Gas exchange during bicycle exercises preceded or not by loadless pedalling in female and male subjects

The effects on ventilation and oxygen uptake of pedalling with no load on the ergometer before exercise have been investigated in 10 subjects (6 males and 4 females). It has been found that: (1) the O2-deficit calculated at the beginning of exercise is less variable and generally reduced when exercise has been preceded by a loadless pedalling period; (2) for a given steady-state VO2, the O2-deficit is larger in female than in male subjects; (3) the respiratory equivalents for oxygen and for carbon dioxide are not affected by loadless pedalling; they are generally larger in female than in male subjects; (4) the increase in ventilation at the beginning of exercise is smaller after loadless pedalling but this seems to be apparent only in male subjects; (5) the pattern of breathing and heart rate are not affected by loadless pedalling. It is concluded that pedalling with no load on the ergometer before the exercise prepares the subject to deliver oxygen more rapidly to the muscles. It then reduces the variability in gas exchanges and the O2-deficit. Several factors which may account for this better efficiency of oxygen delivery are discussed.