Testing an Adjustable Ankle Orthosis During Walking in Cerebral Palsy

Primary outcomes

1. Change in Muscle Activity

   Time frame: day 1

   Change in integrated soleus electromyography (mV/mV) muscle activity during stance phase of walking.

2. Change in Metabolic Cost of Transport

   Time frame: day 1

   Change in metabolic cost of transport during walking. To calculate the metabolic cost of transport, the standing baseline metabolic rate for each participant and each trial was subtracted from their walking metabolic rate to estimate the net metabolic rate of walking. Next, we normalized the net metabolic rate of walking by each participant's body mass (m) and walking speed to calculate the metabolic cost of transport (J/kg*m), averaged over the last two minutes of each condition.

3. Change in Ankle Power

   Time frame: 1 day during walking

   Change in peak ankle power during stance phase measured in w/kg. Ankle kinematics and kinetics were calculated in OpenSim using the collected three-dimensional motion capture and the ground reaction forces. The joint kinematics and ground reaction forces were filtered using a low pass fourth order recursive Butterworth filter with a cut-off frequency of 6 Hz before being used to calculate joint kinetics. The ground reaction forces were collected using two force places associated with the instrumented treadmill (Bertec Corp, Columbus, USA) collected at 1200 Hz. The resultant joint kinetics were then further filtered using the same filtering parameters. Ankle joint power was calculated as the product of the joint moment and joint angular velocity.