Skin temperature modifies impact of hypohydration on aerobic performance

US Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Kansas St., Natick, MA 01760, USA.
Journal of Applied Physiology (Impact Factor: 3.06). 04/2010; 109(1):79-86. DOI: 10.1152/japplphysiol.00135.2010
Source: PubMed


This study determined the effects of hypohydration on aerobic performance in compensable [evaporative cooling requirement (Ereq) < maximal evaporative cooling (Emax)] conditions of 10°C [7°C wet bulb globe temperature (WBGT)], 20°C (16°C WBGT), 30°C (22°C WBGT), and 40°C (27°C WBGT) ambient temperature (Ta). Our hypothesis was that 4% hypohydration would impair aerobic performance to a greater extent with increasing heat stress. Thirty-two men [22 ± 4 yr old, 45 ± 8 ml·kg-1peak O2 uptake (Vo2Peak)] were divided into four matched cohorts (n = 8) and tested at one of four T a in euhydrated (EU) and hypohydrated (HYPO, -4% body mass) conditions. Subjects completed 30 min of preload exercise (cycle ergometer, 50% Vo2peak) followed by a 15 min self-paced time trial. Timetrial performance (total work, change from EU) was -3% (P = 0.1), -5% (P = 0.06), -12% (P < 0.05), and -23% (P < 0.05) in 10°C, 20°C, 30°C, and 40°C Ta, respectively. During preload exercise, skin temperature (Tsk) increased by ∼4°C per 10°C Ta, while core (rectal) temperature (Tre,) values were similar within EU and HYPO conditions across all Ta. A significant relationship (P < 0.05, r = 0.61) was found between Tsk and the percent decrement in time-trial performance. During preload exercise, hypohydration generally blunted the increases in cardiac output and blood pressure while reducing blood volume over time in 30°C and 40°C Ta. Our conclusions are as follows: 1) hypohydration degrades aerobic performance to a greater extent with increasing heat stress; 2) when TSk is >29°C, 4% hypohydration degrades aerobic performance by ∼1.6% for each additional 1°C Tsk; and 3) cardiovascular strain, from high skin blood flow requirements combined with blood volume reductions induced by hypohydration is an important contributor to impaired performance.Copyright © 2005 by the American Physiological Society Skin temperature modifies the impact of hypohydration on aerobic performance.

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    • "With warm skin a 4% body mass loss impaired performance by 18% as compared to the warm skin with euhydration with no significant differences in core temperature across trials. Kenefick et al. (2010) further tested the interaction between environmental conditions and hypohydration by having participants cycle for 30 min (50% ) followed by a 15 min time trial in 10, 20, 30 and 40°C environments (inducing stepwise increases in T sk from 26 to 36°C) "
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    • "Skin temperature ( ) T sk is an important physiological measure that can reflect the presence of illness and injury as well as provide insight into the localised interactions between the body and the environment. T sk has a wide range of applications that consist of, but are not limited to, the assessment of: complex regional pain syndrome (Wasner et al 2002, Koban et al 2003), diabetic ulceration (Armstrong et al 1997), overuse injuries (Meknas et al 2008, Hildebrandt et al 2010), physiological strain (Cuddy et al 2013), hypoxia (Cipriano and Goldman 1975), exercise performance (Price 2006, Kenefick et al 2010, Schlader et al 2011), pacing strategies (Tucker 2009), cold exposure (Selfe et al 2006, Bleakley et al 2012, Costello et al 2012a), fever screening (Chiu et al 2005, Bitar et al 2009, Nguyen et al 2010), thermal comfort and sensation (Wang et al 2007), circadian rhythm (Yosipovitch et al 1998, van Marken Lichtenbelt et al 2006, Hasselberg et al 2013), and when coupled with core body temperature, can determine mean body temperature (Colin et al 1971). Consequently, the assessment of T sk is extremely important in clinical, occupational, sports medicine, exercise science and public health settings. "
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    ABSTRACT: Skin temperature is an important physiological measure that can reflect the presence of illness and injury as well as provide insight into the localised interactions between the body and the environment. The aim of this systematic review was to analyse the agreement between conductive and infrared means of assessing skin temperature which are commonly employed in in clinical, occupational, sports medicine, public health and research settings.Full-text eligibility was determined independently by two reviewers. Studies meeting the following criteria were included in the review: (1) the literature was written in English, (2) participants were human (in vivo), (3) skin surface temperature was assessed at the same site, (4) with at least two commercially available devices employed-one conductive and one infrared-and (5) had skin temperature data reported in the study.A computerised search of four electronic databases, using a combination of 21 keywords, and citation tracking was performed in January 2015. A total of 8,602 were returned.Methodology quality was assessed by two authors independently, using the Cochrane risk of bias tool.A total of 16 articles (n = 245) met the inclusion criteria.Devices are classified to be in agreement if they met the clinically meaningful recommendations of mean differences within ±0.5 °C and limits of agreement of ±1.0 °C.Twelve of the included studies found mean differences greater than ±0.5 °C between conductive and infrared devices. In the presence of external stimulus (e.g. exercise and/or heat) five studies found exacerbated measurement differences between conductive and infrared devices.This is the first review that has attempted to investigate presence of any systemic bias between infrared and conductive measures by collectively evaluating the current evidence base. There was also a consistently high risk of bias across the studies, in terms of sample size, random sequence generation, allocation concealment, blinding and incomplete outcome data.This systematic review questions the suitability of using infrared cameras in stable, resting, laboratory conditions. Furthermore, both infrared cameras and thermometers in the presence of sweat and environmental heat demonstrate poor agreement when compared to conductive devices. These findings have implications for clinical, occupational, public health, sports science and research fields.
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    • "Dr. Sam Cheuvront (see Figure 1) is developing (with industrial partners) technologies for a valid non-invasive hydration status measure. We believe that exercise performance in the heat is impaired because of high skin blood flow requirements [15] and hypovolemia [16] via the cardiovascular system rather than a “critical core temperature” as is a popular belief in the sports medicine literature [17]. Drs. Bob Kenefick and Nisha Charkoudian (see Figure 1) are continuing research to determine if blood pressure control (challenged by vasodilation and hypovolemia) provides the critical signals for impairing exercise-heat performance. "
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