Abstract. Seventeen male officer trainees (between 20 and 24 years of age) of the Theresan Military Academy in Wiener Neustadt (Austria) have been subjected to a standardized 2,400-m run as a fitness test. Before and after the run, capillary blood samples for determination of pH, pCO 2 , pO 2 , HCO 3, base excess (BE), ionized Mg, and lactate were drawn, and heart rate (HR) and RRsys were determined. On the next day, the subjects received two sachets of an effervescent compound (“Dr. Böhm Mg plus Aminosäuren”, Apomedica, Graz, Austria) in 125 mL of tap water, containing electrolytes (Mg 150 mg, K 180 mg), trace elements (Zn 5 mg, Se 25 µg), vitamins (vitamin C 50 mg, riboflavin 0.26 mg, niacin 8 mg, B6 1.4 mg, B 12 3 µg), amino-acids (leucine 600 mg, isoleucine 300 mg, valin 300 mg, argininaspartate 400 mg, l-carnitine 200 mg, taurine 200 mg), and herbal antioxidants (resveratrol 2 mg, green tea extract 25 mg) after blood sampling, and the same 2,400-m run as before was performed again with another consecutive sampling. It turned out that the drop in BE, pCO 2 , HCO 3 , and Mg due to the run was significantly smaller in the treatment group than in controls (p < 0.05). The increase in lactate and RRsys on the other hand was significantly higher in the control group (p < 0.05). Also, Mg changes due to the run were much less uniform in Mg-treated subjects. Linear correlations, which developed significantly between ionized Mg, pO 2 , pCO 2 , BE, and lactate, as well as significant linear correlations between heart rate and lactate, and also between Mg and running time (our performance marker), were in fact always seen in untreated subjects but never in Mg-treated participants. We deduce that acute Mg and amino acid application before sport enhances Mg availability for muscle-energy turnover, and at the same time, (enzyme) protein synthesis is enhanced. This creates an at least (vitamins and antioxidants are also applied) two-pronged useful effect on effort and performance.