(V) over dotO2 Kinetics and Performance in Soccer Players after Intense Training and Inactivity

CHRISTENSEN, P. M., P. KRUSTRUP, T. P. GUNNARSSON, K. KIILERICH, L. NYBO, and J. BANGSBO. (V) over dotO(2) Kinetics and Performance in Soccer Players after Intense Training and Inactivity. Med. Sci. Sports Exerc., Vol. 43, No. 9, pp. 1716-1724, 2011. Purpose: The study's purpose was to examine the effects of a short-term period with intensified training or training cessation of trained soccer players on (V) over dotO(2) kinetics at 75% maximal aerobic speed, oxidative enzymes, and performance in repeated high-intensity exercise. Methods: After the last match of the season, 18 elite soccer players were, for a 2-wk period, assigned to a high-intensity training group (n = 7) performing 10 training sessions mainly consisting of aerobic high-intensity training (8 x 2 min) and speed endurance training (10-12 x 30-s sprints) or a training cessation group (n = 11) that refrained from training. Results: For the training cessation group, (V) over dotO(2) kinetics became slower (P < 0.05) with a larger time constant (tau = 21.5 +/- 2.9 vs 23.8 +/- 3.2 s (mean +/- SD, before vs after)) and a larger mean response time (time delay + tau = 45.0 +/- 1.8 vs 46.8 +/- 2.2 s). The amount of muscle pyruvate dehydrogenase (17%, P < 0.01) and maximal activity of citrate synthase (12%) and 3-hydroxyacyl-CoA (18%, P < 0.05) were lowered. In addition, the fraction of slow twitch fibers (56% +/- 18% vs 47% +/- 15%, P < 0.05), Yo-Yo intermittent recovery level 2 test (845 +/- 160 vs 654 +/- 99 m), and the repeated sprint performance (33.41 +/- 0.96 vs 34.11 +/- 0.92 s, P < 0.01) were reduced. For the high-intensity training group, running economy was improved (P < 0.05), and the amount of pyruvate dehydrogenase (17%) and repeated sprint performance (33.44 +/- 1.17 vs 32.81 +/- 1.01 s) were enhanced (P < 0.05). Conclusions: Inactivity slows (V) over dotO(2) kinetics in association with a reduction of muscle oxidative capacity and repeated high-intensity running performance. In addition, intensified training of already well-trained athletes can improve mechanical efficiency and repeated sprint performance.