Anabolic responses to acute and chronic resistance exercise are enhanced when combined with aquatic treadmill exercise

Aquatic treadmill (ATM) running may simultaneously promote aerobic fitness and enhance muscle growth when combined with resistance training (RT) compared with land-treadmill (LTM) running. Therefore, we examined acute and chronic physiological responses to RT, concurrent RT-LTM, and concurrent RT-ATM. Forty-seven untrained volunteers (men: n = 23, 37 ± 11 yr, 29.6 ±4.6 kg/m²; women: n = 24, 38 ±12 yr, 27.53 ± 6.4 kg/m²) from the general population were tested for VO_2max, body composition, and strength before and after training. All groups performed 12 wk of RT (2 wk, 3×8–12 sets at 60 to approximately 80% 1-repetition maximum). The RT-LTM and RTATM groups also performed 12 wk of LTM or ATM training (2 wk immediately post-RT and 1 wk in isolation, 60–85% VO_2max, 250–500 kcal/session). Additionally, 25 subjects volunteered for muscle biopsy prior to and 24 h post-acute exercise before and after training. Stable isotope labeling (70%²H₂O, 3 ml/kg) was utilized to quantify 24 h post-exercise myofibrillar fractional synthesis rates (myoFSR). Mixed-model ANOVA revealed that RT-ATM but not RT-LTM training produced greater chronic increases in lean mass than RT alone (P < 0.05). RT-LTM training was found to elicit the greatest decreases in percent body fat (-2.79%, P <0.05). In the untrained state, acute RT-ATM exercise elicited higher 24-h myoFSRs compared with RT (+5.68%/day, P < 0.01) and RT-LTM (+4.08%/day, P < 0.05). Concurrent RT-ATM exercise and training elicit greater skeletal muscle anabolism than RT alone or RT-LTM.