Methodological effects on the VO₂-power regression and the accumulated O₂ deficit

The VO₂-power regression and O₂ demand predicted for a supra-VO_2peak intensity (i.e., 432 W) were determined in seven well-trained male cyclists (mean ± SD: VO_2peak = 5.29 ± 0.51 l · min^-1), using five incremental exercise protocols. These protocols were either continuous (CON) or discontinuous (DISCON), and comprised five to eight work bouts ranging in intensity between 40% and 85% VO_2peak; the work bouts differed in duration (4-15 min), and the VO₂ was measured during the 4th minute (CON4, DISCON4), from min 4 to 6 (DISCON6), 8 to 10 (DISCON10), or 13 to 15 (DISCON15) of each work bout. The y-intercepts of the VO₂-power regressions were not different (P > 0.05), whereas the slope was higher (P ≤ 0.01) when determined using DISCON10 (12.7 ± 0.9 ml · min^-1 · W^-1) and DISCON15 (12.5 ± 0.9 ml · min^-1 · W^-1) compared with DISCON6 (12.2 ±1.0 ml · min^-1 · W^-1), DISCON4 (11.6 ± 1.1 ml · min^-1 · W^-1 or CON4 (11.9 ±0.7 ml · min^-1· W^-1). The O₂ demand (at 432 W) was also higher (P ≤ 0.01) for DISCON10 (6.05 ± 0.29 l · min^-1) and DISCON15 (6.05 ± 0.28 l · min^-1) compared with DISCON6 (5.88 ±0.31 l · min^-1), DISCON4 (5.70 ± 0.31 l · min^-1) and CON4 (5.82 ± 0.25 l · min^-1). This demonstrates that the O² demand predicted for high power outputs depends on the incremental protocol used.