Journal of Sport Rehabilitation

Published by Human Kinetics
Online ISSN: 1543-3072
Publications
Transcranial magnetic stimulation setup for testing the vastus medialis oblique. The lateral femoral condyle was aligned with the axis of rotation on the movement arm of the dynamometer, with the knee flexed to 90°. The shank of the leg was then secured to the arm of the Biodex just proximal to the medial and lateral malleoli with a padded strap. 
Transcranial magnetic stimulation setup for testing the fibularis longus. The knee was placed in 10° of flexion, with the ankle in 10° of plantar flexion. The plantar surface of the foot was placed on a foot-plate attachment with a heel cup used to secure the calcaneus, with the foot secured using a strap over the dorsal midfoot. 
Significant lines of best fit for the dominant fibularis longus muscle. 
Article
Alterations in corticomotor excitability are observed in a variety of patient populations, including the musculature surrounding the knee and ankle following joint injury. Active motor threshold (AMT) and motor evoked potential amplitudes (MEPs) elicited through transcranial magnetic stimulation (TMS) are outcomes measures used to assess corticomotor excitability, and have been deemed reliable in upper extremity musculature. However, there are few studies assessing the reliability of TMS measures in lower extremity musculature. Determine the intersession reliability of AMT and MEP amplitudes over 14 and 28 days in the quadriceps and fibularis longus (FL). Descriptive Laboratory Study. University Laboratory PARTICIPANTS: 20 able-bodied volunteers (10M/10F; 22.35 ± 2.3 years; 1.71 ± 0.11m; 73.61 ± 16.77kg). AMT and MEP amplitudes were evaluated at 95, 100, 105, 110, 120, 130, and 140% of AMT in the dominant and non-dominant quadriceps and FL. Interclass Correlation Coefficients (ICCs) were used to assess reliability for absolute agreement and internal consistency between baseline and two follow-up sessions at 14 and 28 days post baseline. Each ICC was fit with the best-fit straight-line or parabola in order to smooth out noise in the observations and best determine if a pattern existed in determining the most reliable MEP value. All muscles yielded strong ICCs between baseline and both time points for AMT. MEPs in both the quadriceps and FL produced varying degrees of reliability, with the greatest reliability demonstrated on day 28 at 130 and 140% of AMT in the quadriceps and FL, respectively. The dominant FL muscle showed a significant pattern as TMS intensity increased MEP reliability increased. TMS can be used to reliably identify corticomotor alterations following therapeutic interventions as well as monitor disease progression.
 
Article
The postgenomic era and heightened public expectations for tangible improvements in the public health have stimulated a complete transformation of the nation's biomedical research enterprise. The National Institutes of Health (NIH) "Roadmap for Medical Research" has catalyzed this transformation. The NIH roadmap consists of several interrelated initiatives, of which the Clinical and Translational Science Award (CTSA) program is the most relevant for rehabilitation specialists. This article reviews the evolution of this transformation and highlights the unprecedented opportunities the CTSA program provides rehabilitation specialists to play leadership roles in improving the clinical care of their patients.
 
— The cocking-simulation device allows passive external rotation and active internal rotation by stabilizing the elbow in the rotating unit with the shoulder at 90° abduction. By dropping a 3-kg weight connected with the rotational unit through a rope, rotational torque was generated for passive external rotation and to simulate the late cocking phase of a throwing activity. 
— A subject is positioned in the fluoroscopic unit with his elbow stabilized with the rotating unit of the cocking- simulation device. The plane of the scapula was perpendicular to the X-ray beam. 
— Anatomic coordinate systems of the scapula and humerus were defined according to reported conventions. Posterior tilt of the scapula was defined as the arc of motion of the z -axis of the scapula on the sagittal plane, upward rotation as the arc of the x -axis of the scapula on the frontal plane, and external rotation as the arc of the x -axis of the scapula on the horizontal plane. 
— A 3D-to-2D registration procedure was performed using JointTrack software. 
Scapular kinematics during simulated throwing motion: (A) upward rotation, (B) posterior tilting, and (C) external rotation. To minimize the effects of postural variation among the subjects, scapular orientation at the starting position (shoulder 0° internal rotation at 90° abduction) was defined as 0° in posterior tilt and external rotation. Scapular external rotation in the throwing shoulder was significantly smaller in the late cocking phase. Values are mean and 95% confidence interval in degrees.
Article
Abnormal scapular kinematics during throwing motion in baseball players with shoulder disorders has not yet been clarified, although altered scapular position has been suggested to be associated with shoulder disorder. The purpose of this study was to determine if the shoulders of baseball players with throwing disorders demonstrate abnormal scapular kinematics during the simulated arm cocking phase of throwing activity. Cross-sectional study. Laboratory. Eleven baseball players (age: 21.1±1.2 years) with a unilateral shoulder disorder volunteered to participate, including nine players at the collegiate level and two at the adult level. The mean playing experience was 12.1±2.7 years. Scapular upward/downward rotation, posterior/anterior tilting, and external/internal rotation during simulated arm cocking motion were analyzed using a 3D-to-2D registration technique. Scapular external rotation in the throwing shoulder was significantly smaller by 2.0-6.0° compared with that of the contralateral shoulder. There were no detectable differences in scapular upward-downward rotation or anterior-posterior tilting between the throwing and contralateral shoulders. Compared to that in the contralateral shoulder, scapular external rotation was smaller in the throwing shoulders, which would increase the glenohumeral horizontal abduction during the arm cocking phase and be related to the throwing shoulder disorder.
 
Demographic Characteristics of the Sample (N = 17) 
Changes in Blood Flow Over 20 min by Treatment Condition 
Comparison of Maximum Wrist-Extension Strength 20, 25, and 30 min After Baseline Wrist Extension (lb) 
Article
Soft-tissue injuries are commonly treated with ice or menthol gels. Few studies have compared the effects of these treatments on blood flow and muscle strength. To compare blood flow and muscle strength in the forearm after an application of ice or menthol gel or no treatment. Repeated measures design in which blood-flow and muscle-strength data were collected from subjects under 3 treatment conditions. Exercise physiology laboratory. 17 healthy adults with no impediment to the blood flow or strength in their right arm, recruited through word of mouth. Three separate treatment conditions were randomly applied topically to the right forearm: no treatment, 0.5 kg of ice, or 3.5 mL of 3.5% menthol gel. To avoid injury ice was only applied for 20 min. At each data-collection session blood flow (mL/min) of the right radial artery was determined at baseline before any treatment and then at 5, 10, 15, and 20 min after treatment using Doppler ultrasound. Muscle strength was assessed as maximum isokinetic flexion and extension of the wrist at 30°/s 20, 25, and 30 min after treatment. The menthol gel reduced (-42%, P < .05) blood flow in the radial artery 5 min after application but not at 10, 15, or 20 min after application. Ice reduced (-48%, P < .05) blood flow in the radial artery only after 20 min of application. After 15 min of the control condition blood flow increased (83%, P < .05) from baseline measures. After the removal of ice, wrist-extension strength did not increase per repeated strength assessment as it did during the control condition (9-11%, P < .05) and menthol-gel intervention (8%, P < .05). Menthol has a fast-acting, short-lived effect of reducing blood flow. Ice reduces blood flow after a prolonged duration. Muscle strength appears to be inhibited after ice application.
 
Article
Valid patient-based outcome instruments are necessary for comprehensive patient care that focuses on all aspects of health, from impairments to participation restrictions. To validate the Slovenian translation of Medical Outcome Survey (MOS) Short Form Health Survey (SF-36) and to assess relations among various knee measurements, activity tested with Oxford Knee Score (OKS) and health-related quality of life as estimated with SF-36 domains. Descriptive validation study. Isokinetic laboratory in outpatient rehabilitation unit. 101 subjects after unilateral sport knee injury. All subjects completed the SF-36 and OKS, and isokinetic knee-muscle strength output at 60°/s was determined in 78 participants. Within a 3-d period, 43 subjects completed the SF-36 and OKS questionnaires again. Reliability testing included internal consistency and test-retest reliability. Correlations between SF-36 subscales and OKS were calculated to assess construct validity, and correlation between SF-36 subscales and muscle strength was calculated to assess concurrent validity. Chronbach α was above .78 for all SF-36 subscales. ICCs ranged from .80 to .93. The correlation between OKS and the physical-functioning subscale, showing convergent construct validity, was higher (r = .83, P < .01) than between OKS and mental health (r = .50, P < .01), showing divergent construct validity. Knee-extensor weakness negatively correlated with physical-functioning (r = -.59, P < .01) and social-functioning (r = -.43, P < .01) subscales. The Slovenian translation of the SF-36 is a reliable and valuable tool. The relationships between knee-muscle strength and activity and between knee-muscle strength and SF-36 subscales in patients after sport knee injury were established.
 
Article
Lower extremity injury is prevalent among individuals participating in sports. Numerous variables have been reported as predisposing risk factors to injury; however, the effects of muscle fatigue on landing kinetics are unclear. To investigate the effects of a single session of repeated muscle fatigue on peak vertical ground-reaction force (GRF) during drop landings. Mixed factorial with repeated measures. Controlled laboratory. 10 female and 10 male healthy recreational athletes. Subjects performed 3 fatigued drop landings (60 cm) after four 20-s Wingate anaerobic tests (WATs) with 5 min of active recovery between fatigued conditions. Kinetic data of peak forefoot (F1) force, peak rear-foot (F2) force, and anteroposterior (AP) and mediolateral (ML) forces at both F1 and F2. A significant main effect was observed in the nonfatigued and fatigued drop landings in respect to peak F2 force. The greatest significant difference was shown between the first fatigued drop-landing condition and the last fatigued drop-landing condition. No significant difference was observed between genders for all GRF variables across fatigue conditions. A single session of repeated conditions of anaerobic muscle fatigue induced by WATs caused an initial reduction in peak F2 force followed by an increase in peak F2 force across conditions. Muscle fatigue consequently alters landing kinetics, potentially increasing the risk of injury.
 
Article
CONTEXT: Hamstring muscle length is commonly measured because of its perceived relationship to injury of both the hamstrings themselves and also the pelvis and lumbar spine. The popliteal (knee extension) angle measured from the starting position hip and knee at 90° is a commonly used indirect measure of hamstring muscle length. When this measure has been undertaken in the literature previously little attention has been paid to the position of the pelvis, which may significantly influence measurements taken. DESIGN: repeated measures SETTING: University Human Performance laboratory. PARTICIPANTS: 60 healthy physically active males (mean age 20.1+/-1.8 years, range 18-24 years). INTERVENTION: Effect of the two extremes of pelvic position (anterior and posterior) on hamstring muscle length (popliteal angle). MAIN OUTCOME MEASURE: Popliteal angle (with maximal knee extension) was measured in two positions one of full anterior and one of full posterior pelvic tilt. RESULTS: The mean difference in popliteal angle between anterior to posterior pelvic positions was 13.4+/-9° (range 0-26°) this was statistically significant (p=0.0001). CONCLUSION: The findings of the study indicate pelvic position has a significant effect on popliteal angle and therefore should be taken into account when measuring hamstring muscle length.
 
Article
Context Hamstring muscle length is commonly measured because of its perceived relationship to injury of both the hamstrings themselves and the pelvis and lumbar spine. The popliteal (knee-extension) angle measured from the starting position hip and knee at 90° is a commonly used indirect measure of hamstring muscle length. When this measure has been undertaken in the literature previously, little attention was paid to the position of the pelvis, which may significantly influence measurements taken. Design Repeated-measures. Setting University human performance laboratory. Participants 60 healthy physically active males (mean age 20.1 ± 1.8 y, range 18–24 y). Intervention The 2 extremes of pelvic position (anterior and posterior). Main Outcome Measure Popliteal angle (with maximal knee extension) was measured in 2 positions, 1 of full anterior and 1 of full posterior pelvic tilt. Results The mean difference in popliteal angle between anterior to posterior pelvic positions was 13.4° ± 9° (range 0–26°); this was statistically significant ( P = .0001). Conclusion The findings of the study indicate that pelvic position has a significant effect on popliteal angle and therefore should be taken into account when measuring hamstring muscle length.
 
— Location of symptoms.  
Patient Characteristics 
Examination Results for Patient 1 
— Modified Oswestry Disability Index scores.  
— Severity of pain during running.  
Article
Transient abdominal pain commonly occurs during running. There is limited information to guide the physical examination and treatment of individuals with this transient pain with running (TAPR). The purposes of this report are to describe the movement-system examination, diagnosis, and treatment of 2 female adolescent athletes with TAPR and highlight the differences in their treatment based on specific movement impairments. Case series. The movement diagnosis determined for both patients was thoracic flexion with rotation. The key signs and symptoms that supported this diagnosis included (1) alignment impairments of thoracic flexion and posterior sway and ribcage asymmetry; (2) movement impairments during testing and running of asymmetrical range of motion for trunk rotation, side bending, and flexion of the thoracic spine; and (3) reproduction of TAPR. Musculoskeletal impairments related to the trunk muscles combined with the mechanical stresses of running could contribute to TAPR. Treatment in each of the patients was focused on patient education regarding correction of alignment, muscle, and movement impairments of the extremities, thoracic spine, and ribcage. A strategy was determined for correcting motion during running to reduce or abolish the TAPR. Outcomes were positive in both patients. Differences in specific impairments in each patient demonstrate the need for specificity of treatment. These 2 patients illustrate how developing a movement diagnosis and identifying the contributing factors based on a systematic examination can be used in individuals with TAPR.
 
— Comparisons of electromyography (EMG) amplitude in abdominal muscles during abdominal hallowing and abdomi- nal bracing maneuver alone and with pelvic-floor-muscle contraction. IO indicates internal oblique; TA, transverse abdominis; EO, external oblique; AHM, abdominal hollowing maneuver; PFM, pelvic-floor muscle; ABM, abdominal bracing maneuver. 
Demographic Data of Healthy and Low-Back-Pain Groups
— Between-groups comparison of electromyography (EMG) amplitude in abdominal muscles during the abdominal hollow- ing maneuver alone and with pelvic-floor-muscle contraction. IO indicates internal oblique; TA, transverse abdominis; EO, external oblique; AHM, abdominal hollowing maneuver; PFM, pelvic-floor muscle; ABM, abdominal bracing maneuver; LBP, low back pain. 
Normalized EMG Amplitudes (mV) of the Abdominal Muscles During AHM Alone and With PFM for Healthy and Low-Back-Pain Groups
— Between-groups comparison of electromyography (EMG) amplitude in abdominal muscles during the abdominal brac- ing maneuver alone and with pelvic-floor-muscle contraction. IO indicates internal oblique; TA, transverse abdominis; EO, external oblique; AHM, abdominal hollowing maneuver; PFM, pelvic-floor muscle; ABM, abdominal bracing maneuver; LBP, low back pain. 
Article
Context: Coactivation of abdominal and pelvic-floor muscles (PFM) is an issue considered by researchers recently. Electromyography (EMG) studies have shown that the abdominal-muscle activity is a normal response to PFM activity, and increase in EMG activity of the PFM concomitant with abdominal-muscle contraction was also reported. Objective: The purpose of this study was to compare the changes in EMG activity of the deep abdominal muscles during abdominal-muscle contraction (abdominal hollowing and bracing) with and without concomitant PFM contraction in healthy and low-back-pain (LBP) subjects. Design: A 2 × 2 repeated-measures design. Setting: Laboratory. Participants: 30 subjects (15 with LBP, 15 without LBP). Main outcome measures: Peak rectified EMG of abdominal muscles. Results: No difference in EMG of abdominal muscles with and without concomitant PFM contraction in abdominal hollowing (P = .84) and abdominal bracing (P = .53). No difference in EMG signal of abdominal muscles with and without PFM contraction between LBP and healthy subjects in both abdominal hollowing (P = .88) and abdominal bracing (P = .98) maneuvers. Conclusion: Adding PFM contraction had no significant effect on abdominal-muscle contraction in subjects with and without LBP.
 
Article
Context: A normal breathing pattern while performing the abdominal-hollowing (AH) maneuver or spinal-stabilization exercise is essential for the success of rehabilitation programs and exercises. In previous studies, subjects were given standardized instructions to control the influence of respiration during the AH maneuver. However, the effect of breathing pattern on abdominal-muscle thickness during the AH maneuver has not been investigated. Objective: To compare abdominal-muscle thickness in subjects performing the AH maneuver under normal and abnormal breathing-pattern conditions and to investigate the effect of breathing pattern on the preferential contraction ratio (PCR) of the transverse abdominis. Design: Comparative, repeated-measures experimental study. Setting: University research laboratory. Participants: 16 healthy subjects (8 male, 8 female) from a university population. Measurement: A real-time ultrasound scanner was used to measure abdominal-muscle thickness during normal and abnormal breathing patterns. A paired t test was used to assess the effect of breathing pattern on abdominal-muscle thickness and PCR. Results: Muscle thickness in the transverse abdominis and internal oblique muscles was significantly greater under the normal breathing pattern than under the abnormal pattern (P < .05). The PCR of the transverse abdominis was significantly higher under the normal breathing pattern compared with the abnormal pattern (P < .05). Conclusion: The results indicate that a normal breathing pattern is essential for performance of an effective AH maneuver. Thus, clinicians should ensure that patients adopt a normal breathing pattern before performing the AH maneuver and monitor transverse abdominis activation during the maneuver.
 
Article
Individuals with low back pain (LBP) are thought to benefit from interventions that improve motor control of the lumbopelvic region. It is unknown if therapeutic exercise can acutely facilitate activation of lateral abdominal musculature. To investigate the ability of 2 types of bridging-exercise progressions to facilitate lateral abdominal muscles during an abdominal drawing-in maneuver (ADIM) in individuals with LBP. Randomized control trial. University research laboratory. 51 adults (mean ± SD age 23.1 ± 6.0 y, height 173.6 ± 10.5 cm, mass 74.7 ± 14.5 kg, and 64.7% female) with LBP. All participants met 3 of 4 criteria for stabilization-classification LBP or at least 6 best-fit criteria for stabilization classification. Participants were randomly assigned to either traditional-bridge progression or suspension-exercise-bridge progression, each with 4 levels of progressive difficulty. They performed 5 repetitions at each level and were progressed based on specific criteria. Muscle thickness of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) was measured during an ADIM using ultrasound imaging preintervention and postintervention. A contraction ratio (contracted thickness:resting thickness) of the EO, IO, and TrA was used to quantify changes in muscle thickness. There was not a significant increase in EO (F1,47 = 0.44, P = .51) or IO (F1,47 = .30, P = .59) contraction ratios after the exercise progression. There was a significant (F1,47 = 4.05, P = .05) group-by-time interaction wherein the traditional-bridge progression (pre = 1.55 ± 0.22; post = 1.65 ± 0.21) resulted in greater (P = .03) TrA contraction ratio after exercise than the suspension-exercise-bridge progression (pre = 1.61 ± 0.31; post = 1.58 ± 0.28). A single exercise progression did not acutely improve muscle thickness of the EO and IO. The magnitude of change in TrA muscle thickness after the traditional-bridging progression was less than the minimal detectable change, thus not clinically significant.
 
Article
The Bodyblade Pro is used for shoulder rehabilitation after injury. Resistance is provided by blade Oscillations-faster oscillations or higher speeds correspond to greater resistance. However, research supporting the Bodyblade Pro's use is scarce, particularly in comparison with dumbbell training. To compare muscle activity, using electromyography (EMG), in the back and shoulder regions during shoulder exercises with the Bodyblade Pro vs dumbbells. Randomized crossover study. San Diego State University biomechanics laboratory. 11 healthy male subjects age 19-32 y. Subjects performed shoulder-flexion and -abduction exercises using a Bodyblade Pro and dumbbells (5, 8, and 10 lb) while EMG recorded activity of the deltoid, pectoralis major, infraspinatus, serratus anterior, and erector spinae. Average peak muscle activity (% maximum voluntary isometric contraction) was separately measured for shoulder abduction and flexion in the range of 85° to 95°. Differences among exercise devices were separately analyzed for the flexed and abducted positions using 1-way repeated-measures ANOVA. The Bodyblade Pro produced greater muscle activity than all the dumbbell trials. Differences were significant for all muscles measured (all P < .01) except for the erector spinae during shoulder flexion with a 10-lb dumbbell. EMG activity for the Bodyblade Pro exceeded 50% of the MVIC during both shoulder flexion and abduction. For the dumbbell conditions, only the 10-lb trials approached this effect. Using a Bodyblade during shoulder exercises results in greater shoulder- and back-muscle recruitment than dumbbells. The Bodyblade Pro can activate multiple muscles in a single exercise and thereby minimize the need for multiple dumbbell exercises. The Bodyblade Pro is an effective device for shoulder- and back-muscle activation that warrants further use by clinicians interested in its use for rehabilitation.
 
— Example of method used to secure subject at the waist. 
— Example of dynamometer-head positioning. 
— Example of test being executed from frontal view. 
— Graphical representation of the relative hip strength of males and females. 
Article
Context: As high school female athletes demonstrate a rate of noncontact anterior cruciate ligament (ACL) injury 3-6 times higher than their male counterparts, research suggests that sagittal-plane hip strength plays a role in factors associated with ACL injuries. Objective: To determine if gender or age affect hip-abductor strength in a functional standing position in young female and male athletes. Design: Prospective cohort design. Setting: Biomechanical laboratory. Participants: Over a 3-y time period, 852 isokinetic hip-abduction evaluations were conducted on 351 (272 female, 79 male) adolescent soccer and basketball players. Intervention: Before testing, athletes were secured in a standing position, facing the dynamometer head, with a strap secured from the uninvolved side and extending around the waist just above the iliac crest. The dynamometer head was positioned in line with the body in the coronal plane by aligning the axis of rotation of the dynamometer with the center of hip rotation. Subjects performed 5 maximum-effort repetitions at a speed of 120°/s. The peak torque was recorded and normalized to body mass. All test trials were conducted by a single tester to limit potential interrater test error. Main outcome measure: Standing isokinetic hip-abduction torque. Results: Hip-abduction torque increased in both males and females with age (P < .001) on both the dominant and nondominant sides. A significant interaction of gender and age was observed (P < .001), which indicated that males experienced greater increases in peak torque relative to body weight than did females as they matured. Conclusions: Males exhibit a significant increase in normative hip-abduction strength, while females do not. Future study may determine if the absence of similar increased relative hip-abduction strength in adolescent females, as they age, may be related to their increased risk of ACL injury compared with males.
 
— Frontal hip-abduction exercise with neutral hip in side-lying. 
— Frontal hip-abduction exercise with hip medial rotation in side-lying. 
— Frontal hip-abduction exercise with hip lateral rotation in side-lying. 
— Comparison of muscle activity in the gluteus medius and the tensor fasciae latae among different hip rotations during side-lying hip-abduction (SHA) exercises. Abbreviations: SHA-N, SHA with neutral hip; SHA-MR, SHA with hip medial rotation; SHA-LR, SHA with hip lateral rotation. *Significant difference by Bonferroni adjustment ( P < .017). 
— Comparison of muscle-activity ratio in the gluteus medius (Gmed) and the tensor fasciae latae (TFL) among different hip rotations during side-lying hip abduction (SHA) exercises. Abbreviations: SHA-N, SHA with neutral hip; SHA-MR, SHA with hip medial rotation; SHA-LR, SHA with hip lateral rotation. *Significant difference by Bonferroni adjustment ( P < .017). 
Article
Context: Gluteus medius (Gmed) weakness is associated with some lower-extremity injuries. People with Gmed weakness might compensate by activating the tensor fasciae latae (TFL). Different hip rotations in the transverse plane may affect Gmed and TFL muscle activity during isometric side-lying hip abduction (SHA). Objectives: To compare Gmed and TFL muscle activity and the Gmed:TFL muscle-activity ratio during SHA exercise with 3 different hip rotations. Design: The effects of different hip rotations on Gmed, TFL, and the Gmed:TFL muscle-activity ratio during isometric SHA were analyzed with 1-way, repeated-measures analysis of variance. Setting: University research laboratory. Participants: 20 healthy university students were recruited in this study. Interventions: Participants performed isometric SHA: frontal SHA with neutral hip (frontal SHAN), frontal SHA with hip medial rotation (frontal SHA-MR), and frontal SHA with hip lateral rotation (frontal SHA-LR). Main outcome measures: Surface electromyography measured the activity of the Gmed and the TFL. A 1-way repeated-measures analysis of variance assessed the statistical significance of Gmed and TFL muscle activity. When there was a significant difference, a Bonferroni adjustment was performed. Results: Frontal SHA-MR showed significantly greater Gmed muscle activation than frontal SHA-N (P = .000) or frontal SHA-LR (P = .015). Frontal SHA-LR showed significantly greater TFL muscle activation than frontal SHA-N (P = .002). Frontal SHA-MR also resulted in a significantly greater Gmed:TFL muscle-activity ratio than frontal SHA-N (P = .004) or frontal SHA-LR (P = .000), and frontal SHA-N was significantly greater than frontal SHA-LR (P = .000). Conclusions: Frontal SHA-MR results in greater Gmed muscle activation and a higher Gmed:TFL muscle ratio.
 
Article
Individuals with a history of low back pain (LBP) may present with decreased hip abduction strength and increased trunk or gluteus maximus (GMax) fatigability. However, the effect of hip abduction exercise on hip muscle function has not been previously reported. To compare hip abduction torque and muscle activation of the hip, thigh and trunk between individuals with and without a history of LBP during repeated bouts of side-lying hip abduction exercise. Repeated Measures. Clinical Laboratory. 12 individuals with a history of LBP and 12 controls. Repeated thirty seconds hip abduction contractions. Hip abduction torque, normalized root-mean-squared (RMS) muscle activation, percent RMS muscle activation, and forward general linear regression. Hip abduction torque reduced in all participants as a result of exercise (1.57±0.36 Nm/kg, 1.12±0.36 Nm/kg, p<.001), but there were no group differences (F=0.129, p=.723) or group by time interactions (F=1.098, p=.358). All participants had increased GMax activation during the first bout of exercise (0.96±1.00, 1.18±1.03, p=.038). Individuals with a history of LBP had significantly greater GMax activation at multiple points during repeated exercise (p<.05), and a significantly lower percent of muscle activation for the GMax (p=.050) at the start of the third bout of exercise and biceps femoris (p=.039) at the end of exercise. The gluteal muscles best predicted hip abduction torque in controls, while no consistent muscles were identified for individuals with a history of LBP. Hip abduction torque decreased in all individuals following hip abduction exercise, although individuals with a history of LBP had increased GMax activation during exercise. Gluteal muscle activity explained hip abduction torque in healthy individuals, but not in those with a history of LBP. Alterations in hip muscle function may exist in individuals with a history of LBP.
 
Article
Standing and sidelying external rotation exercises produce high activation of the deltoid and infraspinatus. Slight shoulder abduction during these exercises may decrease deltoid activity and increase infraspinatus activity. To determine if the addition of a towel under the arm during standing and sidelying external rotation affects infraspinatus, middle and posterior deltoid, and pectoralis major activation characteristics, compared to the no towel condition. Controlled laboratory study. 20 male volunteers (age: 26 ± 3 yrs; height: 1.80 ± 0.07 m; mass: 77 ± 10 kg) who were right-hand dominant and had bilaterally healthy shoulders with no current cervical pathology, and no skin infection or shoulder lesion. External rotation exercises without a towel roll (0° shoulder abduction) and with a towel roll (30° shoulder abduction) were performed in a standing and sidelying position. Maximal voluntary isometric contraction for the infraspinatus, middle and posterior deltoid, and pectoralis major and external rotation in standing and sidelying with and without a towel roll were performed. Normalized average and peak surface EMG amplitude was compared between the towel conditions during standing and sidelying external rotation. Both infraspinatus and pectoralis major activity had no significant differences between the towel conditions in standing and sidelying (P > 0.05). In standing and sidelying, posterior deltoid activity was significantly greater with a towel roll (P < 0.05). Middle deltoid activity had no significant differences between the towel conditions in standing (P > 0.05). However, in sidelying, middle deltoid activity was significantly lower with a towel roll (P < 0.05). Middle deltoid activity decreased with a towel roll during sidelying exercises. More data are needed to determine if a towel roll could be used to potentially reduce superior glide during external rotation exercises.
 
Article
It has been theorized that a positive Trendelenburg test (TT) indicates weakness of the stance hip-abductor (HABD) musculature, results in contralateral pelvic drop, and represents impaired load transfer, which may contribute to low back pain. Few studies have tested whether weakness of the HABDs is directly related to the magnitude of pelvic drop (MPD). To examine the relationship between HABD strength and MPD during the static TT and during walking for patients with nonspecific low back pain (NSLBP) and healthy controls (CON). A secondary purpose was to examine this relationship in NSLBP after a 3-wk HABD-strengthening program. Quasi-experimental. Clinical research laboratory. 20 (10 NSLBP and 10 CON). HABD strengthening. Normalized HABD strength, MPD during TT, and maximal pelvic frontal-plane excursion during walking. At baseline, the NSLBP subjects were significantly weaker (31%; P = .03) than CON. No differences in maximal pelvic frontal-plane excursion (P = .72), right MPD (P = 1.00), or left MPD (P = .40) were measured between groups. During the static TT, nonsignificant correlations were found between left HABD strength and right MPD for NSLBP (r = -.32, P = .36) and CON (r = -.24, P = .48) and between right HABD strength and left MPD for NSLBP (r = -.24, P = .50) and CON (r = -.41, P = .22). Nonsignificant correlations were found between HABD strength and maximal pelvic frontal-plane excursion for NSLBP (r = -.04, P = .90) and CON (r = -.14, P = .68). After strengthening, NSLBP demonstrated significant increases in HABD strength (12%; P = .02), 48% reduction in pain, and no differences in MPD during static TT and maximal pelvic frontal-plane excursion compared with baseline. HABD strength was poorly correlated to MPD during the static TT and during walking in CON and NSLBP. The results suggest that HABD strength may not be the only contributing factor in controlling pelvic stability, and the static TT has limited use as a measure of HABD function.
 
Article
To determine if females with hip abductor weakness are more likely to demonstrate greater knee abduction during the stance phase of running than a strong hip abductor group. Observational prospective study design. University biomechanics laboratory. 15 females with weak hip abductors and 15 females with strong hip abductors. Group differences in lower extremity kinematics were analyzed using repeated measures ANOVA with one between factor of group and one within factor of position with a significance value of P < .05. The subjects with weak hip abductors demonstrated greater knee abduction during the stance phase of treadmill running than the strong group (P < .05). No other significant differences were found in the sagittal or frontal plane measurements of the hip, knee, or pelvis. Hip abductor weakness may influence knee abduction during the stance phase of running.
 
Article
It has been postulated that subjects with weak hip abductors and external rotators may demonstrate increased knee valgus, which may in turn raise risk of injury to the lower extremity. Recent studies have explored the potential link between hip strength and knee kinematics, but there has not yet been a review of this literature. To conduct a systematic review assessing the potential link between hip-abductor or external-rotator strength and knee-valgus kinematics during dynamic activities in asymptomatic subjects. An online computer search was conducted in early February 2011. Databases included Medline, EMBASE, CINAHL, SPORTDiscus, and Google Scholar. Inclusion criteria were English language, asymptomatic subjects, dynamometric hip-strength assessment, single or multicamera kinematic analysis, and statistical analysis of the link between hip strength and knee valgus via correlations or tests of differences. Data were extracted concerning subject characteristics, study design, strength measures, kinematic measures, subject tasks, and findings with regard to correlations or group differences. Eleven studies were selected for review, 4 of which found evidence that subjects with weak hip abductors or external rotators demonstrated increased knee valgus, and 1 study found a correlation to the contrary. There is a small amount of evidence that healthy subjects with weak hip abductors and perhaps weak external rotators demonstrate increased knee valgus. However, due to the variation in methodology and lack of agreement between studies, it is not possible to make any definitive conclusions or clinical recommendations based on the results of this review. Further research is needed.
 
Article
The overarching goal of this study was to examine the use of tri-axial accelerometers in measuring upper extremity motions to monitor upper extremity exercise compliance. There were multiple questions investigated but the primary objective was to investigate the correlation between visually observed arm motions and tri-axial accelerometer activity counts in order to establish fundamental activity counts for the upper extremity. Cross-sectional, Basic Research. Clinical Laboratory. Thirty healthy individuals age = 26 ± 6 years, body mass = 24 ± 3 kg, and height = 1.68 ± 0.09 m volunteered. Participants performed three series of tasks: 1) activities of daily living, 2) rehabilitation exercises 3) passive shoulder range of motion at 5 specific velocities on an isokinetic dynamometer while wearing an accelerometer on each wrist. Participants performed exercises with dominant arm to examine differences between sides. A researcher visually counted all arm motions in order to correlate counts with physical activity counts provided by the accelerometer. Physical activity counts derived from the accelerometer and visual observed activity counts recorded from a single investigator. There was a strong positive correlation (r=.93, p<0.01) between accelerometer physical activity counts and visual activity counts for all ADL's. Accelerometers activity counts demonstrated side to side difference for all ADL's (p<0.001) and 5 of the 7 rehabilitation activities (p<0.003). All velocities tested on the isokinetic dynamometer were shown to be significantly different from each other (p <0.001). There is a linear relationship between arm motions counted visually and the physical activity counts generated by an accelerometer indicating that arm motions could be potentially accounted for if monitoring arm usage. The accelerometers can detect differences in relatively slow arm movement velocities which is critical if attempting to evaluate exercise compliance during early phase of shoulder rehabilitation. These results provide fundamental information that indicates that tri-axial accelerometers have the potential to objectively monitor and measure arm activities during rehabilitation and activity of daily living.
 
— Fatigue protocol. 
Fatigue protocol.
Mean and SD of Static-and Dynamic-Balance Scores and Lactic Acid Concentrations
Article
This study sought to determine the effects of trunk-muscle fatigue and blood lactic acid elevation on static and dynamic balance. Fatigue was induced by an isokinetic protocol, and static and dynamic balance were assessed during bilateral stance using a Kinesthetic Ability Trainer. Subjects participated in a fatigue protocol in which continuous concentric movements at 60 degrees/s were performed until the torque output for both trunk flexion and extension dropped below 25% of the calculated peak torque for 3 consecutive movements. Before and immediately after the fatigue protocol, blood lactic acid measurements and static- and dynamic-balance measurements were recorded. An increase in lactic acid levels was detected in all subjects. According to a dependent-samples t test, significant differences in balance and lactic acid values were found after the fatigue protocol. There was no correlation between lactic acid accumulation (change between prefatigue and postfatigue levels) and balance-score differences. Trunk-muscle fatigue has an adverse effect on static and dynamic balance.
 
Cervical spine proprioception testing (a. headband-marker configuration and Frankfort Plane (black line), b. subject positioning, c. active rotation to target angle) 
Article
The cervical spine can be divided into upper and lower units, and each unit makes a different contribution to the magnitude of rotation and proprioception. However, few studies have examined the effect of the cervical rotation positions on proprioception. To compare cervical spine rotation active joint position sense (AJPS) near mid-range-of-motion (ROM) (30°) and near end-ROM (60°). Cross-sectional study. Human Performance Research Laboratory. Fifty-three military helicopter pilots (age = 28.4 ± 6.2 years, height = 175.3 ± 9.3 cm, weight = 80.1 ± 11.8 kg) consented and participated. A motion analysis system was used to record cervical rotation kinematics. Subjects sat in a chair wearing a headband and blind-fold. First, subjects actively rotated the head right or left to a target position (30°/60°) with real-time verbal cues provided by the tester. Subjects held the target position for five seconds and then returned to the start position. Following this, subjects replicated the target position as closely as possible. Five trials were performed in both directions to both target positions (R30/R60/L30/L60). Order of direction/position was randomized. The difference between target and replicated position was calculated and defined as absolute error (AE), the mean of five trials used for analyses. Wilcoxon Signed Ranks tests were used to compare AJPS at the different target positions (p<0.0125 with Bonferroni adjustments). End-ROM AE were significantly more accurate than mid-ROM AE (p = 0.001). Cervical spine rotation AJPS is more accurate near end-ROM versus mid-ROM. Both target positions should be used to examine cervical spine rotation AJPS of both the upper and lower units.
 
Summary of Study Designs of Articles Retrieved 
Characteristics of Included Studies 
Article
Clinical scenario: Injuries are somewhat commonplace in highly active populations. One strategy for reducing injuries is to identify individuals with an elevated injury risk before participation so that remediative interventions can be provided. Preparticipation screenings have traditionally entailed strength and flexibility measures thought to be indicative of inflated injury risk. Some researchers, however, have suggested that functional movements/tasks should be assessed to help identify individuals with a high risk of future injury. One assessment tool used for this purpose is the Functional Movement Screen (FMS). The FMS generates a numeric score based on performance attributes during 7 dynamic tasks; this score is purported to reflect future injury risk. Expanding interest in the FMS has led researchers to investigate how accurately it can identify individuals with an increased risk of injury. Focused clinical question: Can the Functional Movement Screen accurately identify highly active individuals with an elevated risk of injury?
 
Functional throwing-performance index (FTPI). OKC, open kinetic chain; CKC, closed kinetic chain; CS, core stability; CG, control group. 
Closed kinetic chain upper extremity (CKC UE) stability test. OKC, open kinetic chain; CKC, closed kinetic chain; CS, core stability; CG, control group. 
Core-Stability Training Program 
Reliability for Pretests and Posttests 
Article
With a limited number of outcomes-based studies, only recommendations for strength-training and rehabilitation programs can be made. To determine the extent to which throwing accuracy, core stability, and proprioception improved after completion of a 6-week training program that included open kinetic chain (OKC), closed kinetic chain (CKC), and/or core-stability exercises. A 2 x 3 factorial design. Division III college. 19 healthy baseball athletes with a control group of 15. Two 6-week programs including OKC, CKC, and core-stabilization exercises that were progressed each week. Functional throwing-performance index, closed kinetic chain upper extremity stability test, back-extensor test, 45 degrees abdominal-fatigue test, and right- and left-side bridging test. There was no significant difference between groups. An increase was evident in all pretest-to-posttest results, with improvement ranging from 1.36% to 140%. Both of the 6-week training programs could be used to increase throwing accuracy, core stability, and proprioception in baseball.
 
Article
Osteochondral defects are often symptomatic and lead to deranged joint function. The spontaneous healing capacity of osteochondral defects is limited. In the current case study, utilization of an acellular scaffold capable of induction of mesenchymal stem cell migration is described. This scaffold was used on an Outerbridge grade IV medical condylar defect measuring about 2 square centimetres. At 24 months follow-up, the articular surface appeared restored by MRI, and the patient returned to sports.
 
Article
Achilles tendinopathy is a common and often debilitating condition, and autologous blood injection is a promising treatment option. To determine whether autologous blood injection added to standard management was effective in alleviating symptoms of Achilles tendinopathy. A prospective randomized controlled trial. Private sports medicine clinic. 33 patients (18 women, 15 men) of mean age 50 y (SD 9) with 40 cases of Achilles tendinopathy of mean duration of 11 mo (SD 7). Participants were randomized to blind peritendinous autologous blood injection added to standard treatment (eccentric-loading exercises) or standard treatment alone for 12 wk. Victorian Institute of Sport Assessment for Achilles (VISA-A) score and ratings of discomfort during and after the injection were measured at baseline and 6 and 12 wk. Analytically derived effect-size thresholds of 5 (small) and 15 (moderate) VISA-A units were used as the reference values for clinical inference. Improvements in VISA-A of 7.7 units (95%CL: ± 6.7) and 8.7 units (± 8.8) were observed in the treatment and control groups, respectively, at 6 wk relative to baseline, with no clear effect of blood injection. At 12 wk VISA-A score improved to 18.9 units (± 7.4) in the treatment group, revealing a blood-injection effect of 9.6 units (± 11.5), relative to a comparatively unchanged condition in control (9.4 units; ± 9.0). Predictors of response to treatment were unremarkable, and a 21% rate of postinjection flare was the only noteworthy side effect. There is some evidence for small short-term symptomatic improvements with the addition of autologous blood injection to standard treatment for Achilles tendinopathy, although double-blinded studies with longer follow-up and larger sample size are required.
 
Article
Achilles tendon rupture is often the result of a long-term degenerative process, frequently occurring asymptomatically. To determine the prevalence of asymptomatic Achilles tendinopathy in an active, asymptomatic, young-adult population and to compare these findings across gender. Convenience sample, cohort study. Research laboratory A sample of 52 (28 male, 24 female) healthy, active subjects were recruited from the student body at the University of Connecticut. Images of 104 Achilles tendons were made. Ultrasound images made with a Phillips HD11 with a 15-MHz real-time linear-array transducer were collected on both the longitudinal and transverse axes of the Achilles tendon. Activity level was measured with the International Physical Activity Questionnaire Short Form (IPAQ-SF). Presence of ultrasound evidence of Achilles tendinopathy as agreed on by 2 blinded assessors highly skilled in ultrasonography. More subjects were categorized as highly active (57.4%) on the IPAQ-SF than moderately active (42.6%). One female and one male subject were found to have ultrasound evidence of asymptomatic Achilles tendinopathy, equaling 3.8% prevalence in this study. We found a low prevalence of asymptomatic Achilles tendinopathy in an active, young-adult population. Further work is necessary to identify an optimal group warranting ultrasound screening for asymptomatic tendinopathy.
 
Article
Chronic midportion Achilles tendinopathy is a common and hard-to-treat disorder characterized by degenerative changes of the tendon matrix. Ultrasonographic tissue characterization (UTC) was successfully used to quantify structural human Achilles tendon changes. This novel and reliable technique could be used in follow-up studies to relate tendon structure to symptoms. To quantify structural tendon changes and assess clinical change in patients with tendinopathy. Prospective observational study. Orthopedic department in a university medical center. 23 patients with chronic midportion Achilles tendinopathy. The patients performed a 16-wk home-based eccentric exercise program. An experienced researcher performed the ultrasonographic data collection with the UTC procedure. These data were assessed by a blinded observer. The severity of symptoms was established with the validated Victorian Institute of Sport Assessment-Achilles (VISA-A) questionnaire. UTC was performed to quantify tendon structure through measuring the proportion of 4 echo types. Echo types I and II represent more or less organized tendon bundles, and echo types III and IV represent disintegrated tendon structure. On the VISA-A, the total possible score is divided by 100 for a percentage score, with a perfect score of 100. Follow-up was at 2, 8, 16, and 24 wk. The mean percentage of echo types I and II changed by 0.3% after 24 wk (P = .92, 95% CI -5.8 to 5.3). The mean VISA-A score increased slightly but significantly by 11.3 points after 24 wk (P = .01, 95% CI 2.6-20.0). An increased VISA-A score was not correlated with an increased percentage of echo types I and II (P = .94, r = -.02), and the baseline percentage of echo types I and II did not correlate with an increased VISA-A score (P = .74, r = .07). There is no short-term increase in organized tendon structure after eccentric exercises. Tendon structure is not related to symptom severity and cannot be used as a predictor of clinical outcome.
 
Patient Characteristics 
The effect of 2 modes of rehabilitation conditioning after autologous chondrocyte implantation (experimental, nonconcurrent [N-CON], n = 7; control, concurrent [CON], n = 4) with contralateral limb as experimental control on peak force of the (A) knee extensors and (B) knee flexors, electromechanical delay of the (C) knee extensors and (D) knee flexors, and force error of the (E) knee extensors and (F) knee flexors, group mean ± SD. 
Article
Autologous chondrocyte implantation (ACI) aims to restore hyaline cartilage. Traditionally ACI rehabilitation is prescribed in a concurrent (CON) format However, it is well known from studies in asymptomatic populations that CON training produces an interference effect that can attenuate strength gains. Strength is integral to joint function, adopting a non-concurrent (N-CON) approach to ACI rehabilitation might improve outcomes. To assess changes in function and neuromuscular performance during 48 weeks of CON and N-CON physical rehabilitation following ACI to the knee. Orthopaedic Hospital NHS Foundation Trust. Randomised control; pilot study. Eleven patients (9 males, 2 females; age: 32.3 ± 6.6 yr; body mass: 79.3 ±10.4 kg; time from injury to surgery 7.1 ± 4.9 months [mean ± SD]) were randomly allocated to N-CON: CON (2:1). Standardised CON and N-CON physiotherapy that involved separation of strength and cardio-vascular endurance conditioning. Function [HOP], patient-reported outcomes [KOOS; IKDC] and neuromuscular outcomes of peak force [PF], rate of force development [RFD], electromechanical delay [EMD], and sensorimotor performance [force error, FE] of the knee extensors and flexors of the injured and non-injured legs; measured pre-surgery, and at 6, 12, 24 and 48 weeks post-surgery. Factorial ANOVAs with repeated-measures of group by leg and by test occasion revealed significantly superior improvements for KOOS, IKDC, PF, EMD and FE associated with N-CON vs. CON rehabilitation (F(1.5, 13.4GG) = 3.7 to 4.7; p<0.05). These results confirm increased effectiveness of N-CON rehabilitation (range ~ 4.5% - 13.3% better than CON between 12 and 48 weeks). N-CON and CON showed similar patterns of improvement for HOP and RFD. Non-concurrent strength and cardio-vascular endurance conditioning during 48 weeks of rehabilitation following ACI surgery elicited significantly greater improvements to functional and neuromuscular outcomes compared to contemporary concurrent rehabilitation.
 
Article
The Knee Self-Efficacy Scale (K-SES) has good reliability, validity, and responsiveness for patients' perceived knee-function self-efficacy during rehabilitation after an anterior cruciate ligament (ACL) injury. Preoperative knee-function self-efficacy has also been shown to have a predictive ability in terms of outcome 1 y after ACL reconstruction. To evaluate a new clinical rehabilitation model containing strategies to enhance knee-function self-efficacy. A randomized, controlled study. Rehabilitation clinic and laboratory. 40 patients with ACL injuries. All patients followed a standardized rehabilitation protocol. Patients in the experimental group were treated by 1 of 3 physiotherapists who had received specific training in a clinical rehabilitation model. These physiotherapists were also given their patients' self-efficacy scores after the initial and 4-, 6-, and 12-mo follow-ups, whereas the 5 physiotherapists treating the patients in the control group were not given their patients' self-efficacy scores. The K-SES, the Tegner Activity Scale, the Physical Activity Scale, the Knee Injury and Osteoarthritis Outcome Score, and the Multidimensional Health Locus of Control. Twenty-four patients (12 in each group) completed all follow-ups. Current knee-function self-efficacy, knee symptoms in sports, and knee quality of life improved significantly (P = .05) in both groups during rehabilitation. Both groups had a significantly (P = .05) lower physical activity level at 12 mo than preinjury. No significant differences were found between groups. In this study there was no evidence that the clinical rehabilitation model with strategies to enhance self-efficacy resulted in a better outcome than the rehabilitation protocol used for the control group.
 
— Ratings of perceived exertion throughout the exercise protocol were similar between groups. Abbreviations: ACL, anterior cruciate ligament. 
Subject Demographics
— Between-groups comparison of preexercise to postexercise change in quadriceps and soleus function. Abbreviations: CAR, central activation ratio; HM, H-reflex to M-wave ratio; VM, V-wave to M-wave ratio. *Significant difference between groups at baseline (P < .05). †Significant group × time interaction (P < .05). 
Article
PURPOSE: Persistent quadriceps weakness due to arthrogenic muscle inhibition (AMI) has been reported following ACL reconstruction. Fatiguing exercise has been shown to alter lower extremity muscle function and gait mechanics which may be related to injury risk. The effects of exercise on lower extremity function in the presence of AMI are not currently understood. The purpose of this study was to compare the effect of 30 minutes of exercise on quadriceps muscle function and soleus motor neuron pool excitability in ACL reconstructed participants and healthy controls. METHODS: 26 (13f, 13m) healthy and 26 (13f, 13m) ACL reconstructed recreationally active volunteers were recruited for a case control laboratory study. All participants completed 30 minutes of continuous exercise including alternating cycles of incline treadmill walking and bouts of squats and step-ups. Knee extension (MVIC) torque, quadriceps central activation ratio (CAR), soleus H:M ratio, and soleus V:M ratio were measured before and after 30 minutes of exercise. RESULTS: There was a significant group x time interaction for knee extension torque (P= .002), quadriceps CAR (P= .03), and soleus V:M ratio (P= .03). The effect of exercise was smaller for the ACL-R group when compared to matched controls for knee extension torque [ACL-R: %Δ= -4.2 (-8.7,0.3); Healthy: %Δ= -14.2 (-18.2,-10.2)], quadriceps CAR [ACL-R: %Δ= -5.1 (-8.0,-2.1); Healthy: %Δ= -10.0 (-13.3,-6.7)], and soleus VM ratio [ACL-R: %Δ= 37.6 (2.1,73.0); Healthy: %Δ= -24.9 (-38.6,-11.3)]. CONCLUSION: Declines in quadriceps and soleus volitional muscle function were of lower magnitude compared to healthy matched controls. This response suggests an adaption experienced by patients with quadriceps AMI that may act to maintain lower extremity function during prolonged exercise.
 
Article
In this study a numerical model of a skier was developed to investigate the effect of different rehabilitation strategies after anterior cruciate ligament (ACL) rupture. A computer model using a combined finite-element and multibody approach was established. The model includes a detailed representation of the knee structures, as well as all major leg muscles. Using this model, different strategies after ACL rupture were analyzed. The benefit of muscle training to compensate for a loss of the ACL was shown. The results indicate that an increase of 10% of the physiological cross-sectional area has a positive effect without subjecting other knee structures to critical loads. Simulating the use of a hamstring graft indicated increasing knee loads. A patellar-tendon graft resulted in an increase of the stress on the lateral collateral ligament. Muscle training of both extensors and flexors is beneficial in medical rehabilitation of ACL-deficient and ACL-reconstructed knees.
 
Summary of Study Designs of Articles Retrieved 
Characteristics of Included Studies 
Article
Clinical scenario: Anterior cruciate ligament (ACL) injuries are associated with a lengthy recovery time, decreased performance, and an increased rate of reinjury. To improve performance of the injured knee, affected athletes often undergo surgical reconstruction and rehabilitation. Determining when an athlete is ready to safely return to play (RTP), however, can be challenging for clinicians. Although various outcome measures have been recommended, their ability to predict a safe RTP is questionable. Focused clinical question: Which outcome measures should be used to determine readiness to return to play after ACL reconstruction?
 
Article
CONTEXT: As individuals returning to activity following anterior cruciate ligament reconstruction (ACLr) likely experience fatigue, understanding how fatigue impacts knee muscle activation patterns during sport-like maneuvers is of clinical importance. Fatigue has been suggested to impair neuromuscular control strategies. As a result, fatigue may place ACLr patients at increased risk for post-traumatic osteoarthritis (OA) development. OBJECTIVE: To determine the effects of fatigue on knee muscle activity post-ACLr. Design: Case-Control. SETTING: University Laboratory. PATIENTS OR OTHER PARTICIPANTS: Twelve individuals 7-10 months post-ACLr (7 male, 5 female; age 22.1±4.7years; 1.8±0.01m; mass 77.7±11.9kg) and thirteen controls (4 male, 9 female; age: 22.9±4.3years; 1.7±0.01m; mass 66.9±9.8kg). INTERVENTIONS: Fatigue was induced via repetitive sets of double-leg squats (N =8), which were interspersed with sets of single-leg landings (N =3), until squats were no longer possible. MAIN OUTCOME MEASURES: 2x2 repeated measures ANOVA was used to detect the main effects of group (ACLr, control) and fatigue state (pre-fatigue and post-fatigue) on quadriceps:hamstring co-contraction index (Q:H CCI). RESULTS: All subjects demonstrated higher Q:H CCI at pre-fatigue compared to post-fatigue (F1, 23=66.949, P≤0.001). Q:H CCI did not differ between groups (F1, 23=0.599, P=0.447). CONCLUSIONS: Our results indicate that regardless of fatigue state, ACLr individuals are capable of restoring muscle activation patterns similar to those in healthy subjects. As a result, excessive muscle co-contraction, which has been hypothesized as a potential mechanism of post-traumatic OA, may not contribute to joint degeneration following ACLr.
 
Participant Demographics 
Article
BACKGROUND: Disability is common in a proportion of patients following anterior cruciate ligament reconstruction (ACL-R). Neuromuscular quadriceps deficits are a hallmark impairment following ACL-R, yet the link between muscle function and disability are not understood. QUESTIONS/PURPOSES: Evaluate the ability of quadriceps strength and cortical excitability to predict self-reported disability in patients with ACL-R. METHODS: Fifteen participants with a history of ACL-R (11 Female, 4 Male; 172±9.8cm, 70.4±17.5, 54.4±40.9 months post surgery) were included in this study. Corticospinal excitability was assessed using active motor thresholds (AMT), while strength was assessed with maximal voluntary isometric contractions (MVIC). Both voluntary strength and corticospinal excitability were used to predict disability measured with the International Knee Documentation Committee Index (IKDC). RESULTS: The overall multiple regression model significantly predicted 66% of the variance in self-reported disability as measured by the IKDC index (R2 = 0.66, P=0.01). Initial imputation of MVIC into the model accounted for 61% (R2=0.61, P=0.01) of the variance in IKDC. The subsequent addition of AMT in the model accounted for an insignificant increase of 5% (Δ R2 = 0.05, P=0.19) in the prediction capability of the model. CONCLUSIONS: Quadriceps voluntary strength and cortical excitability predicted two-thirds of the variance in disability of patients with ACL-R; with strength accounting for virtually all of the predictive capability of the model.
 
Article
Context: Anterior cruciate ligament (ACL) reconstruction is the standard of care for individuals with ACL rupture. Balance deficits have been observed in patients with ACL reconstruction (ACLR) using advanced posturography, which is the current gold standard. It is unclear if postural-control deficits exist when assessed by the Balance Error Scoring System (BESS), which is a clinical assessment of balance. Objective: The purpose of this study is to determine if postural-control deficits are present in individuals with ACLR as measured by the BESS. Participants: Thirty participants were included in this study. Fifteen had a history of unilateral ACLR and were compared with 15 matched controls. Interventions: The BESS consists of 3 stances (double-limb, single-limb, and tandem) on 2 surfaces (firm and foam). Participants begin in each stance with hands on their hips and eyes closed while trying to stand as still as possible for 20 s. Main outcome measures: Each participant performed 3 trials of each stance (18 total), and errors were assessed during each trial and summed to create a total score. Results: We observed a significant group x stance interaction (P = .004) and a significant main effect for stance (P < .001). Post hoc analysis revealed that the ACLR group had worse balance on the single-leg foam stance than did controls. Finally, the reconstructed group had more errors when total BESS score was examined (P = .02). Conclusions: Balance deficits exist in individuals with ACLR as measured by the BESS. Total BESS score was different between groups. The only condition that differed between groups was the single-leg stance on the unstable foam surface.
 
Article
There is conflicting evidence in the literature regarding whether women with anterior cruciate ligament reconstruction (ACLR) demonstrate impaired proprioception. This study examined dynamic-position-sense accuracy and central-nervous-system (CNS) processing time between those with and without long-term ACLR. To compare proprioception of knee movement in women with ACLR and healthy controls. Cross-sectional. Human neuromuscular performance laboratory. 11 women (age 22.64 ± 2.4 y) with ACLR (1.6-5.8 y postsurgery) and 20 women without (age 24.05 ± 1.4 y). The authors evaluated subjects using 3 methods to assess position sense. During knee flexion at pseudorandomly selected speeds (40°, 60°, 80°, 90°, and 100°/s), subjects indicated with their index finger when their knee reached a predetermined target angle (50°). Accuracy was calculated as an error score. CNS processing time was computed using the time to detect movement and the minimum time of angle indication. Passive and active joint-position sense were also determined at a slow velocity (3°/s) from various knee-joint starting angles. Absolute and constant error of target angle, indication accuracy, CNS processing time, and perceived function. Both subject groups showed similar levels of error during dynamic-position-sense testing, despite continued differences in perceived knee function. Estimated CNS processing time was 260 ms for both groups. Joint-position sense during slow active or passive movement did not differ between cohorts. Control and ACLR subjects demonstrated similar dynamic, passive, and active joint-position-sense error and CNS processing speed even though ACLR subjects reported greater impairment of function. The impairment of proprioception is independent of post-ACLR perception of function.
 
– CAR effect sizes with 95% confidence intervals: Diamonds with solid error bars ( ) represent effect size point estimates for TENS interventions and 95% confidence intervals, whereas circles with broken lines ( ) represent effect size point estimates for cryotherapy and 95% confidence intervals. All point measures and confidence intervals on the right of the vertical solid line represents beneficial and statistically significant effects (confidence intervals do not cross 0), whereas the left of the line represents non-beneficial and statistically insignificant effects. 
Characteristics of Included Studies 
Treatment Guidelines for Facilitating Quadriceps Activation 
Article
Clinical Scenario Proper neuromuscular activation of the quadriceps muscle is essential for maintaining quadriceps (quad) strength and lower-extremity function. Quad activation (QA) failure is a common characteristic observed in patients with knee pathologies, defined as an inability to voluntarily activate the entire alpha-motor-neuron pool innervating the quad. One of the more popular techniques used to assess QA is the superimposed burst (SIB) technique, a force-based technique that uses a supramaximal, percutaneous electrical stimulation to activate all of the motor units in the quad during a maximal, voluntary isometric contraction. Central activation ratio (CAR) is the formula used to calculate QA level (CAR = voluntary force/SIB force) with the SIB technique. People who can voluntarily activate 95% or more (CAR = 0.95–1.0) of their motor units are defined as being fully activated. Therapeutic exercises aimed at improving quad strength in patients with knee pathologies are limited in their effectiveness due to a failure to fully activate the muscle. Within the past decade, several disinhibitory interventions have been introduced to treat QA failure in patients with knee pathologies. Transcutaneous electrical nerve stimulation (TENS) and cryotherapy are sensory-targeted modalities traditionally used to treat pain, but they have been shown to be 2 of the most successful treatments for increasing QA levels in patients with QA failure. Both modalities are hypothesized to positively affect voluntary QA by disinhibiting the motor-neuron pool of the quad. In essence, these modalities provide excitatory afferent stimuli to the spinal cord, which thereby overrides the inhibitory afferent signaling that arises from the involved joint. However, it remains unknown whether 1 is more effective than the other for restoring QA levels in patients with knee pathologies. By knowing the capabilities of each disinhibitory modality, clinicians can tailor treatments based on the rehabilitation goals of their patients. Focused Clinical Question Is TENS or cryotherapy the more effective disinhibitory modality for treating QA failure (quantified via CAR) in patients with knee pathologies?
 
Article
The gluteus medius (Gmed) is proposed to consist of 3 functional subdivisions (anterior, middle, and posterior). Gmed weakness and dysfunction have been implicated in numerous lower extremity disorders, including patellofemoral pain syndrome (PFPS). PFPS is a knee condition that frequently occurs in females and is associated with activities such as squatting and stair climbing. There is a lack of evidence for the role of the subdivisions of the Gmed in females with and without PFPS. To compare muscle activation in the 3 Gmed subdivisions during 4 weight-bearing exercises in women with and without PFPS. Single-session, repeated-measures observational study. University research laboratory. Convenience sample of 12 women with PFPS and 12 age- and gender-matched asymptomatic controls. Participants performed 4 weight-bearing exercises (wall press, pelvic drop, step-up-and-over, and unilateral squat) 3 times while surface electromyography (sEMG) activity of the Gmed segments was recorded. sEMG muscle activity for each functional subdivision of the Gmed during each weight-bearing exercise was analyzed using a mixed between-within-subjects ANOVA (post hoc Bonferroni). No statistically significant differences in muscle activation were found between the PFPS and healthy participants (P = .97). Furthermore, there were no statistically significant differences between the exercises (P = .19) or muscle fibers (P = .36) independent of group analyzed. However, the activation of the subdivisions varied according to the exercise performed (P = .003). Similar levels of muscle activation were recorded in the Gmed subdivisions of the PFPS and healthy participants during the different exercises. This is the first study to examine all 3 Gmed subdivisions in PFPS. Future studies using larger sample sizes should also investigate onset and duration of muscle activation in all Gmed subdivisions in both healthy individuals and those with PFPS.
 
Article
Weight-bearing (WB) and non-weight-bearing (NWB) exercises are commonly used in rehabilitation programs for patients with anterior knee pain (AKP). To determine the immediate effects of isolated WB or NWB knee-extension exercises on quadriceps torque output and activation in individuals with AKP. A single-blind randomized controlled trial. Laboratory. 30 subjects with self-reported AKP. Subjects performed a maximal voluntary isometric contraction (MVIC) of the quadriceps (knee at 90°). Maximal voluntary quadriceps activation was quantified using the central activation ratio (CAR): CAR = MVIC/(MVIC + superimposed burst torque). After baseline testing, subjects were randomized to 1 of 3 intervention groups: WB knee extension, NWB knee extension, or control. WB knee-extension exercise was performed as a sling-based exercise, and NWB knee-extension exercise was performed on the Biodex dynamometer. Exercises were performed in 3 sets of 5 repetitions at approximately 55% MVIC. Measurements were obtained at 4 times: baseline and immediately and 15 and 30 min postexercise. Quadriceps torque output (MVIC: N·m/Kg) and quadriceps activation (CAR). No significant differences in the maximal voluntary quadriceps torque output (F2,27 = 0.592, P = .56) or activation (F2,27 = 0.069, P = .93) were observed among the 3 treatment groups. WB and NWB knee-extension exercises did not acutely change quadriceps torque output or activation. It may be necessary to perform exercises over a number of sessions and incorporate other disinhibitory interventions (eg, cryotherapy) to observe acute changes in quadriceps torque and activation.
 
— Custom-made runway.  
Custom-made runway.
Results From the MANOVA Table
— Segment capable of dropping into 30° of inversion.  
EMG Data During Normal and Perturbed Gait
Article
Selected muscles in the kinetic chain may help explain the body's ability to avert injury during unexpected perturbation. To determine the activation of the ipsilateral rectus femoris (RF), gluteus maximus (MA), gluteus medius (ME), and contralateral external obliques (EO) during normal and perturbed gait. Single-factor, repeated measures. University research laboratory. 32 physically active, college-age subjects. Subjects walked a total of 20 trials the length of a 6.1-m custom runway capable of releasing either side into 30° of unexpected inversion. During 5 trials, the platform released into inversion. Average, peak, and time to peak EMG were analyzed across the 4 muscles, and comparisons were made between the walking trials and perturbed trials. Significantly higher average and peak muscle activity were noted for the perturbed condition for RF, MA, and EO. Time to peak muscle activity was faster during the perturbed condition for the EO. Rapid contractions of selected postural muscles in the kinetic chain help explain the body's reaction to unexpected perturbation.
 
— This figure illustrates the applied torque due to gravity onto the quadriceps during single leg stance with the knee fully extended and placed in 30 degrees of flexion. The vertical, solid line shows the force due to gravity. The horizontal, broken line represents the length of the external moment arm (perpendicular distance of the force due to gravity from the center of the knee joint) in each position. The external moment arm in the Figure on the left (A) is negligible because the subject’s center of mass is positioned over the knee joint. The external moment arm in the Figure on the right (B) is relatively greater because the subject’s center of mass is positioned posterior to the knee joint. This position created a greater knee flexion moment and required subjects to generate greater vastus medialis electromyographic activity to counteract the knee flexion moment. 
Article
Knee extension exercise is an important part of knee rehabilitation. Clinicians prescribe non-weight bearing exercise initially and progress patients to weight bearing exercise once they can perform a straight leg raise (SLR). Compare VM activation during a SLR and weight bearing exercises. One-way repeated measures design. Setting: University Laboratory. Fifteen healthy subjects. One SLR exercise and 6 weight-bearing knee extension exercises. Electromyographic amplitudes for the VM expressed as a percent maximum voluntary isometric contraction. The SLR had greater activation than the single leg stance and bilateral squat exercises. The step-up and unilateral leg press exercises had the greatest activation. SLR performance can be an important indicator for exercise progression. These results provide foundational knowledge to assist clinicians with exercise prescription.
 
Article
Functional subdivisions are proposed to exist in the gluteus medius (GM) muscle. Dysfunction of the GM, in particular its functional subdivisions, is commonly implicated in lower limb pathologies. However, there is a lack of empirical evidence examining the role of the subdivisions of the GM. To compare the activation of the functional subdivisions of the GM (anterior, middle, and posterior) during isometric hip contractions. Single-session, repeated-measures observational study. University research laboratory. Convenience sample of 15 healthy, pain-free subjects. Subjects performed 3 maximal voluntary isometric contractions for hip abduction and internal and external rotation on an isokinetic dynamometer with simultaneous recording of surface electromyography (sEMG) activity of the GM subdivisions. sEMG muscle activity for each functional subdivision of the GM during each hip movement was analyzed using a 1-way repeated-measures ANOVA (post hoc Bonferroni). The response of GM subdivisions during the 3 different isometric contractions was significantly different (interaction effect; P = .003). The anterior GM displayed significantly higher activation across all 3 isometric contractions than the middle and posterior subdivisions (main effect; both P < .001). The middle GM also demonstrated significantly higher activation than the posterior GM across all 3 isometric contractions (main effect; P = .027). There was also significantly higher activation of all 3 subdivisions during both abduction and internal rotation than during external rotation (main effect; both P < .001). The existence of functional subdivisions in the GM appears to be supported by the findings. Muscle activation was not homogeneous throughout the entire muscle. The highest GM activation was found in the anterior GM subdivision and during abduction and internal rotation. Future studies should examine the role of GM functional subdivisions in subjects with lower limb pathologies.
 
Article
Co-activation ratio of quadriceps to hamstring muscles (Q: H) and medial to lateral knee muscles (M: L) are important to contribute to the dynamic stability of the knee joint during movement patterns recommended during rehabilitation and important for daily function. To compare the quadriceps to hamstring and medial to lateral knee muscles' co-activation ratios between male and females during the following closed kinetic chain exercises which were performed on a balance board: forward lunge, side lunge, single leg stance, and single leg squat. Cross- sectional. Twenty healthy subjects (10 female and 10 male) participated in this study. Surface electromyography was used to measure the activation level of quadriceps (vastus lateralis and medialis) and hamstrings (biceps femoris and medial hamstrings) during forward and side lunge, single leg stance, and single leg squat exercises. Subjects were instructed during each exercise to move into the test position and to hold that position for 15 seconds. EMG was recorded during the 15 second isometric period where subjects tried to maintain a "set" position while the foot was on a balance board. Analysis of variance was used for statistical analysis. There was a significant exercise by gender interaction for Q:H ratio (F (3, 48) = 6.63, p=0.001) but the exercise by gender interaction for M:L ratio was not significant (F (3, 48) = 1.67, p=0.18). Females showed larger Q:H ratio in side lunge exercises than males (p=0.002). Both genders showed larger M:L and lower Q:H ratio in a single leg stance exercise when compared to the other exercises. Our results indicate that the forward and side lunge and single leg squat exercises should not be recommended as an exercise where a balanced co-activation between quadriceps and hamstring muscles is warranted. Single leg stance exercise could be used when seeking an exercise where the ratio is balanced for both females and males.
 
Article
Understanding how muscles activate in a population with a previous glenohumeral joint(GH) injury may help clinicians understand how to build a conservative treatment plan to strengthen or activate the specific muscles in an attempt to reduce recurrent shoulder injury and development of GH laxity. To investigate muscle activation differences between the previously injured limb of individuals with a history of glenohumeral joint injury and healthy, matched controls during functional isometric contractions. Case control. University research laboratory. 17 individuals (8 women, 9 men, age: 22.3±2.6 years, height: 172.4±8.8 cm, mass: 75.4±16.5 kg) with previous unilateral shoulder pain and 17 individuals (8 women, 9 men, age 22.9±3.9 years, height: 170.9±11.3 cm, mass: 73.6±22.9 kg) with no history of shoulder pain or injury. Diagnostic ultrasound (US) measurements of the supraspinatus were completed in both resting and contracted states to assess changes in muscle thickness. Manual muscle tests (anterior deltoid, upper trapezius, infraspinatus, lower trapezius, serratus anterior) and functional isometric contractions (forward flexion, scaption, abduction) were measured using electromyography (EMG) recordings. Peak, normalized activation of each muscle and supraspinatus thickness activation ratio were compared between groups and bilaterally within groups using separate ANOVAs. The anterior deltoid was significantly less activated during all functional isometric tasks in previously injured subjects compared to healthy subjects (P=0.024). In previously injured subjects, the involved limb lower trapezius was significantly less activated during scaption and abduction tasks compared to the contralateral side (P=0.022 and P=.031, respectively). There were decreases in muscle activation in the anterior deltoid between previously injured and healthy people as well as in the lower trapezius within a previously injured person. Understanding the source of muscle activation deficits can help clinicians focus rehabilitation exercises on specific muscles.
 
Article
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.
 
Article
Context: No published studies have compared muscle activation levels simultaneously for the gluteus maximus and medius muscles of stance and moving limbs during standing hip-joint strengthening while using elastic-tubing resistance. Objective: To quantify activation levels bilaterally of the gluteus maximus and medius during resisted lower-extremity standing exercises using elastic tubing for the cross-over, reverse cross-over, front-pull, and back-pull exercise conditions. Design: Repeated measures. Setting: Laboratory. Participants: 26 active and healthy people, 13 men (25 ± 3 y) and 13 women (24 ± 1 y). Intervention: Subjects completed 3 consecutive repetitions of lower-extremity exercises in random order. Main outcome measures: Surface electromyographic (EMG) signals were normalized to peak activity in the maximum voluntary isometric contraction (MVIC) trial and expressed as a percentage. Magnitudes of EMG recruitment were analyzed with a 2 × 4 repeated-measures ANOVA for each muscle (α = .05). Results: For the gluteus maximus an interaction between exercise and limb factor was significant (F3,75 = 21.5; P < .001). The moving-limb gluteus maximus was activated more than the stance limb's during the back-pull exercise (P < .001), and moving-limb gluteus maximus muscle recruitment was greater for the back-pull exercise than for the cross-over, reverse cross-over, and front-pull exercises (P < .001). For the gluteus medius an interaction between exercise and limb factor was significant (F3,75 = 3.7; P < .03). Gluteus medius muscle recruitment (% MVIC) was greater in the stance limb than moving limb when performing the front-pull exercise (P < .001). Moving-limb gluteus medius muscle recruitment was greater for the reverse cross-over exercise than for the cross-over, front-pull, and back-pull exercises (P < .001). Conclusions: From a clinical standpoint there is no therapeutic benefit to selectively activate the gluteus maximus and gluteus medius muscles on the stance limb by resisting sagittal- and frontal-plane hip movements on the moving limb using resistance supplied by elastic tubing.
 
Article
The Star Excursion Balance Test (SEBT) is often used to train and assess dynamic balance and neuromuscular control. Few studies have examined hip- and thigh-muscle activation during the SEBT. To quantify hip- and thigh-muscle activity during the SEBT. Repeated measures. Laboratory. 22 healthy individuals, 11 men and 11 women. EMG measurements were taken as participants completed 3 trials of the anterior (A), medial (M), and posteromedial (PM) reach directions of the SEBT. Mean EMG data (% maximal voluntary isometric contraction) from the gluteus medius (Gmed), gluteus maximus (Gmax), and vastus medialis (VM) were measured during the eccentric phase of each SEBT reach direction. Test-retest reliability of EMG data across the 3 trials in each direction was calculated. EMG data from each muscle were compared across the 3 reach directions. Test-retest reliability ranged from ICC3,1 values of .91 to .99. A 2-way repeated-measure ANOVA revealed a significant interaction between muscle activation and reach direction. One-way ANOVAs showed no difference in GMed activity between the A and M directions. GMed activity in the A and M directions was greater than in the PM direction. There was no difference in GMax and VM activity across the 3 directions. GMed was recruited most effectively when reaching was performed in the A and M directions. The A, M, and PM directions elicited similar patterns of muscle recruitment for the GMax and VM. During all 3 SEBT directions, VM activation exceeded the 40-60% threshold suggested for strengthening effects. GMed activity also exceeded the threshold in the M direction. GMax activation, however, was below the 40% threshold for all 3 reach directions, suggesting that performing dynamic lower extremity reaching in the A, M, and PM directions may not elicit strengthening effects for the GMax.
 
— Start position of the distal segments for the no- wedge condition. 
— Start position of the distal segments for the wedge condition. 
Average EMG (%MVIC) During the Descending Phase of the Squat for Each Condition, Mean ± SD (95% Confidence Interval)
Article
Limitations in gastrocnemius/soleus flexibility that restrict ankle dorsiflexion during dynamic tasks have been reported in individuals with patellofemoral pain (PFP) and are theorized to play a role in its development. To determine the effect of restricted ankle-dorsiflexion range of motion (ROM) on lower extremity kinematics and muscle activity (EMG) during a squat. The authors hypothesized that restricted ankle-dorsiflexion ROM would alter knee kinematics and lower extremity EMG during a squat. Cross-sectional. 30 healthy, recreationally active individuals without a history of lower extremity injury. Each participant performed 7 trials of a double-leg squat under 2 conditions: a no-wedge condition (NW) with the foot flat on the floor and a wedge condition (W) with a 12° forefoot angle to simulate reduced plantar-flexor flexibility. 3-dimensional hip and knee kinematics, medial knee displacement (MKD), and ankle-dorsiflexion angle. EMG of vastus medialis oblique (VMO), vastus lateralis (VL), lateral gastrocnemius (LG), and soleus (SOL). One-way repeated-measures ANOVAs were performed to determine differences between the W and NW conditions. Compared with the NW condition, the wedge produced decreased peak knee flexion (P < .001, effect size [ES] = 0.81) and knee-flexion excursion (P < .001, ES = 0.82) while producing increased peak ankle dorsiflexion (P = .006, ES = 0.31), ankle-dorsiflexion excursion (P < .001, ES = 0.31), peak knee-valgus angle (P = .02, ES = 0.21), and MKD (P < .001, ES = 2.92). During the W condition, VL (P = 0.002, ES = 0.33) and VMO (P = .049, ES = 0.20) activity decreased while soleus activity increased (P = .03, ES = 0.64) compared with the NW condition. No changes were seen in hip kinematics (P > .05). Altering ankle-dorsiflexion starting position during a double-leg squat resulted in increased knee valgus and MKD, as well as decreased quadriceps activation and increased soleus activation. These changes are similar to those seen in people with PFP.
 
Top-cited authors
Timothy E Hewett
  • Hewett Consultants - Rochester, Minneapolis
Gregory Myer
  • Emory University
Lee Herrington
  • University of Salford
Carl G Mattacola
  • University of North Carolina at Greensboro
Allan Munro
  • University of Salford