• Intermyofibrillar fat;
  • lipoprotein-lipase activity;
  • muscle fibre types;
  • prolonged exercise.

Lipoprotein-lipase (LPL) activity and intracellularly stored triglycerides were determined in muscle biopsies taken before and after an 85 km skiing race from 7 volunteers. The triglyceride stores were larger in slow twitch than in fast twitch fibres (proportions 5: 1 before the race). The LPL activity increased and the triglyceride stores in slow twitch fibres decreased during the race. The best trained subjects had the largest TG stores before the race and their TG stores also decreased most during the race. These subjects also had very small increases of LPL activity. The least trained subject on the other hand showed a 6-fold increase of LPL activity. The high post-race LPL activity in less trained subjects indicates a higher capacity for uptake of fatty acids from serum TG as compared to the more trained subjects.