Lower-Load is More Effective Than Higher-Load Resistance Training in Increasing Muscle Mass in Young Women

ABSTRACTFranco, CMdC, Carneiro, MAdS, Alves, LTH, Júnior, GNdO, de Sousa, JdFR, and Orsatti, FL. Lower-load is more effective than higher-load resistance training in increasing muscle mass in young women. J Strength Cond Res 33(7S)S152–S158, 2019—This study was designed to investigate the impact of load (higher vs. lower) performed until or close to volitional fatigue on muscle strength (MS) and fat and bone-free lean mass (FBFM) in young women. To do this, 32 women performed resistance training (RT) in 1 of 2 conditionslower-load RT (LL; n = 14, age = 24.3 ± 4.8 years and body mass index [BMI] = 23.3 ± 2.8 kg·m) and higher-load RT (HL; n = 18, age = 23.0 ± 3.3 years and BMI = 22.4 ± 3.3 kg·m). Leg FBFM (DXA) and MS (1 repetition maximum—unilateral leg extension [LE]) were evaluated before and after 9 weeks (the first week was used for familiarization) of RT. Both groups performed 3 unilateral exercises (LE, leg curl, and leg press), 3 sets per exercise, 60–90 seconds of rest between sets, 2 days per week. In the LL group, the loads used in the exercises were the loads necessary to perform 30–35 repetitions in the first set. For the HL group, the loads used were the loads necessary to perform 8–10 repetitions in the first set. The LL group showed higher RT volume than the HL. Both groups showed leg muscle mass gains (p < 0.05). However, the LL group was better [p = 0.032 and effect size (eta = 0.14 [large]) than the HL group in leg FBFM gains (LL = 0.3 kg [IC 95%0.4 kg; 0.2 kg] and HL = 0.1 kg [IC 95%0.2 kg; 0.0 kg]). Both groups showed MS gains, without any difference between them (LL = 3.4 kg [IC 95%4.4 kg; 2.5 kg] and HL = 4.2 kg [IC 95%5.1 kg; 3.3 kg]; p = 0.239). Thus, lower-load RT is more effective than higher-load RT in increasing FBFM, but not MS in novice young women.