Muscle injuries and lactate overload during training or at the end of the season, in top team sports, quickly preclude optimal results and participation. Is total magnesium deficiency responsible for these problems in elite athletes and whether magnesium supplementation improves their muscle metabolism or lactate-pyruvate-metabolism? Methods: In 55 elite athletes [male: 25 – female: 30 / soccer: 26 – Olympics: 14 – tennis: 15 – motorsports (DTM-Formula1): whole blood magnesium were determined. In 25 athletes serum and whole blood magnesium, creatine kinase (CK), venous pyruvate and lactate, and the mitochondrial energy level ATP were determined before and after 3 months of daily supplementation with 370mg magnesium and statistically correlated. A Spearman-ranking coefficient of correlation, a chi-quadrat-test by Pearson, and an independent t-test were used with p<0.05 this value is reliable, p<0.01 highly significant. Results: In 27. 1% of all elite athletes (N=18/55) a whole blood magnesium deficiency (vMg<1.29 mmol/l) was proved. Female athletes were significantly worst supplied than the male athletes [vMg: 1.33 ± 0.11 mmol/l vs. 1.41 ± 0.13 mmol/l (p<0.024].Whole blood magnesium (1.31 ± 0.15 mmol/l before vs 1.45 ± 0.09 mmol/l after therapy, p<0.00025), serum magnesium (0.78 ± 0.06 mmol/l before vs 0.93 ± 0.05 mmol/l after therapy, p<0.00025), the venous pyruvate (0.21 ± 0.12 mg/dl before vs 0.39 ± 0.10 mg/dl after therapy, p<0.00025) and mitochondrial ATP (90.56 ± 10.11 %T cells before vs 99.07 ± 1.21 %T cells after therapy, p<0.00025) significantly increased after 3 months supplementation of 370mg magnesiumoxide. Venouslactate (10.62 ± 3.50 mg/dl vs. 8.08 ± 2.09 mg/dl after therapy, p<0.0025), the pyruvate lactate ratio (69.98 ± 52.81 vs. 22.93 ± 12.29 after therapy, p<0.00025) and the creatine kinase CK (501 ± 323 U/l before vs. 294 ± 161 U/l after therapy, p=0.018) significantly reduced under 3-months old daily magnesium substitution. For each 0.1 mmol/l increase in whole blood magnesium, the pyruvate improves significantly by 0,06 mg/dl and the pyruvate lactate ratio decreases significantly by 90.9. The improvement of the pyruvate as well as the pyruvate lactate ratio leads to a significant improvement in muscularity metabolism (CK) [increase by 0.1 mg/dl pyruvate decreases CK by 89.39, p=0.018, reduction of lactate pyruvate ratio decreases CK by 25.45, p=0.008). An absolute risk reduction of 68% (18/25 before vs 1/25 after therapy) could be calculated for muscular injuries. No side influences were reported. Conclusion: The determination of serum magnesium in elite sports is not meaningful. Whole blood magnesium (vMg), on the other hand, plays a significant role in the prevention of muscularity injuries, independently of the type of sports, by optimizing pyruvate lactate metabolism and thus mitochondrial energy production ATP. Further treatment studies have to prove if optimizing whole blood magnesium can lead to an increase in performance.