EFFECT OF TRAINING ON THE RELATIONSHIP BETWEEN MAXIMAL AND SUBMAXIMAL STRENGTH

The purpose of this study was to evaluate the validity of a dynamic seven to 10 repetition maximum (7-10 RM) test to estimate maximal knee extension strength (1-RM) in untrained and trained subjects. Thirty-three men and 25 women (25 +/- 5 yr) were randomly assigned to a group that trained two or three times. wk-1 for 18 wk (N = 47) or a control group (N = 11). Training included one set of 7-10 repetitions to volitional fatigue on a Nautilus(TM) knee extension machine. Prior to (T1) and after training (T2) dynamic strength was evaluated by 1-RM and 7-10 RM tests. The 7-10 RM test consisted of one set of variable resistance knee extension exercise performed to volitional fatigue with a weight that allowed 7-10 repetitions. The training group improved their 1-RM and 7-10 RM strength (by 31.7 and 51.4%, respectively) (P less-than-or-equal-to 0.01) while the control group did not change. Training increased relative 7-10 RM strength (68.4% of 1-RM at T1 and 79.1% of 1-RM at T2) (P less-than-or-equal-to 0.01). The relationship between the 7-10 RM weight and 1-RM at T1 was linear: 1-RM = 1.554 (7-10 RM weight) - 5.181; R2 = 0.89; SEE = 9.3 kg. Application of this equation following training resulted in a systematic overprediction (p less-than-or-equal-to 0.01) of 1-RM (21.2 kg) in trained subjects. Therefore, a second linear equation was developed to predict 1-RM in trained subjects: 1-RM = 1.172 (7-10 RM weight) + 7.704; R2 = 0.91; SEE= 9.9 kg. Our results indicate that a test consisting of 7-10 repetitions performed to exhaustion can accurately predict 1-RM knee extension strength. However, resistance training alters the relationship between maximal and submaximal strength, and thus the level of training is an important consideration when estimating 1-RM strength from a multiple repetition test performed to volitional fatigue.