The effects of hybrid cycling on lower-body soft tissue composition and bone density in people with long- term spinal cord injury: a randomized controlled trial

Janssen TWJ. Effects of hybrid cycling on lower-body soft tissue composition, and proximal tibia and distal femur bone mineral density in inactive people with long-term spinal cord injury: a 16-wk randomized controlled trial. PLoS One. Abstract Objective: To investigate the effects of hybrid cycle exercise on soft tissue composition of the legs, proximal tibia and distal femur bone mineral density (BMD), and bone turnover markers in people with long-term spinal cord injury (SCI). Setting: Two rehabilitation centers with a specialized SCI unit. Participants: Physically inactive and wheelchair-dependent individuals with long-term SCI (aged 28–65; time since injury ≥ 8 years; age at onset SCI ≥ 18 years). Interventions: The experimental group received a 16-week hybrid cycle (voluntary arm exercise combined with functional electrical stimulation (FES)-induced leg exercise) training program, while the control group received a 16-week handcycle program. Outcome measures: soft tissue composition of the legs (lean and fat mass), proximal tibia and distal femur BMD, and bone turnover markers (procollagen type 1 amino-terminal propeptide (P1NP) and cross-linked C-telopeptide (CTX)) were obtained in the week before and after the training program. Results: Thirty-six people were included, of which 20 participants (10 hybrid cycle, 10 handcycle) completed the study and were analyzed for all outcome measures. Following the 16-week program, lean mass of the legs was increased with 0.86 ± 0.26 kg (p = 0.029) in the hybrid cycle group, and decreased with 0.78 ± 0.27 kg (p = 0.045) in the handcycle group. For fat mass of the legs, an overall reduction of 0.35 ± 0.13 kg (p = 0.03) was found. For proximal tibia and distal femur BMD, no significant main effects for time were observed. Furthermore, there was an overall reduction of 3.6 ± 1.7 μg/L (p = 0.05) in P1NP, and no significant overall change over time (p = 0.53) for CTX. No significant differences over time between the two training groups were found for leg fat mass, proximal tibia and distal femur BMD, P1NP and CTX. Conclusion: Hybrid cycling leads to improvements in soft-tissue composition of the legs, but does not improve proximal tibia and distal femur BMD, and bone turnover makers.