Post by carruthersjam on Nov 16, 2008 10:50:01 GMT -8
Aging causes a shift from type II to type I (fast twitch to slow
twitch). Below are a few presentation notes from Dr Henning
Wackerhage (Molecular Exercise Physiology Atrophy):
The primary problem in ageing sarcopenia appears to be a loss of a-
motor neurones (Tomlinson & Irving, 1977;Kawamura et al., 1977). As a
result, almost half of the muscle fibres are lost from the age of 20
to the age of 80, at least in the vastus lateralis (Lexell et al.
1988).
Ageing sarcopenia is a very slow process. Lexell et al.'s (1988) data
suggest that » 12 fibres out of half a million are lost daily from
the age of 20 to the age of 80 years. Similarly, a hypothetical loss
of 10 kg of muscle mass over 40 years equates to a daily muscle loss
of ≈ 0.7 g. Thus, the net muscle changes are very hard to detect.
• Type 2 fibres atrophy and the percentage of type 2 fibres decreases
(Lexell et al. 1988).
• Basal protein synthesis and degradation are probably unchanged
(Dorrens & Rennie, 2003). However, the response to resistance
training and nutrition is likely to be different.
• The slow elimination of fibres and myonuclei is likely due to
apoptosis, at least in rats (Dirks & Leeuwenburgh, 2002;Pollack et
al., 2002).
• Aging causes cell death and functional changes in the
neuroendocrine system (Rehman & Masson, 2001) and this affects the
growth environment of the muscle.
• The pulse amplitude of growth hormone secretion (Finkelstein et
al., 1972) and systemic IGF-1 concentrations decrease with aging
(Copeland et al., 1990).
• In addition, old age is often associated with a low-grade
inflammation as demonstrated by higher levels of cytokines such as
TNFa and IL-6 (Bruunsgaard et al., 2001) and an "inflammation theory
of aging" has been proposed (Chung et al., 2001).
* Ageing sarcopenia leads to a change in body composition. The
relative contribution of fat and non-muscle fat free muscle increases
whereas the contribution of muscle decreases (Balagopal et al. 1997).
• Serum myostatin is higher in older men and women than in young
(Yarasheski et al., 2002), although there is a high variation.
*Many other changes could contribute to the net loss of muscle mass:
decreased growth hormone, IGF-1, increased myostatin and pro-
inflammatory cytokines.
twitch). Below are a few presentation notes from Dr Henning
Wackerhage (Molecular Exercise Physiology Atrophy):
The primary problem in ageing sarcopenia appears to be a loss of a-
motor neurones (Tomlinson & Irving, 1977;Kawamura et al., 1977). As a
result, almost half of the muscle fibres are lost from the age of 20
to the age of 80, at least in the vastus lateralis (Lexell et al.
1988).
Ageing sarcopenia is a very slow process. Lexell et al.'s (1988) data
suggest that » 12 fibres out of half a million are lost daily from
the age of 20 to the age of 80 years. Similarly, a hypothetical loss
of 10 kg of muscle mass over 40 years equates to a daily muscle loss
of ≈ 0.7 g. Thus, the net muscle changes are very hard to detect.
• Type 2 fibres atrophy and the percentage of type 2 fibres decreases
(Lexell et al. 1988).
• Basal protein synthesis and degradation are probably unchanged
(Dorrens & Rennie, 2003). However, the response to resistance
training and nutrition is likely to be different.
• The slow elimination of fibres and myonuclei is likely due to
apoptosis, at least in rats (Dirks & Leeuwenburgh, 2002;Pollack et
al., 2002).
• Aging causes cell death and functional changes in the
neuroendocrine system (Rehman & Masson, 2001) and this affects the
growth environment of the muscle.
• The pulse amplitude of growth hormone secretion (Finkelstein et
al., 1972) and systemic IGF-1 concentrations decrease with aging
(Copeland et al., 1990).
• In addition, old age is often associated with a low-grade
inflammation as demonstrated by higher levels of cytokines such as
TNFa and IL-6 (Bruunsgaard et al., 2001) and an "inflammation theory
of aging" has been proposed (Chung et al., 2001).
* Ageing sarcopenia leads to a change in body composition. The
relative contribution of fat and non-muscle fat free muscle increases
whereas the contribution of muscle decreases (Balagopal et al. 1997).
• Serum myostatin is higher in older men and women than in young
(Yarasheski et al., 2002), although there is a high variation.
*Many other changes could contribute to the net loss of muscle mass:
decreased growth hormone, IGF-1, increased myostatin and pro-
inflammatory cytokines.