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Purpose: To assess the effect of 2 work-matched efforts of different intensities on subsequent performance in well-trained cyclists., Methods: The present study followed a randomized controlled crossover design. Twelve competitive junior cyclists volunteered to participate (age, 17 [1] y; maximum oxygen uptake, 71.0 [4.7] mL·kg-1·min-1). The power-duration relationship was assessed through 2-minute, 5-minute, and 12-minute field tests under fresh conditions (control). On subsequent days and following a randomized order, participants repeated the aforementioned tests after 2 training sessions matched for mechanical work (∼15 kJ/kg) of different intensities (ie, a moderate-intensity continuous-training [60%-70% of critical power; CP] session or a session including high-intensity intervals [3-min repetition bouts at 110%-120% of the CP interspersed by 3-min rest periods])., Results: A significantly lower power output was found in the 2-minute test after the high-intensity training session compared not only with the control condition (-8%, P < .001) but also with the moderate-intensity continuous-training session (-7%, P = .003), with no significant differences between the latter conditions. No significant differences between conditions were found for the remaining tests. As a consequence, the high-intensity training session resulted in significantly lower W' values compared to both the control condition (-27%, P = .001) and the moderate-intensity continuous-training session (-26%, P = .012), with no differences between the 2 latter conditions and with no differences for CP., Conclusion: A session including high-intensity intermittent efforts induces a greater fatigue, particularly in short-duration efforts and W', than a work-matched continuous-training session of moderate intensity.

Purpose: The aim of this study was to assess the acute cardiorespiratory as well as muscle and cerebral tissue oxygenation responses to submaximal constant-load (CL) and high-intensity interval (HII) cycling exercise performed in normoxia and in hypoxia at similar intensity, reproducing whole-body endurance exercise training sessions as performed in sedentary and clinical populations., Methods: Healthy subjects performed two CL (30 min, 75% of maximal heart rate, n = 12) and two HII (15 times 1-min high-intensity exercise-1-min passive recovery, n = 12) cycling exercise sessions in normoxia and in hypoxia [mean arterial oxygen saturation 76 ± 1% (clamped) during CL and 77 ± 5% (inspiratory oxygen fraction 0.135) during HII]. Cardiorespiratory and near-infrared spectroscopy parameters as well as the rate of perceived exertion were continuously recorded., Results: Power output was 21 ± 11% and 15% (according to protocol design) lower in hypoxia compared to normoxia during CL and HII exercise sessions, respectively. Heart rate did not differ between normoxic and hypoxic exercise sessions, while minute ventilation was higher in hypoxia during HII exercise only (+ 13 ± 29%, p < 0.05). Quadriceps tissue saturation index did not differ significantly between normoxia and hypoxia (CL 60 ± 8% versus 59 ± 5%; HII 59 ± 10% versus 56 ± 9%; p > 0.05), while prefrontal cortex deoxygenation was significantly greater in hypoxia during both CL (66 ± 4% versus 56 ± 6%) and HII (58 ± 5% versus 55 ± 5%; p < 0.05) sessions. The rate of perceived exertion did not differ between normoxic and hypoxic CL (2.4 ± 1.7 versus 2.9 ± 1.8) and HII (6.9 ± 1.4 versus 7.5 ± 0.8) sessions (p > 0.05)., Conclusion: This study indicates that at identical heart rate, reducing arterial oxygen saturation near 75% does not accentuate muscle deoxygenation during both CL and HII exercise sessions compared to normoxia. Hence, within these conditions, larger muscle hypoxic stress should not be expected.

We hypothesized that prior exercise would attenuate the muscle fatigue accompanied by oxygen uptake slow-component (V̇O 2SC ) behavior during a subsequent very-heavy (VH)-intensity cycling exercise. Thirteen healthy male subjects performed tests to determine the critical power (CP) and the fixed amount of work above CP ([Formula: see text]) and performed 6 square-wave bouts until 3 or 8 min, each at a work rate set to deplete 70% [Formula: see text] in 8 min, with a maximal isokinetic effort before and after the conditions without (VH CON ) and with prior exercise (VH EXP ), to measure the cycling peak torque decrement. The V̇O 2SC magnitude at 3 min (VH CON = 0.280 ± 0.234, VH EXP = 0.116 ± 0.109 L·min -1 ; p = 0.04) and the V̇O 2SC trajectory were significantly lower for VH EXP (VH CON = 0.108 ± 0.042, VH EXP = 0.063 ± 0.031 L·min -2 ; p < 0.01), leading to a V̇O 2SC magnitude at the eighth minute that was significantly lower than VH CON (VH CON = 0.626 ± 0.296 L·min -1 , VH EXP = 0.337 ± 0.179; p < 0.01). Conversely, peak torque progressively decreased from pre-exercise to 3 min (Δtorque = 21.5 ± 7.7 vs. 19.6 ± 9.2 Nm) and to 8 min (Δtorque = 29.4 ± 15.8 vs. 27.5 ± 12.0 Nm) at VH CON and VH EXP , respectively, without significant differences between conditions. Regardless of the condition, there was a significant relationship between Δtorque and the V̇O 2SC (R 2 : VH CON = 0.23, VH EXP = 0.25; p = 0.01). Considering that "priming" effects on the V̇O 2SC were not accompanied by the muscle force behavior, these findings do not support the hypothesis of a "causal" relationship between the time-course of muscle fatigue and V̇O 2SC .

This study compared the responses of two priming exercises of similar fatigue on the adjustment of the oxygen uptake time constant (τV̇O 2 ) in cycling. Ten healthy young adults (25 ± 3 yr) performed: three step transitions from a 20-W baseline to the power output (PO) below the gas exchange threshold (MOD, MOD PRE ); a 3-min bout (P 3MIN ) at 90% of peak PO (PO peak ), followed by MOD (MOD 3MIN ); and a 6-min bout (P 6MIN ) at 80% of PO peak, followed by MOD (MOD 6MIN ). The O 2  supply-to-O 2 demand ([HHb]/V̇O 2 ) ratio was calculated for MOD PRE , MOD 3MIN , and MOD 6MIN . Neuromuscular fatigue was measured isometrically pre- and post-priming exercise. Reductions in maximal voluntary contraction (-29 ± 6 vs -34 ± 7%) and high-frequency doublet amplitude (-48 ± 13 vs -43 ± 11%) were not significantly different between P 3MIN vs P 6MIN , suggesting similar fatigue. τV̇O 2 for MOD 3MIN and MOD 6MIN were similar, being ~25% smaller than MOD PRE . The [HHb]/V̇O 2 ratio was significantly greater in MOD PRE (1.13 ± 0.12) compared to MOD 3MIN (1.02 ± 0.04) and MOD 6MIN (1.02 ± 0.04). This study showed that priming exercise of shorter duration and higher intensity, was sufficient to accelerate V̇O 2 kinetics similarly to that observed subsequent to P 6MIN when the muscle fatigue was similar.

Reductions in postprandial lipemia have been observed following aerobic exercise of sufficient energy expenditure. Increased excess postexercise oxygen consumption (EPOC) has been documented when comparing high- versus low-intensity exercise. The contribution of EPOC energy expenditure to alterations in postprandial lipemia has not been determined. The purpose of this study was to evaluate the effects of low- and high-intensity exercise on postprandial lipemia in healthy, sedentary, overweight and obese men (age, 43 ± 10 years; peak oxygen consumption, 31.1 ± 7.5 mL·kg -1 ·min -1 ; body mass index, 31.8 ± 4.5 kg/m 2 ) and to determine the contribution of EPOC to reductions in postprandial lipemia. Participants completed 4 conditions: nonexercise control, low-intensity exercise at 40%-50% oxygen uptake reserve (LI), high-intensity exercise at 70%-80% oxygen uptake reserve (HI), and HI plus EPOC re-feeding (HI+EERM), where the difference in EPOC energy expenditure between LI and HI was re-fed in the form of a sports nutrition bar (Premier Nutrition Corp., Emeryville, Calif., USA). Two hours following exercise participants ingested a high-fat (1010 kcals, 99 g sat fat) test meal. Blood samples were obtained before exercise, before the test meal, and at 2, 4, and 6 h postprandially. Triglyceride incremental area under the curve was significantly reduced following LI, HI, and HI+EERM when compared with nonexercise control (p < 0.05) with no differences between the exercise conditions (p > 0.05). In conclusions, prior LI and HI exercise equally attenuated postprandial triglyceride responses to the test meal. The extra energy expended during EPOC does not contribute significantly to exercise energy expenditure or to reductions in postprandial lipemia in overweight men.

Purpose: We aimed to identify a blood flow restriction (BFR) endurance exercise protocol that would both maximize cardiopulmonary and metabolic strain, and minimize the perception of effort., Methods: Twelve healthy males (23 ± 2 years, 75 ± 7 kg) performed five different exercise protocols in randomized order: HI, high-intensity exercise starting at 105% of the incremental peak power (P peak ); I-BFR30, intermittent BFR at 30% P peak ; C-BFR30, continuous BFR at 30% P peak ; CON30, control exercise without BFR at 30% P peak ; I-BFR0, intermittent BFR during unloaded exercise. Cardiopulmonary, gastrocnemius oxygenation (StO 2 ), capillary lactate ([La]), and perceived exertion (RPE) were measured., Results: V̇O 2 , ventilation (V̇ E ), heart rate (HR), [La] and RPE were greater in HI than all other protocols. However, muscle StO 2 was not different between HI (set1-57.8 ± 5.8; set2-58.1 ± 7.2%) and I-BRF30 (set1-59.4 ± 4.1; set2-60.5 ± 6.6%, p < 0.05). While physiologic responses were mostly similar between I-BFR30 and C-BFR30, [La] was greater in I-BFR30 (4.2 ± 1.1 vs. 2.6 ± 1.1 mmol L -1 , p = 0.014) and RPE was less (5.6 ± 2.1 and 7.4 ± 2.6; p = 0.014). I-BFR30 showed similar reduced muscle StO 2 compared with HI, and increased blood lactate compared to C-BFR30 exercise., Conclusion: Therefore, this study demonstrate that endurance cycling with intermittent BFR promotes muscle deoxygenation and metabolic strain, which may translate into increased endurance training adaptations while minimizing power output and RPE.

The aim of the present study was to investigate the effects of acute administration of taurine overload on time to exhaustion (TTE) of high-intensity running performance and alternative maximal accumulated oxygen deficit (MAODALT). The study design was a randomized, placebo-controlled, crossover design. Seventeen healthy male volunteers (age: 25 ± 6 years; maximal oxygen uptake: 50.5 ± 7.6 mL·kg(-1)·min(-1)) performed an incremental treadmill-running test until voluntary exhaustion to determine maximal oxygen uptake and exercise intensity at maximal oxygen uptake. Subsequently, participants completed randomly 2 bouts of supramaximal treadmill-running at 110% exercise intensity at maximal oxygen uptake until exhaustion (placebo (6 g dextrose) or taurine (6 g) supplementation), separated by 1 week. MAODALT was determined using a single supramaximal effort by summating the contribution of the phosphagen and glycolytic pathways. When comparing the results of the supramaximal trials (i.e., placebo and taurine conditions) no differences were observed for high-intensity running TTE (237.70 ± 66.00 and 277.30 ± 40.64 s; p = 0.44) and MAODALT (55.77 ± 8.22 and 55.06 ± 7.89 mL·kg(-1); p = 0.61), which seem to indicate trivial and unclear differences using the magnitude-based inferences approach, respectively. In conclusion, acute 6 g taurine supplementation before exercise did not substantially improve high-intensity running performance and showed an unclear effect on MAODALT.

Although exercise training has been demonstrated to have beneficial cardiovascular effects in diabetes, the effect of exercise training on hearts from obese/diabetic models is unclear. In the present study, mice were fed a high-fat diet, which led to obesity, reduced aerobic capacity, development of mild diastolic dysfunction, and impaired glucose tolerance. Following 8 wk on high-fat diet, mice were assigned to 5 weekly high-intensity interval training (HIT) sessions (10 × 4 min at 85-90% of maximum oxygen uptake) or remained sedentary for the next 10 constitutive weeks. HIT increased maximum oxygen uptake by 13%, reduced body weight by 16%, and improved systemic glucose homeostasis. Exercise training was found to normalize diastolic function, attenuate diet-induced changes in myocardial substrate utilization, and dampen cardiac reactive oxygen species content and fibrosis. These changes were accompanied by normalization of obesity-related impairment of mechanical efficiency due to a decrease in work-independent myocardial oxygen consumption. Finally, we found HIT to reduce infarct size by 47% in ex vivo hearts subjected to ischemia-reperfusion. This study therefore demonstrated for the first time that exercise training mediates cardioprotection following ischemia in diet-induced obese mice and that this was associated with oxygen-sparing effects. These findings highlight the importance of optimal myocardial energetics during ischemic stress., (Copyright © 2015 the American Physiological Society.)

Aim: To quantify the physiological demands and impact of muscle function t of the Fran workout, one of the most popular CrossFit benchmarks. Methods: Twenty experienced CrossFitters—16 male: 29 (6) years old and 4 female: 26 (5) years old— performed 3 rounds (with 30-s rests in between) of 21–21, 15–15, and 9–9 front squats to overhead press plus pull-up repetitions. Oxygen uptake and heart rate were measured at baseline, during the workout, and in the recovery period. Rating of perceived exertion, blood lactate, and glucose concentrations were assessed at rest, during the intervals, and in the recovery period. Muscular fatigue was also monitored at rest and at 5 minutes, 30 minutes, and 24 hours postexercise. Repeated-measures analysis of variance was performed to compare time points. Results: Aerobic (52%–29%) and anaerobic alactic (30%–23%) energy contributions decreased and the anaerobic lactic contribution increased (18%–48%) across the 3 rounds of the Fran workout. Countermovement jump height decreased by 8% (−12 to −3) mean change (95% CI), flight duration by 14% (−19 to −7), maximum velocity by 3% (−5 to −0.1), peak force 4% (−7 to −0.1), and physical performance (plank prone 47% [−54 to −38]) were observed. Conclusions: It appears that the Fran workout is a physically demanding activity that recruits energy from both aerobic and anaerobic systems. This severe-intensity workout evokes substantial postexercise fatigue and corresponding reduction in muscle function. [ABSTRACT FROM AUTHOR]

Hypoxia during supramaximal exercise reduces aerobic metabolism with a compensatory increase in anaerobic metabolism without affecting exercise performance. A similar response is elicited by preexercise voluntary hypocapnic hyperventilation, but it remains unclear whether hypocapnic hyperventilation and hypoxia additively reduce aerobic metabolism and increase anaerobic metabolism during supramaximal exercise. To address that issue, 12 healthy subjects (8 males and 4 females) performed the 30-second Wingate anaerobic test (WAnT) after (1) spontaneous breathing in normoxia (control, ∼21% fraction of inspired O2 [FiO2]), (2) voluntary hypocapnic hyperventilation in normoxia (hypocapnia, ∼21% FiO2), (3) spontaneous breathing in hypoxia (hypoxia, ∼11% FiO2), or (4) voluntary hypocapnic hyperventilation in hypoxia (combined, ∼11% FiO2). Mean power output during the 30-second WAnT was similar among the control (561 [133] W), hypocapnia (563 [140] W), hypoxia (558 [131] W), and combined (560 [133] W) trials (P =.778). Oxygen uptake during the 30-second WAnT was lower in the hypocapnia (1523 [318] mL/min), hypoxia (1567 [300] mL/min), and combined (1203 [318] mL/min) trials than in the control (1935 [250] mL/min) trial, and the uptake in the combined trial was lower than in the hypocapnia or hypoxia trial (all P <.001). Oxygen deficit, an index of anaerobic metabolism, was higher in the hypocapnia (38.4 [7.3] mL/kg), hypoxia (37.8 [6.8] mL/kg), and combined (40.7 [6.9] mL/kg) trials than in the control (35.0 [6.8] mL/kg) trial, and the debt was greater in the combined trial than in the hypocapnia or hypoxia trial (all P <.003). Our results suggest that voluntary hypocapnic hyperventilation and hypoxia additively reduce aerobic metabolism and increase anaerobic metabolism without affecting exercise performance during the 30-second WAnT. [ABSTRACT FROM AUTHOR]

Ice hockey is an intense team sport characterized by repeated bursts of fast‐paced skating, rapid changes in speed and direction and frequent physical encounters. These are performed in on‐ice shifts of ~30–80 s interspersed with longer sequences of passive recovery, resulting in about 15–25 min on‐ice time per player. Nearly 50% of the distance is covered at high‐intensity skating speeds and with an accentuated intense activity pattern in forwards compared to defensemen. During ice hockey match‐play, both aerobic and anaerobic energy systems are significantly challenged, with the heart rate increasing toward maximum levels during each shift, and with great reliance on both glycolytic and phosphagen ATP provision. The high‐intensity activity pattern favors muscle glycogen as fuel, leading to pronounced reductions despite the relatively brief playing time, including severe depletion of a substantial proportion of individual fast‐ and slow‐twitch fibers. Player‐tracking suggests that the ability to perform high‐intensity skating is compromised in the final stages of a game, which is supported by post‐game reductions in repeated‐sprint ability. Muscle glycogen degradation, in particular in individual fibers, as well as potential dehydration and hyperthermia, may be prime candidates implicated in exacerbated fatigue during the final stages of a game, whereas multiple factors likely interact to impair exercise tolerance during each shift. This includes pronounced PCr degradation, with potential inadequate resynthesis in a proportion of fast‐twitch fibers in situations of repeated intense actions. Finally, the recovery pattern is inadequately described, but seems less long‐lasting than in other team sports. [ABSTRACT FROM AUTHOR]

The favorable risk factor profiles and superb cardiac performance of elite long-distance runners, as well as the anti-aging effects of exercise, have likely contributed to the escalating number of adults worldwide who have embraced the notion that "more exercise is invariably better.≵ Nevertheless, vigorous-to-high-intensity physical activity (PA), particularly when unaccustomed, appears to be a trigger for acute cardiac events in individuals with known or occult atherosclerotic cardiovascular disease or structural cardiovascular abnormalities, most notably, hypertrophic cardiomyopathy. Although regular endurance exercise and moderate-to-vigorous PA provide established cardioprotective benefits, high-volume, high-intensity exercise training regimens appear to induce maladaptive cardiac remodeling in some individuals. These potential adverse cardiac adaptations include accelerated coronary artery calcification (CAC), elevated cardiac biomarker release, myocardial fibrosis, and atrial fibrillation (AF), which may be described by a reverse J-shaped curve. However, the risk for acute cardiovascular events is lower in fit/active persons compared to their unfit/inactive counterparts with the same CAC scores. Similarly, the risk of AF is the highest in habitually sedentary older adults, decreases with light-to-moderate intensity regular PA but increases with high-volume, high-intensity exercise regimens (i.e., reverse J-shaped curve). This review examines these relations and more, with specific reference to the World Health Organization exercise intensity and duration recommendations for optimal health, as well as the thresholds for other research-based exercise metrics, including steps/day and the concept of metabolic equivalents-minutes/week. The primary beneficiaries of exercise training programs and long-term goal training intensities, based on age, sex, and "good≵ fitness, are also discussed. In summary, the benefits of regular moderate-to-vigorous PA and the associated improvements in cardiorespiratory fitness far outweigh the risks for most individuals. [ABSTRACT FROM AUTHOR]

The accumulation of lactate in muscle and blood during high-intensity exercise is negatively correlated with the duration exercise can be sustained. Removal of lactate is a key component of acute recovery between consecutive bouts of such exercise. Low-intensity exercise enhances recovery by accelerating lactate turnover in metabolically active tissues, largely mediated by blood flow to these tissues. Therefore, the purpose of this research was to clarify if L-citrulline, a nutritional supplement purported to promote vasodilation via enhanced nitric oxide availability, would augment the removal of blood lactate during active recovery (AR). L-citrulline ingestion will augment the rate of blood lactate concentration decrease during AR, reduce the oxygen-cost of submaximal exercise, and increase time-to-exhaustion and peak oxygen uptake (V̇O2peak) during a test of maximal aerobic power. Healthy university students (five males & five females) participated in this double-blind, randomized, placebo-controlled study. Participants exercised on a cycle ergometer at submaximal steady-state intensities followed by progressively increasing intensity to exhaustion, 10 min of AR, and then supramaximal intensity exercise to exhaustion. Oxygen uptake was measured throughout the trial and blood lactate was sampled repeatedly during AR. The protocol elicited very high peak blood lactate concentrations after exercise (11.3 + 1.3 mmol/L). L-citrulline supplementation did not significantly alter blood lactate kinetics during AR, the oxygen cost of exercise, V̇O2peak, or time-to-exhaustion. Despite a strong theoretical basis by which L-citrulline could augment lactate removal from the blood, L-citrulline supplementation showed no effect as an exercise-recovery supplement. [ABSTRACT FROM AUTHOR]

Zandona, BA, Ramos, RA, de Oliveira, CdS, McAnulty, SR, Ferreira, LHB, Smolarek, AC, Enes, AAN, Urbinati, KMdSS, Aragon, AA, Schoenfeld, BJ, and de Souza Junior, TP. Reduced Dose of Beta-Alanine Is Sufficient to Maintain Performance in Repeated Sprints. J Strength Cond Res 36(6): 1636–1642, 2022—Beta-alanine (BA) supplementation has been shown to be effective in improving physical performance by increasing carnosine concentration. However, it is still necessary to know the effect of a maintenance dose on performance. Thus, this study aimed to investigate the effects of a maintenance dose of BA supplementation on performance. Forty-four anaerobically trained men with 23.9 ± 3.8 years of age, 176.0 ± 0.05 cm height, 81.2 ± 7.5 kg body mass, and 15.5 ± 2.9% of body fat performed a cycle ergometer test consisting of 4 sprints of 30 s with 4 minutes of active recovery. The study comprised 3 phases: (a) presupplementation, (b) supplementation with 6.4 g·d−1 BA or placebo, and (c) postsupplementation with a maintenance dose of 1.2 g·d−1 of BA or interruption of supplementation. Data were analyzed using generalized estimated equations with a priori 0.05 level of significance. The placebo group and interruption group presented a lower power (7.28 ± 0.66 and 7.71 ± 0.42 W·kg−1 vs. 8.04 ± 0.84 and 9.25 ± 1.18 W·kg−1, respectively; p < 0.05) during the third sprint in postsupplementation, whereas the maintenance group maintained the required power (7.47 ± 1.03 vs. 8.74 ± 1.07 W·kg−1; p > 0.05). The placebo group also presented higher percentage of fatigue (44.5% ± 12.3 and 44.8% ± 7.7 vs. 37.6 ± 7.2%; p = 0.021) and higher subjective perception of exertion (8.92 ± 0.90 vs. 8.00 ± 1.60; p = 0.028). Therefore, the maintenance dose of 1.2 g·d−1 BA was effective in maintaining performance, whereas a reduction in performance was observed after supplementation interruption. [ABSTRACT FROM AUTHOR]

Purpose: To compare psychophysiological responses to 6 repeated-sprint sessions in normobaric hypoxia (RSH) and normoxia (RSN) in team-sport athletes during a 2-wk "live high-train low" training camp. Methods: While residing under normobaric hypoxia (≥14 h/d, FiO2 14.5-14.2%), 23 lowland elite field hockey players performed, in addition to their usual training, 6 sessions (4 x 5 x 5-s maximal sprints, 25-s passive recovery, 5 min rest) under either RSH (FiO2 ~14.5%) or RSN (FiO2 21%). Sprint 1 and 5 times, physiological strain (heart rate [HR], arterial oxyhemoglobin saturation [SpO2]), and perceptual responses (overall peripheral discomfort, difficulty breathing, and lower-limb discomfort) were monitored. Results: During the 1st session, HR increased across sets (P < .001) independently of the conditions, while SpO2 was globally lower (P < .001) for RSH (averaged value: 91.9% ± 1.2%) vs RSN (96.9% ± 0.6%). Thereafter, SpO2 and HR remained similar across sessions for each condition. While 1st-sprint time remained similar, last-sprint time and fatigue index significantly decreased across sets (P < .01) and sessions (P < .05) but not between conditions. Ratings of overall perceived discomfort, difficulty breathing, and lower-limb discomfort were higher (P < .05) in RSH vs RSN at the 1st session. During subsequent sessions, values for overall perceived discomfort (time [P < .001] and condition [P < .05] effects), difficulty breathing (time effect; P < .001), and lower-limb discomfort (condition [P < .001] and interaction [P < .05] effects) decreased to a larger extent in RSH vs RSN. Conclusion: Despite higher hypoxia-induced physiological and perceptual strain during the 1st session, perceptual responses improved thereafter in RSH so as not to differ from RSN. This indicates an effective acclimation and tolerance to this innovative training. [ABSTRACT FROM AUTHOR]

The present study aimed to examine the profile of energy metabolism during repetition sprint exercises with different rest durations. Nine competitive male track and field athletes performed a submaximal-intensity increment exercise and 4 kinds of 2 consecutive 30-s sprints tests with rest durations of 4, 10, 15, and 20 min, respectively. The mean power output during these sprints was evaluated as the average value over the entire 30-s period. Aerobic and anaerobic energy during these sprints was determined from the extrapolated linear regression between power and the steady-state O2 uptake obtained during the submaximal-intensity increment exercise. During 2nd sprints compared with 1st sprints in the respective tests, the mean power output decreased significantly in the tests with rest durations of 4, 10, and 15 min; in all the tests, the aerobic energy increased significantly and the anaerobic energy decreased significantly. These results suggest that the 1st sprint in a repetition sprint exercise causes activation of aerobic metabolism and inhibition of anaerobic metabolism during the 2nd sprint. On the other hand, it is also suggested that recovery of anaerobic metabolism after the 1st sprint requires a longer rest duration than that for recovery of performance in the repetition sprint exercise. [ABSTRACT FROM AUTHOR]

The cognitive effects of acute aerobic exercise were investigated in endurance-trained individuals. On two occasions, 21 cyclists; 11 male (VO2max: 57 ± 9 mL·kg−1·min−1) and 10 female (VO2max: 51 ± 9 mL·kg−1·min−1), completed 45 min of fixed, moderate-intensity (discontinuous) cycling followed by an incremental ride to exhaustion. Cognitive function was assessed at Baseline, after 15 and 45 min of exercise (15EX and 45EX) and at Exhaustion using a 4-Choice Reaction Time (CRT) test and the Stroop test (Incongruent and Congruent Reaction Time [RT]). A sham capsule was administered on one occasion to determine whether the cognitive response to exercise was robust to the influence of a placebo. CRT, Congruent RT and Incongruent RT decreased (improved) at 15EX, 45EX and Exhaustion compared to Baseline (p's<0.005). While CRT and Congruent RT were faster at 45EX than 15EX (p's<0.020), Incongruent RT was not (p= 1.000). The sham treatment did not affect cognition. When performed at a moderate-intensity, longer duration exercise (up to 45 min) may improve cognition to a greater extent than shorter duration exercise; however, the magnitude of improvement appears to decrease with increasing task complexity. HI/EE performed following a sustained bout of dehydrating activity may not impair cognition. [ABSTRACT FROM AUTHOR]

The optimal exercise intensity and modality for maximizing cerebral blood flow (CBF) and hence potential exposure to positive, hemodynamically derived cerebral adaptations is yet to be fully determined. This study compared CBF velocity responses between running and cycling across a range of exercise intensities. Twenty‐six participants (12 females; age: 26 ± 8 years) completed four exercise sessions; two mode‐specific maximal oxygen consumption (VO2max) tests, followed by (order randomized) two incremental exercise protocols (3‐min stages at 35%, 50%, 65%, 80%, 95% VO2max). Continuous measures of middle cerebral artery velocity (MCAv), oxygen consumption, end‐tidal CO2 (PETCO2), and heart rate were obtained. Modality‐specific MCAv changes were observed for the whole group (interaction effect: p =.01). Exercise‐induced increases in MCAvmean during cycling followed an inverted‐U pattern, peaking at 65% VO2max (Δ12 ± 7 cm/s from rest), whereas MCAvmean during running increased linearly up to 95% VO2max (change from rest: Δ12 ± 13 vs. Δ7 ± 8 cm/s for running vs. cycling at 95% VO2max; p =.01). In contrast, both modalities had an inverted‐U pattern for PETCO2 changes, although peaked at different intensities (running: 50% VO2max, Δ6 ± 2 mmHg; cycling: 65% VO2max, Δ7 ± 2 mmHg; interaction effect: p =.01). Further subgroup analysis revealed that the running‐specific linear MCAvmean response was fitness dependent (Fitness*modality*intensity interaction effect: p =.04). Above 65% VO2max, fitter participants (n = 16; male > 45 mL/min/kg and female > 40 mL/min/kg) increased MCAvmean up to 95% VO2max, whereas in unfit participants (n = 7, male < mL/min/kg and female < 35 mL/min/kg) MCAvmean returned toward resting values. Findings demonstrate that modality‐ and fitness‐specific profiles for MCAvmean are seen at exercise intensities exceeding 65% VO2max. [ABSTRACT FROM AUTHOR]

This study examined the acute performance, cardiovascular and local muscular responses to perceived exertion-based high-intensity interval exercise using either double- or single-leg cycling. Fifteen healthy middle-aged adults completed, on separate occasions, ten 30-s double-leg intervals interspersed with 60 s passive recovery and twenty (ten with each leg) 30-s single-leg intervals interspersed with 60 s passive recovery. Impedance cardiography, blood pressure, muscle oxygenation and total haemoglobin content (near-infrared spectroscopy), oxygen consumption and power output were measured throughout each session. Normalised to the lean mass used during each trial, single-leg cycling resulted in lower power output (single-leg: 8.92 ± 1.74 W kg−1 and double-leg: 10.41 ± 3.22 W kg−1; p < 0.05) but greater oxygen consumption (single-leg: 103 ± 11 mL kg−1 min−1 and double-leg: 84 ± 21 mL kg−1 min−1; p < 0.01) and cardiac output (single-leg: 1407 ± 334 mL kg−1 min−1 and double-leg: 850 ± 222 mL kg−1 min−1; p < 0.01), compared with double-leg cycling. Mean arterial pressure (double-leg: 108 ± 11 mmHg and single-leg: 102 ± 10 mmHg), change in total haemoglobin content (double-leg: 8.76 ± 10.65 µM cm s−1 and single-leg: 13.42 ± 4.10 µM cm s−1) and change in tissue oxygenation index (double-leg: −4.51 ± 3.56% and single-leg: −3.97 ± 3.91%) were not different between double-leg and single-leg cycling. When compared to double-leg cycling, single-leg cycling elicited a higher cardiac output relative to the lean mass, but this did not result in greater power output. The dissociation between blood availability and power output is consistent with an ageing model characterised by a decrease in local oxygen delivery and distribution capability. [ABSTRACT FROM AUTHOR]

The O2-kinetic response to constant work rate exercise provides an insight into the adjustment of systemic oxygen transport and muscle metabolism. Whether O2-kinetics measured in laboratory conditions reflect O2-kinetics in field conditions has not yet been analysed. The aim of this study was to compare O2-kinetics between field and laboratory conditions. Thirteen competitive male cyclists (mean±SD age 23.3±4.1 years; V̇O2peak 68.2±4.7 mL. min−1. kg−1) completed two 6-min severe-intensity trials at 60 and 90 rev. min−1 in both conditions. Power output was measured with an SRM power meter and V̇O2 was measured with a portable gas analyser. The time constant (τ), the time delay (TD) and the amplitude (Amp) were resolved by least square regression, and the V̇O2 slow component (SC) was calculated as the difference between the end-exercise V̇O2 and Amp. To determine differences between the trials, a repeated-measure ANOVA was conducted. The Amp and end-exercise V̇O2 were significantly higher during field cycling whereas the SC were significantly higher during laboratory cycling (all at p<0.001). No significant differences were found for τ (p=0.24). Laboratory measures tend to underestimate the oxygen demand in field cycling. A higher cadence leads to greater oxygen demand in laboratory and field cycling. [ABSTRACT FROM AUTHOR]

Introduction: Leg order during sequential single-leg cycling (i.e., exercising both legs independently within a single session) may affect local muscular responses potentially influencing adaptations. This study examined the cardiovascular and skeletal muscle hemodynamic responses during double-leg and sequential single-leg cycling. Methods: Ten young healthy adults (28 ± 6 yr) completed six 1-min double-leg intervals interspersed with 1 min of passive recovery and, on a separate occasion, 12 (six with one leg followed by six with the other leg) 1-min single-leg intervals interspersed with 1 min of passive recovery. Oxygen consumption, heart rate, blood pressure, muscle oxygenation, muscle blood volume, and power output were measured throughout each session. Results: Oxygen consumption, heart rate, and power output were not different between sets of single-leg intervals, but the average of both sets was lower than the double-leg intervals. Mean arterial pressure was higher during double-leg compared with sequential single-leg intervals (115 ± 9 vs 104 ± 9 mm Hg, P < 0.05) and higher during the initial compared with second set of single-leg intervals (108 ± 10 vs 101 ± 10 mm Hg, P < 0.05). The increase in muscle blood volume from baseline was similar between the active single leg and the double leg (267 ± 150 vs 214 ± 169 μM·cm, P = 0.26). The pattern of change in muscle blood volume from the initial to second set of intervals was significantly different (P < 0.05) when the leg was active in the initial (−52.3% ± 111.6%) compared with second set (65.1% ± 152.9%). Conclusions: These data indicate that the order in which each leg performs sequential single-leg cycling influences the local hemodynamic responses, with the inactive muscle influencing the stimulus experienced by the contralateral leg. [ABSTRACT FROM AUTHOR]

The purpose of the study was to examine the effects of altering from habitual mixed Western-based (HD) to a very low- carbohydrate high-fat (VLCHF) diet over a 4-week timecourse on performance and physiological responses during high-intensity interval training (HIIT). Eighteen moderately trained males (age 23.8 ± 2.1 years) consuming their HD (48 ± 13% carbohydrate, 17 ± 3% protein, 35 ± 9% fat) were assigned to 2 groups. One group was asked to remain on their HD, while the other was asked to switch to a non-standardized VLCHF diet (8 ± 3% carbohy- drate, 29 ± 15% protein, 63 ± 13% fat) for 4 weeks. Participants performed graded exercise tests (GXT) before and after the ex- periment, and an HIIT session (5x3min, work/rest 2:1, passive re- covery, total time 34min) before, and after 2 and 4 weeks. Heart rate (HR), oxygen uptake (... O2), respiratory exchange ratio (RER), maximal fat oxidation rates (Fatmax) and blood lactate were measured. Total time to exhaustion (TTE) and maximal O2 (...O2max) in the GXT increased in both groups, but between-group changes were trivial (ES ± 90% CI: -0.1 ± 0.3) and small (0.57 ± 0.5), respectively. Between-group difference in Fatmax change (VLCHF: 0.8 ± 0.3 to 1.1 ± 0.2 g/min; HD: 0.7 ± 0.2 to 0.8 ± 0.2 g/min) was large (1.2±0.9), revealing greater increases in the VLCHF versus HD group. Between-group comparisons of mean changes in VO2 and HR during the HIIT sessions were trivial to small, whereas mean RER decreased more in the VLCHF group (-1.5 ± 0.1). Lactate changes between groups were unclear. Adoption of a VLCHF diet over 4 weeks increased Fatmax and did not adversely affect TTE during the GXT or cardiorespiratory re- sponses to HIIT compared with the HD. [ABSTRACT FROM AUTHOR]

The present study aimed to analyze and compare the effects of four different interval-training protocols on aerobic fitness and muscle strength. Thirty-seven subjects (23.8 ± 4 years; 171.7 ± 9.5 cm; 70 ± 11 kg) were assigned to one of four groups: low-intensity interval training with ( BFR, n = 10) or without ( LOW, n = 7) blood flow restriction, high-intensity interval training ( HIT, n = 10), and combined HIT and BFR ( BFR + HIT, n = 10, every session performed 50% as BFR and 50% as HIT). Before and after 4 weeks training (3 days a week), the maximal oxygen uptake ( VO2max), maximal power output ( Pmax), onset blood lactate accumulation ( OBLA), and muscle strength were measured for all subjects. All training groups were able to improve OBLA ( BFR, 16%; HIT, 25%; HIT + BFR, 22%; LOW, 6%), with no difference between groups. However, VO2max and Pmax improved only for BFR (6%, 12%), HIT (9%, 15%) and HIT + BFR (6%, 11%), with no difference between groups. Muscle strength gains were only observed after BFR training (11%). This study demonstrates the advantage of short-term low-intensity interval BFR training as the single mode of training able to simultaneously improve aerobic fitness and muscular strength. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare heart rate variability (HRV) recovery after two iso-volume (5 km) exercises performed at different intensities. 14 subjects volunteered (25.17±5.08 years; 74.7±6.28kg; 175±0.05cm; 59.56±5.15ml⋅kg-1⋅min-1) and after determination of peak oxygen uptake (VO2Peak) and the speed associated with VO2Peak (sVO2Peak), the subjects completed 2 random experimental trials: high-intensity exercise (HIE - 1:1 at 100% sVO2Peak), and moderate-intensity continuous exercise (MIE - 70% sVO2Peak). HRV and RR intervals were monitored before, during and after the exercise sessions together with, the HRV analysis in the frequency domains (high-frequency - HF: 0.15 to 0.4 Hz and low-frequency - LF: 0.04 to 0.15 Hz components) and the ratio between them (LF/HF). Statistical analysis comparisons between moments and between HIE and MIE were performed using a mixed model. Both exercise sessions modified LFlog, HFlog, and LF/HF (F = 16.54, F = 19.32 and F = 5.17, p<0.05, respectively). A group effect was also found for LFlog(F = 23.91,p<0.05), and HFlog(F = 57.55,p< 0.05). LF/HF returned to resting value 15min after MIE exercise and 20min after HIE exercise. This means that the heavy domain (aerobic and anaerobic threshold) induces dissimilar autonomic modification in physically active subjects. Both HIE and MIE modify HRV, and generally HIE delays parasympathetic autonomic modulation recovery after iso-volume exercise. [ABSTRACT FROM AUTHOR]

Purpose: This study determined the effects of pre-exercise sodium bicarbonate ingestion (ALK) on changes in oxygen uptake (VO2) at the end of a supramaximal exercise test (SXT).Methods: Eleven well-trained cyclists completed a 70-s all-out cycling effort, in double-blind trials, after oral ingestion of either 0.3 g kg(-1) of sodium bicarbonate (NaHCO3) or 0.2 g kg(-1) body mass of calcium carbonate (PLA). Blood samples were taken to assess changes in acid-base balance before the start of the supramaximal exercise, and 0, 5 and 8 min after the exercise; ventilatory parameters were also measured at rest and during the SXT.Results: At the end of the PLA trial, which induced mild acidosis (blood pH = 7.20), subjects presented a significant decrease in VO2 (P < 0.05), which was related to the amplitude of the decrease in minute ventilation (VE) during the SXT (r = 0.70, P < 0.01, n = 11). Pre-exercise metabolic alkalosis significantly prevented the exercise-induced decrease in VO2 in eleven well-trained participants (PLA:12.5 ± 2.1 % and ALK: 4.9 ± 0.9 %, P < 0.05) and the decrease in mean power output was significantly less pronounced in ALK (P < 0.05). Changes in the VO2 decrease between PLA and ALK trials were positively related to changes in the VE decrease (r = 0.74, P < 0.001), but not to changes in power output (P > 0.05).Conclusions: Pre-exercise alkalosis counteracted the VO2 decrease related to mild acidosis, potentially as a result of changes in VE and in muscle acid-base status during the all-out supramaximal exercise. [ABSTRACT FROM AUTHOR]

Purpose: The slow component of O2 uptake (VO2sc) represents a progressive decline in work efficiency during strenuous, constant work rate cycling. Although most of this “excess” O2 uptake can be explained by factors intrinsic to the exercising muscles, it has been proposed that respiratory muscle work rate may also contribute to the VO2sc response. To date, however, no study has provided a comprehensive analysis of the mechanical power of breathing (Pb) in relation to the VO2sc while performing strenuous exercise. Methods: The mechanical Pb was measured in 12 recreational cyclists (24 ± 1 yr, 70.9 ± 3.9 kg) during heavy- and severe-intensity cycling. The resistive and elastic components of Pb were quantified using the modified Campbell diagram. Results: Total Pb significantly increased (P < 0.05) over the VO2sc phase during both heavy (Δ13 ± 2 J•min−1) and severe work rate transitions (Δ219 ± 56 J•min−1). The magnitude of this increase was relatively greater during severe cycling trials (P < 0.05). The greater “slow component” rise in total Pb during severe work rate transitions was consequent to relatively larger increases in the inspiratoiy and expiratory resistive Pb and inspiratory elastic Pb (P < 0.05). Conclusions: The findings of this investigation support the thesis that the energetic contribution from respiratory muscles to the VO2sc amplitude is disproportionately higher during severe- compared with that during heavy-intensity exercise. [ABSTRACT FROM AUTHOR]

High-intensity intermittent exercise induces physiological adaptations similar to energy-matched continuous exercise, but the comparative appetite and energy balance responses are unknown. Twelve healthy males (mean ± SD: age, 22 ± 3 years; body mass index, 23.7 ± 3.0 kg·m−2; maximum oxygen uptake, 52.4 ± 7.1 mL·kg−1·min−1) completed three 8 h trials (control, steady-state exercise (SSE), high-intensity intermittent exercise (HIIE)) separated by 1 week. Trials commenced upon completion of a standardized breakfast. Exercise was performed from hour 2 to hour 3. In SSE, 60 min of cycling at 59.5% ± 1.6% of maximum oxygen uptake was performed. In HIIE, ten 4-min cycling intervals were completed at 85.8% ± 4.0% of maximum oxygen uptake, with a 2-min rest between each interval. A standardized lunch and an ad libitum afternoon meal were provided at hours 3.75 and 7, respectively. Appetite ratings and peptide YY3-36 concentrations were measured throughout each trial. Appetite was acutely suppressed during exercise, but more so during HIIE ( p < 0.05). Peptide YY3-36 concentrations increased significantly upon cessation of exercise in SSE ( p = 0.002), but were highest in the hours after exercise in HIIE ( p = 0.05). Exercise energy expenditure was not different between HIIE and SSE ( p = 0.649), but perceived exertion was higher in HIIE ( p < 0.0005). Ad libitum energy intake did not differ between trials ( p = 0.833). Therefore, relative energy intake (energy intake minus the net energy expenditure of exercise) was lower in the SSE and HIIE trials than in the control trial (control, 4759 ± 1268 kJ; SSE, 2362 ± 1224 kJ; HIIE, 2523 ± 1402 kJ; p < 0.0005). An acute bout of energy-matched continuous exercise and HIIE were equally effective at inducing an energy deficit without stimulating compensatory increases in appetite. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to compare sexes for time to fatigue at 100% VO2peak in recreationally trained individuals. Ten men (age: 23.4 ± 1.8; height: 177 ± 6.7; body mass: 83.8 ± 11.3; ± SD) and nine women (age: 25.0 ± 2.5; height: 165.6 ± 5.5; body mass: 62.7 ± 6.7) participated in this investigation after providing written consent. One week after assessing VO2peak, subjects exercised on an electrically braked cycle ergometer at 100% of VO2peak until fatigue. The time taken to fatigue was 48.9% longer for men than women (274 ± 13s vs. 184 ± 14s;p< 0.001, for men and women, respectively). When normalized for fat free mass (ffm; s/kg ffm) no significant differences between men and women were observed (3.99 ± 0.21s/kg ffm vs. 3.72 ± 0.28s/kg ffm for men and women, respectively,p = 0.431). The difference in fatigability between the sexes at this exercise intensity is to a large degree related to the difference in fat free mass. [ABSTRACT FROM PUBLISHER]

Venepuncture is the established "gold standard" for sampling cortisol, but it is expensive, highly invasive and impractical for many experimental and clinical settings. Salivary free cortisol is a non-invasive and practical alternative; however, when cortisol concentrations exceed 500 nmol • L there is a lack of agreement between salivary (free) and venous (bound) cortisol. No known research has assessed whether capillary cortisol accurately reflects venous blood cortisol across a range of concentrations. The objective of the current study was to determine the agreement between capillary and venous blood samples of total plasma cortisol across a range of concentrations. 11 healthy male subjects (26.1 ± 5.3 years) were recruited. Capillary and venous blood samples were collected pre and post (immediately post and post 5, 10, 15 and 20 min) a treadmill VO2max test. Regression analysis revealed a strong relationship (R2 = 0.96, y = 1.0028x+1.2964 (P < 0.05)) between capillary and venous cortisol concentrations. A Bland-Altman plot showed all data was within the upper and lower bounds of the 95 % confidence interval, and no systematic bias was evident. In conclusion, capillary sampling is a valid technique for measuring bound cortisol across a range of concentrations. [ABSTRACT FROM AUTHOR]

Amateur wrestling at the high school and collegiate level in the United States often involves exercise and thermal dehydration as well as food and fluid restriction to "make weight". Available evidence suggests this is the opposite of what is optimal for high-intensity exercise performance. A high-intensity taper will substantially improve performance when conducted after a period of high-volume high intensity training. Additionally, dehydration of ~3-4% of body weight will most definitely impair muscular endurance during high-intensity exercise although it likely will not impair maximal muscular strength or power. Even more gradual weight loss practices over a few days, which result in a reduction of body weight by ~3.3 to 6% will result in impaired performance as assessed by wrestling specific tests. It would seem of paramount importance for wrestlers to maintain a high-carbohydrate diet of -8-10g carbohydrate/kg body weight/day to maintain training intensity and optimize performance during individual matches and tournaments. Thus, the evidence would suggest that, prior to competition, collegiate wrestlers should be: 1 ) tapered, 2) in the euhydrated state, and 3) have ingested a high carbohydrate diet, rather than undergo rapid weight loss prior to competition. [ABSTRACT FROM AUTHOR]

It has frequently been demonstrated that prior high-intensity exercise facilitates pulmonary oxygen uptake [Formula: see text] response at the onset of subsequent identical exercise. To clarify the roles of central O(2) delivery and/or peripheral O(2) extraction in determining this phenomenon, we investigated the relative contributions of cardiac output (CO) and arteriovenous O(2) content difference [Formula: see text] to the [Formula: see text] transient during repeated bouts of high-intensity knee extension (KE) exercise. Nine healthy subjects volunteered to participate in this study. The protocol consisted of two consecutive 6-min KE exercise bouts in a supine position (work rate 70-75% of peak power) separated by 6 min of rest. Throughout the protocol, continuous-wave Doppler ultrasound was used to measure beat-by-beat CO (i.e., via simultaneous measurement of stroke volume and the diameter of the arterial aorta). The phase II [Formula: see text] response was significantly faster and the slow component (phase III) was significantly attenuated during the second KE bout compared to the first. This was a result of increased CO during the first 30 s of exercise: CO contributing to 100 and 56% of the [Formula: see text] speeding at 10 and 30 s, respectively. After this, the contribution of [Formula: see text] became increasingly more predominant: being responsible to an estimated 64% of the [Formula: see text] speeding at 90 s, which rose to 100% by 180 s. This suggests that, while both CO and [Formula: see text] clearly interact to determine the [Formula: see text] response, the speeding of [Formula: see text] kinetics by prior high-intensity KE exercise is predominantly attributable to increases in [Formula: see text]. [ABSTRACT FROM AUTHOR]