Two groups of rats were used in the study ( N = 6 in each group): one receiving 1 mg/kg of amphetamine and second receiving 2 mg/kg of amphetamine. This approach helped us to identify a novel and counterintuitive mechanism underlying ergogenic effect of amphetamine, as well as provided new arguments on potential danger of using psychostimulants to improve performance during exercise. ![]() To do so, we collected experimental data on heat production and the core temperature in rats running on a treadmill, and calculated the unobserved parameters, such as muscle temperature and heat dissipation, using our previously published mathematical model (Yoo et al. In this study we aimed to find how amphetamine affects the mechanisms of exhaustion in exercising rats. Therefore, any alterations in the thermoregulatory system that lead to higher muscle temperatures can be extremely dangerous. Unfortunately, thermal or biochemical damage to the myocytes is not usually detected until post exercise. Misbalance of electrolytes can lead to cardiac arrhythmias, while a release of myoglobin may cause renal failure (Lima et al. Damage to the myocytes releases the content of the cells into the circulation. Muscle tissue itself can be damaged if its temperature becomes too high (Kregel 2002). Production of large amounts of heat by the muscles during exercise results in muscle tissue temperature being higher than core temperature. It has been previously shown that amphetamine increases the temperature at which exhaustion occurs at a high ambient temperature, producing a risk of developing exertional heat stroke (Zaretsky et al. 1974) by altering both heat production and heat dissipation. The balance between heat production and heat dissipation is crucial for keeping the temperature of different compartments of the body in a safe range.Īmphetamine is known to affect the thermoregulatory system (Borbely et al. To limit the temperature growth, regulatory heat dissipation mechanisms, for example, vasodilatation and evaporative cooling through saliva spreading in rodents or sweating in humans, are engaged to help remove heat during physical exercise (Young and Dawson 1982 Horowitz et al. During exercise, the temperature of the muscles as well as the core body temperature is elevated as a consequence of increased heat production in the muscles. High body temperature is one of the strongest exhaustion signals (Walters et al., 2000). ![]() However, the mechanism by which amphetamine increases the time to exhaustion is unknown. ![]() Although amphetamine usage is prohibited during competitions, it may be used in some situations to improve performance by delaying exhaustion (WADA, 2012). It was previously shown that low to moderate doses of amphetamine increase the time until exhaustion in exercising rats (Wyndham et al. In many conditions exhaustion may serve as an important safety mechanism keeping the organism from irreversible damage caused by intense exercise (Noakes 2012). However, this affects the integrity of thermoregulatory system and may result in potentially dangerous overheating of the muscles. Therefore, we conclude that amphetamine may mask or delay fatigue by slowing down exercise‐induced core body temperature growth by increasing heat dissipation. Furthermore, the model predicted that the muscle temperature at the end of the run in the amphetamine‐treated group was significantly higher than in the control group. Modeling revealed that amphetamine administration increases heat dissipation in the core. Using a mathematical model describing temperature dynamics in two compartments (the core and the muscles), we were able to infer what physiological parameters were affected by amphetamine. In contrast, a lower dose of amphetamine (1 mg/kg) had no effect on measured parameters. The administration of amphetamine slowed down the temperature rise (thus decreasing core body temperature) in the beginning of the run without affecting oxygen consumption. Due to a progressively increasing workload, which was matched by oxygen consumption, the control group exhibited a steady increase in the body temperature. Experimental results showed that rats treated with amphetamine (2 mg/kg) were able to run significantly longer than control rats. To explore this, we measured core body temperature and oxygen consumption of control and amphetamine‐trea ted rats running on a treadmill with an incrementally increasing load (both speed and incline). Considering that body temperature is one of the major determinants of exhaustion during exercise, we investigated the influence of amphetamine on the thermoregulation. ![]() Athletes use amphetamines to improve their performance through largely unknown mechanisms.
0 Comments
Leave a Reply. |