Age-associated decline in BM and FFM

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<<<Once we reach our 50s, a steep decline in functional strength

seems to be underway. In many ways, this process resembles advanced

detraining. Movement speed, rate of force development, and

especially power diminish even faster than maximum strength. Fast-

twitch muscle fibers disappear more rapidly than slow-twitch,

decreasing in size as well as number, and being replaced by

fatty/fibrous tissue. This is due partly to inactivity and partly to

general deterioration of the nervous system.>>>

***Members may find the following excerpts to be of interest:

" " The age-associated decline in BM and FFM in the men identification in this

study was also reported by Toth et al, (1994) and Davies et al. (1995). Possible

mechanisms are age-related changes in the anabolic hormones testosterone and

human growth hormone, which influence the amount and make up of active tissue

(Rudman et al. 1990, 1991). Human growth hormone secretion declines after the

age of 40, especially in men (Lsaksson et al. 1985). Testosterone levels in the

men also decline wilh advancing age (Gray et al. 1991; Proctor et al. 1998) and

this decline has been shown to be mirrored by a loss of LBM and muscular

strength (Larsson & Karlsson 1978; Balagopal et al. 1997).

Older women do not experience such a rapid change in anabolic

steroids and growth hormones with increasing age (Isaksson et al.

1985), and thus they would tend not to experience such a decline in

BM and FFM…… Any small remaining difference between men and women

could be due lo factors related to cellular aerobic capacity and

perhaps reflects cultural differences such as levels of habitual

exercise, a factor not accounted for in the present analysis. " "

Taken from:

Modelling the influence of fat-free mass and physical activity on the

decline in maximal oxygen uptake with age in older humans.

Exp Physiol. 2000 Nov;85(6):877-86.

Amara CE, Koval JJ, PJ, Paterson DH, Winter EM, Cunningham DA.

The purpose of this study was to use an allometric model (maximal

oxygen uptake (VO2,max) = FFMbeta1 x PAbeta2 x exp(beta0 + beta3 age

+ beta4 sex) x epsilon) to determine the influence of fat-free mass

(FFM), physical activity (PA), sex and age on VO2,max in older men (n

= 152) and women (n = 146) aged 55-86 years. VO2,max was measured

during a fatigue-limited treadmill test, FFM was determined from

skinfold thickness and physical activity by the Minnesota Leisure

Time Physical Activity questionnaire.

The model was linearised by taking the natural logarithm of VO2,max,

FFM and physical activity. Variables were selected using multiple

linear regression (P < 0.05). The sex variable was not significant (P

= 0.062). The model explained 72.1% of the variance in VO2,max.

Significant individual coefficients were incorporated into the model

yielding the following expression: VO2,max = FFM0.971 x PA0.026 x exp

(-2.48-0.015age).

Therefore, FFM and physical activity were significant factors

contributing to the changes in VO2,max with age. In addition,

controlling for FFM and physical activity abolished sex differences

in VO2,max. The rate of decline in VO2,max (after accounting for FFM

and physical activity) with age, was approximately 15% per decade.

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Carruthers

Wakefield, UK