Abstract
This study aimed to investigate the effects of short-duration creatine monohydrate supplementation on anaerobic capacity (AC), anaerobic energy pathways, and time-to-exhaustion during high-intensity running. Fourteen healthy men underwent a graded exercise test (GXT) followed by a O2max confirmation test, 5 submaximal efforts, and 4 supramaximal running bouts at 115% of O2max intensity (the first two supramaximal sessions were applied as familiarization trials) to measure the AC using two procedures; the maximum accumulated oxygen deficit (MAOD) and non-oxidative pathways energetics sum (AC[La-]+EPOCfast). The investigation was conducted in a single-blind and placebo-controlled manner, with participants performing the efforts first after being supplemented with a placebo (dextrose 20 g⋅day-1 for 5 days), and then, after a 7 day “placebo” washout period, they started the same procedure under creatine supplementation (20 g⋅day-1 for 5 days. This order was chosen due to the prolonged washout of creatine. MAOD was not different between placebo (3.35 ± 0.65 L) and creatine conditions (3.39 ± 0.79 L; P = 0.58) and presented a negligible effect [effect size (ES) = 0.08], similar to, AC[La-]+EPOCfast (placebo condition (3.66 ± 0.79 Land under creatine ingestion 3.82 ± 0.85 L; P = 0.07) presenting a small effect (ES = 0.20). The energetics from the phosphagen pathway increased significantly after creatine supplementation (1.66 ± 0.40 L) compared to the placebo condition (1.55 ± 0.42 L; P = 0.03). However, the glycolytic and oxidative pathways were not different between conditions. Furthermore, time to exhaustion did not differ between placebo (160.79 ± 37.76 s) and creatine conditions (163.64 ± 38.72; P = 0.49). Therefore, we can conclude that creatine supplementation improves the phosphagen energy contribution, but with no statistical effect on AC or time to exhaustion in supramaximal running.
Highlights
Creatine (α-methyl guanidine-acetic acid) is a nitrogen amine which can be obtained in diet and endogenously synthesized by the liver, kidneys, and pancreas (Hall and Trojian, 2013) and it is predominantly stored in skeletal muscle (≈95%) in both its free and phosphorylated forms (Persky and Brazeau, 2001)
Considering the values of iV O2max achieved in the graded exercise test (GXT), the velocity corresponding to 115% applied during the supramaximal tests was 17.1 ± 1.3 (CI95% = 16.3 to 17.9) km·h−1
The ePCr increased significantly in the creatine condition when expressed in absolute values (P = 0.027; ES = 0.26), besides which, 7 participants were responsive to creatine supplementation according to the smallest worthwhile change analysis
Summary
Creatine (α-methyl guanidine-acetic acid) is a nitrogen amine which can be obtained in diet (e.g., red and fish meat) and endogenously synthesized by the liver, kidneys, and pancreas (Hall and Trojian, 2013) and it is predominantly stored in skeletal muscle (≈95%) in both its free and phosphorylated forms (i.e., phosphorylcreatine) (Persky and Brazeau, 2001). Since creatine supplementation can significantly increase phosphorylcreatine intramuscular stores, it has been shown to improve the energy supply from the phosphagen systems (ePCr) (Yquel et al, 2002; Bemben and Lamont, 2005), thereby increasing the maximum capacity to resynthesize adenosine triphosphate (ATP) by non-oxidative pathways [i.e., anaerobic capacity (AC)] during high-intensity exercise. These changes could lead to improved performance in this type of exercise (Doherty et al, 2000)
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