Visuomotor ankle force training in individuals with spastic cerebral palsy compared to their typically developed peers
O’Brien S[1,2], Carroll T[1,2], Barber L[3,4] and Lichtwark G[1,2].
1. School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Australia.
2. Centre for Sensorimotor Performance, The University of Queensland, Brisbane, Australia.
3. School of Health, Medical and Applied Sciences, Central Queensland University, Bundaberg, Australia.
4. Child Health Research Centre, Faculty of Medicine, The University of Queensland, Brisbane, Australia.
Lower limb motor impairment produces inefficient gait in individuals with Cerebral Palsy (CP) due to their reduced ability to activate muscles in an appropriate pattern. The trainability of lower limb muscle control in CP is unknown. We tested whether 6 weeks of training involving visuomotor force tracking can improve ankle control, voluntary activation capacity and strength in individuals with CP. Four spastic type CP ([mean+SD] 20.87+1.13yrs, 2 males, hemiplegia=3, diplegia=1, GMFCS I=3, III=1) and nine typically developed (TD) (22.76+2.07yrs, 2 males) individuals completed 18 training sessions for the affected (CP) or dominant (TD) ankle. Isometric maximum voluntary plantarflexion strength, voluntary activation (using supramaximal tibial nerve stimulation), and tracking accuracy were assessed. Data were analysed as the absolute pre-post mean difference (95%CI). Voluntary activation and plantarflexion strength were 35.3% and 61.0% lower in CP than in TD, and did not improve in either group following training (TD:2.2%(-4.9:9.2%), CP:5.7%(-7.2:18.6%); TD:-4.6Nm(-18.0:8.7Nm), CP:5.6Nm(-3.3:14.6Nm)). Tracking accuracy was lower for CP than TD at baseline. Following training maximum cross-correlation co-efficient improved across all difficulties in TD only (TD: low=0.04(0.02:0.06), moderate=0.11(0.09:0.13), high=0.12(0.09:0.16) vs CP: low=0.19(-0.04:0.43), moderate=0.17(-0.003:0.35), high=0.29(-0.004:0.60)). Mean error improved across all difficulties in both groups (TD: low=-0.43Nm(-0.82:-0.05Nm), moderate=-0.94Nm(-1.39:-0.49Nm), high=-0.89Nm(-1.36:-0.44Nm); CP: low=-0.81Nm(-1.39:-0.23Nm), moderate=-0.69Nm(-1.02:-0.35Nm), high=-0.77Nm(-1.45:-0.09Nm)). The training stimulus was not sufficient to illicit improvements in maximal muscle output but indicates potential for learning to improve appropriate muscle patterning in response to a specific task in CP. Additional participants are required to understand the impact and utility of visuomotor ankle training for improving control in CP.