The purpose of this study was to examine the influence of caffeine (5 mg/kg body weight) on metabolism and cardiorespiratory variables during walking exercise at low and moderate aerobic intensities. In addition, caffeine's effect on perception of effort during walking was studied. Eight normotensive, sedentary (VO2max: 39.64, SD $+/-$ 3.05), male nonsmokers (age 21-28) with a habitual caffeine intake of less than 300mg/day participated in four 60-min treadmill walking sessions with and without prior caffeine. Two of these trials were performed at self-selected "normal" walking speed (2.90 mph, SD $+/-$ 0.12), corresponding to 30% VO2max exercise intensity; the other two tests were performed at self-selected "fast" walking speed (3.93 mph, SD $+/-$ 0.12), corresponding to a 50% VO2max work load. The order of trials was randomized and counterbalanced. The study was performed using a placebo double-blind design and data were analyzed using repeated measures ANOVA with each subject serving as his own control. / Caffeine intake 60 min prior to walking exercise increased pre- and post-exercise FFA, glycerol, and lactate concentrations (p $<$ 0.05). Walking exercise by itself raised serum levels of FFA and glycerol (p $<$ 0.05). Blood glucose concentration tended to be higher in caffeine trials (p = 0.06) and were lower post-exercise (p $<$ 0.05). Cardiorespiratory influences of caffeine included a rise in systolic blood pressure, pulse pressure, and minute ventilation during walking (p $<$ 0.05). Walking intensity level selectivity influenced energy substrate metabolism and cardiorespiratory responses. Significant time effects across the 60-min walking duration were noted for HR, RER, and the relative and absolute contribution of carbohydrate and fat for energy (p $<$ 0.05). The influence of caffeine on the perception of subjective effort during walking was statistically nonsignificant (p = 0.08). / It is concluded that ingestion of 5 mg/kg caffeine selectively influences metabolic and cardiorespiratory responses during walking exercise at 30% and 50% VO2max. The present data do not suggest that caffeine enhances the fat reducing potential of prolonged walking exercise. / Source: Dissertation Abstracts International, Volume: 50-10, Section: B, page: 4390. / Major Professor: Emily M. Haymes. / Thesis (Ph.D.)--The Florida State University, 1989.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_78088 |
| Contributors | Engels, Hermann-Josef., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 300 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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