Submaximal Endurance Exercise Research Articles

Independent, additive and interactive effects of acute normobaric hypoxia and cold on submaximal and maximal endurance exercise.

To evaluate the independent and combined effects of hypoxia (FiO2 = 13.5%) and cold (-20°C) on physiological and perceptual responses to endurance exercise. 14 trained male subjects ( O2max: 64 ± 5mL/kg/min) randomly performed a discontinuous maximal incremental test to exhaustion on a motorized treadmill under four environmental conditions: Normothermic-Normoxia (N), Normothermic-Hypoxia (H), Cold-Normoxia (C) and Cold-Hypoxia (CH). Performance and physiological and perceptual responses throughout exercise were evaluated. Maximal WorkLoad (WL) and WL at lactate threshold (LT) were reduced in C (-2.3% and -3.5%) and H (-18.0% and -21.7%) compared to N, with no interactive (p = 0.25 and 0.81) but additive effect in CH (-21.5% and -24.6%). Similarly, HRmax and Vemax were reduced in C (-3.2% and -14.6%) and H (-5.0% and -7%), showing additive effects in CH (-7.7% and -16.6%). At LT, additive effect of C (-2.8%) and H (-3.8%) on HR reduction in CH (-5.7%) was maintained, whereas an interactive effect (p = 0.007) of the two stressors combined was noted on Ve (C: -3.1%, H: + 5.5%, CH: -10.9%). [La] curve shifted on the left in CH, displaying an interaction effect between the 2 stressors on this parameter. Finally, RPE at LT was exclusively reduced by hypoxia (p < 0.001), whereas TSmax is synergistically reduced by cold and hypoxia (interaction p = 0.047). If compared to single stress exposure, exercise performance and physiological and perceptual variables undergo additive or synergistic effects when cold and hypoxia are combined. These results provide new insight into human physiological responses to extreme environments.

Dietary Nitrate Supplementation Enhances Performance and Speeds Muscle Deoxyhaemoglobin Kinetics during an End-Sprint after Prolonged Moderate-Intensity Exercise.

Short-term dietary nitrate (NO3-) supplementation has the potential to enhance performance during submaximal endurance, and short-duration, maximal-intensity exercise. However, it has yet to be determined whether NO3- supplementation before and during submaximal endurance exercise can improve performance during a short-duration, maximal-intensity end-sprint. In a randomised, double-blind, crossover study, 9 recreationally active men ingested NO3--rich (BR: 8 mmol NO3-/day) and NO3--depleted (PL: 0.75 mmol NO3-/day) beetroot powder for 7 days. On day 7, participants completed 2 h of moderate-intensity cycling, which immediately transitioned into a 60 s maximal-intensity end-sprint, with supplements ingested 2 h before and 1 h into the moderate-intensity exercise bout. Plasma [NO3-] and [NO2-] were higher in BR compared to PL pre- and post-exercise (p &lt; 0.05). Post-exercise plasma [NO3-] was higher than pre-exercise (562 ± 89 µM vs. 300 ± 73 µM; p &lt; 0.05) and plasma [NO2-] was not significantly different pre- (280 ± 58 nM) and post-exercise (228 ± 63 nM) in the BR condition (p &gt; 0.05). Mean power output during the final 30 s of the end-sprint was greater after BR (390 ± 38 W) compared to PL (365 ± 41 W; p &lt; 0.05). There were no differences between BR and PL in any muscle oxygenation variables during moderate-intensity cycling (p &gt; 0.05), but muscle [deoxyhaemoglobin] kinetics was faster during the end-sprint in BR (6.5 ± 1.4 s) compared to PL (7.3 ± 1.4 s; p &lt; 0.05). These findings suggest that NO3- supplementation has the potential to improve end-sprint performance in endurance events when ingested prior to and during exercise.

Fuelling the fire: assessment of muscle metabolism during submaximal endurance exercise.

Fuelling the fire: assessment of muscle metabolism during submaximal endurance exercise.

The Effect of Medium-Term Sauna-Based Heat Acclimation (MPHA) on Thermophysiological and Plasma Volume Responses to Exercise Performed under Temperate Conditions in Elite Cross-Country Skiers.

The influence of a series of ten sauna baths (MPHA) on thermophysiological and selected hematological responses in 14 elite cross-country skiers to a submaximal endurance exercise test performed under thermoneutral environmental conditions was studied. Thermal and physiological variables were measured before and after the exercise test, whereas selected hematological indices were studied before, immediately after, and during recovery after a run, before (T1) and after sauna baths (T2). MPHA did not influence the baseline internal, body, and skin temperatures. There was a decrease in the resting heart rate (HR: p = 0.001) and physiological strain (PSI: p = 0.052) after MPHA and a significant effect of MPHA on systolic blood pressure (p = 0.03), hematological indices, and an exercise effect but no combined effect of treatments and exercise on the tested variables. A positive correlation was reported between PSI and total protein (%ΔTP) in T2 and a negative between plasma volume (%ΔPV) and mean red cellular volume (%ΔMCV) in T1 and T2 in response to exercise and a positive one during recovery. This may suggest that MPHA has a weak influence on body temperatures but causes a moderate decrease in PSI and modifications of plasma volume restoration in response to exercise under temperate conditions in elite athletes.

The effect of one bout submaximal endurance exercise on the innate and adaptive immune responses of hypertensive patients.

Changes in some of the immune system factors are associated with a risk of cardiovascular disease. Therefore, the purpose of this study was to investigate the effect of one-bout submaximal endurance exercise (OBSEE) on the innate and adaptive responses of hypertensive patients. From among 70 men with hypertension, 20 men (mean age: 60.25±4.59 years, Body Mass Index [BMI]: 29.57±3.68 kg/m2, and the maximal oxygen uptake [VO<inf>2max</inf>] 34.83±2.11 mL/kg/min) were chosen. The statistical sample performed OBSEE for 30 minutes and at 60-65% of the maximum heart rate reserve (MHRR). Blood sampling was performed to measure the response of immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), white blood cells (WBCs), neutrophil (NEUT), basophil (BASO), eosinophil (EO), monocyte (MONO) and lymphocyte (LYMPH) of hypertensive patients before and immediately after exercise. Plasma volume changes (PVCs) were also calculated in order to find out accurate effectiveness of exercise. Shapiro-Wilk test was used to normalize the research data. To analyze the data, paired sample t-test was used at significant level (P≤0.05). The hypothesis test was performed using SPSS software v. 19. The results after adjusting for PVCs showed that OBSEE significantly increased WBCs (P=0.001) in hypertensive patients. On the other hand, a significant decrease was observed in EO (P=0.001) and MONO (P=0.001) levels after OBSEE. Significant changes were not found in NEUT (P=0.072), BASO (P=0.106), LYMPH (P=0.440), IgA (P=0.382), IgG (P=0.245) and IgM (P=0.081) levels. It seems that OBSEE can reduce the risk of hypertension caused by elevated EO and MONO in hypertensive patients.

Aerobic Continuous and Interval Training under Hypoxia Enhances Endurance Exercise Performance with Hemodynamic and Autonomic Nervous System Function in Amateur Male Swimmers.

Hypoxic training is often performed by competitive swimmers to enhance their performance in normoxia. However, the beneficial effects of aerobic continuous and interval training under hypoxia on hemodynamic function, autonomic nervous system (ANS) function, and endurance exercise performance remain controversial. Here we investigated whether six weeks of aerobic continuous and interval training under hypoxia can improve hematological parameters, hemodynamic function, ANS function, and endurance exercise performance versus normoxia in amateur male swimmers. Twenty amateur male swimmers were equally assigned to the hypoxic training group or normoxic training group and evaluated before and after six weeks of training. Aerobic continuous and interval training in the hypoxia showed a more significantly improved hemodynamic function (heart rate, −653.4 vs. −353.7 beats/30 min; oxygen uptake, −62.45 vs. −16.22 mL/kg/30 min; stroke volume index, 197.66 vs. 52.32 mL/30 min) during submaximal exercise, ANS function (root mean square of successive differences, 10.15 vs. 3.32 ms; total power, 0.72 vs. 0.20 ms2; low-frequency/high-frequency ratio, −0.173 vs. 0.054), and endurance exercise performance (maximal oxygen uptake, 5.57 vs. 2.26 mL/kg/min; 400-m time trial record, −20.41 vs. −7.91 s) than in the normoxia. These indicate that hypoxic training composed of aerobic continuous and interval exercise improves the endurance exercise performance of amateur male swimmers with better hemodynamic function and ANS function.

Sub-maximal endurance exercise does not mediate alterations of somatosensory thresholds

Physical exercise has been shown to alter sensory functions, such as sensory detection or perceived pain. However, most contributing studies rely on the assessment of single thresholds, and a systematic testing of the sensory system is missing. This randomised, controlled cross-over study aims to determine the sensory phenotype of healthy young participants and to assess if sub-maximal endurance exercise can impact it. We investigated the effects of a single bout of sub-maximal running exercise (30 min at 80% heart rate reserve) compared to a resting control in 20 healthy participants.The sensory profile was assessed applying quantitative sensory testing (QST) according to the protocol of the German Research Network on Neuropathic Pain. QST comprises a broad spectrum of thermal and mechanical detection and pain thresholds. It was applied to the forehead of study participants prior and immediately after the intervention. Time between cross-over sessions was one week. Sub-maximal endurance exercise did not significantly alter thermal or mechanical sensory function (time × group analysis) in terms of detection and pain thresholds. The sensory phenotypes did not indicate any clinically meaningful deviation of sensory function. The alteration of sensory thresholds needs to be carefully interpreted, and only systematic testing allows an improved understanding of mechanism. In this context, sub-maximal endurance exercise is not followed by a change of thermal and mechanical sensory function at the forehead in healthy volunteers.

Cerebral haemodynamics and oxygenation during whole-body exercise over 5days at high altitude.

What is the central question of this study? Impairment and subsequent improvement in cerebral oxygenation during acute and prolonged exposure to high altitude affect exercise performance. This study innovates by investigating the effect of acute and prolonged high-altitude exposure on cerebral haemodynamics during submaximal endurance exercise performed at the same relative intensity. What is the main finding and its importance? Despite exercising at the same relative intensity at sea level and high altitude, participants showed a sustained impairment in cerebral oxygenation after prolonged exposure to high altitude, which might contribute to the absence of improvement in exercise tolerance. Deterioration and subsequent improvement in cerebral oxygenation during acute and prolonged hypoxic exposure may affect whole-body exercise performance at high altitude. In this study, we investigated the effect of hypoxic exposure on cerebral haemodynamics at different cortical locations during exercise at the same relative intensity after 1 (D1) and 5days (D5) at 4350m. Eleven male subjects performed a submaximal bout of cycling exercise (6min at 35%+6min at 55% + time-to-exhaustion at 75% of peak work rate achieved in the same conditions, i.e. normoxia or hypoxia at sea level) on D1 and D5. Transcranial Doppler and near-infrared spectroscopy were used to assess middle cerebral artery blood velocity and prefrontal and motor cortex oxygenation, respectively. Despite using the same relative intensity, the duration of exercise was reduced on D1 (22.7±5.1min) compared with sea level (32.2±9.0min; P<0.001), with no improvement on D5 (20.9±6.3min; P>0.05). Middle cerebral artery blood velocity during exercise was elevated on D1 (+18.2%) and D5 (+15.0%) compared with sea level (P<0.001). However, prefrontal and motor cortex oxygenation was reduced on D1 and D5 compared with sea level (P<0.001). This pattern was of similar magnitude between cortical locations, whereas the total haemoglobin concentration increased to a greater extent in the prefrontal versus motor cortex at exhaustion on D1 and D5. In contrast to our primary hypothesis, prefrontal and motor cortex oxygenation and exercise performance did not improve over 5days at 4350m. The sustained impairment in cerebral oxygenation might contribute to the absence of improvement in exercise performance after partial acclimatization to high altitude.

Prolonged Heat Acclimation and Aerobic Performance in Endurance Trained Athletes.

Heat acclimation (HA) involves physiological adaptations that directly promote exercise performance in hot environments. However, for endurance-athletes it is unclear if adaptations also improve aerobic capacity and performance in cool conditions, partly because previous randomized controlled trial (RCT) studies have been restricted to short intervention periods. Prolonged HA was therefore deployed in the present RCT study including 21 cyclists [38 ± 2 years, 184 ± 1 cm, 80.4 ± 1.7 kg, and maximal oxygen uptake (VO2max) of 58.1 ± 1.2 mL/min/kg; mean ± SE] allocated to either 5½ weeks of training in the heat [HEAT (n = 12)] or cool control [CON (n = 9)]. Training registration, familiarization to test procedures, determination of VO2max, blood volume and 15 km time trial (TT) performance were assessed in cool conditions (14°C) during a 2-week lead-in period, as well as immediately pre and post the intervention. Participants were instructed to maintain total training volume and complete habitual high intensity intervals in normal settings; but HEAT substituted part of cool training with 28 ± 2 sessions in the heat (1 h at 60% VO2max in 40°C; eliciting core temperatures above 39°C in all sessions), while CON completed all training in cool conditions. Acclimation for HEAT was verified by lower sweat sodium [Na+], reduced steady-state heart rate and improved submaximal exercise endurance in the heat. However, when tested in cool conditions both peak power output and VO2max remained unchanged for HEAT (pre 60.0 ± 1.5 vs. 59.8 ± 1.3 mL O2/min/kg). TT performance tested in 14°C was improved for HEAT and average power output increased from 298 ± 6 to 315 ± 6 W (P < 0.05), but a similar improvement was observed for CON (from 294 ± 11 to 311 ± 10 W). Based on the present findings, we conclude that training in the heat was not superior compared to normal (control) training for improving aerobic power or TT performance in cool conditions.

Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans.

Regular physical activity has a positive effect on human health, but the mechanisms controlling these effects remain unclear. The physiologic and biologic responses to acute exercise are predominantly influenced by the duration and intensity of the exercise regimen. As exercise is increasingly thought of as a therapeutic treatment and/or diagnostic tool, it is important that standardizable methodologies be utilized to understand the variability and to increase the reproducibility of exercise outputs and measurements of responses to such regimens. To that end, we describe two different cycling exercise regimens that yield different physiologic outputs. In a maximal exercise test, exercise intensity is continually increased with a greater workload resulting in an increasing cardiopulmonary and metabolic response (heart rate, stroke volume, ventilation, oxygen consumption and carbon dioxide production). In contrast, during endurance exercise tests, the demand is increased from that at rest, but is raised to a fixed submaximal exercise intensity resulting in a cardiopulmonary and metabolic response that typically plateaus. Along with the protocols, we provide suggestions on measuring physiologic outputs that include, but are not limited to, heart rate, slow and forced vital capacity, gas exchange metrics, and blood pressure to enable the comparison of exercise outputs between studies. Biospecimens can then be sampled to assess cellular, protein, and/or gene expression responses. Overall, this approach can be easily adapted into both short- and long-term effects of two distinct exercise regimens.

Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans

Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans

Pathophysiology of Chronic Systolic Heart Failure. A View from the Periphery.

Heart failure is a common form of heart disease associated with progressive exercise intolerance and high risk of adverse clinical outcome events. The pathophysiology of chronic systolic heart failure is fundamentally determined by the failure of the circulatory system to deliver oxygen sufficient for metabolic needs, and it is best explained by a complex interplay between intrinsic abnormalities of ventricular pump function and extracardiac factors that limit oxygen use in metabolically active tissues. This brief review highlights the role of extracardiac factors (peripheral factors) that may impact exercise capacity in patients with chronic systolic heart failure. Reduced metabolic vasodilation limits delivery of available cardiac output reserve to skeletal muscle during exercise, and it is associated with reduced peak oxygen capacity. Abnormal substrate use in skeletal muscle due to reduced skeletal muscle mass, change in skeletal muscle fiber type, and mitochondrial dysfunction reduces work efficiency and submaximal exercise endurance capacity in patients with systolic heart failure. These extracardiac peripheral mechanisms of impaired exercise tolerance in chronic heart failure may be targets for novel therapeutic development in this patient population.

Effect of Individualized Combined Exercise Versus Group-Based Maintenance Exercise in Patients With Heart Disease and Reduced Exercise Capacity: THE DOPPELHERZ TRIAL.

To compare individualized endurance + resistance exercises (ICE) with a traditional cardiac maintenance program (CMP) on exercise performance in patients with cardiac disease and low exercise capacity. Patients eligible for cardiac rehabilitation with peak exercise capacity <6 metabolic equivalents (METs) were randomly allocated to once-weekly ICE or CMP for 6 mo. ICE used 60 min of individualized moderate endurance and strength exercises. CMP used 60 min of group calisthenics plus relaxation and flexibility exercises. Maximal and submaximal endurance and strength exercise performance were assessed at baseline and 6 mo. Seventy patients (70 ± 9 y; 38% female) were included in the intention-to-treat analyses. Large and significant improvements in both submaximal endurance and maximal strength were observed in the ICE group compared with the CMP group. Submaximal exercise duration (+111 ± 112 sec vs +14 ± 120 sec, P < .01), workload (+16 ± 16 W vs +2 ± 17 W, P < .01), and muscular strength (+7 ± 8 kg vs 0 ± 7 kg and +16 ± 14 kg vs 0.2 ± 12 kg for upper- and lower-body strength, P < .01) all favored ICE over CMP. No significant between-group differences were observed in peak exercise performance (+0.05 ± 0.17 W/kg vs +0.04 ± 0.17 W/kg, P = .83) or peak oxygen uptake (-0.1 ± 3.1 mL/kg/min vs +0.6 ± 3.2 mL/kg/min, P = .38). Patients with cardiac disease and low exercise capacity improved submaximal exercise performance and muscular strength with once-weekly ICE but not with CMP. Neither ICE nor CMP led to an improvement in peak exercise endurance performance. The implementation of ICE in this population would be feasible and may result in greater benefit for performing activities of daily living.

Similarity and differences of maximal and sub-maximal endurance exercise in increase the serum testosterone and DHT concentrations in healthy males

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Exhaustive submaximal endurance and resistance exercises induce temporary immunosuppression via physical and oxidative stress.

Regular running and strength training are the best ways to improve aerobic capacity and develop the size of skeletal muscles. However, uncontrolled physical activities can often lead to an undertraining or over-training syndrome. In particular, overtraining causes persistent fatigue and reduces physical performance due to changes in the various physiological and immunological factors. In this study, we gave an exhaustive submaximal endurance or resistance exercise to participants and investigated the relationship between physical stress (cortisol level in blood), oxidative stress (intracellular ROS accumulation), and adaptive immune response (CD4:CD8 ratio).Materials and MethodsTen male volunteers were recruited, and performed a submaximal endurance or resistance exercise with 85% of VO2max or 1-repetition maximum until exhaustion. Blood samples were collected at rest, and at 0 and 30 min after the exercise. Cortisol levels, oxidative stress, and immune cell phenotypes in peripheral blood were evaluated. Cortisol levels in the sera increased after the exhaustive endurance and resistance exercises and such increments were maintained through the recovery. Intra-cellular ROS levels also increased after the exhaustive endurance and resistance exercises. The ratio of CD4+ T cells to CD8+ T cells after each type of submaximal exercise decreased compared with that at the resting stage, and returned to the resting level at 30 min after the exercise. In this study, an exhaustive endurance or a resistance exercise with submaximal intensity caused excessive physical stress, intra-cellular oxidative stress, and post-exercise immunosuppression. This result suggests that excessive physical stress induced temporary immune dysfunction via physical and oxidative stress.

A double blind randomized placebo control crossover trial on the effect of dietary nitrate supplementation on exercise tolerance in stable moderate chronic obstructive pulmonary disease.

BackgroundDietary nitrate supplementation has been shown to decrease the oxygen cost of exercise and prolong exercise tolerance, as measured by sub-maximal exercise endurance distance and time at 85% V̇O2max, in both elite athletes and normal healthy subjects. Patients with chronic obstructive pulmonary disease (COPD) have reduced quality of life and ability to perform activities of daily living attributable to diminished exercise tolerance, and dietary nitrate may be able to ameliorate this.MethodsWe performed a double-blind, computer-randomized placebo control crossover trial at a tertiary Australian hospital to investigate whether dietary nitrate supplementation as beetroot juice (BR) would augment submaximal exercise endurance in individuals with spirometrically confirmed stable moderate COPD. Volunteers underwent an incremental shuttle walk test to determine V̇O2max followed by a test dose of BR to establish safety in the study population. Participants performed an endurance shuttle walk test (ESWT) at 85% V̇O2max after randomization to either a 3 day wash-in of BR (4.8 mmol twice a day) or placebo (nitrate deplete BR), with a final dose on the morning of testing. They then crossed over after 4 day washout. Repeated measures two sided paired t-tests were employed.Results35 participants were recruited with 19 completing the trial. In the initial safety phase, we measured systolic blood pressure over four hours post first dose of BR, and found a mean 10 mmHg decrement maximal at 1 hour. One individual developed symptomatic postural hypotension and was excluded. The primary outcomes of ESWT distance and time to fatigue improved by 11% and 6% respectively; however these differences did not achieve statistical significance (p = 0.494 and 0.693 respectively).ConclusionsOur study does not support a role for routine dietary nitrate supplementation for enhancement of exercise endurance in COPD.Trial registrationAustralia and New Zealand Clinical Trial Register: ACTRN12611001088932Electronic supplementary materialThe online version of this article (doi:10.1186/s12890-015-0057-4) contains supplementary material, which is available to authorized users.

Respiratory Muscle Training Improves Dyspnea and Exercise Performance in Cancer Survivors

It is estimated that up to 70% of survivors experience dyspnea at some point in their recovery. Dyspnea is correlated with functional performance (6 minute walk test, 6MWT) and peak exercise (VO2PEAK), both of which predict survival in lung cancer. Respiratory muscle weakness represents one of the primary mechanisms contributing to exertional dyspnea and reduced exercise performance in cancer survivors. Respiratory muscle training (RMT) protocols have been used to reduce dyspnea in patients with non-malignant lung disease; however, no studies have explored respiratory muscle training to alleviate dyspnea in cancer survivors. PURPOSE: Implement a RMT program to reduce the sensation of dyspnea, as well as to improve exercise capacity, functional performance and QoL in breast and lung cancer survivors. METHODS: Eight participants who have completed all therapies (57.3 ± 6.8 years) performed RMT, 3 sets of 15 repetitions against spring loaded inspiratory and expiratory valves, 3 days/week, for 4 weeks. Pre- and Post-RRMT, subjects performed maximal expiratory (MEP) and inspiratory pressures (MIP), exercise tests (VO2Peak, sub-maximal cycling endurance at 70% of peak and 6MWT) and questionnaires related to dyspnea (Baseline Dyspnea Index) and quality of life (SF-36). RESULTS: Four breast and four lung cancer survivors completed the protocol (mean years ± SD from treatment = 4.1±3.0). At baseline, FVC and FEV1 were 80.3±18.5 and 77.2±18.2% of predicted. MIP and MEP were 51.8±20.0% and 94.8±19.2% of predicted. Post-RMT, MIP and MEP increased 26.5±21.2% and 40.1±32.7%, respectively (p<0.005). Time to peak (8.5±3.5 min vs. 10.1±3.2 min, p=0.015) and submaximal endurance (16.5±7.7 vs. 32.4±8.7 min, p=0.007) exercise and the distance covered in the 6MWT (414±91 m vs. 441±97 m, p=0.03) were all significantly longer. Finally, baseline dyspnea index (p=0.02) and quality of life (p=0.04) improved post-RMT. CONCLUSION: These results suggest that a progressive resistance inspiratory and expiratory respiratory muscle training program helps to improve respiratory muscle strength, the sensation of dyspnea, as well as exercise performance and QoL in cancer survivors.

Adipose triglyceride lipase (ATGL) deletion from adipocytes, but not skeletal myocytes, impairs acute exercise performance in mice

Fatty acids (FA) and glucose are essential energy substrates that supply exercising muscle. While the selection of substrates is highly influenced by their availability and the intensity and duration of exercise, for prolonged exercise FA are the key substrate. Adipose Triglyceride Lipase (ATGL) is the rate‐limiting enzyme mediating intracellular triacylglycerol hydrolysis and should play a key role in the mobilization of FA during exercise. However, the contribution of adipose versus skeletal muscle fatty acid mobilization to support exercise remains unclear. To gain insight, we generated adipocyte or skeletal myocyte‐specific ATGL knockout mice and determined their response to acute peak and submaximal exercise.We found that adipocyte ATGL‐mediated lipolysis was crucial to support exercise performance, likely owing to limited FA availability and reliance on a rapidly depleted carbohydrate store. Impaired skeletal muscle ATGL‐mediated lipolysis did not impact exercise tolerance and these mice exhibited improved metabolic flexibility during peak exercise.This suggests that adipocyte rather than skeletal myocyte ATGL‐mediated lipolysis plays a greater role during acute peak and submaximal endurance exercise due to limits in substrate availability and greater reliance on carbohydrate oxidation. While further investigation is needed, this suggests the role of IMCL is more of a stop‐gap substrate store to bridge carbohydrate use and FA mobilization and delivery from adipocytes to working muscle.Supported by NIH R01DK090166, HHMI Physician‐Scientist Early Career Award; NIH T32 DK007052

Mental fatigue does not affect maximal anaerobic exercise performance.

Mental fatigue can negatively impact on submaximal endurance exercise and has been attributed to changes in perceived exertion rather than changes in physiological variables. The impact of mental fatigue on maximal anaerobic performance is, however, unclear. Therefore, the aim of the present study was to induce a state of mental fatigue to examine the effects on performance, physiological and perceptual variables from subsequent tests of power, strength and anaerobic capacity. Twelve participants took part in the single-blind, randomised, crossover design study. Mental fatigue was induced by 90 min of the computer-based Continuous Performance Task AX version. Control treatment consisted of 90 min of watching emotionally neutral documentaries. Participants consequently completed countermovement jump, isometric leg extension and a 3-min all-out cycling tests. Results of repeated measures analysis of variance and paired t tests revealed no difference in any performance or physiological variable. Rating of perceived exertion tended to be greater when mentally fatigued (mental fatigue = 19 ± 1 vs control = 18 ± 1, p = 0.096, [Formula: see text] = .232) and intrinsic motivation reduced (mental fatigue = 11 ± 4 vs control = 13 ± 6, p = 0.063, d = 0.597) in the mental fatigue condition. Near identical responses in performance and physiological parameters between mental fatigue and control conditions suggest that peripheral mechanisms primarily regulate maximal anaerobic exercise. Whereas mental fatigue can negatively impact submaximal endurance exercise, it appears that explosive power, voluntary maximal strength and anaerobic work capacity are unaffected.

Performance outcomes and unwanted side effects associated with energy drinks.

Energy drinks are increasingly popular among athletes and others. Advertising for these products typically features images conjuring great muscle power and endurance; however, the scientific literature provides sparse evidence for an ergogenic role of energy drinks. Although the composition of energy drinks varies, most contain caffeine; carbohydrates, amino acids, herbs, and vitamins are other typical ingredients. This report analyzes the effects of energy drink ingredients on prolonged submaximal (endurance) exercise as well as on short-term strength and power (neuromuscular performance). It also analyzes the effects of energy drink ingredients on the fluid and electrolyte deficit during prolonged exercise. In several studies, energy drinks have been found to improve endurance performance, although the effects could be attributable to the caffeine and/or carbohydrate content. In contrast, fewer studies find an ergogenic effect of energy drinks on muscle strength and power. The existing data suggest that the caffeine dose given in studies of energy drinks is insufficient to enhance neuromuscular performance. Finally, it is unclear if energy drinks are the optimal vehicle to deliver caffeine when high doses are needed to improve neuromuscular performance.