Mild hypohydration in healthy older adults increases pain-related brain activity without affecting pain perception: a single-blind study.

Understanding how hydration status influences pain perception is particularly important in older adults, as both dehydration and pain are prevalent in this population. Ten individuals (70 ± 4 yr) completed two randomized and counterbalanced trials. They were exposed to passive heat until they lost 1% body mass through sweat and urine (∼100 min), with the loss either unreplaced (sham infusion, HYPO) or fully replaced via 0.

Assessment of the Omius™ cooling headband effectiveness during a 70-min submaximal running effort followed by a 5-km time-trial in hot/humid conditions.

Exercise performed under hot/humid conditions can hinder endurance performance. The Omius™ headband (OH) is purported to reduce the perception of heat and improve performance. We examined the impact of OH on selected thermal and cardiovascular functions, subjective perceptions and running performance.

Repeatability of Ad Libitum Water Intake during Repeated 1 h Walking/Jogging Exercise Sessions Conducted under Hot Ambient Conditions.

A drinking strategy aiming to replace a given percentage of the sweat losses incurred during exercise should result in reproducible fluid intake volume and, hence, fluid balance from one exercise session to the other performed under similar scenarios. Whether this may also be the case with ad libitum drinking during exercise is unclear. We characterized the repeatability of ad libitum water intake during repeated 1 h exercise sessions and examined its effect over time on fluid balance and selected physiological functions and perceptual sensations.

Effect of electric fan use in isolation or combined with ice slurry/cold water ingestion and lower-leg immersion in young men during intermittent physical activity in hot-humid conditions.

Using a randomized crossover protocol, 10 young men completed four 180 min exposures (38 °C, 60% relative humidity), alternating between 30 min of walking and 30 min of sitting where fluid or ice slurry were served. Participants underwent four trials: (i) 5 mL·kg body mass of 20 °C water (CON); (ii) 5 mL·kg body mass of 20 °C water + fan at 4 m·s (FAN); (iii) fan + 3 mL·kg body mass of ice slurry + 2 mL·kg body mass of 4 °C water (FAN + ISCW); and (iv) FAN + ISCW + lower-leg immersion in 20 °C water (FAN + ISCW + LLI). Sweat and body mass losses were higher with FAN than CON, FAN + ISCW, and FAN + ISCW + LLI.

CORE™ wearable sensor: Comparison against gastrointestinal temperature during cold water ingestion and a 5 km running time-trial.

Five km running time-trials (TT) are associated with rapid and significant increases in core body temperature (T). For such races, real-time feedback from pre-exercise and exercise T may be helpful in the design of an optimal pacing strategy aimed at limiting the possibility of developing heat-related illnesses. This study compared measurements of T obtained with a wearable device, the CORE™, to those of a gastrointestinal pill (GI pill), during cold water ingestion and a 5 km running TT.

Effect of Glycerol-Induced Hyperhydration on a 5-kilometer Running Time-Trial Performance in the Heat in Recreationally Active Individuals.

Maximal oxygen consumption (V˙O) is a major determinant of 5-km running time-trial (TT) performance. Glycerol-induced hyperhydration (GIH) could improve V˙O in recreationally active persons through an optimal increase in plasma volume. Moreover, ingestion of a large bolus of cold fluid before exercise could decrease thermal stress during exercise, potentially contributing to improved performance.

Change in heart rate variability during two firefighting work cycles.

This study aimed to determine whether the change in heart rate variability from pre to post firefighting is modulated by different work cycles. Thirteen male firefighters underwent two firefighting simulations that comprised two identical 25-min work bouts intercalated by a passive recovery period of either 20 min (T20) or 5 min (T5). The square root of the mean squared differences of successive R-R intervals (RMSSD) and aural temperature were measured at rest before (PRE) and after (POST) firefighting simulations.

Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis.

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 (C) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat.

Impact of dehydration on perceived exertion during endurance exercise: A systematic review with meta-analysis.

Background: Understanding the impact of stressors on the rating of perceived exertion (RPE) is relevant from a performance and exercise adherence/participation standpoint. Athletes and recreationally active individuals dehydrate during exercise. No attempt has been made to systematically determine the impact of exercise-induced dehydration (EID) on RPE.

Cognitive Performance Before and Following Habituation to Exercise-Induced Hypohydration of 2 and 4% Body Mass in Physically Active Individuals.

We investigated the effect of repeated exposures to hypohydration upon cognitive performance. In a randomized crossover design, ten physically active adults completed two 4-week training blocks, one where they maintained euhydration (EUH) and the other where they were water-restricted (DEH) during walking/running at 55% V.O2max, 40 °C.

Programmed vs. Thirst-Driven Drinking during Prolonged Cycling in a Warm Environment.

We compared the effect of programmed (PFI) and thirst-driven (TDFI) fluid intake on prolonged cycling performance and exercise associated muscle cramps (EAMC). Eight male endurance athletes (26 ± 6 years) completed two trials consisting of 5 h of cycling at 61% V˙O2peak followed by a 20 km time-trial (TT) in a randomized crossover sequence at 30 °C, 35% relative humidity. EAMC was assessed after the TT with maximal voluntary isometric contractions of the shortened right plantar flexors.

Impact of Repeated Acute Exposures to Low and Moderate Exercise-Induced Hypohydration on Physiological and Subjective Responses and Endurance Performance.

This study aimed to examine whether repeated exposures to low (2%) and moderate (4%) exercise-induced hypohydration may reverse the potentially deleterious effect of hypohydration on endurance performance. Using a randomized crossover protocol, ten volunteers (23 years, V˙O: 54 mL∙kg∙min) completed two 4-week training blocks interspersed by a 5-week washout period. During one block, participants replaced all fluid losses (EUH) while in the other they were fluid restricted (DEH).

Validity and Reliability of the Computrainer Lab™ During Simulated 40 and 100 km Time-Trials.

The validity and reliability of the Computrainer Lab (CT) was assessed, for the first time, using a high-precision motor-driven calibration rig during simulated variable intensity 40 and 100 km time-trials (TTs). The load patterns imposed by the CT were designed from previously published studies in trained cyclists and included multiple 1 or 4 km bursts in power output. For the 40 and 100 km TTs, cluster-based analyses revealed a mean measurement error from the true workload of respectively 0.

Provision of instructions to drink ad libitum or according to thirst sensation: impact during 120 km of cycling in the heat in men.

The terms drinking to thirst and ad libitum drinking are used interchangeably, but should they? We investigated the differences in how athletes consumed fluids during exercise when instructed to drink according to thirst or ad libitum. Using a randomized, crossover, and counterbalanced design, 10 males (27 ± 4 y) cycled 120 km (48 ± 4% of peak power, 33 °C, 40% relative humidity) on 2 occasions, while drinking water according to thirst or ad libitum. Participants covered the cycling trials in 222 ± 11 min ( = 0.

Validity and Reliability of the CorTemp Telemetric Pill during 50 h of Reuse in a Circulating Water Bath.

It has been shown that CorTemp telemetric pills (CTTPs) provide valid measures of rectal temperature when used as suppositories. While encapsulated into a condom linked to a thread, CTTPs can be inserted in and extracted from the rectum and be reused. The validity and reliability of the CTTP throughout repeated use remains to be demonstrated.

Impact of Mild Hypohydration on 100 m Front Crawl Performance and Starting Block Peak Force Production in Competitive University-Level Swimmers.

Unstructured, ad libitum drinking may predispose some athletes to start exercise already slightly hypohydrated (decreased body water). The impact of pre-exercise mild hypohydration on subsequent swimming performance is still unknown. Hence, the goal of this study was to examine its effect on peak force production on the starting block and 100 m front crawl swimming performance in competitive university-level swimmers.

Permanent tattooing has no impact on local sweat rate, sweat sodium concentration and skin temperature or prediction of whole-body sweat sodium concentration during moderate-intensity cycling in a warm environment.

Purposes: This study investigated the impact of permanently tattooed skin on local sweat rate, sweat sodium concentration and skin temperature and determined whether tattoos alter the relationship between local and whole-body sweat sodium concentration.

Methods: Thirteen tattooed men (27 ± 6 years) completed a 1 h (66 ± 4% of [Formula: see text]) cycling trial at 32 °C, 35% relative humidity. Sweat rate and sweat sodium concentration were measured using the whole-body washdown and local absorbent patch techniques.

Comment on: "The Utility of Thirst as a Measure of Hydration Status Following Exercise-Induced Dehydration".

In their study, Adams et al. [1] attempted to determine whether thirst perception could serve as a reliable marker of hydration status during 3 h of exercise where participants either dehydrated by 3% of their body mass or maintained euhydration through water intake, and following exercise where they either could not drink or were allowed to consume water ad libitum during the first 10 min of a 60 min long recovery period [..

Impact of Pre-exercise Hypohydration on Aerobic Exercise Performance, Peak Oxygen Consumption and Oxygen Consumption at Lactate Threshold: A Systematic Review with Meta-analysis.

Background: Progressive exercise-induced dehydration may impair aerobic exercise performance (AEP). However, no systematic approach has yet been used to determine how pre-exercise hypohydration, which imposes physiological challenges differing from those of a well-hydrated pre-exercise state, affects AEP and related components such as peak oxygen consumption [Formula: see text] and [Formula: see text] at lactate threshold [Formula: see text].

Objective: To determine, using a systematic approach with meta-analysis, the magnitude of the effect of pre-exercise hypohydration on AEP, [Formula: see text] and [Formula: see text].

Effect of Thirst-Driven Fluid Intake on 1 H Cycling Time-Trial Performance in Trained Endurance Athletes.

A meta-analysis demonstrated that programmed fluid intake (PFI) aimed at fully replacing sweat losses during a 1 h high-intensity cycling exercise impairs performance compared with no fluid intake (NFI). It was reported that thirst-driven fluid intake (TDFI) may optimize cycling performance, compared with when fluid is consumed more than thirst dictates. However, how TDFI, compared with PFI and NFI, impacts performance during a 1 h cycling time-trial performance remains unknown.

The ability of exercise to meaningfully improve glucose tolerance in people living with prediabetes: A meta-analysis.

Background: Individuals with prediabetes are likely to progress to Type 2 diabetes. Although exercise training is an established method to improve glycemic control, the degree to which this translates into meaningful improvements, particularly in individuals with prediabetes, is unclear. The purpose of this meta-analysis was to investigate the ability of exercise training to improve 2-hour glucose tolerance beyond the smallest worthwhile difference in individuals with prediabetes.

The Impact of an Ice Slurry-Induced Gastrointestinal Heat Sink on Gastrointestinal and Rectal Temperatures Following Exercise.

Gastrointestinal temperature (gint) measurement with a telemetric pill (TP) is increasingly used in exercise science. Contact of cool water with a TP invalidates gint assessment. However, what effect a heat sink created in the proximity of a TP may have on the assessment of gint remains unknown.

Wireless measurement of rectal temperature during exercise: Comparing an ingestible thermometric telemetric pill used as a suppository against a conventional rectal probe.

Wireless measurement of rectal temperature during exercise may circumvent some limitations associated with the use of a conventional wired probe. We determined, for the first time, whether temperatures provided in vivo by wireless ingestible thermometric telemetric pills and a rectal probe compare favorably under conditions producing slow and rapid increases and decreases in rectal temperature. While wearing a rectal probe linked to a wireless ingestible thermometric telemetric pill, 13 participants completed the following phases: 1) 30 min sitting; 2) 45 min passive heat exposure (40-42 °C); 3) 45 min sitting while ingesting 7.