Effect Of Creatine Monohydrate Supplementation On VO2 Kinetics In Aerobically Fit Adults

Creatine monohydrate (CrM) is a popular dietary supplement consumed by individuals engaging in both strength training and endurance training. Though CrM supplementation has been shown to increase the second lactate threshold, effects on the aerobic threshold are unknown. PURPOSE: to determine the effect of CrM supplementation on 1) oxygen deficit (O2def) at the onset of aerobic exercise, and 2) the first lactate threshold (LT1) later in graded exercise. METHODS: Analysis included 9 aerobically fit adults (5 males, 4 females, 25 ± 6 y, 77 ± 20 kg, 1.8 ± 0.1 m). Following eligibility confirmation by achieving at least 50th percentile of VO2max for sex and age via indirect calorimetry, participants consumed 0.3 g CrM•kg-1 body mass (BM)•d-1 plus 0.6 g maltodextrin•kg-1 BM•d-1 (CrM-MAL) or just 0.6 g maltodextrin•kg-1 BM•d-1 (MAL) for 7 d. Following a 14-d washout in a crossover design, participants consumed the other supplement for 7-d. After each supplementation period, participants were assessed for oxygen consumption at LT1 (VO2LT1) during graded treadmill exercise and area under the curve (AUC) of VO2 at the onset of steady-state treadmill walking. LT1 was determined by the first rise in blood lactate concentration ([bLa]), determined from finger venipuncture and subsequent electrochemical lactate oxidase analysis. Paired t-tests were used to compare means. Effect size was reported as Cohen’s d. Error rate was p ≤ 0.05. RESULTS: VO2LT1 (% of VO2max) was not significantly different between CrM-MAL and MAL (67.9 ± 12.3% vs. 69.1 ± 10.7% respectively; p = 0.799). O2def AUC (mL/kg) at the onset of steady-state treadmill walking did not differ significantly between CrM-MAL and MAL (76.8 ± 8.6 vs. 91.9 ± 15.1 respectively; p = 0.142; ES = 1.229). CONCLUSION: CrM supplementation does not significantly impact oxygen consumption at LT1. However, CrM supplementation may impact VO2 kinetics at the onset of steady-state aerobic exercise, increasing the O2 deficit.