Metabolic changes during volleyball matches.
Urinary and/or serum concentrations of electrolytes (sodium, potassium, calcium, magnesium), hormones (aldosterone, cortisol, catecholamines), and metabolic parameters (lactate, glucose, free fatty acids) were determined during different volleyball matches. While [Na+]s was slightly increased-not exceeding the hemo-concentration effect-[K+]s, and [Ca2+]s were diminished after the matches. Due to a lowered glomerular filtration rate (GFR), urinary excretion of water, sodium, and potassium was decreased. In addition, the tubular resorption and secretion of fluid and electrolytes was influenced by different hormones leading to a lowered [Na+]u and an increase of [K+]u after exercise. Low concentrations of lactate (2.54 +/- 1.21 mmol/l) during and after the matches and an increase of [FFA]s indicate that energy during the short exercise periods (9 s) is mainly supplied by a breakdown of creatine phosphate, while aerobic pathways restore the energy sources during the resting periods (12 s). Serum concentrations of aldosterone and cortisol as well as the excretion of adrenaline are enhanced on the same scale as after endurance sports. The excretion of noradrenaline corresponds to values during exercise of high intensity.