Comparison of muscle force exertion and electromyographic activity level during manual resistance exercise between experts and non-experts in resistance training

Background & Aim: Manual resistance training (MRT) is one form of resistance training (RT). MRT has some unique merits, such as the ability to apply a sufficient load in both the concentric and eccentric muscle activity phases. On the other hand, there is a possibility that sufficient muscle force cannot be exerted in some cases because muscle force exertion depends on the trainee's effort. It would be difficult for trainees without prior RT experience to exert sufficient force during MRT. In this study, we investigated the effect of RT experience on muscle force exertion patterns during MRT. Methods: Six healthy men with more than 2 years of RT experience (trained group) and 6 healthy men who had no RT experience (untrained group) performed dominant arm cable elbow flexion exercise. They performed 8 repetitions of manual resistance exercise (MR) with maximum voluntary force exertion throughout all repetitions and 8RM isotonic resistance exercise (ISO), which is a popular RT method. Their elbow flexion muscle exertion force and biceps brachii electromyogram (EMG) signals were measured during exercise. Results: In the trained group, the muscle exertion force during MR in the first 2 repetitions was significantly higher (142±11%: vs ISO), and that in the last 2 repetitions tended to be higher (109±13%) than that in ISO. In the untrained group, the muscle exertion force during MR in the first 2 repetitions was significantly higher (119±19%), and that in the last 2 repetitions was significantly lower (87%±14%) than that in ISO. Compared to those in ISO, the muscle exertion forces during MR in both the first 2 and the last 2 repetitions were significantly higher in the trained group than in the untrained group. There were no significant differences in electromyographic activity levels between the trained and untrained groups, or between MR and ISO, although some trends similar to those for the muscle exertion force were evident. Conclusion: Subjects with no prior RT experience exert a lower muscle force in MR than subjects with RT experience. Prior RT experience is suggested to affect the degree of muscle exertion force in MR.