J. Phys. Ther. Sci. 25: 233–234, 2013 Effects of Various Wedge Boards on Vastus Medialis Oblique and Vastus Lateralis Muscles during Lunge Exercise

Min-hee Kim1), Won-gyu Yoo2)

1) Institute of Health Science, Yonsei University 2) Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University and Elderly Life Redesign Institute: 607 Obangdong, Gimhae, Gyeongsangnam-do 621-749, Republic of Korea. TEL: +82 55-320-3994, FAX: +82 55-329-1678, E-mail: [email protected]

Abstract. [Purpose] This study applied the lunge exercise using a variety of foot wedge boards to analyze differ- ences in the muscle activities of the vastus lateralis (VL) and vastus medialis oblique (VMO) and the VMO/VL ratios. [Subjects] This study was performed on 20 asymptomatic males. [Methods] Surface mea- surements were obtained under 5 lunge exercise conditions. [Result] The EMG activity for the VL muscle signifi- cantly increased in the order of conditions as follows: anterior wedge < no wedge and medial wedge < lateral wedge and posterior wedge. The EMG activity for the VMO muscle significantly increased in the order of conditions as follows: anterior wedge < no wedge and lateral wedge < medial wedge and posterior wedge. The VMO/VL ratios under the medial wedge and posterior wedge conditions were significantly increased. [Conclusion] Use of medial and posterior wedge boards during the lunge exercise can selectively strengthen the VMO. Key words: Foot wedge board, Patellofemoral pain syndrome, VMO/VL ratio (This article was submitted Aug. 4, 2012, and was accepted Sep. 4, 2012)

INTRODUCTION logical conditions. The EMG signals were sent to the data acquisition unit of an MP150 system (BIOPAC Systems, Recent studies emphasize the necessity of balance between Santa Barbara, CA, USA). The EMG data were analyzed the vastus lateralis (VL) and vastus medialis oblique (VMO) using a program created with the AcqKnowledge software for treatment of patellofemoral pain syndrome (PFPS)1). (version 3.9.1) and expressed as the maximum voluntary Several studies have reported that a remarkably weaker contraction (MVC). Surface electrodes were attached VMO or delayed activation of the VMO compared with the over the VL (vastus lateralis) and VMO (vastus medialis VL is due to imbalance between the VMO and VL2). Open oblique). The subjects maintained a neutral trunk alignment chain exercise increases anterior shear force and induces with right flexion of 90 degrees and left hip and knee excessive tension of the anterior cruciate ligament3). On extension. The trunk posture was defined as anterior rotation the other hand, closed chain exercise (CCE) does not cause of the pelvis for a neutral lumbar lordosis and relaxation of anterior shear force because of the cooperative contraction the thorax with an upright head posture. The experimental of the quadriceps and the in the patellofemoral protocol specified 5 lunge exercise conditions: condition 1 joint, and functional muscle recruitment patterns can be applied no foot wedge board; condition 2 applied an anterior provided as many joints move4, 5). CCEs to strengthen the wedge board to the foot; condition 3 applied a medial wedge quadriceps femoris muscle have been performed in various board to the foot; condition 4 applied a lateral wedge board forms of exercises. In the present study, we applied the lunge to the foot; and condition 5 applied a posterior wedge board exercise most frequently used among CCEs using a variety to the foot. The angle of the wedge was 20 degrees (L×W×H: of foot wedge boards to analyze differences in the muscle 30 × 30 × 15 cm). The order in which subjects performed activities of the VL and VMO and the VMO/VL ratios. the trials with the different foot wedges was randomized to prevent any learned effects. The EMG signal was collected SUBJECTS AND METHODS for 30 seconds, excluding the first and last 10 seconds. To test for differences in VMO and VL muscle activities and the This study was performed on 20 asymptomatic males VMO/VL ratio among the various foot wedge board condi- aged 25.4 ± 3.2 years (mean ± SD); their heights and weights tions, repeated-measures analysis of variance was used to were 176 ± 2.5 cm and 69.5 ± 4.7 kg, respectively. All determine if there was a significant effect of the muscles and subjects were healthy and had been free of any back pain ratio. For the significant main effect, Bonferroni’s correction for a minimum of 1 year before the study; they had no lower was performed to identify the specific mean differences. limb or spine pathologies and no rheumatological or neuro- Differences were defined as significant at p<0.05. 234 J. Phys. Ther. Sci. Vol. 25, No. 3, 2013

RESULTS

The EMG activity for the VL muscle increased signifi- cantly in the order of conditions as follow: anterior wedge (50.9 ± 11.7%) < no wedge (58.5 ± 9.7%) and medial wedge (56.6 ± 10.1%) < lateral wedge (63.5 ± 8.5%) and posterior wedge (67.4 ± 10.7%) (p<0.05). The EMG activity for the VMO muscle increased significantly in the order of condi- tions as follow: anterior wedge (49.7 ± 10.1%) < no wedge (58.0 ± 11.0%) and lateral wedge (56.1 ± 11.4%) < medial wedge conditions (69.9 ± 13.5%) and posterior wedge (74.5 ± 11.7%) (p<0.05). The VMO/VL ratio was more Fig. 1. Foot Wedge significantly increased under the medial wedge (1.25 ± 0.25) and posterior wedge conditions (1.21 ± 0.18) than under the no wedge (0.99 ± 0.13), anterior wedge (0.99 ± 0.14) and lateral wedge conditions (0.91 ± 0.10) (p<0.05) (Fig. 1). could be therapeutically applied. Use of medial and posterior wedge boards during the lunge exercise can selectively DISCUSSION strengthen the VMO.

6) Cook et al. suggested that the squat exercise on a ACKNOWLEDGEMENT 30-degree posterior slope was more effective in activating the VMO than the same exercise on the ground because it minimized the effect of the . In this This research was supported by Basic Science Research result, use of a posterior wedge board during the lunge Program through the National Research Foundation of exercise relaxed the gastrocnemius muscle, so the VL and the Korea (NRF) funded by the Ministry of Education, Science VMO showed higher muscle activities than when exercises and Technology (No. 2012001058). were performed with a variety of postural changes on the ground and showed the highest VMO/VL ratios. On the other REFERENCES hand, the lunge exercise on an anterior wedge board showed 1) Chien JR, Lin GH, Hsu AT: Implementation of a portable electronic the lowest activity of the VMO and VL. It is considered that system for providing pain relief to patellofemoral pain syndrome patients. gastrocnemius muscle tension increased due to the anterior Rev Sci Instrum, 2011, 82: 105101. [Medline] [CrossRef] wedge board. Thus, the gastrocnemius muscle acted more 2) Kim MH, Yoo WG, Yi CH: Gender differences in the activity and ratio of vastus medialis oblique and vastus lateralis muscles during drop landing. J on knee extension, thereby relatively reducing the activity Phys Ther Sci, 2009, 21: 325–329. [CrossRef] 7) of the quadriceps muscles . In this study, when the lunge 3) Felicio LR, Saad MC, Liporaci RF, et al.: Evaluating patellar kinematics exercise was applied with a medial wedge board, significant through magnetic resonance imaging during open- and closed-kinetic- increases in VMO/VL ratios were shown along with high chain exercises. J Sport Rehabil, 2010, 19: 1–11. [Medline] 4) Tang SF, Chen CK, Hsu R, et al.: Vastus medialis obliquus and vastus activity of the VMO. The exercise on a medial wedge board lateralis activity in open and closed kinetic chain exercise in patients with causes resistance to hip adduction. This exercise showed patellofemoral pain syndrpme: an electromyographic study. Arch Phys results consistent with the hypothesis that if hip adduction is Med Rehabil, 2001, 82: 1441–1445. [Medline] [CrossRef] also induced, the muscle activity of the VMO will increase 5) Escamilla RF, Fleisig GS, Zheng N, et al.: Effects of technique variations on knee biomechanics during the squat and leg press. Med Sci Sports based on the fact that the VMO originates in the distal part Exerc, 2001, 33: 1552–1566. [Medline] [CrossRef] of the adductor magnus muscle8). In the present study, when 6) Cook JL, Khan K, Kiss S, et al.: Reproducibility and clinical utility of a lateral wedge board was applied, only the activity of the tendinopathy in young basketball players. Br J Sports Med, 2001, 35: 65–69. [Medline] [CrossRef] VL increased greatly. In this case, the VL would be overused 7) Yoon JY, An DH, Yoo WG, et al.: Differences in activities of the lower 8) because the muscle should pull against contracted states . extremity muscles with and without heel contact during stair ascent by Appropriate wedges applied to the feet may prevent the tibia young women wearing high-heeled shoes. J Orthop Sci, 2009, 14: 418–422. from rotating and correct the misalignment of the Q-angle [Medline] [CrossRef] 9) 8) Earl JE, Schmitz RJ, Arnold BL: Activation of the VMO and VL during to prevent basic factors of PFPS . The medial wedge board dynamic mini-squat exercises with and without isometric hip adduction. J used in the present study can also be used as a treatment Electromyogr Kinesiol, 2001, 11: 381–386. [Medline] [CrossRef] method for misalignment with an excessive Q-angle. Saxena 9) Saxena A, Haddad J: The effect of foot orthoses on patellofemoral pain 10) syndrome. J Am Podiatr Med Assoc, 2003, 93: 264–271. [Medline] and Haddad reported that when they applied foot wedges 10) Signorile JF, Kwiatkowksi K, Caruso JF, et al.: Effect of foot position on to patients with PFPS and conducted biomechanical tests, the electromyographical activity of the superficial quadriceps muscles the range of motion significantly increased along with the during the parallel squat and knee extension. J Strength Cond, 1995, 9: alleviation of knee pain; hence, they suggested that wedges 182–187.