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 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 MVCRamp Force Production EMG rms AmplitudeEMG Instantaneous Amplitude (IA) MMG rms AmplitudeMMG IA EMG Median Frequency (MDF)EMG Instantaneous Mean Frequency (IMF) MMG MDFMMG 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 ThermocoupleThermocouple

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