Creatine is an effective, inexpensive, and safe dietary supplement, which has been largely used in sports and clinical populations. However, creatine is much less studied in female athletes, with long-term data being particularly scant. This study aims to expand our knowledge on the effects of creatine supplementation in young (Under-20) and elite female football players. This study will comprise two experiments. The first one will be a randomized, controlled trial in which young athletes will be assigned into either creatine or placebo (n = 20). Before and 7 days after supplementation or placebo (4 x 5 g/d of Creapure or dextrose at same dose), athletes will perform a battery of performance tests. Blood and urinary biochemical parameters for assessing the safety of supplementation will be analyzed (creatinine, albuminuria, urea, sodium, potassium, liver enzymes, creatine kinase, hematology). Food intake will be assessed by means of 3-d 24-h dietary recalls. The second experiment will have a quasi-experimental design (i.e., pre-to-post), in which both young and elite football players (n = 70) will be supplemented with creatine (4 x 5 g/d for 7 days and then 5 days during the follow-up) and will be assessed for safety using the above-mentioned markers during the regular football season (~12 months). Assessments will be carried out at baseline, in the mid-season and after the season.

Inclusion Criteria:

• female football players

Exclusion Criteria:

• age under 18

Data will be made available upon reasonable request.