Effect of aerobic and strength training on gas exchange kinetics during moderate- and heavy-intensity exercise in elderly

Introduction Aerobic training accelerates Phase II of V’O2 kinetics at the onset of moderate intensity exercise (M) and decreases the amplitude of the slow component (A3) during heavy-intensity exercise (H). The physiological causes of the slow component are still matter of debate. The progressive recruitment of the less economical Type II muscle fibers during H (Jones et al., 2005) may be implied in its genesis. The increase of muscle strength caused by resistance training would decrease the number of Type II muscle fibers recruited during H at the same workload (WL), wherefrom a smaller A3 may derive. Methods 12 active older men (69.4±4.3 yy; 78.5±10.5 kg; 171.2±5.3 cm; V’O2peak: 29.5±4.1mL/kg/min) were exposed to 8 weeks of: i) high intensity interval training (HIT), 7 2-minute cycling repetitions @90% of V’O2peak (V’O2p), 3 times/week and, after 4 months, ii) isoinertial resistance training (IRT), 4 × 7 maximal concentric-eccentric knee extensions, 3 times/week. Before and after trainings we measured: i) V’O2p and gas exchange threshold (GET); ii) B-by-B V’O2 at the onset of: a) moderate intensity (M; @WL equal to 80 % of GET; n = 4); and b) heavy-intensity exercise (H, @WL equal to 50% between GET and V’O2p assessed before training; n = 3); iii) isokinetic concentric torque (Tc) and isometric torque (Ti) of the limb extensors. V’O2 kinetics were modeled, after synchronization and averaging, by means of double or triple exponential functions. Results Only HIT led to a significant increase of absolute and relative V’O2p (P < 0.05). IRT brought about a significant increase of Tc and Ti (P > 0.05). The time constant of Phase II of V’O2 kinetics ( 2) during M was significantly faster only after HIT (19.5 vs. 27.3; P < 0.05); the amplitude (A2) of V’O2 response during M was significantly lower at the end of IRT (-10%, P < 0.05) than after HIT. After HIT, A3 was smaller than before training. Conversely, A3 was not affected by IRT. Discussion 8 weeks of HIT induced a significant acceleration of V’O2 kinetics during M and decreased the amplitude of A3 during H. On the contrary, IRT did not elicit any substantial effect on the characteristics of the slow component assessed during H. However, IRT resulted in a significant decrease of A2 during M, indicating an amelioration of the economy of exercise. These findings are in agreement with the ones obtained in young adults (Zoladz et al., 2012) and may suggest that IRT can have beneficial effects on performance of endurance events. References Jones AM, Pringle JSM, Carter H. (2005) Oxygen uptake kinetics in sport, exercise and medicine, 261-293, NY. Zoladz JA, Szkutnik Z, Majerczak J, Grandys M, Duda K, Grassi B. (2012) Eur J Appl Physiol 112, 4151–4161.