An analytical model of a spinal root stimulated neuromuscular system

Leg cycle ergometry using functional electrical stimulation provides many health benefits for paraplegic users. The lumbo-sacral anterior root stimulator implant provides sufficient control over the muscles in the legs for leg powered cycling to be achieved, however for further development to take place, more knowledge is needed about the complicated pathways involved in the neuromuscular system from the nerve roots to the muscles in the leg. To achieve this, an analytical model has been developed from experimental measurements which predicts the force output from the leg due to stimulation on one of the twelve available channels dependent on stimulation level, duration of stimulation and leg position (crank angle). The model incorporates both linear and non-linear elements and is a first step towards a full model of the complicated non-linear processes involved in the neuromuscular system. The work here presents both the measurements used to develop the model and the modelled force response.