Muscle Function and Aging

1
Muscle Function and Aging

• Dain LaRoche, Ph.D

2
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?

3
Muscle Function

• 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

4
Motor Unit
5
Muscle Quantity and Quality
6
Purpose

• To examine the effects of age and physical
  activity on the determinants of muscle power

7
Methods

• 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)

8
Cybex Dynamometer
9
Procedure

• 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

10
Visual Stimulus
11
Integrated EMG
Force
12
Measures

• 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

13
Measures

• 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

14
(No Transcript)
15
Expected 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!

16
Next Steps

• Subject recruitment and data collection
• Power training intervention
• Muscle function and aging

17
Thank You!

• Johnson State College