Effect of the o₂ time-averaging interval on the reproducibility of o_2max in healthy athletic subjects

Aims: Limited research has investigated the most appropriate oxygen uptake (o₂) data averaging method to obtain reliable and valid maximal oxygen uptake (o_2max) values. This study investigated the effect of the o₂ time-averaging interval on the reproducibility of o_2max.

Methods and results: Twenty-two competitive distance runners (six female) performed two identical incremental treadmill tests to their limit of exercise tolerance separated by at least 48 h. Commencing at 7 km h⁻¹, running speed was increased by 1 km h⁻¹ per minute for five stages and 0·5 km h⁻¹ thereafter. Breath-by-breath o₂ data collected during each incremental test were time-averaged over 10-, 15-, 20-, 30- and 60-s and the highest averaged o₂ value was regarded as o_2max for each time-averaging interval. The o_2max values derived from different o₂ time-averaging intervals were significantly different for the first (F = 39·6; P<0·001) and second (F = 68·9; P<0·001) incremental test. There was a tendency for o_2max to significantly increase as the time-averaging interval became shorter. The reproducibility of o_2max was similar for all five o₂ time-averages, with no significant differences between the within-subject variance (F = 0·4; P = 0·6).

Conclusion: The results of this study suggests that the reproducibility of o_2max is not affected by the length of the o₂ time-average interval. However, o_2max was significantly altered by changing the o₂ time-averaging interval between 10 and 60 s. Consistency in the o₂ time-averaging interval is therefore an important methodological consideration for repeated determinations of o_2max.