[Show abstract][Hide abstract] ABSTRACT: This study examined the effects of caffeine, co-ingested with a high fat meal, on perceptual and metabolic responses during incremental (Experiment 1) and endurance (Experiment 2) exercise performance. Trained participants performed three constant-load cycling tests at approximately 73% of maximal oxygen uptake (VO2max) for 30 min at 20 degrees C (Experiment 1, n = 8) and to the limit of tolerance at 10 degrees C (Experiment 2, n = 10). The 30 min constant-load exercise in Experiment 1 was followed by incremental exercise (15 W . min-1) to fatigue. Four hours before the first test, the participants consumed a 90% carbohydrate meal (control trial); in the remaining two tests, the participants consumed a 90% fat meal with (fat + caffeine trial) and without (fat-only trial) caffeine. Caffeine and placebo were randomly assigned and ingested 1 h before exercise. In both experiments, ratings of perceived leg exertion were significantly lower during the fat + caffeine than fat-only trial (Experiment 1: P < 0.001; Experiment 2: P < 0.01). Ratings of perceived breathlessness were significantly lower in Experiment 1 (P < 0.01) and heart rate higher in Experiment 2 (P < 0.001) on the fat + caffeine than fat-only trial. In the two experiments, oxygen uptake, ventilation, blood [glucose], [lactate] and plasma [glycerol] were significantly higher on the fat + caffeine than fat-only trial. In Experiment 2, plasma [free fatty acids], blood [pyruvate] and the [lactate]:[pyruvate] ratio were significantly higher on the fat + caffeine than fat-only trial. Time to exhaustion during incremental exercise (Experiment 1: control: 4.9, s = 1.8 min; fat-only: 5.0, s = 2.2 min; fat + caffeine: 5.0, s = 2.2 min; P > 0.05) and constant-load exercise (Experiment 2: control: 116 (88 - 145) min; fat-only: 122 (96 - 144) min; fat + caffeine: 127 (107 - 176) min; P > 0.05) was not different between the fat-only and fat + caffeine trials. In conclusion, while a number of metabolic responses were increased during exercise after caffeine ingestion, perception of effort was reduced and this may be attributed to the direct stimulatory effect of caffeine on the central nervous system. However, this caffeine-induced reduction in effort perception did not improve exercise performance.
Journal of Sports Sciences 09/2006; 24(8):875-87. · 2.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study aimed to investigate the acute effects of a single exercise class on appetite sensations, energy intake and mood, and to determine if there was a time of day effect. Twelve healthy, young, normal weight females, who were non-regular exercisers, participated in four trials: morning control, morning exercise, evening control and evening exercise. Exercise trials were a one-hour class of aerobic and muscle conditioning exercise of varying intensities, to music. Control trials were a one-hour rest. Ratings of perceived exertion were significantly greater during the warm-up and muscle conditioning parts of the morning exercise trial compared to those of the evening exercise trial. Although both exercise trials, compared to control trials, produced an increase in appetite sensations, they did not alter energy intake and produced a decrease in 'relative' energy intake. In relation to mood, both exercise trials increased positive affect and decreased negative affect. These results suggest that a single exercise class, representative of that offered by many sports centres, regardless of whether it is performed in the morning or evening produces a short-term negative energy balance and improves mood in normal weight women. However, when this type of exercise was performed in the morning it was perceived to require more effort.
[Show abstract][Hide abstract] ABSTRACT: To investigate whether moderate physical activity or snack intake influence appetite sensations and subsequent food intake in obese women. Associations between serum leptin and appetite ratings were also investigated.
In all, 10 obese women (mean age+/-s.d.: 50.0+/-8.5 y; mean body mass index (BMI)+/-s.d.: 37.2+/-6.5 kg m(-2)) were submitted in random order to three trials: Moderate physical activity (20 min brisk walking), Snack (58.5 g chocolate-based) and Control (sitting, TV-watching). Appetite and satiety were assessed by visual analogue scales, and serum leptin, blood glucose and plasma free fatty acids were measured at baseline, pre- and postintervention and 1 h postintervention (ie, before dinner). A buffet-style dinner was provided subsequent to the three trials.
The moderate physical activity and snack intake both produced lower appetite and higher satiety and fullness perceptions, compared to control, following the intervention. No significant differences were found in subsequent food intake. Serum leptin concentrations did not differ between trials. Serum leptin was not associated with appetite or satiety sensations at any time during the control or the snack trials, but was correlated following moderate physical activity (prospective food consumption r(s)=-0.83, P=0.003; hunger r(s)=-0.79, P=0.007; desire to eat r(s)=-0.69, P=0.02; satiety r(s)=0.71, P=0.02; fullness r(s)=0.66, P=0.04). These associations were not influenced by BMI or fat mass.
Moderate physical activity and snack intake suppress the appetite of obese women acutely. The associations between circulating leptin and appetite-satiety ratings suggest leptin involvement in short-term appetite regulation in response to physical activity-induced factors.
International Journal of Obesity 12/2003; 27(11):1332-9. · 5.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Endurance-trained athletes experience a low level of postprandial lipaemia, but this rapidly increases with detraining. We sought to determine whether detraining-induced changes to postprandial metabolism influenced endothelial function and inflammation. Eight endurance-trained men each undertook two oral fat tolerance tests [blood taken fasted and for 6 h following a high-fat test meal (80 g fat, 80 g carbohydrate)]: one during a period of their normal training (trained) and one after 1 wk of no exercise (detrained). Endothelial function in the cutaneous microcirculation was assessed using laser Doppler imaging with iontophoresis in the fasted state and 4 h postprandially during each test. Fasting plasma triglyceride (TG) concentrations increased by 35% with detraining (P = 0.002), as did postprandial plasma (by 53%, P = 0.002), chylomicron (by 68%, P = 0.02) and very low-density lipoprotein (by 51%, P = 0.005) TG concentrations. Endothelial function decreased postprandially in both the trained (by 17%, P = 0.03) and detrained (by 22%, P = 0.03) conditions but did not differ significantly between the trained and detrained conditions in either the fasted or the postprandial states. These results suggest that, although fat ingestion induces endothelial dysfunction, interventions that alter postprandial TG metabolism will not necessarily concomitantly influence endothelial function.