detected but not between amplitude of biceps or timing of triceps (i.e. the variables that showed the greatest change towards normal).

CONCLUSION: Five people with upper limb post-stroke hemiplegic underwent 18 training sessions in a planar arm robot in which ES of triceps, mediated by ILC, was used to correct tracking error. An improvement in motor performance and changes in EMG activity in biceps and triceps were observed. An interaction was found between improvement in tracking and some but not all EMG variables.

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Contributors

Author: Jane Burridge

Author: Ann-Marie Hughes

Author: Eric Rogers

Author: Paul Lewin

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