Effects of Heat Exposure and 3% Dehydration Achieved Via Hot Water Immersion on Repeated Cycle Sprint Performance

Kraft, Justin A.; Green, James Mathew; Bishop, Phillip A.; Richardson, Mark T.; Neggers, Yasmin H.; Leeper, James D.

doi:10.1519/jsc.0b013e3181c1f79d

Cited by 18 publications

(21 citation statements)

References 27 publications

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“…Hematocrit increases and there is a decline in mean power and peak power during exercise as well as a greater level of perceived exertion (200). HOWI in warm water has been shown to increase total urinary Aquaporin 2 excretion suggesting elevation of plasma vasopressin levels (391).…”

Section: Head-out Water Immersion In Warm Watermentioning

confidence: 99%

Human Physiology in an Aquatic Environment

Pendergast

Moon

Krasney

et al. 2015

Comprehensive Physiology

139

137

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Water covers over 70% of the earth, has varying depths and temperatures and contains much of the earth's resources. Head-out water immersion (HOWI) or submersion at various depths (diving) in water of thermoneutral (TN) temperature elicits profound cardiorespiratory, endocrine, and renal responses. The translocation of blood into the thorax and elevation of plasma volume by autotransfusion of fluid from cells to the vascular compartment lead to increased cardiac stroke volume and output and there is a hyperperfusion of some tissues. Pulmonary artery and capillary hydrostatic pressures increase causing a decline in vital capacity with the potential for pulmonary edema. Atrial stretch and increased arterial pressure cause reflex autonomic responses which result in endocrine changes that return plasma volume and arterial pressure to preimmersion levels. Plasma volume is regulated via a reflex diuresis and natriuresis. Hydrostatic pressure also leads to elastic loading of the chest, increasing work of breathing, energy cost, and thus blood flow to respiratory muscles. Decreases in water temperature in HOWI do not affect the cardiac output compared to TN; however, they influence heart rate and the distribution of muscle and fat blood flow. The reduced muscle blood flow results in a reduced maximal oxygen consumption. The properties of water determine the mechanical load and the physiological responses during exercise in water (e.g. swimming and water based activities). Increased hydrostatic pressure caused by submersion does not affect stroke volume; however, progressive bradycardia decreases cardiac output. During submersion, compressed gas must be breathed which introduces the potential for oxygen toxicity, narcosis due to nitrogen, and tissue and vascular gas bubbles during decompression and after may cause pain in joints and the nervous system.

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Section: Head-out Water Immersion In Warm Watermentioning

confidence: 99%

Human Physiology in an Aquatic Environment

Pendergast

Moon

Krasney

et al. 2015

Comprehensive Physiology

139

137

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“…Most previous studies which concluded that $3% loss of body mass impairs anaerobic performance, used exercise in heat (some in a heat chamber) to prompt body water loss (7,14,16,17,45). Kraft et al (21,22) used submersion in hot water bath. All participants completed performance tests on the same day of dehydration.…”

Section: Experimental Approach To the Problemmentioning

confidence: 99%

“…Similarly, as Kraft et al (22) found, heat exposure alone could diminish same day performance even when fluids are replaced at the rate of loss. Kraft et al (21,22) also included a recovery period allowing core temperature to return to near preheat exposure levels. Furthermore, residual effects of exercise-induced fatigue resulting from dehydration protocols may also impair subsequent performance.…”

Section: Experimental Approach To the Problemmentioning

confidence: 99%

“…Studies have reported anaerobic performance decrements associated with hypohydration (6,14,16,17,21,22,30,45), whereas others show no influence (6,7,14,17,18,44,45). A possible explanation for a portion of these equivocal results is the failure of some studies to achieve the level of body water loss (.3%) associated with diminished anaerobic performance (23,45).…”

Section: Introductionmentioning

confidence: 99%

“…In a review, Kraft et al (23) points out that it is difficult to determine the exact effects of hypohydration on anaerobic performance because of variations in exercise mode, mode of dehydration, and levels of hypohydration, among previous studies. Tests of anaerobic performance include one-repetition maximum weight lifting (14,30), full-body resistance exercise protocol (21), repeated back squats (18,21), unilateral leg extensions (14), vertical jump (7,14,18,44), 15-second Wingate tests (6,22), 30-second lower-body Wingate tests, and 30-second upper-body Wingate tests (16). In addition, various assessments of reaction time and skill (2,3,31,35,36) have been assessed.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Hypohydration on Repeated 40-yd Sprint Performance

Gann

Green

OʼNeal

et al. 2016

Journal of Strength and Conditioning Research

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This study examined the effects of hypohydration on repeated 40-yd sprint performance. Anaerobically fit current and former Division II male athletes (n = 12) completed 2 bouts of 10 × 40-yd sprints followed by an agility test, dehydrated (∼3% body weight [DT]), or hydrated trial (HT). Statistical analysis of group means indicated that hypohydration had little effect on sprint times for either the first (DT= 5.38 ± 0.37; HT = 5.35 ± 0.34) or second (DT = 5.47 ± 0.39; HT = 5.42 ± 0.39) bout of 10 sprints with only sprint number 2, 5, and 6 of bout 2 reaching statistical significance. However, when individual sprint performance was considered, a greater effect was seen. In all, 83% (10 of 12) of subjects experienced a meaningful change (≥0.1 seconds) (positive or negative) in mean sprint time (DT vs. HT) for one or more bout of 10 sprints. Ratings of perceived exertion was significantly higher (∼1 unit on a 10 point scale) for DT in all sprints during bout 1 and the first 2 sprints of bout 2. These results indicate that the effect of hypohydration on repeated sprint performance varies among individuals. Some improved performance with hypohydration, while others experienced detrimental effects. Hypohydration also resulted in a particularly notable negative impact on perceptual measures of exertion even when performance was similar.

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