Sprinting kinetics and acute muscle potentiation following handcycling exercise in persons with spinal cord injuries

Objectives: Post activation potentiation (PAP) is the phenomenon where muscle force-generating capacity during explosive activities increases after sustained activation. Alternatively, fatigue refers to the decrease in muscle force-generating capacity following sustained activation. The level to which muscles are fatigued or potentiated may influence whether performance is enhanced or decreased. While PAP has been well-documented in able-bodied athletes, few studies have examined PAP and muscle performance following exercise in athletes with spinal cord injuries (SCI). Therefore the objective of this study was to investigate the effect of handcycling exercise on acute muscle performance--defined as total work--and propulsion kinetics in people with SCI. Design: Within-subject design with repeated measures, n=19 wheelchair users. Method: We examined the kinetics, power output, and work completed during a maximal effort task (handcycling sprinting) before and after high intensity and moderate intensity exercise to determine the acute effects of different exercise intensities on muscle fatigue and potentiation. Results: Potentiation (defined as an increase in total work completed during sprinting) was observed after both moderate and high intensity exercise, with more participants potentiated following moderate compared to high intensity. Increases in work completed during the sprints can be traced back to increases in tangential force applied at the handcycle at the beginning of the sprint test. Conclusions: Most participants were not fatigued following either exercise protocol, which is encouraging for recommending both protocols for people with SCI. Additionally, warm-up exercises for handcycling, especially handcycling sprinting, should be moderate intensity to potentiate the muscles rather than interval cycling or “ramp up” activities.