THE EFFECT OF CREATINE PHOSPHATE LOADING ON ANAEROBIC WORKING CAPACITY IN WOMEN

Abstract

To our knowledge, no studies have examined the combined effect of creatine (Cr) plus phosphate supplementation on anaerobic working capacity (AWC) in women. PURPOSE: To determine the effects of 2 d and 6 d of creatine phosphate (CrP) loading on AWC in women. METHODS: Thirty physically active women (age range = 18 - 35 yr) were randomly assigned to one of three treatment groups using a double blind design: (1) 18 g of dextrose as placebo (PL); (2) 5 g of Cr plus 2 g of sodium phosphate and 2 g of potassium phosphate with 18 g of dextrose (CrP); or (3) 5 g of Cr plus 18 g dextrose. All of the treatments were administered as a flavored powder blend and were packaged to be identical in taste and appearance. The treatments were dissolved in 16 oz. water and ingested 4 times per day for 6 consecutive days. The subjects completed 4 d of testing on an electronically braked cycle ergometer: (a) familiarization - 1 learning trial to establish power outputs (PO) for subsequent testing; (b) pre-testing - 2 bouts performed at PO selected to elicit fatigue in 1 - 10 min; (c) post-testing - 2 bouts performed at the same PO following 2 and 6 d of supplementation. The data were analyzed using a 3 x 3 (group x time) ANOVA. When appropriate, Tukey post-hoc tests were used to make pairwise comparisons. RESULTS: The results indicated that there were no significant (p > 0.05) effects by time or by group. When examining the changes in AWC for each group from baseline to 6 d, the Cr and CrP groups experienced a 13.0% (ES = 0.68) and 10.8% (ES = 0.55) increase in AWC, respectively, whereas the PL group demonstrated a 1.1% decrease (ES = 0.06). CONCLUSIONS: These findings suggest that neither Cr or CrP supplementation was effective for increasing AWC when compared to PL. Although the changes in AWC were not statistically significant, it is worthy to note (from a performance standpoint) that the Cr and CrP groups experienced a 13.0% and 10.8% increase in AWC, respectively, while the PL group demonstrated a 1.1% decline. The increase in AWC for the Cr group was consistent with previous studies using female subjects that reported increases ranging from 14.8% to 22.1% following 5 - 6 d of loading. Supported by Nutricia USA