D-30 Free Communication/Poster- Heat Stress and Fluid Balance: Physiological and Biochemical Responses to Heat Strain: MAY 29, 2008 1:00 PM- 6:00 PM ROOM: Hall B
Previous research showed that acute dopamine/noradrenaline (DA/NA) reuptake inhibition (acute bupropion (BUP) administration) enabled subjects to maintain a greater power output during a time trial performance in the heat. This 9% improvement in performance did not cause any changes in the perception of effort and thermal sensation reported during the placebo trial, despite the attainment of a higher core temperature equal to, or higher than 40°C. It appears that in an acute situation, BUP might be dampening the inhibitory signals arising from the central nervous system to cease exercise due to hyperthermia.
PURPOSE: BUP is a drug that is most commonly administered chronically. Since we know its potentially harmful effects after acute administration, it becomes important to investigate the effects of chronic BUP administration on exercise performance and thermoregulation in warm environmental temperatures.
METHODS: Eight trained, non smoking male cyclists (Age 27±5y; Ht 180±10cm; Body Mass 74.9±7.9kg; Wmax 346±48W) participated in the study. Subjects completed 2 trials (30°C; 50-60%RH) consisting of 60min fixed intensity exercise followed by a time trial in a double blind-randomized crossover design. Subjects took either placebo or BUP for 3 days (150mg), followed by 300mg for 7days.
RESULTS: Chronic BUP did not change performance on a preloaded time trial (BUP 40'42"±4'18"; placebo 41'36"±5'12") and significantly increased core temperature and growth hormone levels compared to the placebo situation (p=0.030 and p<0.08).
CONCLUSIONS: Chronic BUP did not influence performance and subjects did not reach core temperature values as high as observed during the acute BUP study in the heat. This might be explained by a more important influence of the NA system through BUPs major metabolite, hydroxybupropion (HB), which acts on the NA transporter. Although less extreme, BUP still significantly increases Tcore compared to PLAC.
This study was supported by research funding from the Vrije Universiteit Brussel (OZR607, OZR 990 and OZR 1236).