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Age and contraction type influence motor output variability in rapid discrete tasks
Evangelos A Christou1, Les G Carlton
1University of Illinois at Urbana-Champaign, Champaign, Illinois 61820, USA. echristo@colorado.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 23, 2002
Summary
Older adults exhibit greater variability in controlling knee-extension force across isometric, concentric, and eccentric contractions compared to younger adults. This age-related difference is particularly pronounced during rapid, discrete eccentric contractions of the quadriceps.
Area of Science:
- Biomechanics
- Motor Control
- Aging Research
Background:
- Muscle force control is crucial for daily activities.
- Age-related declines in muscle function are well-documented.
- Understanding force control variability across contraction types is important for assessing neuromuscular function.
Purpose of the Study:
- To investigate age-related differences in knee-extension force control.
- To compare force control during isometric (IC), concentric (CC), and eccentric contractions (EC).
- To analyze variability in force production and timing during discrete contractions.
Main Methods:
- 24 young and 24 old healthy adults performed IC, CC, and EC of the knee extensors.
- Subjects matched a parabolic force-time profile at various submaximal levels (20-90% MVC).
- Contraction types included isometric, concentric (90-80° knee flexion), and eccentric (90-80° knee flexion) at 25°/s.
Main Results:
- Younger adults produced greater maximal voluntary contraction (MVC) force than older adults.
- Normalized variability (CV) of peak force and impulse was higher in older adults.
- Older adults showed greater variability in time to peak force and impulse duration, especially during ECs.
Conclusions:
- Older adults demonstrate reduced capacity for precise knee-extension force control compared to young adults.
- Eccentric contractions exhibit higher variability than isometric and concentric contractions, particularly in older individuals.
- Age-related decrements in motor control are evident in rapid, discrete muscle contractions.