[Ultrastructural changes in the skeletal muscles during local endurance training (a morphometric study)].

Biopsies of m. triceps surae were studied in physically active students-volunteers. Flexion of the foot sole 40 minutes in duration with 30% maximum voluntary strength was performed during 8 weeks 3-4 times a week. The frequency of the moves made 60 times per minute. In the course of morphometrical study greater attention was paid on mitochondrial parameters. Mitochondrial volume density did not change, while their number as well as the volume density of lipid inclusions tend to increase. Mitochondrial number, area and volume density of inclusions in the central zone of m. triceps surae were compared (before training: number per 100 microns2--2+3; area--0,13 +/- 0,010 microns2, volume density--2.7 +/- 0.3%, after training: number--48 +/- 4, area--0,110 +/- 0,01 microns2, volume density--2,7 +/- 0,3%) with the data available in literature on another muscles of elite sportsmen. It was concluded that high mitochondrial volume density in muscles of endurance trained sportsmen may result either from mitochondrial hypertrophy or increase of their number or from either of these factors, which is likely to be the concrete reflection of specificity of the sport efficiency.