The present study aims to investigate effects of caffeine ingestion and sex difference on muscle performance, delayed-onset muscle soreness (DOMS), and various biomarkers under exercise-induced muscle damage (EIMD). Twenty (10 male and 10 female) healthy elite college athletes were recruited. Participants ingested either caffeine (6 mg/kg) or a placebo in a randomized, double-blind, and counterbalanced fashion at 24 and 48 h following EIMD. Muscle performance, DOMS, and blood samples were taken an hour before and an hour after supplementation. Caffeine ingestion restored impaired maximal voluntary isometric contractions (MVIC: 10.2%; MVICpost: 7.2%, both P < 0.05) during EIMD across both sexes. Following caffeine ingestion during MVIC, while affected by EIMD, an interaction was found in DOMS and serum K+ (both P < 0.05), with males showing greater attenuation (21.5 and 16.9%, respectively) compared with females (4.6 and 1.3%, respectively). DOMS demonstrated an inverse correlation with MVIC after caffeine ingestion both overall and among male athletes ( r = −0.34 and −0.54, respectively; P < 0.05) but not among female athletes ( r = −0.11; P > 0.05) under EIMD. In addition, caffeine ingestion increased postexercise serum glucose and lactate concentrations across both sexes (both P < 0.05). This is the first study to show that male athletes, compared with female athletes, experience a greater reduction in DOMS during enhanced MVIC when caffeine was consumed, suggesting men might receive greater ergogenic effects from caffeine when affected by EIMD. Furthermore, caffeine ingestion was able to restore impaired muscle power among elite collegiate athletes across both sexes. NEW & NOTEWORTHY Exercise-induced muscle damage (EIMD) reduces anaerobic/aerobic performance and increases delayed-onset muscle soreness (DOMS) during exercise. We show that acute caffeine supplementation at a dosage of 6 mg/kg seems to facilitate recovery of anaerobic muscle power and attenuate DOMS after EIMD across both sexes. Furthermore, male athletes, compared with female athletes, when caffeine was prescribed, experience a greater reduction in DOMS with better restoration of impaired maximal voluntary isometric contractions. This suggests that male athletes might benefit from the ergogenic effect of acute caffeine supplementation after the onset of EIMD.

The primary purpose of this study was to investigate the effects of gender difference and caffeine supplementation to maximal voluntary isometric contractions (MVIC) and submaximal voluntary isometric contractions (T(lim)). 10 male (age: 20.10 ± 2.18 years, BMI: 22.23±1.96 kg/m(2)) and 10 female (age: 19.90±0.99 years, BMI: 21.76±2.65 kg/m(2)) elite collegiate athletes were recruited. Subjects ingested caffeine (6 mg/kg) or a placebo in a randomized, double-blind, placebo-control, and counter-balanced fashion. MVIC and T(lim) were measured after supplementations. T(lim) result was calculated based on the time to exhaustion of isometric contraction with 50% MVIC. Fatigue index (FI%) referred to the MVIC tested 20 s after the cessation of T(lim) test, and was indexed by the percentage of MVIC decline. No significant interaction effect was found between the gender factor and the supplementation factor for all dependent variables. Compared to the placebo, caffeine supplementation significantly increased MVIC (5.9%) and T(lim) (15.5%) (p<0.05) whereas it had no significant effect on FI%. This study demonstrates that caffeine supplementation at a 6 mg/kg dosage facilitates performances in MVIC and T(lim). The ergogenic effect of caffeine on muscle power and muscle endurance does not show a gender bias.

The aim of this study was to determine the effects of short-term resistance training combined with systemic hypoxia on muscular performance and body composition. Eighteen resistance-untrained men (21.3 ± 2.0 years, 172.7 ± 5.5 cm, 67.3 ± 9.7 kg) were matched and assigned to 2 experimental groups: performing 6 weeks of squat exercise training under normobaric hypoxia (H, FiO2 = 15%) or normoxia (N). In both groups, subjects performed 3 weekly sessions (a total of 18 sessions) of 3 sets of back squat at 10-repetition maximum with 2 minutes of rest between sets. Dynamic, isometric, and isokinetic leg strength and body composition were measured under normoxia before and after resistance training. Squat 1 repetition maximum (1RM) improved significantly (p ≤ 0.05) after resistance training in both H and N groups (88.9 ± 16.9 to 109.4 ± 17.0 kg and 90.0 ± 12.2 to 105.6 ± 13.3 kg, respectively). However, there were no changes in maximal isometric and isokinetic leg strength, lean body mass, and fat mass after the resistance training in both groups. In addition, no significant differences were observed between H and N groups in squat 1RM, maximal isometric and isokinetic leg strength, and body composition. The major findings of this study suggest that short-term resistance training performed under normobaric hypoxia has no additive beneficial effect on muscular performance and body composition. In practical terms, our data suggest that the use of systemic hypoxia during short-term resistance training is not a viable method to further enhance muscular performance and body composition in previously resistance-untrained men.

BackgroundMuscle damage induced by unaccustomed or eccentric exercise results in delayed onset vascular stiffening. We tested the hypothesis that a 7-day supplementation of panax ginseng and salvia miltiorrhiza prior to an acute eccentric exercise could attenuate arterial stiffening.MethodsBy using a double-blind study placebo-controlled randomized design, subjects were randomly assigned to either the Chinese herb (N = 12) or the placebo group (N = 11) and performed a downhill running (eccentric exercise) trial and a control (seated rest) trial.ResultsMuscle soreness increased 1–2 days after exercise similarly in both groups, whereas the herb group demonstrated a faster recovery on active range of motion. Plasma creatine kinase concentration increased significantly at 24 h in both groups but the magnitude of increase was attenuated in the herb group. Arterial stiffness as measured by carotid-femoral pulse wave velocity increased significantly at 24 h in the placebo group but such increase was absent in the herb group. Flow-mediated dilation did not change in either group. Plasma concentrations of CRP and IL-6 increased in the placebo group but no such increases were observed in the herb group. Changes in arterial stiffness induced by eccentric exercise were associated with the corresponding changes in IL-6 (r = 0.46, P < 0.05).ConclusionsA short-term Chinese herb supplementation of panax ginseng and salvia miltiorrhiza ameliorated the delayed onset vascular stiffening induced by acute downhill running exercise.Trial registrationClinicalTrials.gov: NCT02007304. Registered Dec. 5, 2013)

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