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Effects of aerobic fitness on hypohydration-induced physiological strain and exercise impairment.
Acta Physiol (Oxf). 2010 Feb; 198(2):179-90.AP

Abstract

AIM

Hypohydration exacerbates cardiovascular and thermal strain and can impair exercise capacity in temperate and warm conditions. Yet, athletes often dehydrate in exercise, are hypervolaemic and have less cardiovascular sensitivity to acute hypervolaemia. We tested the hypothesis that trained individuals have less cardiovascular, thermoregulatory and performance affect of hypohydration during exercise.

METHODS

After familiarization, six trained [VO(2 peak) = 64 (SD 8) mL kg(-1) min(-1)] and six untrained [O(2 peak) = 45 (4) mL kg(-1) min(-1)] males cycled 40 min at 70%O(2 peak) while euhydrated or hypohydrated by 1.5-2.0% body mass (crossover design), before a 40-min work trial with euhydration or ad libitum drinking (in Hypohydration trial), in temperate conditions (24.3 degrees C, RH 50%, v(a) = 4.5 m s(-1)). Baseline hydration was by complete or partial rehydration from exercise+heat stress the previous evening.

RESULTS

During constant workload, heart rate and its drift were increased in Hypohydration compared with Euhydration for Untrained [drift: 33 (11) vs. 24 beats min(-1) h(-1) (10), 95% CI 5-11] but not Trained [14 (3) vs. 13 beats min(-1) h(-1) (3), CI -2 to 3; P = 0.01 vs. Untrained]. Similarly, rectal temperature drift was faster in Hypohydration for Untrained only [by 0.57 degrees C h(-1) (0.25); P = 0.03 vs. Trained], concomitant with their reduced sweat rate (P = 0.05) and its relation to plasma osmolality (P = 0.03). Performance power tended to be reduced for Untrained (-13%, CI -35 to 2) and Trained (-7%, CI: -16 to 1), without an effect of fitness (P = 0.38).

CONCLUSION

Mild hypohydration exacerbated cardiovascular and thermoregulatory strain and tended to impair endurance performance, but aerobic fitness attenuated the physiological effects.

Authors+Show Affiliations

School of Physical Education, University of Otago, Dunedin, New Zealand.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

19807723

Citation

Merry, T L., et al. "Effects of Aerobic Fitness On Hypohydration-induced Physiological Strain and Exercise Impairment." Acta Physiologica (Oxford, England), vol. 198, no. 2, 2010, pp. 179-90.
Merry TL, Ainslie PN, Cotter JD. Effects of aerobic fitness on hypohydration-induced physiological strain and exercise impairment. Acta Physiol (Oxf). 2010;198(2):179-90.
Merry, T. L., Ainslie, P. N., & Cotter, J. D. (2010). Effects of aerobic fitness on hypohydration-induced physiological strain and exercise impairment. Acta Physiologica (Oxford, England), 198(2), 179-90. https://doi.org/10.1111/j.1748-1716.2009.02051.x
Merry TL, Ainslie PN, Cotter JD. Effects of Aerobic Fitness On Hypohydration-induced Physiological Strain and Exercise Impairment. Acta Physiol (Oxf). 2010;198(2):179-90. PubMed PMID: 19807723.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effects of aerobic fitness on hypohydration-induced physiological strain and exercise impairment. AU - Merry,T L, AU - Ainslie,P N, AU - Cotter,J D, Y1 - 2009/10/06/ PY - 2009/10/8/entrez PY - 2009/10/8/pubmed PY - 2010/5/1/medline SP - 179 EP - 90 JF - Acta physiologica (Oxford, England) JO - Acta Physiol (Oxf) VL - 198 IS - 2 N2 - AIM: Hypohydration exacerbates cardiovascular and thermal strain and can impair exercise capacity in temperate and warm conditions. Yet, athletes often dehydrate in exercise, are hypervolaemic and have less cardiovascular sensitivity to acute hypervolaemia. We tested the hypothesis that trained individuals have less cardiovascular, thermoregulatory and performance affect of hypohydration during exercise. METHODS: After familiarization, six trained [VO(2 peak) = 64 (SD 8) mL kg(-1) min(-1)] and six untrained [O(2 peak) = 45 (4) mL kg(-1) min(-1)] males cycled 40 min at 70%O(2 peak) while euhydrated or hypohydrated by 1.5-2.0% body mass (crossover design), before a 40-min work trial with euhydration or ad libitum drinking (in Hypohydration trial), in temperate conditions (24.3 degrees C, RH 50%, v(a) = 4.5 m s(-1)). Baseline hydration was by complete or partial rehydration from exercise+heat stress the previous evening. RESULTS: During constant workload, heart rate and its drift were increased in Hypohydration compared with Euhydration for Untrained [drift: 33 (11) vs. 24 beats min(-1) h(-1) (10), 95% CI 5-11] but not Trained [14 (3) vs. 13 beats min(-1) h(-1) (3), CI -2 to 3; P = 0.01 vs. Untrained]. Similarly, rectal temperature drift was faster in Hypohydration for Untrained only [by 0.57 degrees C h(-1) (0.25); P = 0.03 vs. Trained], concomitant with their reduced sweat rate (P = 0.05) and its relation to plasma osmolality (P = 0.03). Performance power tended to be reduced for Untrained (-13%, CI -35 to 2) and Trained (-7%, CI: -16 to 1), without an effect of fitness (P = 0.38). CONCLUSION: Mild hypohydration exacerbated cardiovascular and thermoregulatory strain and tended to impair endurance performance, but aerobic fitness attenuated the physiological effects. SN - 1748-1716 UR - https://www.unboundmedicine.com/medline/citation/19807723/Effects_of_aerobic_fitness_on_hypohydration_induced_physiological_strain_and_exercise_impairment_ L2 - https://doi.org/10.1111/j.1748-1716.2009.02051.x DB - PRIME DP - Unbound Medicine ER -