The effects of caffeine ingestion on time trial cycling performance.

AIM: The purpose of this work was to determine the effects of caffeine ingestion on cycling time trial (TT) performance in well trained male subjects. METHODS: Eight males, with the following physical characteristics (Mean +/- SD) age 30.2+/-10.1 years, height 180.3+/-7.1 cm, mass 70.4+/-5.1 kg, VO2max 63.6+/-4.4 mL.kg(-1).min(-1) undertook three 1 h TT performances on a VelotronPro cycle ergometer, in a double blind, random fashion. The trials were Control (C), Placebo (Pl) and Caffeine (CAF). The CAF and Pl were given 60 min prior to exercise in a dose of 6 mg.kg(-1) body mass. Prior to ingestion, 60 min post ingestion, and at the end of the TT, subjects gave 10 mL of venous blood which was analysed for lactate, glucose, and free fatty acids. Expired air was collected throughout each test by indirect calorimetry. RESULTS: The cyclists rode significantly further in CAF trial (28.11+/-1.32 km) than they did in the C (26.69+/-1.5 km, P < 0.03) or Pl (27.0+/-1.5 km, P < 0.03) trials. No significant differences were seen between C and Pl trials (P > 0.88). No differences between C and Pl were seen in heart rate data throughout the TT (p > 0.05). The free fatty acid (FFA) concentrations were significantly higher in the CAF trials both post ingestion (P < 0.005) and post exercise (P < 0.0001) than either C or Pl trials. CONCLUSION: We concluded that performance was improved possibly based upon a greater reliance on fat metabolism, as indicated by increased FFA and a lower respiratory exchange ratio (RER).

The effects of caffeine ingestion on time trial cycling performance.

PURPOSE: The purpose of this work was to determine the effects of caffeine on high intensity time trial (TT) cycling performance in well-trained subjects. SUBJECTS: Six male cyclists with the following physical characteristics (mean +/- SD) age 30.7 +/- 12, height 179.3 +/- 7.5 cm, mass 70.0 +/- 7.5 kg, VO2max 65.0 +/- 6.3 mL.kg-1.min-1 undertook three 1-h TT performances, control (C), placebo (P) and caffeine (CAF), on a Velotron cycle ergometer conducted in a double-blind, random fashion. Subjects rested for 60 min and were then given CAF or P in a dose of 6 mg.kg-1 body mass and then commenced exercise after another 60 min of rest. Before ingestion, 60 min postingestion, and at the end of the TT, finger-prick blood samples were analyzed for lactate. RESULTS: The cyclists rode significantly further in the CAF trial (28.0 +/- 1.3 km) than they did in the C (26.3 +/- 1.5 km, P < .01) or P (26.4 +/- 1.5 km, P < .02) trials. No differences were seen in heart rate data throughout the TT (P > .05). Blood lactate levels were significantly higher at the end of the trials than either at rest or postingestion (P < .0001), but there were no differences between the three trial groups. CONCLUSION: On the basis of the data, we concluded that performance was improved with the use of a caffeine supplement.

Soccer half-time strategy influences thermoregulation and endurance performance.

AIM: In the first 15 min of the second half in professional soccer, there is a reduction of high intensity distance covered and a high incidence of injuries sustained, possibly due to a reduction in body temperature during the half-time (HT). The aim of this study was to investigate the effect of active and passive re-warm-up strategies on cardiovascular (heart rate, HR) and thermoregulatory stress, and second-half soccer-specific endurance performance (SSEP). METHODS: Seven professional players performed two intermittent field tests of 16.5 min duration, with a 15 min HT. On separate, randomised occasions, 4 trials were completed during which different HT strategies were undertaken between minutes 7 and 14 of the HT interval. Two passive trials were completed: rest control trial (CON), or players were immersed to the gluteal fold in a hot bath (approximately 40 degrees C-passive heating, PH); in the active trials, players performed at 70% maximum HR, either steady-state non-specific active heating (cycling, NSAH) or intermittent soccer-specific active heating (sprinting repeatedly, SSAH). HR and core temperature (Tc) were measured every 5 min, and body weight was recorded pre and post each trial. RESULTS: Active re-warm-up strategies maintained SSEP in the second period with respect to CON (P<0.01), whereas PH did not reduce the decrement in performance (P>0.05). Active heating strategies increased HR during HT in comparison to CON, whereas PH did not. During the HT period in the CON trial, T(c) decreased by 0.97+/-0.29 degrees C, PH and SSAH trials did not attenuate this decrease (P>0.01), whereas NSAH increased T(c) in respect to CON (P<0.01). These differences in HR and T(c) between re-warm-up strategies during HT were not apparent at the end of the trials. CONCLUSION: Active re-warm-up strategies during HT attenuated the decrement in second-half SSEP that was observed during passive trials.