Strategies to mitigate acute kidney injury risk during physical work in hot environments.

Prolonged physical work in the heat can reduce renal function and increase the risk of acute kidney injury (AKI). This is concerning given that the latest climate change projections forecast a rise in global temperature as well as the frequency, intensity, and duration of heatwaves. This means that outdoor and indoor workers in the agriculture or construction industries will be exposed to higher heat stress in the years ahead. Several studies indicate a higher incidence of chronic kidney disease from nontraditional origins (CKDnt) in individuals exposed to high temperatures, intense physical work, and/or recurrent dehydration. It has been proposed that prolonged physical work in the heat accompanied by dehydration results in recurrent episodes of AKI that ultimately lead to permanent kidney damage and the development of CKDnt. Thus, there is a need to identify and test strategies that can alleviate AKI risk during physical work in the heat. The purpose of this review is to present strategies that might prevent and mitigate the risk of AKI induced by physical work in the heat.

The biphasic activity of autophagy and heat shock protein response in peripheral blood mononuclear cells following acute resistance exercise in resistance-trained males.

PURPOSE: Autophagy and heat shock protein (HSP) response are proteostatic systems involved in the acute and adaptive responses to exercise. These systems may upregulate sequentially following cellular stress including acute exercise, however, currently few data exist in humans. This study investigated the autophagic and HSP responses to acute intense lower body resistance exercise in peripheral blood mononuclear cells (PBMCs) with and without branched-chain amino acids (BCAA) supplementation. METHODS: Twenty resistance-trained males (22.3 ± 1.5 yr; 175.4 ± .7 cm; 86.4 ± 15.6 kg) performed a bout of intense lower body resistance exercise and markers of autophagy and HSP70 were measured immediately post- (IPE) and 2, 4, 24, 48, and 72 h post-exercise. Prior to resistance exercise, 10 subjects were randomly assigned to BCAA supplementation of 0.22 g/kg/d for 5 days pre-exercise and up to 72 h following exercise while the other 10 subjects consumed a placebo (PLCB). RESULTS: There were no difference in autophagy markers or HSP70 expression between BCAA and PLCB groups. LC3II protein expression was significantly lower 2 and 4 h post-exercise compared to pre-exercise. LC3II: I ratio was not different at any time point compared to pre-exercise. Protein expression of p62 was lower IPE, 2, and 4 h post-exercise and elevated 24 h post-exercise. HSP70 expression was elevated 48 and 72 h post-exercise. CONCLUSIONS: Autophagy and HSP70 are upregulated in PBMCs following intense resistance exercise with autophagy increasing initially post-exercise and HSP response in the latter period. Moreover, BCAA supplementation did not affect this response.

Effect of heat stress on heat shock protein expression and hypertrophy-related signaling in the skeletal muscle of trained individuals.

Muscle mass is balanced between hypertrophy and atrophy by cellular processes, including activation of the protein kinase B-mechanistic target of rapamycin (Akt-mTOR) signaling cascade. Stressors apart from exercise and nutrition, such as heat stress, can stimulate the heat shock protein A (HSPA) and C (HSPC) families alongside hypertrophic signaling factors and muscle growth. The effects of heat stress on HSP expression and Akt-mTOR activation in human skeletal muscle and their magnitude of activation compared with known hypertrophic stimuli are unclear. Here, we show a single session of whole body heat stress following resistance exercise increases the expression of HSPA and activation of the Akt-mTOR cascade in skeletal muscle compared with resistance exercise in a healthy, resistance-trained population. Heat stress alone may also exert similar effects, though the responses are notably variable and require further investigation. In addition, acute heat stress in C2C12 muscle cells enhanced myotube growth and myogenic fusion, albeit to a lesser degree than growth factor-mediated hypertrophy. Though the mechanisms by which heat stress stimulates hypertrophy-related signaling and the potential mechanistic role of HSPs remain unclear, these findings provide additional evidence implicating heat stress as a novel growth stimulus when combined with resistance exercise in human skeletal muscle and alone in isolated murine muscle cells. We believe these findings will help drive further applied and mechanistic investigation into how heat stress influences muscular hypertrophy and atrophy.NEW & NOTEWORTHY We show that acute resistance exercise followed by whole body heat stress increases the expression of HSPA and increases activation of the Akt-mTOR cascade in a physically active and resistance-trained population.

The heat shock connection: skeletal muscle hypertrophy and atrophy.

Skeletal muscle is an integral tissue system that plays a crucial role in the physical function of all vertebrates and is a key target for maintaining or improving health and performance across the lifespan. Based largely on cellular and animal models, there is some evidence that various forms of heat stress with or without resistance exercise may enhance skeletal muscle growth or reduce its loss. It is not clear whether these stimuli are similarly effective in humans or meaningful compared with exercise alone across various heating methodologies. Furthermore, the magnitude by which heat stress may influence whole body thermoregulatory responses and the connection to skeletal muscle adaptation remains ambiguous. Finally, the underlying mechanisms, which may include interaction between relevant heat shock proteins and intracellular hypertrophy and atrophy related factors, remain unclear. In this narrative review, we examine the relevant literature regarding heat stress alone or in combination with resistance exercise emphasizing skeletal muscle hypertrophy and atrophy across cellular and animal models, as well as human investigations. In addition, we present working mechanistic theories for heat shock protein-mediated signaling effects regarding hypertrophy and atrophy-related signaling processes. Importantly, continued research is necessary to determine the practical effects and mechanisms of heat stress with and without resistance exercise on skeletal muscle function via growth and maintenance.

High-altitude exposures and intestinal barrier dysfunction.

Gastrointestinal complaints are often reported during ascents to high altitude (>2,500 m), though their etiology is not known. One potential explanation is injury to the intestinal barrier which has been implicated in the pathophysiology of several diseases. High-altitude exposures can reduce splanchnic perfusion and blood oxygen levels causing hypoxic and oxidative stress. These stressors might injure the intestinal barrier leading to consequences such as bacterial translocation and local/systemic inflammatory responses. The purpose of this mini-review is to 1) discuss the impact of high-altitude exposures on intestinal barrier dysfunction and 2) present medications and dietary supplements which may have relevant impacts on the intestinal barrier during high-altitude exposures. There is a small but growing body of evidence which shows that acute exposures to high altitudes can damage the intestinal barrier. Initial data also suggest that prolonged hypoxic exposures can compromise the intestinal barrier through alterations in immunological function, microbiota, or mucosal layers. Exertion may worsen high-altitude-related intestinal injury via additional reductions in splanchnic circulation and greater hypoxemia. Collectively these responses can result in increased intestinal permeability and bacterial translocation causing local and systemic inflammation. More research is needed to determine the impact of various medications and dietary supplements on the intestinal barrier during high-altitude exposures.

Exercise in hypobaric hypoxia increases markers of intestinal injury and symptoms of gastrointestinal distress.

NEW FINDINGS: What is the central question of this study? What is the effect of hypobaric hypoxia on markers of exercise-induced intestinal injury and symptoms of gastrointestinal (GI) distress? What is the main finding and its importance? Exercise performed at 4300 m of simulated altitude increased intestinal fatty acid binding protein (I-FABP), claudin-3 (CLDN-3) and lipopolysaccharide binding protein (LBP), which together suggest that exercise-induced intestinal injury may be aggravated by concurrent hypoxic exposure. Increases in I-FABP, LBP and CLDN-3 were correlated to exercise-induced GI symptoms, providing some evidence of a link between intestinal barrier injury and symptoms of GI distress. ABSTRACT: We sought to determine the effect of exercise in hypobaric hypoxia on markers of intestinal injury and gastrointestinal (GI) symptoms. Using a randomized and counterbalanced design, nine males completed two experimental trials: one at local altitude of 1585 m (NORM) and one at 4300 m of simulated hypobaric hypoxia (HYP). Participants performed 60 min of cycling at a workload that elicited 65% of their NORM V̇O2max${\dot V_{{{\rm{O}}_{\rm{2}}}{\rm{max}}}}$ . GI symptoms were assessed before and every 15 min during exercise. Pre- and post-exercise blood samples were assessed for intestinal fatty acid binding protein (I-FABP), claudin-3 (CLDN-3) and lipopolysaccharide binding protein (LBP). All participants reported at least one GI symptom in HYP compared to just one participant in NORM. I-FABP significantly increased from pre- to post-exercise in HYP (708 ± 191 to 1215 ± 518 pg ml-1 ; P = 0.011, d = 1.10) but not NORM (759 ± 224 to 828 ± 288 pg ml-1 ; P > 0.99, d = 0.27). CLDN-3 significantly increased from pre- to post-exercise in HYP (13.8 ± 0.9 to 15.3 ± 1.2 ng ml-1 ; P = 0.003, d = 1.19) but not NORM (13.7 ± 1.8 to 14.2 ± 1.6 ng ml-1 ; P = 0.435, d = 0.45). LBP significantly increased from pre- to post-exercise in HYP (10.8 ± 1.2 to 13.9 ± 2.8 µg ml-1 ; P = 0.006, d = 1.12) but not NORM (11.3 ± 1.1 to 11.7 ± 0.9 µg ml-1 ; P > 0.99, d = 0.32). I-FABP (d = 0.85), CLDN-3 (d = 0.95) and LBP (d = 0.69) were all significantly higher post-exercise in HYP compared to NORM (P ≤ 0.05). Overall GI discomfort was significantly correlated to ΔI-FABP (r = 0.71), ΔCLDN-3 (r = 0.70) and ΔLBP (r = 0.86). These data indicate that cycling exercise performed in hypobaric hypoxia can cause intestinal injury, which might cause some commonly reported GI symptoms.

Can linear regression confirm VO2max was attained in middle-aged and older adults?

PURPOSE: Evaluate the efficacy of a regression method for identifying a VO2 plateau to confirm the attainment of VO2max compared to a verification trial in middle-aged and older adults. METHODS: Eleven men and ten women (age 61.0 ± 8.1, VO2max 21.8-50.3 ml/kg/min, n = 21) completed an individualized ramp graded exercise test (GXT) on the cycle ergometer, and one hour later, a verification trial at 105% of their maximal work rate (WR) achieved during the GXT. A plateau in VO2 was used to confirm VO2max was attained. VO2 plateau was identified using the difference between the highest VO2 between the two trials and a linear regression analysis of the VO2-WR relationship during the GXT. McNemar's test of marginal homogeneity was used to detect differences in the proportion of paired data of individuals' attainment of VO2max criteria. RESULTS: Of the 21 participants, 15 (71.4%) met the verification criterion while 6 (28.6%) did not, compared to the regression method where 16 (76.2%) achieved the regression criterion while 5 (23.8%) did not. McNemar's test revealed no significant difference between participants' ability to achieve the regression and verification criteria (p = 0.999). CONCLUSION: The regression method is an effective strategy for confirming VO2max was attained with middle-aged and older adults on a cycle ergometer. This time-efficient regression method is comparable with the verification criterion but does not require a second maximal test, which may be advantageous for those where the verification trial may not be practical.

Heat acclimation during low-intensity exercise increases V̇O2max and Hsp72, but not markers of mitochondrial biogenesis and oxidative phosphorylation, in skeletal tissue.

NEW FINDINGS: What is the central question of this study? Heat acclimation increases tolerance to exercise performed in the heat and may improve maximal oxygen uptake (VO2 max) and performance in temperate environments. However, it is unknown if HA affects the expression of proteins related to mitochondrial biogenesis and oxidative capacity in skeletal muscle. What is the main finding and its importance? We showed that heat acclimation increased VO2 max in a temperate environment but did not change markers of mitochondrial biogenesis and oxidative phosphorylation in the skeletal muscle. ABSTRACT: Heat acclimation (HA) increases tolerance to exercise performed in the heat and may improve maximal oxygen uptake ( V̇O2max ) in temperate environments. However, it is unknown if HA affects the expression of proteins related to mitochondrial biogenesis and oxidative capacity in skeletal muscle. The purpose of this study was to investigate the effect of HA on skeletal muscle markers of mitochondrial biogenesis and oxidative phosphorylation in recreationally trained adults. Thirteen (7 males and 6 females) individuals underwent 10 days of HA. Participants performed two 45 min bouts of exercise (walking at 30-40% maximal velocity at 3% grade) with 10 min rest per session in a hot environment (∼42°C and 30-50% relative humidity). V̇O2max , ventilatory thresholds (VT), and protein expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), mitochondrial transcription factor A (TFAM), calcium/calmodulin-dependent protein kinase (CaMK), electron transport chain (ETC) complexes I-IV, and heat shock protein 72 (Hsp72) in skeletal muscle were measured pre- and post-HA. Comparing day 1 to day 10, HA was confirmed by lower resting core temperature (Tcore ) (P = 0.026), final Tcore (P < 0.0001), mean heart rate (HR) (P = 0.002), final HR (P = 0.003), mean ratings of perceived exertion (RPE) (P = 0.026) and final RPE (P = 0.028). Pre- to post-HA V̇O2max (P = 0.045) increased but VT1 (P = 0.263) and VT2 (P = 0.239) were unchanged. Hsp72 (P = 0.007) increased, but skeletal muscle protein expression (PGC-1α, P = 0.119; TFAM, P = 0.763; CaMK, P = 0.19; ETC I, P = 0.629; ETC II, P = 0.724; ETC III, P = 0.206; ETC IV, P = 0.496) were not affected with HA. HA during low-intensity exercise increased V̇O2max in a temperate environment and Hsp72 but it did not affect markers of mitochondrial biogenesis and oxidative phosphorylation in the skeletal muscle.

Effect of Predicted Versus Measured Thoracic Gas Volume on Body Fat Percentage in Young Adults.

The BodPod® (COSMED, Concord, CA) uses predicted (pTGV) or measured thoracic gas volume (mTGV) during estimations of percentage body fat (%BF). In young adults, there is inconsistent evidence on the variation between pTGV and mTGV, and the effect of sex as a potential covariate on this relationship is unknown. This study examined the difference between TGV assessments and its effect on %BF and potential sex differences that may impact this relationship. A retrospective analysis of BodPod® pTGV and mTGV for 95 men and 86 women ages 18-30 years was performed. Predicted TGV was lower than mTGV for men (-0.49 ± 0.7 L; p < .0001). For men, %BF derived by pTGV was lower than that by mTGV (-1.3 ± 1.8%; p < .0001). For women, no differences were found between pTGV and mTGV (-0.08 ± 0.6 L; p > .05) or %BF (-0.03 ± 0.2%; p > .05). The two-predictor model of sex and height was able to account for 57.9% of the variance in mTGV, F(2, 178) = 122.5, p < .0001. Sex corrected for the effect of height was a significant predictor of mTGV (ß = 0.483 L, p < .0001). There is bias for pTGV to underestimate mTGV in individuals with a large mTGV, which can lead to significant underestimations of %BF in young adults; this was especially evident for men in this study. Sex is an important covariate that should be considered when deciding to use pTGV. The results indicate that TGV should be measured whenever possible for both men and women ages 18-30 years.

Metabolic effects of two high-intensity circuit training protocols: Does sequence matter?

BACKGROUND/OBJECTIVE: The integration of high-intensity interval training (HIIT) and circuit weight training (CWT) is seamless and practical for meeting recommended exercise guidelines. The purpose of this study was to determine the ideal combination of HIIT and CWT to elicit desired acute cardiorespiratory and metabolic responses in variables such as energy expenditure (EE), oxygen consumption (VO2), heart rate (HR), blood lactate (BLa-), excess post-exercise oxygen consumption (EPOC), rating of perceived exertion (RPE), and enjoyment. METHODS: Fourteen trained males (25.7 ±â€¯4.4 yr) completed two exercise protocols matched for volume and recovery periods. On one day, participants performed six HIIT bouts prior to three rounds of a nine exercise CWT protocol (HIC). The second day (separated by ≥ 72 h) consisted of three rounds of three mini-circuits (three exercises per circuit) integrated with three HIIT bouts between the first and second and second and third mini-circuits (TRI). VO2, HR, and EE were monitored throughout both protocols. EPOC for a 20-min duration, [BLa-] (five time points), RPE, and enjoyment were measured post-exercise. RESULTS: Energy expenditure was significantly higher during the HIC compared to the TRI protocol (p = .012), as well as EPOC (p = .034). [BLa-] was significantly greater immediate-, 5min-, 10min- and 20min-post-exercise following HIC as compared to TRI. Mean values for HIC and TRI were similar (p > .05) for HR and RPE. CONCLUSION: Performing HIIT prior to CWT elicits a higher metabolic perturbation compared to the TRI protocol. Although a significant EE difference was detected between the two trials, the practical difference (∼20 kcal) between protocols indicates both protocols are similarly effective for caloric expenditure, metabolic and cardiorespiratory response.

Telemedicine-Based Health Coaching Is Effective for Inducing Weight Loss and Improving Metabolic Markers.

BACKGROUND: To assess the efficacy of health coaching (HC) delivered through videoconferencing (VC) to favorably change physical activity (PA), weight, and metabolic markers in adults with high body mass index (BMI). MATERIALS AND METHODS: Thirty adults (BMI ≥30 kg/m2) were randomly assigned to one of three groups: VC, in-person (IP), or control group (CG). Participants received wireless watches and weight scales to sync with their personal smartphones; recorded data were wirelessly uploaded to a secure database. Participants assigned to VC and IP received individualized HC by a multidisciplinary team (registered dietitian, exercise physiologist, and medical doctor) based on data uploaded over the 12-week intervention. Steps/day and weight loss were analyzed through analyses of covariance. RESULTS: Within- and between-group changes in weight (kg), glucose, insulin, hemoglobin A1c (HbA1c), and Homeostasis Model Assessment estimate of insulin resistance (HOMA-IR) were analyzed through analyses of variance. Weight loss was greater (p < 0.05) for VC (8.23 ± 4.5 kg; 7.7%) than IP (3.2 ± 2.6 kg; 3.4%) and CG (2.9 ± 3.9 kg; 3.3%), respectively. Steps/day were significantly higher in VC than IP at week 4 and VC was significantly higher than the CG at weeks 6, 8, 9, and 11 (p ≤ 0.05). No within- or between-group differences were found for glucose, insulin, or HbA1C. HOMA-IR decreased for VC only (p ≤ 0.05). CONCLUSIONS: Our innovative, multidisciplinary, telemedicine HC delivered through VC led to more favorable changes in weight loss, PA (steps/day), and HOMA-IR than IP or no HC. VC may be an economical approach to improve health and promote behavior change in obese adults. CLINICAL TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier NCT03278951.

Intraindividual Variability in Test-Retest Air Displacement Plethysmography Measurements of Body Density for Men and Women.

Air displacement plethysmography (ADP) is a popular method for estimating body density (Db). Most ADP tests are performed once, with test-retest investigations scarce. Therefore, we investigated test-retest reliability of ADP. Active men (n = 25) and women (n = 25) volunteered and followed standard pretest guidelines. Participants wore dry, form-fitting swimwear and manufacturer-supplied swim caps. In a single session, two ADP trials with measured thoracic gas volume (TGV) were performed without repositioning participants. Separate 2 (sex) × 2 (ADP trial) repeated-measures ANOVAs were performed to investigate within-between comparisons of Db, TGV, body volume (Vb), and relative fatness (%BF). Paired t tests were used to investigate significant differences as appropriate. The Bland and Altman technique was used to depict individual intertrial variations. For all analyses, α =.05. A significant main effect for sex was found; men were lower in %BF and higher in all other variables compared with women. Individual variability was notable (ADP1-ADP2). The range of individual intertrial differences were larger for women than men, respectively, for Db (-0.0096-0.0045 g/cc; -0.0019-0.0054 g/cc), TGV (-0.623-1.325 L; -0.584-0.378 L), Vb (-0.249-2.10 L; -0.234-0.397 L), and %BF (-2.1-4.4%; -0.2-0.9%). When assessing body composition of women via ADP or using Db from ADP in a multicomponent model, at least two trials with measured TGV should be performed and the average of the values recorded and reported.

Effect of Acute Dietary Nitrate Consumption on Oxygen Consumption During Submaximal Exercise in Hypobaric Hypoxia.

Reduced partial pressure of oxygen impairs exercise performance at altitude. Acute nitrate supplementation, at sea level, may reduce oxygen cost during submaximal exercise in hypobaric hypoxia. Therefore, we investigated the metabolic response during exercise at altitude following acute nitrate consumption. Ten well-trained (61.0 ± 7.4 ml/kg/min) males (age 28 ± 7 yr) completed 3 experimental trials (T1, T2, T3). T1 included baseline demographics, a maximal aerobic capacity test (VO2max) and five submaximal intensity cycling determination bouts at an elevation of 1600 m. A 4-day dietary washout, minimizing consumption of nitrate-rich foods, preceded T2 and T3. In a randomized, double-blind, placebo-controlled, crossover fashion, subjects consumed either a nitrate-depleted beetroot juice (PL) or ~12.8 mmol nitrate rich (NR) beverage 2.5 hr before T2 and T3. Exercise at 3500 m (T2 and T3) via hypobaric hypoxia consisted of a 5-min warm-up (25% of normobaric VO2max) and four 5-min cycling bouts (40, 50, 60, 70% of normobaric VO2max) each separated by a 4-min rest period. Cycling RPM and watts for each submaximal bout during T2 and T3 were determined during T1. Preexercise plasma nitrite was elevated following NR consumption compared with PL (1.4 ± 1.2 and 0.7 ± 0.3 uM respectively; p < .05). There was no difference in oxygen consumption (-0.5 ± 1.8, 0.1 ± 1.7, 0.7 ± 2.1, and 1.0 ± 3.0 ml/kg/min) at any intensity (40, 50, 60, 70% of VO2max, respectively) between NR and PL. Further, respiratory exchange ratio, oxygen saturation, heart rate and rating of perceived exertion were not different at any submaximal intensity between NR and PL either. Blood lactate, however, was reduced following NR consumption compared with PL at 40 and 60% of VO2max (p < .0.05). Our findings suggest that acute nitrate supplementation before exercise at 3500 m does not reduce oxygen cost but may reduce blood lactate accumulation at lower intensity workloads.

Talk test as a practical method to estimate exercise intensity in highly trained competitive male cyclists.

The Talk Test (TT) has been used to determine exercise intensity among various population subgroups but not for competitive athletes. This study was designed to compare the ventilatory threshold (VT) with the last positive (+/+), equivocal (+/-), and negative (-/-) stages of the TT for highly trained cyclists. Twelve men (26.5 ± 4.6 years, 71.9 ± 7.6 kg) consented and completed the study, as approved by the university institutional review board. A maximal graded exercise test was used to identify VT, maximal aerobic capacity ((Equation is included in full-text article.)max: 65.9 ± 6.9 ml·kg(-1)·min(-1)), and maximal heart rate (HRmax: 187.3 ± 11.3 b·min). On a separate visit, the TT was administered using the same protocol. Participants were asked if they could speak comfortably after a standard passage recitation. Response options were: "Yes" (+/+), "I'm not sure" (+/-), or "No" (-/-). Variables at VT were compared with the last (+/+), (+/-), and (-/-) stages of TT through t-test with Bonferroni's adjustment (0.05/3). Differences (p ≤ 0.017) were found between variables at VT, as compared with (+/+) TT ((Equation is included in full-text article.): 32.9 ± 7.7 ml·kg(-1)·min(-1), %(Equation is included in full-text article.): 49.9 ± 9.9, heart rate [HR]: 128.7 ± 18.7 b·min, %HRmax: 68.6 ± 7.9, rating of perceived exertion [RPE]: 11.1 ± 1.1) and (+/-) TT ((Equation is included in full-text article.): 44.4 ± 7.5 ml·kg(-1)·min(-1), %(Equation is included in full-text article.): 67.2 ± 7.5). There were no differences between RPE- and HR-based variables at VT, as compared with (+/-) TT (RPE: 13.6 ± 0.63, HR: 147.1 ± 17.2 b·min, %HRmax: 78.5 ± 7.4) or (-/-) TT ((Equation is included in full-text article.): 48.8 ± 7.8 ml·kg(-1)·min(-1), %(Equation is included in full-text article.): 73.9 ± 7.1, HR: 155.6 ± 13.6 b·min, %HRmax: 83.1 ± 5.3, RPE: 14.8 ± 0.90). We found that when the athlete could no longer speak comfortably, he was exercising at or near his VT; we concluded that (-/-) TT estimated VT and can therefore provide a practical method to gauge exercise intensity for highly trained competitive cyclists similar to those in our study.

Palm Cooling and Heating Delays Fatigue During Resistance Exercise in Women.

We previously reported that cold application to the palms between sets of high-intensity bench press exercise produces an ergogenic effect in men. In this study, we hypothesized that palm cooling (PC) or heating during rest intervals between high-intensity weight training sets will increase total repetitions and exercise volume load (kilograms) in resistance trained female subjects in a thermoneutral (TN) environment. Eight female subjects (mean ± SD, age = 25 ± 6 years, height = 160 ± 6 cm, body mass = 56 ± 7 kg, 1-repetition maximum [1RM] = 52 ± 6 kg, weight training experience = 6 ± 2 years) completed 4 sets of 85% 1RM bench press exercise to failure, with 3-minute rest intervals. Exercise trials were performed in a counterbalanced order on 3 days, separated by at least 3 days in TN, Palm heating (PH), and PC conditions. Heating and cooling were applied by placing both hands in a hand cooling device with the hand plate set to 45° C for heating and 10° C for cooling. Data were analyzed using a 2-factor repeated-measures analysis of variance and Tukey's post hoc tests. Palm cooling repetitions were significantly higher than TN repetitions during the second set, and PH repetitions were significantly higher than those of TN during the fourth set. Total exercise volume load (kilograms) for both PC (1,387 ± 358) and PH (1,349 ± 267) were significantly higher than TN (1,187 ± 262). In women, both heating and cooling of the palms between sets of resistance exercise increased the total exercise volume load performed. This ergogenic response to a peripheral sensory input is consistent with the central governor theory of muscular fatigue.

Relative Importance of Four Muscle Groups for Indoor Rock Climbing Performance.

Little research is available to guide training programs for rock climbers. To help meet this need, we sought to determine the relative importance of 4 muscle groups for rock climbing performance. Eleven male climbers were familiarized with an indoor climbing route before 5 separate days of testing. On testing days, subjects were randomly assigned to climb with no prefatiguing exercise (control climb) or after a prefatiguing exercise designed to specifically target the digit flexors (DF), shoulder adductors (SA), elbow flexors (EF), or lumbar flexors (LF). Immediately after the prefatiguing exercise, the subject climbed the route as far as possible without rest until failure. The number of climbing moves was recorded for each climb. Surface electromyography of the target muscles was recorded during the prefatigue. Fewer climbing moves were completed after prefatigue of the DF (50 ± 18%) and EF (78 ± 22%) (p ≤ 0.05) compared with the control climb. The number of moves completed after prefatigue of the LF and SA were not statistically significant compared with the control climb (p > 0.05). The short time lapse between the end of prefatiguing exercise and the start of climbing (transit time), which may have allowed for some recovery, was not different among trials (p > 0.05). Electromyography median frequency was reduced from beginning to end of each prefatiguing exercise. These results suggest that among the muscle groups studied in men, muscular endurance of DF and EF muscle groups is especially important for rock climbing on 40° overhanging terrain.

The Potential Interplay Between HIF-1α, Angiogenic, and Autophagic Signaling During Intermittent Hypoxic Exposure and Exercise.

Berkemeier QN, Deyhle MR, McCormick JJ, Escobar KA, Mermier CM. The Potential Interplay between HIF-1α, Angiogenic, and Autophagic Signaling during Intermittent Hypoxic Exposure and Exercise High Alt Med Biol. 00:000-000, 2024.-Berkemeier QN, Deyhle MR, McCormick JJ, Escobar KA, Mermier CM. The Potential Interplay between HIF-1α, Angiogenic, and Autophagic Signaling During Intermittent Hypoxic Exposure and Exercise High Alt Med Biol. 00:000-000, 2024.-Environmental hypoxia as a result of decreased barometric pressure upon ascent to high altitudes (>2,500 m) presents increased physiological demands compared with low altitudes, or normoxic environments. Competitive athletes, mountaineers, wildland firefighters, military personnel, miners, and outdoor enthusiasts commonly participate in, or are exposed to, forms of exercise or physical labor at moderate to high altitudes. However, the majority of research on intermittent hypoxic exposure is centered around hematological markers, and the skeletal muscle cellular responses to exercise in hypoxic environments remain largely unknown. Two processes that may be integral for the maintenance of cellular health in skeletal muscle include angiogenesis, or the formation of new blood vessels from preexisting vasculature and autophagy, a process that removes and recycles damaged and dysfunctional cellular material in the lysosome. The purpose of this review is to is to examine the current body of literature and highlight the potential interplay between low-oxygen-sensing pathways, angiogenesis, and autophagy during acute and prolonged intermittent hypoxic exposure in conjunction with exercise. The views expressed in this paper are those of the authors and do not reflect the official policy of the Department of Army, DOD, DOE, ORAU/ORISE or U.S. Government.

The effects of a harness safety system during maximal treadmill run testing in collegiate middle- and long-distance runners.

This study compared the results of graded maximal treadmill testing with and without a safety harness (SH) spotting system among collegiate middle- and long-distance runners. Thirteen (n = 8 men, n = 5 women) collegiate runners completed 2 randomly selected maximal treadmill tests. One trial used an SH, and one trial used no harness. All tests were separated by at least 48 hours. The subjects began the test at a velocity of 14.5 or 12 km · h with 1% grade for men and women, respectively, and increased 0.80 kilometers/hr per stage. During each trial, metabolic data and running speed values were recorded along with the completion of a safety questionnaire. No significant difference was found for maximal oxygen consumption (60.84 ± 8.89 vs. 60.733 ± 9.38 ml · kg · min) and velocity at maximal oxygen consumption (5.33 ± 0.62 vs. 5.24 ± 0.57 m · s) between the no harness and harness trials, respectively. Test time was found to be significantly longer in the no harness trial (611.06 ± 119.34 vs. 537.38 ± 91.83 seconds, p < 0.05). The results of the safety questionnaire demonstrated that the runners felt significantly more comfortable during the SH trial (p < 0.05).

The physiological, perceptual, and thermoregulatory responses to facemask use during exercise.

The use of masks in public settings and when around people has been recommended to limit the spread of Coronavirus disease 2019 (COVID-19) by major public health agencies. Several different types of masks classified as either medical- or non-medical grade are commonly used among the public. However, concerns with difficulty breathing, re-breathing exhaled carbon dioxide, a decrease in arterial oxygen saturation, and a decrease in exercise performance have been raised regarding the use of mask during exercise. We review the current knowledge related to the effect of different masks during exercise on cardiorespiratory, metabolic, thermoregulatory, and perceptual responses. As such, the current literature seems to suggest that there are minimal changes to cardiovascular, metabolic, and no changes to thermoregulatory parameters with facemask use. However, differences in ventilatory parameters have been reported with submaximal and maximal intensity exercise to volitional fatigue. Literature on perceptual responses to exercise indicate an impact on ratings of perceived exertion, dyspnea, and overall discomfort dependent on mask use as well as exercise intensity. In conclusion, data from the current literature suggests a minimal impact on physiological, perceptual, and thermoregulatory responses dependent on the type of mask used during exercise.