RESUMO
Cell swelling caused by resistance training is proposed to provide an anabolic stimulus for muscle growth and it is believed that these effects are heightened with the use of low loads. The purpose of this study was to compare the acute effects of two volume-equated resistance training (RT) protocols, low-load (LL) versus high-load (HL), on elbow flexor muscles thickness, arm circumference, and blood lactate concentration in well-trained individuals. Eight resistance-trained males performed the following two RT protocols involving unilateral elbow flexion of the dominant arm: i) LL, four sets with 50% 1 repetition-maximum [1 RM] and ii) HL, ten sets with 85% 1 RM until failure, and equated volume. Pre- and post-session measurements included muscle thickness of the elbow flexors (biceps brachii and brachialis), upper arm circumference, and blood lactate concentration. Significant pre- to post-session increases were found in both protocols for muscle thickness (F (1, 28) = 11.74, p = 0.0019), and blood lactate (F (1, 28) = 35.55, p < 0.0001); no statistically significant differences were observed between conditions, however, the magnitude of increases favored LL. Significant between-condition differences favoring LL were observed for total repetitions (p = 0.007), time under tension (p = 0.007), and training density (p = 0.007). These results suggest that LL training promotes superior post-session increases in muscle thickness, indicating that RT protocols with longer times under tension and densities are beneficial when the goal is to promote acute cell swelling.
RESUMO
BACKGROUND: Isokinetic strength has been useful to assess muscle function related to sports and prevent injuries. The present study measured the isokinetic isometric and concentric shoulder rotators strength, agonist/antagonist ratio, and examined the relationships between isometric and concentric peak torque, and agonist/antagonist ratio in powerlifters compared to a control group. METHODS: The participants were divided into two groups: powerlifters group (N.=14) and physically active group (N.=9). Participants' were evaluated on isokinetic dynamometer for isometric, and concentric (two velocities, 60°/s and 180°/s) strength of shoulder external (ER) internal rotation (IR). Isometric contractions lasted 10 seconds, and concentric modes were 5 repetitions. RESULTS: Bilateral significant differences, between dominant and non-dominant side, were found in ER peak torque at isometric mode in powerlifters group (P=0.021). Powerlifters showed higher IR peak torque at isometric mode in dominant (P=0.040) and non-dominant side (P=0.014) than physically active group. Pearson correlations between isometric peak torque and concentric velocities ranged between 0.49 and 0.89 for powerlifters group, and between 0.73 and 0.93 for physically active group. For agonist/antagonist ratio, pearson correlation ranged between 0.47 and 0.83 for powerlifters group, and between 0.48 and 0.86 for physically active group. CONCLUSIONS: The bilateral differences in ER movement at isometric mode in powerlifters suggest that exercises for shoulder rotators must be included on training for joint safety and balance between sides despite isometric shoulder rotators strength in powerlifters was higher than physically active individuals. Results presented positive correlation between both muscle actions, isometric and concentric, in peak torque and agonist/antagonist ratio.