Energetics of paraplegic cycling: Adaptations to 12 months of high volume training

Purpose: The efficiency of functional electrical-stimulation (FES) cycling in spinal cord injured and anaesthetised able-bodied cyclists has been found to be about one third of that reported during volitional cycling. The stimulation paradigm itself appears to be the main source of this inefficiency. It is unknown whether a period of high-volume training can induce adaptations that may influence the metabolic and electrical cost of FES cycling. Method: 11 individuals with paraplegia completed a 12-month, home-based, progressive FES cycle training programme (up to 5 x 60 min per wk). Stimulation cost, oxygen cost, efficiency and markers of anaerobic metabolism were determined before and after 6 and 12 months of training, during constant work-rate tests. Results: Oxygen cost and efficiency did not significantly change after training. Total stimulation cost and blood lactate values reduced overall, while respiratory exchange ratios remained relatively high. Conclusions: The high metabolic cost of FES cycling is a result of non-physiological recruitment of predominantly fast muscle fibres. The electrical cost of cycling reduced by 37%, probably due to motor unit hypertrophy, and lactate oxidation capacity improved.