Muscle fatigue in response to low-load blood flow-restricted elbow-flexion exercise: are there any sex differences?

PURPOSE: This study aimed to determine whether men and women display a different magnitude of muscle fatigue in response to high-load (HL) and low-load blood flow-restricted (LLBFR) elbow-flexion exercise. We also explored to which extent both exercise protocols induce similar levels of muscle fatigue (i.e., torque decrement). METHODS: Sixty-two young participants (31 men and 31 women) performed dynamic elbow flexions at 20 and 75% of one-repetition maximum for LLBFR and HL exercise, respectively. Maximum voluntary isometric contractions were performed before and after exercise to quantify muscle fatigue. RESULTS: Men and women exhibited similar magnitude of relative torque decrement after both exercise protocols (p > 0.05). HL was more fatiguing (∆ torque output: 11.9 and 23 N.m in women and men, respectively) than LLBFR resistance exercise (∆ torque output: 8.3 and 15.4 N.m in women and men, respectively) in both sexes, but this was largely attenuated after controlling for the differences in volume load between protocols (p > 0.05). CONCLUSIONS: These data show that torque decrement in response to LLBFR and HL dynamic elbow-flexion exercise does not follow a sexually dimorphic pattern. Our data also indicate that, if performed in a multiple-set fashion and prescribed for a given volume load, elbow-flexion LLBFR exercise induces similar levels of fatigue as HL acute training. Importantly, this occurs similarly in both sexes.

Sexual Dimorphism in the Estimation of Upper-Limb Blood Flow Restriction in the Seated Position.

Borges, A, Teodósio, C, Matos, P, Mil-Homens, P, Pezarat-Correia, P, Fahs, C, and Mendonca, GV. Sexual dimorphism in the estimation of upper-limb blood flow restriction in the seated position. J Strength Cond Res 32(7): 2096-2102, 2018-Arterial occlusion pressure (AOP) is typically used to normalize blood flow restriction (BFR) during low-intensity BFR exercise. Despite strong evidence for sexual dimorphism in muscle blood flow, sex-related differences in AOP estimation remain a controversial topic. We aimed at determining whether the relationship of upper-limb AOP with arm circumference and systolic blood pressure (BP) differs between men and women resting in the seated position. Sixty-two healthy young participants (31 men: 21.7 ± 2.3; 31 women: 22.0 ± 2.0 years) were included in this study. Arm circumference, resting BP, and AOP were taken in the seated position. Multiple linear regression analysis was used to determine whether the relationship of AOP with arm circumference and resting BP differed between sexes. Prediction accuracy was assessed with the mean absolute percent error and Bland-Altman plots. Men had higher systolic BP and larger arm circumference than women (p < 0.05). Nevertheless, AOP was similar between sexes. Arm circumference, systolic BP, and sex were all significant predictors of AOP (p < 0.05), explaining 42% of its variance. The absolute percent error was similar in both sexes (men: -0.55 ± 7.12; women: -0.39 ± 6.31%, p > 0.05). Bland-Altman plots showed that the mean difference between actual and estimated AOP was nearly zero in both groups, with no systematic overestimation or underestimation. In conclusion, arm circumference, systolic BP, and sex are all significant predictors of upper-limb-seated AOP. Their measurement allows for the indirect estimation of BFR pressure within the context of exercise training.

Oxygen uptake efficiency slope during exercise in adults with Down syndrome.

BACKGROUND: Persons with Down syndrome (DS) have low aerobic exercise capacity. The present authors sought to compare the oxygen uptake efficiency slope (OUES) between adults with and without DS performing graded exercise testing (GXT) and to investigate its relationship with peak oxygen uptake (VO2peak ) in both groups of participants. METHOD: Twenty-three participants with DS and 24 non-disabled controls performed GXT with VO2 measurements. OUES was calculated from data of the first 75%, 90% and 100% GXT time. Multiple linear regression analyses were computed to explore associations between the independent (OUES and DS) and the dependent variables (VO2peak ). RESULTS: VO2peak , GXT time and OUES were lower in participants with DS (p < .05). OUES and DS explained 69.3% of the variance in VO2peak . CONCLUSIONS: Our findings show that OUES values are lower in persons with DS. Additionally, it was shown that OUES has predictive value for VO2peak estimations in DS.