Session ratings of perceived exertion (SRPE) provide a valid and reliable indicator of resistance exercise session intensity. However, there is a lack of studies on the effects of resistance exercise with blood flow restriction (BFR) on SRPE. Thus, the aim of this study is to compare the effects of resistance exercise at high intensity versus low intensity with BFR on internal training load measured by SRPE. Thirteen young (22.2 ± 3.8 years) resistance-trained men (training experience 3.2 ± 2.4 years) participated in the study protocol. After determining one maximum repetition (1-RM), the subjects were assigned to two groups in a counterbalanced design (i) high-intensity exercise (HIE, performed one training session at 80% of 1-RM) and (ii) low intensity with BFR (BFR, performed an exercise session at 50% of 1-RM with BFR). During each session, subjects performed three sets of unilateral elbow flexion leading to concentric failure with a 1-min rest interval between sets. A cuff around the arm, inflated at 110 mmHg, was used continuously for BFR. The SRPE was reported 30 min after the end of the session. The low intensity with BFR showed lower total work (197.13 ± 63.49 versus 300.92 ± 71.81 kg; P = 0.002) and higher SRPE (9 versus 6; P = 0.007) than high-intensity resistance exercise. The present results indicate that BFR is an important factor to increase internal training load. Future studies should investigate the physiological stress imposed by different training methods rather than just quantify the external training load such as intensity or volume.

Capsaicin (CAP) activates the transient receptor potential vanilloid 1 (TRPV1) channel on sensory neurons, improving ATP production, vascular function, fatigue resistance, and thus exercise performance. However, the underlying mechanisms of CAP-induced ergogenic effects and fatigue-resistance, remain elusive. To evaluate the potential anti-fatigue effects of CAP, 10 young healthy males performed constant-load cycling exercise time to exhaustion (TTE) trials (85% maximal work rate) after ingestion of placebo (PL; fiber) or CAP capsules in a blinded, counterbalanced, crossover design, while cardiorespiratory responses were monitored. Fatigue was assessed with the interpolated twitch technique, pre-post exercise, during isometric maximal voluntary contractions (MVC). No significant differences (p > 0.05) were detected in cardiorespiratory responses and self-reported fatigue (RPE scale) during the time trial or in TTE (375 ± 26 and 327 ± 36 s, respectively). CAP attenuated the reduction in potentiated twitch (PL: −52 ± 6 vs. CAP: −42 ± 11%, p = 0.037), and tended to attenuate the decline in maximal relaxation rate (PL: −47 ± 33 vs. CAP: −29 ± 68%, p = 0.057), but not maximal rate of force development, MVC, or voluntary muscle activation. Thus, CAP might attenuate neuromuscular fatigue through alterations in afferent signaling or neuromuscular relaxation kinetics, perhaps mediated via the sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) pumps, thereby increasing the rate of Ca2+ reuptake and relaxation.

The sympathicotonic effect of caffeine is strongly evidenced in the literature. However, the effects of caffeine or caffeine expectancy on the cardiac parasympathetic modulation remain obscure. Thus, the aim of this study was to investigate the effects of caffeine consumption and expectancy of caffeine consumption on the cardiac parasympathetic modulation under different stress conditions. Twenty-one physically active men (22.3 ± 2.9 years, 25.2 ± 2.7 kg/m 2 ) consumed ∼3 mg/kg of caffeine received as caffeine, caffeine as placebo, placebo as placebo and placebo as caffeine. Parasympathetic modulation was assessed by heart rate variability (HRV-Poincaré SD1 index) at supine and orthostatic positions, during a submaximal exercise (HRV threshold-HRV T ) and during each 60 seconds (s) within 300 s of post-exercise active recovery. A factorial ANOVA for repeated measures (p < 0.05) was used to assess the effect of caffeine, expectancy and resting time after caffeine intake on the HRV. No significant effect of caffeine or expectancy was observed on the SD1 value at supine or standing positions (p = 0.47-0.53; p = 0.57-0.31, respectively), despite an increase in this variable after resting periods in both positions (p < 0.001). During exercise, caffeine and expectancy do not alter the HRV T (p = 0.51-0.39). However, higher SD1 values were observed after caffeine administration from 60 to 300 s post-exercise recovery (p = 0.01-0.05) but not for the effects of expectancy (p = 0.19-0.94). We concluded that low doses of caffeine or expectancy do not alter the resting cardiac parasympathetic modulation or HRV T . However, caffeine, but not expectancy, increases parasympathetic reactivation after a submaximal exercise test in young men.

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Background Low endogenous testosterone has been associated with increased cardiovascular risk in men. Objectives To determine the prevalence of low serum testosterone level (TT) in a cohort of male US career firefighters and to examine its relation with left ventricular wall thickness (LVWT). Materials and Methods We conducted a cross‐sectional study among 341 career firefighters, (age: 37.5 ± 10.3 years; BMI: 28.9 ± 4.5 kg/m2), who underwent an occupational medical screening examination. TT quartiles were determined, and LVWT distribution among them was plotted. Then, TT values were categorized as low (<264 ng/dL), borderline (264‐399 ng/dL), reference range (400‐916 ng/dL), and high (>916 ng/dL). To further investigate the association of mildly decreased TT on LVWT, we divided the borderline group into borderline‐low (264‐319 ng/dL) and borderline‐high (320‐399 ng/dL) ranges. LVWT values were classified as low LVWT when <0.6 cm. A multivariate model was used to compare LVWT, age, BMI, systolic blood pressure (SBP), and HbA1c among groups by TT values. Results The prevalence of low TT was 10.6% and of borderline was 26.4%, while 58.7% had levels in the reference range. The low‐TT group was older and had higher BMI and SBP as compared to the reference group (P < .01). LVWT values were different among groups (P = .04) and significantly lower in firefighters with borderline‐low TT as compared to the reference group (P < .05). This finding also occurred within obese firefighters (P = .03). The borderline‐low group had a higher adjusted risk for a low LVWT as compared to the reference group [OR: 4.11 (95% CI: 1.79‐9.43)]. Discussion Our findings highlight the possible relationship between a mild reduction in testosterone levels (borderline) and lower LVWT. Conclusions A high prevalence of subnormal TT levels (low and borderline: 37%) was observed in this relatively homogeneous cohort of career firefighters. Mildly decreased TT levels and lower LVWT might represent a preclinical condition and a window of opportunity for cardiovascular preventive interventions in firefighters.

Objective: To compare health-related physical fitness (HRPF) in patients with severe adult growth hormone deficiency (AGHD) according to the deficiency onset phase, and to evaluate the effects of a six-months human growth hormone (rhGH) replacement therapy on HRPF, in a subgroup of patients. Methods: First arm: cross-sectional observational study at baseline of naive rhGH multiple pituitary hormonal deficiency (MPHD) hypopituitarism patients - adult-onset growth hormone deficiency (AO-GHD) versus child onset growth hormone deficiency (CO-GHD). Second arm: a 6-month intervention clinical trial in a selected group of a non-randomized, non-controlled cohort. HRPF was evaluated by measuring isokinetic and isometric torque stensor strength at the knee using an isokinetic dynamometer, handgrip strength and six-minute walk test. Body composition was assessed by DXA. Results: Patients who presented AO-GHD had higher BMI than CO-GHD (28.1±3.5 x 22.4±4.8; p=0.017), but body composition (lean body mass%:57.9±7.9 x 58.9±8.6;p=0.816/fatty body mass%:39.3±6.8 x 36.0±9.1;p=0.434), stensor peak torque/body weight at 60, 90 and 180deg/s (2.18±0.6 x 2.18±0.6; p=0.580/1.99±0.5 x 2.14±0.5;p=0.546/1.52±0.4 x 1.64±0.4;p=0.547), isometric torque/body weight at the knee (2.62±0.7 x 2.91±0.6;p=0.357) and six-minute walk test (570.2±76.0cm x 554.1±91.0cm;p= 0.703) did not differ between groups. Handgrip strength test also showed significant reduction in scores for age and gender in both groups of GHD patients. After six months of rhGH, no improvement in muscular strength tests was found. There was a significant worsening in the six-minute walk test (575.1±84cm x 545.4±90.6cm; p=0.033) despite the improvement in body composition (lean body mass%:59.7±8.6 x 63.6±11.1;p=0.005/fatty body mass%:35.7±9.2 x 32.9±10.0;p=0.003). Conclusion: Despite differences in BMI, there were no other differences in HRPF between AO-GHD and CO-GHD patients. The decrease of the six-minute walking test performance after rhGH replacement therapy supports the clinical evidence that the GH regulates bioenergetics in human skeletal muscle fibers. Although the treatment had a short period, GH might have stimulated the anaerobic and suppressed the aerobic energy system.

The purpose of this review was to examine in the current literature the advances made in terms of the effects of caffeine supplementation on maximum strength and its associated mechanisms since the publication of two important papers in 2010. Searches were carried out in the PubMed, Medline, Scielo and Web of Science databases for articles published after 2010. Sixteen studies were included based on inclusion and exclusion criteria. Five studies did not report changes in maximal voluntary strength (31.3%). Four of them used isometric muscle contractions, although this may not be a key factor because five other studies also used isometric contractions and reported ergogenic effects. Furthermore, these four studies evaluated small muscle groups and volunteers were not accustomed to consuming caffeine. Caffeine produced ergogenic effects in eleven of the sixteen studies analyzed (68.8%). None of the doses were clearly related to ergogenic effects; however, a dose of at least 3 mg/kg of caffeine is probably necessary. Caffeine ergogenicity was affected by various factors. There was a lack of standardized protocols and controls for intervening factors (e.g., circadian cycles and nutritional states), which could affect results. An ideal caffeine supplementation protocol that is useful for future research, athletes, and physical activity practitioners, has yet to be defined. A small advance made since 2010 involved a possible lack of gender difference; it would appear that caffeine supplementation affects men and women equally. Level of Evidence I; Systematic Review of Level I Studies.

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