MAZZETTI, S. A., W. J. KRAEMER, J. S. VOLEK, N. D. DUNCAN, N. A. RATAMESS, A. L. GÓMEZ, R. U. NEWTON, K. HÄKKINEN, and S. J. FLECK. The influence of direct supervision of resistance training on strength performance. Med. Sci. Sports Exerc., Vol. 32, No. 6, pp. 1175-1184, 2000.
Purpose: The purpose of this study was to compare changes in maximal strength, power, and muscular endurance after 12 wk of periodized heavy-resistance training directly supervised by a personal trainer (SUP) versus unsupervised training (UNSUP).
Methods: Twenty moderately trained men aged 24.6 ± 1.0 yr (mean ± SE) were randomly assigned to either the SUP group (N = 10) or the UNSUP group (N = 8). Both groups performed identical linear periodized resistance training programs consisting of preparatory (10-12 repetitions maximum (RM)), hypertrophy (8 to 10-RM), strength (5 to 8-RM), and peaking phases (3 to 6-RM) using free-weight and variable-resistance machine exercises. Subjects were tested for maximal squat and bench press strength (1-RM), squat jump power output, bench press muscular endurance, and body composition at week 0 and after 12 wk of training.
Results: Mean training loads (kg per set) per week were significantly (P < 0.05) greater in the SUP group than the UNSUP group at weeks 7 through 11 for the squat, and weeks 3 and 7 through 12 for the bench press exercises. The rates of increase (slope) of squat and bench press kg per set were significantly greater in the SUP group. Maximal squat and bench press strength were significantly greater at week 12 in the SUP group. Squat and bench press 1-RM, and mean and peak power output increased significantly after training in both groups. Relative local muscular endurance (80% of 1-RM) was not compromised in either group despite significantly greater loads utilized in bench press muscular endurance testing after training. Body mass, fat mass, and fat-free mass increased significantly after training in the SUP group.
Conclusion: Directly supervised, heavy-resistance training in moderately trained men resulted in a greater rate of training load increase and magnitude which resulted in greater maximal strength gains compared with unsupervised training.
Different resistance training protocols have been shown to present a variety of exercise demands resulting in adaptations which are specific to the exercise program utilized (1,3,19,21-23,46,47). For example, multiple-set protocols that incorporate periodization and progressive overload have been shown to optimize improvements in maximal strength performance (4,26,38,39,44).
To date, the effects of direct supervision (i.e., one-on-one personal training) on resistance training adaptations have not been examined. Because many training studies have incorporated some level of supervision to ensure standardized training of all subjects (5,10,13,17,21,28-30), we hypothesized that in highly motivated moderately trained men, direct supervision of training sessions is important for maximal strength performance adaptations to periodized, heavy-resistance training.
Previous studies that have utilized individually supervised training in moderately trained subjects have shown improvements in leg press strength performance of 26 and 30% after 19 and 12 wk of resistance training, respectively (5,21). Strength performance adaptations resulting from other relevant studies, where the level of supervision was either less direct or not specified were as follows: 28% and 12% improvements in 1-repetition maximum (RM) squat and bench press strength, respectively, after 12 wk of linear periodized training; 22% improvement in 1-RM squat after 14 wk of multiple-set varied resistance training; and ∼30 and ∼25% improvements in relative (i.e., 1-RM/body weight) squat and bench press strength, respectively, after 16 wk of linear periodized training (2,17,44). Due to variations in the strength testing protocols, experimental periods, training protocols, and pretraining status of the subjects in these studies, it is difficult to formulate any concrete conclusions describing the influence of supervision of resistance training on strength performance adaptations. The primary purpose of this investigation, therefore, was to compare the changes in maximal strength after directly supervised versus unsupervised, periodized heavy-resistance training.