this article and any supplementary material should be cited as follows: brokaw eb, murray t, nef t,...

This article and any supplementary material should be cited as follows: Brokaw EB, Murray T, Nef T, Lum PS. Retraining of interjoint arm coordination after stroke using robot-assisted time-independent functional training. J Rehabil Res Dev. 2011;48(4):299–316. DOI:10.1682/JRRD.2010.04.0064

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– 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.


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.


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).


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.


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.

this article and any supplementary material should be cited as follows: brokaw eb, murray t, nef t,...

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