A Comparative Study Of The Impact Of Muscle Energy Technique And Eccentric Training On Popliteal Angle: Hamstring Flexibility In Indian Collegiate Males

Introduction

Sports coaches, performers and scientists are constantly in search of new means to enhance sports performance and gain a competitive edge. Flexibility is related to physical fitness and is often evaluated from the joint range of motion [3, 9, 16]. It is defined as “performance of smooth and extensive movement of body joints” [6, 23]. Reports on the significance of flexibility have focused on the contribution to preventing injuries and improving sports performance [16, 27]. For example, in hurdles an extensive joint range of motion i.e. flexibility is required in the hip joint [27].

Flexibility is considered an essential element of normal biomechanical functioning in sport [11, 12]. The literature reports a number of associated benefits of flexibility including improved athletic performance, reduced injury risk, prevention or reduction of post-exercise soreness and improved co-ordination [19]. Some studies have shown that decreased hamstring flexibility is a risk factor for development of patella tendinopathy and patellofemoral pain, hamstring strain injury [10, 13, 20, 25]. Hamstring muscle injuries are one of the most common musculotendinous injuries in the lower extremity [5]. They occur primarily during high speed or high intensity exercises and have a high rate of recurrence [17, 22]. Worrel et al stated that a “lack of hamstring flexibility was the single most important characteristics of hamstring injuries in athletes" [24].

Muscle energy technique is a manual technique developed by osteopaths that is now used in many different manual therapy professions [1, 4]. Such approach which targets the soft tissues primarily (although it makes a major contribution towards joint mobilization) has been termed as MET and this is also known as active muscular relaxation technique. It is claimed to be effective for a variety of purposes including lengthening shortened muscles, as a lymphatic or venous pump to aid the drainage of fluid or blood and increase the range of motion [1, 14, 15].

Eccentric contractions are a type of training that allows the muscle to elongate naturally and in its relaxed state this elongation is achieved by having the subjects eccentrically contract the antagonist muscle to move the joint through the full available range in slow controlled manner to stretch the agonist muscle group [21]. It is a better training strategy to improve flexibility and is also able to increase strength and protect against muscle damage [2, 26].

This present study tried to control all the risk factors which are due to inappropriate flexibility, and are related to performance, both physical and psychological. Thus we could observe solely the effects of these techniques on improvement, i.e. hamstring flexibility. The aim of the study was to investigate and compare the influence of Muscle Energy Technique (MET) [14] and Eccentric Training (ECC) on popliteal angle, i.e. hamstring flexibility in Indian collegiate males.

Matherials and methods

Samples

20 Indian collegiate males, aged 18-25 years, having tightness in hamstring muscles (inability to achieve greater than 160° of knee extension with the hip at 90° of flexion) [3], were included in the study.

Those subjects who had acute or chronic low back pain, hamstring injury, inhibition to actively extend the knee fully in sitting position, visual acute swelling in the region of hamstring muscles, or were already involved in any exercise programs for lower extremity were omitted from the study.

The written informed consent was obtained from all the subjects. The study was approved by Institutional Medical Ethics Committee of Jamia Hamdard University, Delhi, India.

Experimental Procedure

The study was experimental with different subject design. The subjects were randomly assigned into two equal groups: Muscle Energy Technique group & Eccentric Training group. Each subject was assessed for hamstring tightness by measuring the popliteal angle. The testing was taken over 5 days' period with each subject in both groups, A and B, receiving one treatment session in a day for consecutive 5 days and the follow-up measurement on the 8th day. The study was conducted at Hamdard University, N.D., India. The subjects were tested approximately at the same time of each day.

Outcome Variable

Popliteal Angle / Active Knee Extension Test
Pre-, post- and follow-up measurement data on the popliteal angle were collected from both groups.

The subjects were assessed for hamstring tightness using the Active Knee Extension test (Popliteal angle). The subject was in supine position with the hip flexed at 90° and the knee flexed. A cross bar was used to maintain the proper position of the hip and the thigh. The testing was done on the right lower extremity and subsequently, the left lower extremity and the pelvis were strapped down to the table for stabilization and control over accessory movements. Landmarks used to measure the hip and knee range of motion were the greater trochanter, the lateral condyle of the femur and the lateral malleolus, which were marked by a permanent skin marker. The fulcrum of the goniometer was centered over the lateral condyle of the femur with the proximal arm secured along the femur using the greater trochanter as a reference. The distal arm was aligned with the lower leg using the lateral malleolus as a reference. The hip and knee of the extremity being tested were placed into 90° flexion with the anterior aspect of the thigh in contact with the horizontal cross bar frame at all times to maintain the hip in 90° flexion. The subject was then asked to extend the right lower extremity as far as possible until a mild stretch sensation was felt. A full circle goniometer was then used to measure the angle of knee flexion. Three repetitions were performed and an average of the three was taken as the final reading for Popliteal Angle [21].

Training Program
Muscle Energy Technique

The Muscle Energy Technique (MET) is a manual technique developed by osteopaths, which is now used in many different manual therapy professions. It is claimed to be effective for a variety of purposes, including lengthening a shortened or contractured muscle and increasing the joint range of motion of the restricted joint [14, 18]. It can be used in older patients who have restricted motion from arthritis or who have brittle osteoporotic bones. MET was applied to the experimental group B. The subject’s knee was extended to the position where he first reported any hamstring discomfort, and moderate isometric contraction (approx 75% of maximal) of the hamstring muscle was then elicited for a period of five seconds. After a period of three seconds of relaxation, the technique was repeated three times (for a total of four contractions) [1].

Eccentric Training

The Eccentric Training group performed a full range of motion eccentric training for the hamstring muscles. The subject lay supine with the leg fully extended. A 3ft (0.91-m) long piece of black Theraband was wrapped around the heel and the subject held the ends of the Theraband in each hand. The subject was instructed to keep the opposite knee locked in full extension and the hip in neutral internal and external rotation throughout the entire activity.

The subject was then instructed to bring the test hip into full hip flexion by pulling on the Theraband attached with the foot and both arms, making sure that the knee remained locked in full extension at all times. Full hip flexion was defined as the position of hip flexion at which a gentle stretch was felt by the subject. As the subject pulled the hip into full flexion with the arms, he was instructed to simultaneously resist the hip flexion by eccentrically contracting the hamstring muscle during the entire range of hip flexion. The subject was instructed to provide activity of the hamstring muscles, so that the entire hip flexion took approximately 5 seconds to complete. Once achieved, this flexed hip position was held for 5 seconds and then the extremity was lowered to the ground (hip extension) by the subject’s arms.

This procedure was repeated 6 times with no rest between repetitions, thereby providing a total 30 seconds of stretching at the end range [21].

Statistical Analysis

The data were statistically analyzed using the Statistical Package for Social Science (SPSS)/15.0. (Copyright © SPSS Inc.). Statistical tests used in the present study were the independent-t-test and the repeated measure ANOVA test.

Results And Discussion

The mean physical parameters of the subjects are shown in Table 1. There was no significant difference in the baseline Popliteal angle values of the subjects when compared across the 2 groups, as shown in Table 2. There was however a significant difference in the post 5 days' range of motion across both groups, as shown in Table 2. On the post intervention and the carryover/follow-up, the mean values showed significant difference (p<0.05).

Table 1. Physical characteristics of the subjects in each group.

The comparison of pre-, post- and follow-up results of the outcome (Popliteal Angle) shows that it was significant in both experimental groups (p<0.01). Groups A and B showed significant difference at post intervention with p value of 0.018 (lesser than 0.05). In the follow-up, Groups A and B showed significant difference with p value of 0.014 (lesser than 0.05).

Table 2. The baseline, post-, and follow-up Popliteal Angle ranges of the subjects (N=20).

In both groups, the range of Popliteal Angle (Degree) shows that the mean range of motion during the post-test is higher than that during the pre-test (p<0.001). In group A, follow-up values were lower than post-test values (p< 0.20) but higher than pre-test values after application of Muscle Energy Technique (p<0.02). In group B, follow-up values were lower than post-test values (p<0.008) but less than pre-test values after application of Eccentric Training (p<0.733).

Figure 1. Between-group comparison ( Pre-, Post- to Follow-up).

Figure 2. Within-group comparison.

Discussion

The review of the existing literature regarding the role of different techniques in improving flexibility reveals a confusing picture so as to which technique, Eccentric training/contraction or MET, is best for the purpose. Therefore the current study was undertaken to investigate and compare the influence of Muscle Energy Technique (MET) and Eccentric Training (ECC) on the popliteal angle, i.e. hamstrings flexibility in Indian collegiate males and to determine which is better in the long run. For the purpose of this, a pre-test, a post-test, and a follow-up (experimental study) were carried out. The hamstring was the muscle of choice since it is the muscle that is most prone to injuries during sporting activities and there are also well documented, reliable and valid methods of testing flexibility of hamstring muscles, such as the Popliteal Angle/ Active Knee Extension test.

A comparison of the pre-test and the post-test values of the Popliteal Angle for the groups showed that there was a significant improvement in both groups. Thus it may be said that these techniques are effective individually in improving flexibility of hamstrings.

MET in the present study is comparable to that seen in earlier research. Ballantyne et al. [1] identified 30 seconds as the optimal duration for an effective stretch; MET, which can maintain muscle elongation for this duration, may produce an increase in muscle length by a combination of creep and plastic change in the connective tissue [7]. Flexibility increased after MET more, whereas Eccentric Training showed less improvement in hamstring flexibility. The mechanism behind the gained flexibility in muscle after MET may be due to biomechanical or neuro-physiological changes or an increase in tolerance to stretch. However, the mechanism behind the increased flexibility with eccentric hamstring activity through the full range of motion is unclear [21].

Skeletal muscle has a large adaptation potential induced by eccentric contraction and morphological changes are related to the addition of sarcomeres in series [2]. Repeated (eccentric) contraction results in disruption and membrane damage, which in effect leads to uncontrolled Ca++ movements and the development of localized contracture [8]; this could be a cause of less improvement of muscle flexibility in Eccentric Training than in Muscle Energy Technique.

At the time of the follow-up, the values of the Popliteal angle were higher than the pre-test values but showed a decrease from the post-test values. Thus an analysis of the muscle flexibility after 72 hours of the end of training did not reveal a significant maintenance of flexibility. The deterioration from the post-test values at the time of follow-up can be attributed to the fact that there was no maintenance program that was being followed during that period, and the subjects were not undergoing any active or passive stretching regimes during those 72 hours.

Conclusions

It can be concluded that the Muscle Energy Technique and Eccentric Training program improve the Popliteal angle, i.e. hamstring flexibility, and that they will enhance the athletic performance. Muscle Energy Technique resulted in maximum improvement as compared to Eccentric Training/contraction on hamstring flexibility.

Practical application

It is suggested to coaches, trainers, sports-physiotherapists, as well as athletes, to prefer Muscle Energy Technique over Eccentric Training when both can be performed and where the gain in flexibility/ range of motion is the objective/goal of the treatment.

Acknowledgements

We gratefully acknowledge the co-operation provided by the subjects who participated in this study.