Men exhibit greater values of reactive hyperemia than women even when controlling for the magnitude of desaturation during transient ischemia. Factors other than the ischemic vasodilatory stimulus, such as skeletal muscle mass and quality, likely provoke the commonly reported sex differences in reactive hyperemia measured by near-infrared spectroscopy.

Hill, EC, Housh, TJ, Smith, CM, Schmidt, RJ, and Johnson, GO. Gender- and muscle-specific responses during fatiguing exercise. J Strength Cond Res 32(5): 1471–1478, 2018—The purpose of the present investigation was to examine potential gender-related differences in electromyographic (EMG) and mechanomyographic (MMG) responses during submaximal, concentric, isokinetic, forearm flexion muscle contractions. Twelve men and 12 women performed concentric peak torque trials before (pretest) and after (posttest) a fatiguing exercise bout that consisted of 50 submaximal (65% of concentric peak torque), concentric, isokinetic (60°·s⁻¹), forearm flexion muscle contractions. Surface EMG and MMG signals were simultaneously recorded from the biceps brachii and brachioradialis muscles. There was a gender-related difference in the decline in absolute concentric peak torque for the men (23.8%) vs. women (18.5%) that was eliminated when covaried for differences in pretest concentric peak torque values. During the fatiguing exercise bout, EMG amplitude(AMP) increased and EMG mean power frequency (MPF) decreased for both genders and muscles. There were, however, muscle- and gender-specific increases, decreases, and no changes for MMG AMP and MMG MPF. The gender-related difference for the posttest decline in concentric peak torque was associated with differences in muscle strength which may have resulted in greater blood flow occlusion in the men than the women. The muscles with the most pronounced fatigue-induced neuromuscular responses were the biceps brachii in men and the brachioradialis in women. These findings may be related to gender differences in the usage patterns of synergistic muscles during a fatiguing task.

The purpose of this study was to compare the composite, inter-individual, and intra-individual differences in the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during fatiguing, maximal, bilateral, and isokinetic leg extension muscle actions. Thirteen recreationally active men (age = 21.7 ± 2.6 years; body mass = 79.8 ± 11.5 kg; height = 174.2 ± 12.7 cm) performed maximal, bilateral leg extensions at 180°·s⁻¹ until the torque values dropped to 50% of peak torque for two consecutive repetitions. The EMG and MMG signals from the vastus lateralis (VL) muscles of both limbs were recorded. Four 2(Leg) × 19(time) repeated measures ANOVAs were conducted to examine mean differences for EMG AMP, EMG MPF, MMG AMP, and MMG MPF between limbs, and polynomial regression analyses were performed to identify the patterns of neuromuscular responses. The results indicated no significant differences between limbs for EMG AMP (p = 0.44), EMG MPF (p = 0.33), MMG AMP (p = 0.89), or MMG MPF (p = 0.52). Polynomial regression analyses demonstrated substantial inter-individual variability. Inferences made regarding the patterns of neuromuscular responses to fatiguing and bilateral muscle actions should be considered on a subject-by-subject basis.

Shilajit is a safe, fluvic mineral complex exudate that is common to Ayurvedic medicine and is composed of fulvic acids, dibenzo-α-pyrones, proteins, and minerals. The purpose of this study was to examine the effects of 8 weeks of Shilajit supplementation at 250 mg·d− 1 (low dose) and 500 mg·d− 1 (high dose) versus placebo on maximal voluntary isometric contraction (MVIC) strength, concentric peak torque, fatigue-induced percent decline in strength, and serum hydroxyproline (HYP). Sixty-three recreationally-active men ( $$ \overline{X} $$ ± SD: 21.2 ± 2.4 yr.; 179.8 ± 6.3 cm; 83.1 ± 12.7 kg) volunteered to participate in this study. The subjects were randomly assigned to the high dose, low dose, or placebo group (each group: n = 21). During pre-supplementation testing, the subjects performed 2 pretest MVICs, 2 sets of 50 maximal, bilateral, concentric isokinetic leg extensions at 180°·s− 1 separated by 2-min of rest, and 2 posttest MVICs. Following 8 weeks of supplementation, the subjects repeated the pre-supplementation testing procedures. In addition, the groups were dichotomized at the 50th percentile based on pre-supplementation MVIC and baseline HYP. Mixed model ANOVAs and ANCOVAs were used to statistically analyze the dependent variables for the total groups (n = 21 per group) as well as dichotomized groups. For the upper 50th percentile group, the post-supplementation adjusted mean percent decline in MVIC was significantly less for the high dose group (8.9 ± 2.3%) than the low dose (17.0 ± 2.4%; p = 0.022) and placebo (16.0 ± 2.4%; p = 0.044) groups. There was no significant (p = 0.774) difference, however, between the low dose and placebo groups. In addition, for the upper 50th percentile group, the adjusted mean post-supplementation baseline HYP for the high dose group (1.5 ± 0.3 μg·mL− 1) was significantly less than both the low dose (2.4 ± 0.3 μg·mL− 1; p = 0.034) and placebo (2.4 ± 0.3 μg·mL− 1, p = 0.024) groups. The results of the present study demonstrated that 8 weeks of PrimaVie® Shilajit supplementation at 500 mg·d− 1 promoted the retention of maximal muscular strength following the fatiguing protocol and decreased baseline HYP. Thus, PrimaVie® Shilajit supplementation at 500 mg·d− 1 elicited favorable muscle and connective tissue adaptations.