Music alters heart rate and psychological responses but not muscle activation during light-intensity isometric exercise.

Listening to music manipulates attention to be more externally focused, which has the potential to improve muscular efficiency. This study aimed to determine the effect of listening to music on muscle activation during an isometric exercise task, and compare this effect to those of other attentional focus conditions. Apparently healthy subjects (n = â€‹35; 16 men/19 women) completed an isometric elbow flexion task for 1 â€‹min in three randomized and counterbalanced conditions: internal focus (INT), external focus with a simple distraction task (EXT), or listening to music (MUS). Muscle activation of the biceps and triceps brachii and heart rate (HR) were recorded throughout the exercise tasks. Ratings of perceived exertion (RPE), affective valence, and motivation were measured at the end of each trial. There was no difference in muscle activation measures among the three conditions. HR during MUS was lower than EXT at 15 â€‹s ([89.4 â€‹± â€‹11.8] beats/min vs. [93.1 â€‹± â€‹12.9] beats/min; p â€‹= â€‹0.018) and 30 â€‹s ([90.6 â€‹± â€‹12.4] beats/min vs. [94.2 â€‹± â€‹12.5] beats/min; p â€‹= â€‹0.026), and lower than INT at 60 â€‹s ([93.3 â€‹± â€‹13.3] beats/min vs. [96.7 â€‹± â€‹12.0] beats/min; p â€‹= â€‹0.016). Overall RPE was higher for INT (13.4 â€‹± â€‹2.2) than for MUS ([12.6 â€‹± â€‹2.0]; p â€‹= â€‹0.020) and EXT ([11.94 â€‹± â€‹2.22]; p â€‹< â€‹0.001). Affective valence was higher for MUS than for INT ([2.7 â€‹± â€‹1.4] vs. [2.1 â€‹± â€‹1.5]; p â€‹= â€‹0.011). Manipulating attentional focus did not alter muscle activation for a light-intensity isometric muscular endurance task, though MUS was reported as more positive and requiring less exertion to complete than INT. Using music can therefore be recommended during light-intensity isometric exercise based on the psychological benefits observed.

Comparison of the Frontal Plane Projection Angle and the Dynamic Valgus Index to Identify Movement Dysfunction in Females with Patellofemoral Pain.

Background: Clinicians typically measure the knee frontal plane projection angle (FPPA) during a single-leg squat to identify females with patellofemoral pain (PFP). A limitation of this measure is minimal attention to movement of the pelvis on the femur that can create knee valgus loading. The dynamic valgus index (DVI) may be a better assessment. Hypothesis/Purpose: The purpose of this study was to compare the knee FPPA and DVI between females with and without PFP and determine if the DVI better identified females with PFP than the knee FPPA. Study Design: Case-control. Methods: Sixteen females with and 16 without PFP underwent 2-dimensional motion analysis when performing five trials of a single-leg squat. The average peak knee FPPA and peak DVI were analyzed. Independent t-tests determined between-group peak knee FPPA and peak DVI differences. Receiver operating characteristic (ROC) curves determined the area under the curve (AUC) scores for sensitivity and 1 - specificity of each measure. Paired-sample area difference under the ROC curves was conducted to determine differences in the AUC for the knee FPPA and DVI. Positive likelihood ratios were calculated for each measure. The significance level was p < 0.05. Results: Females with PFP exhibited a higher knee FPPA (p = 0.001) and DVI (p = 0.015) than controls. AUC scores were .85 (p = 0.001) and .76 (p = 0.012) for the knee FPPA and DVI, respectively. Paired-sample area difference under the ROC curves showed a similar (p = 0.10) AUC for the knee FPPA and DVI. The knee FPPA had 87.5% sensitivity and 68.8% specificity; the DVI had 81.3% sensitivity and 81.0% specificity. Positive likelihood ratios for the knee FPPA and DVI were 2.8 and 4.3, respectively. Conclusion: The DVI during a single-leg squat may be another useful tool for discriminating between females with and without PFP. Level of Evidence: 3a.

Patient-Reported Outcome Measures for Adults and Adolescents with Patellofemoral Pain: A Systematic Review of Content Validity and Feasibility Using the COSMIN Methodology.

OBJECTIVE: To assess the content validity and feasibility of patient-reported outcome measures (PROMs) used to assess pain and function in adults and adolescents with patellofemoral pain (PFP). DESIGN: Systematic review. LITERATURE SEARCH: We searched the databases PubMed, CINAHL, Scopus, SPORTDiscus, and the Cochrane Library from inception to January 6, 2022. STUDY SELECTION CRITERIA: We included studies that described the development or evaluation of the content validity of English-language PROMs for PFP, as well as their translations and cultural adaptations to different languages. DATA SYNTHESIS: Using the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology, we determined overall ratings and quality of evidence for the relevance, comprehensiveness, and comprehensibility of PROMs. We extracted data related to feasibility for clinical use (eg, administration time and scoring ease). RESULTS: Forty-three studies for 33 PROMs were included. The overall quality of most studies was "inadequate" due to failure to engage stakeholders and/or ensure adherence to rigorous qualitative research procedures. Of all PROMs evaluated, the Knee injury and Osteoarthritis Outcome Score-Patellofemoral subscale (KOOS-PF), was the only PROM with sufficient content validity components. Quality of evidence for content validity of the KOOS-PF was low. Most PROMs were rated feasible for clinical and research purposes. CONCLUSION: Most PROMs used to measure pain and function in patients with PFP have inadequate content validity. The KOOS-PF had the highest overall content validity. We recommend the KOOS-PF for evaluating pain and function (in research and clinical practice) in adults and adolescents with PFP. J Orthop Sports Phys Ther 2023;53(1):23-39. Epub: 18 October 2022. doi:10.2519/jospt.2022.11317.

Patient-Reported Outcome Measures for Adults and Adolescents With Patellofemoral Pain: A Systematic Review of Construct Validity, Reliability, Responsiveness, and Interpretability Using the COSMIN Methodology.

OBJECTIVE: We aimed to appraise the construct validity, reliability, responsiveness, and interpretability of patient-reported outcome measures (PROMs) used to assess function and pain in adults and adolescents with patellofemoral pain (PFP). DESIGN: Systematic review of measurement properties LITERATURE SEARCH: We searched the PubMed, CINAHL, Scopus, SPORTDiscus, and Cochrane Library databases from inception to January 6, 2022. STUDY SELECTION CRITERIA: We included studies that assessed the measurement properties of English-language PROMs for PFP and their cultural adaptations and translations. DATA SYNTHESIS: Using the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology, we determined overall ratings and quality of evidence for construct validity, internal consistency, reliability, measurement error, and responsiveness. We extracted data related to interpretability for clinical use. RESULTS: After screening 7066 titles, 61 studies for 33 PROMs were included. Only 2 PROMs had evidence of "sufficient" or "indeterminate" quality for all measurement properties. The Knee injury and Osteoarthritis Outcome Score patellofemoral subscale (KOOS-PF) had "low" to "high" quality evidence for a rating of "sufficient" for 4 measurement properties. The Lower Extremity Functional Scale (LEFS) had very low-quality evidence for a "sufficient" rating for 4 measurement properties. The KOOS-PF and LEFS were rated "indeterminate" for structural validity and internal consistency. The KOOS-PF had the best interpretability with reported minimal important change and 0% ceiling and floor effects. No studies examined cross-cultural validity. CONCLUSION: The KOOS-PF and LEFS had the strongest measurement properties among PROMs used for PFP. More research is needed, particularly regarding structural validity and interpretability of PROMs. J Orthop Sports Phys Ther 2023;53(8):1-20. Epub: 20 June 2023. doi:10.2519/jospt.2023.11730.

Survey of confidence and knowledge to manage patellofemoral pain in readers versus nonreaders of the physical therapy clinical practice guideline.

OBJECTIVES: To compare beliefs of physical therapists (PTs) who read the clinical practice guideline (CPG) for the management of individuals with patellofemoral pain (PFP) to those who have not read the CPG. DESIGN: Cross-sectional study. SETTING: Online survey. PARTICIPANTS: 494 currently licensed/registered PTs or physiotherapists. MAIN OUTCOME MEASURES: Respondents answered Likert-based or open-ended questions regarding the diagnosis, prognosis, risk factors, and management of individuals with PFP, as well as confidence for managing individuals with PFP, especially the ability to identify beneficial and non-beneficial interventions. We dichotomized responses into participants who read (READERS) and did not read (NonREADERS) the CPG. RESULTS: Most respondents held inaccurate beliefs about risk factors and prognosis; however, READERS' beliefs better aligned with the CPG than NonREADERS (P < 0.01). Most respondents correctly agreed that hip and knee exercise was the recommended treatment strategy; yet NonREADERS believed in implementing unsupported passive treatments (P < 0.01). READERS reported greater confidence in managing individuals with PFP, delivering evidence-based interventions, identifying less beneficial treatments, and locating evidence-based resources than NonREADERS (P < 0.01). CONCLUSION: While READERS and NonREADERS held accurate beliefs for exercise-based treatment for PFP, greater knowledge translation is needed to counter inaccurate beliefs regarding risk factors, prognostic factors, and passive treatments.

Reliability of the scapular dyskinesis test yes-no classification in asymptomatic individuals between students and expert physical therapists.

BACKGROUND: Scapular dyskinesis is considered a risk factor for the shoulder pain that may warrant screening for prevention. Clinicians of all experience screen scapular dyskinesis using the scapular dyskinesis test yes-no classification (Y-N), yet its reliability in asymptomatic individuals is unknown. We aimed to establish Y-N's intra- and inter-reliability between students and expert physical therapists. METHODS: We utilized a cross-sectional design using consecutive asymptomatic subjects. Six students and two experts rated 100 subjects using the Y-N. Cohen's kappa (κ) and Krippendorff's alpha (K-α) were calculated to determine intra- and inter-rater reliability. RESULTS: Intra- and inter-rater values for experts were κ=0.92 (95% confidence interval [CI], 0.91-0.93) and 0.85 (95% CI, 0.84-0.87) respectively; students were κ=0.77 (95% CI, 0.75-0.78) and K-α=0.63 (95% CI, 0.58-0.67). CONCLUSIONS: The Y-N is reliable in detecting scapular dyskinesis in asymptomatic individuals regardless of experience.

Hamstring Strain Injury in Athletes.

Hamstring strain injury (HSI) may result in considerable impairment, activity limitation, and participation restriction, including time lost from competitive sports. This CPG includes sports-related overloading and overstretching injuries to myofascial or musculotendinous structures in any combination of the 3 hamstring muscles (the semitendinosus, semimembranosus, and biceps femoris). J Orthop Sports Phys Ther 2022;52(3):CPG1-CPG44. doi:10.2519/jospt.2022.0301.

Electromyographic analysis of hip abductor exercises performed by a sample of total hip arthroplasty patients.

Weakness of the hip abductors after total hip arthroplasty may result in pain and/or functional limitation. Non-weight-bearing (NWB) exercises are often performed to target the hip abductors; however, muscle activation of NWB exercises has not been compared to weight-bearing (WB) exercises. Our purpose was to evaluate gluteus medius activation during 2 WB and 2 NWB hip abductor strengthening exercises. Fifteen patients at least 6 weeks post unilateral total hip arthroplasty volunteered for the study. Electromyographic amplitude for each exercise was normalized to each patient's maximal voluntary isometric contraction. There were no significant differences in gluteus medius electromyographic amplitudes between the 4 exercises (P = .15). Based on our results, NWB exercises provided no clear benefit in terms of gluteus medius activation when compared to potentially more functional WB exercises in the early postoperative period.

COMPARISON OF PATELLA ALIGNMENT AND CARTILAGE BIOMARKERS IN YOUNG ADULT FEMALES WITH AND WITHOUT PATELLOFEMORAL PAIN: A PILOT STUDY.

BACKGROUND: Evidence suggests that individuals with patellofemoral pain (PFP) may develop patellofemoral joint osteoarthritis (PFJOA). Limited data exist regarding an absolute association between PFP and PFJOA. Understanding this relationship will support the need for early interventions to manage PFP. HYPOTHESIS/PURPOSE: This study was conducted to determine if females with PFP have a patella position and cartilage biomarkers similar to individuals with PFJOA. It was hypothesized that females with PFP and excessive patella lateralization would have higher cartilage biomarker levels than controls. It also was hypothesized that a significant association would exist between pain and cartilage biomarker levels in subjects with excessive patella lateralization. STUDY DESIGN: Single-occasion, cross-sectional, observational. METHODS: Pain was assessed using a 10-cm visual analog scale (VAS) for activity pain over the previous week. Patella offset position (RAB angle) was measured using diagnostic ultrasound. Urine was collected and cartilage biomarkers quantified by analyzing C-telopeptide fragments of type II collagen (uCTX-II). Independent t-tests were used to determine between-group differences for RAB angle and uCTX-II. Bivariate correlations were used to determine associations between VAS and uCTX-II for females with PFP. RESULTS: Subjects (age range 20 to 30 years) had similar RAB angles (p = 0.21) and uCTX-II (p = 0.91). A significant association only existed between VAS scores and uCTX-II for females with PFP who had a RAB angle > 13 ° (r = 0.86; p = 0.003). Comparison of uCTX-II in the 25-to-30-year-old females with PFP and excessive patella lateralization in the current study to published normative data showed that this cohort had elevated biomarkers. CONCLUSION: These findings support that a certain cohort of individuals with PFP have features similar to individuals with confirmed PFJOA (patella lateralization and elevated biomarkers). Additional studies are needed to determine if interventions can reverse not only pain but biomarker levels. LEVEL OF EVIDENCE: 2b (diagnosis).

Patellofemoral Pain.

Patellofemoral pain (PFP) is a common musculoskeletal-related condition that is characterized by insidious onset of poorly defined pain, localized to the anterior retropatellar and/or peripatellar region of the knee. The onset of symptoms can be slow or acutely develop with a worsening of pain accompanying lower-limb loading activities (eg, squatting, prolonged sitting, ascending/descending stairs, jumping, or running). Symptoms can restrict participation in physical activity, sports, and work, as well as recur and persist for years. This clinical practice guideline will allow physical therapists and other rehabilitation specialists to stay up to date with evolving PFP knowledge and practices, and help them to make evidence-based treatment decisions. J Orthop Sports Phys Ther. 2019;49(9):CPG1-CPG95. doi:10.2519/jospt.2019.0302.

Hip strength and hip and knee kinematics during stair descent in females with and without patellofemoral pain syndrome.

STUDY DESIGN: Cross-sectional. OBJECTIVE: To determine if females presenting with patellofemoral pain syndrome (PFPS) from no discernable cause other than overuse demonstrate hip weakness and increased hip internal rotation, hip adduction, and knee valgus during stair descent. BACKGROUND: Historically, PFPS has been viewed exclusively as a knee problem. Recent findings have indicated an association between hip weakness and PFPS. Researchers have hypothesized that patients who demonstrate hip weakness would exhibit increased hip internal rotation, hip adduction, and knee valgus during functional activities. To date, researchers have not simultaneously examined hip and knee strength and kinematics in subjects with PFPS to make this determination. METHODS AND MEASURES: Eighteen females diagnosed with PFPS and 18 matched controls participated. Strength measures were taken for the hip external rotators and hip abductors. Hip and knee kinematics were collected as subjects completed a standardized stair-stepping task. Independent t tests were used to determine between-group differences in strength and kinematics during stair descent. RESULTS: Subjects with PFPS generated 24% less hip external rotator (P = .002) and 26% less hip abductor (P =. 006) torque. No between-group differences (P > .05) were found for average hip and knee transverse and frontal plane angles during stair descent. CONCLUSION: Subjects with PFPS had significant hip weakness but did not demonstrate altered hip and knee kinematics as previously theorized. Additional investigations are needed to better understand the association between hip weakness and PFPS etiology.

Treatment Success of Hip and Core or Knee Strengthening for Patellofemoral Pain: Development of Clinical Prediction Rules.

CONTEXT: Patellofemoral pain (PFP) is a common injury that interferes with quality of life and physical activity. Clinical subgroups of patients may exist, one of which is caused by proximal muscle dysfunction. OBJECTIVES: To develop clinical prediction rules that predict a positive outcome after either a hip and core- or knee-focused strengthening program for individuals with PFP. DESIGN: Secondary analysis of data from a randomized control trial. SETTING: Four university laboratories. PATIENTS OR OTHER PARTICIPANTS: A total of 199 participants with PFP. INTERVENTION(S): Participants were randomly allocated to either a hip and core-focused (n = 111) or knee-focused (n = 88) rehabilitation group for a 6-week program. MAIN OUTCOME MEASURE(S): Demographics, self-reported knee pain (visual analog scale) and function (Anterior Knee Pain Scale), hip strength, abdominal muscle endurance, and hip range of motion were evaluated at baseline. Treatment success was defined as a decrease in visual analog scale score by ≥2 cm or an increase in the Anterior Knee Pain Scale score by ≥8 points or both. Bivariate relationships between the outcome (treatment success) and the predictor variables were explored, followed by a forward stepwise logistic regression to predict a successful outcome. RESULTS: Patients with more pain, better function, greater lateral core endurance, and less anterior core endurance were more likely to have a successful outcome after hip and core strengthening (88% sensitivity and 54% specificity). Patients with lower weight, weaker hip internal rotation, stronger hip extension, and greater trunk-extension endurance were more likely to have success after knee strengthening (82% sensitivity and 58% specificity). CONCLUSION: The patients with PFP who have more baseline pain and yet maintain a high level of function may experience additional benefit from hip and core strengthening. The clinical prediction rules from this study remain in the developmental phase and should be applied with caution until externally validated.

National Athletic Trainers' Association Position Statement: Management of Individuals With Patellofemoral Pain.

OBJECTIVE:: To present recommendations for athletic trainers and other health care providers regarding the identification of risk factors for and management of individuals with patellofemoral pain (PFP). BACKGROUND:: Patellofemoral pain is one of the most common knee diagnoses; however, this condition continues to be one of the most challenging to manage. Recent evidence has suggested that certain risk factors may contribute to the development of PFP. Early identification of risk factors may allow clinicians to develop and implement programs aimed at reducing the incidence of this condition. To date, clinicians have used various treatment strategies that have not necessarily benefitted all patients. Suboptimal outcomes may reflect the need to integrate clinical practice with scientific evidence to facilitate clinical decision making. RECOMMENDATIONS:: The recommendations are based on the best available evidence. They are intended to give athletic trainers and other health care professionals a framework for identifying risk factors for and managing patients with PFP.

Trunk and hip muscle activation during yoga poses: Do sex-differences exist?

OBJECTIVE: To compare core activation during yoga between males and females. METHODS: Surface electromyography was used to quantify rectus abdominis (RA), abdominal obliques (AO), lumbar extensors (LE), and gluteus maximus (GMX) activation during four yoga poses. Data were expressed as 100% of a maximum voluntary isometric contraction. Mixed-model 2 × 2 analyses of variance with repeated measures were used to determine between-sex differences in muscle activity. RESULTS: Females generated greater RA activity than males during the High Plank (P < 0.0001) and Dominant-Side Warrior 1 (P = 0.017). They generated greater AO (P < 0.0001) and GMX (P = 0.004) activity during the High Plank (P < 0.0001). No between-sex EMG activity differences existed for the Chair and Upward Facing Dog. CONCLUSION: Findings have provided preliminary evidence for between-sex differences in muscle activation during yoga poses. Clinicians should consider such differences when prescribing yoga to improve muscle strength and endurance.

Reliability of electromyographic normalization methods for evaluating the hip musculature.

The purpose of this study was to determine the reliability of three normalization methods for analyzing hip abductor activation during rehabilitation exercises. Thirteen healthy subjects performed three open kinetic chain and three closed kinetic chain hip abductor exercises. Surface EMG activity for the gluteus medius was collected during each exercise and normalized based on a maximum voluntary isometric contraction (MVIC), mean dynamic (m-DYN), and peak dynamic activity (pk-DYN). Intraclass coefficient correlations (ICCs), intersubject coefficients of variation (CVs), and intrasubject CVs were then calculated for each normalization method. MVIC ICCs exceeded 0.93 for all exercises. M-DYN and pk-DYN ICCs exceeded 0.85 for all exercises except for the sidelying abduction exercise. Intersubject CVs ranged from 55% to 77% and 19% to 61% for the MVIC and dynamic methods, respectively. Intrasubject CVs ranged from 11% to 22% for all exercises under all normalization methods. The MVIC method provided the highest measurement reliability for determining differences in activation amplitudes between hip abductor exercises in healthy subjects. Future research should determine if these same results would apply to a symptomatic patient population.

PAIN, FUNCTION, AND STRENGTH OUTCOMES FOR MALES AND FEMALES WITH PATELLOFEMORAL PAIN WHO PARTICIPATE IN EITHER A HIP/CORE- OR KNEE-BASED REHABILITATION PROGRAM.

BACKGROUND: Hip exercise has been recommended for females with patellofemoral pain (PFP). It is unknown if males with PFP will benefit from a similar treatment strategy. HYPOTHESES/PURPOSE: The purpose of this study was to compare improvements in pain, function, and strength between males and females with PFP who participated in either a hip/core or knee rehabilitation program. The directional hypothesis was that females would respond more favorably to the hip/core rehabilitation program and males to the knee program. STUDY DESIGN: Randomized-controlled clinical trial. METHODS: Patients were randomly assigned to a six-week hip/core or knee rehabilitation program. Visual analog scale (VAS), Anterior Knee Pain Scale (AKPS), and hip and knee isometric strength were collected before and after subjects completed the rehabilitation program. Data were analyzed using an intention-to-treat basis. Separate mixed-model analyses of variance (ANOVA) with repeated measures were used to determine changes in VAS and AKPS and strength changes for subjects classified as treatment responders (successful outcome) and non-responders (unsuccessful outcome). RESULTS: Regardless of sex or rehabilitation group, VAS (F1,181=206.5; p<.0001) and AKPS (F1,181 = 160.4; p < 0.0001) scores improved. All treatment responders demonstrated improved hip abductor (F1,122 = 6.6; p = 0.007), hip extensor (F1,122 = 19.3; p < 0.0001), and knee extensor (F1,122 = 16.0; p < 0.0001) strength. A trend (F1,122 = 3.6; p = 0.06) existed for an effect of sex on hip external rotator strength change. Males demonstrated a 15.4% increase compared to a 5.0% increase for females. All treatment non-responders had minimal and non-significant (p > 0.05) strength changes. CONCLUSION: On average, males and females with PFP benefitted from either a hip/core or knee rehabilitation program. Subjects with successful outcomes likely had hip and knee weakness that responded well to the intervention. These males and females had similar and meaningful improvements in hip extensor and knee extensor strength. Only males had relevant changes in hip external rotator strength. Clinicians should consider a subgroup of males who may benefit from hip extensor and external rotator exercise and females who may benefit from hip extensor exercise. LEVEL OF EVIDENCE: 2b.

Relative electromyographic activity in trunk, hip, and knee muscles during unilateral weight bearing exercises: Implications for rehabilitation.

BACKGROUND: Clinicians routinely prescribe unilateral weight bearing exercises to strengthen the lower extremity. Researchers have primarily examined thigh muscle activation with minimal attention to the hip and trunk muscles. The purpose of this study was to quantify trunk, hip, and thigh muscle activation during these types of exercises. METHODS: Electromyographic (EMG) activity was collected for the abdominal obliques (AO), lumbar extensors (LE), gluteus maximus (GMX), gluteus medius (GM), and vastus medialis (VM) as subjects performed four unilateral weight bearing exercises. Data were expressed as 100% of a maximum voluntary isometric contraction (% MVIC). Separate analyses of variance with repeated measures were used to identify muscle activity differences across exercise. The sequentially-rejective Bonferroni test was used for all post-hoc analyses. RESULTS: EMG activity for the AO, LE, and GMX was low (5.7-18.9% MVIC) during all the exercises. The GM activity was moderate (21.4-26.5% MVIC) while VM activity was high (40.0-45.2% MVIC). CONCLUSION: Lower AO and LE activation most likely resulted from subjects maintaining a vertical trunk position over the stance limb during each exercise. The fact that the exercises required greater frontal plane control (from balancing on a single limb) most likely accounted for lower GMX activity. The exercises would provide little, if any, benefit for individuals with AO, LE, or GMX weakness. The unilateral weight bearing exercises would be beneficial for GM neuromuscular re-education and endurance and VM strengthening.

Electromyographic analysis of hip rehabilitation exercises in a group of healthy subjects.

STUDY DESIGN: Single-occasion, repeated-measures design. OBJECTIVE: To determine the magnitude of hip abductor muscle activation during 6 rehabilitation exercises. BACKGROUND: Many researchers have reported that hip strengthening, especially of the hip abductors, is an important component of a lower extremity rehabilitation program. Clinicians employ non-weight-bearing and weight-bearing exercise to strengthen the hip musculature; however, researchers have not examined relative differences in muscle activation during commonly used exercises. Information regarding these differences may provide clinicians with a scientific rationale needed for exercise prescription. METHODS AND MEASURES: Sixteen healthy subjects (mean +/- SD age, 27 +/- 5 years; range, 18-42 years; mean +/- SD height, 1.7 +/- 0.2 m; mean +/- SD body mass, 76 +/- 15 kg) volunteered for this study. Bipolar surface electrodes were applied to the right gluteus medius muscle. We measured muscle activation as subjects performed 3 non-weight-bearing (sidelying right hip abduction and standing right hip abduction with the hip at 0 degrees and 20 degrees of flexion) and 3 weight-bearing (left-sided pelvic drop and weight-bearing left hip abduction with the hips at 0 degrees and 20 degrees of flexion) exercises. Data were expressed as a percent of maximum voluntary isometric contraction of the right gluteus medius. Differences in muscle activation across exercises were determined using a 1-way analysis of variance with repeated measures, followed by a sequentially rejective Bonferroni post hoc analysis to identify differences between exercises. RESULTS: The weight-bearing exercises demonstrated significantly greater EMG amplitudes (P<.001) than all non-weight-bearing exercises except non-weight-bearing sidelying hip abduction. CONCLUSION: The weight-bearing exercises and non-weight-bearing sidelying hip abduction exercise resulted in greater muscle activation because of the greater external torque applied to the hip abductor musculature. Although the non-weight-bearing standing hip abduction exercises required the least activation, they may benefit patients who cannot safely perform the weight-bearing or sidelying hip abduction exercises. Clinicians may use results from this study when designing hip rehabilitation programs.

Comparison of hip and knee strength in males with and without patellofemoral pain.

OBJECTIVES: The primary purpose of this study was to compare hip strength in males with and without patellofemoral pain (PFP). The secondary purpose was to compare knee strength in males with and without PFP. DESIGN: Secondary analysis of cross-sectional data for males with and without PFP from a larger randomized controlled trial examining hip and core versus knee-muscle strengthening for the treatment of PFP. SETTING: Laboratory setting. PARTICIPANTS: Sixty-six males with PFP and 36 controls. MAIN OUTCOME MEASURES: Peak isometric force for the hip abductors, external rotators, internal rotators, extensors, and knee extensors expressed as a percentage of body mass (%BM). RESULTS: No differences existed with respect to any of the hip strength measures (P > .05). Males with PFP demonstrated almost 17% less knee extensor strength than controls (mean difference = 7.3 %BM; 95% confidence interval, 1.3-13.4 %BM; t = 2.41; P = .02). CONCLUSIONS: Unlike females, males with PFP did not demonstrate hip muscle weakness. However, differences did exist with knee extensor strength. These data provide preliminary evidence for the potential need for sex-specific interventions for individuals with PFP.

A literature review of studies evaluating gluteus maximus and gluteus medius activation during rehabilitation exercises.

Recently, clinicians have focused much attention on the importance of hip strength for the rehabilitation of not only patients with low back pain but also lower extremity pathology. Properly designing a rehabilitation program for the gluteal muscles requires careful consideration of biomechanical principles, such as length of the external moment arm, gravity, and subject positioning. Understanding the anatomy and function of these muscles also is essential. Electromyography (EMG) provides a useful means to determine muscle activation levels during specific exercises. Descriptions of specific exercises, as they relate to the gluteal muscles, are described. The specific performance of these exercises, the reliability of such EMG measures, and descriptive figures are also detailed. Of utmost importance to practicing clinicians is the interpretation of such data and how it can be best used in exercise prescription when formulating a treatment plan.