In humans, studies that investigate links between serotonin and creatine supplementation find that 21 trained males, given creatine via 22.8g creatine monohydrate (20g creatine equivalent) with 35g glucose, relative to a placebo of 160g glucose, was found to reduce the perception of fatigue in hot endurance training, possibly secondary to serotonergic modulation, specifically attentuating the increase of serotonin seen with exercise (normally seen to hinder exercise capacity in the heat[233]) while possibly increasing dopaminergic activity (conversely seen to benefit activity in the heat[234]).[155]
Back in the 1970s, scientists discovered that taking creatine in supplement form might enhance physical performance. In the 1990s, athletes started to catch on, and creatine became a popular sports supplement. The supplement is particularly popular among high school, college, and professional athletes, especially football and hockey players, wrestlers, and gymnasts. 
Recommended Dose: In Shannon Clark's article, "6 Ways To Get More Energized For Your Workouts", Dr. Chris Lockwood recommends between 1.36 and 2.5 milligrams of caffeine per pound of bodyweight. That would be 200-375 milligrams for a 150-pound person. If that leaves you jittery, try less. Determine your tolerance and find the dose that works best for you.

Nitrate-rich foods like beets, radishes, and pomegranates are a great way to boost the production of nitric oxide (NO). Although there's very limited research examining the effects of beet root juice and pomegranate extract on resistance training, these ingredients have previously been shown to increase skeletal muscle blood flow and lead to reduced soreness, which may ultimately lead to improvements in strength and performance.[9,10]
Collectively the above investigations indicate that creatine supplementation can be an effective strategy to maintain total creatine pool during a rehabilitation period after injury as well as to attenuate muscle damage induced by a prolonged endurance training session. In addition, it seems that creatine can act as an effective antioxidant agent after more intense resistance training sessions.