“Background Most team sports include performance of moderate- to long duration exercise interspersed
with repeated bouts of high-intensity activities as well as periods of low-to-moderate active recovery or passive rest. The work: rest ratio of the team sport athlete is around selleck chemicals llc 1:4.5 , and average number of sprints completed during competition is approximately 20–60 times with an approximate sprint duration equal to 2 – 4-s . Girard et al.  reported that intermittent sprint exercise (ISE) differs greatly from repeated sprint exercise (RSE), that is, ISE is characterized by short-duration sprints (≤10-s) interspersed with long recovery periods (60–300-s); however, RSE is characterized by similar exercise duration (≤10-s) interspersed with insufficient recovery (≤60-s).
Gaitanos et al.  indicated that the inadequate recovery inherent in RSE (6-s maximal sprints AZD5153 solubility dmso with 30-s rest intervals) may impair sprint performance because of limited adenosine triphosphate (ATP) supply from anaerobic metabolism (glycolysis and phosphocreatine (PCr) resynthesis) during the transient recovery between sprints, and increased acidosis. Thus, the strategies of nutritional ingestion are needed to preserve repeated sprint performance in competitive athletes. It is common practice for team sport athletes to consume carbohydrate (CHO) to improve intermittent exercise capacity [5, 6] and endurance performance [7, 8], which is thought to occur via central nervous system (CNS) activation and other potential mechanisms such as higher rates of CHO oxidation [9, 10]. Another ergogenic aid that has routinely been used by athletes is caffeine (CAF) . Existing data show that CAF supplementation may benefit sprint performance [12, 13] and reactive agility performance  via various mechanisms . However, one study demonstrated that caffeine was ergolytic for mean power and fatigue index during the high-intensity sprint test when a 24 × 4-s cycling sprint test with 20-s of active recovery was completed versus a 90-s active recovery between each sprint bout . Numerous studies have also
reported that CAF ingestion has a small or negligible effect on sprint performance [16–18] when repeated sprint tests (≤10-s) are interspersed with short rest periods (-)-p-Bromotetramisole Oxalate (≤60-s), as well as no effect on reactive agility . Although CAF significantly improved ISE [12, 13, 20], a number of studies have suggested that CAF doses of 2–6 mg · kg−1 are likely to improve ISE but not RSE performance; in other words, caffeine ingestion may negatively affect repeated sprint performance with short recovery intervals in the later stages of exercise [16, 21]. If CHO plus CAF could potentiate benefits of CHO on substrate metabolism and improve CNS modulation, then CAF may enhance RSE performance. Some studies have examined changes in metabolism when CAF is coingested with CHO. For example, Yeo et al.