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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 6  |  Issue : 1  |  Page : 49-55

Effect of performance level on the longitudinal electromyographic activity of vastus medialis and vastus lateralis muscles after induced extreme fatigue with a workload of 30 repetition maximum


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 Submission10-Apr-2020
Date of Decision05-Jul-2020
Date of Acceptance24-Jul-2020
Date of Web Publication08-Apr-2021

Correspondence Address:
Dr. Dhananjoy Shaw
Indira Gandhi Institute of Physical Education and Sports Sciences, University of Delhi, B-Block, Vikaspuri, New Delhi - 110 018
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/bjhs.bjhs_27_20

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  Abstract 


CONTEXT: The study of longitudinal electromyographic (EMG) activity of the muscles under extreme fatigue conditions has been an inadequately explored area in muscle fatigue research.
AIMS: The aim of this study was to assess the effect of performance level on the longitudinal EMG activity of the vastus medialis (VM) and vastus lateralis (VL) after induced extreme fatigue with a workload of 30 repetition maximum (RM).
DESIGN: This was a cross-sectional study.
MATERIALS AND METHODS: Eighteen healthy intercollegiate level male sportspersons (age: 19.84 ± 2.1 years, height: 171.38 ± 8.48 cm, and weight: 69.72 ± 13.85 kg) were randomly selected as participants. As fatigue protocol, 30 repetitions of leg extension exercise with 30 RM load were performed. Isometric contraction of VM and VL muscles at an angle of 0°–10° with 30 RM load was performed until failure as the postfatigue or extreme fatigue protocol. Both protocols were performed in Cybex VR1 leg curl exercise device. EMG activity was recorded from VL and VM during the postfatigue protocol. 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 participants, nine participants were enlisted and equally divided into high-performance (HP) group, mid-performance (MP) group, and low-performance (LP) group. The raw EMG signals were quantified through MATLAB to derive root mean square (RMS) and median frequency (MDF).
STATISTICAL ANALYSIS USED: One-way ANOVA and least significant difference (at P < 0.05) were used to assess the influence of performance level, and independent two-tailed t-test (at P < 0.05) was applied to compare the EMG activities of VM and VL in regard to performance level.
RESULTS: All the groups displayed a constant linear trend in regard to MDF and RMS except for the HP group in the VL and LP groups in VM. The EMG activities of all the groups were not significantly different from each other under extreme fatigue. However, muscle activation of VM and VL was significantly different from each other in the MP and LP groups.
CONCLUSIONS: Findings are useful for further understanding muscle fatigue.

Keywords: Vastus lateralis, vastus medialis, relative impulse, root mean square, median frequency, extreme fatigue


How to cite this article:
Shaw D, Singh D, Kaur M, Ahlawat UK, Bhatia D. Effect of performance level on the longitudinal electromyographic activity of vastus medialis and vastus lateralis muscles after induced extreme fatigue with a workload of 30 repetition maximum. BLDE Univ J Health Sci 2021;6:49-55

How to cite this URL:
Shaw D, Singh D, Kaur M, Ahlawat UK, Bhatia D. Effect of performance level on the longitudinal electromyographic activity of vastus medialis and vastus lateralis muscles after induced extreme fatigue with a workload of 30 repetition maximum. BLDE Univ J Health Sci [serial online] 2021 [cited 2021 Dec 9];6:49-55. Available from: https://www.bldeujournalhs.in/text.asp?2021/6/1/49/313351



Muscle fatigue is a state characterized by inability of a muscle to generate the required amount of force during a sustained or repeated contraction.[1] Some of the extensively studied muscles in the domain of muscle fatigue researches are the vastus medialis (VM) and vastus lateralis (VL) muscles[2] because the coordination between their contractions is a major determinant of patellar tracking and other knee joint-related dysfunctions,[3],[4] and they have major role in the sports activity and in overall functional capacity.[2] A commonly utilized tool to accurately assess muscle fatigue and its effects on the muscle is surface electromyography (sEMG).[2],[5],[6] Numerous areas related to muscle fatigue and its effect on the functioning capacity of VM and VL have been extensively explored through the use of sEMG.[7],[8],[9],[10],[11],[12],[13] A prominently explored area under the researches on muscle fatigue is the investigation of the longitudinal electromyographic (EMG) activity of the knee extensor muscles (especially VM and VL muscles) during a physical activity or exercise[14] or voluntary isometric contraction[10] till fatigued and exhaustion. However, an inadequately explored area is the investigation of longitudinal EMG activity of the knee extensor muscles during the performance of a physical activity or exercise in fatigued condition or postfatigue or extreme fatigue condition. The conducted studies on extreme fatigue conditions involve the performance of two successive tasks/protocols wherein the first protocol is called fatigue protocol and it seeks to induce muscle fatigue in the VM and VL muscles, and immediately after the fatigue protocol, the individual performs the second protocol while being in fatigued condition, also known as postfatigue task.[15] EMG activity of the concerned muscle is recorded in the postfatigue task, and it is also referred to as recording EMG activity in an extreme fatigue condition. However, several limitations have been identified in these studies. These studies have reported statistically insignificant and inconclusive findings,[15],[9] and to encounter this, Murdock and Hubley-Kozey have recommended to use a more demanding task requiring greater muscle activation as the postfatigue task.[15] Another major limitation associated with these studies is that they had disregarded the effect of performance level of the individuals on the longitudinal EMG activity of VM and VL muscles in the postfatigue task. This questions the applicability of their findings to the field of exercise and training because the performance level has been demonstrated to impart a significant effect on the neuromuscular fatigue responses and muscle activation levels in VM and VL.[7],[8]

The proposed study has sought to efface the above stated problems by adopting the necessary measures and recommendations with the purpose to comprehensively assess the effects of performance level on the longitudinal EMG activity of VM and VL with the progression of duration of the postfatigue task while also investigating the differences between the EMG activity of VM and VL muscles in relation to performance level.


  Materials and Methods Top


Healthy intercollegiate level male sportspersons (n = 18, age = 19.84 ± 2.1 years, height = 171.38 ± 8.48 cm, and weight = 69.72 ± 13.85 kg) were included as the participants of the study. The inclusion criterion was that the individuals 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 individuals must not have any medical conditions/contractures/deformities in the joints or suffer from skin condition which might impede the fixation of the electrodes on the body surface. The participants were engaged in regular training of their respective games/sports, and their activity level was at least of intercollegiate level of University of Delhi which reflects more than the requirements to fulfill the physical activity recommendations of American College of Sports Medicine and American Heart Association[16] because they were at least undergoing a minimum of 150 min of moderate-intensity aerobic physical activity per week. Before participation, each participant was explained about the purpose and protocol to be followed for the study and they were asked to undergo few predata collection trials in order to make them familiar with the study along with determining their 30 repetition maximum (RM) for the exercise through trial and error method. The average 30 RM value of the participants was 28.47 (±7.56) kg. Before initiating the tests, written informed consent was obtained from each participant to fulfill the ethical requirements. As the study was noninvasive in nature and appropriate written informed consent was obtained from all the participants, thus, the relevant ethical requirement was met. Cybex VR1 leg curl exercise device (Cybex, Division of Lumex Inc., Ronkonkoma, USA) was used for performing fatigue protocol and postfatigue or extreme fatigue protocol. EMG data were acquired using a 4-Channel Wireless EMG BIOPAC Inc. MP150 system (CMRR: 110 dB at 50/60 Hz, maximum sampling rate: 200 K samples/s and gain: 5–50,000, input impedance: 2 MΩ). 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 participant's selected muscle following a standard protocol[17] to acquire EMG data. The interelectrode distance was 20 mm, center to center. After the participant preparation was done, the participant was appropriately seated on the Cybex VR1 leg curl exercise device. For the fatigue protocol or the protocol to induce fatigue, each participant 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. 30 RM load is the load (in kg) with which 30 repetitions of a particular exercise can be performed, and it was opted for the study as 25–30 is considered as the appropriate load for developing and measuring muscular strength and endurance in athletes.[18] Immediately following the last repetition in fatigue protocol, the participants performed isometric contraction of VM and VL muscles at an angle of 0° to 10° with their 30 RM load in Cybex VR1 leg extension exercise device until failure as the postfatigue or extreme fatigue protocol. EMG activity was recorded simultaneously from the VL muscle and VM muscle of the right lower limb of all the participants during the performance of the postfatigue protocol to investigate the longitudinal EMG activity in the extreme fatigue condition. Sampling rate during the acquisition was set to 2000 Hz as per the Nyquist criteria. The collected data were stored using AcqKnowledge 4.3 software (BIOPAC Inc., USA). As the mechanism of muscle fatigue depends on the duration and intensity of the activity/exercise,[19] thus, to account for both intensity and duration of exercises, a new criterion called relative impulse (RI) was developed and it was calculated for each participant. RI is an equation formulated from the equation of impulse from physics. However, in RI, the 30 RM was used as an equivalent of force applied and the duration of postfatigue protocol was adopted as the duration of force application. To account for the differences in body mass of the participants and its effect on 30 RM value, the whole equation is divided by the body weight. The relative impulse of each participant was calculated from their 30 RM, duration of postfatigue, or extreme fatigue protocol and the body weight using equation 1.



Based on the magnitude of RI, nine participants were enlisted and they were divided into high-performance (HP) group (n = 3), mid-performance (MP) group (n = 3), and low-performance (LP) group (n = 3). The top three participants with greater relative impulse (RI = 41.96 ± 13.72) were included in the HP group, the bottom three participants were included in the LP group, and the participant with the median value (RI = 19.42) and two participants closer to the median value were included in the MP group (n = 3). The relative impulse value of each group is stated in [Table 1].
Table 1: Relative impulse value of each group

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The raw EMG data of right VM and VL muscles recorded from the total duration of postfatigue protocol were segmented at a 30 seconds (s) time interval. Thus, the raw EMG data of right VM and VL were segmented into 30, 60, and 90 s for each participant of the HP group. The raw EMG data of right VM and VL of each participant of MP were segmented into 30 and 60 s. The raw EMG data of right VM and VL of each participant belonging to the LP group were segmented into 30 and 60 s. Different data segmentation of EMG data for each group was based on the duration of the postfatigue protocol of the participants in the group. All these were done to better understand the influence of performance level of a participant on his longitudinal EMG activity of muscle during fatigued condition. The raw EMG signals acquired from the participants 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. Cascaded low-pass (20 Hz) and high-pass (450 Hz) filters were subsequently applied in order to remove other noise sources from the signal. Selected time domain variable and frequency domain variable were extracted from the filtered signal. Thus, selected variables, namely root mean square (RMS) and median frequency (MDF), were derived and calculated, respectively, for each participant belonging to each group. RMS is an established index of muscle recruitment[20] and MDF is recognized as the index of muscle fatigue,[14],[21] and together these provide information regarding the level of muscle activation and the development of muscle fatigue during an exercise or physical activity.[13] Thus, both RMS and MDF are frequently used for determining the changes associated with fatigue in muscle.[7] [Table 2] contains a list of variables used in the study.
Table 2: Selected variables to study the electromyographic activity of selected knee extensor muscles

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The longitudinal EMG pattern for the selected muscles with respect to the progression of time in the duration of postfatigue task for each performance group was determined by plotting the mean values of selected time and frequency domain variable of each group on a line graph with respect to the segmented time interval for the group. One-way ANOVA was carried out to determine whether the influence of performance level exists and it is statistically significant (P < 0.05) during the postfatigue conditions in VM and VL muscles of the participants. The selected variables to carry out statistical analysis are presented in [Table 3].
Table 3: Selected variables for the statistical analysis

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MDF 90 and RMS 90 were excluded from one-way ANOVA to facilitate comparison among the performance groups as only the HP group reported values for them. After determining the statistical significance among the groups, the least significant difference for the statistically significant variables was conducted as post hoc test. To compare the EMG activities of the selected knee extensor muscles in regard to performance level, independent two-tailed t-test was applied on each selected variable of VM and VL of each participant while considering his performance level. The level of significant was set to P < 0.05 for all tests. All the statistical analysis was carried out using IBM SPSS Statistics Software (IBM, Armonk, New York, United States).


  Results Top


The mean and standard deviation values of all the selected variables derived from the raw EMG data of VM muscle and VL muscle are presented in [Table 4.1],[Table 4.2],[Table 4.3]. According to the [Figure 1],[Figure 2],[Figure 3],[Figure 4], all the three groups displayed a constant liner trend at the selected variables, namely MDF and RMS, in both VM and VL except for the HP group in VL muscle as it demonstrated a slight rising trend in both MDF and RMS and the LP group in VM muscle as it displayed a slight declining trend in both MDF and RMS. According to [Table 4.1],[Table 4.2],[Table 4.3], the HP group reported the highest values of the MDF and RMS at all the segmented time intervals and VM muscle reported greater values of MDF and RMS than VL muscle in all the performance groups. However, the result of one-way ANOVA (presented in [Table 6] and [Table 7]) reveals that the performance level does not impart a statistically significant influence on the longitudinal EMG activity of the VM and VL in the extreme fatigue condition. According to [Table 5.1],[Table 5.2],[Table 5.3], the longitudinal EMG activity in regard to the muscle activation of the VM and VL muscles differs in different performance levels because the comparison between the VM and VL muscles at RMS 30 and RMS 60 in the MP and LP groups was found to be significant.
Figure 1: Median frequency of vastus medialis of all combined group (HP + MP + LP group)

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Figure 2: Root mean square of vastus medialis of all combined group (HP + MP + LP group)

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Figure 3: Median frequency of vastus lateralis of all combined group (HP + MP + LP group)

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Figure 4: Root mean square of vastus lateralis of all combined group (HP + MP + LP group)

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Table 6: Comparison among the performance groups (one-way ANOVA) in regard to the selected electromyographic variables of vastus medialis

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Table 7: Comparison among the performance groups (one-way ANOVA) in regard to the selected electromyographic variables of vastus lateralis

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  Discussion Top


The key findings of the study were that the values of the selected frequency domain variable (MDF) and time domain variable (RMS) followed a constant linear trend with the progression of time in all the groups in both VL and VM muscles except for the LP group in regard to the VM and HP groups in regard to VL. This finding is partially contrary to the results reported by Murdock and Hubley-Kozey(2012) as their study reported a decline in MDF in both VL and VM muscles, and the partial agreement found between the LP groups and their result can be attributed to the similarity of the fitness level of the participants in the LP group and the sedentary classified participant used by them.[15] Similarly, this finding is partially contrary to the result reported by Camata et al. and Maïsetti et al. as they reported a rise in the RMS in both VM and VL with the progression of the time or till the point of exhaustion and this disagreement could be attributed to the fact that fatigue protocol would have caused the maximum neural activation of the selected knee extensor muscles, and thus, no further increase in RMS was reported in the postfatigue task.[2],[13] However, the partial agreement found between the HP groups in RMS at VL muscle, and the findings of Camata et al. and Maïsetti et al. could be due to the inability of the fatigue protocol to cause maximum neural activation in the VL muscle of the participants in the HP group. Another major finding of the study is that the HP group reported the highest values of MDF in both VM and VL muscles, but the comparisons among the performance groups with regard to both VM and VL, using one-way ANOVA, were not found to be significant, and this implies that even though the HP group demonstrates to have absolute greater resistance to muscle fatigue,[2] relatively the rate of muscle fatigue and the rate of slowing of their muscle fiber conduction velocity, contractile speed, and increase in the accumulation of metabolites are same in the extreme fatigue conditions among the performance groups.[2],[22],[23] Similarly, the HP group also reported the highest value in RMS as well, but the comparison between the performance groups at both VM and VL using one-way ANOVA was not found significant, and this implies that relatively the rate of muscle activation is the same in the extreme fatigue conditions among the performance groups.[13] Another major finding of the present study was that the comparison between the longitudinal EMG activity of the VM and VL groups was found not significant in MDF in all the groups and this implies that VM and VL muscles have a similar muscle fatigue rate in all the performance levels in extreme fatigue condition and this is consistent with the result reported by Grabiner,[9] but it is contrary to the result reported by Pincivero et al.,[24] Camata et al.,[13] and Pincivero et al.[14] However, the comparison between the longitudinal EMG activity of the VM and VL groups was found significant in regard to RMS in the MP and LP groups but not in the HP group, and this indicates towards the presence of higher EMG asymmetricity between VM and VL muscles in the MP and LP groups than the EMG asymmetricity between VM and VL muscles in the HP group in extreme fatigue condition. This finding is consistent with the result reported by Nara et al.[8] The study design allowed to execute a better investigation of the effect of performance level on the longitudinal EMG activity of VM and VL muscles under the extreme fatigue conditions. However, the use of only male sample and lack of control over psychological factors such as motivation and discomfort that impacts muscle fatigue[25] can be considered as the limitation of the study. Overall, it can be concluded that in the extreme fatigue conditions, the performance level has no significant effect on the longitudinal EMG activity of VM and VL at the intracomparison level with the progression of time. However, the performance level does have a significant impact on the muscle activation at VM and VL at the intermuscular comparison level in the extreme fatigue conditions. The findings of the study would be useful for evaluation and assessment of sportspersons as well as other populations. The findings will also contribute in improving the understanding of muscular fatigue by elaborating on its electrophysiological aspects.


  Conclusions Top


The following conclusions can be drawn from the study:

  1. The longitudinal EMG activity of VM and VL muscles across all the performance groups followed a constant linear trend with the progression of time under the extreme fatigue conditions
  2. The performance level had no significant effects on the longitudinal EMG activity of VM and VL during the extreme fatigue conditions
  3. The muscle activation of VM and VL was significantly different from each other in the MP and LP groups during the extreme fatigue conditions.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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