Menthol alleviates post-race elevations in muscle soreness and metabolic and respiratory stress during running.

PURPOSE: We evaluated (1) whether participating in middle- and long-distance running races augments muscle soreness, oxygen cost, respiration, and exercise exertion during subsequent running, and (2) if post-race menthol application alleviates these responses in long-distance runners. METHODS: Eleven long-distance runners completed a 1500-m race on day 1 and a 3000-m race on day 2. On day 3 (post-race day), either a 4% menthol solution (Post-race menthol) or a placebo solution (Post-race placebo) serving as a vehicle control, was applied to their lower leg skin, and their perceptual and physiological responses were evaluated. The identical assessment with the placebo solution was also conducted without race participation (No-race placebo). RESULTS: The integrated muscle soreness index increased in the Post-race placebo compared to the No-race placebo (P < 0.001), but this response was absent in the Post-race menthol (P = 0.058). Oxygen uptake during treadmill running tended to be higher (4.3%) in the Post-race placebo vs. No-race placebo (P = 0.074). Oxygen uptake was 5.4% lower in the Post-race menthol compared to the Post-race placebo (P = 0.018). Minute ventilation during treadmill running was 6.7-7.6% higher in the Post-race placebo compared to No-race placebo, whereas it was 6.6-9.0% lower in the Post-race menthol vs. Post-race placebo (all P ≤ 0.001). The rate of perceived exertion was 7.0% lower in the Post-race menthol vs. Post-race placebo (P = 0.007). CONCLUSIONS: Middle- and long-distance races can subsequently elevate muscle soreness and induce respiratory and metabolic stress, but post-race menthol application to the lower legs can mitigate these responses and reduce exercise exertion in long-distance runners.

Sodium bicarbonate reduces ventilation without altering core temperature threshold or sensitivity of hyperthermia-induced hyperventilation in exercising humans.

Hyperthermia stimulates ventilation (hyperthermia-induced hyperventilation). In exercising humans, once the core temperature reaches ∼37°C, minute ventilation (V̇e) increases linearly with rising core temperature, and the slope of the relation between V̇e and core temperature reflects the sensitivity of the response. We previously reported that sodium bicarbonate ingestion reduces V̇e during prolonged exercise in the heat without affecting the sensitivity of hyperthermia-induced hyperventilation. Here, we hypothesized that reductions in V̇e associated with sodium bicarbonate ingestion reflect elevation of the core temperature threshold for hyperthermia-induced hyperventilation. Thirteen healthy young males ingested sodium bicarbonate (0.3 g/kg body wt) (NaHCO3 trial) or sodium chloride (0.208 g/kg body wt) (NaCl trial), after which they performed a cycle exercise at 50% of peak oxygen uptake in the heat (35°C and 50% relative humidity) following a pre-cooling. The pre-cooling enabled detection of an esophageal temperature (Tes: an index of core temperature) threshold for hyperthermia-induced hyperventilation. The Tes thresholds for increases in V̇e were similar between the two trials (P = 0.514). The slopes relating V̇E to Tes also did not differ between trials (P = 0.131). However, V̇e was lower in the NaHCO3 than in the NaCl trial in the range of Tes = 36.8-38.4°C (P = 0.007, main effect of trial). These results suggest that sodium bicarbonate ingestion does not alter the core temperature threshold or sensitivity of hyperthermia-induced hyperventilation during prolonged exercise in the heat; instead, it downshifts the exercise hyperpnea.

Effects of High-Intensity Exercise Repetition Number During Warm-up on Physiological Responses, Perceptions, Readiness, and Performance.

Purpose: We investigated whether varying the number of repetitions of high-intensity exercise during work-matched warm-ups modulates physiological responses (heart rate, metabolic responses, and core temperature), perceptions (ratings of perceived exertion, effort of breathing), readiness for exercise, and short-term exercise performance. Methods: Ten physically active young males performed a 30-s Wingate anaerobic test (WAnT) following a warm-up consisting of submaximal constant-workload cycling at 60% maximal oxygen uptake with no high-intensity cycling (constant-workload warm-up) or with 1, 4, or 7 repetitions of 10 s of high-intensity cycling at 110% maximal oxygen uptake. All warm-ups were matched for duration (10 min) and total work. Results: Warm-ups with seven repetitions of high-intensity cycling resulted in higher ratings of perceived whole-body exertion and effort of breathing than the constant-workload warm-up. Warm-up with four repetitions of high-intensity cycling produced greater readiness for a 30-s WAnT (7.33 ± 0.73 AU) than the constant-workload warm-up (6.33 ± 0.98 AU) (P = .022). Physiological responses did not differ among the four warm-up conditions, though peak heart rate was slightly higher (~5 beats/min) during warm-up with four or seven repetitions of high-intensity cycling than during the constant-workload warm-up. Peak, mean, and minimum power output during the 30-s WAnT did not differ among the four warm-up conditions. Conclusions: These results suggest that the effects of warm-ups with intermittent high-intensity exercise on physiological responses and short-term high-intensity exercise performance do not greatly differ from a warm-up with a work-matched submaximal constant-workload. However, they appear to modulate perceptions and readiness as a function of the number of repetitions of the high-intensity exercise.

Ingestion of carbonated water increases middle cerebral artery blood velocity and improves mood states in resting humans exposed to ambient heat stress.

Sugar-free carbonated water is consumed worldwide. The consumption of carbonated water is high in summer, when the heat loss responses of sweating and skin vasodilation are activated, and thermal perceptions (thermal sensation and comfort) and mood states are negatively modulated. However, whether ingesting carbonated water under ambient heat exposure modulates cerebral blood flow index, heat loss responses, thermal perceptions, and mood states remains to be determined. In this study, 17 healthy, habitually active, young adults (eight women) ingested 4 °C noncarbonated or carbonated water under 37 °C ambient heat-stressed resting conditions. Both drinks increased the middle cerebral artery mean blood velocity, an index of cerebral blood flow, and mean arterial pressure, with carbonated water exhibiting higher elevations than noncarbonated water (P < 0.05). However, the heart rate, sweat rate, and skin blood flow during and after drinking remained unchanged between the two conditions (P > 0.05). The thermal sensation and comfort after drinking remained unchanged between the two conditions (P > 0.05); but, a drink-induced reduction in sleepiness was higher, and drink-induced elevations in motivation and exhilaration were higher after ingesting carbonated water than those after ingesting noncarbonated water (P < 0.05). The analyses suggest that in humans under ambient heat-stressed resting conditions, ingestion of cold carbonated water increases the cerebral blood flow index, blood pressure, motivation, and exhilaration, whereas it decreases sleepiness relative to ingestion of noncarbonated cold water. However, ingestion of cold carbonated water fails to modulate thermoregulatory responses and thermal perception as opposed to noncarbonated cold water.

CO2-Enriched Air Inhalation Modulates the Ventilatory and Metabolic Responses of Endurance Runners During Incremental Running in Hypobaric Hypoxia.

Cao, Yinhang, Naoto Fujii, Tomomi Fujimoto, Yin-Feng Lai, Takeshi Ogawa, Tsutomu Hiroyama, Yasushi Enomoto, and Takeshi Nishiyasu. CO2-enriched air inhalation modulates the ventilatory and metabolic responses of endurance runners during incremental running in hypobaric hypoxia. High Alt Med Biol. 23:125-134, 2022. Aim: We measured the effects of breathing CO2-enriched air on ventilatory and metabolic responses during incremental running exercise under moderately hypobairc hypoxic (HH) conditions. Materials and Methods: Ten young male endurance runners [61.4 ± 6.0 ml/(min·kg)] performed incremental running tests under three conditions: (1) normobaric normoxia (NN), (2) HH (2,500 m), and (3) HH with 5% CO2 inhalation (HH+CO2). The test under NN was always performed first, and then, the two remaining tests were completed in random and counterbalanced order. Results: End-tidal CO2 partial pressure (55 ± 3 vs. 35 ± 1 mmHg), peak ventilation (163 ± 14 vs. 152 ± 12 l/min), and peak oxygen uptake [52.3 ± 5.5 vs. 50.5 ± 4.9 ml/(min·kg)] were all higher in the HH+CO2 than HH trial (all p < 0.01), respectively. However, the duration of the incremental test did not differ between HH+CO2 and HH trials. Conclusion: These data suggest that chemoreflex activation by breathing CO2-enriched air stimulates breathing and aerobic metabolism during maximal intensity exercise without affecting exercise performance in male endurance runners under a moderately hypobaric hypoxic environment.