Muscle Hypertrophy and Strength Adaptations to Systematically Varying Resistance Exercises

Abstract

We compared the effects of varied and constant resistance exercises on muscular adaptations in young women. Seventy young women (21.8 ± 3.4 yrs, 62.0 ± 12.3 kg, 162.3 ± 5.7 cm) were randomly divided into two groups: constant resistance exercises (CON-RE, n = 38) or varied resistance exercises (VAR-RE, n = 32). The resistance training (RT) was performed thrice a week over 10 weeks. CON-RE performed a 45º leg press and stiff-leg deadlift in every training session, while VAR-RE performed 45º leg press and stiff-leg deadlift in the first training session of the week, hack squat and prone leg curl in the second, and Smith machine squat and seated-leg curl in the third. Both groups performed two sets of 10–15 repetitions maximum per resistance exercise. We measured the muscle thickness of the thigh’s anterior, lateral, and posterior aspects by ultrasonography at different muscle sites (proximo-distal). Muscular strength was analyzed from the one-repetition maximum (1RM) tests in the 45° leg press and leg extension (non-trained exercise). The muscle thickness increased similarly in both groups for all muscles and sites (CON-RE: +7.8–17.7% vs. VAR-RE: +7.5–19.3%, p >.05). The 1RM increased similarly in both groups (CON-RE: +24.4–32.1% vs. VAR-RE: +29.0–30.1%, p >.05). Both RT routines resulted in virtually similar muscular strength gains and hypertrophy. Therefore, both strategies should be considered for the improvement of strength and muscle growth.