Muscle Function and Aging Dain La Roche Ph

Muscle Function and Aging Dain La. Roche, Ph. D

Introduction n Muscle force and power production decrease with aging n Locomotion, fall risk, activities of daily living, and independence n Is the loss of muscle function associated with aging process or physical inactivity? JOHNSON STATE COLLEGE JOHNSON, VERMONT

Muscle Function n 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 n May affect rate of force development (power) in addition to total force JOHNSON STATE COLLEGE JOHNSON, VERMONT

Motor Unit

Muscle Quantity and Quality JOHNSON STATE COLLEGE JOHNSON, VERMONT

Purpose n To examine the effects of age and physical activity on the determinants of muscle power JOHNSON STATE COLLEGE JOHNSON, VERMONT

Methods n Able-bodied, independent women aged 65 -80 years old n Historical physical activity questionnaire and muscle function test will be administered n Cybex Dynamometer and Biopac Data Acquisition System – Force – Electromyography (EMG) JOHNSON STATE COLLEGE JOHNSON, VERMONT

Cybex Dynamometer JOHNSON STATE COLLEGE JOHNSON, VERMONT

Procedure n Participants will be secured to the dynamometer for knee extension n Surface EMG electrodes will be placed over the vastus lateralis muscle n Subjects will maximally extend the knee as quickly as possible following a visual stimulus. n EMG will be recorded with Biopac PRO v 3. 6. 7 JOHNSON STATE COLLEGE JOHNSON, VERMONT

Visual Stimulus JOHNSON STATE COLLEGE JOHNSON, VERMONT

Integrated EMG PMT Stimulus Force Time to Peak EMD Rate of Force Development Stimulus JOHNSON STATE COLLEGE JOHNSON, VERMONT

Measures n Premotor time – calculated by determining the time from initiation of the stimulus to detection of EMG n Electromechanical delay – determined by calculating the time from the onset of the EMG until the detection of force n Time to peak force – determined by calculating the time from the onset of the stimulus until peak force JOHNSON STATE COLLEGE JOHNSON, VERMONT

Measures n Peak force – the highest force measured n Rate of force development – slope of the force versus time line n Onset EMG – comparison of onset EMG to peak force EMG JOHNSON STATE COLLEGE JOHNSON, VERMONT

JOHNSON STATE COLLEGE JOHNSON, VERMONT

Expected Results n Greater in Inactive: – Pre-motor time – Electromechanical Delay – Time to Peak n Lower in Inactive: – Rate of Force Development – Onset to Peak EMG Ratio n Lower Power Output in Inactive! JOHNSON STATE COLLEGE JOHNSON, VERMONT

Next Steps Subject recruitment and data collection n Power training intervention n Muscle function and aging n JOHNSON STATE COLLEGE JOHNSON, VERMONT

Thank You! Johnson State College JOHNSON STATE COLLEGE JOHNSON, VERMONT