There are obvious limitations of extrapolating the indirect evidence from this study. Nonetheless, along with studies demonstrating an effect of ES cycling on venous return (Elokda et al 2000, Faghri and Yount 2002, Sampson et al 2000), the study by Man and colleagues indicates some basis
for the rationale Selleckchem MK2206 that FES cycling in people with spinal cord injury influences venous return and lower limb swelling; a conclusion not supported by our leg circumference results. The results from the small number of studies examining the effects of FES cycling on spasticity are similar to ours with no clear indication of therapeutic effect (Krause et al 2008, Skold et al 2002, van der Salm et al 2006). The potential effect of FES cycling on urine output may have been missed because we only measured urine output over a one-hour period immediately after FES cycling. One hour may
be too short. However this seems unlikely because naturetic peptide has an immediate effect on the kidneys (Dunn and Donnelly 2007). If the release of naturetic peptide in response to an increase in venous return is the main mechanism by which FES cycling increases urine output, then our time frame for measurements of urine output should have been sufficient. Another possible explanation for our failure selleck inhibitor to find a convincing treatment effect is our use of a short intervention period, namely two weeks. A longer training period may have increased participants’ muscle bulk and stimulated strength (Baldi et al 1998) thereby Electron transport chain enhancing the muscle pump effect and venous return. Venous return may have been further increased by the stimulation of additional lower limb muscles however stimulation of more than three muscle groups is problematic as this requires additional expensive equipment not routinely available in the clinical setting. Future studies could manipulate some of these variables to determine their effect on urine output. Only the immediate effects of FES cycling were investigated and only at the
impairment level. We acknowledge that urine output, lower limb swelling and spasticity are surrogate measures for what is important to people with spinal cord injury, and clearly immediate effects are of little interest unless they are sustained. We however restricted the trial in this way to increase statistical power. In addition, it is potentially wasteful of resources looking for sustained effects of interventions on global measures of participation without first demonstrating immediate effects on surrogate measures. Importantly, FES cycling is advocated in people with motor complete lesions for reasons other than its effect on urine output, lower limb swelling and spasticity. For example, it is advocated on the basis that it increases cardiovascular fitness, muscle bulk and lean muscle mass.