Caffeine increases exercise intensity and energy expenditure but does not modify substrate oxidation during 1 h of self-paced cycling.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
oral caffeine intake | increase | fat oxidation during aerobic exercise with a steady-state intensity | - | - | has been deemed as an effective supplementation strategy to enhance | #1 |
caffeine intake | increase | the self-selected wattage | fifteen young and healthy participants (11 men and 4 women) | 105 ± 44 vs 117 ± 45 W | increased | #2 |
caffeine intake | increase | total work during the cycling session | fifteen young and healthy participants (11 men and 4 women) | 377 ± 157 vs 422 ± 160 kJ | represented a higher | #3 |
caffeine | increase | total energy expenditure | fifteen young and healthy participants (11 men and 4 women) | 543 ± 161 vs 587 ± 155 kcal | increased | #4 |
caffeine | no change | total fat oxidation | fifteen young and healthy participants (11 men and 4 women) | 24.7 ± 12.2 vs 22.9 ± 11.5 g | did not affect | #5 |
caffeine | no change | total carbohydrate oxidation | fifteen young and healthy participants (11 men and 4 women) | 87.4 ± 22.4 vs 97.8 ± 32.3 g | did not affect | #6 |
acute caffeine ingestion before an exercise session with an individual's freedom to regulate intensity | increase | self-selected exercise intensity | - | - | induces a higher | #7 |
acute caffeine ingestion before an exercise session with an individual's freedom to regulate intensity | increase | total work | - | - | induces a higher | #8 |
the selection of a higher exercise intensity | increase | total energy expenditure | - | - | augments | #9 |
the selection of a higher exercise intensity | no change | substrate oxidation during exercise | - | - | eliminates the effect of caffeine on | #10 |
AIM: Oral caffeine intake has been deemed as an effective supplementation strategy to enhance fat oxidation during aerobic exercise with a steady-state intensity. However, in real exercise scenarios, individuals habitually train with autoregulation of exercise intensity. This study aimed to analyze the effect of oral caffeine intake during self-paced cycling on autoregulated exercise intensity and substrate oxidation. METHODS: Fifteen young and healthy participants (11 men and 4 women) participated in a double-blind, randomized, cross-over investigation. Each participant took part in 2 experimental days consisting of pedaling for 1 h with a self-selected wattage. Participants were told that they had to exercise at a moderate intensity to maximize fat oxidation. On one occasion participants ingested 3 mg/kg of caffeine and on the other occasion ingested a placebo. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured during exercise by indirect calorimetry. RESULTS: In comparison to the placebo, caffeine intake increased the self-selected wattage (on average, 105 ± 44 vs 117 ± 45 W, respectively, P < 0.001) which represented a higher total work during the cycling session (377 ± 157 vs 422 ± 160 kJ, P < 0.001). Caffeine increased total energy expenditure (543 ± 161 vs 587 ± 155 kcal, P = 0.042) but it did not affect total fat oxidation (24.7 ± 12.2 vs 22.9 ± 11.5 g, P = 0.509) or total carbohydrate oxidation (87.4 ± 22.4 vs 97.8 ± 32.3 g, P = 0.101). CONCLUSION: Acute caffeine ingestion before an exercise session with an individual's freedom to regulate intensity induces a higher self-selected exercise intensity and total work. The selection of a higher exercise intensity augments total energy expenditure but eliminates the effect of caffeine on substrate oxidation during exercise.