Gender Differences in the Activity and Ratio of Vastus Medialis Oblique and Vastus Lateralis Muscles during Drop Landing

Transcription

1 Original Article Gender Differences in the Activity and Ratio of Vastus Medialis Oblique and Vastus Lateralis Muscles during Drop Landing J. Phys. Ther. Sci. 21: , 2009 MIN-HEE KIM 1), WON-GYU YOO 2), CHUNG-HWI YI 3) 1) Department of Rehabilitation Therapy, The Graduate School, Yonsei University 2) Department of Physical Therapy, College of Biomedical Sciences and Engineering, Inje University 3) Department of Physical Therapy, College of Health Science, Yonsei University: 234 Maeji-ri, Heungup-myun, Wonju, Kangwon-do, , Republic of Korea. TEL: , FAX: , Abstract. [Purpose] The purpose of this study was to determine whether gender differences exist in the activity and ratio of the vastus medialis oblique and vastus lateralis muscles when performing a vertical drop landing. [Subjects] Thirty participants (15 males, 15 females) dropped from the height of their lower leg. [Methods] The EMG activities of the vastus medialis oblique and vastus lateralis muscles were recorded during vertical drop landing using surface electrodes. [Results] The muscle activities and the ratio of both muscles were significantly higher for males than for females. The muscle activity of the vastus medialis oblique muscle was 36.3% for males and 20.2% for females, and that of the lateralis muscle was 34.2% for males and 26.1% for females. The mean ratio of the vastus medialis oblique muscle : vastus lateralis muscle was 1.07 for males and 0.78 for females. [Conclusion] For females, drop landing in females may increase the likelihood of patellofemoral pain syndrome. Key words: Gender difference, Patellofemoral pain syndrome, Vastus medialis oblique: vastus lateralis muscle ratio (This article was submitted May. 14, 2009, and was accepted Jun. 29, 2009) INTRODUCTION Inappropriate landing motions result in improper absorption of impact when the feet come in contact with the ground and may cause excessive stress and injury to the knee joint system 1). Landing with less knee-bending increases impact during landing, resulting in an increased load on the surrounding knee joint 2). The patella is joined to the quadriceps muscle, which is far from the axis of motion. It serves as the fulcrum of a lever to improve the extension efficiency of the knee joint, reduce friction of the quadriceps mechanism, relieve tension in the knee joint capsule, and protect the femur and cartilage 3). When the patella is pushed outside from the patella surface between femoral condoyles, patellofemoral pain syndrome is caused, which results in serious pain around the knee 4). If this occurs repetitively, an individual may develop degenerative arthritis due to abrasion of the articular surface 5). Many studies have demonstrated that the patellae of patients with patellofemoral pain syndrome are excessively dragged outward 6,7). It was reported that this excessive outward dragging is caused by imbalance between the vastus medialis oblique muscle and the vastus lateralis muscle, and that it is a main cause of patellofemoral pain

2 326 J. Phys. Ther. Sci. Vol. 21, No. 4, 2009 syndrome. The weakness of quadriceps during climbing or descending stairs is a major cause of patellofemoral pain syndrome or osteoarthritis in the knee for women 8). Especially, the syndrome appears more often among women who are afflicted with muscle weakness and muscle imbalance 9). Chappell et al. 10) investigated the kinematic differences in the pressure on knees between male and female athletes during vertical landing motions. They reported that female athletes had increased anterior shear force of the knee compared to male athletes and stated that knee motor control strategies among female athletes caused this anterior shear force. Ford et al. 9) reported that the lack of knee joint stability in the knee could be a factor increasing the ACL injuries of female athletes. This lack of stability can easily cause patellofemoral pain syndrome due to the imbalance of muscles 11). Yi et al. 12) presented the kinematic differences in landing motions between male and female college students and reported that the valgus angles of women were more increased than those of men during vertical landing motion. They suggested future studies of measurements of muscle activities of the muscles that are used for landing motions and the evaluation of the imbalance of muscles 13). It has also been reported that an excessive knee valgus angle may cause imbalance of the muscles around the knee 14). Based on the theories of previous studies, this study measured the muscle activities of the vastus medialis oblique muscle and the vastus lateralis muscle during landing motions according to gender so as to determine the basic data for predicting the risk of patellofemoral pain syndrome due to differences in landing postures. SUBJECTS AND METHODS Subjects The subjects in this study were 15 males [age: 26.2 ± 1.8 years (mean ± SD); height: ± 6.8 cm; body weight: 73.1 ± 6.3 kg] and 15 females [age: 23.7 ± 3.1 years; height: ± 4.2 cm; body weight: 57.9 ± 5.3 kg] who consented to participate in this experiment. Ethical approval of this study was obtained from the Yonsei University Faculty of Health Sciences Human Ethics Committee. Methods Before starting the experiment, the authors explained the experimental procedure to the subjects. The selection criteria for the subjects were as follows: (1) a dominant right leg; (2) normal range of movement for the ankle, knee, and hip joint; and (3) no injury to the waist or legs in the past 12 months. The muscle activity of each muscle was measured with an MP100 system, and DE-3.1 Double Differential Electrodes were used. The electromyogram electrodes were attached to the outward side from the center of the thigh at 3 5 cm above the right knee for the vastus lateralis muscle, and at 2 cm to the inward diagonal direction at 55 from the knee for the vastus medialis oblique muscle. Because individual differences can influence the results, all of the values were normalized to the %Maximal Voluntary Contraction (%MVC) during knee extension at a knee angle of 80 and hip joint angle of 90 in the sitting position with the trunk fixed 15). All experiments and measurements were performed by one researcher. The EMG data were sampled at 1,000 Hz using Acqknowledge software (BIOPAC System) and a notebook computer. The recordings were notch-filtered at 60 Hz, and amplified. The data were stored on a PC after analog-to-digital conversion and then averaged. Each subject performed vertical landing motions with the locations of the feet specified at the starting point and landing point. To reduce individual differences, we adjusted the height of the vertical landing based on participants height. We had the subjects perform vertical landing from a table, the height of which was adjusted to the distance between the midpoint of the knee joint and the heel of each subject. The subjects were asked to repeat the vertical landing motion three times, and their means were calculated for data analysis. A foot switch was installed at the landing point; it was connected to the electromyogram system so that the precise time of landing would be automatically displayed on a screen. The vastus medialis oblique and vastus lateralis muscle were measured at the moment of landing at the point where the foot switch was installed, and the subjects were asked to allow their arms to move naturally during the landing. Furthermore, the subjects were asked to keep their line of vision to the front and return to an upright position after landing. For natural landing motions, the subjects practiced landing motions twice before the experiment. The SPSS statistical package (SPSS, Chicago, IL)

3 327 Table 1. Comparison of normalized EMG between males and females Mean ± SD Males (n=15) Females (n=15) Vastus medialis oblique (VMO, %) 36.3 ± ± 7.5* Vastus lateralis (VL, %) 34.2 ± ± 7.1* VMO/VL ratio 1.07 ± ± 0.20* *p<0.05. was used to analyze differences in the vastus medialis oblique and vastus lateralis muscle activities and in the vastus medialis oblique : vastus lateralis muscle ratio. The significance of differences between males and females was tested by the paired t-test, with significance defined as being present when p<0.05. RESULTS The muscle activities of the vastus medialis oblique and vastus lateralis muscle and the ratio of the vastus medialis oblique : vastus lateralis muscle during vertical landing motions were compared between males and females. The muscle activities and ratio of both muscles were significantly higher for males than for females (p<0.05). The muscle activity of the vastus medialis oblique muscle was 36.3% for males and 20.2% for females, and that of the lateralis muscle was 34.2% for males and 26.1% for females. The ratio of the vastus medialis oblique : vastus lateralis muscle was 1.07 for males and 0.78 for females (Table 1). DISCUSSION Patellofemoral pain syndrome can be caused by weakening of the quadriceps, weakening of the vastus medialis oblique muscle, increasing of the knee valgus angle, shortening of the lateral retinaculum, gastrocnemius, and hamstring, loss of normal lower limb mechanisms, or overuse 16,17). Previous studies that compared gender differences in vertical landing motions found that women have a smaller knee-bending angle and higher knee valgus angle compared to men during landing 12,18). Based on the theories of previous studies, this study measured the muscle activities of the vastus medialis oblique and vastus lateralis muscle during the landing motion. It was previously reported that quadriceps muscle activities of women were significantly lower than those of men 19,20). In the present study, similarly, quadriceps muscle activities (both vastus medialis oblique and vastus lateralis) were significantly lower for females than for males. We consider that women did not use their quadriceps as much as men did, due to the genetic, biological, structural disparity between them. There are many theories on the etiology of the greater incidence of patellofemoral injuries in females 21). Teichtahl et al. 22) reported that increased anthropometric measures of obesity, as well as fat mass, are associated with increased risk of patellofemoral injury for both males and females; particularly females, who have greater baseline body mass, and appear to have an increased risk for the onset and progression of patellofemoral injury 22). Yi et al. 18) who studied gender differences in the knee-bending angle during vertical landing reported that the knee-bending angles of women were smaller than those of men. It seems that women use the quadriceps less than men and they do not sufficiently bend their knees during vertical landing. Previous studies reported that when the knee valgus angle increases to an abnormal proportion, it affects the distance between the origin and insertion of the vastus lateralis muscle. As it shortens the traction line of the vastus lateralis muscle, the muscles must be pulled in a contracted condition. Therefore, the vastus lateralis muscle and tensor fasciae latae muscle are overused in dynamic exercises 19). In the present study, similarly the vastus lateralis muscle contracted more than the vastus medialis oblique muscle, and the ratio of vastus medialis oblique : vastus lateralis muscle was lower among women than among men. The findings of this study support those of Yi et al. 12), who studied the influence of gender on the knee valgus angle during vertical landing and found that the angle of female college students was greater than that of male college students. Particularly during sports motions, outward pulling of the patella often results from abnormal alignment of the knee joint and loss of contraction force in the vastus medialis oblique muscle 15). Recent studies showed that among patients with patellofemoral pain syndrome, the muscle activity of the vastus medialis oblique was lower than that of the vastus lateralis muscle, or the vastus lateralis muscle contracted earlier than the vastus medialis

4 328 J. Phys. Ther. Sci. Vol. 21, No. 4, 2009 oblique muscle compared to ordinary adults. In recent studies, the main cause of the patellofemoral pain syndrome has been reported as imbalance of the vastus medialis oblique and vastus lateralis muscles 7,16,17). Furthermore, the patellofemoral malalignment directly influences the balance of the surrounding joints and muscle-tendon structures 23). Because the greater contraction of the vastus lateralis muscle and the increased knee valgus angle during vertical landing by women influences the tibial rotation, tension in the medial part of the knee joint excessively increases 24). The imbalance of muscles around the knee can cause changes in the alignment of the knee joint 14). Therefore, to prevent knee injuries in women, improved muscle balance around the knee during dynamic motions such as landing and the balanced strengthening of lower limb muscles are necessary. Moreover, the fixing action against femoral rotation by the vastus medialis oblique muscle is essential for the prevention and treatment of knee injuries; thus, the selective strengthening of the vastus medialis oblique muscle is very important 19). According to the results of previous studies and the present study, women are vulnerable to musculoskeletal diseases such as patellofemoral pain syndrome from repeated landing motions. Therefore, it is necessary to provide education about correct landing motions and selective muscular force strengthening programs for the improvement of knee stability and the balanced development of lower limb muscles in women. REFERENCES 1) Hewett TE, Riccobene JV, Lindenfeld TN: The effect of neuromuscular training on the incidence of knee injury in female athletes: a prospective study. Am J Sports Med, 1999, 27: ) Arendt E, Dick R: Knee injury patterns among men and women in collegiate basketball and soccer. NCAA data and review of literature. Am J Sports Med, 1995, 23: ) Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation. St. Louis: Mosby, 2002, pp ) Witvrouw E, Danneels L, Tiggelen DV, et al.: Open versus closed kinetic chain exercises in patellofemoral pain. Am J Sports Med, 2004, 32(5): ) Quilty B, Tucker M, Campbell R, et al.: Physiotherapy, including quadriceps exercises and patellar taping, for knee osteoarthritis with predominant patello-femoral joint involvement: randomized controlled trial. J Rheumatol, 2003, 30(6): ) Blond L, Hansen L: Patellofemoral pain syndrome in athletes: a 5.7 year retrospective follow-up study of 250 athletes. Acta Orthop Belg, 1998, 64: ) Sheehy P, Burrdett R, Irrgang J, et al.: An electromyographic study of vastus lateralis activity while ascending and descending steps. J Orthop Sports Phys Ther, 1998, 27: ) Cahue S, Dunlop D, Hayes K, et al.: Varus-valgus alignment in the progression of patellofemoral osteoarthritis. Arthritis Rheum, 2004, 50(7): ) Ford KR, Myer GD, Hewett TE: Valgus knee motion during landing in high school female and male basketball players. Med Sci Sports Exerc, 2003, 10: ) Chappell JD, Yu B, Kirkendall DT, et al.: A comparsion of knee kinetics between male and female recreational athletes in stop-jump tasks. Am J Sports Med, 2002, 30: ) Griffin LY, Agel J, Albohm MJ, et al.: Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies. J Am Acad Orthop Surg, 2000, 8: ) Yi CH, Park SY, Yoo WG: Gender differences of knee valgus angle during vertical drop landing in college students. J Korean Acad Univ Trained Phys Therapists, 2005, 12(1): ) McClinton S, Donatell G, Weir J, et al.: Influence of step height on quadriceps onset timing and activation during stair ascent in individuals with patellofemoral pain syndrome. J Orthop Sports Phys Ther, 2007, 37(5): ) DeVan MR, Pescatello LS, Faghri P, et al.: A prospective study of overuse knee injuries among female athletes with muscles imbalances and structural abnormalities. J Athl Train, 2004, 39(3): ) Newman SA, Jones G, Newham DJ: Quadriceps voluntary activation at different joint angles measured by two stimulation techniques. Eur J Appl Physiol, 2003, 3: ) Boucher JP, King MA, Lefebre R, et al.: Quadriceps femoris muscle activity in patellofemoral pain syndrome. Am J Phys Med, 1992, 20: ) Miller J, Sedory D, Croce R: Vastus medialis obliques and vastus lateralis activity in patients with and without patellofemoral pain syndrome. J Sport Rehabil, 1997, 6: ) Yi CH, Park SY, Lee SH: Gender differences in knee angle on landing from a drop-jump: kinematic data in young adults. J Phys Ther Sci, 2004, 16: ) Earl JE, Schmitz RJ, Arnold BL: Activation of the VMO and VL during dynamic mini-squat exercises with and without isometric hip adduction. J Electromyogr Kinesiol, 2001, 11: ) Escamilla RF, Fleisig GS, Zheng N, et al.: Effects of technique variations on knee biomechanics during the squat and leg press. Med Sci Sport Exerc, 2001, 33(9):

5 ) Arendt EA, Agel J, Dick R: Anterior cruciate ligament injury patterns among collegiate men and women. J Athletic Training, 1999, 34: ) Teichtahl AJ, Wang Y, Wluka AE, et al.: The longitudinal relationship between body composition and patella cartilage in healthy adults. Obesity, 2008, 16: ) Tiberio D: The effect of excessive subtalar joint pronation on patellofemoral mechanics. J Orthop Sports Phys Ther, 1987, 9: ) McPoil TG, Cornwall MW: Footwear and foot orthotic effectiveness research. J Orthop Sports Phys Ther, 1995, 21: