title: Effects of caffeine ingestion on metabolic responses to prolonged walking in sedentary males.
abstract: This study examined the effects of a single dose of caffeine (5 mg.kg-1) on energy metabolism during 60-min treadmill walking at light (30% VO2max) and moderate (50% VO2max) aerobic intensities in eight sedentary (VO2max) 39.6 +/- 3.1 ml.kg-1 x min-1) males. Caffeine intake 60 min prior to walking exercise increased pre- and postexercise FFA, glycerol, and lactate concentrations (p < 0.05). Blood glucose levels following walking trials were lower than preexercise values (p < 0.05). Gas exchange indicated that caffeine did not change exercise oxygen uptake, RER values, and carbon dioxide production (p > 0.05). In contrast, a small but statistically significant effect of caffeine on exercise minute ventilation was noted (p < 0.01). It is concluded that ingestion of 5 mg.kg-1 caffeine increases the mobilization of energy substrate from fat sources; however, the present data do not provide evidence of a caffeine-induced shift in energy substrate usage. Caffeine is not an effective means for enhancing the energy cost of prolonged walking.
authors.affiliation: Div. of HPR-Exercise Science, Wayne State University, Detroit, MI 48202.
authors.forename: H J
authors.initials: HJ
authors.lastname: Engels
authors.forename: E M
authors.initials: EM
authors.lastname: Haymes
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology*; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D016138:Walking / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D006454:Hemoglobins; D007773:Lactates; D019344:Lactic Acid; D002110:Caffeine