The effects of aging on the muscle length (as inferred by
joint angle)-tension relationship was studied in the ankle
dorsiflexors of male and female subjects aged 20-40 years
(x=25.3; 15d, 159) and 60-80 years (x=68.8; 15d, 159) at 10
joint angles {15°0 through 30°P, in 5° increments). Isometric
twitches, voluntary contractions, and 1-sec evoked tetanic
contractions {20, 50 & 80 Hz) were measured in the R-tibialis
anterior muscle. The resting joint angle for the ankle
dorsi flexors was similar between elderly and young adults
{13°P ± 3.44). On average, evoked and voluntary torque output
increased upon muscle lengthening beyond resting length, and
decreased upon shortening. Evoked single twitches of the TA
revealed that peak total torque occurred at the extreme of
plantarflexion (30°P} in both elderly and young adults. Most
importantly, elderly individuals produced similar twitch
torque values at all joint angles compared to young adults.
Maximal voluntary torque was stronger at the more
plantarflexed compared to the dorsiflexed angles, for all
subjects, regardless of age, with maximum torque plateauing at
15°P. Elderly subjects demonstrated much reduced MVC torque
values compared to young adults at all joint angles (ave.= 18%
reduction, p<O.Ol) while maintaining no less than 96% motorunit activation (MUA) . Stimulation of the dorsiflexors at 20,
50, & 80 Hz revealed that the 1-sec peak tetanic torques
declined from a maximum at 30°P through to 15°0 for all
subjects. Elderly adults produced significantly less tetanic
torque at all joint angles compared to young adults (p<0.05).
There was no difference between the elderly and young adults
in the rate at which the rise in tetanic torque was developed
at all joint angles, but elderly adults displayed a
significantly greater twitch/tetanus ratio as compared to
young adults (p<0.005).
In conclusion, these results suggest that there is no
age-associated change in the elastic properties of the ankle
dorsiflexors, and thus, the length-tension relationship of
this muscle group is similar between elderly and young adults. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22605 |
| Date | 08 1900 |
| Creators | Van Schaik, Charmaine S. |
| Contributors | Human Biodynamics |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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