The Influence of Hot Humid and Hot Dry Environments on Intermittent-Sprint Exercise Performance

2014 ◽  
Vol 9 (3) ◽  
pp. 387-396 ◽  
Author(s):  
Mark Hayes ◽  
Paul C. Castle ◽  
Emma Z. Ross ◽  
Neil S. Maxwell
Keyword(s):  
Heat Stress ◽  
Exercise Performance ◽  
Peak Power ◽  
Team Sport ◽  
Peak Power Output ◽  
Evaporative Heat Loss ◽  
Physiological Strain ◽  
Type Method ◽  
Sprint Exercise ◽  
Full Protocol

Purpose:To examine the effect of a hot humid (HH) compared with a hot dry (HD) environment, matched for heat stress, on intermittent-sprint performance. In comparison with HD, HH environments compromise evaporative heat loss and decrease exercise tolerance. It was hypothesized that HH would produce greater physiological strain and reduce intermittent-sprint exercise performance compared with HD.Method:Eleven male team-sport players completed the cycling intermittent-sprint protocol (CISP) in 3 conditions, temperate (TEMP; 21.2°C ± 1.3°C, 48.6% ± 8.4% relative humidity [rh]), HH (33.7°C ± 0.5°C, 78.2% ± 2.3% rh), and HD (40.2°C ± 0.2°C, 33.1% ± 4.9% rh), with both heat conditions matched for heat stress.Results:All participants completed the CISP in TEMP, but 3 failed to completed the full protocol of 20 sprints in HH and HD. Peak power output declined in all conditions (P < .05) but was not different between any condition (sprints 1–14 [N = 11]: HH 1073 ± 150 W, HD 1104 ± 127 W, TEMP, 1074 ± 134; sprints 15–20 [N = 8]: HH 954 ± 114 W, HD 997 ± 115 W, TEMP 993 ± 94; P > .05). Physiological strain was not significantly different in HH compared with HD, but HH was higher than TEMP (P < .05).Conclusion:Intermittent-sprint exercise performance of 40 min duration is impaired, but it is not different in HH and HD environments matched for heat stress despite evidence of a trend toward greater physiological strain in an HH environment.

The Effects of Compression Garments on Intermittent Exercise Performance and Recovery on Consecutive Days

2008 ◽  
Vol 3 (4) ◽  
pp. 454-468 ◽  
Author(s):  
Rob Duffield ◽  
Johann Edge ◽  
Robert Merrells ◽  
Emma Hawke ◽  
Matt Barnes ◽  
...  
Keyword(s):  
Heart Rate ◽  
Exercise Performance ◽  
High Intensity ◽  
Peak Power ◽  
Muscle Soreness ◽  
Sport Activity ◽  
Team Sport ◽  
Tympanic Temperature ◽  
Exercise Protocol ◽  
Compression Garments

Purpose:The aim of this study was to determine whether compression garments improve intermittent-sprint performance and aid performance or self-reported recovery from high-intensity efforts on consecutive days.Methods:Following familiarization, 14 male rugby players performed two randomized testing conditions (with or without garments) involving consecutive days of a simulated team sport exercise protocol, separated by 24 h of recovery within each condition and 2 weeks between conditions. Each day involved an 80-min high-intensity exercise circuit, with exercise performance determined by repeated 20-m sprints and peak power on a cart dynamometer (single-man scrum machine). Measures of nude mass, heart rate, skin and tympanic temperature, and blood lactate (La−) were recorded throughout each day; also, creatine kinase (CK) and muscle soreness were recorded each day and 48 h following exercise.Results:No differences (P = .20 to 0.40) were present between conditions on either day of the exercise protocol for repeated 20-m sprint efforts or peak power on a cart dynamometer. Heart rate, tympanic temperature, and body mass did not significantly differ between conditions; however, skin temperature was higher under the compression garments. Although no differences (P = .50) in La− or CK were present, participants felt reduced levels of perceived muscle soreness in the ensuing 48 h postexercise when wearing the garments (2.5 ± 1.7 vs 3.5 ± 2.1 for garment and control; P = .01).Conclusions:The use of compression garments did not improve or hamper simulated team-sport activity on consecutive days. Despite benefits of reduced self-reported muscle soreness when wearing garments during and following exercise each day, no improvements in performance or recovery were apparent.

scholarly journals Influence of Hypohydration on Intermittent Sprint Performance in the Heat

2009 ◽  
Vol 4 (1) ◽  
pp. 54-67 ◽  
Author(s):  
Neil S. Maxwell ◽  
Richard W.A. Mackenzie ◽  
David Bishop
Keyword(s):  
Relative Humidity ◽  
Peak Power ◽  
Cycle Ergometer ◽  
Sprint Performance ◽  
Peak Power Output ◽  
Total Work ◽  
Physiological Strain ◽  
Metabolic Markers ◽  
Repeated Sprint ◽  
Physiological Strain Index

Purpose:To examine the effect of hypohydration on physiological strain and intermittent sprint exercise performance in the heat (35.5 ± 0.6°C, 48.7 ± 3.4% relative humidity).Methods:Eight unacclimatized males (age 23.4 ± 6.2 y, height 1.78 ± 0.04 m, mass 76.8 ± 7.7 kg) undertook three trials, each over two days. On day 1, subjects performed 90 min of exercise/heat-induced dehydration on a cycle ergometer, before following one of three rehydration strategies. On day 2, subjects completed a 36-min cycling intermittent sprint test (IST) with a -0.62 ± 0.74% (euhydrated, EUH), -1.81 (0.99)% (hypohydrated1, HYPO1), or -3.88 ± 0.89% (hypohydrated2, HYPO2) body mass defcit.Results:No difference was observed in average total work (EUH, 3790 ± 556 kJ; HYPO1, 3785 ± 628 kJ; HYPO2, 3647 ± 339 kJ, P = 0.418), or average peak power (EUH, 1315 ± 129 W; HYPO1, 1304 ± 175 W; HYPO2, 1282 ± 128 W, P = 0.356) between conditions on day 2. Total work and peak power output in the sprint immediately following an intense repeated sprint bout during the IST were lower in the HYPO2 condition. Physiological strain index was greater in the HYPO2 vs. the EUH condition, but without changes in metabolic markers.Conclusion:A greater physiological strain was observed with the greatest degree of hypohydration; however, sprint performance only diminished in the most hypohydrated state near the end of the IST, following an intense bout of repeating sprinting.

Effects of External Counterpulsation on Postexercise Recovery in Elite Rugby League Players

2019 ◽  
Vol 14 (10) ◽  
pp. 1350-1356 ◽  
Author(s):  
Llion A. Roberts ◽  
Johnpaul Caia ◽  
Lachlan P. James ◽  
Tannath J. Scott ◽  
Vincent G. Kelly
Keyword(s):  
Receptor Antagonist ◽  
Exercise Performance ◽  
Peak Power ◽  
Interleukin 1 ◽  
Rugby League ◽  
Peak Power Output ◽  
Placebo Control ◽  
Coronary Perfusion ◽  
External Counterpulsation ◽  
Interleukin 1 Receptor Antagonist

Purpose: External counterpulsation (ECP) has previously been used to treat cardiac patients via compression of the lower extremities during diastole to increase venous return and coronary perfusion. However, the effects of ECP on exercise performance and markers of recovery in elite athletes are largely unknown. Methods: On 2 separate occasions, 48 h apart, 7 elite National Rugby League players performed an identical 60-min field-based conditioning session followed by a 30-min period of either regular ECP treatment or placebo. Power measures during repeated cycle bouts and countermovement jump height and contraction time derivatives were measured at rest and 5 h postexercise. Saliva samples and venous blood samples were taken at rest, postexercise, and 5 h postexercise to assess stress, inflammation, and muscle damage. Results: After ECP treatment, cycling peak power output (P = .028; 11%) and accumulated peak power (P = .027; 14%) increased compared with the placebo condition. Postexercise plasma interleukin 1 receptor antagonist only increased after ECP (P = .024; 84%), and concentrations of plasma interleukin 1 receptor antagonist tended to be higher (P = .093; 76%) 5 h postexercise. Furthermore, testosterone-to-cortisol ratio was increased above baseline and placebo 5 h postexercise (P = .017–.029; 24–77%). The ratio of postexercise salivary α-amylase to immunoglobulin A decreased after treatment (P = .013; 50%) compared with the placebo control. Conclusions: Exercise performance and hormonal indicators of stress were improved and inflammation markers were reduced following acute ECP.

Effect of creatine loading on long-term sprint exercise performance and metabolism

2001 ◽  
pp. 814-821 ◽  
Author(s):  
DAVID PREEN ◽  
BRIAN DAWSON ◽  
CARMEL GOODMAN ◽  
STEVEN LAWRENCE ◽  
JOHN BEILBY ◽  
...  
Keyword(s):  
Exercise Performance ◽  
Sprint Exercise

Abstract P134: Preliminary Data: Dietary Nitrate Supplementation Does Not Extend Dry Static Apnea Or Wingate Performance

Circulation ◽  
2021 ◽  
Vol 143 (Suppl_1) ◽  
Author(s):  
Colin Carriker ◽  
Phillip Armentrout ◽  
Sarah Levine ◽  
James Smoliga
Keyword(s):  
Power Output ◽  
Preliminary Data ◽  
Repeated Measures ◽  
Peak Power ◽  
Hold Time ◽  
Wingate Test ◽  
Peak Power Output ◽  
Breath Hold ◽  
Dietary Nitrate ◽  
Nitrate Supplementation

Introduction: Previous studies have examined dietary nitrate supplementation and its effects on dry static apnea, and peak power. Dietary nitrate supplementation has been found to increase maximal apnea and peak power output. The purpose of this study was to determine the effects of beetroot juice on dry static apnea and Wingate performance. Hypothesis: Dietary nitrate will improve maximal breath hold time and peak power output. Dietary nitrate will improve tolerance to CO2, thereby improving maximal breath hold time and anaerobic capacity. Methods: In a randomized, double-blind, counterbalanced study, five healthy males (20.4±0.89 years) visited the lab on 3 separate occasions each separated by one week. Visit 1 served as a Wingate and breath hold familiarization visit. Prior to visits 2 and 3 participants were instructed to drink a beverage either a placebo (negligible nitrate content, PL) or dietary nitrate rich beverage (12.4 mmol nitrate, NIT) during the 4 days leading up to their next visit. Visits 2 and 3 consisted of two submaximal breath holds (80% of maximal determined during visit 1), with 2 minutes of rest between and three minutes of rest preceding the final breath hold for maximal duration. Finally, participants completed a standardized 10-minute warmup on the cycle ergometer before completing a 30-second maximal effort Wingate test. Results: A linear mixed effects model was used to determine whether treatment (NIT vs. PL) was associated with differences in VCO2 or PetCO2. Time (0, 10, 20, 30 min post-breath hold) and Treatment both served as repeated measures. Models were developed using multiple repeated measures covariance matrix structures, and the model with the lowest AIC was chosen as the final model. The interaction between time and treatment was included in the original models, and was removed if it was not statistically significant. Time was a statistically significant factor for VCO2 and PetCO2 (p < 0.001). Treatment, and the Time x Treatment interaction was not significant for either variable. No differences between NIT and PL were observed during the Wingate test for either time to peak power (5.02±2.45 and 6.2±2.43 sec, respectively) or maximal power (9.73±1.01 and 9.72±1.03 watts/kg, respectively) and fatigue index (49.42±14.98 and 47.30±6.99 watts/sec, respectively). Conclusion: Preliminary data indicates that in a general population four days of dietary nitrate supplementation may not improve breath hold time, tolerance to carbon dioxide in the lungs, or Wingate performance.

A review of intervention methods used to reduce flying-fox mortalities in heat stress events

2021 ◽  
Vol 43 (2) ◽  
pp. 137
Author(s):  
Matthew Mo ◽  
Mike Roache
Keyword(s):  
Climate Change ◽  
Systematic Review ◽  
Heat Stress ◽  
Evidence Based ◽  
Evaporative Heat Loss ◽  
Temperature And Humidity ◽  
Intervention Trials ◽  
Individual Scale ◽  
The Relationship ◽  
Flying Fox

Heat stress events in Australian flying-fox camps have resulted in significant numbers of flying-fox deaths. The frequency and intensity of such events have increased in recent decades, attributed to anthropogenic climate change. Evidence-based interventions are required to address this growing threat. Responders currently use different combinations of a range of intervention methods. We undertook a systematic review of heat stress interventions, which we classified as either ‘camp-scale’ or ‘individual-scale’. Camp-scale interventions included manual and automated misting of roost vegetation, whereas individual-scale interventions included spraying individual animals or removing them for intensive cooling and rehydration procedures. Our study showed that to date, evaluation of the efficacy of heat stress interventions has been largely anecdotal rather than empirical. This highlights the need for dedicated rigorous studies to evaluate the effectiveness of all the intervention methods described here. It will be especially important to understand the relationship between camp temperature and humidity levels and their influence on flying-foxes’ ability to regulate their body temperature, because high relative humidity reduces the ability of mammals to cool themselves using evaporative heat loss. The development of biophysiological measures such as temperature and humidity indices for different flying-fox species would enable meaningful interpretations of intervention trials under controlled conditions.

Force-velocity and force-power properties of single muscle fibers from elite master runners and sedentary men

1996 ◽  
Vol 271 (2) ◽  
pp. C676-C683 ◽  
Author(s):  
J. J. Widrick ◽  
S. W. Trappe ◽  
D. L. Costill ◽  
R. H. Fitts
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Power Output ◽  
Peak Power ◽  
Isometric Force ◽  
Peak Force ◽  
Peak Power Output ◽  
Type I ◽  
Shortening Velocity ◽  
Force Velocity

Gastrocnemius muscle fiber bundles were obtained by needle biopsy from five middle-aged sedentary men (SED group) and six age-matched endurance-trained master runners (RUN group). A single chemically permeabilized fiber segment was mounted between a force transducer and a position motor, subjected to a series of isotonic contractions at maximal Ca2+ activation (15 degrees C), and subsequently run on a 5% polyacrylamide gel to determine myosin heavy chain composition. The Hill equation was fit to the data obtained for each individual fiber (r2 > or = 0.98). For the SED group, fiber force-velocity parameters varied (P < 0.05) with fiber myosin heavy chain expression as follows: peak force, no differences: peak tension (force/fiber cross-sectional area), type IIx > type IIa > type I; maximal shortening velocity (Vmax, defined as y-intercept of force-velocity relationship), type IIx = type IIa > type I; a/Pzero (where a is a constant with dimensions of force and Pzero is peak isometric force), type IIx > type IIa > type I. Consequently, type IIx fibers produced twice as much peak power as type IIa fibers, whereas type IIa fibers produced about five times more peak power than type I fibers. RUN type I and IIa fibers were smaller in diameter and produced less peak force than SED type I and IIa fibers. The absolute peak power output of RUN type I and IIa fibers was 13 and 27% less, respectively, than peak power of similarly typed SED fibers. However, type I and IIa Vmax and a/Pzero were not different between the SED and RUN groups, and RUN type I and IIa power deficits disappeared after power was normalized for differences in fiber diameter. Thus the reduced absolute peak power output of the type I and IIa fibers from the master runners was a result of the smaller diameter of these fibers and a corresponding reduction in their peak isometric force production. This impairment in absolute peak power production at the single fiber level may be in part responsible for the reduced in vivo power output previously observed for endurance-trained athletes.

Arm muscle sympathetic nerve activity during preparation for and initiation of leg-cycling exercise in humans

1994 ◽  
Vol 77 (3) ◽  
pp. 1403-1410 ◽  
Author(s):  
R. Callister ◽  
A. V. Ng ◽  
D. R. Seals
Keyword(s):  
Power Output ◽  
Peak Power ◽  
General Pattern ◽  
Peak Power Output ◽  
Movement Initiation ◽  
Nerve Activity ◽  
Cycling Exercise ◽  
Target Power ◽  
Leg Cycling ◽  
Exercise In Humans

We tested the hypothesis that sympathetic vasoconstrictor nerve activity to nonactive skeletal muscle (MSNA) decreases immediately before and remains suppressed during initiation of conventional large muscle upright dynamic exercise in humans. In 11 healthy young subjects, adequate recordings of MSNA from the radial nerve in the arm were obtained during upright seated rest (control) and throughout 1 min of leg-cycling exercise at one or more submaximal workloads (range 33–266 W; approximately 10–80% of peak power output). MSNA was analyzed during four consecutive time intervals; control, preparation for cycling (end of control to onset of pedal movement), initiation of cycling (onset of pedal movement to attainment of target power output), and the initial 60 s of cycling at target power output. MSNA decreased (P < 0.05) abruptly and markedly in all subjects [to 19 +/- 4% (SE) of control levels] during the preparation period before the 33-W load and remained suppressed throughout the period of initiation of cycling in 8 of 11 subjects; MSNA increased during the initiation period in three subjects in whom diastolic arterial pressure fell below control levels. This general pattern was observed at all loads. MSNA remained at or below control levels throughout the 1 min of cycling exercise at 33–166 W. MSNA increased above control levels during the latter portion of the 1 min of cycling only at loads > or = 60% of peak power output.(ABSTRACT TRUNCATED AT 250 WORDS)

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