Comparison of hamstring muscles activity between subjects with normal and shortened hamstring muscle during plank exercise

Ⅰ. Introduction

Plank exercise (PE) is an exercise commonly used to improve lumbar stability and body movement, and to prevent and rehabilitate back injuries (Snarr and Michael RE, 2014). PE enhances sports performance by increasing the activity of core muscles, such as the external oblique (EO), internal oblique (IO) and transverse abdominis (TrA) muscles (Cosio-Lima et al., 2003; Yoon et al., 2015; Park et al., 2020). Strengthening core muscles through PE can reduce the incidence of back injuries and improve exercise performance (Duncan, 2009). PE is also effective in the prevention and treatment of low back pain, by enhancing the strength and endurance of muscles around the lower back, such as the erector spinae (ES) and multifidus muscles, in turn improving lower back flexibility and balance and ultimately reducing the incidence of back injuries (Kwon, 2008). The core region functions as a movement chain for various activities at the body center; therefore, lower limb function can be enhanced by strengthening the core muscles (de Marche Baldon et al., 2012; Han WJ and Son KH, 2019). Thus, PE can increase stability around the trunk by strengthening the core muscles and improving lower limb muscles strength and endurance, by enhancing the functional connection between the trunk and lower limbs.

Strengthening the hamstrings (HAM) of lower limb muscles can increase the flexibility of the lower back and leg muscles, thereby reducing back pain (An, 2005). In addition, it can increase knee stability through co-activation of the quadriceps femoris muscle (Park, 2006; Oh, 2013). However, a shortened HAM can cause malalignment of the lumbar and pelvis and limit anterior pelvic tilt during lumbar–pelvic rhythm movement, inducing lumbar hypermobility and ultimately resulting in various forms of lumbar-related disease (Kim and Hwang, 2012). PE is an effective exercise to enhance lower back stability by strengthening the core and lower limb muscles; however, it may cause abnormal lumbar and pelvic movement due to HAM hyperactivity when applied to subjects with a shortened HAM. Therefore, it is necessary to investigate the effects of PE on the core muscles and HAM in subjects with a shortened HAM. In this study, we hypothesized that subjects with a shortened HAM would have higher activity in certain muscle groups during PE than subjects with a normal HAM length.

Ⅱ. Methods

Ⅲ. Results

The results showed that ES, RA, and EO muscle activities were larger in the NHG than in the SHG; however, no significant differences were detected. HAM muscle activity was significantly higher in the SHG than in the NHG (p<.05)<Table 1>.

Table 1.

Comparisons of trunk muscles and hamstring muscle activation between normal length of hamstring group and shortened length of hamstring group

Ⅳ. Discussion

PE is a commonly used core exercise; various studies of PE have been conducted, particularly comparing the effects of diverse PE methods on muscle activation. Lee et al(2016) studied ES, EO, and RA muscle activities during PE performed on three different surfaces to determine the surface that induced the highest muscle activity, and suggested that this approach should be used to recommend specific PEs to professional athletes and patients with weakened abdominal muscles. Kang et al(2016) investigated changes in the thickness and balance ability of the TrA, IO, and EO muscles when PE was performed on various supporting surfaces over a 4-week period, to determine the most effective PE method for healthy subjects. The present study showed that core muscle activity differed between subjects with normal and shortened HAMs, although these differences were not significant. This finding suggests that the effects of the same PE can vary according to characteristics of subject such as muscle tightness and shortness, asymmetrical right and left muscle length.

HAM injury is the most common injury in athletes, and can be caused by various factors including weakened knee flexors (Ekstrand et al., 2012), muscle imbalance between the quadriceps femoris and HAM muscles (Fousekis et al., 2011), and performing exercise while the long head of the biceps femoris (a HAM muscle) is shortened (Timmins, et al., 2016). When there is an imbalance in the muscles around the femur, the strong HAM muscle continues to activate; this results in a more severe imbalance between the muscles, in turn inducing HAM injuries and low back pain, which are related to patellofemoral pain syndrome (Lardner et al., 2010). In this study, HAM activity tended to increase in an effort to maintain hip joint extension during PE, while knee extension posture increased the passive tension in the HAM, further stimulating its activity. Therefore, if a person with a shortened HAM performs repetitive PE, HAM stimulation will increase to cause hyperactivity, which may negatively impact the lower back and knee joints.

Ⅴ. Conclusion

When PE is performed by a subject with a shortened HAM, it lead to overactivate the HAM. Due to the negative effects of an overactive HAM on the lower back and knee joints, it is recommended that people with a shortened HAM perform sufficient HAM stretching before PE or perform alternative exercises to strengthen the core muscles.

References

• An C. The effects of hamstring stretching exercise on angle of lumbar flexion and pain reduction with chronic low back patients. J Kor Phy Ther 2005;17(4);559-67.
• Cosio-Lima LM, Reynolds KL, Winter C, et al. Effects of physioball and conventional floor exercises on early phase adaptations in back and abdominal core stability and balance in women. J Strength Cond Res 2003;17(4);721-5. [https://doi.org/10.1519/00124278-200311000-00016]
• de Marche Baldon R, Lobato DFM, Carvalho LP et al. Effect of functional stabilization training on lower limb biomechanics in women. Med Sci Sports Exer 2012;44(1);135-45. [https://doi.org/10.1249/MSS.0b013e31822a51bb]
• Duncan M. Muscle activity of the upper and lower rectus abdominis during exercises performed on and off a swiss ball. J Bodyw Mov Ther 2009;13(4);364-7. [https://doi.org/10.1016/j.jbmt.2008.11.008]
• Ekstrand J, Healy JC, Waldén M, et al. Hamstring muscle injuries in professional football: The correlation of MRI findings with return to play. Br J Sports Med 2012;46(2);112-7. [https://doi.org/10.1136/bjsports-2011-090155]
• Fousekis K, Tsepis E, Poulmedis P, et al. Intrinsic risk factors of non-contact quadriceps and hamstring strains in soccer: A prospective study of 100 professional players. Br J Sports Med 2011;45(9);709-14. [https://doi.org/10.1136/bjsm.2010.077560]
• Han WJ, Son KH. The Effect of Unstable Support Surface Plank Exercise on Flexibility, Abdominal Muscle Thickness and Pain in Chronic Low Back Pain. Kor Phy Ther Sci 2019;26(3):23-36. [https://doi.org/10.26862/jkpts.2019.12.26.3.23]
• Kang K, Son S, Ko Y. Changes in abdominal muscle thickness and balance ability on plank exercises with various surfaces. J Kor Phy Ther 2016;28(5);264-8. [https://doi.org/10.18857/jkpt.2016.28.5.264]
• Kim GC, Hwang BG. Kinetic Analysis on the Lumbar at the Trunk Flexion according to the Degree of Hamstring Flexibility of Healthy Adult. J Kor Soc Phy Med 2012;7(4);501-7. [https://doi.org/10.13066/kspm.2012.7.4.501]
• Kwon BY. Effects of core stability and mobility training with aero equipment on biomechanical balance, posture, strength and agility for rhythmic gymnasts. [dissertation] Ewha Womans University; 2008.
• Lardner PF, Frank CC, Page P. Assessment and treatment of muscle imbalance the janda approach; 2010.
• Lee et al. Comparison of three different surface plank exercises on core muscle activity. Phy Ther Rehab Sci 2016;5(1);29-33. [https://doi.org/10.14474/ptrs.2016.5.1.29]
• Magee DJ. Orthopedic Physical Assessment. Elsevier Health Sciences; 2013.
• Mendell JR, Florence J. Manual muscle testing. Muscle Nerve: Official Journal of the American Association of Electrodiagnostic Medicine 1990;13(S1);S16-20. [https://doi.org/10.1002/mus.880131307]
• Oh YT, Effect of hold-relax technique for college students with hamstring shortening. J Kor Soc Phy Med 2013;8(3):433-41. [https://doi.org/10.13066/kspm.2013.8.3.433]
• Park M. Changes of quadriceps and hamstring strength ratio in women of different ages. Phy Ther Kor 2006;13(3);75-83.
• Park YA, Kim EJ, Cha HY, et al. Effects of various plank exercises on activation of hamstring muscle. Kor Phy Ther Sci 2020;27(1):51-5. [https://doi.org/10.26862/jkpts.2020.06.27.1.51]
• Schoenfeld BJ, Contreras B, Tiryaki-Sonmez G et al. An electromyographic comparison of a modified version of the plank with a long lever and posterior tilt versus the traditional plank exercise. Sports biomech 2014;13(3);296-306. [https://doi.org/10.1080/14763141.2014.942355]
• Snarr RL, Esco MR. Electromyographical comparison of plank variations performed with and without instability devices. J Strength Cond Res 2014;28(11);3298-305. [https://doi.org/10.1519/JSC.0000000000000521]
• Timmins RG, Bourne MN, Shield AJ et al. Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): A prospective cohort study. Br J Sports Med 2016;50(24);1524-35. [https://doi.org/10.1136/bjsports-2015-095362]
• Yoon M, Choi H, Shin W. Effects of the abdominal drawing-in maneuver and the abdominal expansion maneuver on grip strength, balance and pulmonary function in stroke patients. J Kor Phy Ther 2015;27(3);147-53. [https://doi.org/10.18857/jkpt.2015.27.3.147]