Abstract
BackgroundVariable resistance has been shown to induce greater total work and muscle activation when compared to constant resistance. However, little is known regarding the effects of chronic exposure to variable resistance training in comparison with constant resistance training. The aim of the present study was therefore to examine the effects of chain-loaded variable and constant gravity-dependent resistance training on resting hormonal and neuromuscular adaptations.MethodsYoung women were randomly assigned to variable resistance training (VRT; n = 12; age, 23.75 ± 3.64 years; and BMI, 26.80 ± 4.21 kg m−2), constant resistance training (CRT; n = 12; age, 23.58 ± 3.84 years; BMI, 25.25 ± 3.84 kg m−2), or control (Con; n = 12; age, 23.50 ± 2.93 years; BMI, 27.12 ± 12 kg m−2) groups. CRT performed 8-week total-body free-weight training three times per week with moderate-to-high intensity (65–80% 1RM; periodized). VRT was the same as CRT but included variable resistance via chains (15% of total load). Resting serum samples were taken before and after the 8-week intervention for GH, IGF-1, cortisol, myostatin, and follistatin analyses.ResultsBoth VRT and CRT groups displayed moderate-to-large significant increases in GH (197.1%; ES = 0.78 vs. 229.9%; ES = 1.55), IGF-1 (82.3%; ES = 1.87 vs. 66%; ES = 1.66), and follistatin (58.8%; ES = 0.80 vs. 49.15%; ES = 0.80) and decreases in cortisol (− 19.9%; ES = − 1.34 vs. − 17.1%; ES = − 1.05) and myostatin (− 26.9%; ES = − 0.78 vs. − 23.2%; ES = − 0.82). Also, VRT and CRT resulted in large significant increases in bench press (30.54%; ES = 1.45 vs. 25.08%; ES = 1.12) and squat (30.63%; ES = 1.28 vs. 24.81%; ES = 1.21) strength, with no differences between groups.ConclusionsImplementing chain-loaded VRT into a periodized resistance training program can be an effective alternative to constant loading during free-weight RT among untrained young women.
Highlights
Variable resistance has been shown to induce greater total work and muscle activation when compared to constant resistance
Hormonal measures After the 8-week training period, there were moderate and large significant increases in growth hormone (GH) levels for the variable Resistance training (RT) (VRT) (p = 0.014; Effect size (ES) = 0.78, 95% Confidence interval (CI) = 0.17 to 1.39; Δ of 197.1 ± 320.4%) and constant RT (CRT) (p = 0.003; ES = 1.55, 95% CI = 0.83 to 2.26; Δ of 229.9 ± 440.4%) groups, respectively (Fig. 2a, b)
Large significant increases in insulin-like growth factor-1 (IGF-1) were observed for the VRT (p = 0.001; ES = 1.87, 95% CI = 1.10 to 2.65; Δ of 82.3 ± 57.6%) and CRT (p = 0.001; ES = 1.66, 95% CI = 0.92 to 2.39; Δ of 66 ± 44.1%) groups
Summary
Variable resistance has been shown to induce greater total work and muscle activation when compared to constant resistance. Little is known regarding the effects of chronic exposure to variable resistance training in comparison with constant resistance training. The aim of the present study was to examine the effects of chain-loaded variable and constant gravity-dependent resistance training on resting hormonal and neuromuscular adaptations. Resistance training (RT) induces acute mechanical and physiological responses that play a role in chronic adaptations including muscular strength, hypertrophy, and performance. Other factors are at play, the acute responses to RT and subsequent tissue remodeling are primarily mediated via the neuroendocrine system [1]. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are some of the most studied, having a major role in promoting tissue anabolism [2]. Follistatin is a putative inhibitor of myostatin, which can contribute to elevated anabolic responses [3]
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