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dmcfarlane
05-28-2007, 12:06 PM
Greetings!

We used to think that sarcopenia was irreversible; the traditional view
of muscle aging was that a decline in physical strength due to began
after the age of 39 in males and after the age of 49 in females (Adams
et al, 2006) and continued to get steadily worse during the rest of a
person's life. [Sarcopenia, the loss of skeletal muscle mass with
advancing age, causes physical weakness and reduced activity levels that
lead to fatness and hypertension.]

However, it has been known since the nineties that progressive
resistance exercises can increase muscle strength, reduce body fat and
decrease blood pressure (Evans, 1996). Subsequent research has shown
that enormous improvements in fitness are possible; Meredith et al found
that for 10 "elderly subjects" (65.1 +/- 2.9 yr) endurance training at
70% of peak oxygen consumption for 12 weeks produced a 128% increase in
muscle oxidative capacity (1989).

It is now widely accepted that frail elderly people respond robustly to
resistance training and that significant increases in muscle area are
possible with resistance training in combination with adequate energy
intakes (Singh et al, 1999). This is thought to be due to adaptive
responses of skeletal muscle to mechanical load that are mediated by
myogenic regulatory factors (Bamman et al, 2004).

More recently the spotlight has fallen on the role of nutrition and
hormone replacement in reversing sarcopenia have received attention
(Yarasheski, 2003); the factors that contribute to its development
include the neuropathic, metabolic, hormonal, nutritional and
immunological status of those affected (Narici et al, 2004).

Almost all of the attention seems to be paid to the institutionalised
elderly; I cannot find many papers that comment on the value of
resistance training for middle aged people (i.e. those who are aged
between 40 and 60) who are still in the workforce. This is rather odd
considering all the current publicity about retaining older workers
(especially "baby boomers") in the workforce (not to mention all the
current publicity about improving fitness and reducing obesity in the
population in general!)

Does anyone have any comments (or references) on the benefits of
endurance training for these workers in programs designed to maintain
their fitness (or rehab programs)?

Regards,
David McFarlane MAppSc (Ergonomics)
Ergonomist, WorkCover NSW

References

1. M. Adams, N. Bogduk, K. Burton and P. Dolan, (2006), "The
Biomechanics of Back Pain", second edition, (Churchill, Livingstone,
Elsevier; New York), fig 8.5, p 99.

2. W Evans, (1996), "Reversing sarcopenia: how weight training can build
strength and vitality", Geriatrics, May 1996; 51(5): 46-7, 51-3.

3. C Meredith, W Frontera, E Fisher, V Hughes, J Herland, J Edwards and
W Evans, (1989), "Peripheral effects of endurance training in young and
old subjects", Journal of Applied Physiology, Vol 66, Issue 6, pp
2844-2849.

4. M Singh, W Ding, T Manfredi, G Solares, E O'Neill, K Clements, N
Ryan, J Kehayias, R Fielding and W Evans, (1999), " Insulin-like growth
factor I in skeletal muscle after weight-lifting exercise in frail
elders", Am J Physiol Endocrinol Metab 277, 1, July (1 Pt 1): E135-43.

5. M Bamman, R Ragan, J Kim, J Cross, V Hill, S Tuggle and R Allman,
(2004), " Myogenic protein expression before and after resistance
loading in 26- and 64-yr-old men and women", J Appl Physiol 97:
1329-1337.

6. K Yarasheski, (2003), " Exercise, aging, and muscle protein
metabolism", J Gerontol A Biol Sci Med Sci, 2003 Oct; 58 (10): M918-22.

7. M Narici, N Reeves, C Morse and C Maganaris, (2004), "Muscular
adaptations to resistance exercise in the elderly", Journal of
Musculoskeletal Neuronal Interaction, 4 (2), 161-164.

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