Muscle Activity and Perceived Loading During ...

Muscle Activity and Perceived Loading During Graded Rehabilitation Exercises with Dumbbells and Elastic Resistance Divya*, Chaya Garg**, Jitender Munjal*** * Student, Masters of Physiotherapy, Banarsidas Chandiwala Institute of Physiotherapy, Kalkaji, New Delhi-110019. ** Assistant Professor, Banarsidas Chandiwala Institute of Physiotherapy, Kalkaji, New Delhi-110019. *** Physiotherapist, Hindu Rao Hospital, Delhi

Abstract Background : Resistance exercises with heavy weights yield high levels of muscle activation, the ef cacy of more user friendly forms of exercises need to be examined. Aims & Objectives : The aim of the study is to compare the level of muscle activation and perceived loading between dumbbells and elastic resistance during graded rehabilitation exercises and to evaluate the relationship between muscle activation and perceived loading during each set of exercises using dumbbells and elastic resistance. Methodology: Fifty subjects (aged 18-25 yr) without any musculoskeletal disorder participated in the study.EMG activity was measured in two selected muscle during the exercises of full can, Empty can and prone full can during graded loading with elastic resistance ( red, green and blue ) and dumbbells ( 2-4 kg ).The order of exercises & loadings was randomized for each individual.EMG amplitude was normalized to the absolute maximum EMG amplitude obtained during MVIC and exercise testing. Immediately after each set of exercise, the Borg CR 10 scale was used to rate perceived loading during the exercise. Results: Resistance exercise with dumbbells as well as elastic resistance showing increasing EMG amplitude & perceived loading with increasing resistance. Normalized EMG activity of the muscles was not signi cantly different between dumbbells and elastic resistance. Perceived loading was weakly related to normalized EMG activity. Conclusion: Comparable high levels of muscle activation were obtained during graded rehabilitation exercises with dumbbells and elastic resistance and low perceived loading in elastic resistance as compared to dumbbells. It indicates that physical therapists can use either type of resistance while programming rehabilitation exercises. Key words: EMG – electromyography, MVIC – maximum isometric voluntary contraction

Introduction Resistance training has become an essential part of various rehabilitation protocols and an integral component of conditioning programs for those who wish to promote or maintain health and physical wellbeing , potentially enhance performance of motor skills, and prevent or reduce the risk of injury and disease.1 Electromyography (EMG) is commonly used to measure the level of muscle activation and provides an estimate of exercise intensity for speci c muscles involved in the movement.2 To yield high levels of muscle activation, resistance training usually is performed on machines or with free weights.3-9In clinical practice and for home-based rehabilitation, conventional resistance training devices may not always be feasible. Thus, the effectiveness of alternative exercise methods should be investigated. Strengthening exercises with elastic resistance have been shown to be a feasible alternative to heavy weights in certain situations. 8 A program of elastic resistance exercises to compliment regular strength training may be able to improve the strength of more isolated muscle

groups such as the rotator cuff. 11,12 Additionally, training these otherwise neglected muscles may even improve performance 12. The Borg CR10 scale has been widely used for rating the perceived intensity of various physiological experiences, such as physical exertion.11 Borg rating scale was developed to enable simple, reliable, and valid estimations of exercise intensity . The aim of present study was to compare the level of muscle activation and perceived loading between dumbbells and elastic resistance during graded rehabilitation exercises and to evaluate the relationship between muscle activation and perceived loading during each set of exercises using dumbbells and elastic resistance.

Methodology A group of 50 subjects with 22.16 ± 1.9 yrs, 165.1 ± 7.36 cm & 58.9 ± 8.63 kg were recruited on voluntary basis for the study. Potential subjects was apprised of the procedure and its potential risks and bene ts and the

The Physiotherapy Post, July - September 2012, Volume - 4. No. 3 135

Divya et al. Muscle Activity and Perceived Loading During Graded Rehabilitation Exercises with Dumbbells and Elastic Resistance

evaluation was done. Subjects those ful lled the study’s inclusive and exclusive criteria and gave their informed consent were included in the study. Prior to testing ,the subjects were familiarized with the testing procedure and exercise protocol. Subjects underwent testing for MVIC followed by the administration of exercise and testing. Testing: MVIC: Skin preparation: The electrode sites were prepared by shaving, abrasion with sandpaper, and swabbing with alcohol pads to lower skin resistance. Marking was made for the posterior deltoid, infraspinatus muscle and pairs of self adhesive electromyographic electrodes were placed on the markings made on the subjects dominant side according to the method of SENIAM.13 For posterior deltoid- 2.5cm inferior to posterior margin of acromion. For infraspinatus- midpoint and to nger breadths below and parallel to the spine of scapula. Two trials were performed for each muscle to test MVIC and the higher EMG response out of two trials was used for normalization of the peak EMG amplitude in the rehabilitation exercises.14 Participants were instructed to gradually increase muscle contraction force toward maximum over a period of 2 seconds, sustain the MVIC for 3 seconds, and slowly release the force. Verbal encouragement was given during all trials.14 For posterior deltoid-90 elbow exion and shoulder in neutral position against side of body. Subject oriented with back against wall and posterior aspect of elbow applying force into the wall with shoulder and elbow remaining in same plane during effort.15 For infraspinatus- subject standing with lateral aspect of upper arm against wall with elbow exed 90 and shoulder in neutral, towel placed under axilla and subject applies max external rotation affort into wall.15 Peak EMG Deltoid – Skin preparation and electrode placement were done as mentioned above. Peak EMG amplitude of deltoid is measured during 3 trials of each exercises with dumbbells and elastic resistance. Average of peak EMG amplitude noted from 3 trials of each exercises with dumbbells and elastic resistance used for analysis. Peak EMG Infraspinatus - Skin preparation and electrode placement were done as mentioned above. Peak EMG amplitude of infraspinatus is measured during 3 trials of each exercises with dumbbells and elastic resistance. Average of peak EMG amplitude noted from 3 trials of each exercises with dumbbells and elastic resistance used for analysis. Borg CR 10 scale - Immediately after each set of exercise, the Borg CR10 scale was used to rate perceived loading

of the respective muscle groups during the exercise. The meaning of the scale was carefully explained to each individual prior to testing.

Protocol Subjects performed the 3 exercises (empty can,full can and prone full can) with three different elastic resistance,[red, green and blue] and 3 corresponding dumbbells (2,3 and 4 kg).The subjects underwent 3 testing trials for each exercise and had a rest period of 1.5 minutes in between each set of testing. Exercises : All the exercises were performed in a slow controlled manner—lifting and lowering (3 seconds) without sudden jerks or acceleration. The order of exercises and loadings were randomized for each participant. Full can: subject was positioned in erect standing, arms on side and elbow in full extension and then abduction is performed to 90 in scapular plane with external rotation such that thumb faces upward. The exercise was performed with red elastic resistance and then with its respective weighted 2kg dumbbell. The same exercise was repeated with green and blue elastic resistance and their weighted 3kg and 4kg dumbbell respectively. The one end of the elastic resistance was secured under the subject’s foot and other end was grasped by the hand of the subject.16 Empty can: subject was positioned in erect standing, arms on side and elbow in full extension and then abduction is performed to 90 in scapular plane with internal rotation such that thumb faces downward. The exercise was performed with red elastic resistance and then with its respective weighted 2kg dumbbell. The same exercise was repeated with green and blue elastic resistance and their weighted 3kg and 4kg dumbbell respectively. The one end of the elastic resistance was secured under the subject’s foot and other end was grasped by the hand of the subject.16 Prone full can: subject was positioned in prone lying on bed with arm hanging freely of the bed and then horizontal abduction is performed to 100 in prone position with external rotation of shoulder such that thumb faces upward. The exercise was performed with red elastic resistance and then with its respective weighted 2kg dumbbell. The same exercise was repeated with green and blue elastic resistance and their weighted 3kg and 4kg dumbbell respectively. One end of thera band was grasped by the subject’s hand and other end was tied on bar of the bed.16 Surface EMG signal: For each individual muscle, peak EMG amplitude of the 3 repetitions were averaged.



Results was normalized by expressing the peak EMG value for each muscle and for each exercise as a percentage of the MVIC of corresponding muscle.16 Thus, the peak EMG values was expressed in percentage of MVIC values for each muscle.

Data Analysis The differences in EMG activity and perceived loading with dumbbells and elastic resistance was tested for statistical signi cance using paired t-test. Spearman correlation was used to determine the relationship among perceived loading and EMG activity in graded rehabilitation exercises.

Results Perceived Loading There was a type of resistance * perceived loading interaction in empty can exercise. A signi cant difference was found for the level of green elastic resistance & 3 kg dumbbell and blue elastic resistance & 4 kg dumbbell. No signi cant difference was found at the level of red elastic resistance & 2 kg dumbbell (graph 1.1). Perceived loading was found to be signi cantly higher in exercise with dumbbells than with elastic resistance. There was a type of resistance * perceived loading interaction in full can exercise. A signi cant difference was found between perceived loading in exercises with elastic resistance and dumbbells at all level of resistance ( graph 1.2). Perceived loading was found to be signi cantly lower in exercise with elastic resistance than with dumbbells at all levels of resistance. There was a type of resistance * perceived loading interaction in prone full can exercise. A signi cant difference was found between perceived loading in exercises with elastic resistance and dumbbells at all level of resistance ( graph 1.3). Perceived loading was found to be signi cantly lower in exercise with elastic resistance than with dumbbells at all levels of resistance.

infraspinatus interaction in full can exercise. A signi cant difference was found at the level of red elastic resistance & 2 kg dumbbell and green elastic resistance & 3 kg dumbbell. No signi cant difference was found at the level of blue elastic resistance & 4 kg dumbbell ( graph 1.5). EMG activity of infraspinatus was signi cantly higher for elastic resistance at the level of elastic resistance & 2 kg dumbbell and green elastic resistance & 3 kg dumbbell. There was a type of resistance * EMG activity of infraspinatus interaction in prone full can exercise. A signi cant difference was found at the level of green elastic resistance & 3 kg dumbbell. No signi cant difference was found at the level of red elastic resistance & 2 kg dumbbell and blue elastic resistance & 4 kg dumbbell (graph 1.6).EMG activity of infraspinatus was signi cantly higher for elastic resistance at the level of 3 kg & green elastic resistance. Muscle Activity of Deltoid There was a type of resistance * EMG activity of deltoid interaction in empty can exercise. A signi cant difference was found at the level of green elastic resistance & 3 kg dumbbell. No signi cant difference was found at the level of red elastic resistance & 2 kg dumbbell and blue elastic resistance & 4 kg dumbbell (graph 1.7). EMG activity of deltoid was signi cantly higher for dumbbell at the level of 3 kg & green elastic resistance. There was a type of resistance * EMG activity of deltoid interaction in full can exercise. No signi cant difference was found at the level of red elastic resistance & 2 kg dumbbell, green elastic resistance & 3 kg dumbbell and blue elastic resistance & 4 kg dumbbell (graph 1.8). There was a type of resistance * EMG activity of deltoid interaction in prone full can exercise. No signi cant difference was found at the level of red elastic resistance & 2 kg dumbbell, green elastic resistance & 3 kg dumbbell and blue elastic resistance & 4 kg dumbbell (graph 1.9).

Muscle Activity of Infraspinatus There was a type of resistance * EMG activity of infraspinatus interaction in empty can exercise. A signi cant difference was found at the level of blue elastic resistance & 4 kg dumbbell. No signi cant difference was found at the level of red elastic resistance & 2 kg dumbbell and green elastic resistance & 3 kg dumbbell ( graph 1.4).EMG activity of infraspinatus was signi cantly higher for dumbbell at the level of 4 kg & blue elastic resistance. There was a type of resistance * EMG activity of

Graph–1.1: Comparison of perceived loading in empty can exercise.



Graph–1.5: Comparison of EMG activity of infraspinatus in full can exercise.

Graph–1.2: Comparison of perceived loading in full can exercise .

Graph–1.6: Comparison of EMG activity of infraspinatus in prone full can exercise

Graph–1.3: Comparison of perceived loading in prone full can exercise.

Graph–1.7: Comparison of EMG activity of deltoid in

Graph–1.4: Comparison of EMG activity of infraspinatus in empty can exercise.

empty can exercise.



green elastic resistance & 3 kg dumbbell in full can exercise and blue elastic resistance & 4 kg dumbbell in prone full can exercise.The muscle activity of deltoid was found to be similar with both kind of resistance in all the exercises except 3 kg dumbbell & green elastic resistance in empty can exercise.There was a weak positive correlation between perceived loading measured by Borg’s CR 10 scale and muscle activity ( EMG activity of Infraspinatus & Deltoid) using elastic resistance and dumbbells. The results obtained in our study con rmed that the use of elastic resistance produces equivalent EMG activity of muscles to those obtained with dumbbells. Our result support the previous studies done by Lars L.Anderson 2010.15 and Christopher J.Hughes 2005.20Although ,previous study by Michael .M.Reinold et al 16quanti ed EMG activity of supraspinatus and deltoid & found higher activation level in all graded rehabilitation exercises involved in the study. We studied infraspinatus & deltoid & we came out to have high peak amplitude in all graded rehabilitation exercises .We studied the infraspinatus activity because another researchers Christopher J.Hughes et al20 suggested that exercises in external rotation & full can exercise are the good position to stimulate infraspinatus & posterior deltoid.

Graph–1.8: Comparison of EMG activity of deltoid in full can exercise

We had found that perceived loading is less in elastic resistance as compared to dumbbells in all the exercises and it was weakly related with muscle activity. Whereby Lars L.Anderson et al 15 had found that perceived loading was moderate to strongly related to muscle activity.

Graph–1.9: Comparison of EMG activity of deltoid in prone full can exercise.

Discussion The study compares the muscle activation and perceived loading during graded rehabilitation exercises with elastic resistance & dumbbells. We found that perceived loading was signi cantly lower with elastic resistance than with dumbbells at all levels of resistance in all the exercises except red elastic resistance and 2 kg dumbbell in empty can exercise. The muscle activity of infraspinatus was found to be higher with dumbbells in empty can exercise but it achieve signi cance only at the level of blue elastic resistance & 4 kg dumbbell where as in full can & prone full can exercise muscle activity was higher with elastic resistance at all the levels except 4 kg dumbbell in full can exercise. Though this difference reach the signi cant level only in red elastic resistance & 2 kg dumbbell &

In our study high levels of muscle activation were obtained ,corresponding to perceived loading of 4 & higher on the Borg CR 10 scale. Thus ,compared with the other 2 exercises of the present study, relatively high loadings are needed to obtain a high level of muscle activation. Although very high intensities are not recommended during the initial phases of rehabilitation, such intensities may necessary during later stages to ensure high levels of muscle activation. The present study showed clear similarities between dumbbells and elastic resistance with regard to muscle activation & low perceived loading with elastic resistance during graded rehabilitation exercises. Although not speci cally investigated in this study, some differences also may exist. Whereas dumbbells provide isotonic resistance, elastic resistance increases linearly with elongation of the material.14 Furthermore, it should be noted that all exercises were performed in a controlled manner and that differences between elastic resistance and dumbbells may exist during more explosive movements. Whereas the inertia of the dumbbell results in increased total moment of force during accelerative movements,



the inertia of the elastic resistance is negligible. Thus, the results of the present study apply only for exercises performed according to general recommendations of basic strength training and rehabilitation (ie, in a controlled manner without sudden jerks or acceleration). Although some accommodation comes from prestretching of the elastic tubing, as few as 20 repetitions appear to stabilize the material.14 Because all elastic tubings were stretched several times during pilot testing in the present study, it is unlikely that the material properties were changed during actual testing. With the use of surface EMG, there is an inherent risk of cross talk from neighboring muscles. Even though a relatively short inter-electrode distance of 2 cm was used, it is possible that EMG recordings from the infraspinatus muscles may have been affected by surrounding muscles to some extent. To our knowledge, the optimal interelectrode distance for minimizing cross talk while retaining signal amplitude has not been determined for these particular muscles.

Conclusion Comparable high levels of muscle activation were obtained during graded rehabilitation exercises with dumbbells and elastic resistance It indicates that physical therapists can use either type of resistance while programming rehabilitation exercises. Perceived loading is low in elastic resistance as compared to dumbbells.

References 1. Taylor NF, Dodd KJ, Damiano DL. Progressive resistance exercise in physical therapy: a summary of systematic reviews. Phys Ther. 2005;85:1208–1223. 2. Andersen LL, Kjaer M, Andersen CH, et al. Muscle activation during selected strength exercises in women with chronic neck muscle pain. Phys Ther. 2008;88:703–711. 3. Ballantyne BT, O’Hare SJ, Paschall JL, et al. Electromyographic activity of selected shoulder muscles in commonly used therapeutic exercises. Phys Ther. 1993;73: 668–677. 4. Decker MJ, Hintermeister RA, Faber KJ, Hawkins RJ. Serratus anterior muscle activity during selected rehabilitation exercises. Am J Sports Med. 1999;27:784 –791. 5. Ekstrom RA, Donatelli RA, Soderberg GL. Surface electromyographic analysis of exercises for the trapezius and serratus anterior muscles. J Orthop Sports Phys Ther. 2003;33:247–258. 6. Hintermeister RA, Lange GW, Schultheis JM, et al. Electromyographic activity and applied load during

shoulder rehabilitation exercises using elastic resistance. Am J Sports Med. 1998;26:210–220. 7. Ratamees NA, Alvar BA, Evetoch TK, et al. American College of Sports Medicine position stand: Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009;41:687–708. 8. Andersen LL, Magnusson SP, Nielsen M, et al. Neuromuscular activation in conventional therapeutic exercises and heavy resistance exercises: implications for rehabilitation.Phys Ther. 2006;86:683–697. 9. Ribeiro F, Teixeira F, Brochado G, Oliveira J. Impact of low cost strength training of dorsi- and plantar exors on balance and functional mobility in institutionalized elderly people. Geriatr Gerontol Int. 2009; 9:75– 80. 10. Patterson RM, Stegink Jansen CW, Hogan HA, Nassif MD. Material properties of Thera-Band Tubing. Phys Ther. 2001;81: 1437–1445. 11. Borg G.Borg”s Percieved Exertion and Pain Scales. Champaign,IL:Human Kinematics;1998. 12. Phillip Page .A Comparison of isotonic and elastic resistance exercises on trapezius muscle balance in overhead athletes.B.S., Louisiana State University, 1990 M.S., Mississippi State University, 1992 B.S., L.S.U. Health Sciences Center, 1994 December, 2009. 13. SENIAM Website: available at: http://www.seniam. org Accessed May 1, 2009. 14. Lars L. Andersen, Christoffer H. Andersen, Ole S. Mortensen, Otto M. Poulsen, 15. Inger Birthe T. Bjørnlund, Mette K. Zebis. Muscle activation and perceived loading during rehabilitation exercises. PhysTher 2010; volume 90;4. 16. Christopher J.Hughes, Kenneth Hurd, Allan Jones, Stephen Sprigle. Resistance properties of theraband tubing during shoulder abduction exercise. Journal of sports & sports physical therapy.1999;29(7):413420. 17. Michael M. Reinold, Leonard C. Macrina, Glenn S. Fleisig EMG analysis of the supraspinatus and deltoid muscle during 3 common rehabilitation exercises. Journal of athletic training2007; 42(4):464-469. 18. Christopher J. Hughes, PT, PhD, OCS, CSCS; Aaron McBride, MPT,ATC. The use of surface EMG to determine muscle activation during isotonic and elastic resistance exercises for shoulder rehabilitation.Orthopaedic Practice Vol.17;2:05.
