DISSOCIATED OXYGEN-UPTAKE RESPONSE TO AN INCREMENTAL INTERMITTENT REPETITIVE LIFTING AND LOWERING EXERCISE IN HUMANS

Five subjects performed a maximal exercise test of repetitive lifting and lowering, with a discontinuous protocol of incremental exercise (3 min) and relative rest (2 min). Exercise periods consisted of repetit ive lifting and repetitive lifting and lowering at increasing movement frequencies. Relative rest periods consisted of ergometer cycling at a constant, low power output. An unexpected, dissociated, response of cardiovascular and pulmonary parameters was found: during relative res t, values for oxygen uptake, carbon dioxide production, pulmonary vent ilation and tidal volume were significantly higher than during the pre ceding exercise periods, though exercise intensity was much lower. To our knowledge, such a response has not been reported in previous studi es. Since the response could not be attributed to methodological or te chnical factors, it is hypothesized that the type of exercise itself i mpeded the optimal performance of the oxygen transporting system. The function of the pulmonary system could have been influenced by a high intra-abdominal pressure, the involvement of respiratory muscles in st abilizing trunk and head, a flexed trunk posture and the entrainment o f respiratory frequency with movement frequency. More likely, the func tion of the cardiovascular system was hindered by a high blood pressur e and high intramuscular pressures. Since this response occurred at lo w exercise intensities, optimal functioning of the cardiovascular and pulmonary system during daily activities of repetitive lifting and low ering could similarly be impeded. The hypotheses put forward could als o explain the lower peak oxygen uptake reported during repetitive lift ing, compared to running and cycling.