|Year : 2020 | Volume
| Issue : 2 | Page : 194-199
Electromyographic activity of vastus lateralis muscle of dominant thigh (right) in relation to performance levels during the leg/knee extension exercise performance with 30 repetition maximum load
Dhananjoy Shaw1, Deepak Singh1, Manvinder Kaur2, Umesh Kr Ahlawat1, Dinesh Bhatia3
1 Biomechanics Laboratory, Indira Gandhi Institute of Physical Education and Sports Sciences, University of Delhi, New Delhi, India
2 Department of Biomedical Engineering, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Haryana, India
3 Department of Biomedical Engineering, North Eastern Hill University, Shillong, Meghalaya, India
|Date of Submission||14-Mar-2020|
|Date of Decision||04-Apr-2020|
|Date of Acceptance||19-Apr-2020|
|Date of Web Publication||18-Dec-2020|
Dr. Dhananjoy Shaw
Officiating Principal, Indira Gandhi Institute of Physical Education and Sports Sciences, University of Delhi, New Delhi - 110 018
Source of Support: None, Conflict of Interest: None
CONTEXT: Leg/knee exercise has been extensively used to study the electromyographic (EMG) activity of the quadriceps muscle group. However, conducted studies have several limitations related to methodology.
AIMS: To assess the effect of performance level on the EMG activity of the vastus lateralis (VL) muscle of the dominant thigh (right) during the performance of leg/knee extension exercise with 30 repetition maximum load. Thigh dominance was based on the result of leg dynamometer.
SETTING AND DESIGN: The study was a cross-sectional study, and data collection was conducted in Indira Gandhi Institute of Physical Education and Sports Sciences, University of Delhi, India.
MATERIALS AND METHODS: Healthy intercollegiate-level male sportspersons (n = 19, age = 19.84 ± 2.1 years, height = 171.38 ± 8.48 cm, and weight = 70.42 ± 13.8 kg) were randomly selected as the subjects. Leg extension exercise was performed on Cybex VR1 leg curl exercise device and EMG data were acquired using a 4-Channel Wireless EMG BIOPAC Inc. MP150 system. A criterion called relative impulse (RI) was developed. Based on the magnitude of RI of the subject, nine subjects were enlisted and were equally divided into high-performance (HP), mid-performance (MP), and low-performance (LP) groups. The raw EMG signals were quantified, and time-domain (root mean square [RMS] and integrated EMG [IEMG]) and frequency-domain variables (Median Frequency [MDF] and Mean Frequency [MNF]) were derived with the help of? MATLAB.
STATISTICAL ANALYSIS USED: One-way analysis of variance and least significant differences (at P < 0.05) for post hoc analysis were used to determine the significant influence of performance level.
RESULTS: All three groups (HP, MP, and LP) displayed a declining pattern in the EMG activity of the VL in the selected variables, except MP group in the MDF, MNF, and RMS. Significant effect of performance level was observed between LP and HP groups and between MP and HP groups in MDF and MNF (P < 0.05).
CONCLUSION: The findings are useful for understanding muscular fatigue as they focus on its electrophysiological aspect.
Keywords: Frequency-domain variables, relative impulse, time-domain variables, vastus lateralis
|How to cite this article:|
Shaw D, Singh D, Kaur M, Ahlawat UK, Bhatia D. Electromyographic activity of vastus lateralis muscle of dominant thigh (right) in relation to performance levels during the leg/knee extension exercise performance with 30 repetition maximum load. BLDE Univ J Health Sci 2020;5:194-9
|How to cite this URL:|
Shaw D, Singh D, Kaur M, Ahlawat UK, Bhatia D. Electromyographic activity of vastus lateralis muscle of dominant thigh (right) in relation to performance levels during the leg/knee extension exercise performance with 30 repetition maximum load. BLDE Univ J Health Sci [serial online] 2020 [cited 2021 Apr 14];5:194-9. Available from: https://www.bldeujournalhs.in/text.asp?2020/5/2/194/303963
Leg/knee extension exercise is one of the frequently used exercises to strengthen the quadriceps muscles as it involves the dynamic movement of knee extension, which is executed by the concentric contraction of quadriceps muscle group.,,, Knee extension movement is the most common movement performed at different sports and games. Leg/knee extension exercise has been extensively used to study the electromyographic (EMG) activity of the quadriceps muscles.,,,,,, However, these researches contain several limitations. Majority of these studies are based on isokinetic dynamometers,,,, instead of using an isotonic leg/knee extension exercise machines, and this questions the applicability of the findings to the field of exercise and training as loading mechanism of isokinetic dynamotor is different and it is mostly used in clinical setting. However, the use of exercise machine in the studies has another limitation as conducted studies had segmented and quantified the raw EMG activity data on the basis of repetitions and specific joint angle in range of motion,, and this precludes the comparison of their findings with the findings of the other studies that used isometric contractions to study the activity of quadriceps muscles as these have segmented and quantified their raw EMG activity data based on time intervals., The isometric contractions' protocol researches that had attempted to study the effect of performance level of the subjects on their EMG activity and fatigue response of quadriceps muscle group have an observable limitation in their criteria of dividing performance level as they have based performance division on the duration of sustenance of the contraction,, and this most often overlooks the intensity of the contraction. Thus, these studies lack to comprehensively investigate the effect of performance level on the EMG activity and muscle fatigue responses of quadriceps muscle group because the mechanism of muscle fatigue depends on the duration and intensity of the activity/exercise. Another limitation with is that conducted studies is that they have divided the subjects into only two performance levels, namely high-performance (HP) and low-performance (LP) groups,, and this had disregarded those subjects who perform in the middle of this performance division spectrum. The proposed study has sought to efface the above-stated problems by adopting the necessary measures with the purpose to comprehensively assess the EMG activity of vastus lateralis (VL) and the effects of performance level on it.
| Materials and Methods|| |
The inclusion criteria of the subjects were that the subjects must be above 18 years of age, nonalcoholic, and willingness to partake in the study while not suffering from any medical condition which might obstruct the functioning of neuromuscular system. The exclusion criteria were that the subjects must not have any medical conditions/contractures/deformities in the joints or suffering from skin condition which might impede the fixation of the electrodes on the body surface. Based on the inclusion criteria, the potential participants of the study were sequentially listed from the Indira Gandhi Institute of Physical Education and Sports Sciences, University of Delhi, New Delhi. Then, 50 participants were selected from the list using a lottery system. However, due to issues with voluntary participation and errors in data collection with the voluntary participants, data of only 19 subjects were considered for the study. Thus, 19 healthy intercollegiate-level male sportspersons (n = 19, age = 19.84 ± 2.1 years, height = 171.38 ± 8.48 cm, and weight = 70.42 ± 13.8 kg) were included as the subjects of the study. Before participation, each subject was explained about the purpose and protocol to be followed for the study and they were asked to undergo few predata collection trials to make them familiar with the study along with the determination of their 30 repetition maximum (RM) for the exercise through trial-and-error method. The average 30 RM value of the subjects was 29 (±7.69) kg. Before initiating the tests, written informed consent was obtained from each subject to fulfill the ethical requirements. As the study was noninvasive in nature and appropriate written informed consent was obtained from all the subjects, the relevant ethical requirement was met. Cybex VR1 leg curl exercise device (Cybex, Division of Lumex Inc., Ronkonkoma, New York, USA) was used for performing leg extension exercise. EMG data were acquired using a 4-Channel Wireless EMG BIOPAC Inc., MP 150 system (CMRR: 110 dB at 50/60 Hz, maximum sampling rate: 200 K samples/s, gain: 5–50,000, and input impedance: 2 MO). The skin was rubbed with cotton containing alcohol to minimize the skin impedance, thereby improving the quality of signal acquisition. Disposable electrodes (44 mm × 32 mm × 1 mm) were placed on the subject's selected muscle following a standard protocol to acquire the EMG data. The interelectrode distance was 20 mm, center to center. After the subject preparation was done, subject was appropriately seated on the Cybex VR1 leg curl exercise device. Each subject was assigned to 30 RM load, and they were asked to perform 30 repetitions of the leg extension exercise with no pause in-between the repetitions. Thirty RM was opted for the study as 25–30 is considered as the appropriate load for developing and measuring muscular strength and endurance in an athlete. EMG activity was recorded simultaneously from the VL muscle of the dominant or right lower limb of all the subjects during the performance of the exercise. The dominance of the limb was measured by asking the subjects about which leg they felt is the stronger than the other, and all the subjects reported their right thigh as the strongest and it was also confirmed by using a leg dynamometer. Sampling rate during acquisition was set to 2000 Hz as per the Nyquist criteria. The collected data were stored using AcqKnowledge 4.3 software (BIOPAC Inc., USA). To account for both intensity and duration of exercises, a new criterion called relative impulse (RI) was developed and calculated for each subject. RI is an equation formulated from the equation of impulse from physics. However, in RI, the 30 RM was used an equivalent of force applied and duration of exercise was adopted as the duration of force application. To account for the differences in body mass of the subjects and its effect on 30 RM value, the whole equation is divided by the body weight. The RI of each subject was calculated from their 30 RM, duration of exercise, and the body weight using the equation 1.
RI = (30 RM [in kg] × duration of time taken for exercise [s])/(body weight [kg]) (1)
Based on the magnitude of RI, nine subjects were enlisted and were divided into HP group (n = 3), mid-performance (MP) group (n = 3), and LP group (n = 3). The top three subjects with greater RI (RI = 408.21 ± 67.27) value were included in HP group, the bottom three subjects with the lowest value were included in LP group, and the subject with the median value (RI = 132.65 ± 11.73) and two subjects closer to the median value were included in the MP group (n = 3). The RI value of each group is stated in [Table 1].
Then, the raw EMG data of the right VL were segmented into 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 390, and 420 s for each subject of HP group. The raw EMG data of the right VL of each subject of MP were segmented into 30, 60, 90, 120, and 150 s. The raw EMG data of the right VL of each subject belonging to LP group were segmented into 30, 60, 90, and 120 s. Different data segmentation of EMG data for each group was based on the exercise duration of the subjects in the group. All this was done to better understand the influence of muscle fatigue with progression of time with regard to the performance level of the subject. The raw EMG signals acquired from the subjects were quantified with the help of MATLAB. For processing of EMG signal, notch filter was applied to remove 50 Hz noise interference from the signal. A cascaded low-pass filter (20 Hz) and a high-pass filter (450 Hz) were subsequently applied to remove other noise sources from the signal. Time- and frequency-domain variables were extracted from the filtered signal, namely root mean square (RMS), integrated EMG (IEMG), median frequency (MDF), and mean frequency (MNF), respectively, for each subject belonging to each group. These variables were selected as these are frequently used for determining the changes associated with fatigue in the muscle. [Table 2] contains the list of variables used in the study.
|Table 2: Selected variables to study the electromyographic (activity) of vastus lateralis|
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The EMG pattern for the selected muscle for each performance group was determined by plotting the mean values of selected time- and frequency-domain variables of each group on a line graph with respect to the segmented time interval for the group. One-way analysis of variance (ANOVA) was carried out to determine whether the influence of performance is statistically significant during the leg extension exercise in the VL muscle of the participants. The selected variables to carry out one-way ANOVA are presented in [Table 3].
After determining the statistical significance among groups, least significant difference (LSD) for the statistically significant variables was conducted as post hoc test. The level of significant was set to P < 0.05. All the statistical analysis was carried out using IBM SPSS Statistics Software(IBM,Armonk, New York, United States).
| Results|| |
The mean and standard deviation value of all the selected variables derived from the raw EMG data of VL muscle are presented in [Table 4.1], [Table 4.2], [Table 4.4.3]. According to [Figure 1],[Figure 2],[Figure 3],[Figure 4], all three performance groups displayed a “declining pattern” in their EMG activity of the VL muscle across all the selected variables, except MP group in the variables, namely MDF, MNF, and RMS. Hence, there is a partial opposite trends in time-domain and frequency-domain variables in HP and MP groups. The sharpest decline in the values across all the selected variables was reported by the LP group. All the groups reported fluctuations in their values in between the time series in all the selected variables of the EMG activity of VL. The HP group reported higher values than the LP group in regard to variables, MDF and MNF, and the difference between their performance is further supported by the result of one-way ANOVA and LSD, because the comparison between LP and HP group in regard to variables MDF 30 (-462.724*), MDF 60 (-469.865*), MDF 120 (-476.379*), MNF 30 (-235.298*), MNF 60 (-207.839*), and MNF 120 (-244.681*) was found to be significant (P < 0.05). Similarly, HP group reported superior values to the MP group in regard to variables MDF and MNF and the results of one-way ANOVA and LSD revealed that the comparison between MP and HP group in regard to variables MDF 60 (-298.768*), MDF 120 (-477.819*), MNF 60 (-144.598*), and MNF 120 (-191.202*) was found to be significant (P < 0.05). However, the comparison between LP and MP group was only found significant in regard to MDF 30 (-311.382*). These results of LSD are presented in the [Table 5].
|Figure 1: Median frequency of vastus lateralis of all combined group (high-performance + mid-performance + low-performance group)|
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|Figure 2: Mean frequency of vastus lateralis of all combined group (high-performance + mid-performance + low-performance group)|
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|Figure 3: Integrated EMG of vastus lateralis of all combined group (high-performance + mid-performance + low-performance group)|
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|Figure 4: Root mean square of vastus lateralis of all combined group (highperformance + mid-performance + low-performance group)|
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|Table 5: Least significant differences applied on significant variables for post hoc analysis|
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| Discussion|| |
The key findings of the study were that with the progression of time, the values of both time- and frequency-domain variables followed a declining trend in all the groups except for MP group in the variables, namely MDF, MNF, and RMS. Significant effect of performance levels was observed not only between LP and HP group but also between MP and HP group, and this corroborates the findings of the conducted studies.,, The graphical presentation of the values of time- and frequency-domain variables in all the performance groups reported a declining pattern with the progression of time, and this could be attributed to the changes in the number of active motor units and shape of motor unit action potential. The initial effect of performance level was highlighted by the differences in the performance of HP and LP group in regard to their graphical presentation of time domain variables. As LP group reported the highest value at both IEMG and RMS at 30 s, then it also reported the sharpest decline in the values with the progression of time; however, HP group maintained a comparatively consistent value of the variables across the total time duration and this may be due to the differences in the muscle fibers recruitment and power of signal between LP and HP group with the progression of time., This may be attributed to the difference in the fiber composition and size between LP and HP group based on their training levels. The study design allowed to execute a better investigation of the effect of performance level on the EMG activity of VL muscle of dominant (right) leg. However, using only the male sample and recording EMG activity from only the VL muscle from the quadriceps muscle group may be identified as the limitations of the design. Overall, findings of the study would be useful for the evaluation and assessment of sportspersons as well as other populations. The findings will also contribute to improve the understanding of muscular fatigue by elaborating on its electrophysiological aspects.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]