The effect of immobilization on myocellular characteristics in healthy, young males

Aging is characterized by a decrease in skeletal muscle mass and strength, also
known as sarcopenia. This age-related reduction in muscle mass and strength is
associated with a decline in muscle function and performance. On a myocellular
level, sarcopenia is characterized by a reduction in muscle fiber number and
size, with specific type II muscle fiber atrophy. The age-related reduction in
type II muscle fiber size is accompanied by a type II muscle fiber specific
decline in satellite cell (muscle stem cell) content. In adult muscle,
satellite cells are essential for myofiber growth, repair and regeneration.
Thus, the reduction in satellite cell content with age could play an important
role in the development of sarcopenia. In addition, apart from the essential
role that SC play in the maintenance of skeletal muscle mass, day to day
regulation of muscle mass is governed by an intricate balance between muscle
protein synthesis and muscle protein breakdown . Of these, muscle protein
synthesis has been shown to be the most susceptible to change. While basal
muscle protein synthesis does not seem to change with age, it is now becoming
apparent that the normal stimulation of muscle protein synthesis in response to
feeding may become impaired with age. Thus, muscle loss with aging is likely to
be a combination of the decline in SC number and/or the reduced stimulation of
muscle protein synthesis to food.
In the present study we will investigate the effects of physical inactivity,
induced by leg immobilization, on muscle characteristics and satellite cell
content in healthy, young males. The latter can give further insight into the
role of satellite cells in inactivity induced muscle fiber atrophy and/or
sarcopenia.

To study the influence of physical inactivity, induced by leg immobilization,
on muscle charateristics, satellite cell content and muscle protein synthesis
rate.

During this study we will follow participants for a time period of 8 weeks.
Following the first test day one leg will be immobilized by means of a cast,
for a time period of 2 weeks. After 2 weeks of immobilization (on the second
test day), the leg cast will be removed. On this test day we will assess the
effects of the immobilization period. Finally, the third test day will be 6
weeks after cast removal, to assess the effects natural recovery.

The intervention period is 2 weeks. During this period 1 leg will be
immobilized by means of a leg cast.

At the site of the muscle biopsy a hematoma could occur. The muscle biopsy is
performed by an experienced physician. The incision made for obtaining the
muscle biopsy will heal completely. The biopsy scare will be assessed by a
physician before the leg is casted. The immobilization period will lead to loss
of muscle mass and strength in the immobilized leg. However, previous research
has shown that this loss of muscular strength returns to pre-immobilized values
within weeks after removal of the cast, without specific training. The
radiation from the CT-scan is negligible becasue only one image ("single-slice)
is taken and this on 0, 2 and 8 weeks of the intervention