Effect of Permissive Dehydration on Induction and Decay of Heat Acclimation, and Temperate Exercise Performance

Neal, Rebecca A.; Massey, Heather; Tipton, Michael J.; Young, John S.; Corbett, Jo

doi:10.3389/fphys.2016.00564

Cited by 43 publications

(89 citation statements)

References 45 publications

(121 reference statements)

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“…Furthermore, they found that work capacity in the incremental test to exhaustion increased across HA to a similar extent from both dehydrated and euhydrated HA interventions. Equally, Neal et al found no difference in aldosterone concentration or PV expansion between groups with varying hydration status during HA training, with EUH having a slightly greater non‐significant change than DEH (+8.2 ± 8.0% EUH and +6.3 ± 4.2% DEH) which translated into no difference in performance outcomes. Our data support these outcomes in that we also found no impact of hydration status during HA on PV expansion (Figure ) or performance outcomes (Figure ).…”

Section: Discussionmentioning

confidence: 97%

“…Our investigation is one of few studies to investigate the role of hydration status (euhydrated vs dehydrated) on HA responses in two isothermally clamped HA training groups. Furthermore, it is one of the few studies that features a mild/cool conditions control training group that was matched to the same internal load (%HR max and RPE) to elicit a equivalent cardiac training stimulus as the HA groups.…”

Section: Discussionmentioning

confidence: 99%

“…To our knowledge, only two studies involving a pre‐ and post‐HA crossover or group design have investigated the impact of dehydration vs euhydration during HA . Both studies utilized a randomized crossover design, with aerobically fit males (mean

V^{\cdot} O_{2 \max}

was 60 mL/kg/min and 56.9 mL/kg/min) undergoing hyperthermia controlled HA sessions that were either dehydrated (1.8% loss; 2.7% loss, respectively) vs euhydrated. Garrett et al , found a more pronounced acute response of aldosterone to heat stress with dehydration.…”

Section: Discussionmentioning

confidence: 99%

“…Overall, this relative lack of change translated into no difference in a heat stress test or an incremental test to exhaustion . Additionally, Neal et al (n = 8;) in a HA crossover design showed no difference in the impact of euhydration vs dehydration (~3% of BW) during HA in cardiovascular outcomes, aldosterone, or

V^{\cdot} O_{2 \max}

step test results between treatments. Taken together, these two existing studies would suggest a limited impact of mild dehydration in augmenting HA; although dehydration does not appear to attenuate the HA responses.…”

Section: Introductionmentioning

confidence: 96%

“…The physiological stressors required to optimize HA remain to be fully elucidated, but several key variables are potentially implicated: (a) total duration and intensity of heat stress; (b) subject hydration status throughout HA; and (c) baseline PV and/or fitness status . Several research groups have hypothesized that acutely restricting fluid intake during HA protocols, causing permissive dehydration, may further augment physiological strain and fluid regulatory hormonal responses resulting in even greater adaptations compared to euhydration protocols . Indeed, a couple of studies have examined the impact of permissive dehydration (~2% decrease in body weight [BW]) during short‐term HA protocols but have had equivocal results.…”

Section: Introductionmentioning

confidence: 99%

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Effects of hydration status during heat acclimation on plasma volume and performance

Pethick

Murray

McFadyen

et al. 2018

Scandinavian Med Sci Sports

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The impact of hydration status was investigated during a 5‐day heat acclimation (HA) training protocol vs mild/cool control conditions on plasma volume (PV) and performance (20 km time‐trial [TT]). Sub‐elite athletes were allocated to one of two heat training groups (90 min/day): (a) dehydrated to ~2% body weight (BW) loss in heat (35°C; DEH; n = 14); (b) euhydrated heat (35°C; EUH; n = 10), where training was isothermally clamped to 38.5°C core temperature (Tc). A euhydrated mild control group (22°C; CON; n = 9) was later added, with training clamped to the same relative heart rate (~75% HRmax) as elicited during DEH and EUH; thus all groups experienced the same internal training stress (%HRmax). Five‐day total thermal load was 30% greater (P < 0.001) in DEH and EUH vs CON. There were significant differences in the average percentage of maximal work rate (%Wmax) across all groups (DEH: 24 ± 6%; EUH: 34 ± 9%; CON: 48 ± 8%Wmax) during training required to elicit the same %HRmax (77 ± 4% HRmax). There were no significant differences pre‐to post‐HA between groups for PV (DEH: +1.7 ± 10.1%; EUH: +4.8 ± 10.2%; CON: +5.2 ± 4.0%), but there was a significant pooled group PV increase, as well as a 97% likely pooled improvement in TT performance (DEH: −1.8 ± 2.8%; EUH: −1.9 ± 2.1%, CON; −1.8 ± 2.8%; P = 0.136). Due to a lack of between‐group differences for PV and TT, but pooled group increases in PV and 97% likely group increase in TT performance, over 5 days of intense training at the same average relative cardiac load suggests that overall training stress may also impact significant adaptations beyond heat and hydration stress.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

V^{\cdot} O_{2 \max}

Section: Discussionmentioning

confidence: 99%

V^{\cdot} O_{2 \max}

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Effects of hydration status during heat acclimation on plasma volume and performance

Pethick

Murray

McFadyen

et al. 2018

Scandinavian Med Sci Sports

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Real‐Time Multi‐Ion Detection in the Sweat Concentration Range Enabled by Flexible, Printed, and Microfluidics‐Integrated Organic Transistor Arrays

Demuru

Kunnel

Briand

2020

Adv Materials Technologies

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working conditions. [12-15] More precisely, in human sweat, the concentration of Na + changes between 10 × 10 −3-100 × 10 −3 m, it is sweat rate-dependent and associated with dehydration. [3,14,16] K + concentration level ranges between 1 × 10 −3-18.5 × 10 −3 m with a sweat rate-independent partitioning. [3,16] Also, pH can strongly vary between 3-8 units, [3] with changes associated with dehydration and muscle fatigue. [14,15] For the next generation of wearable ion sensors, key requirements include mechanical flexibility, simple array patterning for multi-parametric analysis, and microfluidics integration for continuous sampling. [17-23] Conventionally, selective ion measurements are performed using potentiometric two-electrode systems, in which the potential drop between an Ion Selective Membrane (ISM) and a reference electrode is measured. [21,24,25] However, standard potentiometric sensors are difficult to integrate into an array configuration in a microfluidic platform, due to their high output impedance, [18] and the difficult miniaturization of a stable reference electrode. [26-28] Organic electrochemical transistors (OECTs) are an interesting alternative to conventional potentiometric sensors, overcoming some of these limitations. [29] The OECTs are three-terminal devices (drain, source, and gate), with the source and the drain electrodes connected by a conducting polymeric channel. The organic channel is based on conjugated polymer-polyelectrolyte blends, such as the mainly used poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS). [22,30-32] This active material enables mixed ionic and electronic charges interaction, with ionic conduction provided by the PSS polyelectrolyte chains and electronic conduction by nanometric-sized PEDOT crystallites. [33-35] In the presence of an electrolyte and once a positive gate voltage is applied, the dissolved cations are injected into the PEDOT:PSS channel. The cations compensate electrostatically the sulfonate anions of the PSS phase, subsequently lowering the drain current (hole de-doping) in the bulk of the layer. [2,29] This technology, without the need for a reference electrode, allows a facile miniaturization. [28,36] Moreover, the mechanical flexibility of the PEDOT:PSS channel, [22,37] the compatibility with digital manufacturing such as inkjet printing, [38-41] and the very low output impedance, [18] make OECTs promising candidates for Organic electrochemical transistors (OECTs) show remarkable promise as biosensors, thanks to their high signal amplification, simple architecture, and the intrinsic flexibility of the organic material. Despite these properties, their use for real-time sensing in complex biological fluids, such as human sweat, is strongly limited due to the lack of cross-sensitivity and selectivity studies and the use of rigid and bulky device configurations. Here, the development of a novel flexible microfluidics-integrated platform with an array of printed ion-selective OECTs enables multi-ion detection in a wearable fashion. T...

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The time course of adaptations in thermoneutral maximal oxygen consumption following heat acclimation

Waldron

Jeffries

Tallent³

et al. 2019

Eur J Appl Physiol

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Purpose This study investigated the effects of a 10-day heat acclimation (HA) programme on the time course of changes in thermoneutral maximal oxygen uptake ($$\dot{V}$$ V ˙ O2max) during and up to 10 days post-HA. Methods Twenty-two male cyclists were assigned to a HA or control (Con) training group following baseline ramp tests of thermoneutral $$\dot{V}$$ V ˙ O2max. Ten days of fixed-intensity (50% baseline $$\dot{V}$$ V ˙ O2max) indoor cycling was performed in either ~ 38.0 °C (HA) or ~ 20 °C (Con). $$\dot{V}$$ V ˙ O2max was re-tested on HA days 5, 10 and post-HA days 1, 2, 3, 4, 5 and 10. Results $$\dot{V}$$ V ˙ O2max initially declined across time in both groups during training (P < 0.05), before increasing in the post-HA period in both groups (P < 0.05). However, $$\dot{V}$$ V ˙ O2max was higher than control by post-HA day 4 in the HA group (P = 0.046). Conclusions The non-linear time course of $$\dot{V}$$ V ˙ O2max adaptation suggests that post-testing should be performed 96-h post-training to identify the maximal change for most individuals. In preparation for training or testing, athletes can augment their aerobic power in thermoneutral environments by performing 10 days HA, but the full effects will manifest at varying stages of the post-HA period.

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Effect of Permissive Dehydration on Induction and Decay of Heat Acclimation, and Temperate Exercise Performance

Cited by 43 publications

References 45 publications

Effects of hydration status during heat acclimation on plasma volume and performance

Effects of hydration status during heat acclimation on plasma volume and performance

Real‐Time Multi‐Ion Detection in the Sweat Concentration Range Enabled by Flexible, Printed, and Microfluidics‐Integrated Organic Transistor Arrays

The time course of adaptations in thermoneutral maximal oxygen consumption following heat acclimation

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