Physiological effects of constant versus variable power during endurance cycling

Purpose: Previous theoretical research found that varying power slightly to counter external conditions may result in improved performance during cycling time trialing, but it is not known whether such power variations result in added physiological stress. Thus, the purpose of this study was to determine whether variable power (VP) cycling produced greater physiological stress than constant power (CP) cycling of the same mean intensity. Methods: Eight trained male cyclists (age 28 +/- 2 yr, mass 74.4 +/- 2.3 kg, (V) over dotO(2max) 4.24 +/- 0.13 L.min(-1), weekly training 277 +/- 44 km) performed three 1-h ergometer trials. The first trial was performed at a self-paced maximal effort. The mean power from that trial was used to determine the power for the CP trial (constant effort at mean power) and the VP trial (alternating +/- 5% of mean power every 5 min). Results: No differences were found between the CP and VP trials in mean (V) over dotO(2) (CP 3.33 +/- 0.11 L.min(-1), VP 3.26 +/- 0.12 L.min(-1)), mean heart rate (CP 158 +/- 3 min(-1), VP 159 +/- 3 min(-1)), mean blood lactate concentration (CP 4.2 +/- 0.7 mM, VP 4.3 +/- 0.7 mM), or mean RPE (CP 13.9 +/- 0.4, VP 14.1 +/- 0.4). Conclusion: Therefore, during a strenuous 1-h effort (78% of (V) over dotO(2max)), subjects experienced no additional physiological stress by varying power +/- 5% compared with that during a constant power effort.