Effect of Caffeine Intake on Finger Cold-Induced Vasodilation

Abstract

The purpose of the study was to investigate the effect of caffeine intake on finger cold-induced vasodilation (CIVD). Ten healthy men underwent 6 experimental trials characterized by control (NCAFF) or caffeine intake (CAFF) via chewing gum (300 mg of caffeine) while resting on a chair or performing submaximal (70% maximal oxygen consumption) or maximal (100% maximal oxygen consumption) treadmill exercise (Bruce protocol) followed by immersion of the middle finger in a water bath (5°C) for 20 minutes. Finger temperature (Tf ) and time parameters of the first CIVD cycle and post-test norepinephrine were measured. Exercise duration for submaximal and maximal exercise was 8.9 ± 0.9 and 12.4 ± 0.8 minutes, respectively. CAFF had no effect on Tf, but exercise increased minimal Tf in NCAFF (9.08 ± 1.27°C, 13.02 ± 2.13°C, and 13.25 ± 1.63°C in rest, submaximal, and maximal exercise, respectively) and CAFF (8.76 ± 1.39°C, 12.50 ± 1.91°C, and 12.79 ± 1.20°C). Maximal Tf was significantly higher in NCAFF (15.98 ± 1.04°C, 16.18 ± 1.56°C, and 15.14 ± 1.52°C) than in CAFF (13.56 ± 1.19°C, 15.52 ± 1.31°C, and 14.39 ± 1.43°C), resulting in a significant difference between minimal and maximal Tf in rest (NCAFF, 6.89 ± 1.56°C and CAFF, 4.79 ± 1.23°C), but not in exercise conditions. CAFF had no effect on CIVD time responses, but exercise significantly shortened CIVD onset and peak time compared with rest in both NCAFF and CAFF. Norepinephrine concentration was significantly greater in CAFF (290.6 ± 113.0 pg/mL, 278.1 ± 91.4 pg/mL, and 399.8 ± 125.5 pg/mL) than NCAFF (105.6 ± 29.5 pg/mL, 199.6 ± 89.6 pg/mL, and 361.5 ± 171.3 pg/mL). Caffeine intake before finger immersion in cold water does not result in a thermogenic effect and adversely affects CIVD responses, whereas exercise modifies CIVD temperature and time responses.