Dear Kaniaw,

The following publication entitled " The Loss of Skeletal Muscle Strength, Mass, and Quality in Older Adults: The Health, Aging and Body Composition Study" by Bret H. Goodpaster et al. published in J Gerontol A Biol Sci Med Sci (2006) 61 (10): 1059-1064 describes a study conducted on 1880 older adults for three years and the methods used to determine muscle loss or/and decline:

Background. The loss of muscle mass is considered to be a major determinant of strength loss in aging. However, large-scale longitudinal studies examining the association between the loss of mass and strength in older adults are lacking.

Methods. Three-year changes in muscle mass and strength were determined in 1880 older adults in the Health, Aging and Body Composition Study. Knee extensor strength was measured by isokinetic dynamometry. Whole body and appendicular lean and fat mass were assessed by dual-energy x-ray absorptiometry and computed tomography.

Results. Both men and women lost strength, with men losing almost twice as much strength as women. Blacks lost about 28% more strength than did whites. Annualized rates of leg strength decline (3.4% in white men, 4.1% in black men, 2.6% in white women, and 3.0% in black women) were about three times greater than the rates of loss of leg lean mass (∼1% per year). The loss of lean mass, as well as higher baseline strength, lower baseline leg lean mass, and older age, was independently associated with strength decline in both men and women. However, gain of lean mass was not accompanied by strength maintenance or gain (ß coefficients; men, −0.48 ± 4.61, p =.92, women, −1.68 ± 3.57, p =.64).

Conclusions. Although the loss of muscle mass is associated with the decline in strength in older adults, this strength decline is much more rapid than the concomitant loss of muscle mass, suggesting a decline in muscle quality. Moreover, maintaining or gaining muscle mass does not prevent aging-associated declines in muscle strength.

http://biomedgerontology.oxfordjournals.org/content/61/10/1059.abstract

In addition the following link contains a number of studies on mechanisms and countermeasures of muscle mass decline  in aging and neuromuscular disorders:

 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4821223/

Finally, the following is a review article entitled "Human neuromuscular structure and function in old age: A brief review " by Power et al. published in Journal of Sport and Health Science Volume 2, Issue 4, December 2013, Pages 215–226 which focuses on motor unit loss associated with natural adult aging, age-related fatigability, and the age-related differences in strength across contractile muscle actions:

Abstract

Natural adult aging is associated with many functional impairments of the human neuromuscular system. One of the more observable alterations is the loss of contractile muscle mass, termed sarcopenia. The loss of muscle mass occurs primarily due to a progressive loss of viable motor units, and accompanying atrophy of remaining muscle fibers. Not only does the loss of muscle mass contribute to impaired function in old age, but alterations in fiber type and myosin heavy chain isoform expression also contribute to weaker, slower, and less powerful contracting muscles. This review will focus on motor unit loss associated with natural adult aging, age-related fatigability, and the age-related differences in strength across contractile muscle actions.

http://www.sciencedirect.com/science/article/pii/S2095254613000689

Hoping this will be helpful,

Rafik

Dear Kaniaw Rafhat

it is not my domain but I think this is useful for you

Background:

aging process is associated with changes in muscle mass and strength with decline of muscle strength after the 30th life year.

The aim of this study was to investigate these changes in muscle mass and strength.

Patients & Methods:

for this analysis 26 participants were subdivided in two groups. Group 1 comprises participants aged 40 years (n=12).

We assessed anthropometrics, range of motions, leg circumferences and isometric strength values of the knee joints.

Results:

besides comparable anthropometrics, circumferences and strength were higher in group 1 than in group 2. Circumference of upper leg (20 cm above knee articular space) showed for right leg a trend to a significant (median: 54.45 cm (1st quartile: 49.35/3rd quartile: 57.78) vs 49.80 cm (49.50/50.75), p=0.0526) and for left leg a significant 54.30 cm (49.28/58.13) vs 49.50 cm (48.00/52.53), p=0.0356) larger circumference in group 1. Isometric strength was in 60° knee flexion significantly higher in group 1 than in group 2 for right (729.88N (561.47/862.13) vs 456.92N (304.67/560.12), p=0.00448) and left leg (702.49N (581.36/983.87)vs 528.49N (332.95/648.58), p=0.0234).

Conclusions:

aging process leads to distinct muscle mass and strength loss. Muscle strength declines from people aged 40 years between 16.6% and 40.9%.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3940510/

thanks Mr. Rafiq and Mr. Saeed for our answers

Dear Kaniaw, 

I am agree with suggestions of 2 previous experts, and in my opinion, EMG can be helpful. You can find many articles regarding EMG easily.