The purpose of this study was to determine the effect of long-term Cr supplementation on blood parameters reflecting liver and kidney function. Twenty-three members of an NCAA Division II American football team (ages = 19–24 years) with at least 2 years of strength training experience were divided into a Cr monohydrate group (CrM, n = 10) in which they voluntarily and spontaneously ingested creatine, and a control group (n = 13) in which they took no supplements. Individuals in the CrM group averaged regular daily consumption of 5 to 20 g (mean ± SD = 13.9 ± 5.8 g) for 0.25 to 5.6 years (2.9 ± 1.8 years). Venous blood analysis for serum albumin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, bilirubin, urea, and creatinine produced no significant differences between groups. Creatinine clearance was estimated from serum creatinine and was not significantly different between groups. Within the CrM group, correlations between all blood parameters and either daily dosage or duration of supplementation were nonsignificant. Therefore, it appears that oral supplementation with CrM has no long-term detrimental effects on kidney or liver functions in highly trained college athletes in the absence of other nutritional supplements.
David L. Mayhew, Jerry L. Mayhew, and John S. Ware
J. L. Mayhew, Chad D. Kerksick, Doug Lentz, John S. Ware, and David L. Mayhew
The purpose of this study was to evaluate the effectiveness of repetitions to fatigue (RTF) for estimating one-repetition maximum (1-RM) bench press performance in male high school athletes. Members of high school athletic teams (N = 213, age = 16.3 ± 1.1 yrs, weight = 79.9 ± 16.7 kg) from four states were tested for 1-RM bench press and RTF after completing 4–6 weeks of resistance training. A new equation for use with male high school athletes was developed from a random sample of 180 participants; it appears to have excellent predictive potential (r = 0.96, SEE = 4.5 kg) and cross-validated well on a subsample (n = 33) from this population (r = 0.98, t = 0.64). Therefore, RTF can be used with acceptable accuracy to estimate maximal strength in the majority of adolescent male athletes who need to handle excessively heavy weights.