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Jay O, Périard JD, Clark B, Hunt L, Ren H, Suh H, Gonzalez RR, Sawka MN. Whole body sweat rate prediction: outdoor running and cycling exercise. J Appl Physiol (1985) 2024; 136:1478-1487. [PMID: 38695357 DOI: 10.1152/japplphysiol.00831.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 04/22/2024] [Accepted: 05/01/2024] [Indexed: 06/14/2024] Open
Abstract
Our aim was to develop and validate separate whole body sweat rate prediction equations for moderate to high-intensity outdoor cycling and running, using simple measured or estimated activity and environmental inputs. Across two collection sites in Australia, 182 outdoor running trials and 158 outdoor cycling trials were completed at a wet-bulb globe temperature ranging from ∼15°C to ∼29°C, with ∼60-min whole body sweat rates measured in each trial. Data were randomly separated into model development (running: 120; cycling: 100 trials) and validation groups (running: 62; cycling: 58 trials), enabling proprietary prediction models to be developed and then validated. Running and cycling models were also developed and tested when locally measured environmental conditions were substituted with participants' subjective ratings for black globe temperature, wind speed, and humidity. The mean absolute error for predicted sweating rate was 0.03 and 0.02 L·h-1 for running and cycling models, respectively. The 95% confidence intervals for running (+0.44 and -0.38 L·h-1) and cycling (+0.45 and -0.42 L·h-1) were within acceptable limits for an equivalent change in total body mass over 3 h of ±2%. The individual variance in observed sweating described by the predictive models was 77% and 60% for running and cycling, respectively. Substituting measured environmental variables with subjective assessments of climatic characteristics reduced the variation in observed sweating described by the running model by up to ∼25%, but only by ∼2% for the cycling model. These prediction models are publicly accessible (https://sweatratecalculator.com) and can guide individualized hydration management in advance of outdoor running and cycling.NEW & NOTEWORTHY We report the development and validation of new proprietary whole body sweat rate prediction models for outdoor running and outdoor cycling using simple activity and environmental inputs. Separate sweat rate models were also developed and tested for situations where all four environmental parameters are not available, and some must be subsequently estimated by the user via a simple rating scale. All models are freely accessible through an online calculator: https://sweatratecalculator.com. These models, via the online calculator, will enable individualized hydration management for training or recreational cycling or running in an outdoor environment.
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Affiliation(s)
- Ollie Jay
- Heat and Health Research Center, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Julien D Périard
- Research Institute of Sports and Exercise, University of Canberra, Canberra, Australian Capital Territory, Australia
| | - Brad Clark
- Research Institute of Sports and Exercise, University of Canberra, Canberra, Australian Capital Territory, Australia
| | - Lindsey Hunt
- Heat and Health Research Center, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Haiyu Ren
- The Coca-Cola Company (USA), Atlanta, Georgia, United States
| | - HyunGyu Suh
- The Coca-Cola Company (USA), Atlanta, Georgia, United States
| | - Richard R Gonzalez
- Gonzalez Advanced Biophysics Associates, Lorenzo, New Mexico, United States
| | - Michael N Sawka
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, United States
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Yu P, Fan Y, Wu H. Effects of Caffeine-Taurine Co-Ingestion on Endurance Cycling Performance in High Temperature and Humidity Environments. Sports Health 2024:19417381241231627. [PMID: 38406865 DOI: 10.1177/19417381241231627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2024] Open
Abstract
BACKGROUND Taurine (TAU) and caffeine (CAF), as common ergogenic aids, are known to affect exercise performance; however, the effects of their combined supplementation, particularly in high temperature and humidity environments, have not been studied. HYPOTHESIS The combination of TAU and CAF will have a greater effect on endurance cycle performance and improve changes in physiological indicators during exercise compared with TAU or CAF supplementation alone and placebo. STUDY DESIGN Single-blind crossover randomized controlled study. LEVEL OF EVIDENCE Level 1. METHODS Twelve university students majoring in physical education volunteered to receive 4 different supplement ingestions: (1) placebo (maltodextrin), (2) TAU, (3) CAF, (4) TAU + CAF. After a 7-day washout period, participants completed a time to exhaustion (TTE) test in the heat (35°C, 65% relative humidity). RESULTS All experimental groups improved TTE compared with the placebo group. Peak and mean power of countermovement jump were significantly higher in the CAF group compared with the placebo group before the exhaustion exercise (P = 0.02, d = 1.2 and P = 0.04, d = 1.1, respectively). Blood lactate was significantly lower after the exhaustion test in the TAU group compared with the CAF (P < 0.01, d = 0.8) and TAU + CAF (P < 0.01, d = 0.7) groups. Core temperature in the TAU group was significantly reduced in the placebo group later in the exhaustion test (P < 0.01, d = 1.9). CONCLUSION In high temperature and humidity environments, acute TAU, CAF, and combined supplementation all improved TTE and did not affect recovery from lower limb neuromuscular fatigue compared with placebo, with TAU having the best effect. Combined supplementation failed to exhibit superimposed performance. CLINICAL RELEVANCE The results provide suggestions for the effects of TAU, CAF, and their combined intake on exercise performance in high temperature and humidity environments.
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Affiliation(s)
- Peiqi Yu
- Capital University of Physical Education and Sports, Beijing, China
- Comprehensive Key Laboratory of Sports Ability Evaluation and Research of the General Administration of Sport of China, Beijing, China
- Key Laboratory of Sports Function Assessment and Technical Analysis, Beijing, China
| | - Yongzhao Fan
- Department of Physical Education, Henan Normal University, Xinxiang, Henan, China
| | - Hao Wu
- Capital University of Physical Education and Sports, Beijing, China
- Comprehensive Key Laboratory of Sports Ability Evaluation and Research of the General Administration of Sport of China, Beijing, China
- Key Laboratory of Sports Function Assessment and Technical Analysis, Beijing, China
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Smallcombe JW, Foster J, Hodder SG, Jay O, Flouris AD, Havenith G. Quantifying the impact of heat on human physical work capacity; part IV: interactions between work duration and heat stress severity. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2022; 66:2463-2476. [PMID: 36197554 PMCID: PMC9684271 DOI: 10.1007/s00484-022-02370-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 09/13/2022] [Accepted: 09/15/2022] [Indexed: 06/16/2023]
Abstract
High workplace temperatures negatively impact physical work capacity (PWC). Although PWC loss models with heat based on 1-h exposures are available, it is unclear if further adjustments are required to accommodate repeated work/rest cycles over the course of a full work shift. Therefore, we examined the impact of heat stress exposure on human PWC during a simulated work shift consisting of six 1-h work-rest cycles. Nine healthy males completed six 50-min work bouts, separated by 10-min rest intervals and an extended lunch break, on four separate occasions: once in a cool environment (15 °C/50% RH) and in three different air temperature and relative humidity combinations (moderate, 35 °C/50% RH; hot, 40 °C/50% RH; and very hot, 40 °C/70%). To mimic moderate to heavy workload, work was performed on a treadmill at a fixed heart rate of 130 beats·min-1. During each work bout, PWC was quantified as the kilojoules expended above resting levels. Over the shift, work output per cycle decreased, even in the cool climate, with the biggest decrement after the lunch break and meal consumption. Expressing PWC relative to that achieved in the cool environment for the same work duration, there was an additional 5(± 4)%, 7(± 6)%, and 16(± 7)% decrease in PWC when work was performed across a full work shift for the moderate, hot, and very hot condition respectively, compared with 1-h projections. Empirical models to predict PWC based on the level of heat stress (Wet-Bulb Globe Temperature, Universal Thermal Climate Index, Psychrometric Wet-Bulb Temperature, Humidex, and Heat Index) and the number of work cycles performed are presented.
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Affiliation(s)
- James W Smallcombe
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK
- Thermal Ergonomics Laboratory, University of Sydney, Sydney, NSW, Australia
| | - Josh Foster
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital and University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Simon G Hodder
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK
| | - Ollie Jay
- Thermal Ergonomics Laboratory, University of Sydney, Sydney, NSW, Australia
| | - Andreas D Flouris
- FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, Trikala, Greece
| | - George Havenith
- Environmental Ergonomics Research Centre, Loughborough University, Loughborough, LE11 3TU, Leicestershire, UK.
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Naulleau C, Jeker D, Pancrate T, Claveau P, Deshayes TA, Burke LM, Goulet EDB. Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis. Sports Med 2022; 52:2431-2445. [PMID: 35616851 DOI: 10.1007/s40279-022-01692-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2022] [Indexed: 11/26/2022]
Abstract
BACKGROUND Heat is associated with physiological strain and endurance performance (EP) impairments. Studies have investigated the impact of caffeine intake upon EP and core temperature (CT) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat. OBJECTIVE To use a meta-analytical approach to determine the effect of pre-exercise caffeine intake on EP and CT in the heat. DESIGN Systematic review with meta-analysis. DATA SOURCES Four databases and cross-referencing. DATA ANALYSIS Weighted mean effect summaries using robust variance random-effects models for EP and CT, as well as robust variance meta-regressions to explore confounders. STUDY SELECTION Placebo-controlled, randomized studies in adults (≥ 18 years old) with caffeine intake at least 30 min before endurance exercise ≥ 30 min, performed in ambient conditions ≥ 27 °C. RESULTS Respectively six and 12 studies examined caffeine's impact on EP and CT, representing 52 and 205 endurance-trained individuals. On average, 6 mg/kg body mass of caffeine were taken 1 h before exercises of ~ 70 min conducted at 34 °C and 47% relative humidity. Caffeine supplementation non-significantly improved EP by 2.1 ± 0.8% (95% CI - 0.7 to 4.8) and significantly increased the rate of change in CT by 0.10 ± 0.03 °C/h (95% CI 0.02 to 0.19), compared with the ingestion of a placebo. CONCLUSION Caffeine ingestion of 6 mg/kg body mass ~ 1 h before exercise in the heat may provide a worthwhile improvement in EP, is unlikely to be deleterious to EP, and trivially increases the rate of change in CT.
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Affiliation(s)
- Catherine Naulleau
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Institut National du Sport du Québec, Montréal, P.Q., Canada
| | - David Jeker
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Institut National du Sport du Québec, Montréal, P.Q., Canada
| | - Timothée Pancrate
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
| | - Pascale Claveau
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
| | - Thomas A Deshayes
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Research Center on Aging, University of Sherbrooke, Sherbrooke, P.Q., Canada
| | - Louise M Burke
- Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, VIC, Australia
| | - Eric D B Goulet
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada.
- Research Center on Aging, University of Sherbrooke, Sherbrooke, P.Q., Canada.
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