High intensity intervall training is a system of cardiorespiratory training which calls for repeated bouts of short duration, high-intensity exercise intervals alternating with periods of lower intensity intervals of active recovery. When using max heart rate (MHR) as a guide, high intensity can be considered exercising above 80% of MHR. Most reviews and trials found that HIIT regimens of one month or longer effectively improve cardiovascular fitness and are superior to traditional endurance training. In comparison to moderate intensity continuous training HIIT leads to greater improvements in VO2 max, but less reduction in body weight and heart rate.
Hypotetical question, if results of HIIT can be further improved with creatinine supplementation was adressed in some trials. Phosphocreatine (PCr), a high-energy storage molecule within skeletal muscle, provides immediate replenishment
of ATP during intense exercise. Multiple HIIT bouts are designed to deplete PCr stores in the working skeletal muscle, reducing power output. It takes about six minutes to fully recover depleted PCr stores after exercise-induced PCr
depletion. Therefore, if recovery intervals during HIIT bouts are less than six minutes, PCr may not be fully
replenished, resulting in reduced strengh and endurance.
There is little supporting evidence for creatine supplementation. Some reviews show positive effect on resistance training for enhancing strength and muscle mass. There are only few trials investigating creatine supplementation in HIIT and supporting previous evidence that HIIT is an efficient way to induce cardiorespiratory improvements. Findings suggest that prolonged creatine ingestion induces slightly increase in fat-free mass. Other study showed absolutely no benefits of supplementation.
HIIT is very effective training method by itself. Based on current scientific data we can not routinely recommend creatine supplementation during HIIT. When used, creatine should be beginned in high loading dose (4 to 5 times daily 5 g each)and followed by long maintenance period. Although perception of safety cannot be guaranteed especially that of the long term safety of creatine supplementation.
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Greaf J et al. The effects of four weeks of creatine supplementation and high-intensity interval training on cardiorespiratory fitness: a randomized controlled trial. Journal of the International Society of Sports Nutrition 2009, 6:18 doi:10.1186/1550-2783-6-18