title: Impact of high versus low fixed loads and non-linear training loads on muscle hypertrophy, strength and force development.
abstract: BACKGROUND
  In this study, we investigated the effects of resistance training protocols with different loads on muscle hypertrophy and strength.
  
  
  METHODS
  Twenty-one participants were randomly assigned to 1 of 3 (n = 7 for each) resistance training (RT) protocols to failure: High load 80 % 1RM (8-12 repetitions) (H group), low load 30 % 1RM (30-40 repetitions) (L group) and a mixed RT protocol (M group) in which the participants switch from H to L every 2 weeks. RT consisted of three sets of unilateral preacher curls performed with the left arm 3 times/week with 90 s rest intervals between sets. The right arm served as control. Maximum voluntary contraction (MVC) of the elbow flexors (elbow angle: 90°) and rate of force development (RFD, 0-50, 50-100, 100-200 and 200-300 ms) were measured. Cross-sectional area (CSA) of the elbow flexors was measured via magnetic resonance imaging (MRI). All measurements were conducted before and after the 8 weeks of RT (72-96 h after the last RT). Statistical evaluations were performed with two-way repeated measures (time × group).
  
  
  RESULTS
  After 8 weeks of 3 weekly RT sessions, significant increases in the left elbow flexor CSA [H: 9.1 ± 6.4 % (p = 0.001), L: 9.4 ± 5.3 % (p = 0.001), M: 8.8 ± 7.9 % (p = 0.001)] have been observed in each group, without significant differences between groups. Significant changes in elbow flexor isometric MVC have been observed in the H group (26.5 ± 27.0 %, p = 0.028), while no significant changes have been observed in the M (11.8 ± 36.4 %, p = 0.26) and L (4.6 ± 23.9 %, p = 0.65) groups. RFD significantly increased during the 50-100 ms phase in the H group only (p = 0.049).
  
  
  CONCLUSIONS
  We conclude that, as long as RT is conducted to failure, training load might not affect muscle hypertrophy in young men. Nevertheless, strength and RFD changes seem to be load-dependent. Furthermore, a non-linear RT protocol switching loads every 2 weeks might not lead to superior muscle hypertrophy nor strength gains in comparison with straight RT protocols.
authors.affiliation: Graduate Schools of Health and Sport Science, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Julius
authors.initials: J
authors.lastname: Fink
authors.affiliation: Department of Training Science, Nippon Sport Science University, 1221-1, Kamoshidacho, Aoba-ku, Yokohama, 227-0033 Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Kikuchi
authors.affiliation: Graduate Schools of Health and Sport Science, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Shou
authors.initials: S
authors.lastname: Yoshida
authors.affiliation: Graduate Schools of Health and Sport Science, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Terada
authors.affiliation: Graduate Schools of Health and Sport Science, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakazato
keywords: Cross-sectional area; Maximum voluntary contraction; Periodized training