Muscle lactate and glycogen Muscle lactate (Figure 7a) concentration increased for both creatine and placebo groups from rest to the end of the two-hour cycling bout before supplementation; however, after supplementation both groups exhibited less of an increase in muscle lactate during the two-hour cycling bout. Muscle glycogen content (Figure 7b) was AZD1480 reduced (P < 0.05) by approximately 600 mmol/kg dry mass both before and after supplementation in creatine and placebo groups. After supplementation, muscle glycogen content at the end of the two-hour ride was higher in the creatine than

placebo group (P < 0.05) due to the higher resting muscle glycogen content after supplementation in the creatine than placebo group. Figure 7 a and b. Mean muscle lactate (Figure 7a) and muscle glycogen (Figure 7b) during approximately 2-hours of cycling performed before and at the end of 28 days of dietary supplementation (3 g/day creatine; n = 6 or placebo;

n = 6) in young trained cyclists. Data are presented as mean ± SEM. Muscle fiber composition Fiber type percentage in the creatine group was 46.8 ± 3.6, 42.7 ± 2.4, and 10.5 ± 2.5% for type I, type IIa, and type IIb fibers, respectively. Fiber type percentage in the placebo group was not different from that of the creatine group, with fiber type percentages of 42.5 ± 2.3, 48.7 ± 3.8, and 8.5 ± 3.0% for type I, type IIa, and type IIb fibers, respectively. Type I fiber percentage was correlated with muscle total creatine (r = 0.62, P < 0.05) and muscle creatine phosphate (r = 0.65, P < 0.05). Fiber type percentage was not significantly correlated with sprint performance time, nor with the Dibutyryl-cAMP mouse change in muscle creatine concentration from pre- to post-supplementation. Side effects Regarding side effects (data not shown), two of the 12 subjects reported experiencing muscle cramps at rest following supplementation. There were no reports of muscle

cramping prior to supplementation. Both of the subjects who reported muscle cramping following supplementation were in the creatine group. There were no other reports of side effects (chest pain, fatigue, upper-respiratory and auditory problems, autoimmune reactions, gastrointestinal Obeticholic in vivo difficulties, syncope, joint discomfort, appetite, headache, memory, stress and mood changes) that were unique Urease to the creatine supplementation. Discussion The present study is unique in that it is the first double-blind study to monitor the effect of prolonged creatine supplementation at the level of the whole body, vascular compartment, and skeletal muscle. The performance data presented indicate that total time of a sprint to exhaustion at a constant power output following two hours of variable-intensity cycling is not influenced by 28 days of low-dose dietary creatine monohydrate supplementation. Sprint time, and therefore total power output, in the creatine group was not improved to a greater extent than that seen in the placebo group. Engelhardt et al.