Abstract
Step incremental exercise tests are widely used to assess endurance performance determinants; however, to what extent step duration influences oxygen uptake (V̇O(2)) and carbon dioxide production (V̇CO(2)) is unclear. This study assessed the influence of sampling duration on V̇O(2), V̇CO(2), and fat oxidation (Fat(ox)) across different exercise intensities and modalities, and participant age and biological sex during graded exercise tests. A total of 169 participants (41 females; peak V̇O(2) [V̇O(2)peak]: 54.7 ± 8.6 mL/kg/min) completed a running (n = 96) or cycling (n = 73) submaximal step test with V̇O(2) and V̇CO(2) measured continuously. Each stage was 6 min, and three 30 s averaging windows (2.5-3, 3.5-4, and 4.5-5 min) were compared to the 5.5-6 min reference. Linear mixed models assessed the effects of averaging window, exercise intensity domain, biological sex, age, fitness status, and exercise modality. The analysis included 1031 valid stages (588 running; 443 cycling). In running, V̇O(2) differences from the 6-min averaging window were observed at 3 (-28 mL/min), 4 (-15 mL/min), and 5-min averaging windows (-8 mL/min) (all p < 0.001), with similar results for V̇CO(2). No differences in V̇O(2) or Fat(ox) between averaging windows were observed in cycling. These findings were consistent across exercise intensity, fitness status, biological sex, and age. Averaging window differences were < 2% for all conditions. Despite subtle differences, 3-, 4-, and 5-min averaging windows do not meaningfully impact V̇O(2), V̇CO(2), or Fat(ox) compared to a 6-min stage duration. In conclusion, stage durations of ≥ 3 min may be sufficient to estimate these variables in running and cycling in participants with a wide range of characteristics.