A Biomechanical Review of the Squat Exercise: Implications for Clinical Practice.

The squat is one of the most frequently prescribed exercises in the rehabilitative setting. Performance of the squat can be modified by changing parameters such as stance width, foot rotation, trunk position, tibia position, and depth. An understanding of how the various squatting techniques can influence joint loading and muscular demands is important for the proper prescription of this exercise for various clinical conditions. The purpose of this clinical commentary is to discuss how the biomechanical demands of the squat can be influenced by various modifiable parameters. General recommendations for specific clinical conditions are presented. Level of Evidence: 5.

Is muscular strength a predictor for primary or secondary ACL injury? A scoping review of prospective studies.

OBJECTIVE: To identify strength-related risk factors of ACL injury by conducting a scoping review of the peer-reviewed literature. METHODS: PubMed and EBSCO host (CINAHL Complete, MEDLINE Complete, SPORTDiscus) were searched from inception to August 2022. Prospective studies that examined strength strength-related risk factors for ACL injury (primary and secondary) were included. PRISMA Extension for Scoping Reviews guided data charting/extraction. RESULTS: 17 studies were included (eight primary ACL injury, nine secondary ACL injury). Knee flexor strength was the most studied predictor (10 studies), followed by hip abductor strength (9 studies). Across studies, measures of muscle performance were inconsistent. Significant strength-related risk factors were reported in seven of 17 studies. Potential strength-related risk factors of primary ACL injury included measures of hip strength (abductor or external rotator) and knee strength (knee flexor/extensor ratio and knee extensor strength symmetry) for secondary ACL injury. Limited/conflicting evidence was found for all strength-related risk factors. CONCLUSION: Measures of muscle strength appear to be predictive of primary and secondary ACL injury in a subset of identified studies. The heterogeneity of study designs and lack of standardization related to strength testing make it difficult to determine the overall impact of strength in predicting ACL injury.

Does the 2D Frontal Plane Projection Angle Predict Frontal Plane Knee Moments during Stepping, Landing, and Change of Direction Tasks?

Background: Although dynamic knee valgus can be visually identified using the 2D frontal plane projection angle (FPPA), the validity of the FPPA in terms of predicting frontal plane knee kinematics has been questioned. The biomechanical utility of the FPPA may lie in its ability to predict frontal plane knee moments. Hypothesis/Purpose: The purpose of the current study was to comprehensively evaluate the ability of the FPPA to predict the frontal plane knee kinetics (peak moment, average moment, and moment at peak knee flexion) across a wide range of tasks (stepping, landing, and change of direction). Design: Crossover Study Design. Methods: Three-dimensional lower-extremity kinetics and 2D video were obtained from 39 healthy athletes (15 males and 24 females) during execution of six tasks (step down, drop jump, lateral shuffle, deceleration, triple hop, side-step-cut). Linear regression analysis was performed to determine if the 2D FPPA at peak knee flexion predicted frontal plane knee moment variables during the deceleration phase of each task (peak moment, average moment, moment at peak knee flexion). Results: The FPPA was found to significantly predict the peak frontal plane knee moment for two tasks (deceleration and side-step-cut, R2 = 12% to 25%), average frontal plane knee moment for five tasks (drop jump, shuffle, deceleration, triple hop, side-step-cut, R2 = 15% to 40%), and frontal plane knee moment at peak knee flexion for five tasks (drop jump, shuffle, deceleration, triple hop, side-step-cut, R2 = 16% to 45%). Conclusion: An increased FPPA (medial knee collapse) predicted increased knee valgus moments (or decreased knee varus moments) during landing and change of direction tasks (but not stepping). However, the predictive ability of the FPPA was weak to moderate.

Quadriceps strength symmetry predicts vertical ground reaction force symmetry during running in patients who have undergone ACL reconstruction.

OBJECTIVE: To determine whether quadriceps strength symmetry can predict peak vertical ground reaction force (vGRF) running force symmetry in patients who have undergone ACL reconstruction (ACLR). We also sought to determine a cutoff for quadriceps strength symmetry to identify patients at risk for vGRF running asymmetry. DESIGN: Retrospective cross-sectional. SETTING: Clinical facility. METHODS: Bilateral quadriceps strength and vGRF data during running were obtained from 79 patients 26-30 weeks post ACLR. Linear regression was used to determine if quadriceps strength symmetry predicted peak vGRF running force symmetry. Classification and regression tree (CART) analysis was used to determine the cutoff value for quadriceps strength symmetry to identify patients at risk for vGRF running asymmetry. RESULTS: Increased quadriceps strength symmetry predicted increased vGRF running symmetry (R2 = 0.20). CART analysis revealed that patients with quadriceps strength symmetry less than or equal to 88% were at highest risk for vGRF running asymmetry (R2 = 26%). CONCLUSION: Greater quadriceps strength symmetry is predictive of greater vGRF running force symmetry in patients who have undergone ACLR. This finding highlights the need for clinicians to consider the degree of quadriceps strength symmetry before initiating a return to running program.

Predictors of Quadriceps Strength Asymmetry after Anterior Cruciate Ligament Reconstruction: A Chi-Squared Automatic Interaction Detection Decision Tree Analysis.

INTRODUCTION: The influence of graft type on the restoration of quadriceps strength symmetry after ACL reconstruction (ACLR) has been widely studied. However, an important consideration when evaluating quadriceps symmetry is the fact that this measure can be influenced by numerous factors beyond graft type. This study sought to determine if graft type is predictive of quadriceps strength asymmetry during the first 12 months post-ACLR taking into consideration potentially influential factors (i.e., age, sex, body mass index, time post-ACLR). METHODS: We retrospectively reviewed quadriceps strength data from 434 patients (303 female patients and 131 male patients) who had previously undergone ACLR with an autograft (hamstring tendon, quadriceps tendon [QT], patellar tendon [PT]) or allograft. Chi-Squared Automatic Interaction Detection decision tree analysis was used to evaluate if graft type is predictive of quadriceps strength asymmetry during the first 12 months post-ACLR taking into consideration age, sex, body mass index, and time post-ACLR. RESULTS: The best predictor of quadriceps strength asymmetry was graft type. Specifically, three graft categories were identified: 1) allograft and hamstring tendon autograft, 2) PT autograft, and 3) QT autograft. The average quadriceps strength asymmetry for each of the three identified categories was 0.91, 0.87, and 0.81, respectively, and differed statistically from each other ( P < 0.001). The second-best predictor of quadriceps strength asymmetry was sex, albeit only in the PT and QT groups (with female patients having increased asymmetry). Female patients post-ACLR with a QT autograft were at highest risk for quadriceps strength asymmetry. CONCLUSIONS: Graft type and sex are important predictors of quadriceps strength asymmetry after ACLR. Clinicians should take these factors into consideration when designing rehabilitation protocols to restore quadriceps strength symmetry during the postoperative period.

Utility of 2D Video Analysis for Assessing Frontal Plane Trunk and Pelvis Motion during Stepping, Landing, and Change in Direction Tasks: A Validity Study.

BACKGROUND: Excessive frontal plane motion of the trunk and/or pelvis has been implicated in numerous clinical conditions. To date, it is unclear whether 2D video is an appropriate surrogate for assessing frontal plane trunk and pelvis motion as a comprehensive validity study across a wide range of movements using a consistent methodology has not been performed. HYPOTHESIS/PURPOSE: The purpose of the current study was to assess the concurrent validity and agreement of frontal plane pelvis and trunk motion obtained with 2D video against the respective 3D angles during stepping, landing, and change in direction tasks. DESIGN: Crossover Study Design. METHODS: 3D kinematics and 2D frontal plane video were obtained from 39 healthy participants (15 males and 24 females) during five athletic tasks (step down, lateral shuffle, deceleration, triple hop, side-step-cut). Data were extracted at peak knee flexion. Pearson's correlation analysis was used to assess the association between the 2D and 3D frontal plane angles at the trunk and pelvis. Bland Altman plots were used to assess the level of agreement between the 2D and 3D frontal plane angles at the trunk and pelvis. RESULTS: 2D and 3D frontal plane angles for all tasks were correlated in a positive direction at the pelvis (r = 0.54 to 0.73, all p < 0.001) and trunk (r = 0.81 to 0.92, all p < 0.001). Absolute agreement in the frontal plane for all tasks and angles was below 5°. However, the 95% limits of agreement across tasks ranged from -12.8° to 21.3° for the pelvis and -11.8° to 9.4° for the trunk. CONCLUSIONS: The use of 2D video to assess frontal plane trunk and pelvis motion is appropriate during stepping, landing, and change of direction tasks, however caution is advised when high levels of agreement or accuracy is required.

Confidence to Return to Play After ACL Reconstruction: An Evaluation of Quadriceps Strength Symmetry and Injury Mechanism in Male Athletes.

BACKGROUND: After anterior cruciate ligament reconstruction (ACLR), diminished quadriceps strength symmetry and reduced psychological readiness to return to play (RTP) increase the risk for subsequent injury. Although the relationship between quadriceps strength symmetry and psychological readiness to RTP has been reported to be influenced by injury mechanism in female athletes, it is unclear whether such a relationship exists in male athletes. HYPOTHESIS: Quadriceps strength symmetry would be positively associated with greater psychological readiness to RTP after ACLR, regardless of injury mechanism. STUDY DESIGN: Retrospective cohort. LEVEL OF EVIDENCE: Level 3 (cohort study). METHODS: Sixty male patients completed strength testing and the Injury-Psychological Readiness to Return to Sport Scale (I-PRRS) at an outpatient clinical facility as part of return to sport testing after ACLR. Linear regression analysis was used to assess the relationship between the I-PRRS and the independent variables of interest (quadriceps strength symmetry and injury mechanism). RESULTS: For all patients combined, no symmetry × mechanism interaction was found (P = 0.11). A significant positive relationship was found between quadriceps strength symmetry and the I-PRRS score (P < 0.001, R2 = 0.31), after adjusting for time post-ACLR and injury mechanism. CONCLUSION: Greater quadriceps strength symmetry was associated with greater psychological readiness to RTP after ACLR in male athletes. In contrast to what has been reported in female athletes, this relationship was independent of injury mechanism. CLINICAL RELEVANCE: Given the potential negative consequences of quadriceps strength deficits on one's confidence to RTP, the need to restore quadriceps symmetry during the postoperative period is readily apparent. Low confidence or low psychological readiness to RTP may be indicative of quadriceps strength asymmetry or poor physical function in general.

Chronic Fatigue Syndrome: A Case Report Highlighting Diagnosing and Treatment Challenges and the Possibility of Jarisch-Herxheimer Reactions If High Infectious Loads Are Present.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex multi-system disease with no cure and no FDA-approved treatment. Approximately 25% of patients are house or bedbound, and some are so severe in function that they require tube-feeding and are unable to tolerate light, sound, and human touch. The overall goal of this case report was to (1) describe how past events (e.g., chronic sinusitis, amenorrhea, tick bites, congenital neutropenia, psychogenic polydipsia, food intolerances, and hypothyroidism) may have contributed to the development of severe ME/CFS in a single patient, and (2) the extensive medical interventions that the patient has pursued in an attempt to recover, which enabled her to return to graduate school after becoming bedridden with ME/CFS 4.5 years prior. This paper aims to increase awareness of the harsh reality of ME/CFS and the potential complications following initiation of any level of intervention, some of which may be necessary for long-term healing. Treatments may induce severe paradoxical reactions (Jarisch-Herxheimer reaction) if high infectious loads are present. It is our hope that sharing this case will improve research and treatment options for ME/CFS.

Estimation of vertical ground reaction force parameters during athletic tasks using 2D video.

BACKGROUND: Given that elevated vertical ground reaction forces (vGRF) have been reported to contribute to various lower-extremity injuries, there is a need for a practical method to characterize movement behavior that is representative of elevated impact forces. RESEARCH QUESTION: Can images obtained from 2D video be used to predict vGRF parameters during athletic tasks? Specifically, we sought to determine whether the 2D thigh angle obtained at peak knee flexion could be used to predict the peak vGRF and vGRF impulse during single limb and double limb landings and movements that involve a change of direction. METHODS: 2D sagittal plane video and vGRFs were obtained simultaneously from 39 participants (15 males and 24 females) during 5 athletic tasks (drop jump, lateral shuffle, deceleration, triple hop, side-step-cut). Linear regression analysis was performed to determine if the 2D thigh angle at peak knee flexion predicted the first peak of the vGRF and vGRF impulse during the deceleration phase of each task. RESULTS: The 2D thigh angle predicted the peak vGRF for all tasks except cutting (R2 = 0.17 to 0.47, all p < 0.01). However, the 2D thigh angle predicted the vGRF impulse for all 5 tasks (R2 = 0.13 to 0.39, all p < 0.025). SIGNIFICANCE: An increased 2D thigh angle (which is representative of increased hip and knee flexion) was able to predict lower peak vGRFs and vGRF impulse during athletic tasks. The 2D thigh angle is a potential clinical method to characterize movement behavior that may expose individuals to high impact forces.

Hip Abductor Rate of Torque Development as Opposed to Isometric Strength Predicts Peak Knee Valgus During Landing: Implications for Anterior Cruciate Ligament Injury.

Peak knee valgus has been shown to predict anterior cruciate ligament injury. The purpose of the current study was to compare peak rate of torque development (RTD) to peak isometric torque as a predictor of peak knee valgus during landing. Twenty-three healthy females participated. Hip abductor muscle performance was quantified using 2 types of isometric contractions: sustained and rapid. Peak isometric torque was calculated from the sustained isometric contraction. Peak RTD was calculated from the rapid isometric contraction (0-50 and 0-200 ms after force initiation). Kinematic data were collected during the deceleration phase of a double-leg drop jump task. Linear regression was used to assess the ability of hip abductor muscle performance variables to predict peak knee valgus. Increased peak RTD during the 0 to 50 milliseconds window after force initiation was found to significantly predict lower peak knee valgus (P = .011, R2 = .32). In contrast, neither peak RTD from 0 to 200 milliseconds after force initiation window (P = .45, R2 = .03) nor peak isometric torque (P = .49, R2 = .03) predicted peak knee valgus. The inability of the hip abductors to rapidly generate muscular force may be more indicative of "at-risk" movement behavior in females than measures of maximum strength.

Clinical Estimation of the Use of the Hip and Knee Extensors During Athletic Movements Using 2D Video.

Given that increased use of the knee extensors relative to the hip extensors may contribute to various knee injuries, there is a need for a practical method to characterize movement behavior indicative of how individuals utilize the hip and knee extensors during dynamic tasks. The purpose of the current study was to determine whether the difference between sagittal plane trunk and tibia orientations obtained from 2D video (2D trunk-tibia) could be used to predict the average hip/knee extensor moment ratio during athletic movements. Thirty-nine healthy athletes (15 males and 24 females) performed 6 tasks (step down, drop jump, lateral shuffle, deceleration, triple hop, and side-step-cut). Lower-extremity kinetics (3D) and sagittal plane video (2D) were collected simultaneously. Linear regression analysis was performed to determine if the 2D trunk-tibia angle at peak knee flexion predicted the average hip/knee extensor moment ratio during the deceleration phase of each task. For each task, an increase in the 2D trunk-tibia angle predicted an increase in the average hip/knee extensor moment ratio when adjusted for body mass (all P < .013, R2 = .17-.77). The 2D trunk-tibia angle represents a practical method to characterize movement behavior that is indicative of how individuals utilize the hip and knee extensors during dynamic tasks.

Confidence to Return to Play After Anterior Cruciate Ligament Reconstruction Is Influenced by Quadriceps Strength Symmetry and Injury Mechanism.

BACKGROUND: Although the restoration of quadriceps strength symmetry is a primary rehabilitation goal after anterior cruciate ligament reconstruction (ACLR), little is known about the potential relationship between quadriceps strength symmetry and psychological readiness to return to play (RTP). HYPOTHESIS: Quadriceps strength symmetry will be associated with psychological readiness to RTP after ACLR. Secondarily, injury mechanism will influence the association between quadriceps strength and psychological readiness to RTP. STUDY DESIGN: Retrospective cohort. LEVEL OF EVIDENCE: Level 3 (cohort study). METHODS: A total of 78 female patients completed strength testing and the Injury-Psychological Readiness to Return to Sport (I-PRRS) scale at an outpatient clinical facility as part of return to sport testing after ACLR. Linear regression analysis was used to assess the relationship between the I-PRRS and the independent variables of interest (quadriceps strength symmetry and injury mechanism). RESULTS: For all patients combined, a significant symmetry × mechanism interaction was found. When split by injury mechanism, a significant linear relationship was found between quadriceps strength symmetry and the I-PRRS score in patients who experienced a noncontact injury (n = 55; P = 0.01; R2 = 0.24). No such relationship was found for those who experienced a contact injury (n = 23; P = 0.97; R2 = 0.01). CONCLUSION: Greater quadriceps strength symmetry was associated with greater psychological readiness to RTP in female athletes after ACLR. This relationship, however, was present only in those who experienced a noncontact injury. CLINICAL RELEVANCE: Clinicians should consider both the physical and the psychological factors in assessing a patient's readiness to RTP. This may be particularly important for those who have experienced an ACL tear through a noncontact mechanism.

Trunk Inclination During Squatting is a Better Predictor of the Knee-Extensor Moment Than Shank Inclination.

CONTEXT: A limitation of previous studies on squatting mechanics is that the influence of trunk and shank inclination on the knee-extensor moment (KEM) has been studied in isolation. OBJECTIVE: The purpose of the current study was to determine the influence of segment orientation on the KEM during freestanding barbell squatting. DESIGN: Repeated-measures cross sectional. SETTING: University research laboratory. PARTICIPANTS: Sixteen healthy individuals (8 males and 8 females). INTERVENTION: Each participant performed 8 squat conditions in which shank and trunk inclinations were manipulated. MAIN OUTCOME MEASURES: 3D kinematic and kinetic data were collected at 250 and 1500 Hz, respectively. Regression analysis was conducted to identify the individual relationships between the KEM and the trunk and shank inclination at 60° and 90° of knee flexion. To identify the best predictor(s) of the KEM, stepwise regression was implemented. RESULTS: Increased shank inclination increased the KEM (P < .001, R2 = .21-.25). Conversely, increased trunk inclination decreased the KEM (P < .001, R2 = .49-.50). For the stepwise regression, trunk inclination entered first and explained the greatest variance in the KEM (all P < .001, R2 = .49-.50). Shank inclination entered second (all P < .010, R2 = .53-.54) and explained an additional 3% to 5% of the variance. CONCLUSIONS: Our results confirm that inclination of the trunk and shank have an opposing relationship with the KEM. Increased forward shank posture increases the KEM, while increased forward trunk posture decreases the KEM. However, when viewed in combination, the trunk was the superior predictor of the KEM, highlighting the fact that increased quadriceps demand created by a forward shank can be offset by trunk inclination.

Improvements in Hip Extensor Rate of Torque Development Influence Hip and Knee Extensor Feed-Forward Control.

Females have been reported to utilize a feedforward control strategy during landing in which they compensate for decreased rate of torque development (RTD) of the hip extensors through earlier pre-activation of the knee extensors. The purpose of this study was to determine the influence of a 4-week hip-focused training program on hip extensor RTD and feedforward control of the hip and knee extensors. Twenty-one females underwent hip extensor RTD evaluation and electromyographic assessment of the hip and knee extensors during a drop-jump task. Post-training, there was a significant improvement in hip extensor RTD (21.68 ± 5.44 to 23.33 ± 5.45 Nm/kg s, p = 0.009), and pre-activation of the hip extensors (87.1 ± 63.6 to 56.2 ± 60.9 ms, p < 0.001) and knee extensors (272.3 ± 113.8 to 124.0 ± 67.7 ms, p < 0.001) occurred closer to ground contact. A negative association was found between the change in hip extensor RTD and the change in knee extensor onset (r = -0.48, p = 0.03). We propose that the observed change in feedforward control is reflective of the decreased need for preparatory muscle activity owing to the improved capacity of the hip extensors to rapidly generate force.

Hip Strength as a Predictor of Ankle Sprains in Male Soccer Players: A Prospective Study.

CONTEXT: Diminished hip-abductor strength has been suggested to increase the risk of noncontact lateral ankle sprains. OBJECTIVE: To determine prospectively whether baseline hip-abductor strength predicts future noncontact lateral ankle sprains in competitive male soccer players. DESIGN: Prospective cohort study. SETTING: Athletic training facilities and various athletic fields. PATIENTS OR OTHER PARTICIPANTS: Two hundred ten competitive male soccer players. MAIN OUTCOME MEASURE(S): Before the start of the sport season, isometric hip-abductor strength was measured bilaterally using a handheld dynamometer. Any previous history of ankle sprain, body mass index, age, height, and weight were documented. During the sport season (30 weeks), ankle injury status was recorded by team medical providers. Injured athletes were further classified based on the mechanism of injury. Only data from injured athletes who sustained noncontact lateral ankle sprains were used for analysis. Postseason, logistic regression was used to determine whether baseline hip strength predicted future noncontact lateral ankle sprains. A receiver operating characteristic curve was constructed for hip strength to determine the cutoff value for distinguishing between high-risk and low-risk outcomes. RESULTS: A total of 25 noncontact lateral ankle sprains were confirmed, for an overall annual incidence of 11.9%. Baseline hip-abductor strength was lower in injured players than in uninjured players ( P = .008). Logistic regression indicated that impaired hip-abductor strength increased the future injury risk (odds ratio = 1.10 [95% confidence interval = 1.02, 1.18], P = .010). The strength cutoff to define high risk was ≤33.8% body weight, as determined by receiver operating characteristic curve analysis. For athletes classified as high risk, the probability of injury increased from 11.9% to 26.7%. CONCLUSIONS: Reduced isometric hip-abductor strength predisposed competitive male soccer players to noncontact lateral ankle sprains.

Hip Muscle Strength Predicts Noncontact Anterior Cruciate Ligament Injury in Male and Female Athletes: A Prospective Study.

BACKGROUND: Prospective studies have reported that abnormal movement patterns at the trunk, hip, and knee are associated with noncontact anterior cruciate ligament (ACL) injuries. Impaired hip strength may underlie these abnormal movement patterns, suggesting that diminished hip strength may increase the risk of noncontact ACL injury. PURPOSE: To determine whether baseline hip strength predicts future noncontact ACL injury in athletes. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Before the start of the competitive season, isometric hip strength (external rotation and abduction) was measured bilaterally by use of a handheld dynamometer in 501 competitive athletes (138 female and 363 male athletes) participating in various sports. During the sport season, ACL injury status was recorded, and injured athletes were further classified based on the mechanism of injury (noncontact vs contact). After the season, logistic regression was used to determine whether baseline hip strength predicted future noncontact ACL injury. Receiver operating characteristic (ROC) curves were constructed independently for each strength measure to determine the clinical cutoff value between a high-risk and low-risk outcome. RESULTS: A total of 15 noncontact ACL injuries were confirmed (6 females, 9 males), for an overall annual incidence of 3.0% (2.5% for males, 4.3% for females). Baseline hip strength measures (external rotation and abduction) were significantly lower in injured athletes compared with noninjured athletes (P = .003 and P < .001, respectively). Separate logistic regression models indicated that impaired hip strength increased future injury risk (external rotation: odds ratio [OR] = 1.23 [95% CI, 1.08-1.39], P = .001; abduction: OR = 1.12 [95% CI, 1.05-1.20], P = .001). Clinical cutoffs to define high risk were established as external rotation strength ≤20.3% BW (percentage of body weight) or abduction strength ≤35.4% BW. CONCLUSION: Measures of preseason isometric hip abduction and external rotation strength independently predicted future noncontact ACL injury status in competitive athletes. The study data suggest that screening procedures to assess ACL injury risk should include an assessment of isometric hip abduction and/or external rotation strength.

The VMO:VL activation ratio while squatting with hip adduction is influenced by the choice of recording electrode.

Concomitant hip adduction during squatting has long been advocated as a rehabilitative method to preferentially activate the VMO in persons with patellofemoral pain. This practice however has been based on research using surface electrodes which are prone to crosstalk from neighboring muscles (i.e., adductor magnus). This study sought to determine whether activation levels of the VMO relative to the VL while squatting with hip adduction would differ based on the choice of recording electrode. Ten healthy subjects performed a maneuver with hip adduction and without hip adduction. The mean VMO and VL activation levels were recorded simultaneously with surface and indwelling fine-wire electrodes. For both recording electrodes, the VMO and VL activity increased significantly with the addition of hip adduction (p < 0.05). However, the increase in VMO activation was more pronounced with surface electrodes, resulting in a significantly higher VMO:VL ratio with the incorporation of hip adduction compared to without hip adduction (p < 0.05). No difference in the VMO:VL ratio was observed between the two squat conditions for the fine-wire electrodes (p > 0.05). Our findings suggest that the VMO:VL activation ratio when squatting with hip adduction is influenced by electrode choice.

Shoulder- and back-muscle activation during shoulder abduction and flexion using a Bodyblade Pro versus dumbbells.

CONTEXT: 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. OBJECTIVE: To compare muscle activity, using electromyography (EMG), in the back and shoulder regions during shoulder exercises with the Bodyblade Pro vs dumbbells. DESIGN: Randomized crossover study. SETTING: San Diego State University biomechanics laboratory. PARTICIPANTS: 11 healthy male subjects age 19-32 y. INTERVENTION: 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. MAIN OUTCOME MEASURES: 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. RESULTS: 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. CONCLUSIONS: 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.

Influence of infrapatellar and suprapatellar straps on quadriceps muscle activity and onset timing during the body-weight squat.

The use of knee braces for the treatment of patellofemoral pain syndrome (PFPS) is widely documented, yet the mechanism by which such braces alleviate knee pain remains unclear. This study attempted to clarify this issue by simplifying the brace to the level of only straps. The effectiveness of an infrapatellar strap for PFPS remains controversial, and the use of a suprapatellar strap has not yet been studied. Quadriceps muscle activity and onset timing parameters were measured with surface electromyography (EMG) during a body-weight squat in 19 healthy subjects during 4 different knee-strapping conditions (infra, supra, both, and none). No differences in normalized mean or peak EMG activity in any part of the quadriceps were found. The onset timing of the vastus lateralis (VL) was significantly delayed when using an infrapatellar strap (p < 0.05) or both straps (p < 0.05) and marginally delayed when using a suprapatellar strap (p < 0.10) in comparison with the no-strap (control) condition. No differences in the vastus medialis oblique (VMO) onset timing or VMO-VL onset timing difference were found among the strapping conditions, although an improvement in timing was noted with the suprapatellar condition. The results provide novel evidence that the application of an infrapatellar strap, suprapatellar strap, or both straps improves quadriceps muscle timing imbalances by delaying VL onset. Because the largest delay in VL onset occurred when wearing both straps, the combined application of an infrapatellar and suprapatellar strap may be the most beneficial in managing patellofemoral pain. Knee straps, unlike braces, are cost effective, nonrestrictive, and can be universally fitted to any knee and based on the results deserve further study in the patellofemoral pain population.

Soy protein supports cardiovascular health by downregulating hydroxymethylglutaryl-coenzyme A reductase and sterol regulatory element-binding protein-2 and increasing antioxidant enzyme activity in rats with dextran sodium sulfate-induced mild systemic inflammation.

Animal and human studies have indicated that the presence of soy in the diet improves cardiovascular health. Inflammation plays a pivotal role in the progression of cardiovascular disease (CVD). However, little is known about how dextran sodium sulfate (DSS)-induced systemic inflammation impacts overall heart health and, correspondingly, how soy protein modulates risk of CVD development in DSS-induced systemic inflammation. We hypothesized that soy protein-fed rats would have a lower risk of CVD by beneficial alteration of gene expression involving lipid metabolism and antioxidant capacity in DSS-induced systemic inflammation. Forty Sprague-Dawley rats were divided into 4 groups: casein, casein + DSS, soy protein, and soy protein + DSS. After 26 days, inflammation was induced in one group from each diet by incorporating 3% DSS in drinking water for 48 hours. Soy protein-fed rats had lower final body weights (P = .010), epididymal fat weights (P = .049), total cholesterol (P < .001), and low-density lipoprotein cholesterol (P < .001). In regard to gene expression, soy protein-fed rats had lower sterol regulatory element-binding protein-2 (P = .032) and hydroxymethylglutaryl-coenzyme A reductase (P = .028) levels and higher low-density lipoprotein receptor levels (P = .036). Antioxidant enzyme activity of superoxide dismutase and catalase was higher among the soy protein groups (P = .037 and P = .002, respectively). These results suggest that soy protein positively influences cardiovascular health by regulating serum lipids through modified expression of sterol regulatory element-binding protein-2 and its downstream genes (ie, hydroxymethylglutaryl-coenzyme A reductase and low-density lipoprotein receptor) and by promoting the antioxidant enzyme activity of superoxide dismutase and catalase.