Physical performance of women following heat-exercise hypohydration.

Greenleaf, J. E.; Prange, E M; Averkin, E. G.

doi:10.1152/jappl.1967.22.1.55

Cited by 13 publications

(11 citation statements)

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“…Others have also found decreases in strength (6-11 %) with dehydration amounting to 1.5-3 % body weight [ 7 , 32 ] . Conversely, Greenleaf et al [ 20 ] and Montain et al [ 28 ] used exercise-heat exposure to induce a 3-4 % body weight defi cit and found no change in strength. However, the question of whether moderate dehydration impairs Introduction ▼ Net water balance, the diff erence between water loss and gain, is well maintained in humans as sensations of thirst and hunger allow for a daily body water balance variability between 0.2-0.7 % [ 8 , 31 ] .…”

Section: Skeletal Muscle Strength and Endurance Are Maintained Duringmentioning

confidence: 99%

Skeletal Muscle Strength and Endurance are Maintained during Moderate Dehydration

2012

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This study investigated the effects of moderate dehydration (~2.5% body weight) on muscle strength and endurance using percutaneous electrical stimulation to quantify central and peripheral fatigue, and isolate the combined effects of exercise-heat stress and dehydration, vs. the effect of dehydration alone. Force production and voluntary activation were calculated in 10 males during 1 brief and 15 repeated maximal voluntary isometric contractions performed prior to (control) walking in the heat (35°C), immediately following exercise, and the next morning (dehydration). The protocol was also performed in a euhydrated state. During the brief contractions, force production and voluntary activation were maintained in all trials. In contrast, force production decreased throughout the repeated contractions, regardless of hydration status (P<0.001). The decline in force was greater immediately following exercise-heat stress dehydration compared with control and euhydration (P<0.001). When dehydration was isolated from acute post-exercise dehydration, force production was maintained similarly to control and euhydration. Despite the progressive decline in force production and the increased fatigability observed during the repeated contractions, voluntary activation remained elevated throughout each muscle function test. Therefore, moderate dehydration, isolated from acute exercise-heat stress, does not appear to influence strength during a single contraction or enhance fatigability.

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Section: Skeletal Muscle Strength and Endurance Are Maintained Duringmentioning

confidence: 99%

Skeletal Muscle Strength and Endurance are Maintained during Moderate Dehydration

2012

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“…Studies measuring dehydration eVects on muscular strength or anaerobic performance are sparse and have yielded mixed results, showing signiWcant impairment (Bigard et al 2001;Bosco et al 1968Bosco et al , 1974Ftaiti et al 2001;Greenleaf et al 1967;Houston et al 1981;Judelson et al 2007b;SchoVstall et al 2001;Viitasalo et al 1987;Yoshida et al 2002), no eVects (Cheuvront et al 2006;Evetovich et al 2002;Greiwe et al 1998;Judelson et al 2007b; Montain et al 1998;Saltin 1964;Serfass et al 1984;Singer and Weiss 1968;Yoshida et al 2002) or even signiWcant improvements (Ahlman and Karvonen 1961;Widerman and Hagan 1982). Studies examining muscular endurance have shown signiWcant impairment (Bosco et al 1974;Caterisano et al 1988;Montain et al 1998;Torranin et al 1979) and no diVerence (Caterisano et al 1988;Ftaiti et al 2001;Greiwe et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Impact of dehydration on a full body resistance exercise protocol

et al. 2010

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This study examined effects of dehydration on a full body resistance exercise workout. Ten males completed two trials: heat exposed (with 100% fluid replacement) (HE) and dehydration (approximately 3% body mass loss with no fluid replacement) (DEHY) achieved via hot water bath (approximately 39 degrees C). Following HE and DEHY, participants performed three sets to failure (using predetermined 12 repetition maximum) of bench press, lat pull down, overhead press, barbell curl, triceps press, and leg press with a 2-min recovery between each set and 2 min between exercises. A paired t test showed total repetitions (all sets combined) were significantly lower for DEHY: (144.1 +/- 26.6 repetitions) versus HE: (169.4 +/- 29.1 repetitions). ANOVAs showed significantly lower repetitions (approximately 1-2 repetitions on average) per exercise for DEHY versus HE (all exercises). Pre-set rate of perceived exertion (RPE) and pre-set heart rate (HR) were significantly higher [approximately 0.6-1.1 units on average in triceps press, leg press, and approached significance in lat pull down (P = 0.14) and approximately 6-13 b min(-1) on average in bench press, lat pull down, triceps press, and approached significance for overhead press (P = 0.10)] in DEHY versus HE. Session RPE difference approached significance (DEHY: 8.6 +/- 1.9, HE: 7.4 +/- 2.3) (P = 0.12). Recovery HR was significantly higher for DEHY (116 +/- 15 b min(-1)) versus HE (105 +/- 13 b min(-1)). Dehydration (approximately 3%) impaired resistance exercise performance, decreased repetitions, increased perceived exertion, and hindered HR recovery. Results highlight the importance of adequate hydration during full body resistance exercise sessions.

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“…Studies from Greenleaf's first few years at ARC included the first NASA-funded study using female test subjects (9). Conducted in 1965, the study explored how dehydration impacted orthostatic and exercise performance of exercisetrained women.…”

Section: Arcmentioning

confidence: 99%

John Greenleaf's life of science

Watenpaugh

2012

Advances in Physiology Education

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This article summarizes the life and career of John E. Greenleaf, PhD. It complements an interview of Dr. Greenleaf sponsored by the American Physiological Society Living History Project found on the American Physiological Society website. Dr. Greenleaf is a "thought leader" and internationally renowned physiologist, with extensive contributions in human systems-level environmental physiology. He avoided self-aggrandizement and believed that deeds rather than words define one's legacy. Viewed another way, however, Greenleaf's words define his deeds: 48% of his 185 articles are first author works, which is an unusually high proportion for a scientist of his stature. He found that writing a thorough and thoughtful discussion section often led to novel ideas that drove future research. Beyond Greenleaf's words are the many students, postdocs, and collaborators lucky enough to have worked with him and thus learn and carry on his ways of science. His core principles included the following: avoid research "fads," embrace diversity, be the first subject in your own research, adhere to rules of fiscal responsibility, and respect administrative forces-but never back down from them when you know you are right. Greenleaf's integrity ensured he was usually right. He thrived on the axiom of many successful scientists: avoid falling in love with hypotheses, so that when unexpected findings appear, they arouse curiosity instead of fear. Dr. Greenleaf's legacy will include the John and Carol Greenleaf Award for prolific environmental and exercise-related publication in the Journal of Applied Physiology.

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Physical performance of women following heat-exercise hypohydration.

Cited by 13 publications

References 0 publications

Skeletal Muscle Strength and Endurance are Maintained during Moderate Dehydration

Skeletal Muscle Strength and Endurance are Maintained during Moderate Dehydration

Impact of dehydration on a full body resistance exercise protocol

John Greenleaf's life of science

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