Archives of Medicine and Health Sciences

: 2020  |  Volume : 8  |  Issue : 2  |  Page : 215--220

Neuromuscular efficiency of knee stability after anterior cruciate ligament injury in indian endurance athletes

Amrinder Singh, Jagannath Rout, Shweta Shenoy, Jaspal Singh Sandhu 
 MYAS-GNDU Department of Sports Sciences and Medicine, Guru Nanak Dev University, Amritsar, Punjab, India

Correspondence Address:
Dr. Amrinder Singh
MYAS.GNDU Department of Sports Sciences and Medicine, Guru Nanak Dev University, Amritsar, Punjab


Background and Aim: Knee muscle strength deficit occurs after anterior cruciate ligament (ACL) injury. For testing, isokinetic dynamometer was used to evaluate agonist and antagonist muscles strength, and it provides a certain magnitude of torque generated. Electromyography (EMG) is a method used in research, rehabilitation, ergonomics, and sport science to evaluate neuromuscular activation. The aim of the study was to compare the isokinetic strength and EMG changes of the flexor and extensor muscle of the knee in healthy athletes and athletes following ACL injury in endurance sports persons of India. Materials and Methods: This comparative study investigated 16 athletes with a history of unilateral ACL injury and 16 participants in the control group. Their isokinetic strength was checked using isokinetic dynamometer BIODEX System 4 PRO Dynamometer in conc/conc mode at 60,120 and 300°/s and electromyographic activity of the rectus femoris (RF), vastus medialis obliqus (VMO), vastus lateralis (VL), biceps femoris (BF), semitendinosus (ST) was checked by EMG in 0% and 10% of inclination of treadmill walking between control and ACL injured endurance athletes with the help of NORAXON DTS telemetric EMG. Results: Significant differences were observed in peak torque (PT), PT/body weight (BW), and hamstrings-to-quadriceps ratio at certain angular velocities; when observing muscle activity, there was significant difference in left and right side of RF, VL, and ST but comparing activity and groups, there were no significance. Conclusion: ACL group presented with lower PT and PT/BW; therefore, exhibiting poor isokinetic analysis results regarding the muscle performance in comparison to the control group, and there were no significant differences at 0% and 10% inclined treadmill walking between the control group and ACL injured group.

How to cite this article:
Singh A, Rout J, Shenoy S, Sandhu JS. Neuromuscular efficiency of knee stability after anterior cruciate ligament injury in indian endurance athletes.Arch Med Health Sci 2020;8:215-220

How to cite this URL:
Singh A, Rout J, Shenoy S, Sandhu JS. Neuromuscular efficiency of knee stability after anterior cruciate ligament injury in indian endurance athletes. Arch Med Health Sci [serial online] 2020 [cited 2021 Mar 2 ];8:215-220
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Full Text


The anterior cruciate ligament (ACL) is the primary passive restraint to anterior tibial translation on femur, and in frontal and transverse planes of the knee, it provides rotational stability because of its specific orientation.[1],[2],[3],[4] About 200,000 ACL injuries occur in US annually, and among them, 64% athletic knee injury is there in cutting and pivoting sports.[5],[6],[7] ACL injury leads to effusion of joint, alteration of kinematics and gait of knee, weakness of muscle, decreased functional performance, and in the long term, it causes tearing of menisci, chondral lesions, and posttraumatic early onset of osteoarthritis.[8],[9],[10],[11],[12],[13],[14],[15]

The prevalence of the injury depends on the level of participation, specific sports, sex differences and contributing factors, injury mechanism, and prevention programs.[16] Female injure their ACL 4–6 times more than their male counterparts.[17] The incidence of ACL injury in football is 0.063 events per 1.000 h of exposure time and higher during the competition than in training.[18],[19],[20] Sprains in field hockey are from 2%–37%, but ACL injury is infrequent comparing other professional sports and has high associated menisci and MCL injuries, and the majority of injuries are contact injuries.[21],[22],[23] In Kabaddi, 89.47% of athletes suffer from ACL injury in the Indian context.[24] Seventeen ACL injury per 100000 athletic exposures was found in NCAA players in basketball between 1989 and 2004. Between 2000 and 2004, 7.0% of ACL injury was found among Australian basketball players and 10.6% ACL injury among Canadian high-school basketball players in 2004.[25] In handball, the most serious injury is knee injuries that varies from 7% to 27% of which ACL injury holds up to 40%–50%, and these are due to deceleration and pivoting.[26],[27] Strength of an athlete is important as it is essential for optimal performance in sports and for the prevention of sports-related injuries.[28]

Strength is operationally defined as the maximal force a muscle or a group of muscles can generate at a specified velocity.[29] High muscular imbalance between hamstring and quadriceps is associated with knee and low-back injuries.[30] The alteration of strength and the hypotrophy of the flexor and ex-tensor muscles of the knee cause alter joint stability, leading athletes to injury.[31],[32] To measure strength now a days isokinetic dynamometers are used which resist applied force and control the speed of exercise at a preset velocity which show the amount of force applied in a joint range of motion (ROM).[33]

ACL injured person were prone to knee degeneration and early onset of osteoarthritis.[34],[35],[36] Inclined treadmill walking is helpful for the rehabilitation of ACL injured patients because it gives a functional activity that induces knee flexion and Quadriceps and Hamstring activity in stance phase. The increased knee flexion provides hamstrings a better mechanical advantage to restrict anterior tibial translation.[37] The experimental technique concerned with the development, recording and analysis of myoelectric signals is known as electromyography (EMG). Myoelectric signals are formed by physiological variations in the state of muscle fiber membranes.[38]

To the best of our knowledge, there is a lack of study of dynamometer and EMG on ACL injured endurance athletes in the Indian population. Hence, through this study, the aim was made to compare the strength changes between healthy and ACL injured endurance athletes by isokinetic dynamometry at 60,120,300 degree/second and to compare the activation of the rectus femoris (RF), vastus medialis obliqus (VMO), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (ST)muscle in plane (0%) and inclined (10%) treadmill walking by EMG method.

 Materials and Methods

Thirty two university level endurance athletes (mean age, 20.96 ± 1.95 years; height, 167 ± 8.9 cm; mass, 65.7 ± 12.04 kg) included and were assigned in two groups, Group A (n = 16; left ACL = 9, right ACL = 7) ACL injured group and Group B (n = 16) control group for this comparative study. Sample size was calculated by the biostatistician of the department. Both Indian male and female endurance athletes participated in interuniversity and above level having age between 16 and 25 years and unilateral ACL injury in between 3 and 12 months were included in this study for Group B and healthy endurance athletes aged between 16 and 25 were selected for Group A. All the athletes participating in the study were right dominant persons. The exclusion criteria included athletes having bilateral ACL injury, age below 16 and above 25 years, timing of injury <3 months and more than 12 months, any other associated lower extremity injuries, and athletes not belonging to India. The athletes were selected from the sports rehabilitation center of MYAS-GNDU Department of Sports Sciences and Medicine who were already diagnosed with chronic ACL injury to the knee (of Grade 1 and 2) by clinical examinations and observing the MRI reports. Athletes were in the training period and were undergoing in the rehabilitation phase. For the control group, they were selected from the field. The procedure, benefits and potential risks of study was explained to the participants before the test started and duly signed informed consent was taken. It was ensured that the participants were free of any musculoskeletal conditions or any neurological dysfunctions apart from ACL injury. This study was approved by the Institutional Ethics Committee of Guru Nanak Dev University, Amritsar, Punjab, India.

Procedure for isokinetic dynamometry

The isokinetic testing was performed using the Biodex System 4 pro Dynamometer (Biodex Medical System Inc., Shirley, NY) in the concentric/concentric mode at 60, 120 and 300°/s, for knee flexion and extension [Figure 1]. Participants were instructed not to perform any physical activities on the day of testing. Warm-up consisted of stationary cycling with no resistance and stretching of the Quadriceps and Hamstring muscles. Participants were then positioned on the positioning chair, and stabilized by belts around their trunk, pelvis, and thighs. Hip flexion was set at 85°, and the dynamometer axis was aligned with the lateral femoral epicondyle. The ankle pad was positioned just above the medial malleolus. Then calibration and gravity correction was done. ROM was limited to between 90° of flexion and 0° of extension. Extension ROM for each participant was defined in accordance with their individual limits. Three practice repetitions at each velocity were performed to accommodate with testing procedures.[39] Isokinetic testing consisted of one set of five repetitions at each velocity with a rest time of 2 min between sets. The data were obtained by the investigator along with one lady therapist. Verbal encouragement was given for the production of maximal effort of the athlete.{Figure 1}

Procedure for electromyography

For EMG analysis of the lower extremity athletes walked on the treadmill in 0% and 10% of inclination. Dependent variable was level of EMG activity for each muscle and independent variable was Level of treadmill inclination (0 and 10%). To record muscle activity, the skin for each electrode site was shaved and cleaned. Thereafter, warm up was done on stationary bicycle. A Noraxon DTS (Noraxon, USA) 16 channel telemetric EMG was attached bilaterally at the RF, VMO, VL, BF, ST, respectively [Figure 2]. Placements were secured by adhesive tapes. After the warm up, particiants were allowed to perform the dynamic walking and were allowed adequate trials for familiarization. Two days of familiarization session was conducted to understand the procedure and equipment used. Participants walked on Zebris FDM-T [Figure 3] set to 60 m/min first at 0% and then 10% of treadmill inclination.[40] Walking trial was performed twice for each condition with each trial lasting 1 min once for plane and another for inclined walking. Activities were repeated three times (30 s each) for each subject with 1 min rest between repetitions. Data were captured and processed in the Noraxon MR 3.8 software (Noraxon, USA). Mean and max EMG were determined during the study. Root mean square was done with 150 ms windowing. Normalization was done by dividing activity EMG to maximum value.{Figure 2}{Figure 3}

Data analysis

The results obtained as mean ± standard deviation. For comparisons of the anthropometric and isokinetic variables such as, peak torque (PT), PT/body weight (BW), and the hamstrings-to-quadriceps (H/Q) ratio; Student's t-test was used after verification of the equality of variance errors (Levene test). In EMG analysis, multivariate analysis was done to compare the side, activity, and group effect. The level of significance was 0.05 and all analyses were performed with SPSS version 20.0 (Armonk, NY: IBM Corp).


Demographic data

Demographic data are presented in [Table 1] of the control group and ACL injured group.{Table 1}

Isokinetic performance

Statistically significant differences were found in PT (both right and left and in flexion and extension) at 60°/s, 120°/s ; in 300°/s there is no significant difference found in left flexion PT, but all other variables are significant between the control group and ACL injured group [Table 2]. PT/BW values in extension (both right and left) at 60°/s, 120°/s, and 300°/s were significant between the control group and ACL group. PT/BW values in flexion is significant in all speeds except left side at 300°/s. H/Q ratio is significant in left leg at 60°/s and in both legs at 120°/s. The other variables were not statistically significantly different. In the Table 2, the control group shows the data of the healthy athletes, but the ACL injured group shows both data of the left side ACL injured and right side ACL injured athletes. All the athletes participating in the study were right dominant persons. In this study, the right side data of the healthy athlete were compared with the right side ACL injured athletes and left side data of the healthy athletes was compared to the left side ACL injured athletes.{Table 2}

Electromyography performance

[Table 3] illustrates tabulated representation of normalized values of EMG of RF muscle. When comparing muscle activity of RRF to LRF, there was significant difference (F = 26.120, P < 0.001). However, when comparing groups (i.e., ACL injured group to control groups), no significant difference was found (F = 0.503, P = 0.481). Similarly, in comparison of activity (i.e., plane to inclined treadmill walking), no significant difference was observed (F = 0.803, P = 0.374).{Table 3}

[Table 4] illustrates tabulated representation of normalized values of EMG of VL muscle. When comparing muscle activity of RVL to LVL, there was significant difference (F = 5.631, P = 0.021). However, when comparing groups (i.e., ACL injured group to control groups), no significant difference was found (F = 0.125, P = 0.725). Similarly, in comparison of activity (i.e., plane to inclined treadmill walking), no significant difference was observed (F = 0.000, P = 0.991).{Table 4}

[Table 5] illustrates tabulated representation of normalized values of EMG of semitendinosus muscle. When comparing muscle activity of Right Semitendinosus (RST) to Left Semitendinosus (LST), there was statistically significant difference (F = 10.290, P = 0.002). However, when comparing groups (i.e., ACL injured group to control groups), no significant difference was found (F = 0.777, P = 0.382). Similarly, in comparison of activity (i.e., plane to inclined treadmill walking), no significant difference was observed (F = 0.309, P = 0.580).{Table 5}


The aim of the present study was to compare the isokinetic strength changes between healthy and ACL injured endurance athletes of India at 60°/s, 120°/s, and 300°/s. Another objective of this study was to observe the EMG changes of the RF, VMO, VL, and BF, Semitendinosus muscles in treadmill walking at 0% and 10% inclination between healthy and ACL injured endurance athletes.

Our study evaluated isokinetic variables of post-ACL injury subjects compared to controls; the results indicate that extension PT, PT/BW was lower in the ACL injury group at 60, 120, and 300°/s. The flexion PT, PT/BW of ACL injured when compared with healthy endurance athletes at 60 and 120°/s, it showed a statistically significant difference for both flexion and extensor muscles (P < 0.05). However, in 300°/s, the PT and PT/BW is slightly lowered but not significant. This deficit is in accordance with a systematic review by Petersen et al. in which strength deficits is there in the both the extensors of the knee and the flexors of knee.[41] The authors recommended isokinetic examination of the knee as one criteria to decide if an athlete should be allowed to return to unrestricted sporting activities. Hart et al. also found persistent quadriceps weakness in post-ACL injury participants.[42] Cvjetkovic et al. found that there were statistically significant differences between groups in all evaluated parameters (PT/BW, H/Q ratio) except of the mean value of PT/BW of the quadriceps et velocity of 60°/s (P > 0.05).[43]

In our study, result showed that H/Q ratio is significant at 60°/s for left ACL injured limb when compared to healthy athletes. At 120°/s, there is significant difference in both right and left limb between ACL injured athletes and healthy athletes for H/Q ratio. At 300°/s, there is no significant difference between the two groups. At lower velocities, the HQR is low and at higher velocities it increases. When velocity increases, it leads to increase in forward momentum of tibia to an extent where hamstring recruitment is more to limit extension rotation and anterior tibial translation of knee. Hence, when angular velocities increase, there is increased HQR present.[44],[45] In all speeds, the HQR value is higher in ACL injured athletes than healthy athletes which is in accordance with the results found by Kannus; who found significant higher HQR in involved compared with the sound limb at the higher testing speed (180°/s).[44] According to the literature for low velocities, the normal HQR was about 0.60, and for higher velocities, it was >1.[46] If the HQ ratio is higher, the hamstrings has an increased functional capacity to provide stability to the knee.[47]

The present study shows the dynamic EMG of RF, VMO, VL, BF, and ST muscles, of which averaged mean amplitude of all periods and averaged maximum of all periods in μV (microvolt) bilaterally was taken. Our study found the activity of RF, VL, and ST to be significant when the left side was compared to right whereas other muscles that are VMO and BF did not showed significant difference when left side was compared to right. When groups (control and ACL injured) and activities (0% and10% treadmill inclination) were compared, there was no significant difference between both the groups. The results of our study agrees with the findings by Cicotti et al. who showed no changes in EMG activity for most muscles when progressing from level to ramp walking when observing in ACL deficient and reconstructed patients.[48] However, the data disagree with those of Lange et al. who showed there was significant increase in vastus medialis oblique, VL, and BF with graded treadmill walking.[49]


The finding of the present study indicated that the ACL injured group presented with lower PT and PT/BW, therefore exhibiting poor isokinetic strength analysis results regarding the muscle performance in comparison to the control group. There were significant differences in H/Q ratio in right and left limb at 120°/s of angular velocity, only in the left side between two groups at 60°/s of angular velocity and no significance at 300°/s of angular velocity.

In this study, we have found no significant differences in muscle activity during level and inclined walking on treadmill for ACL injured endurance athletes compared with control participants, but for muscles such as RF, VL, and semitendinosus, there was a significant difference between the right and left side.[50],[51] The study will help in adapting a proper rehabilitation programme for knee joint so that the deficits in the muscle strength can be regained. It will help endurance sports players, physical therapists, and sports biomechanist to understand and promote better strategies for improvement in muscle performance around knee.

Financial support and sponsorship

The study was conducted at MYAS-GNDU Department of Sports Sciences and Medicine, Guru Nanak Dev University, Amritsar, Punjab, India. This center is funded by the Ministry of Youth Affairs and Sports Government of India.

Conflicts of interest

There are no conflicts of interest.


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