Abstract

Previous investigators have reported that oxygen consumption (V02) continues to rise after the initial 2- to 3-min transient period of exercise when work exceeds approximately 60 of V02max. The purpose of this investigation was to examine the possible causes of this slow rise in V02. Eighteen subjects exercised for 20 min at 65 and at 80 of V02max on the bicycle ergometer. V02 ventilation (VE), and respiratory exchange ratio were monitored by a continuous computerbased system. Blood lactate concentration and rectal temperatures were measured at 2- to 3-min intervals during the exercise. V02 increased significantly from the 5th to 20th min of exercise in 81 of the testsat both levels of work intensity. The magnitude of the rise was not different for the two work loads. No evidence was found to support the lactacid explanation proposed for this rise. Increased temperature could account for 30 of the rise; the estimated cost of increased VE coult account for 30 and 81 of the rise at the two work loads. The sum of these factors could account for 60 and 111 of the rise in V02 at the 65 and 80 of V02max work loads. Verf.-Referat