See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/261800767 Adductor Longus Activation During Common Hip Exercises Article in Journal of Sport Rehabilitation · May 2014 DOI: 10.1123/JSR.2012-0046 · Source: PubMed CITATIONS READS 6 3,570 3 authors, including: Kevin Laudner Michael Torry Illinois State University Illinois State University 90 PUBLICATIONS 1,964 CITATIONS 133 PUBLICATIONS 4,536 CITATIONS SEE PROFILE SEE PROFILE All content following this page was uploaded by Kevin Laudner on 03 August 2015. The user has requested enhancement of the downloaded file. Journal of Sport Rehabilitation, 2014, 23, 79-87 http://dx.doi.org/10.1123/JSR.2012-0046 www.JSR-Journal.com © 2014 Human Kinetics, Inc. ORIGINAL RESEARCH REPORT Adductor Longus Activation During Common Hip Exercises Robert J. Delmore, Kevin G. Laudner, and Michael R. Torry Context: Hip-adductor strains are among the most common lower-extremity injuries sustained in athletics. Treatment of these injuries involves a variety of exercises used to target the hip adductors. Objective: To identify the varying activation levels of the adductor longus during common hip-adductor exercises. Design: Descriptive study. Setting: Laboratory. Participants: 24 physically active, college-age students. Intervention: None. Main Measurement Outcomes: Peak and average electromyographic (EMG) activity of the adductor longus muscle during the following 6 hip-adductor rehabilitation exercises: side-lying hip adduction, ball squeezes, rotational squats, sumo squats, standing hip adduction on a Swiss ball, and side lunges. Results: The side-lying hip-adduction exercise produced more peak and average activation than any other exercise (P < .001). Ball squeezes produced more peak and average activation than rotational squats, sumo squats, and standing adduction on a Swiss ball (P < .001). Ball squeezes had more average activation than side lunges (P = .001). All other variables for peak activation during the exercises were not statistically significant (P > .08). These results allowed the authors to provide an overall ranking system (highest to lowest muscle activation): side-lying hip adduction, ball squeezes, side lunges, standing adduction on a Swiss ball, rotational squats, and sumo squats. Conclusion: The study provides a ranking system on the activation levels of the adductor longus muscle for 6 common hip-adductor rehabilitation exercises, with the side-lying hip-adduction and ball-squeeze exercises displaying the highest overall activation. Keywords: therapeutic, rehabilitation, adductor strains Adductor strains are among the most common Soccer athletes also frequently sustain hip-adductor lower-extremity injuries seen in athletics.1–3 A common muscle injuries, with 12% to 18% of all soccer-related mechanism of this injury is when the adductors attempt injuries being diagnosed as adductor strains.5,6 Sixty to decelerate an extending, abducting leg by using an percent of these injuries are due to overuse, while the eccentric contraction to adduct and flex the hip.4 With other 40% are caused by acute trauma.5 Experience level the forceful eccentric contraction, the adductors may has also been shown to increase the incidence of adduc- not be strong enough to withstand the force, and injury tor strains in soccer, with athletes in higher experience can occur. The injury may also occur during a forceful levels reporting more adductor strains.6 In the adductor concentric contraction of the muscle. Lower-extremity muscle group, the adductor longus has been shown to be athletes such as ice hockey and soccer players are natu- most susceptible to injury when the leg is transitioning rally more prone to this pathology due to the importance from hip extension to hip flexion during a soccer kick.7 of the hip adductors in lower-extremity performance.4 This is a common action not only in soccer but also in Research has reported that 10% of all ice hockey any sport requiring forceful hip flexion and extension. injuries sustained are hip-adductor strains.1 Other Hockey players perform a similar motion while skating, research has found that 43% of all muscle strains over the making the mechanism of hip-adductor injury common course of a hockey season are diagnosed as hip-adductor in both soccer and hockey. strains.2 Another investigation looking solely at adductor/ The adductor longus muscle has been found to be the abdominal-strain incidence in all U.S. National Hockey most frequently injured of the adductor group, with 62% League teams over 6 competitive seasons reported that of adductor injuries occurring to the musculotendinous out of 7050 ice hockey players, 617 adductor/abdominal junction of the adductor longus.8 With adductor strains strains were reported, with adductor strains being the being such a common injury among different athletes, most common compared with abdominal strains.3 understanding how the adductor longus muscle specifi- cally functions during different exercises becomes a key component in the prevention and treatment of such inju- ries. With the occurrence of hip-adductor strains being The authors are with the School of Kinesiology and Recreation, 17 times more likely when hip-adductor strength is 80% Illinois State University, Normal, IL. or less than the strength of the abductors,9 this makes 79 80 Delmore, Laudner, and Torry adductor strength a vital component in the prevention of test electrode was applied to the adductor longus at the this pathology. Past studies have used an array of adduc- center of the muscle belly parallel to the muscle fibers. tor exercises while looking at adductor-injury-prevention The adductor longus belly was found midway between programs, as well as for postinjury rehabilitation proto- the origin at the pubic tubercle and the insertion at the col.10,11 At the heart of these techniques are activities that medial linea aspera of the femur.14 To ensure electrode specifically target adductor strength and stabilization. placement, the test leg was passively abducted and the While these methods have been suggested to help treat adductor longus muscle belly was palpated just distal to adductor pathologies, the amount of specific muscle the muscle’s tendon, traced from the pubic tubercle on the activation during individual exercises has yet to be exam- medial side of the leg. The participant was then asked to ined. Therefore, the purpose of this study was to identify actively adduct the leg against resistance to confirm that the amount of activation of the adductor longus muscle motor-unit activation was recorded by appropriate place- during common hip-adductor-strengthening and -stabi- ment of the electrode. A ground electrode was placed on lization exercises. By obtaining these data, clinicians the anteromedial tibia of the test leg. may be able to choose specific exercises to reach desired Once prepared, the participants first performed activation levels of the hip adductors, thereby assisting in a 5-second maximal voluntary isometric contraction the prevention and rehabilitation of such injuries. (MVIC) of the adductor longus to gain a baseline mea- surement. MVICs were taken with the participant side- lying on the test side, with the contralateral leg flexed so Methods that the foot rested on the table in front of the participant. The test leg was kept straight and was lying flat against Participants the table. The researcher then provided manual resistance Twenty-four male participants (age 21.5 ± 2.0 y, height against the leg as the participant attempted to adduct 180.5 ± 6.3 cm, mass 86.9 ± 10.8 kg) volunteered to par- toward the ceiling (Figure 1). The test leg was kept flat ticipate in this study. Exclusion criteria included previous on the table during each MVIC to ensure an isometric history of lower-extremity injury within the past 6 months contraction. The participant was asked to provide a maxi- and any previous history of hip surgery. Participants were mal effort for 5 seconds for a total of 5 trials. required to be active for a minimum of 3 times per week, The participants performed each of the following for at least 30 minutes per session. Each participant was 6 hip-adductor exercises: side-lying hip adduction, informed of the experimental risks of the study and signed ball squeezes, rotational squats, sumo squats, standing an informed-consent form as approved by the university hip adduction on a Swiss ball, and side lunges. The 10,15 review board before data collection. exercises were chosen based on previous research and our 12 years of therapeutic exercise experience. Stabilization exercises were defined as exercises that Instrumentation incorporated adductor longus activation to maintain Muscle-activity data were obtained using surface elec- an exercise pattern or stance. Strength exercises were tromyography (EMG; Bagnoli EMG system, Delsys Inc, defined as exercises that incorporated adductor longus Boston, MA). Signals were amplified from a test electrode activation to sustain activation against resistance. All (Delsys DE-2.1 differential EMG sensor, Delsys Inc, exercises were completed at the pace of a metronome set Boston, MA) and a disposable pregelled adhesive ground at 1 beat/s to maintain compliance with the variable of electrode with a circular contact diameter of 5 cm. EMG time. The researcher also provided a verbal cadence to data were collected at a frequency of 2000 Hz per channel. the beat of the metronome to ensure that the participant Each EMG signal exhibited a bandwidth of 3 dB at 10 to maintained the correct rhythm during the exercise. The 500 Hz. The lower cutoff filter was a first-order, high-pass verbal cadence consisted of the researcher counting out design. The upper cutoff filter was a fourth-order But- the seconds during each repetition of the exercise. The terworth low-pass design. The differential amplifier had researcher providing the verbal cadence was also in a fixed gain of 1000, an input impedance of >10Ω , and charge of striking the force platform at the beginning a common rejection ratio of 130 dB.