A Comparison of the Effects of Two Resistance Training Protocols on Physiological Responses in Middle-Aged Men

Purpose. The purpose of this study was to investigate and compare the effects of two types of resistance training protocols on the adaptations in skeletal muscle size and strength, changes in the endocrine system, inflammatory markers, bone markers, total body composition, and performance of normal daily living activities in middle-aged men. Methods. Thirty-seven healthy middle-aged male subjects participated in this study. Subjects were assigned to one of three groups: high-intensity (80% 1-RM) resistance training (RT80, age = 57.5 +/- 0.8, n = 13); low-intensity (20% 1-RM) resistance training with vascular restriction (VR-RT20, age = 59.9 +/- 1.0, n = 13); and control (CON, age = 57.0 +/- 1.1, n = 11). Subjects in both exercise groups performed three upper body (lat pulldown, shoulder press, and biceps curl at 80% 1-RM) and two lower body (leg press and knee extension) exercises either with (two sets of 15 repetitions and one set of 30 repetitions at 20% 1-RM) or without (three sets of 8 repetitions at 80% 1-RM) vascular restriction three times a week for 6 weeks. Following training, subjects were assessed for muscle strength and size, serum hormones (IGF-I, IGFBP-3, testosterone), skeletal muscle damage marker [creatine kinase (CK)], inflammatory marker [interleukin-6 (Il-6)], bone markers (bone alkaline phosphatase [BAP] and C-telopeptide of Type I collagen cross-links [CTX]), body composition (total fat mass, total lean mass, and percent fat), and daily living activities (chair rise, walking, and stair climb). Analysis of covariance (ANCOVA), two-way repeated measures analysis of variance (ANOVA), and one-way ANOVA were used to test for group differences and changes over time. Results. No significant group differences were detected in age, height, and weight at baseline. Following training, ANCOVA demonstrated that RT80 and VR-RT20 had significantly greater strength values in lat pulldown, biceps curl, and leg press 1-RM strength than CON, while no significant differences between exercise groups were detected. For leg extension 1-RM strength, ANCOVA also revealed that RT80 experienced significantly greater increases compared with VR-RT20 and CON. The VR-RT20 group had a significantly greater improvement in leg extension 1-RM strength compared with CON. Repeated measures ANOVA (group x time) showed a significant time and time x group interaction for shoulder press strength; however, the Bonferroni post-hoc analyses did not detect any significant group differences. Significant increases were determined in strength values for all 5 tested exercises over time for each exercise group throughout the training period. The RT80 and VR-RT20 groups had significantly greater strength increases in all upper body and leg press exercises compared with CON but, no group differences between exercise groups were determined for upper body and leg press exercises. However, the percentage changes in leg extension exercise for the RT80 group was significantly higher than both VR-RT20 and CON, while percentage changes in leg press exercise for the VR-RT20 group was significantly greater compared with CON. Two-way repeated measures ANOVA revealed a significant time effect for BAP and a trend for group x time interaction. There was a significant percentage changes in serum BAP concentrations, but the follow-up post-hoc tests did not determine any significant group differences. A significant main effect for time was detected in BAP to CTX ratio. Statistical analyses failed to detect significant group differences or percentage changes in serum IGF-I, IGFBP-3, testosterone, CTX, CK, IL-6, body composition and functional tests, however a trend for...