Changes in oxygen uptake, shoulder muscles activity, and propulsion cycle timing during strenuous wheelchair exercise.

STUDY
DESIGN: Cross-over study.
OBJECTIVE: To determine the effect of strenuous wheelchair exercise on oxygen uptake (VO2 ), muscle activity and propulsion cycle timing (including the push time and recovery time during one full arm cycle).
SETTING: Laboratory of Sport Sciences at the University of France-Comte in France.
METHODS: Two exercise bouts of 6-min duration were performed at a constant workload: (1) non-fatigable exercise (moderate workload) and (2) fatigable exercise (heavy workload). Measurement of VO2, surface electromyographic activity (EMG) from shoulder muscles, and temporal parameters of wheelchair ergometer propulsion were collected from eight able-bodied men (26+/-4 years).
RESULTS: A progressive increase in VO2 associated with EMG alterations (P<0.05), and a decrease of the cycle and recovery time (P<0.05) during the heavy exercise. Whereas the push time remained constant, an increased muscle activation time (P<0.05) was found during heavy exercise.
CONCLUSION: Observations during wheelchair ergometry indicate the development of fatigue and inefficient muscle coordination, which may contribute to deleterious stress distributions at the shoulder joint, increasing susceptibility to injury.