Lambert BS, Shimkus KL, Fluckey JD, Riechman SE, Greene NP, Cardin JM, Crouse SF. Anabolic responses to acute and chronic resistance exercise are enhanced when combined with aquatic treadmill exercise. Am J Physiol Endocrinol Metab 308: E192-E200, 2015. First published November 25, 2014; doi:10.1152/ajpendo.00689.2013.-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 ϭ 23, 37 Ϯ 11 yr, 29.6 Ϯ 4.6 kg/m 2 ; women: n ϭ 24, 38 Ϯ 12 yr, 27.53 Ϯ 6.4 kg/m 2 ) from the general population were tested for V O2max, body composition, and strength before and after training. All groups performed 12 wk of RT (2 wk, 3 ϫ 8 -12 sets at 60 to approximately 80% 1-repetition maximum). The RT-LTM and RT-ATM groups also performed 12 wk of LTM or ATM training (2 wk immediately post-RT and 1 wk in isolation, 60 -85% V O2max, 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% 2 H2O, 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 Ͻ 0.05). RT-LTM training was found to elicit the greatest decreases in percent body fat (Ϫ2.79%, P Ͻ 0.05). In the untrained state, acute RT-ATM exercise elicited higher 24-h myoFSRs compared with RT (ϩ5.68%/day, P Ͻ 0.01) and RT-LTM (ϩ4.08%/day, P Ͻ 0.05). Concurrent RT-ATM exercise and training elicit greater skeletal muscle anabolism than RT alone or RT-LTM. concurrent training; aquatic exercise; skeletal muscle; aquatic treadmill; protein metabolism IN RECENT YEARS, AQUATIC EXERCISE HAS GROWN in popularity in the general, overweight, elderly, and athletic populations as a mode of therapeutic or rehabilitative exercise (43, 66). Aquaticbased running exercises such as deep water running and aquatic treadmill (ATM) running (Fig. 1) have also been shown to be effective alternatives to land-based aerobic exercises for promoting increases in aerobic fitness (11,18,38). Recently, we compared the efficacy of ATM training with traditional land treadmill (LTM) training using a training prescription similar to that recommended by the American College of Sports Medicine (ACSM) (38). Following training, increases in aerobic capacity and decreases in fat mass were similar regardless of training mode. However, leg lean mass [measured with dual-energy X-ray absorptiometry (DEXA)] was increased significantly following ATM training, twice that of the LTM group. We suspected that because vertical load, lateral resistance, and skeletal muscle activation have been shown to differ between ATM exercise and traditional LTM exercise (67), chron...