The oxygen uptake-power regression in cyclists and untrained men: implications for the accumulated oxygen deficit

The regression of oxygen uptake (VO2) on power output and the O2 demand predicted for suprapeak oxygen uptake (VO2peak) exercise (power output = 432 W) were compared in ten male cyclists [C, mean VO2peak = 67.9 (SD 4.2) ml.kg-1.min-1] and nine active, yet untrained men [UT, mean VO2peak = 54.1 (SD 6.5) ml.kg-1.min-1]. The VO2-power regression was determined using a continuous incremental cycle test (CON4), performed twice, which comprised several 4-min exercise periods progressing in intensity from approximately 40%-85% VO2peak. Minute ventilation (VE), heart rate (HR), respiratory exchange ratio (R), blood lactate concentration ([la-]b) and rectal temperature (Tre) were measured at rest and during CON4. The slope of the VO2-power regression was greater (P < or = 0.05) in C [12.4 (SD 0.7) ml.min-1.W-1] compared to UT [11.7 (SD 0.4) ml.min-1.W-1]; as a result, the O2 demand (at 432 W) was also higher (P < or = 0.05) in C [5.97 (SD 0.23) l.min-1] than UT [5.70 (SD 0.15) l.min-1]. Exercise R and [la-]b were lower (P < or = 0.05) in C in comparison to UT at all power outputs, whereas VE and HR were relatively lower (P < or = 0.05) in C at power outputs approximating 180 W, 220 W and 270 W. Differences in fat metabolism estimated over the first three power outputs accounted for approximately 19% of the difference in VO2-power slopes between the groups and up to 46% of the difference in VO2 at a given intensity.(ABSTRACT TRUNCATED AT 250 WORDS)