Type your tag names separated by a space and hit enter

Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat.

Abstract

PURPOSE

This study was conducted to determine whether preexercise ingestion of a highly concentrated sodium beverage would increase plasma volume (PV) and reduce the physiological strain of moderately trained males running in the heat.

METHODS

Eight endurance-trained (.VO2max: 58 mL.kg(-1).min(-1) (SD 5); 36 yr (SD 11)) runners completed this double-blind, crossover experiment. Runners ingested a high-sodium (High Na+: 164 mmol Na+.L(-1)) or low-sodium (Low Na+: 10 mmol Na+.L(-1)) beverage (10 mL.kg(-1)) before running to exhaustion at 70% .VO2max in warm conditions (32 degrees C, 50% RH, V(a) approximately equal to 1.5 m.s(-1)). Beverages (approximately 757 mL) were ingested in seven portions across 60 min beginning 105 min before exercise. Trials were separated by 1-3 wk. Heart rate and core and skin temperatures were measured throughout exercise. Urine and venous blood were sampled before and after drinking and exercise.

RESULTS

High Na+ increased PV before exercise (4.5% (SD 3.7)), calculated from Hct and [Hb]), whereas Low Na+ did not (0.0% (SD 0.5); P = 0.04), and involved greater time to exercise termination in the six who stopped because of an ethical end point (core temperature 39.5 degrees C: 57.9 min (SD 6) vs 46.4 min (SD 4); P = 0.04) and those who were exhausted (96.1 min (SD 22) vs 75.3 min (SD 21); P = 0.03; High Na+ vs Low Na+, respectively). At equivalent times before exercise termination, High Na+ also resulted in lower core temperature (38.9 vs 39.3 degrees C; P = 0.00) and perceived exertion (P = 0.01) and a tendency for lower heart rate (164 vs 174 bpm; P = 0.08).

CONCLUSIONS

Preexercise ingestion of a high-sodium beverage increased plasma volume before exercise and involved less thermoregulatory and perceived strain during exercise and increased exercise capacity in warm conditions.

Links

  • Publisher Full Text
  • Authors+Show Affiliations

    ,

    School of Physical Education, Department of Human Nutrition, University of Otago, Dunedin, New Zealand.

    , ,

    Source

    MeSH

    Adult
    Cross-Over Studies
    Double-Blind Method
    Exercise
    Hot Temperature
    Humans
    Male
    Middle Aged
    Monitoring, Physiologic
    New Zealand
    Physiological Phenomena
    Placebos
    Sodium
    Water-Electrolyte Balance

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    17218894

    Citation

    Sims, Stacy T., et al. "Sodium Loading Aids Fluid Balance and Reduces Physiological Strain of Trained Men Exercising in the Heat." Medicine and Science in Sports and Exercise, vol. 39, no. 1, 2007, pp. 123-30.
    Sims ST, van Vliet L, Cotter JD, et al. Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat. Med Sci Sports Exerc. 2007;39(1):123-30.
    Sims, S. T., van Vliet, L., Cotter, J. D., & Rehrer, N. J. (2007). Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat. Medicine and Science in Sports and Exercise, 39(1), pp. 123-30.
    Sims ST, et al. Sodium Loading Aids Fluid Balance and Reduces Physiological Strain of Trained Men Exercising in the Heat. Med Sci Sports Exerc. 2007;39(1):123-30. PubMed PMID: 17218894.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat. AU - Sims,Stacy T, AU - van Vliet,Linda, AU - Cotter,James D, AU - Rehrer,Nancy J, PY - 2007/1/16/pubmed PY - 2007/3/17/medline PY - 2007/1/16/entrez SP - 123 EP - 30 JF - Medicine and science in sports and exercise JO - Med Sci Sports Exerc VL - 39 IS - 1 N2 - PURPOSE: This study was conducted to determine whether preexercise ingestion of a highly concentrated sodium beverage would increase plasma volume (PV) and reduce the physiological strain of moderately trained males running in the heat. METHODS: Eight endurance-trained (.VO2max: 58 mL.kg(-1).min(-1) (SD 5); 36 yr (SD 11)) runners completed this double-blind, crossover experiment. Runners ingested a high-sodium (High Na+: 164 mmol Na+.L(-1)) or low-sodium (Low Na+: 10 mmol Na+.L(-1)) beverage (10 mL.kg(-1)) before running to exhaustion at 70% .VO2max in warm conditions (32 degrees C, 50% RH, V(a) approximately equal to 1.5 m.s(-1)). Beverages (approximately 757 mL) were ingested in seven portions across 60 min beginning 105 min before exercise. Trials were separated by 1-3 wk. Heart rate and core and skin temperatures were measured throughout exercise. Urine and venous blood were sampled before and after drinking and exercise. RESULTS: High Na+ increased PV before exercise (4.5% (SD 3.7)), calculated from Hct and [Hb]), whereas Low Na+ did not (0.0% (SD 0.5); P = 0.04), and involved greater time to exercise termination in the six who stopped because of an ethical end point (core temperature 39.5 degrees C: 57.9 min (SD 6) vs 46.4 min (SD 4); P = 0.04) and those who were exhausted (96.1 min (SD 22) vs 75.3 min (SD 21); P = 0.03; High Na+ vs Low Na+, respectively). At equivalent times before exercise termination, High Na+ also resulted in lower core temperature (38.9 vs 39.3 degrees C; P = 0.00) and perceived exertion (P = 0.01) and a tendency for lower heart rate (164 vs 174 bpm; P = 0.08). CONCLUSIONS: Preexercise ingestion of a high-sodium beverage increased plasma volume before exercise and involved less thermoregulatory and perceived strain during exercise and increased exercise capacity in warm conditions. SN - 0195-9131 UR - https://www.unboundmedicine.com/medline/citation/17218894/Sodium_loading_aids_fluid_balance_and_reduces_physiological_strain_of_trained_men_exercising_in_the_heat_ L2 - http://Insights.ovid.com/pubmed?pmid=17218894 DB - PRIME DP - Unbound Medicine ER -