The influence of knee extensor fatigue on lower extremity muscle activity during chair rise in young and older adults.
Level 3 - non-randomized controlled study
Non-randomized pre-post laboratory comparative study across two age cohorts
PubMed 30317389 · doi:10.1007/s00421-018-3999-4
What was done
Researchers evaluated changes in lower extremity muscular effort (% maximum voluntary contraction, %MVC) and temporal activation patterns during a sit-to-stand (STS) task following isolated dynamic knee extensor fatiguing exercise. Surface electromyography was recorded before and after fatigue in 22 healthy participants: 11 young adults and 11 older adults.
What was found
The abstract reports directional changes without exact numerical values, standard deviations, or effect sizes. Knee extensor fatigue caused significant increases in relative effort (%MVC) for the soleus, gastrocnemius, and gluteus maximus across both age groups during STS. Rectus femoris %MVC increased significantly across the entire STS movement in both young and older adults, whereas vastus lateralis amplitude increased only in preparation for seat-off. Muscle temporal characteristics were generally invariant, except for an earlier activation onset in ankle musculature among older adults.
Why it matters
This study shows that when knee extensors are fatigued, the neuromuscular system compensates during chair rising by redistributing demand to synergist muscles and non-fatigued hip and ankle musculature, a mechanism preserved in healthy older adults.
Limits
Small sample size (n = 22 total, 11 per group). The abstract does not report numerical data, confidence intervals, or exact p-values. Kinematics, joint kinetics, and fall risk outcomes were not evaluated, and findings in healthy individuals cannot be generalized to frail or mobility-impaired older populations.
Cited by
- context Electromyography (EMG) testing shows that quadriceps activation is very high during everyday tasks like climbing stairs or standing up from a couch, while glute activation remains low.