The Thermal Effects of Pulsed Shortwave Diathermy on Electromyography and Mechanomyography Sarah Marek November 17, 2004.
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The Thermal Effects of Pulsed Shortwave Diathermy on Electromyography and
Mechanomyography
Sarah Marek
November 17, 2004
Objectives
Background & Significance Purpose Research Questions & Hypotheses Design Methods Data Analysis Assumptions, Delimitations, & Limitations Research Benefits
Why Use Heat?
Physiological effects of heat Increases extensibility of collagen tissues Relaxes muscles Provides pain relief Increases blood flow
Muscle is often the target tissue Need deep penetration of heat Need large treatment area
Pulsed Shortwave Diathermy (PSWD) & Ultrasound are considered deep heating modalities
Why Use PSWD?
Superficial Heat Pack(Trowbridge et al 2004)
Ultrasound(Garrett et al 2000)
PSWD(Garrett et al 2000)
Increased intramuscular temperature 1.0°C at 2 cm deep
Increased intramuscular temperature 0.17°C at 3 cm deep
Increased intramuscular temperature 4.58°C at 3 cm deep
Treatment size was the same as the PSWD treatment size
Treatment size was the size of the diathermy drum
Returned to baseline temperature at 14.88 min
Returned to baseline temperature at 38.5 min
Studies have shown PSWD increases intramuscular temperature about 4.0°C during treatment and decays about 1.8°C 10min post-treatment (Draper et al 1999; Draper et al 1997; Castel et al 1997)
Heat & Tissue Properties
Low-load, long-duration stretching with PSWD causes a greater increase in range of motion (ROM) than stretch alone
Increases in ROM were still present for a period after the treatment was stopped
May cause changes to the properties of the musculotendinous unit
(Peres et al 2002; Draper et al 2004)
EMG & MMG
Electromyography (EMG) – records the sum of the electrical muscle action potentials
Mechanomyography (MMG) – records the sounds caused by the lateral oscillations of the contracting skeletal muscles
Together EMG & MMG can give information about the relationship between the electrical and mechanical events of excitation-contraction coupling
Purpose
PSWD may change the musculotendinous properties of skeletal muscles
EMG & MMG can characterize the changes that PSWD may cause to the neurological and mechanical properties of skeletal muscles
Purpose: To examine the thermal effects of PSWD on force
production, EMG, and MMG during isometric ramp contractions
Research Questions
Does a 20-min PSWD treatment change EMG and MMG during an isometric ramp contraction?
Does a 20-min PSWD treatment change force production, EMG, and MMG during maximal voluntary contractions?
Main Hypotheses
As temperature increases we expect:1. MMG amplitude will not change during the MVC
2. MMG amplitude to increase during the ramp contraction
3. EMG frequency to increase
4. No change in EMG amplitude
5. MMG frequency to increase
As force production increases 1. EMG amplitude will increase linearly
2. MMG amplitude will increase up to 80% MVC and then decrease to 100%
Design 2 × 3 mixed factorial design to examine force production, EMG,
and MMG during MVCs
Time
1. Pre-treatment
2. Post-treatment
Treatment
1. Control
2. Diathermy
3. Sham-Diathermy
Design 2 × 3 × 9 mixed factorial design to examine EMG and MMG
during isometric ramp contractions
Time
1. Pre-treatment
2. Post-treatment
Treatment
1. Control
2. Diathermy
3. Sham-Diathermy
%MVC
1. 5%
2. 15%
3. 25%
4. 35%
5. 45%
6. 55%
7. 65%
8. 75%
9. 85%
Dependent Variables
MVC Ramp
Force Production
EMGrms Amplitude EMG Instantaneous Amplitude (IA)
MMGrms Amplitude MMG IA
EMG Median Frequency (MDF) EMG Instantaneous Mean Frequency (IMF)
MMG MDF MMG IMF
Methods Subjects
34 Males Ages 19 to 35 yrs Free of health risks No injury within the past 12 months to the knee, thigh, or lower
leg Skinfold thickness ≤ 30 mm No metal implants or cardiac pacemakers
Randomized group placement Control (n=10) Diathermy (n=12) Sham-diathermy (n=12)
Methods
Procedure Familiarization Trial
Informed consent Health history questionnaire Skinfold measurements Trials
Experimental Trial EMG & MMG sensor placement Pre-test Thermocouple insertion Treatment Post-test
Methods
Testing 2 MVCs
Isometric contraction at 60° knee flexion 3 sec contraction
2 ramp contractions 3 sec isometric contraction at 60° knee flexion at 5% MVC Gradual, linear increase from 5% to 85% MVC
2 min rest between each trial
Methods
Instruments 16-channel Isothermex
Isothermex, Columbus, OH Intramuscular-implantable thermocouple
Physitemp Instruments, Type IT-21 (diameter = .41 mm), Clifton, NJ Biodex System 3 dynamometer
Biodex Medical Systems, Inc., Shirley, New York Active miniature rugged accelerometer
Entran Inc., EGAS-FS, Fairfield, NJ Bipolar surface electrode arrangement
Moore Medical, Ag-AgCl
Thermocouple
Data Analysis 2 × 3 (TIME × TREATMENT) mixed factorial ANCOVA to
analyze the dependent variables for the MVCs
2 × 3 × 9 (TIME × TREATMENT × %MVC) mixed factorial ANCOVA to analyze the dependent variables for the ramp contractions
Change in intramuscular temperature from baseline will be the covariate
Assumptions
Subjects will accurately fill out the health history questionnaire
Subjects will perform the MVC and ramp contractions to the best of their ability
Delimitations
Males between the ages of 19 and 35 years of age Males without injury to the right knee, thigh, or lower leg
within the past 12 months Males that have a thigh skinfold thickness ≤ 30 mm Males who are able to complete a successful isometric
ramp contraction
Limitations
Differences in skinfold thickness between left and right thigh
Changes in room temperature between subjects Learning effect Subject selection Subject communication Psychological effects
Research Benefits
Provide allied health care practitioners (physicians, certified athletic trainers, physical therapists, occupational therapists, nurses, and massage therapists) with valuable information regarding the effects of diathermy on neuromuscular function
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