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Caffeine effects on short-term performance during prolonged exercise in the heat.
Med Sci Sports Exerc. 2008 Apr; 40(4):744-51.MS

Abstract

PURPOSE

To determine the effect of water, carbohydrate, and caffeine ingestion on fatigue during prolonged exercise in the heat.

METHODS

Seven endurance-trained cyclists (V O2max = 61 +/- 8 mL.kg.min) pedaled for 120 min at 63% V O2max in a hot-dry environment (36 degrees C; 29% humidity), ingesting either no fluid (NF), water (WAT) to replace 97% fluid losses, the same volume of a 6% carbohydrate-electrolyte solution (CES), or each of these treatments along with ingestion of 6 mg of caffeine per kilogram of body weight (NF + CAFF, WAT + CAFF, and CES + CAFF). At regular intervals during exercise, maximal cycling power (PMAX) was measured. Before and after exercise, maximal voluntary contraction (MVC), voluntary activation (VA), and electrically evoked contractile properties of the quadriceps were determined.

RESULTS

Without fluid replacement (NF and NF + CAFF), subjects were dehydrated by 3.8 +/- 0.3%, and rectal temperature reached 39.4 +/- 0.3 degrees C, while it was maintained at 38.7 +/- 0.3 degrees C in trials with rehydration (P < 0.05). Trials with caffeine ingestion increased PMAX by 3% above trials without caffeine (P < 0.05). MVC reductions after exercise were larger with NF (-11 +/- 5%) than for the rest of the trials (P < 0.05). MVC was reduced in WAT compared with CES + CAFF (-6 +/- 4 vs 2 +/- 4%; P < 0.05). However, NF + CAFF maintained MVC at the level of the CES trial. VA showed the same treatment response pattern as MVC. There were no differences in electrically evoked contractile properties among trials.

CONCLUSION

During prolonged exercise in the heat, caffeine ingestion (6 mg.kg body weight) maintains MVC and increases PMAX despite dehydration and hyperthermia. When combined with water and carbohydrate, caffeine ingestion increases maximal leg force by increasing VA (i.e., reducing central fatigue).

Authors+Show Affiliations

Universidad de Castilla-La Mancha, Toledo, Spain.No affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

18317369

Citation

Del Coso, Juan, et al. "Caffeine Effects On Short-term Performance During Prolonged Exercise in the Heat." Medicine and Science in Sports and Exercise, vol. 40, no. 4, 2008, pp. 744-51.
Del Coso J, Estevez E, Mora-Rodriguez R. Caffeine effects on short-term performance during prolonged exercise in the heat. Med Sci Sports Exerc. 2008;40(4):744-51.
Del Coso, J., Estevez, E., & Mora-Rodriguez, R. (2008). Caffeine effects on short-term performance during prolonged exercise in the heat. Medicine and Science in Sports and Exercise, 40(4), 744-51. https://doi.org/10.1249/MSS.0b013e3181621336
Del Coso J, Estevez E, Mora-Rodriguez R. Caffeine Effects On Short-term Performance During Prolonged Exercise in the Heat. Med Sci Sports Exerc. 2008;40(4):744-51. PubMed PMID: 18317369.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Caffeine effects on short-term performance during prolonged exercise in the heat. AU - Del Coso,Juan, AU - Estevez,Emma, AU - Mora-Rodriguez,Ricardo, PY - 2008/3/5/pubmed PY - 2008/6/21/medline PY - 2008/3/5/entrez SP - 744 EP - 51 JF - Medicine and science in sports and exercise JO - Med Sci Sports Exerc VL - 40 IS - 4 N2 - PURPOSE: To determine the effect of water, carbohydrate, and caffeine ingestion on fatigue during prolonged exercise in the heat. METHODS: Seven endurance-trained cyclists (V O2max = 61 +/- 8 mL.kg.min) pedaled for 120 min at 63% V O2max in a hot-dry environment (36 degrees C; 29% humidity), ingesting either no fluid (NF), water (WAT) to replace 97% fluid losses, the same volume of a 6% carbohydrate-electrolyte solution (CES), or each of these treatments along with ingestion of 6 mg of caffeine per kilogram of body weight (NF + CAFF, WAT + CAFF, and CES + CAFF). At regular intervals during exercise, maximal cycling power (PMAX) was measured. Before and after exercise, maximal voluntary contraction (MVC), voluntary activation (VA), and electrically evoked contractile properties of the quadriceps were determined. RESULTS: Without fluid replacement (NF and NF + CAFF), subjects were dehydrated by 3.8 +/- 0.3%, and rectal temperature reached 39.4 +/- 0.3 degrees C, while it was maintained at 38.7 +/- 0.3 degrees C in trials with rehydration (P < 0.05). Trials with caffeine ingestion increased PMAX by 3% above trials without caffeine (P < 0.05). MVC reductions after exercise were larger with NF (-11 +/- 5%) than for the rest of the trials (P < 0.05). MVC was reduced in WAT compared with CES + CAFF (-6 +/- 4 vs 2 +/- 4%; P < 0.05). However, NF + CAFF maintained MVC at the level of the CES trial. VA showed the same treatment response pattern as MVC. There were no differences in electrically evoked contractile properties among trials. CONCLUSION: During prolonged exercise in the heat, caffeine ingestion (6 mg.kg body weight) maintains MVC and increases PMAX despite dehydration and hyperthermia. When combined with water and carbohydrate, caffeine ingestion increases maximal leg force by increasing VA (i.e., reducing central fatigue). SN - 0195-9131 UR - https://www.unboundmedicine.com/medline/citation/18317369/Caffeine_effects_on_short_term_performance_during_prolonged_exercise_in_the_heat_ L2 - http://dx.doi.org/10.1249/MSS.0b013e3181621336 DB - PRIME DP - Unbound Medicine ER -