Intermittent and continuous running. (A further contribution to the physiology of intermittent work.)

Abstract

AbstractIntermittent running on a tread mill at a speed of 20 km/h (12.4 miles/h) is analysed and a comparison between this work and continuous running at the same speed has been done. The present results are in agreement with the assumption that stored oxygen plays an important role for the oxygen supply during short spells of heavy work. When running intermittent 6.67 km in 30 min (effective work 20 min and rest 10 min), a trained subject attained a total O2 uptake of 150 1. With an O2 uptake of 0.4 1/min at rest standing at the tread mill, or 4 1 per 10 min of rest, 146 1 O2 are due to the 20 min of work. The actual uptake at work was only 101 1 and if normal values are assumed during rest pauses, a deficit in oxygen transport of 45 1 arises during the 20 min of actual work. This quantity will be taken up during the 120 rest pauses of 5 sec each. Two thirds of the oxygen demand during the 120 work periods of 10 sec each will accordingly be supplied by oxygen transported with the blood during work, and one third will be covered by a reduction in the available oxygen stores in the muscles, which in turn will be reloaded during the subsequent 5 sec rest periods. Respiratory and circulatory functions at intermittent and continuous running with special reference to maximal values are discussed. Research on intermittent work may open up a new field in work physiology.