Low-Load x High-Load Resistance Exercise: Greater Cell Swelling After a Training Session.

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.

Isokinetic strength of shoulder rotator muscles in powerlifters: correlation between isometric and concentric muscle actions.

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.

Hypopressive exercise in normotensive young women: A case series.

Hypopressive exercise (HE) has been contraindicated for people with cardiovascular disease because it involves isometric postures performed with low-pulmonary volume breath-holds, which are thought to increase blood pressure. The objective of this study was to analyze the hemodynamic responses to HE performed in the seated posture on systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) in normotensive females. Ten women (age = 31.2 ± 6.3 years) with previous experience in HE participated. Three sets of eight breathing cycles of HE breathing were completed. The HE breathing protocol consisted of three complete breathing cycles of controlled latero-costal inhalations and slow deep exhalations followed by a breath-hold and rib-cage expansion after every third exhalation. Measurements of SBP, DBP, MAP and HR were assessed at baseline, at the end of each set and at the end of minute 5, 10, 15 and 20 during the recovery period. The measurement of hemodynamic variables used a digital photoplethysmography device. Significant differences for SBP (baseline compared to SET2, p = 0.0182) and MAP (baseline compared to SET1, p = 0.0433; and SET2, p = 0.0072) were found. No significant differences were found in the recovery periods compared with baseline. Medium effect size for HR during REC5 (ES = 0.50) and REC10 (ES = 0.56) was observed. These findings indicate that HE in the seated posture performed by normotensive females leads to significant increases in SBP and MAP with no significant increase of HR and no hypotensive effect during recovery period. Our preliminary results should be supported by future randomized controlled trials.