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Durability, or resilience to deteriorations in physiological endurance characteristics during exercise, is posited to have important implications for endurance performance. However, little is known about the effects of exercise intensity on the durability of important endurance parameters. The aim of this study was to compare changes in peak ramp power (power achieved at the end of a ramp test), V˙$\\dot{\\mathrm{V}}$ O2max, lactate threshold, critical power, gross efficiency and W′ after work‐matched moderate and heavy exercise bouts. Twelve competitive cyclists (V˙$\\dot{\\mathrm{V}}$ O2max = 62.1 ± 4.4 mL·kg−1 min−1) performed exercise testing before and after completing 15 kJ·kg−1 work bouts in the moderate (duration = 4837 ± 675 s) and heavy (4000 ± 537 s) exercise domain. Significant declines were seen in peak ramp power (baseline = 412.6 ± 64.5 W, moderate = 380.2 ± 59.7 W and heavy = 374.8 ± 59 W) and W’ (baseline = 7.8 ± 4 kJ, moderate = 4 ± 3.6 kJ and heavy = 3.6 ± 2.4 kJ)—all other parameters did not change. There were no significant differences in the magnitude of decline between the moderate and heavy work bouts for any variable. For the first time, we show that durability of important determinants of endurance performance is not different when 15 kJ·kg−1 of moderate or heavy work is performed, suggesting that exercise domain does not influence durability for exercise lasting ∼60–90 min. Further research is needed to explore exercise of longer durations and associated physiological mechanisms for deteriorations in relevant parameters. Highlights This is the first study to explore laboratory measured changes in all the primary physiological determinants of endurance cycling (i.e., durability) after work‐matched prior exercise in the moderate and heavy domains. We found that the exercise domain did not affect durability of peak ramp power, V˙$\\dot{\\mathrm{V}}$ O2max, lactate threshold, economy, critical power or W’. Peak ramp power and W′ were the only variables to significantly decline after prior exercise. Coaches and practitioners should be aware that as little as 15 kJ·kg−1 work in the moderate and heavy exercise domain can reduce peak ramp power and W′, which could affect performance and training intensity.

The effect of exercise‐induced muscle damage (EIMD) on three‐dimensional side cut biomechanics and task achievement were assessed in 16 team sport athletes (eight males and eight females) who completed 45° side cuts before and 48 h after multidirectional running. Angular displacement and joint moments of the hip and knee, and GRF impulse (IGRF) during five successful trials of a 45° side cut, were collected using a 3D motion capture system and force platform at both timepoints. At 48 h, participants had more knee internal rotation (p = 0.009), knee abduction ROM (p = 0.002), lower peak knee extensor moment (p = 0.001) and a higher hip‐knee extensor ratio moment (p = 0.020). Large increases in IGRF at 48 h in females (d; ± 95% CI: 1.4; ± 1.4, p = 0.037) suggest a less effective deceleration capacity. Whilst EIMD had no effect on side cut task achievement and sagittal kinematics, EIMD caused participants to shift the extensor demands away from the knee and towards the hip to decelerate the body. Practitioners should be mindful of potential increases in frontal and transverse motions at the knee for athletes with EIMD, which might have implications for strategies to reduce injury risk. Highlights Multidirectional running mimicking the movement demands of team sport activity offers an ecologically valid model to study EIMD. Whilst task achievement and sagittal side cut kinematics were not affected by EIMD, some impairment to transverse and frontal knee kinematics during a side cut were observed, which could have implications for ACL injury risk. EIMD caused participants to shift the extensor demands away from the knee and towards the hip during side cutting and caused a less effective deceleration capacity in females.

The purpose of the study was to compare measures of energy expenditure derived from indirect calorimetry and micro-technology, as well as high power and high speed activity during linear and multi-directional running. Repeated measures. Twelve university standard team sport players completed a linear and multi-directional running condition. Estimated energy expenditure, as well as time at high speed (>14.4kmh−1) and high power (>20Wkg−1) were quantified using a 10Hz micro-technology device and compared with energy expenditure derived from indirect calorimetry. Measured energy expenditure was higher during the multi-directional condition (9.0±2.0 cf. 5.9±1.4kcalmin−1), whereas estimated energy expenditure was higher during the linear condition (8.7±2.1 cf. 6.5±1.5kcalmin−1). Whilst measures of energy expenditure were strongly related (r>0.89, p<0.001), metabolic power underestimated energy expenditure by 52% (95% LoA: 20–93%) and 34% (95% LoA: 12–59%) during the multi-directional and linear condition, respectively. Time at high power was 41% (95% LoA: 4–92%) greater than time at high speed during the multi-directional condition, whereas time at high power was 5% (95% LoA: −17–9%) lower than time at high speed during the linear condition. Estimated energy expenditure and time at high metabolic power can reflect changes in internal load. However, micro-technology cannot be used to determine the energy cost of intermittent running.

With the advancements in player tracking technology, the topic of fatigue and pacing in team sport has become increasingly popular in recent years. Initially based upon a pre-conceived pacing schema, a central metabolic control system is proposed to guide the movement of players during team sport matches, which can be consciously modified based on afferent signals from the various physiological systems and in response to environmental cues. On the basis of this theory, coupled with the collective findings from motion-analysis research, we sought to define the different pacing strategies employed by team sport players. Whole-match players adopt a ‘slow-positive’ pacing profile (gradual decline in total running intensity), which appears to be global across the different team sports. High-intensity movement also declines in a ‘slow-positive’ manner across most team sport matches. The duration of the exercise bout appears to be important for the selected exercise intensity, with the first introduction to a match as a substitute or interchange player resulting in a ‘one bout, all out’ strategy. In a limited interchange environment, a second introduction to the match results in a ‘second-bout reserve’ strategy; otherwise, the ‘one bout, all out’ strategy is likely to be adopted. These pacing profiles are proposed to reflect the presence of a central regulator that controls the movement intensity of the player to optimize performance, as well as avoiding the harmful failure of any physiological system. The presence of ‘temporary fatigue’ reflects this process, whereby exercise intensity is consciously modulated from within the framework of a global pacing schema.

PurposeThe acute physiological, perceptual and neuromuscular responses to volume-matched running and cycling high intensity interval training (HIIT) were studied in team sport athletes.MethodsIn a randomized cross-over design, 11 male team sport players completed 3 × 6 min (with 5 min between sets) repeated efforts of 15 s exercising at 120% speed (sV˙O2max) or power (pV˙O2max) at V˙O2max followed by 15 s passive recovery on a treadmill or cycle ergometer, respectively.ResultsAbsolute mean V˙O2 (ES [95% CI] = 1.46 [0.47–2.34], p < 0.001) and heart rate (ES [95% CI] = 1.53 [0.53–2.41], p = 0.001) were higher in running than cycling HIIT. Total time at > 90% V˙O2max during the HIIT was higher for running compared to cycling (ES [95% CI] = 1.21 [0.26–2.07], p = 0.015). Overall differential RPE (dRPE) (ES [95% CI] = 0.55 [− 0.32–1.38], p = 0.094) and legs dRPE (ES [95% CI] = − 0.65 [− 1.48–0.23], p = 0.111) were similar, whereas breathing dRPE (ES [95% CI] = 1.01 [0.08–1.85], p = 0.012) was higher for running. Maximal isometric knee extension force was unchanged after running (ES [95% CI] = − 0.04 [− 0.80–0.8], p = 0.726) compared to a moderate reduction after cycling (ES [95% CI] = − 1.17 [− 2.02–0.22], p = 0.001).ConclusionCycling HIIT in team sport athletes is unlikely to meet the requirements for improving run-specific metabolic adaptation but might offer a greater lower limb neuromuscular load.

We investigated the effects of familiarization on the reliability of gross efficiency (GE) and lower-limb electromyography (EMG-rms) of adults and adolescents. We also evaluated the relationship between inter-test differences in GE and EMG-rms. Nine adult and nine adolescent cyclists performed three 10 min cycling tests at 50% of peak power output, separated by 48 h. Forty-five minutes familiarization visits were performed 24 h after each test. No differences were found across the tests for adult cyclists’ GE or EMG-rms, with Coefficient of Variation (CV%) ranging from 2.6 to 2.9% (GE) and 4.3 to 7.4%. Among adolescents, there was an increase in GE between tests 1 and 2 (p < 0.001) but not 2–3 (p = 0.438), with CVs decreasing from 6.8 to 2.6%. The adolescents’ EMG-rms decreased (p < 0.05) between tests 1 and 2, with CVs from 8.4 to 12.5%. There were no relationships (p > 0.05) between the inter-test differences of GE and EMG-rms. GE can be reliably determined; however, adolescents require two exposures to cycling. Without familiarization, adolescent EMG-rms is more variable than adults and would require larger samples to establish differences. The weak relationships between inter-test EMG-rms and inter-test GE questions the link between muscle activation and GE changes.

Purpose To examine the dose–response effects of acute glutamine supplementation on markers of gastrointestinal (GI) permeability, damage and, secondary, subjective symptoms of GI discomfort in response to running in the heat. Methods Ten recreationally active males completed a total of four exercise trials; a placebo trial and three glutamine trials at 0.25, 0.5 and 0.9 g kg −1 of fat-free mass (FFM) consumed 2 h before exercise. Each exercise trial consisted of a 60-min treadmill run at 70% of V ˙ O 2max in an environmental chamber set at 30 °C. GI permeability was measured using ratio of lactulose to rhamnose (L:R) in serum. Plasma glutamine and intestinal fatty acid binding protein (I-FABP) concentrations were determined pre and post exercise. Subjective GI symptoms were assessed 45 min and 24 h post-exercise. Results Relative to placebo, L:R was likely lower following 0.25 g kg −1 (mean difference: − 0.023; ± 0.021) and 0.5 g kg −1 (− 0.019; ± 0.019) and very likely following 0.9 g kg − 1 (− 0.034; ± 0.024). GI symptoms were typically low and there was no effect of supplementation. Discussion Acute oral glutamine consumption attenuates GI permeability relative to placebo even at lower doses of 0.25 g kg −1 , although larger doses may be more effective. It remains unclear if this will lead to reductions in GI symptoms. Athletes competing in the heat may, therefore, benefit from acute glutamine supplementation prior to exercise in order to maintain gastrointestinal integrity.

PurposeWe investigated the effects of an acute 24-h nitrate-rich beetroot juice supplement (BR) on the energy cost, exercise efficiency and blood pressure responses to intermittent walking at different gradients.MethodsIn a double-blind, cross-over design, eight participants were provided with a total of 350 ml of nitrate-rich (~ 20.5 mmol nitrate) BR or placebo (PLA) across 24 h before completing intermittent walking at 3 km/h on treadmill at gradients of 1, 5, 10, 15 and 20%.ResultsResting mean arterial pressure (MAP) was ~ 4.1% lower after BR (93 vs. 89 mmHg; P = 0.001), as well as during exercise (102 vs. 99 mmHg; P = 0.011) and recovery (97 vs. 94 mmHg; P = 0.001). Exercising (1227 vs. 1129 ml/min P < 0.001) and end-stage (1404 vs. 1249 ml/min; P = 0.002) oxygen uptake (V˙O2) was lower in BR compared to PLA, which was accompanied by an average reduction in phase II V˙O2 amplitude (1067 vs. 940 ml/min; P = 0.025). Similarly, recovery V˙O2 (509 vs. 458 ml/min; P = 0.001) was lower in BR. Whole blood potassium concentration increased from pre-post exercise in PLA (4.1 ± 0.3 vs. 4.5 ± 0.3 mmol/L; P = 0.013) but not BR (4.1 ± 0.31 vs. 4.3 ± 0.2 mmol/L; P = 0.188).ConclusionsEnergy cost of exercise, recovery of V˙O2, MAP and blood markers were ameliorated after BR. Previously-reported mechanisms explain these findings, which are more noticeable during less-efficient walking at steep gradients (15–20%). These findings have practical implications for hill-walkers.

The aim of the present thesis was to examine the potential for acute carbohydrate-protein (CHO-P) ingestion to enhance performance and recovery from exercise designed to simulate the demands of multiple-sprint sports (MSSs). Chapter 3 of the thesis explored the inter- and intra-day reliability and concurrent validity of non-motorised treadmill ergometry (NMT) for the assessment of short-distance sprint performance [i.e. 10-30 m). There were no significant mean differences between NMT variables recorded on the same day or between days. Ratio limits of agreement indicated that the best agreement was in 20 [1.02 */-=- 1.09) and 30 m [1.02 */* 1.07) sprint times, peak [1.00 */T 1.06) and mean (0.99 */+ 1.07) running speed and step length (0.99 */-=- 1.09) and frequency (1.01 */+ 1.06). The poorest agreement was observed for time to peak running speed (1.10 */* 1.47). Significant differences were observed between NMT and over-ground sprint times across all distances, with times being lower (faster) by approximately 25-30% over-ground. The correlations between NMT and over-ground variables were generally modest (r5 = 0.44 - 0.67), and optimal for time to cover 30 m on Day 2 (rs = 0.8). Chapter 4 sought to examine the efficacy of CHO-P ingestion during 4 h of recovery from the Loughborough Intermittent Shuttle Test (LIST) when compared to CHO matched for energy (ISOEN) or CHO (ISOCHO) in a typical CHO beverage. There were significant increases over time in muscle soreness, and reductions in extensor and flexor peak torque (by approximately 9%, 9% and 8%, and 13 %, 13% and 11% at 60 deg-s-1) and jump performance (10%, 7% and 5%) with the ingestion of CHO-P, ISOEN and ISOCHO, respectively. Beverage type x time interactions were not significant for any of these variables, indicating that changes in each variable were similar for all groups. Decrements in sprint performance assessed on the NMT were typically small and not different between beverage types (<4%), although sprint times over 20 and 30 m remained elevated for 48 h post-exercise. Accordingly, Chapter 4 provided no clear evidence for a benefit of ingesting CHO-P in the hours after exercise to enhance recovery of muscle function and selected performance variables following MSS activity. Chapters 5 and 6 of the thesis aimed to examine the effect of CHO-P ingestion during simulated MSS exercise. In Chapter 5, it was observed that sprint times, HR and gut fullness increased over the course of the LIST, with no influence of consuming each of the different beverages. In contrast, there was a main effect of time (P < 0.001), and drink (P = 0.042) observed for RPE, which was lower (P < 0.001) during the LIST in the CHO-P condition (16.9 ± 1.4) than in either the ISOCHO (17.8 ± 1.1) or ISOEN (17.7 ± 1.3). However, time to exhaustion was not different (P = 0.29) between CHO-P (468.3 ± 268.5 s), ISOCHO (443.4 ± 286.3 s) and ISOEN (446.2 ± 282.08 s), although these times did equate to a non-significant mean improvement of 4% in the CHO-P trial. Chapter 6 demonstrated that during a modified version of the LIST with two self-regulated blocks of exercise intensity, participants had a higher average speed (8.1 ± 0.3 cf. 7.9 ± 0.5 knvlr1) during the final (self-regulated) 15 min block of the LIST in the CHO-P condition compared to CHO. Whilst the mechanisms for such an improvement are not certain, the attenuated rise in RPE observed in Chapter 5, and increased blood urea concentration observed in Chapter 6, with CHO-P ingestion may suggest altered central fatigue and/or increased protein oxidation enhances performance during MSSs.

This benchmark volume documents in comprehensive detail a major environmental crisis: rapidly declining amphibian populations and the disturbing developmental problems that are increasingly prevalent within many amphibian species. Horror stories on this topic have been featured in the scientific and popular press over the past fifteen years, invariably asking what amphibian declines are telling us about the state of the environment. Are declines harbingers of devastated ecosystems or simply weird reflections of a peculiar amphibian world? This compendium—presenting new data, reviews of current literature, and comprehensive species accounts—reinforces what scientists have begun to suspect, that amphibians are a lens through which the state of the environment can be viewed more clearly. And, that the view is alarming and presages serious concerns for all life, including that of our own species. The first part of this work consists of more than fifty essays covering topics from the causes of declines to conservation, surveys and monitoring, and education. The second part consists of species accounts describing the life history and natural history of every known amphibian species in the United States.