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Elizabeth B. Brokaw, MS; Theresa Murray, BS; Tobias Nef, PhD; Peter S. Lum, PhD

Retraining of interjoint arm coordination after stroke using robot-assisted time-independent functional training. Elizabeth B. Brokaw, MS; Theresa Murray, BS; Tobias Nef, PhD; Peter S. Lum, PhD. Study aim

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Elizabeth B. Brokaw, MS; Theresa Murray, BS; Tobias Nef, PhD; Peter S. Lum, PhD

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  1. Retraining of interjoint arm coordination after stroke using robot-assistedtime-independent functional training Elizabeth B. Brokaw, MS; Theresa Murray, BS; Tobias Nef, PhD; Peter S. Lum, PhD

  2. Study aim • Develop time-independent functional training (TIFT), a haptic-based approach for retraining interjoint coordination poststroke. • Implement TIFT in ARMin III robotic exoskeleton. • Relevance: • Abnormal interjoint coordination is common after stroke. • Recovery is possible with focused intervention that inhibits compensatory strategies and promotes learning of proper interjoint coordination during reaching.

  3. Motor Learning Testing • 37 nondisabled subjects • 3 training groups: TIFT, visual demonstration, and time-dependent (TD) training. • Performed 8 blocks of 10 repetitions of task training with recall testing and 1 min of rest between each block. ARMin III robot and passive hand device, HandSOME, being used in functional shelf task.

  4. Training Results • TIFT subjects signifi-cantly reduced errors in training (p < 0.001) but TD subjects did not (p = 0.76). • Robot guidance torque decreased significantly across training blocks in TIFT (p < 0.001) but not TD (p = 0.67). Typical subject’s joint coordination pattern during TIFT training. Trajectories were disjointed in 1st training block (top)but smoother by 8th training block (bottom).

  5. Movement Recall Results • All three groups reduced error across movement recall blocks (p < 0.001). • Same observation for reduction of slope error (p = 0.018) and movement variability (p < 0.001). • However, no significant between-group differences for any metrics (p > 0.20). Error reductions during recall blocks with standard error bars.

  6. Conclusions • Can not yet recommend TIFT over more easily implemented TD, but TIFT warrants further study: • Theoretical advantages: • Minimally interferes with input/output map between correct muscle activation and movement. • Allows greater kinematic variability. • Requires subjects to produce proper interjoint coordination to advance. • Training advantages • Lower interaction forces between robot and human arm (thus arm contributing more to movement during TIFT). • Error and assistance forces reduced during TIFT but not TD.

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