Abstract
The histological and ultrastructural features of 21 males and 8 females were monitored
during an 18- to 20-month training period, during which the training distance was
gradually increased. The training period was divided into three periods of 6, 5, and
7 months, respectively. The first, second, and third periods were concluded with a
15-, 25-, 42-km road race, respectively. The competitive distance always exceeded
the maximal distance covered in any previous training session. Percutaneous biopsies
were taken from the vastus lateralis muscle 5 days before each contest as well as
0.5-6 h post-contest and 8-9 days post-contest. No shift in fiber type was observed
during the training period from the 15-km contest until the 42-km contest nor were
any changes in fiber diameter observed. Histological examination demonstrated a gradual
increase in degenerative changes during the training period, which occurred in type
I as well as in type II fibers. Ultrastructural examination revealed irregular Z-lines
and hypercontraction immediately after exercise. No damage to the sarcolemma was detected.
The number of degenerative changes after each contest was not higher than before each
race. It is concluded that long-distance running is associated with transient minor
pathological changes in skeletal muscle, which are related to the total distance covered
per week rather than the intensity of the exercise.
Key words
muscle - marathon - pathological changes - fiber types
