Automated Versus Traditional Scoring Agreeability During the Balance Error Scoring System.

CONTEXT: The Balance Error Scoring System (BESS) is a commonly used clinical tool to evaluate postural control that is traditionally performed through visual assessment and subjective evaluation of balance errors. The purpose of this study was to evaluate an automated computer-based scoring system using an instrumented pressure mat compared to the traditional human-based manual assessment. DESIGN: A descriptive cross-sectional study design was used to evaluate the performance of the automated versus human BESS scoring methodology in healthy individuals. METHODS: Fifty-one healthy active participants performed BESS trials following standard BESS procedures on an instrumented pressure mat (MobileMat, Tekscan Inc). Trained evaluators manually scored balance errors from frontal and sagittal plane video recordings for comparison to errors scored using center of force measurements and an automated scoring software (SportsAT, version 2.0.2, Tekscan Inc). A linear mixed model was used to determine measurement discrepancies across the 2 methods. Bland-Altman analyses were conducted to determine limit of agreement for the automated and manual scoring methods. RESULTS: Significant differences between the automated and manual errors scored were observed across all conditions (P < .05), excluding bilateral firm stance. The greatest discrepancy between scoring methods was during the tandem foam stance, while the smallest discrepancy was during the tandem firm stance. CONCLUSION: The 2 methods of BESS scoring are different with wide limits of agreement. The benefits and risks of each approach to error scoring should be considered when selecting the most appropriate metric for clinical use or research studies.

The Effect of Exercise on a Novel Dual-Task Assessment for Sport Concussion.

PURPOSE: This study aimed to determine the effect of exercise on cognitive and motor performance and the subsequent test-retest reliability of a novel dual-task (DT) assessment in nonconcussed college students. METHODS: Sixty nonconcussed college students (53.3% female) with an average age (±SD) of 20.5 ± 1.34 yr, height of 171.7 ± 9.33 cm, and mass of 69.3 ± 12.23 kg were included in the study. Participants were assigned to an exercise ( n = 30) or rest ( n = 30) intervention group and completed two study visits that were separated by a 2-wk test-retest interval. At each visit, participants completed a novel DT assessment that consisted of the concurrent administration of the Standardized Assessment of Concussion (SAC) and tandem gait (TG) before the exercise or rest intervention. After the DT assessment at the first visit, participants in the exercise group performed moderate-intensity exercise, whereas the rest group sat quietly for 30 min. After the intervention, both groups were readministered the DT assessment. At the second visit, the same procedures were followed, except that each group was administered the opposite intervention (e.g., the exercise group completed the rest intervention). A composite TG (cTG) score was calculated by summing the average time to complete the TG pattern during each SAC domain (immediate memory, digits backwards, months in reverse order, delayed recall). An ANCOVA was conducted to assess postintervention differences while controlling for preintervention performance. Test-retest reliability was assessed using intraclass correlation coefficients (ICC 3,2 ) with 95% confidence intervals, with all analyses performed with α = 0.05. RESULTS: SAC and cTG performance was similar ( P values > 0.05) from preintervention to postintervention for the rest or exercise protocols. Good (rest: ICC = 0.77 (0.62-0.87); exercise: ICC = 0.84 (0.73-0.90)) and excellent (rest: ICC = 0.97 (0.94-0.98); exercise: ICC = 0.93 (0.88-0.96)) test-retest reliabilities were observed for the SAC composite score and cTG score, respectively. CONCLUSIONS: Our DT assessment was robust to the influence of moderate-intensity exercise and demonstrated good-to-excellent test-retest reliability in a healthy collegiate sample.

Knee extensor torque-velocity relationships following anterior cruciate ligament reconstruction.

BACKGROUND: The inherent nature of the torque-velocity relationship is the inverse nature between the velocity of muscle contraction and torque production and is an indication of muscle function. The purpose of this study was to characterize the torque-velocity relationship in the quadriceps following anterior cruciate ligament reconstruction compared to healthy limbs. METHODS: 681 participants were included, 493 of which were patients at least four months following anterior cruciate ligament reconstruction (23.2 ± 10.08 yr, 6.6 ± 5.37 months post-surgery) and 188 were healthy participants (21.6 ± 3.77 yr). A subset of 175 post-surgical participants completed a repeated visit (8.1 ± 1.71 months post-surgery). Participants completed isokinetic knee extension at 90°/s and 180°/s. A one-way ANOVA was used to compare torque velocity relationships by limb type (surgical, contralateral, healthy). Paired samples t-tests were conducted to analyze the torque-velocity relationship across limbs and across time. FINDINGS: There was a large effect for limb type on torque-velocity (F(2, 1173) = 146.08, p < 0.001, η2 = 0.20). Surgical limbs demonstrated significantly lower torque-velocity relationships compared to the contralateral limbs (ACLR: 0.26 Nm/kg, contralateral:0.55 Nm/kg, p < 0.001, d = 1.18). Healthy limbs had similar torque-velocity relationships bilaterally (dominant limb: 0.48 Nm/kg, non-dominant limb: 0.49 Nm/kg, p = 0.45). The torque velocity relationship for the involved limb significantly increased in magnitude over time (+0.11 Nm/kg, p < 0.001, d = -0.61) while the contralateral limb torque-velocity relationship remained stable over time (0.0 Nm/kg difference, p = 0.60). INTERPRETATION: Following surgery, the knee extensors appear to have altered torque-velocity relationships compared to contralateral and healthy limbs. This may indicate a specific target for assessment and rehabilitation following surgery.

Hip Strength Recovery After Anterior Cruciate Ligament Reconstruction.

Background: Return-to-play (RTP) assessment after anterior cruciate ligament reconstruction (ACLR) rarely includes hip strength. Hypothesis: It was hypothesized that (1) patients after ACLR will have weaker hip abduction (AB) and adduction (AD) strength compared with the contralateral limb, with larger deficits in women, (2) there will be a correlation between hip and thigh strength ratios and patient-reported outcomes (PROs), and (3) hip AB and AD strength will improve over time. Study Design: Descriptive laboratory study. Methods: Included were 140 patients (74 male, 66 female; mean age, 24.16 ± 10.82 years) who underwent RTP assessment at 6.1 ± 1.6 months after ACLR; 86 patients underwent a second assessment at 8.2 ± 2.2 months. Hip AB/AD and knee extension/flexion isometric strength were measured and normalized to body mass, and PRO scores were collected. Strength ratios (hip vs thigh), limb differences (injured vs uninjured), sex-based differences, and relationships between strength ratios and PROs were determined. Results: Hip AB strength was weaker on the ACLR limb (ACLR vs contralateral: 1.85 ± 0.49 vs 1.89 ± 0.48 N·m/kg; P < .001) and hip AD torque was stronger (ACLR vs contralateral: 1.80 ± 0.51 vs 1.76 ± 0.52 N·m/kg; P = .004), with no sex-by-limb interaction found. Lower hip-to-thigh strength ratios of the ACLR limb were correlated with higher PRO scores (r = -0.17 to -0.25). Over time, hip AB strength increased in the ACLR limb more than in the contralateral limb (P = .01); however, the ACLR limb remained weaker in hip AB at visit 2 (ACLR vs contralateral: 1.88 ± 0.46 vs 1.91 ± 0.45 N·m/kg; P = .04). In both limbs, hip AD strength was greater at visit 2 than visit 1 (ACLR: 1.82 ± 0.48 vs 1.70 ± 0.48 N·m/kg; contralateral: 1.76 ± 0.47 vs 1.67 ± 0.47 N·m/kg; P < .01 for both). Conclusion: The ACLR limb had weaker hip AB and stronger AD compared with the contralateral limb at initial assessment. Hip muscle strength recovery was not influenced by sex. Hip strength and symmetry improved over the course of rehabilitation. Although strength differences across limbs were minor, the clinical importance of these differences is still unknown. Clinical Relevance: The evidence provided highlights the need to integrate hip strength into RTP assessments to identify hip strength deficits that may increase reinjury or lead to poor long-term outcomes.

Comparison of Patient-Reported Outcomes, Strength, and Functional Performance in Primary Versus Revision Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Clinical outcomes after revision anterior cruciate ligament reconstruction (ACLR) are not well understood. HYPOTHESIS: Patients undergoing revision ACLR would demonstrate worse patient-reported outcomes and worse limb symmetry compared with a cohort undergoing primary ACLR. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: 672 participants (373 with primary ACLR, 111 with revision ACLR, and 188 uninjured) completed functional testing at a single academic medical center. Descriptive information, operative variables, and patient-reported outcomes (International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, and Tegner Activity Scale score) were assessed for each patient. Quadriceps and hamstring strength tests were conducted using a Biodex System 3 Dynamometer. Single-leg hop for distance, triple hop test, and the 6-m timed hop test were also assessed. Limb symmetry index (LSI) between the ACLR limb and contralateral limb was calculated for strength and hop testing. Normalized peak torque (N·m/kg) was calculated for strength testing. RESULTS: No differences were found in group characteristics, excluding body mass (P < .001), or in patient-reported outcomes. There were no interactions between revision status, graft type, and sex. Knee extension LSI was inferior (P < .001) in participants who had undergone primary (73.0% ± 15.0%) and revision (77.2% ± 19.1%) ACLR compared with healthy, uninjured participants (98.8% ± 10.4%). Knee flexion LSI was inferior (P = .04) in the primary group (97.4% ± 18.4%) compared with the revision group (101.9% ± 18.5%). Difference in knee flexion LSI between the uninjured and primary groups, as well as between the uninjured and revision groups, did not reach statistical significance. Hop LSI outcomes were significantly different across all groups (P < .001). Between-group differences in extension in the involved limb (P < .001) were noted, as the uninjured group exhibited stronger knee extension (2.16 ± 0.46 N·m/kg) than the primary group (1.67 ± 0.47 N·m/kg) and the revision group (1.78 ± 0.48 N·m/kg). As well, differences in flexion in the involved limb (P = .01) were found, as the revision group exhibited stronger knee flexion (1.06 ± 0.25 N·m/kg) than the primary group (0.97 ± 0.29 N·m/kg) and the uninjured group (0.98 ± 0.24 N·m/kg). CONCLUSION: At 7 months postoperatively, patients who had undergone revision ACLR did not demonstrate inferior patient-reported outcomes, limb symmetry, strength, or functional performance compared with patients who had undergone primary ACLR. Patients who had undergone revision ACLR exhibited greater strength and LSI than their counterparts with primary ACLR, but these parameters were still inferior to those of uninjured controls.

Influence of interim functional assessments on patient outcomes at the time of return to activity following ACL-reconstruction.

OBJECTIVE: To compare patient outcomes at the time of the return to activity (RTA) progression between those with a prior interim assessment and those without. DESIGN: Retrospective, Cohort Study. SETTING: Controlled Laboratory. PARTICIPANTS: Patients following Anterior Cruciate Ligament Reconstruction (ACLR) were recruited through an ongoing RTA assessment program. Patients were stratified into two testing groups = "Single RTA test": only assessment between 6 and 9 months post-ACLR and "Repeat RTA test": prior assessment performed >2-months before their RTA assessment. Patients were matched based on time post-surgery, age, activity level, and graft type. MAIN OUTCOME MEASURE: Self-reported knee function and isokinetic knee flexor and extensor strength/symmetry were compared between groups. RESULTS: 392 patients were identified. Once matched, 138 patients (21.1 ± 7.0 years, 7.3 ±0 .9 mo post-ACLR) were analyzed. Repeat RTA test patients demonstrated higher measures of self-reported knee function (P = .04) and greater knee flexion strength (P = .006) and symmetry (P = .05). CONCLUSION: Patients with interim functional assessments reported greater self-reported knee function and higher hamstring strength at the time of RTA compared to patients that completed their only assessment within this time point. Early functional assessments may identify individualized deficits that can be addressed while patients are under supervision of rehabilitation specialists.

Disagreement in Pass Rates Between Strength and Performance Tests in Patients Recovering From Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Performance on strength and functional tests is often used to guide postoperative rehabilitation progress and return to activity decisions after anterior cruciate ligament reconstruction (ACLR). Clinicians may have difficulty in determining which criteria to follow if there is disagreement in performance outcomes among the tests. PURPOSE/HYPOTHESIS: The purpose of this study was to compare pass rates between strength tests and single-leg hop (SLHOP) tests among men and women and between patients with lower and higher preinjury activity levels recovering from ACLR. We hypothesized that pass rates would be nonuniformly distributed among test types, sex, and activity level and that more participants would pass hop tests than strength tests. DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 299 participants (146 men; 153 women)-at a mean of 6.8 ± 1.4 months after primary, unilateral, and uncomplicated ACLR (mean age, 23 ± 9.7 years; mean height, 172 ± 10.5 cm; mean mass, 75.8 ± 18.4 kg)-completed testing. Quadri.tif strength was evaluated using peak torque during isokinetic knee extension at 90 deg/s and 180 deg/s. Jump distance during the SLHOP and triple hop tests was measured (in cm). Strength and hop test measures were evaluated based on the limb symmetry index ((LSI) = (ACLR / contralateral side) × 100). We operationally defined "pass" as >90% on the LSI. RESULTS: Pass rates were nonuniformly distributed between isokinetic knee extension at 90 deg/s and the SLHOP test (χ2 = 18.64; P < .001). Disagreements between isokinetic testing at 90 deg/s and the SLHOP test occurred in 36.5% (109/299) of the participants. Among those who failed strength testing and passed hop testing, a greater portion reported higher activity levels before their injury (χ2 = 6.90; P = .01); however, there was no difference in pass rates between men and women. Similar patterns of disagreement were observed between all strength test and hop test outcomes. CONCLUSION: ACLR patients with higher activity levels may be more likely to pass hop testing despite failing quadri.tif strength testing. This may be an indicator of movement compensations to achieve jump symmetry in the presence of quadri.tif weakness.

Visuomotor therapy modulates corticospinal excitability in patients following anterior cruciate ligament reconstruction: A randomized crossover trial.

BACKGROUND: Corticospinal adaptations have been observed following anterior cruciate ligament reconstruction around the time of returning to activity. These measures have been related to quadriceps strength deficits. Visuomotor therapy, combining motor control tasks with visual biofeedback, has been shown to increase corticospinal excitability. The purpose of this study was to assess the immediate changes of corticospinal excitability following a single session of visuomotor therapy in patients following anterior cruciate ligament reconstruction. METHODS: This was a single blinded, sham-controlled crossover study. Ten patients following ACLR (8 Female, 26.1(6.2) years) completed assessments of quadriceps strength at approximately 4- and 6-months following anterior cruciate ligament reconstruction. At 6-months, quadriceps motor evoked potentials were assessed at 80%, 90%, 100%, 110%, 120%, 130%, 140%, and 150% of the patient's active motor threshold. Patients were randomized to receive a single session of visuomotor therapy(active) or passive motion(sham). Quadriceps motor evoked potentials were reassessed for treatment effect. Following a one-week washout period, all patients received the crossover intervention. FINDINGS: Moderate to large increases in motor response following visuomotor therapy 90%(P = .008, r = 0.60), 110%(P = .038, r = 0.46), 120%(P = .021, r = 0.52), 130%(P = .021, r = 0.52), 140%(P = .008, r = 0.60) and 150%(P = .021, r = 0.52) of the active motor threshold were found. Moderate increases in motor response was observed following the passive motion at 80% of the active motor threshold(P = .028, r = 0.49). INTERPRETATION: A single session of visuomotor therapy was found to increase quadriceps corticospinal motor response greater than the response to sham therapy. Visuomotor therapy is a potential supplement to quadriceps rehabilitation programs when upregulation of corticospinal excitability is indicated.

ISB clinical biomechanics award winner 2019: Knee extensor fatigue resistance in individuals following anterior cruciate ligament reconstruction.

BACKGROUND: Individuals following anterior cruciate ligament reconstruction demonstrate quadriceps weakness throughout the post-operative recovery and at the time of returning to sport. This is often accompanied with patterns of quadriceps fatigue resistance. As such, fatigue may be an identifier of individuals with delayed recovery. The purpose was to assess quadriceps fatigue in anterior cruciate ligament reconstructed patients at the time of return to sport in comparison to healthy controls. METHODS: A total of 215 individuals, 120 following anterior cruciate ligament reconstruction (21.0 (2.9) years, 63 Female, 5.96 (0.48) months post-surgery) and 95 healthy controls (21.5 (8.4) years, 49 Female), participated in this study. All participants completed a 30-s knee extensor maximum voluntary isometric contraction. Knee extensor strength, limb symmetry index, and fatigue (%) were compared between groups. Between-limb fatigue comparisons were made through the Fatigue Index Limb Difference = [(Involved Limb Fatigue Index) - (Uninvolved Limb Fatigue Index)]. FINDINGS: Individuals following anterior cruciate ligament reconstruction (18.7 (10.9)%, -5.6 (11.2)) demonstrated lower values of unilateral fatigue and Fatigue Index Limb Difference compared to healthy participants (22.5 (8.2)%, P = .002; 2.2 (7.9), P < .001). For anterior cruciate ligament reconstructed patients, there was a weak, negative, significant relationship between the involved limb strength and fatigue (r = -0.184, P = .048). There was no relationship between limb symmetry and Fatigue Index Limb Difference (r = 0.137, P = .142). For Healthy individuals, there was a positive, moderate relationship between limb symmetry and Fatigue Index Limb Difference (r = 0.400, P < .001). INTERPRETATION: Individuals following anterior cruciate ligament reconstruction demonstrate fatigue resistance compared to healthy active controls and greater resistance to fatigue in their involved limb compared to their contralateral limb.

Landing Stiffness Between Individuals With and Without a History of Low Back Pain.

CONTEXT: Reduced spinal stabilization, delayed onset of muscle activation, and increased knee joint stiffness have been reported in individuals with a history of low back pain (LBP). Biomechanical adaptations resulting from LBP may increase the risk for future injury due to suboptimal loading of the lower-extremity or lumbar spine. Assessing landing mechanics in these individuals could help identify which structures might be susceptible to future injury. OBJECTIVE: To compare vertical and joint stiffness of the lower-extremity and lumbar spine between individuals with and without a previous history of LBP. DESIGN: Cross-sectional study. SETTING: Research laboratory. PARTICIPANTS: There were 45 participants (24 without a previous history of LBP-age 23 [8] y, height 169.0 [8.5] cm, mass 69.8 [13.8] kg; 21 with a previous history of LBP-age 25[9] y, height 170.0 [8.0] cm, mass 70.2 [11.8] kg). INTERVENTIONS: Single-limb landing trials on the dominant and nondominant limb from a 30-cm box. MAIN OUTCOME MEASURES: Vertical stiffness and joint stiffness of the ankle, knee, hip, and lumbar spine. RESULTS: Individuals with a previous history of LBP had lower vertical stiffness (P = .04), but not joint stiffness measures compared with those without a previous history of LBP (P > .05). Overall females had lower vertical (P = .01), ankle (P = .02), and hip stiffness (P = .04) compared with males among all participants. Males with a previous history of LBP had lower vertical stiffness compared with males without a previous history LBP (P = .01). Among all individuals without a previous history of LBP, females had lower vertical (P < .01) and ankle stiffness measures (P = .04) compared with males. CONCLUSIONS: Landing stiffness may differ among males and females and a previous history of LBP. Comparisons between individuals with and without previous LBP should be considered when assessing landing strategies, and future research should focus on how LBP impacts landing mechanics.

How Much Time Is Needed Between Serial "Return to Play" Assessments to Achieve Clinically Important Strength Gains in Patients Recovering From Anterior Cruciate Ligament Reconstruction?

BACKGROUND: Pass rates for return-to-play evaluations are alarmingly low for patients after anterior cruciate ligament reconstruction (ACLR). Since timing of return to play is a complicated decision, it is important that patients be given optimal time to realize meaningful improvements in strength that warrant additional testing. PURPOSE: To (1) compare outcomes among patients assessed at different time points after ACLR, (2) determine strength gains indicative of improvements in subjective function, and (3) determine the amount of time necessary to achieve meaningful strength gains. STUDY DESIGN: Cross-sectional/case-control study; Level of evidence, 3. METHODS: A total of 293 patients participated in the study after ACLR (mean ± SD, 23.2 ± 10.1 years old; n = 142 female participants; 6.4 ± 0.9 months after ACLR). Participants were stratified on the month of their evaluation after ACLR: 5 to 6 months (n = 122), 6 to 7 months (n = 102), 7 to 8 months (n = 43), and 8 to 9 months (n = 26). The International Knee Documentation Committee (IKDC) subjective form and knee extensor and flexor torque and symmetry, as assessed through an isokinetic dynamometer, were compared among groups. Forty patients (20 female participants, 20.4 ± 7.1 years old) were referred for subsequent testing (2.14 ± 0.78 months after initial visit). Subjective improvement between visits was defined as a ≥9-point change of the IKDC score. Thresholds of knee extensor torque and symmetry indicative of subjective improvement and the time between assessments needed to achieve these strength improvements were determined. RESULTS: Patients between 5 and 6 months (IKDC, 79.7; interquartile range [IQR], 70.1-88.5) had lower subjective function compared to patients between 6 and 7 months (IKDC, 83.9; IQR, 74.5-92.0; P = .019) and 8 and 9 months after ACLR (IKDC, 89.1; IQR 75.8-92.3; P = .026). Patients between 5 and 6 months (1.41 N·m/kg; IQR, 1.16-1.73 N·m/kg]) had lower knee extensor torque compared to patients 6 and 7 months (1.59 N·m/kg; IQR, 1.23-1.95 N·m/kg; P = .013) and 7 and 8 months after ACLR (1.62 N·m/kg; IQR, 1.30-1.86 N·m/kg; P = .046). Patients between 5 and 6 months (66.4%; IQR, 54.2-78.6) had lower symmetry compared to patients between 6 and 7 months (71.8%; IQR,61.1-82.9; P = .019) and 8 and 9 months afterACLR (75.2%; IQR, 66.6-87.7; P = .014). Of the 40 patients that completed follow-up assessments, an increase in knee extensor torque of 0.22 N·m/kg and symmetry of 5.75% discriminated patients that achieved subjective improvement. A period of 1.97 months between assessments discriminated those that achieved the established symmetry threshold. CONCLUSION: Patients demonstrate increasing subjective and quadriceps function when tested at later time points from surgery; however, the observed values are low, suggesting that at 9 months patients are demonstrating deficits that may be improving. Approximately 2 months is needed to observe clinically meaningful improvements.

Prospective, Randomized, Double-Blind Evaluation of the Efficacy of a Single-Dose Hyaluronic Acid for the Treatment of Patellofemoral Chondromalacia.

BACKGROUND: Patellofemoral pain is common in the young and active populations. Nonoperative management is limited and focuses on physical therapy. Hyaluronic acid (HA) is an injectable device that has been used for the treatment of knee osteoarthritis. HYPOTHESIS: A single injection of HA would reduce pain and improve function in patients with patellofemoral pain who had previously failed conservative management. STUDY DESIGN: Randomized controlled trial; Level of evidence, 2. METHODS: A total of 86 patients with patellofemoral pain (65 females, 21 males; mean ± SD age, 27.0 ± 7.7 years; height, 168.6 ± 8.9 cm; weight, 74.6 ± 17.0 kg; body mass index, 26.2 ± 5.2 kg/m2) enrolled in this study after failing conservative management. Patients were randomly allocated to either 6 mL of HA or a sham injection. All patients were prescribed an additional home exercise program, including lower extremity strengthening and flexibility exercises, and were evaluated at 1, 3, and 6 months. Outcome assessments included patellofemoral pain assessment with a visual analog scale during a single-legged squat, KOOS (Knee injury and Osteoarthritis Outcome Score), Kujala score, Tegner activity rating, and normalized isometric knee extension strength. Group assignment was revealed after the 6-month assessment, and crossover treatment was offered to patients in the sham group who were still symptomatic. Linear mixed models were used to compare outcomes between groups and across time. RESULTS: A total of 45 patients were randomized to HA injection and 41 to sham, with 6 patients lost to follow-up (93% follow-up rate). Patients in both groups experienced a significant reduction in visual analog pain ratings and significant improvements in all domains of the KOOS and in Kujala scores at 6 months when compared with baseline measurement (P < .05); however, there was no significant difference between groups. There were no differences observed over time or between groups for normalized knee extension strength or Tegner activity rating (P > .05). CONCLUSION: HA injection had no clinically meaningful effect on pain or functional outcomes in patients diagnosed with patellofemoral pain. Improvements were observed for both groups in patient-reported pain and function, with no change in quadriceps strength or activity rating. REGISTRATION: NCT01771952 (ClinicalTrials.gov identifier).

Effect of Sex and Level of Activity on Lower-Extremity Strength, Functional Performance, and Limb Symmetry.

Context: Strength, functional performance, and limb symmetry are common objective clinical assessments used by clinicians to guide safe return to physical activity following injury. Population-specific unilateral limb outcomes or estimates of limb symmetry of these assessments should be established. Objective: To compare lower-extremity strength, functional performance, and limb symmetry in healthy participants based on sex and level of activity. Design: Descriptive laboratory study. Setting: Laboratory. Participants: A total of 117 healthy participants (72 males and 45 females; mass = 73.67 [13.60] kg, height = 1.76 [0.12] m, and age = 21.44 [2.92] y) without history of injury within 6 months were included. Interventions: Participants completed isokinetic concentric and isometric knee extension and flexion strength tasks at 90°/s, 180°/s, and 90°, respectively, and 4 hop tasks (single, cross-over, triple, and 6-m timed) during 1 session. Groups were separated by sex (male and female) and activity level (athlete and nonathlete). Participants rostered on National Collegiate Athletic Association (NCAA) Division I (DI) teams were considered as athletes, and non-NCAA DI healthy, uninjured participants were considered as nonathletes. Main Outcome Measures: Limb symmetry index (LSI), maximal voluntary isometric contraction (N·m/kg), peak torque (N·m/kg), average power (N·m/s), distance (m), and time hopped (s) were assessed. LSI was calculated by dividing the lower limb outcome by the higher limb outcome of the nondominant or dominant limb. Group differences were assessed through Mann-Whitney U tests and Cohen's d effect sizes for all comparisons. Results: LSI differences did not exist between groups. Mean LSIs for all participants ranged between 83.52% (12.54%) and 96.16% (3.82%). On average, males were stronger (range: d = 0.63-1.54), hopped farther (range: d = 1.52-1.63), and hopped faster (range: d = 1.67-1.68) than females. On average, some strength differences existed between athletes and nonathletes, but athletes hopped farther (range: d = 0.71-0.82) and faster (range: d = 0.87-0.88) than nonathletes. Conclusions: Unilateral limb strength and functional performance outcomes differ between sex and activity level, but not limb symmetry. These differences may be important for a clinician's understanding of normative values of common return-to-play assessment tasks.

A Comparison of Cervical Spine Motion After Immobilization With a Traditional Spine Board and Full-Body Vacuum-Mattress Splint.

BACKGROUND: The National Athletic Trainers' Association (NATA) advocates for cervical spine immobilization on a rigid board or vacuum splint and for removal of athletic equipment before transfer to an emergency medical facility. PURPOSE: To (1) compare triplanar cervical spine motion using motion capture between a traditional rigid spine board and a full-body vacuum splint in equipped and unequipped athletes, (2) assess cervical spine motion during the removal of a football helmet and shoulder pads, and (3) evaluate the effect of body mass on cervical spine motion. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty healthy male participants volunteered for this study to examine the influence of immobilization type and presence of equipment on triplanar angular cervical spine motion. Three-dimensional cervical spine kinematics was measured using an electromagnetic motion analysis system. Independent variables included testing condition (static lift and hold, 30° tilt, transfer, equipment removal), immobilization type (rigid, vacuum-mattress), and equipment (on, off). Peak sagittal-, frontal-, and transverse-plane angular motions were the primary outcome measures of interest. RESULTS: Subjective ratings of comfort and security did not differ between immobilization types (P > .05). Motion between the rigid board and vacuum splint did not differ by more than 2° under any testing condition, either with or without equipment. In removing equipment, the mean peak motion ranged from 12.5° to 14.0° for the rigid spine board and from 11.4° to 15.4° for the vacuum-mattress splint, and more transverse-plane motion occurred when using the vacuum-mattress splint compared with the rigid spine board (mean difference, 0.14 deg/s [95% CI, 0.05-0.23 deg/s]; P = .002). In patients weighing more than 250 lb, the rigid board provided less motion in the frontal plane (P = .027) and sagittal plane (P = .030) during the tilt condition and transfer condition, respectively. CONCLUSION: The current study confirms similar motion in the vacuum-mattress splint compared with the rigid backboard in varying sized equipped or nonequipped athletes. Cervical spine motion occurs when removing a football helmet and shoulder pads, at an unknown risk to the injured athlete. In athletes who weighed more than 250 lb, immobilization with the rigid board helped to reduce cervical spine motion. CLINICAL RELEVANCE: Athletic trainers and team physicians should consider immobilization of athletes who weigh more than 250 lb with a rigid board.

Clinical strategies for addressing muscle weakness following knee injury.

Muscle strength is a determinate of physical function and increasing muscle strength is an important clinical goal for patients with knee injury. This article discusses the emerging evidence regarding a novel rehabilitation strategy that uses disinhibitory modalities to increase neuromuscular activation in conjunction with traditional muscle strengthening for the purpose of maximizing strength gains following acute knee injury or surgery and in patients with knee osteoarthritis. The use of disinhibitory modalities and specific types of neuromuscular training for clinically maximizing strength are discussed.

Patellofemoral pain: epidemiology, pathophysiology, and treatment options.

Patients with anterior knee pain present a complex and common problem to health care providers. The diagnosis and treatment of these patients often involve a comprehensive evaluation that includes assessing the chronicity of the pain, the specific location of the complaint, and the previous treatment modalities attempted by the patient. This common diagnosis includes a wide variety of different pathologic abnormalities that can be present independently or concomitantly and cause a spectrum of disabilities for the patient.

Effect of ankle braces on lower extremity muscle activation during functional exercises in participants with chronic ankle instability.

BACKGROUND: Ankle bracing and rehabilitation are common methods to reduce the rate of recurrent ankle sprain in participants with chronic ankle instability (CAI). CAI participants utilize less muscle activity when performing functional exercises compared to healthy controls. The effect of ankle braces on muscle activity during functional exercises in participants with CAI has not been previously studied. PURPOSE: To determine the effect of bracing on motor output as demonstrated by surface EMG amplitudes in participants with CAI during single limb, eyes closed balance, star excursion balance, forward lunge, and lateral hop exercises. METHODS: A descriptive laboratory study was performed. Fifteen young adults with CAI performed functional exercises with and without ankle braces while surface EMG signals were recorded from the tibialis anterior, peroneus longus, lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius. The main outcome measures were normalized surface EMG amplitudes (root mean square area) for each muscle, muscles of the shank (distal three muscles), muscles of the thigh (proximal three muscles), and total muscle activity (all six muscles) of the lower extremity. A paired t-test was performed for each dependent variable to compare conditions. The level of significance was set a priori at p ≤ 0.05 for all analyses. RESULTS: During the forward lunge, bracing significantly reduced muscle activity pre-initial contact in the lateral gastrocnemius and post-initial contact in the peroneus longus. During the star excursion balance anterior reach the peroneus longus, lateral gastrocnemius, rectus femoris, and gluteus medius had significantly less muscle activity during braced trials. Bracing significantly reduced thigh and total muscle activity during the anterior reach and gluteus medius activity during the posterolateral reach. There were no differences between braced and unbraced conditions during the single limb eyes closed balance, star excursion balance posteromedial reach, or during lateral hop exercises. CONCLUSIONS: Clinicians should be aware of the decreased muscle activity that occurs during common rehabilitation exercises when patients with CAI complete those activities while wearing ankle braces. LEVEL OF EVIDENCE: Level III.

Changes in muscle thickness after exercise and biofeedback in people with low back pain.

CONTEXT: Individuals with low back pain (LBP) have reduced function of the transversus abdominis (TrA) and lumbar multifidus (LM) muscles. Biofeedback during exercise may increase the ability to contract the TrA and LM muscles compared with exercise alone. OBJECTIVE: To compare TrA preferential activation ratio (PAR) and the percent change in LM-muscle thickness in patients with LBP history before and after exercise with or without biofeedback. DESIGN: Controlled laboratory study. SETTING: University research laboratory. PATIENTS: 20 LBP individuals, 10 exercise alone and 10 exercise with biofeedback. INTERVENTIONS: Patients were allotted to tabletop exercises in isolation or tabletop exercises with visual, auditory, and tactile biofeedback. MAIN OUTCOME MEASURES: TrA PAR and percent change in LM-muscle thickness. RESULTS: There were no differences between groups at baseline (all P > .05). Nonparametric statistics showed decreased resting muscle thickness for total lateral abdominal-wall muscles (P = .007) but not TrA (P = .410) or LM (P = .173). Percent TrA thickness increased from table to standing positions before (P = .006) and after exercise (P = .009). TrA PAR increased after exercise (pre 0.01 ± 0.02, post 0.03 ± 0.04, P = .033) for all patients and for exercise with biofeedback (pre 0.02 ± 0.01, post 0.03 ± 0.01, P = .037) but not for exercise alone (pre 0.01 ± 0.02, post 0.02 ± 0.05, P = .241). No group differences were observed for TrA PAR before (exercise 0.01 ± 0.02, exercise with biofeedback 0.02 ± 0.01, P = .290) or after exercise (exercise 0.02 ± 0.05, exercise with biofeedback 0.03 ± 0.01, P = .174). There were no group differences in LM percent change before exercise (P = .999) or after exercise (P = .597). In addition, no changes were observed in LM percent change as a result of exercise among all participants (P = .391) or for each group (exercise P = .508, exercise with biofeedback P = .575). CONCLUSION: TrA PAR increased after a single session of exercises, whereas no thickness changes occurred in LM.

Knee-extension exercise's lack of immediate effect on maximal voluntary quadriceps torque and activation in individuals with anterior knee pain.

CONTEXT: Weight-bearing (WB) and non-weight-bearing (NWB) exercises are commonly used in rehabilitation programs for patients with anterior knee pain (AKP). OBJECTIVE: To determine the immediate effects of isolated WB or NWB knee-extension exercises on quadriceps torque output and activation in individuals with AKP. DESIGN: A single-blind randomized controlled trial. SETTING: Laboratory. PARTICIPANTS: 30 subjects with self-reported AKP. INTERVENTIONS: 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. MAIN OUTCOME MEASURES: Quadriceps torque output (MVIC: N·m/Kg) and quadriceps activation (CAR). RESULTS: 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. CONCLUSIONS: 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.