Changes in phosphorus compounds and water content in skeletal muscle due to eccentric exercise

Abstract

The interrelationship of the time courses of soreness and oedema, and of force and phosphorus metabolites after eccentric exercise was studied. Eight male subjects performed 120 maximal eccentric contractions with their left forearm flexors. Soreness, maximal force, flexion and extension elbow angle, and creatine kinase and myoglobin efflux were followed for 96 h after exercise. For equal periods T1 and T2 relaxation times and muscle cross-sectional area were calculated from magnetic resonance images as indications of oedema, and inorganic phosphate (P_i) and phosphocreatine (PCr) were measured with magnetic resonance spectroscopy. 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) at 24 h, and muscle cross-sectional area increased at 48 h (P = 0.01) after exercise. Soreness on extension reached a maximum at 48 h, the other four parameters at 72 h. All parameters related to oedema, and soreness, showed an increasing pattern for the period after exercise as a whole, but the largest increase between two points of measurement occurred earlier for soreness than for oedema. Creatine kinase increased significantly from baseline from 24 h onwards (P = 0.017) and myoglobin from 1 h onwards (P = 0.012). The P_i: PCr ratio differed from baseline for the first time 24 h after exercise (P = 0.018), increased to 225%, 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 was concluded firstly that the largest increase in soreness precedes that of oedema, and secondly that the decrease in force after eccentric exercise is not related to an altered metabolic state. The combined imaging and spectroscopy results gave the impression that changes in phosphorus metabolites were homogeneously distributed over the flexor muscles whereas oedema was not.