<P> Amphetamine is a stimulant that has been found to improve both physical and cognitive performance . Amphetamine blocks the reuptake of dopamine and norepinephrine, which delays the onset of fatigue by increasing the amount of dopamine, despite the concurrent increase in norepinephrine, in the central nervous system . Amphetamine is a widely used substance among collegiate athletes for its performance enhancing qualities, as it can improve muscle strength, reaction time, acceleration, anaerobic exercise performance, power output at fixed levels of perceived exertion, and endurance . </P> <P> Methylphenidate has also been shown to increase exercise performance in time to fatigue and time trial studies . </P> <P> Caffeine is the most widely consumed stimulant in North America . Caffeine causes the release of epinephrine from the adrenal medulla . In small doses, caffeine can improve endurance . Recently, it has also been shown to delay the onset of fatigue in exercise . The most probable mechanism for the delay of fatigue is through the obstruction of adenosine receptors in the central nervous system . Adenosine is a neurotransmitter that decreases arousal and increases sleepiness . By preventing adenosine from acting, caffeine removes a factor that promotes rest and delays fatigue . </P> <P> Carbohydrates are the main source of energy in organisms for metabolism . They are an important source of fuel in exercise . A study conducted by the Institute of Food, Nutrition, and Human Health at Massey University investigated the effect of consuming a carbohydrate and electrolyte solution on muscle glycogen use and running capacity on subjects that were on a high carbohydrate diet . The group that consumed the carbohydrate and electrolyte solution before and during exercise experienced greater endurance capacity . This could not be explained by the varying levels of muscle glycogen; however, higher plasma glucose concentration may have led to this result . Dr. Stephen Bailey posits that the central nervous system can sense the influx of carbohydrates and reduces the perceived effort of the exercise, allowing for greater endurance capacity . </P>

How does weightlifting affect the central nervous system