NORADRENALINE IS INVOLVED WITH FATIGUE

Roelands, B., & Meeursen, R. (2009). The possible role of serotonine, dopamine, and noradrenaline in central fatigue. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

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This study examined the effects of acute administration of individual serotonin, dopamine, and noradrenaline reuptake inhibitors (5-HTRI, DARI, NARI) on performance and thermoregulation in normal and high ambient temperatures. In three separate studies, between 8 and 11 healthy trained male cyclists completed four experimental trials (two in 18C, two in 30C). Ss ingested either a placebo or a drug (Citalopram 5-HTRI, Reboxetine - NARI, Ritalin - DARI) on the morning of the trial. Ss cycled for 60 min at 55%Wmax, immediately followed by a time-trial to measure performance. Core temperature, skin temperature, heart rate, blood pressure, sweat loss, rating of perceived exertion, thermal stress, blood lactate and hormonal data were recorded.

The serotonin uptake inhibitor did not induce any significant change in performance in 18C or 30C. The dopamine uptake inhibitor improved performance in the high ambient temperature by more than seven minutes. Core temperatures rose significantly higher compared to placebo while no changes in ratings of perceived exertion and thermal stress were found. The noradrenaline uptake inhibitor decreased performance by three minutes in 18C and eight minutes in 30C.

Implication. Serotonin is unrelated to fatigue in prolonged exercise. Dopamine neurotransmission is capable of increasing motivation and drive to continue exercising, even at very high core temperatures, without changing the perception of effort or internal temperature. The manipulation of noradrenaline neurotransmission has negative effects on performance.

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