CSM 2017 Sports Physical Therapy Section Poster Presentations (Abstracts SPO1–SPO152)

Abstract

Previous article Full AccessAPTA Combined Sections MeetingSports Physical Therapy Section Poster Presentations (Abstracts SPO1–SPO152)AuthorsJournal of Orthopaedic & Sports Physical TherapyPublished Online:December 31, 2016Volume47Issue1PagesA162-A226https://www.jospt.org/doi/10.2519/jospt.2017.47.1.A162SectionsPDFPDF PLUSAbstract ToolsAdd to FavoritesDownload CitationsTrack CitationsPermissions ShareShare onFacebookTwitterLinkedInRedditEmail AboutAbstractThese abstracts are presented here as prepared by the authors. The accuracy and content of each abstract remain the responsibility of the authors. In the identification number above each abstract, SPO designates a Sports Physical Therapy Section poster presentation.J Orthop Sports Phys Ther 2017;47(1):A162–A226. doi:10.2519/jospt.2017.47.1.A162SPO1Incidence of Injury in Boys' and Girls' High School Soccer: A 25-Year Longitudinal StudyMarisa R. Abegg, Alexandra K. Dillon, Glenn D. Beachy, Cedric Akau, Mitchell J. RauhDoctor of Physical Therapy Program, San Diego State University, San Diego, California; Punahou School, Honolulu, Hawaii; Straub Clinic and Hospital, Honolulu, HawaiiPURPOSE/HYPOTHESIS: Although a popular interscholastic sport, few studies have described the injury risk of high school and middle school soccer players. The purpose of this longitudinal study was to determine the incidence rates of injury among boys' and girls' interscholastic soccer players over a 25-year period.NUMBER OF SUBJECTS: We studied 1203 athletes (637 boys, 566 girls) who participated in interscholastic soccer at a US Western State School (grades 7–12) between 1988 and 2013.MATERIALS/METHODS: Data included all injuries that resulted from participation in a soccer practice or game. An injury was defined as any athlete complaint that required the attention of the athletic trainer, regardless of time lost from activity. Athletic exposure (AEs) data (each athlete's daily participation in a practice or game where he/she was at risk for injury) was also collected. Incidence rates per 1000 AEs were calculated for overall incidence, practices and games, body location, injury type, injury severity, and position played. Rate ratios (RR) and 95% confidence intervals (CIs) were used to compare sex and practice versus game injury rates.RESULTS: There were 4101 injuries for an overall injury rate of 11.5/1000 AEs. Girls had a higher overall injury rate (12.0/1000 AEs) than boys (11.0/1000 AEs) (RR = 1.09; 95% CI: 1.0, 1.2; P = .01). Overall, the injury rate during games (7.2/1000 AEs) was higher than in practices (4.6/1000 AEs) (RR = 1.57; 95% CI: 1.4, 1.7; P<.001), with similar patterns for boys and girls. The incidence of injury was highest at the ankle for girls (1.6/1000 AEs) and boys (1.3/1000 AEs). Sprains and strains were the most common injury types for girls (2.1/1000 AEs, 1.7/1000 AEs, respectively) and boys (1.7/1000 AEs, 1.3/1000 AEs, respectively). The incidence of ACL injury was almost 8 times higher for girls (0.08/1000 AEs) than boys (0.01/1000 AEs) (RR = 7.65; 95% CI: 1.7, 33.7; P = .001). The incidence for concussion was higher for girls (0.3/1000 AEs) than for boys (0.2/1000 AEs) (RR = 1.52; 95% CI: 1.0, 2.3; P = .04). Most (53.6%) injuries were minor (no time lost) in severity (6.2/1000 AEs). Injury rates for mild (1–7 days lost), moderate (8–21 days lost) and severe (22 or more days lost) injuries were 4.5/1000 AEs, 5.7/1000 AEs, and 3.1/1000 AEs, respectively. Overall, injury rates were highest for midfielders (2.0/1000 AEs) and fullbacks (1.7/1000 AEs), with similar position injury rate patterns for boys and girls.CONCLUSIONS: The results of this study suggest that the risk for injury is higher for girls during an interscholastic soccer season, especially for ACL and concussion injuries. The risk of injury was greater during games than in practices for boy and girl players.CLINICAL RELEVANCE: In terms of injury prevention planning, the data suggest there is a need to reduce lower extremity injuries in soccer players, particularly for girls. Special attention should be devoted to determining the reasons and mechanisms (ie, risk factors) for the higher incidence of ACL and concussion injuries observed among interscholastic girl soccer players.SPO2Influence of Patient Demographics and Graft Type on ACL Second Injury Rates in Ipsilateral Versus Contralateral Knees: Systematic ReviewGabrielle Adams, Olivia Pryzbylkowski, David LogerstedtPhysical Therapy, University of the Sciences, Philadelphia, PennsylvaniaPURPOSE/HYPOTHESIS: Patients after primary anterior cruciate ligament reconstruction (ACLR) are at risk for second injury due to age, sex, type of graft reconstruction, and activity level. While there is a greater likelihood of sustaining a second ACL injury after primary ACLR, little evidence exists to determine which patient demographics and graft type contribute to increased ACL second injury.NUMBER OF SUBJECTS: Twenty-two thousand five hundred ninety-four participants after ACL reconstruction.MATERIALS/METHODS: A computerized search of the databases MEDLINE, CINAHL, and SPORTDiscus were searched for full text articles published in English using combinations of the following terms: anterior cruciate ligament, ACL reconstruction, ACL surgery, reinjury, retear, rerupture, revisions, contralateral tear, ipsilateral graft tear, and/or second injury. In order to be included in the final review, studies were required to report the number or percentage of second ACL injury (ipsilateral reinjury or contralateral injury) after primary ACLR, sex, and graft type.RESULTS: Among the 11 studies that met the inclusion criteria, 22 594 participants had a primary ACLR and a total of 1424 second injuries that occurred to either the ipsilateral ACLR graft or contralateral uninjured ACL. A review of the studies reported that there was a greater number of second injuries to the ipsilateral limb (735/1424) compared to the contralateral limb (686/1424). Based on the 9 articles that specified rates of second injury in men and women, men (4.45%) have a lower incidence of second ACL injuries than women (5.81%). Women had a greater number of contralateral injuries (244/495) to men (222/626); whereas, men had a higher number of ipsilateral injuries (404/626) compared to women (250/495). Of the 6 articles that reported graft type, 60.5% of participants had hamstring tendon autografts (HT) and 69.1% of participants had allograft reinjuries on the ipsilateral side while participants with bone patella tendon bone autografts (BPTB) had higher contralateral injury rates (59.8%).CONCLUSIONS: Second injuries to the ipsilateral graft are more likely to occur in men compared to women, whereas women are more likely to sustain an injury to the contralateral limb compared to men. Compared to other graft types, HT were found to have a higher number of second injury to the ipsilateral limb; whereas, BPTB has an increased likelihood of contralateral injury.CLINICAL RELEVANCE: Clinicians should be aware of the reinjury rates after ACL reconstruction and the influence that sex and graft may have on those reinjury rates. Clinicians can then determine how physical therapy can play role to address strength imbalances or neuromuscular deficits, and estimate an appropriate time frame for a specific individual to return to sport.SPO3Effect of Running Speed on Achilles Tendon Stress in FemalesKelly Adkins, Jessica Miller, Thomas W. KernozekHealth Professions, University of Wisconsin-La Crosse, La Crosse, WisconsinPURPOSE/HYPOTHESIS: Increasing one's running cadence has been suggested to be an influential parameter in decreasing stress and strain of the Achilles tendon (AT). Additionally, it has been shown that running cadence is closely related to speed, with step frequency increasing linearly as running speed increases. However, specific information regarding how AT stress changes with running speed has yet to be examined and may provide additional insight into prevention or treatment of patients with injuries involving the AT or gastrocnemius/soleus complex. Therefore, the purpose of our study was to compare the effect of speed on AT stress during running. We hypothesized that AT stress and strain would be lower at slower running speeds.NUMBER OF SUBJECTS: Nineteen.MATERIALS/METHODS: Nineteen healthy female recreational runners (mean ± SD age, 21.44 ± 1.85 years) with a rearfoot strike pattern participated. Transverse 2-D ultrasound images were obtained of each participant's AT cross-sectional area before being equipped with 47 markers for 3-D motion capture. Participants ran down a 20-m runway under 3 recreational speed conditions: 2.8, 3.3, and 3.8 m/s ± 5%. Speed was calculated by the elapsed time (seconds) through 2 photoelectric timing gates placed 2.3 m apart along the runway. 15 motion analysis cameras captured kinematic data at 180 Hz while kinetic data were collected using a force platform at 1800 Hz. Muscle forces were estimated using static optimization. Multivariate statistics with repeated measures were used to examine differences in peak AT stress, strain, strain rate and ankle dorsiflexion (α = .05).RESULTS: Peak AT stress and peak AT strain were greater at the fastest running speed when compared to the slowest speed (P<.001) and medium speed (P<.001), but speed had no impact on strain rate. Furthermore, participants used a greater ankle range of motion (ROM) during stance when running at a slow velocity compared to the fast (P = .006) and medium running speeds (P = .02).CONCLUSIONS: The reduced ankle excursion during stance at the faster running speed may contribute to the observed greater peak stress and strain on the AT. Altering running speed should be considered in those runners with a chronic AT injury.CLINICAL RELEVANCE: Manipulating running speed may be beneficial when determining appropriate progressions of training speed for a return to sport protocol following AT tendinopathy.SPO4Validation of a Clinical Screening Tool to Identify Anterior Cruciate Ligament (Acl) Risk in Adolescent Athletes During a 45° CutEryn K. Apanovitch, Monica Hurst, Elizabeth K. Chappell, Grant Smith, Daniel Lehnert, Alexa Martinez, Lauren Butler, Amie DeVerna, Cheryl Gimenez, Cristina Martorelli, Moataz Eltoukhy, Jeonghoon OhDepartment of Physical Therapy, University of Miami, Miami, Florida; Physical Therapy, Nicklaus Children's Hospital, Miami, Florida; Kinesiology and Sports Science, University of Miami, Miami, FloridaPURPOSE/HYPOTHESIS: ACL injuries are one of the most common injuries in adolescent athletes and cutting movements have been identified as a major cause of this injury. However, there is no clinical tool that screens for ACL injury risk during a cutting maneuver. The purpose of this study is to determine the validity of a qualitative checklist used to identify ACL injury risk in the clinic during a 45° sidestep cut.NUMBER OF SUBJECTS: Subjects were a convenience sample of 13 male and female athletes, ages 12 to 17, with no medically treated lower extremities injuries in the last 6 months, and no previous surgeries.MATERIALS/METHODS: The athletes were given specific instructions and asked to perform a 45° sidestep cut towards the right and left (3 trials of each) and 3 trials of a drop vertical jump (DVJ). An iPad was used to capture these maneuvers. Two experienced clinicians used an application (Dartfish) and a clinically established 45° cut qualitative checklist to score the cut and identify biomechanical risk factors. The same clinicians also evaluated biomechanical errors during the DVJ using the Landing Error Scoring System (LESS), a reliable and valid clinical assessment tool of jump landing biomechanics. Pearson correlation statistics were used to examine the relationship between the LESS and the total scores for the 45° cut items.RESULTS: There was no relationship between the LESS and the total cut score for the right lower extremity (P = .98, r = −0.0091), left lower extremity (P = .88, r = −0.045) or the total score for both legs (P = .93, r = −0.026).CONCLUSIONS: The findings of this pilot study suggest that qualitative analysis of a 45° sidestep cut, through use of a dichotomous check list, does not correlate to ACL injury risk level as identified during a drop vertical jump through use of the LESS. The results of this study are consistent with previous works suggesting that DVJ tests cannot predict loading of the knee during side step cutting tasks and that there is a poor correlation between frontal plane measures in drop jumps and unanticipated cutting. Previous works have shown a correlation between several 45° cut performance variables and knee abduction moments. Further data analysis will be performed to determine if there is a relationship between the 45° sidestep cut checklist scores and knee abduction moments to determine if this is a valid tool to identify high knee abduction moments and ACL injury risk.CLINICAL RELEVANCE: Despite the high percentage of ACL injuries that occur during a cutting task, there is no validated clinical measure to assess cutting injury risk factors. If the scores identified through use of the 45° sidestep cut qualitative checklist are found to correlate with knee abduction moments, this may prove to be a valuable clinician friendly tool for identifying injury risk during cutting tasks. The results of this pilot study support current evidence that injury risk evaluated during a DVJ cannot predict injury risk during a cutting task.SPO5Description and Comparison of Preseason and Postseason Blood Pressure Measures among Collegiate AthletesSara Arena, Lauren LaBelle, Jennifer Larsen, Lia M. Palomino, Tamara Hew-ButlerPhysical Therapy, Oakland University, Rochester, Michigan; Exercise Science, Oakland University, Rochester, MichiganPURPOSE/HYPOTHESIS: Growing evidence suggests prevalence of suboptimal blood pressure (BP) measures among professional athletes parallel rates among the nonathlete population; however, limited evidence specific to BP measures among collegiate athletes has been reported. Therefore, the purpose of this study is to describe and compare pre and postseason BP measures among collegiate athletes of varied sports and sexes.NUMBER OF SUBJECTS: Seventy-four collegiate athletes.MATERIALS/METHODS: After obtaining Institutional Review Board approval, National Collegiate Athletic Association (NCAA) athletes from the men's soccer, women's volleyball, men's and women's cross country and men's and women's swimming of 1 Division I university were invited to participate in a prospective observational study using a sample of convenience. Resting BP in both upper extremities was obtained preseason and at a 3- to 4-month follow-up (postseason) using evidenced based methodology. Additionally, BP measures were classified as normal, prehypertensive (PHTN) or hypertensive (HTN) using The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure criteria. Descriptive statistics provided analysis of athlete demographics, BP measures and BP classifications. A pairwise t test determined differences in pre and postseason BP measures by sport and sex. Statistical significance was set at P≤.05.RESULTS: Preseason BP assessment found 81.1% (n = 60) of athletes met the criterion of a normal BP; whereas 17.6% (n = 13) and 1.4% (n = 1) had PHTN and HTN measures, respectively. Results of postseason BP assessment was as follows; 56.8% (n = 42) with normal BP measures, 41.9% (n = 31) with PHTN BP measures and 1.4% (n = 1) with a HTN BP measure. During the competitive season 24% (n = 18) of athletes converted from a normal to a PHTN measure and an athlete with HTN BP measures during the preseason assessment continued to have the HTN BP measure postseason. Right (R) and left (L) systolic and diastolic BP measures demonstrated statistically significant increases (P = .001) from pre to postseason among all sports. Furthermore, pre and postseason systolic BP measures were significantly higher in male athletes compared to female athletes (R preseason and postseason, P = .001; L preseason, P = .0002 and L postseason, P = .024). Although not statistically significant, higher mean systolic and diastolic BP measures were identified in both men's soccer and men's cross country when compared to other sports.CONCLUSIONS: This study identified collegiate athletes with pre and post season PHTN and HTN BP measures. While statistically significant increases in pre and postseason BP measures among all sport teams and in men compared to women were detected, causative factors for this observation requires further examination.CLINICAL RELEVANCE: Findings of this study support routine BP assessment by health care providers serving the collegiate athlete population.SPO6Injury Incidence in Athletes Returning to Professional Soccer After ACL ReconstructionAmelia J. Arundale, Holly J. Silvers-Granelli, Lynn Snyder-MacklerBiomechanics and Movement Science, University of Delaware, Newark, Delaware; Department of Physical Therapy, University of Delaware, Newark, DelawarePURPOSE/HYPOTHESIS: The purpose of this study was to examine the incidence of lower extremity injuries, muscle/tendon injuries, particularly thigh muscle injuries, and the mean time-loss due to injury in athletes who have returned to professional soccer after anterior cruciate ligament reconstruction (ACLR). The authors hypothesized that athletes returning to sport after ACLR will have a higher injury incidence and greater time loss than controls.NUMBER OF SUBJECTS: Athletes participating in Major League Soccer (MLS) from January 2011 to March 2016 were eligible. All athletes with a history of ACLR were identified through injury records.MATERIALS/METHODS: This was a retrospective matched cohort study, with 1:1 matching based on age [1,2]. ACLR athletes were followed to the end of their MLS career or for 2 years after their return to play, whichever occurred first. The corresponding controls were followed for the same period. Exposure and injuries were recorded by team athletic trainers. Incidence rates (IR) were calculated per 1000 athletic exposures (AEs) for all lower extremity injuries [3,4], time-loss lower extremity injuries, muscle/tendon injuries [5], and thigh muscle injuries. A generalized linear model regression with Tweedie distribution and logit link function was used to calculate the relative risk ratios (RR) and 95% confidence intervals. Age was included in the model as a covariate. An independent t test was used to compare mean time-loss. Alpha was set a priori at P = .05.RESULTS: Twenty-four of 70 athletes returned to the MLS after ACLR. There was no difference between groups in age (P = .95). The ACLR group had a lower extremity injury IR = 22.7/1000 AEs compared to the control group IR = 20.7/1000 AEs (RR = 1.4; 95% CI: 0.7, 2.8; P = .31). The ACLR group had 70 time-loss lower extremity injuries (IR = 13.0/1000 AEs), the control group had 60 (IR = 10.4/1000 AEs; RR = 1.6; 95% CI: 0.8, 3.3; P = .21). The RR for muscle/tendon injuries was 1.69 (95% CI: 0.76, 3.78; P = .20) with the ACLR group IR = 9.3/1000 AEs and the control group IR = 5.5/1000 AEs. The RR for thigh injuries was 1.5 (95% CI: 0.59, 3.78; P = .39), with the ACLR group IR = 6.8/1000 AEs and the control group IR = 4.5/1000 AEs. The ACL reconstruction group had a mean 57 ± 83 days off due to injury, where the control group had a mean 37 ± 82, but this difference was not significant (P = .31).CONCLUSIONS: The return to sport rate (34%) in this cohort is very low compared to previous results from other professional men's soccer leagues [6,7]. Further investigation is warranted, as there may be a trend towards higher injury incidence rates in the ACLR group compared to the control group.CLINICAL RELEVANCE: A comprehensive understanding of the injury risks after ACLR and return to sport is crucial for educating athletes. These results indicate that rehabilitation must improve in order to allow more athletes to return to their preinjury level of sport as well as integrate secondary lower extremity injury prevention efforts.SPO7Subjective Reports of Fatigue Do Not Affect Cadence in Recreational RunnersJake AwenderPhysical Therapy, Fairview Health Services, Minneapolis, MinnesotaPURPOSE/HYPOTHESIS: To examine the effects of subjective reports of cardiovascular fatigue on knee kinematics and step frequency in recreational runners.NUMBER OF SUBJECTS: Twenty-two healthy recreational runners (13 female, 9 male) between the ages of 18 and 49 years without current knee or lower extremity pain, no history of surgery on either lower extremity, and no current or past cardiovascular illnesses.MATERIALS/METHODS: The primary investigator placed reflective markers at the greater trochanter, lateral knee joint line, and lateral malleolus. A slow motion camera was used to record each runner for 10 seconds “pre” and “post” volitional fatigue using a modified Astrand VO2max treadmill protocol. The Dartfish software was used by an independent assessor to compare pre and post results of knee kinematics and cadence.RESULTS: Maximum knee extension at initial contact (IC) was identical pre and post with a measurement of 6.9° (P = .917). Maximum knee extension at Toe Off (TO) was 13.9° pre versus 11.8° post (P = .003). Knee extension at midstance of the weight bearing extremity increased from 41.1° pre to 39.5° post (P = .207). The measurement for open chain flexion (OCF) of the swing leg was 89.8° pre, and increased to 93.3° post (P = .020). Comparing cadence between the 2 conditions, prefatigue was measured at 163.4 steps/min versus 163.1 steps/min post (P = .654).CONCLUSIONS: Only the TO and OCF measurements were found to have a statistically significant difference. IC, midstance, and cadence have all been shown to play an important role in oxygen consumption and energy absorption of the lower extremities while running, yet were not altered in the fatigued state of this experiment.CLINICAL RELEVANCE: Subjective assessment of fatigue may not play a role in altering lower extremity mechanics in healthy recreational runners, therefore it may not yield an additional clinical benefit to bring a runner to fatigue in order to assess their gait in a clinical setting. The absence of a significant change in IC, midstance, and cadence may suggest that volitional fatigue is not a risk factor for impact related overuse injuries in healthy recreational runners.SPO8Improving Limb Symmetry and Recovery Following Anterior Cruciate Ligament Reconstruction Surgery: Use of a Modified Wobble BoardFred Baldwin, Courtney Hatcher, Christy Conroy, Emily J. FoxMotion Analysis Center, Brooks Rehabilitation, St Johns, FloridaBACKGROUND AND PURPOSE: Following anterior cruciate ligament reconstruction (ACLR) surgery, athletes often develop movement compensations and limb asymmetry. During high-level activities such as jump landings, limb asymmetries are magnified, increasing the risk of injury in athletes. Use of a modified wobble board (MWB), with posting added to one side, may be a low-cost approach to encourage loading on the involved limb while limiting uninvolved limb compensations during exercise. This approach may improve limb symmetry and outcomes for athletes but the feasibility and outcomes have not been reported. The purpose of this case report is to describe the use of the MWB to improve limb symmetry by evaluating lower extremity kinematics and loading during functional movement tasks pre and postintervention for an individual post ACLR.CASE DESCRIPTION: A 21-year-old woman, 16 weeks post-ACLR surgery, was evaluated using 3 dimensional kinematics and vertical ground reaction forces (vGRF) during 5 repetitions of each task: Overhead squat, Drop vertical jump, Single-leg land, Lateral step down. Kinematic and loading asymmetries were calculated using a symmetry index (SI) seen in Eq 1 and 2 where a higher value indicates less symmetry: SI = |Joint AngleR — Joint AngleL| (Eq 1) and SI = (vGRFR — vGRFL)/0.5(Vgrfr + vGRFL) × 100% (Eq 2). The individual completed 10 intervention sessions using the MWB during squatting with her involved leg on the posted side (3 sets, 10–15 repetitions). Reassessment was performed 26 weeks postsurgery and the SI values were compared. In a separate test session, load distribution on the MWB was assessed using pressure sensors placed under each leg during squatting (6 repetitions). The amount of pressure applied through each lower extremity was calculated and compared.OUTCOMES: After 10 intervention sessions using the MWB and 26 weeks post-ACLR surgery, the individual demonstrated improved symmetry in hip internal rotation during all tasks: Overhead squat (pre-SI, 22.6°; post-SI, 5.60°), Drop vertical jump (pre-SI, 22.6°; post-SI, 9.23°), Single-leg land (pre-SI, 17.3°; post-SI, 7.44°), Lateral step down (pre-SI, 16.9°; post-SI, 14.2°). The vGRFs during both landing tasks also showed increased symmetry postintervention: Drop vertical jump (pre-SI, 53.2%; post-SI, 17.8%), Single-leg land (pre-SI, 28.8%; post-SI, 2.09%). Separate testing of the MWB displayed a 17% increase in weight distribution on the posted side as compared to the nonposted side, confirming that squatting on the MWB may increase weight shift toward the desired leg.DISCUSSION: The outcomes from this case suggest the potential benefit of using the MWB to improve limb symmetry in athletes who have difficulty loading their involved leg. The MWB may be a feasible approach for addressing asymmetry during athletic movements and reducing the risk of reinjury. The MWB should be evaluated further to gain insight into the effectiveness of this intervention.REFERENCES: 1. Paterno M, Ford K, Myer G, Heyl R, Hewett T. Limb asymmetries in landing and jumping 2 years following anterior cruciate ligament reconstruction. Clin J Sports Med. 2007;17:258–262. 2. Paterno M, Schmitt L, Ford K, Rauh M, Myer G, Huang B, Hewett T. Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport. Am J Sports Med. 2010. 3. Logerstedt D, Lynch A, Axe M, Snyder-Mackler L. Symmetry restoration and functional recovery before and after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2013; 21:859–868. 4. Sandford B, Williams J, Zucker-Levin A, Mihalko W. Asymmetric ground reaction forces and knee kinematics during squat after anterior cruciate ligament (ACL) reconstruction. Knee. 2016. 5. Hadizadeh M, Amri SB, Mohafez H, Ahmad SR, Mokhtar AHB. Gait analysis of national athletes after anterior cruciate ligament reconstruction following three stages of rehabilitation program: symmetrical perspective. Gait Posture. 2016.SPO9Limb Asymmetry in Landing Knee Mechanics is Associated with Isokinetic Quadriceps Strength, Not Degree of Voluntary ActivationTyler S. Balfour, Caroline R. Waters, Brian L. Talley, Katelyn N. Corbin, Ravi G. Patel, Jason Y. Kawamura, Liang-Ching TsaiPhysical Therapy, Georgia State University, Atlanta, GeorgiaPURPOSE/HYPOTHESIS: Diminished quadriceps function is often associated with altered knee mechanics, particularly in persons with knee injuries. The function of the quadriceps muscles (eg, strength, degree of activation) can be evaluated under different testing conditions (eg, isometric, isokinetic). Which quadriceps functional measurements are better indicators of altered knee mechanics remains unknown. This study examined the association of limb asymmetry in landing knee mechanics with asymmetry in quadriceps function quantified using isometric/isokinetic strength and degree of voluntary activation.NUMBER OF SUBJECTS: Fourteen.MATERIALS/METHODS: Seven males (mean ± SD age, 25.7 ± 2.8 years; weight, 77.5 ± 15.0 kg; height, 178.1 ± 10.0 cm) and 7 females (age, 23.9 ± 1.7 years; weight, 62.7 ± 6.9 kg; height, 170.5 ± 8.2 cm) with no history of lower extremity injury participated. Lower extremity kinematics and kinetics were recorded while participants performed a single-leg drop-land task. Peak knee angles and net moments (normalized to body mass) in all 3 planes during landing were calculated for both legs. Quadriceps function was evaluated using a dynamometer under an isometric (at 60° of knee flexion) twitch interpolation protocol and under 2 isokinetic conditions (60°/s and 180°/s; from 90° to 0° of knee flexion). Peak strength (isometric and isokinetic) and degree of voluntary activation of the quadriceps muscles were then determined. The association of limb asymmetry (nondominant versus dominant) in each knee kinematic/kinetic variable with the limb asymmetry in each quadriceps functional measurement was evaluated using Pearson correlation coefficient.RESULTS: Limb asymmetry in peak knee extensor moment was associated with that in peak isometric strength (r = −0.595, P = .025) and isokinetic strength at 60°/s (r = −0.562, P = .037). Peak knee valgus angle was associated with peak isokinetic strength at 60°/s (r = −0.594, P = .025) and 180°/s (r = −0.607, P = .021). Peak valgus moment also was associated with peak isokinetic strength at 60°/s (r = −0.573, P = .032) and 180°/s (r = −0.559, P = .038).CONCLUSIONS: Our data reveal several moderate correlations between limb asymmetry in landing knee mechanics and asymmetry in the quadriceps strength, particularly when evaluated under an isokinetic condition. The degree of voluntary activation was not associated with landing knee mechanics. Given our cross sectional design, causal relationships between quadriceps strength and knee mechanics cannot be established. Future studies involving a larger sample and assessment of muscle morphology (another factor determining muscle function) will provide a more complete picture of the association between quadriceps function and kn