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Muscle Function and Aging. Dain LaRoche, Ph.D. Introduction. Muscle force and power production decrease with aging Locomotion, fall risk, activities of daily living, and independence Is the loss of muscle function associated with aging process or physical inactivity?. Muscle Function. - PowerPoint PPT Presentation
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Muscle Function and Muscle Function and AgingAging
Dain LaRoche, Ph.D
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
IntroductionIntroduction
Muscle force and power production decrease with aging
Locomotion, fall risk, activities of daily living, and independence
Is the loss of muscle function associated with aging process or physical inactivity?
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Decrease in muscle function due to: – Loss of muscle mass and quality – Decrease in type II (fast twitch) fibers– Inability to recruit motor units– Decreased motor unit firing rate
May affect rate of force development (power) in addition to total force
Muscle FunctionMuscle Function
Motor UnitMotor Unit
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Muscle Quantity and Muscle Quantity and QualityQuality
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
PurposePurpose
To examine the effects of age and physical activity on the determinants of muscle power
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
MethodsMethods
Able-bodied, independent women aged 65-80 years old
Historical physical activity questionnaire and muscle function test will be administered
Cybex Dynamometer and Biopac Data Acquisition System– Force– Electromyography (EMG)
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Cybex Dynamometer
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
ProcedureProcedure
Participants will be secured to the dynamometer for knee extension
Surface EMG electrodes will be placed over the vastus lateralis muscle
Subjects will maximally extend the knee as quickly as possible following a visual stimulus.
EMG will be recorded with Biopac PRO v3.6.7
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Visual StimulusVisual Stimulus
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Integrated EMG
Force
Stimulus
Stimulus
Rate of Force Development
Time to Peak
PMT
EMD
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
MeasuresMeasures
Premotor time – calculated by determining the time from initiation of
the stimulus to detection of EMG
Electromechanical delay – determined by calculating the time from the onset of
the EMG until the detection of force
Time to peak force – determined by calculating the time from the onset of
the stimulus until peak force
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
MeasuresMeasures
Peak force – the highest force measured
Rate of force development– slope of the force versus time line
Onset EMG– comparison of onset EMG to peak force EMG
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Expected ResultsExpected Results
Greater in Inactive:– Pre-motor time– Electromechanical Delay– Time to Peak
Lower in Inactive:– Rate of Force Development– Onset to Peak EMG Ratio
Lower Power Output in Inactive!
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Next StepsNext Steps
Subject recruitment and data collection
Power training intervention Muscle function and aging
JOHNSON, VERMONT
STATE COLLEGEJOHNSON
Thank You!Thank You!
Johnson State College
