It has been documented that CAF’s learn more influence on anaerobic exercise capacity and agility may depend on the rest: work ratio [11]. Similar to the results of previous studies by Lee et al.[16], Paton et al. [17], and Stuart et al. [21], CAF alone did not improve repeated sprint ability. Thus, while further applied research certainly

needs to be done, these results suggest that CAF provides negligible benefit to repeated sprint Fludarabine in vivo exercise with insufficient rest interval (work: rest ratio = 1:5). Although a meta-analysis indicated that CAF + CHO ingestion improved endurance performance when compared with CHO alone [44], the present study observed that CAF + CHO ingestion does not benefit repeated sprint performance versus CAF + PLA, PLA + CHO, or PLA + PLA. By contrast, the total work in PLA + CHO check details condition increased significantly at Set 3, compared to the CAF + CHO and CAF + PLA conditions.

Therefore, it is tempting to speculate that combining CAF with CHO supplementation has no additive effect on prolonged repeated sprint exercise, composed of 10 sets, 5 × 4-s sprints with 20-s rest interval between each sprint. Furthermore, a performance-enhancing effect of CHO seemed to be negated by CAF when recreational male athletes performed 20-kilometer time trial [29]. This apparent discrepancy may be attributed to type (that is, prolonged repeated sprint exercises) and intensity (i.e. high-intensity not and short recovery interval) of exercise performed in the present study, because previous study has indicated that anaerobic glycolysis supplies approximately 40% of the total energy during a single 6-s sprint, with a progressive inhibition of glycolysis and decreased ATP production with subsequent sprints [4]. Data also show that blood lactate concentration was not significantly different at pre-test and Set 1 among treatments, but was significantly higher after CAF + PLA ingestion than PLA + CHO and PLA + PLA during later stages of the RSE. Lee et al. [16] demonstrated a significant increase in blood lactate concentrations and decreased fatigue resistance during the late stage of the RSE after CAF ingestion. By contrast, this study

and others show that ingesting CHO does not affect the blood lactate response to sprint exercise [45, 46]. This may reflect rapidly increasing anaerobic glycolysis, where lactate is produced when ingesting CAF [47]. CAF may impair performance for this type of exercise due to increased accumulation of by-products of anaerobic metabolism [48], a deficiency in the phosphagen system [4], and blocking CNS adenosine receptors [49] or activating Na+/K+ ATPase [15]. Nevertheless, studies focused on the exact mechanism related with the effects of caffeine on energy substrate or nervous system should be conducted in future. The present study showed that repeated sprint performance was improved followed CHO ingestion rather than CAF + CHO ingestion or CAF ingestion alone.