Accepted Manuscript “Effects of pulsed electromagnetic field therapy on delayed-onset muscle soreness in biceps brachii” Hye-Seon Jeon, PhD, PT Sun-Young Kang, MSc, PT Joo-Hee Park, BHSc, PT HyunSook Lee, PhD PII:

S1466-853X(14)00010-8

DOI:

10.1016/j.ptsp.2014.02.006

Reference:

YPTSP 599

To appear in:

Physical Therapy in Sports

Received Date: 5 September 2013 Revised Date:

13 February 2014

Accepted Date: 20 February 2014

Please cite this article as: Jeon, H.-S., Kang, S.-Y., Park, J.-H., Lee, H.-S., “Effects of pulsed electromagnetic field therapy on delayed-onset muscle soreness in biceps brachii”, Physical Therapy in Sports (2014), doi: 10.1016/j.ptsp.2014.02.006. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Title in this study is

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“Effects of pulsed electromagnetic field therapy on delayed-onset muscle soreness in biceps brachii” Hye-Seon Jeon1, PhD, PT, Sun-Young Kang2, MSc, PT Joo-Hee Park2, BHSc, PT, Hyun-Sook Lee*3, PhD 1

Dept. of Physical Therapy, College of Health Science, Yonsei University,Korea 2

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Dept. of Ergonomic Therapy, The Graduate School of Health and Environment, Yonsei University, Dept. of Physical Therapy, The Graduate School, Yonsei University, Korea

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Dept.of Oriental Biomedical Engineering, College of Health Science, Sangji University, Korea

E-mail addresses: [email protected] (H.S. Jeon), rl[email protected] (S.Y. Kang) [email protected] (J.H.Park), [email protected] (H.S.Lee)

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Corresponding author: Hyun-Sook Lee, PhD. Tel: 82-10-4288-4050 / Fax: 82-33-7602496 /Address: Department of Oriental Biomedical Engineering, College of Health

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Science, Sangji University, Usan-dong, Wonju-si, Gangwon-do, Republic of Korea.

ACCEPTED MANUSCRIPT Effects of pulsed electromagnetic field therapy on delayed-onset muscle soreness in biceps brachii Abstracts

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Objective: to compare the effects of pulsed electromagnetic field (PEMF) therapy and sham treatment on DOMS-related variables in elbow flexors at 24, 48 and 72 hours after delayed onset muscle soreness (DOMS) induction exercise. Design: randomized, double-blind, placebo-controlled study. Setting: Yonsei University laboratory. Participants: In total, 30 healthy male college students Main outcome measures: Muscle soreness, peak torque, median frequency (MDF) and electromechanical delay (EMD) during isometric contraction at 24, 48 and 72 hours after DOMS induction exercise. Results: Overall, the application of the PEMF was found to be effective in reducing the physiological deficits associated with DOMS, including improved recovery of perceived muscle soreness, MDF, and EMD during isometric contraction. Our results did not show that PEMF treatment was mechanically more effective in isometric peak torque generation compared to the sham group. Conclusion: this study indicates that PEMF may be useful as a modality to reduce DOMS symptoms. However, further well-designed experiments are required to determine optimal treatment dosage and duration, and to investigate the physiological and clinical mechanisms of PEMF on DOMS. Introduction

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Delayed onset muscle soreness (DOMS) is one of the most common painful muscle conditions and is induced by unaccustomed physical activity or exercise (Cleak & Estons, 1992). DOMS is characterized by subsequent pain and discomfort predominantly within the skeletal muscle, reduction in joint range of motion (ROM) and decreased peak torque production (Connolly et al., 2003; Cheung et al., 2003). DOMS, in general, is first felt within 24 to 48 hours following cessation of exercise, peaks between 48 and 72 hours, subsides and eventually disappears by 5-7 days post-exercise (Kisner, 2007). Despite this natural recovery course, clinicians have tried to apply various electro-physical agents to reduce the intensity of DOMS-related symptoms and to decrease recovery time for maximal function. Frequencyspecific microcurrent therapy effectively alleviated the level of muscle soreness (Curtis et al., 2010), and an Acustat eletro-membrane microcurrent therapy showed significant reduction of the signs of DOMS compared with placebo group (Lambert et al., 2002). However, the general consensus regarding effects of electro-physical agents on DOMS has not reached an agreement amongst researchers. Microcurrent electrical and low-volt micro-amperage stimulation failed to demonstrate their effects on the alleviation of muscle soreness or other DOMS symptoms (Denegar and Perrin, 1992; Weber et al,, 1994), and also static magnetic field demonstrated no effect on recovery from DOMS (Reeser et al, 2005; Mikesky and Hayden, 2005). For many years, the use of the pulsed electromagnetic field (PEMF) was proposed as an alternative noninvasive medical treatment for influencing human physiology, via inducing electric current in deep tissue with the rapidly changing field of the magnetic impulses (Shupak et al., 2004). Regarding the recovery from DOMS, Rasmussen et al., (2013) reported that the application of PEMF effectively reduced soreness related with DOMS in marathon runners. On the other hand, Walsh et al., (2010) failed to show a favorable effect of PEMF on pain intensity and peak torque value on DOMS. As above mentioned, PEMF has been introduced as another remedy for DOMS, still has no consensus for the effect. Furthermore, the effectiveness of PEMF therapy on electromyography (EMG)-related variables in subjects with DOMS has not been studied yet. Therefore, the purpose of this study was to determine if the application of PEMF on elbow flexors would have a significant effect on variables associated with DOMS: MDF, EMD, peak isometric torque generation, and muscle soreness (VAS). The primary outcome measure was MDF. This study hypothesized that PEMF would reduce the severity and duration of signs and symptoms associated with DOMS compared to the sham group. 1

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Methods Subjects

Table1 General characteristics of the subjects

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Thirty healthy male college students volunteered for this study (Table I). The experimental procedure was approved by the Yonsei University’s Research Ethical Committee (certification number: # 2012-27), and all subjects provided written informed consent. Subjects were excluded from the study for the following reasons: currently involved in weight training, any known upper limb pathology or neurological deficit, undiagnosed pain, cardiovascular problems, pacemakers, epilepsy or diabetes mellitus. Each group consisted of 15 subjects and all subjects were randomly assigned to either the experimental group or the sham group. Sample size was determined based on preliminary data and power analysis using the G-power software (power of 0.8, α=.05) (Cohen, 1988). Each group consisted of 15 subjects and treatment was applied daily for three days according to group allocation. The subjects were asked to refrain from any form of strenuous physical activity, and were asked to avoid any form of medication, including anti-inflammatory agents, as well as any self-massage on the biceps brachii for the duration of the study.

(N=30)

PEMFa group (N1=15)

Sham group (N2=15)

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Age (years)

22.4±2.1b

23.8±2.7

.910

Height (cm)

174.0±6.9

176.0±4.6

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Weight (kg)

73.0±7.5

75.0±8.1

.450

Pulsed-electromagnetic field, b mean ± standard deviation, *independent t-tests were used to evaluate baseline equivalence between groups and significant level was set .05. Overview of experimental design

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This study used a randomized controlled design with a sham treatment group. The study lasted 4 consecutive days (Figure 1). On day 1, initial baseline values of all outcome measures were obtained prior to induction of DOMS. Immediately following DOMS induction, the subjects were treated under blind conditions, according to the randomized group allocation. All participants were right-handed, and the non-dominant left arm was always the testing arm. Treatment and assessment procedure on days 2, 3 and 4, was identical to day 1. The experiment group received PEMF therapy and the sham group received the sham treatment. Subjects in the sham group received the treatment with sham PEMF device that did not generate any magnetic pulses. Since this study was designed to compare the results from the sham group and the experimental group, sham device had the exact same shape, weight, sound, and same probe as the real PEMF stimulator, but did not generate any magnetic pulses. Specific aspects of the experimental design and procedures are detailed below. Data collection procedures and equipment Isokinetic dynamometer An isokinetic dynamometer was used to induce DOMS and to obtain peak torque data (Biodex Medical Systems, Inc., Shirley, NY, USA). The subjects were seated on a bench as described in the Biodex users’ manual 2

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and were restrained with straps around the shoulders and waist in order to inhibit any substitute movement. The dynamometer was calibrated at full elbow extension position (designated as 0°) at the beginning of each assessment. Prior to each measurement, the subject’s limb weight was measured with the limb parallel to the floor to determine (and thus eliminate) the effects of gravity upon torque values (Gleeson & Mercer, 1996). Peak torque values were achieved during maximal isometric contraction. Isometric peak torque was determined at a joint angle of 45° flexion from full extension, following an identical method that was demonstrated to be highly reliable (Howatson & van Someren, 2005). Three 5 s isometric contractions were performed with 10s rest. Subjects were given visual feedback via the dynamometer monitor, which has been previously shown to have a positive effect on motivational effort (Baltzopoulos et al., 1991). The maximum torque value produced during the respective repetitions was used for statistical analysis. Surface electromyography

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Surface EMG data were collected using a Noraxon Telemyo 2400T system (Noraxon, Inc., Scottsdale, AZ, USA) with a pair of AgCl surface electrodes 2 cm in diameter. After careful preparation of the skin (shaving, abrasion, and cleaning with alcohol), the electrode was attached to the mid-belly of the contracted biceps brachii muscle and the position was immediately marked with semi-permanent ink to ensure consistent placement on subsequent testing days (Cram et al., 1998). Raw EMG signals were collected with a band-pass filter of 20–450 Hz, sampled at 1000 Hz, and converted to ASCII files for analysis. The dynamometer and EMG data were synchronized on all procedures. Analogue data directly from the dynamometer was converted to a digital signal in parallel with the EMG signal; consequently both data sets were collected in synchrony before processing by the EMG software (Noraxon, Inc., Scottsdale, AZ, USA). This method made it possible to accurately determine the onset of surface EMG activity in relation to the onset of torque production. Visual analogue scale

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In this study, VAS at rest was used as a quantitative measure of muscle soreness. Each subject was asked to rate their level of soreness in the biceps brachii using VAS, where ‘0’ represented ‘absolutely no soreness’ and ‘10’ corresponded to ‘the most muscle soreness they could possibly bear’. The resting VAS scores were obtained before the DOMS induction on day 1, thereafter, the VAS scores were obtained before the PEMF/Sham treatment each day. The number of value was recorded by an independent researcher and the numerical results were used for later analysis. Reliability of the VAS for pain measurement in clinical setting as assessed by the ICC appears to be high (ICC=.99) (Gallagher et al., 2002) DOMS induction exercise protocol

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To induce DOMS, all participants performed repeated maximal voluntary elbow flexor contractions against the lever arm of an isokinetic dynamometer in concentric/eccentric mode. The DOMS induction exercise protocol consisted of two sessions of repetitive elbow contraction with five minutes rest. The first session was at an angular velocity of 60°/s and the second session was at 120°/s. The subjects were asked to accomplish maximum voluntary contractions during all the sessions. Each session was performed until exhaustion, which was defined as the point when the subject lost 70% of the initial eccentric and concentric peak torque (Vinck et al., 2006). Before the exercises, the dynamometer was calibrated at full elbow extension position (designated as 0°) and the concentric/eccentric elbow motion was performed though 30° to 120° range of elbow flexion. This procedure was based on a pilot study and previously described induction protocols (Vinck et al., 2006; Walsh et al., 2010). PEMF device and treatment procedure 3

ACCEPTED MANUSCRIPT The PEMF device consisted of a magnetic field generator and a flat multiple layer disk coil. Our Pulse Magnetic Field (PMF) stimulator was a prototype manufactured by Nuga Medical Co., Ltd, KOREA, and was certified as MRT-II by Ministry of Food and Drug Safety in Korea. It generates time-varying PMF which has peak magnetic field intensity of 0.2T, 5 mm away from coil and magnetic field pulse duration of 160 μs. The

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pulse duration was 480 μs, including 3 micro-pulses, and pulse repetition rate was 1 Hz. Since the waveforms of generated PMF show rapidly decayed sinusoidal signal, averaging magnetic fields over a period were calculated as 10.6 Gauss. Therefore, our PMF stimulator would deliver approximately 44 mW/cm2 at the skin surface. Real or sham PEMF treatments were applied to the most painful area on the biceps brachii with duration of 10 min. Data analysis

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Outcome measures of this experiment were MDF, peak torque, EMD during isometric muscle contraction and VAS score. EMD was determined as the time lag between the onset of EMG activity and the initiation of torque production during isometric contraction. A threshold value of 2 SD above the mean resting activity was used to determine onset of EMG activity and torque production. The reliability of this method has been previously established as a coefficient of variation of

Effects of pulsed electromagnetic field therapy on delayed-onset muscle soreness in biceps brachii.

to compare the effects of pulsed electromagnetic field (PEMF) therapy and sham treatment on DOMS-related variables in elbow flexors at 24, 48 and 72 h...
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