Enzymatic and hormonal responses following a 24 h endurance run and a 10 h triathlon race

Summary

Muscle cell leakage and hormonal changes were compared immediately after and during the 3 days following a 24 h endurance run (R_{24 h}) in 8 subjects, and a 10 h triathlon non-competitive race (T_{10 h}) in 6 subjects. The study showed three main differences: 1) plasma enzyme increases were considerably more significant in R_{24 h} than in T_{10 h}: compared with resting levels, creatine kinase increased ×120 after R_{24 h} but only ×2 after T_{10 h}; lactic dehydrogenase ×4, as opposed to ×1.5; and transaminases only showed an increase after R_{24 h}. The plasma myoglobin increase after R_{24 h} was double that found after T_{10 h}; 2) for the same magnitude of plasma aldosterone and cortisol after R_{24 h} and T_{10 h} (3 times the resting levels), a highly significant decrease in urinary Na⁺ (p<0.001) and an increase in urinary K⁺ (p<0.01) were found only after R_{24 h}; and 3) the plasma free noradrenaline level increased significantly after R_{24 h} (×2.6) whereas it was unchanged after T_{10 h}. In contrast, the plasma level of conjugated dopamine increased only after T_{10 h} (×3.7, p<0.05). These results suggest that long-distance running causes more muscular lesions than the triathlon, and that important factors other than aldosterone are probably involved in the regulation of urinary electrolyte excretions during T_{10 h}.