Maximal fat oxidation during exercise (MFO) and the intensity of exercise that elicits MFO (Fatmax) has been recognized as potential determinants of endurance performance.

The purpose of this study was to determine the possible interaction between the effects of diurnal variation (morning vs. afternoon) and caffeine ingestion on MFO, Fatmax and VO2 max in endurance-trained men. Specifically, the investigators sought to elucidate whether the stimulant actions of caffeine could reverse the decrements of MFO and Fatmax observed in the morning.

Body weight, height, body composition (DXA), exercise test (MFO and VO2max assessment) will be measured during the 4 evaluations.

Participants were randomized into 4 exercise test conditions:

1. Exercise test in the morning with placebo intake
2. Exercise test in the evening with placebo intake
3. Exercise test in the morning with caffeine intake
4. Execrise test in the evening with caffeine intake

Inclusion Criteria:

• Having a body mass index (BMI) ranged from 18.5 to 28 kg/m2
• not suffering any specific disease which can be aggravated by physical exercise
• having previous experience in endurance training (i.e. self-reporting at least 2 years of cycling or running training including more than 3 training sessions/week).
• Participant must be capable and willing to provide consent, understand exclusion criteria, instructions and protocols.

Exclusion Criteria:

• Being smoker
• Taking medication or drugs
• Any non-controlled medical condition which could influence results or could be worsened by the participation in the study
• Are deemed unsuitable by the investigator for any other reason, that prevent data collection.