Ingestion of a carbohydrate-electrolyte solution during exercise enabled subjects with compromised glycogen stores to better maintain skill and sprint performance than when ingesting fluid alone.
Caffeine ingestion before simulated soccer activity improved players' passing accuracy and jump performance without any detrimental effects on other performance parameters.
The exercise psychology literature includes an intriguing, albeit not frequently discussed, paradox by juxtaposing two conclusions: (a) that exercise makes most people feel better and (b) that most people are physically inactive or inadequately active. In this article, we propose that this might be an artifact rather than a paradox. Specifically, we question the generality of the conclusion that exercise makes people feel better by proposing that (a) occasional findings of negative affective changes tend to be discounted, (b) potentially relevant negative affective states are not always measured, (c) examining changes from pre-to postexercise could miss negative changes during exercise, and (d) analyzing changes only at the level of group aggregates might conceal divergent patterns at the level of individuals or subgroups. Data from a study of 12 men participating in a 90-min walk-run protocol designed to simulate the demands of sports games (e.g., soccer) are used to illustrate these points.
Carbohydrate and caffeine are known to independently improve certain aspects of athletic performance. However, less is understood about physiological and performance outcomes when these compounds are coingested in a rehydration and carbohydrate-replacement strategy. The aim of this study was to examine the influence of adding a moderate dose of caffeine to a carbohydrate solution during prolonged soccer activity. Fifteen male soccer players performed two 90-min intermittent shuttle-running trials. They ingested a carbohydrate-electrolyte solution (CON) providing a total of 1.8 g/kg body mass (BM) of carbohydrate or a similar solution with added caffeine (CAF; 3.7 mg/kg BM). Solutions were ingested 1 hr before exercise and every 15 min during the protocol. Soccer passing skill and countermovement-jump height (CMJ) were quantified before exercise and regularly during exercise. Sprinting performance, heart rate, blood lactate concentration (La) and the subjective experiences of participants were measured routinely. Mean 15-m sprint time was faster during CAF (p = .04); over the final 15 min of exercise mean sprint times were CAF 2.48 +/- 0.15 s vs. CON 2.59 +/- 0.2 s. Explosive leg power (CMJ) was improved during CAF (52.9 +/- 5.8 vs. CON 51.7 +/- 5.7 cm, p = .03). Heart rate was elevated throughout CAF, and ratings of pleasure were significantly enhanced. There were no significant differences in passing skill, rating of perceived exertion, La, or body-mass losses between trials. The addition of caffeine to the carbohydrate-electrolyte solution improved sprinting performance, countermovement jumping, and the subjective experiences of players. Caffeine appeared to offset the fatigue-induced decline in self-selected components of performance.
These results suggest that CHO-E ingestion improves endurance capacity during intermittent high-intensity running in subjects with high preexercise muscle glycogen concentrations. The greater endurance capacity cannot be explained solely by differences in muscle glycogen, and it may actually be a consequence of the higher plasma glucose concentration towards the end of exercise that provided a sustained source of CHO for muscle metabolism and for the central nervous system.
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