Ammonium chloride ingestion attenuates exercise-induced mRNA levels in human muscle

Minimizing the decrease in intracellular pH during high-intensity exercise training promotes greater improvements in mitochondrial respiration. This raises the intriguing hypothesis that pH may affect the exercise-induced transcription of genes that regulate mitochondrial biogenesis. Eight males performed 10x2-min cycle intervals at 80% VO2speak intensity on two occasions separated by ~2 weeks. Participants ingested either ammonium chloride (ACID) or calcium carbonate (PLA) the day before and on the day of the exercise trial in a randomized, counterbalanced order, using a crossover design. Biopsies were taken from the vastus lateralis muscle before and after exercise. The mRNA level of peroxisome proliferator-activated receptor co-activator 1α (PGC-1α), citrate synthase, cytochome c and FOXO1 was elevated at rest following ACID (P<0.05). During the PLA condition, the mRNA content of mitochondrial- and glucose-regulating proteins was elevated immediately following exercise (P<0.05). In the early phase (0-2 h) of post-exercise recovery during ACID, PGC-1α, citrate synthase, cytochome C, FOXO1, GLUT4, and HKII mRNA levels were not different from resting levels (P>0.05); the difference in PGC-1α mRNA content 2 h post-exercise between ACID and PLA was not significant (P = 0.08). Thus, metabolic acidosis abolished the early post-exercise increase of PGC-1α mRNA and the mRNA of downstream mitochondrial and glucose-regulating proteins. These findings indicate that metabolic acidosis may affect mitochondrial biogenesis, with divergent responses in resting and post-exercise skeletal muscle

Alterations in cognitive performance during passive hyperthermia are task dependent

The objectives of this study were to (1) assess the effect of passive heating upon attention and memory task performance, and (2) evaluate the effectiveness of the application of cold packs to the head on preserving these functions. Using a counterbalance design 16 subjects underwent three trials: a control (CON, 20°C, 40% rH), hot (HOT, 50°C, 50% rH) and hot with the head kept cool (HHC). In each condition, three attention tests and two memory tests were performed. Mean core, forehead and tympanic temperatures were all significantly higher (p< 0.05) during HOT (38.6° ±0.1°, 39.6° ±0.2° and 38.8°±0.1°C, respectively) and HHC (38°±0.2, 37.7°±0.3° and 37.7°C, respectively) than in CON (37.1°±0.6°, 33.3° ±0.2° and 35.9°±0.3°C, respectively). Results indicate that there was impairment in working memory with heat exposure (p < 0.05) without alteration in attentional processes. The regular application of cold packs only prevented the detrimental effect of hyperthermia on short-term memory. Our results show that impairments in cognitive function with passive hyperthermia and the beneficial effect of head cooling are task dependent and suggests that exposure to a hot environment is a competing variable to the cognitive processes

Oral l-menthol reduces thermal sensation, increases work-rate and extends time to exhaustion, in the heat at a fixed rating of perceived exertion

PurposeThe study investigated the effect of a non-thermal cooling agent, l-menthol, on exercise at a fixed subjective rating of perceived exertion (RPE) in a hot environment.MethodEight male participants completed two trials at an exercise intensity between ‘hard’ and ‘very hard’, equating to 16 on the RPE scale at ~35 °C. Participants were instructed to continually adjust their power output to maintain an RPE of 16 throughout the exercise trial, stopping once power output had fallen by 30%. In a randomized crossover design, either l-menthol or placebo mouthwash was administered prior to exercise and at 10 min intervals. Power output, VO2, heart rate, core and skin temperature was monitored, alongside thermal sensation and thermal comfort. Isokinetic peak power sprints were conducted prior to and immediately after the fixed RPE trial.ResultsExercise time was greater (23:23 ± 3:36 vs. 21:44 ± 2:32 min; P = 0.049) and average power output increased (173 ± 24 vs. 167 ± 24 W; P = 0.044) in the l-menthol condition. Peak isokinetic sprint power declined from pre-post trial in the l-menthol l (9.0%; P = 0.015) but not in the placebo condition (3.4%; P = 0.275). Thermal sensation was lower in the l-menthol condition (P = 0.036), despite no changes in skin or core temperature (P > 0.05).Conclusion These results indicate that a non-thermal cooling mouth rinse lowered thermal sensation, resulting in an elevated work rate, which extended exercise time in the heat at a fixed RPE

Fourteen days of smoking cessation improves muscle fatigue resistance and reverses markers of systemic inflammation

Cigarette smoking has a negative effect on respiratory and skeletal muscle function and is a risk factor for various chronic diseases. To assess the effects of 14 days of smoking cessation on respiratory and skeletal muscle function, markers of inflammation and oxidative stress in humans. Spirometry, skeletal muscle function, circulating carboxyhaemoglobin levels, advanced glycation end products (AGEs), markers of oxidative stress and serum cytokines were measured in 38 non-smokers, and in 48 cigarette smokers at baseline and after 14 days of smoking cessation. Peak expiratory flow (p = 0.004) and forced expiratory volume in 1 s/forced vital capacity (p = 0.037) were lower in smokers compared to non-smokers but did not change significantly after smoking cessation. Smoking cessation increased skeletal muscle fatigue resistance (p < 0.001). Haemoglobin content, haematocrit, carboxyhaemoglobin, total AGEs, malondialdehyde, TNF-α, IL-2, IL-4, IL-6 and IL-10 (p < 0.05) levels were higher, and total antioxidant status (TAS), IL-12p70 and eosinophil numbers were lower (p < 0.05) in smokers. IL-4, IL-6, IL-10 and IL-12p70 had returned towards levels seen in non-smokers after 14 days smoking cessation (p < 0.05), and IL-2 and TNF-α showed a similar pattern but had not yet fully returned to levels seen in non-smokers. Haemoglobin, haematocrit, eosinophil count, AGEs, MDA and TAS did not significantly change with smoking cessation. Two weeks of smoking cessation was accompanied with an improved muscle fatigue resistance and a reduction in low-grade systemic inflammation in smokers

Head temperature modulates thermal behavior in the cold in humans

We tested the hypothesis that skin temperature, specifically of the head, is capable of modulating thermal behavior during exercise in the cold. Following familiarization 8 young, healthy, recreationally active males completed 3 trials, each consisting of 30 minutes of self-paced cycle ergometry in 6°C. Participants were instructed to control their exercise work rate to achieve and maintain thermal comfort. On one occasion participants wore only shorts and shoes (Control) and on the 2 other occasions their head was either warmed (Warming) or cooled (Cooling). Work rate, rate of metabolic heat production, thermal perceptions, rectal, mean weighted skin and head temperatures were measured. Exercise work rate was reduced during Warming and augmented during Cooling after the first and second minutes of exercise, respectively (P ≤ 0.04), with the rate of metabolic heat production mirroring work rate. At this early stage of exercise (≤5 min) the changes over time for rectal temperature were negligible and similar (0.1 ± 0.1°C, P = 0.51), while the decrease in mean skin temperature was not different between all trials (1.7 ± 0.6°C, P = 0.13). Mean head temperature was either decreased (Control: 1.5 ± 1.1°C, Cooling: 2.9 ± 0.8°C, both P 0.09) after 10 ± 7 min and this was maintained until the end of exercise. These results indicate that peripheral temperatures modulate thermal behavior in the cold

Should We be Concerned with Nicotine in Sport? Analysis from 60,802 Doping Control Tests in Italy.

Nicotine is a psychostimulant drug with purported use in sports environments, though the use of nicotine among athletes has not been studied extensively. The aim of this study was to assess the nicotine positivity rate in 60,802 anti-doping urine samples from 2012 to 2020. Urine samples obtained in-competition at different national and international sports events held in Italy during the period 2012-2020 were analysed. All samples were from anonymous athletes that were collected and analysed at the WADA-accredited antidoping laboratory in Rome, Italy. Samples were analysed by gas chromatography coupled with mass spectrometry, with a cut-off concentration for nicotine of &gt; 50 ng/mL. Results were stratified by year, sport and sex. An overall mean of 22.7% of the samples (n = 13,804; males: n = 11,099; females: n = 2705) showed nicotine intake, with male samples also displaying higher positivity rates than female (24.1% vs 18.5%). Sample positivity was higher during 2012-2014 (25-33%) than 2015-2020 (15-20%). Samples from team sports displayed a higher positivity rate than those from individual sports (31.4 vs 14.1%). The current data demonstrates that one in five samples from a range of 90 sports test positive for nicotine in-competition. There is a lower positivity rate in endurance versus power/strength athletes and higher positivity rate in team versus individual sports, probably accounted for by differences in physiological and psychological demands and the desire for socialisation. WADA, international and national sports federations should consider these findings with concern, proactively investigate this phenomenon and act in order to protect the health and welfare of its athletes

Effects of hypoxia and hypercapnia on human HRV and respiratory sinus arrhythmia

Purpose: Hypercapnia increases minute ventilation (V’E) with little effect on heart rate (HR), whereas hypoxia may increase HR without affecting V’E. However, the effects of hypercapnia and hypoxia on both heart rate variability (HRV) and the clustering of heart beats during spontaneous breathing (respiratory sinus arrhythmia – RSA), are not clear. Methods: In this study, 10 human volunteers breathed room air (RA), hypercapnic (5% CO 2 ) or hypoxic (10% O 2 ) gas mixtures, each for 6 min, while resting supine. ECG, mean arterial pressure (MAP), ventilatory flow, inhaled and exhaled fractions of CO 2 and O 2 , were recorded throughout. Results: Both V’E and MAP increased with 5% CO 2 , with no change in HR. Hypoxia did not change ventilation but increased HR. High frequency components of HRV, and the relative proportion of heart beats occurring during inhalation increased with 5% CO 2 , but neither changed with 10% O 2 . Conclusion: Increased RSA concomitant with increased MAP suggests RSA – vagal dissociation with hypercapnia. Elevated heart rate with acute hypoxia with no change in either frequency components of HRV or the distribution of heart beats during ventilation, suggested that clustering of heart beats may not be a mechanism to improve ventilation-perfusion matching during hypoxia. Keywords: autonomic nervous system, spectral analysis, cardiovascular control, heart rate variability, hypoxia, hypercapni

Delineating the impacts of air temperature and humidity for endurance exercise

10.1113/EP090969Experimental Physiolog

Intermittent-sprint performance and muscle glycogen after 30 h of sleep deprivation

PURPOSE: The aim of this study was to determine the effects of 30 h of sleep deprivation on consecutive-day intermittent-sprint performance and muscle glycogen content. METHODS: Ten male, team-sport athletes performed a single-day "baseline" session and two consecutive-day experimental trials separated either by a normal night's sleep (CONT1 and CONT2) or no sleep (SDEP1 and SDEP2). Each session included a 30-min graded exercise run and 50-min intermittent-sprint exercise protocol, including a 15-m maximal sprint every minute and self-paced exercise bouts of varying intensities. Muscle biopsies were extracted before and after exercise during the baseline session and before exercise on day 2 during experimental trials. Voluntary force and activation of the right quadriceps, nude mass, HR, core temperature, capillary blood lactate and glucose, RPE, and a modified POMS were recorded before, after, and during the exercise protocols. RESULTS: Mean sprint times were slower on SDEP2 (2.78 ± 0.17 s) compared with SDEP1 (2.70 ± 0.16 s) and CONT2 (2.74 ± 0.15 s, P < 0.05). Distance covered during self-paced exercise was reduced during SDEP2 during the initial 10 min compared with SDEP1 and during the final 10 min compared with CONT2 (P < 0.05). Muscle glycogen concentration was lower before exercise on SDEP2 (209 ± 60 mmol•kg-1 dry weight) compared with CONT2 (274 ± 54 mmol•kg-1 dry weight, P = 0.05). Voluntary force and activation were reduced on day 2 of both conditions; however, both were lower in SDEP2 compared with CONT2 (P < 0.05). Sleep loss did not affect RPE but negatively affected POMS ratings (P < 0.05). CONCLUSIONS: Sleep loss and associated reductions in muscle glycogen and perceptual stress reduced sprint performance and slowed pacing strategies during intermittent-sprint exercise for male team-sport athletes. Copyright © 2011 by the American College of Sports Medicine