Date of Award
2007
Degree Type
Thesis
Degree Name
Doctor of Philosophy
Program
Kinesiology
Supervisor
Dr.Charles Rice
Abstract
Although there has been extensive research into the effects of aging on the neuromuscular system, there are relatively few data on those elderly individuals most at risk for a loss of independence; i.e., >80 years old. Thus, the objective of this thesis was to provide a partial timeline of age-related changes in dorsiflexor form and function by testing healthy men in their 3rd, 7th and 9th decades of life (young, old and very old, respectively). It has been suggested that motor unit (MU) loss is the principal factor in sarcopenia, the age-related loss of muscle mass and strength. Decomposition-enhanced spike-triggered averaging (DE-STA) is a relatively new method for determining a motor unit number estimate (MUNE) in a human muscle. The key finding of the study in Chapter 2 was that the most representative sample of MUs in the tibialis anterior (TA) would be obtained at 25% Of maximum voluntary contraction (MVC) strength. Using the 25% MVC contraction intensity, MUNEs in the TA were 150 in the young, 91 in the old and 59 in the very old (Chapter 3). In spite of the progressive loss of MUs, dorsiflexor strength was maintained in the old and only 30% reduced in the very old. Muscle power encompasses both muscle strength and contractile velocity yet static strength is the most commonly studied functional measure with aging. Similarly, the assessment of power derived from isotonic (constant load) efforts would yield the data most applicable to activities of daily living in the elderly; however, this is the least investigated contraction mode. The key findings of the study in Chapter 4 were that power loss was nearly double strength loss in the very old and that these deficits were due πi to changes intrinsic to the muscle fibres and not a loss of muscle mass. Perhaps more important than the implications of such a large power deficit in a non-fatigued state, was the finding that very old men were more susceptible to fatigue during a bout of repeated low-load isotonic contractions.
Recommended Citation
McNeil, Chris J., "DORSIFLEXOR FORM AND FUNCTION IN YOUNG, OLD AND VERY OLD MEN" (2007). Digitized Theses. 5073.
https://ir.lib.uwo.ca/digitizedtheses/5073
