Newton, David; (1993) Normalised muscle force and relaxation rates in subnourished and aged human subjects. Masters thesis (M.Phil), UCL (University College London).

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Abstract

Is the muscle weakness associated with ageing and subnutrition simply due to muscle atrophy. Can the weakness be reversed by training. Maximal voluntary force (MVF) measurements of adductor pollicis (AP) muscle were made during maximum voluntary contractions (MVC's) and normalised for anatomical cross-sectional area (CSA) in three subject groups: normally-nourished young; normally-nourished elderly; and subnourished young patients. In the subnourished patients MVF was significantly less, relative to their heights, than in the young control group but normalised force (MVF/CSA) was unchanged. Normal maximum relaxation rates (MRR) were significantly slower in the patients than in the controls. The elderly also showed significantly reduced MVF relative to their heights and in addition the mean ratio of MVF/CSA for the elderly was significantly less than that for the young nourished. MRR was no different in the two groups. A comparison was made of AP muscle CSA's measured directly (by means of CAT and n.m.r scans) with muscle CSA's measured by the method used in the present, reported studies. There was a good correlation between CSA's obtained by CAT/n.m.r. and the method used in the present studies, indicating that the present method gives a good estimate of AP muscle CSA. An evaluation was made of the effectiveness of an adductor pollicis strength training regime for future use in investigating the effects of strength training on aged muscle. No training effect was found. The experience gained prompted the development of an improved force measuring apparatus. An investigation was made into the force and cross- sectional area characteristics of the AP in a group of experienced fencers. This was intended as a means of evaluating the use of the newly-developed force- measuring apparatus, and as a preliminary to an intended training study of AP in the elderly. The new force- measuring apparatus gave a better correlation with measured AP muscle CSA's than did the old-style force transducer. No training effect was found in the AP of the fencers' fencing hand. Using the new, improved force measuring apparatus, a group of normally-nourished elderly and a group of normally-nourished young were tested for maximality of their muscle recruitment by means of twitch superimposition. There was a strong indication that both groups were able to maximally activate their adductor pollicis muscle during maximum voluntary contraction. It appears that in the young subnourished at least, the weakness associated with subnourishment is due largely to atrophy. It is evident that the muscle weakness associated with age is not due simply to muscle atrophy. There is in the elderly an inherent decline in the force- producing capability of AP muscle.

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