Modality-specific Changes In Upper-body Muscular Strength Are Dependent Upon Initial Level Of Fat-free Mass In Untrained College Men

Abstract

There remains controversy concerning the most efficacious modality for improving muscular strength in untrained individuals. Furthermore, potential differences in training response may be confounded by initial body composition differences in untrained individuals. PURPOSE: To compare the effect of resistance training with free weights or weight machines on upper-body strength in untrained college men with differing body mass (BM) and/or fat-free mass (FFM) at training inception. METHODS: Untrained men were selected from a larger cohort (N = 1,502) and assigned to either a low FFM (LM; n = 184) or high FFM (HM: n = 164) groups based on the 15th and 85th percentiles of the skinfold-predicted FFM. Training groups included free weights (FW, n = 150), seated horizontal chest press (SCP, n = 117), and supine vertical press (SVP, n = 81). Training was conducted 3X/week for 12 weeks using a linear periodization program of increasing loads and decreasing repetitions. In addition, subjects performed 3 sets with their 10RM for supplemental arm and leg exercises during each training session. RESULTS: Prior to training, the HM group was significantly taller and had greater BM, FFM, and %fat than the LS group. Prior to initiating training, there was no significant difference in 1RM performance among the 3 mode groups. A multi-factorial ANOVA indicated that training resulted in a significantly greater (p = 0.03) strength gain in the HM group (10.8 ± 6.4 kg) compared to the LM group (9.3 ± 6.0 kg). BM and FFM did not change significantly following training in HM (81.4 ± 8.0 vs 81.5 ± 7.6 kg) and LM (54.4 ± 4.0 vs 53.1 ± 3.5 kg). However, BP/FFM increased significantly more in LM (1.00 ± 0.21 to 1.13 ± 0.25) than in HM (0.89 ± 0.23 to 0.99 ± 0.23). The SHP (12.2 ± 6.0 kg) and SVP (11.7 ± 6.3 kg) made significantly greater (p<0.001) strength gains than the FW group (6.2 ± 5.8 kg). The mode x FFM interaction was not significant (p = 0.27). CONCLUSIONS: Untrained men appear to experience greater increases in muscular strength when utilizing machines as opposed to free weights. While upper-body muscular strength in untrained men was independent of BM and FFM, it appears that a higher initial FFM results in a greater response to training with greater gains in absolute strength.