The ergogenic effect of caffeine and its mechanism of action on short-term, high-intensity exercise are controversial. One proposed mechanism is caffeine's stimulatory effect on the central nervous system and thus, motor-unit excitation. The latter is non-invasively determined from surface electromyographic signal (EMG) frequency measures. The purpose of this study was to determine if power output and surface EMG frequency variables during high-intensity cycling were altered following caffeine ingestion. Eighteen recreationally active college males (mean +/- SD age, 21.5 +/- 1.8 y; height, 181.8 +/- 0.5 cm; body mass, 84.7 +/- 11.4 kg) performed the Wingate test (WG) after ingestion of gelatin capsules containing either placebo (PL; dextrose) or caffeine (CAFF; 5 mg/kg body mass). The trials were separated by 1 week and subjects were asked to withdraw from all caffeine-containing products for 48 h before each trial. From the resulting power-time records, peak power (PP; highest power output in 5 s), minimum power (MP; lowest power output in 5 s), and the percent decline in power (Pd) were calculated. Surface EMG records of the right vastus lateralis (VL) and the gastrocnemius (GA) muscles corresponding to the PP and MP periods were collected and used to determine the integrated electromyogram (IEMG), the mean (MNPF), and the median (MDPF) of the signal's power spectrum. A 2-way repeated measures analysis of variance (ANOVA) (treatment x time) was conducted to determine the effect of caffeine on these variables across levels of time. Caffeine ingestion had no effect on PP (PL, 1049 +/- 192 W; CAFF, 1098 +/- 198 W), MP (PL, 762 +/- 104 W; CAFF, 802 +/- 124 W), or the Pd (PL, 47% +/- 8.9%; CAFF, 48.2% +/- 7.3%) compared with the placebo. For both muscles, MNPF and MDPF diminished significantly (p < 0.001) across time and to a similar degree in both the CAFF and PL trials. Regardless of muscle, CAFF had no effect on the percent change in IEMG from the first 5 s to the last 5 s. For both treatments, the GA displayed a significantly (p < 0.05) greater pre vs. post percent decline in the EMG signal amplitude compared with the VL. These results indicate that caffeine does not impact power output during a 30 s high-intensity cycling bout. Furthermore, these data suggest that caffeine does not impact the neuromuscular drive as indicated by the similar IEMG scores between treatments. Similarly, caffeine does not seem to impact the frequency content of the surface EMG signal and thus the nature of recruited motor units before and after the expression of fatigue. The lack of decline in the IEMG in the VL despite the decline in power output over the course of the WG suggests a peripheral as opposed to a neural mechanism of fatigue in this muscle. The significant difference in the pre vs. post percent decline in the GA IEMG score further supports this notion. The pre vs. post decline in the IEMG noted in the GA may suggest a fatigue-triggered change in pedaling mechanics that may promote dominance of knee extensors with less re...

No previous study has investigated the applications of isolated cannabidiol (CBD) as a recovery aid in untrained human subjects after a bout of exercise-induced muscle damage. Purpose: This study aimed to investigate the effect of CBD oil on perceived muscle soreness, inflammation, and strength performance after eccentric exercise (ECC) of the elbow flexors. Methods: Thirteen untrained men (mean ± SD age, 21.85 ± 2.73 yr) performed 6 sets of 10 maximal ECC isokinetic muscle actions of the elbow flexors as part of a double-blind crossover design. Noninvasive (perceived soreness, arm circumference, hanging joint angle (JA), and peak torque (PT)) measures were taken before and after ECC, and 24, 48, and 72 h after ECC. All subjects completed both the supplement (CBD: 150 mg POST, 24 h, 48 h) and placebo (PLC: POST, 24 h, 48 h) condition separated by 2 wk. Four separate two-way repeated-measures ANOVA (condition [CBD vs PLC] Â time [PRE vs POST vs 24 h vs 48 h vs 72 h]) were used to analyze perceived soreness, arm circumference, JA, and PT. One-way repeated-measures ANOVA were used to decompose significant interactions and main effects. Results: There was no condition-time interaction or main effect of condition (P > 0.05) for perceived soreness, arm circumference, JA, or PT. There were main effects for time for perceived soreness (P = 0.000, η p 2 = 0.71) and JA (P = 0.006, η p 2 = 0.35). Conclusions:The current dose of 150 mg CBD oil at POST, 24 h, and 48 h had no effect on noninvasive markers of muscle damage in the upper extremity. At the current dose and schedule, CBD oil may not be beneficial for untrained men as a recovery aid after exercise-induced muscle damage.

CrossFit is a physically and metabolically-demanding training mode increasing in popularity among recreational athletes. Presently, however, scarce evidence is available documenting its energetic profile. This study investigated the metabolic characteristics of a CrossFit training bout as measured by expired gases and blood lactate. Eleven females and 7 males completed a 12-minute CrossFit bout on two occasions separated by three days. During both experimental sessions (Pt1, Pt2), subjects performed as many rounds as possible (AMRAP) within the timed workout which consisted of consisted of 12 box jumps (30" for males, 20" for females), 6 thrusters (24 kg for males, 16 kg for females), and 6 bar-facing burpees in sequence. Oxygen consumption (VO2), respiratory exchange ratio (RER), blood lactate (BL), and repetitions completed were measured during both experimental sessions. The average VO2 and RER of both bouts (Pt1 and Pt2) was 37.0 ± 4.8 ml/kg/min and 1.04 ± 0.1, respectively. Average BL significantly increased above pre-exercise concentrations (3.0 ± 1.3 mmol/L) at 4 min (10.1 ± 3.2 mmol/L; p < 0.01), 8 min (12.3 ± 3.5 mmol/L; p < 0.01), and immediately post at 12 min (12.6 ± 3.9 mmol/L; p < 0.01). Repetitions completed in Pt2 (140.2 ± 25.9) were significantly different to repetitions completed in Pt1 (131.2 ± 27.2) (p = 0.023). Average repetitions completed in Pt1 and Pt 2 was 135.7 ± 26.6. These data suggest that CrossFit is a metabolicallydemanding conditioning method that relies heavily on both aerobic and anaerobic energy production and may represent an alternative to traditional methods of exercise to improve fitness and longevity.

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Verification tests to confirm graded exercise test (GXT) V˙O2max are growing in popularity, but the validity and reliability of such testing in the heat remains unknown. Purpose This study aimed to evaluate the validity and reliability of a verification test to confirm GXT V˙O2max in a hot environment. Methods Twelve recreationally trained cyclists completed a two-test protocol that included a GXT progressing 20 W·min−1 followed by a biphasic supramaximal-load verification test (1 min at 60% increasing to 110% maximal GXT wattage until failure) in a hot environment (39°C, 32% relative humidity). Rest between tests occurred in a thermoneutral room and was anchored to the duration required for gastrointestinal temperature to return to baseline. Results Mean verification test V˙O2max (51.3 ± 8.8 mL·kg−1·min−1) was lower than GXT (55.9 ± 7.6 mL·kg−1·min−1, P = 0.02). Verification tests confirmed GXT V˙O2max in 92% of participants using individual analysis thresholds. Bland–Altman analysis revealed a sizable mean bias (−4.6 ± 4.9 mL·kg−1·min−1) with wide 95% limits of agreement (−14.0 to 5.0 mL·kg−1·min−1) across a range of V˙O2max values. The high coefficient of variation (9.6%) and typical error (±3.48 mL·kg−1·min−1) indicate potential issues of test–retest reliability in the heat. Conclusions Verification testing in a hot condition confirmed GXT V˙O2max in virtually all participants, indicating robust utility. To enhance test–retest reliability in this environment, protocol recommendations for work rate and recovery between tests are provided.