CHANGES IN PHOSPHORUS-COMPOUNDS AND WATER-CONTENT IN SKELETAL-MUSCLE DUE TO ECCENTRIC EXERCISE

The interrelationship of the time courses of soreness and oedema, and of force and phosphorus metabolites after eccentric exercise was studi ed. Eight male subjects performed 120 maximal eccentric contractions w ith their left forearm flexors. Soreness, maximal force, flexion and e xtension elbow angle, and creatine kinase and myoglobin efflux were fo llowed for 96 h after exercise. For equal periods T1 and T2 relaxation times and muscle cross-sectional area were calculated from magnetic r esonance images as indications of oedema, and inorganic phosphate (P(i )) and phosphocreatine (PCr) were measured with magnetic resonance spe ctroscopy. Soreness on extension increased at 1 h (P = 0.043), T1 and T2 (both P = 0.01) and soreness when the arm was pressed (P = 0.028) a t 24 h, and muscle cross-sectional area increased at 48 h (P = 0.01) a fter exercise. Soreness on extension reached a maximum at 48 h, the ot her four parameters at 72 h. All parameters related to oedema, and sor eness, showed an increasing pattern for the period after exercise as a whole, but the largest increase between two points of measurement occ urred earlier for soreness than for oedema. Creatine kinase increased significantly from baseline from 24 h onwards (P = 0.017) and myoglobi n from 1 h onwards (P = 0.012). The P(i):PCr ratio differed from basel ine for the first time 24 b after exercise (P = 0.018), increased to 2 25%, and then remained on a plateau until 72 h. Maximal isotonic force decreased to 53% at 1 h (P = 0.012), and recovered from then on. It w as concluded firstly that the largest increase in soreness precedes th at of oedema, and secondly that the decrease in force after eccentric exercise is not related to an altered metabolic state. The combined im aging and spectroscopy results gave the impression that changes in pho sphorus metabolites were homogeneously distributed over the flexor mus cles whereas oedema was not.