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