Altered contractile properties of the quadriceps muscle in people with spinal cord injury following functional electrical stimulated cycle training

Study design: A longitudinal training study. Objectives: To assess if contractile speed and fatigability of paralysed qu adriceps muscles in individuals with spinal cord injury (SCI) can be altere d by functional electrical stimulation leg cycle ergometry (FES-LCE) traini ng. Settings: The Sint Maartenskliniek rehabilitation centre and the University of Nijmegen, Nijmegen, the Netherlands. Methods: Contractile properties of the quadriceps muscle were studied in se ven people with motor-complete SCI who participated in a FES-LCE training p rogram. Subjects trained for 30 min, three times per week for 6 weeks. Cont ractile speed and fatigue characteristics of electrically stimulated isomet ric contractions were compared before and after 6 weeks of FES-LCE. Results: Fatigue resistance improved following FES-LCE training as indicate d by the higher forces maintained in response to repetitive electrical stim ulation. In contrast with an improved fatigue resistance, the maximal rate of force rise was unaffected, the speed of relaxation increased and the fus ion of a 10 Hz force signal decreased. Furthermore, the force-frequency rel ationship shifted to the right at low stimulation Frequencies, indicated by a decline in the ratio of 1 and 100 Hz force responses as well as the rati o of 10 and 100 Hz force responses. Conclusion: FES-LCE training can change the physiological properties of the quadriceps muscle in people with SCI. Even after a short period of trainin g, the stimulated muscles become more resistant to fatigue. Furthermore, th e increased speed of relaxation and associated decreased fusion and altered force-frequency relationship following training may be related to adaptati ons in the calcium handling processes, which reflect an early response of l ong-term disused muscles.