Effects of age and mode of exercise on power output profiles during repeated sprints

The aim of this study was to compare power output profiles during repeated cycling and running sprints in children and adults. On two separate visits, 12 boys [11.7 (0.5) years] and 13 men [22.1 (2.9) years] performed ten consecutive 10-s sprints interspersed with 15-s recovery intervals on a non-motorised treadmill and cycle ergometer. Peak (PPO) and mean (MPO) power outputs were measured during each sprint. Capillary fingertip blood samples were drawn at rest and 3 min after the final sprint to measure lactate accumulation (Δ[La]). PPO and MPO decreased significantly more in adults compared to children over the ten sprints irrespective of the mode of exercise (P < 0.001). PPO decreased by a similar amount during running and cycling in children (-17.7 versus -14.3 %, P > 0.05, respectively) and adults (-43.3 versus -40.0%, P > 0.05, respectively). In contrast, MPO decreased significantly more during running compared to cycling both in children (-28.9 versus -18.7%, P < 0.05) and adults (-47.0 versus -36.7%, P < 0.05). The greater decrease in MPO during running compared to cycling was accompanied in children by significantly higher Δ[La] values (7.7 versus 4.1 mmol l^-1, P < 0.001). In adults, blood lactate accumulation tended to be higher during running than cycling (12.7 versus 10.8 mmol l^-1, P = 0.06). To conclude, adults displayed a greater decrement in power output compared to children over the ten repeated running and cycling sprints. Furthermore, children and adults experienced greater fatigue during running compared to cycling. This last result may be attributed to additional muscle recruitment during sprint running.