Neuromuscular Consequences of Lumbopelvic Dysfunction: Research and Clinical Perspectives.

Injuries involving the lumbopelvic region (ie, lumbar spine, pelvis, hip) are common across the lifespan and include pathologies such as low back pain, femoroacetabular impingement syndrome, labrum tear, and osteoarthritis. Joint injury is known to result in an arthrogenic muscle response which contributes to muscle weakness and altered movement patterns. The purpose of this manuscript is to summarize the arthrogenic muscle response that occurs across lumbopelvic region pathologies, identify methods to quantify muscle function, and propose suggestions for future research. While each lumbopelvic region pathology is unique, there are a few common impairments and a relative consistent arthrogenic muscle response that occurs across the region. Hip muscle weakness and hip joint range of motion limitations occur with both lumbar spine and hip pathologies, and individuals with low back pain are known to demonstrate inhibition of the transversus abdominis and multifidus. Assessment of muscle inhibition is often limited to research laboratory settings, but dynamometers, ultrasound imaging, and electromyography offer clinical capacity to quantify muscle function and inform treatment pathways. Future studies should systematically determine the arthrogenic muscle response across multiple muscle groups and the timeline for changes in muscle function and determine whether disinhibitory modalities improve functional outcomes beyond traditional treatment approaches.

Ability of Isokinetic Dynamometer to Predict Isotonic Knee Extension 1-Repetition Maximum.

CONTEXT: Resistance training exercise prescription is often based on exercises performed at a percentage of a 1-repetition maximum (1RM). Following knee injury, there is no consensus when a patient can safely perform 1RM testing. Resistance training programs require the use of higher loads, and loads used in knee injury rehabilitation may be too low to elicit gains in strength and power. A maximum isometric contraction can safely be performed during early stages of knee rehabilitation and has potential to predict an isotonic knee extension 1RM. OBJECTIVE: To determine whether a 1RM on an isotonic knee extension machine can be predicted from isometric peak torque measurements. DESIGN: Descriptive laboratory study. SETTING: University research laboratory. PARTICIPANTS: A total of 20 (12 males and 8 females) healthy, physically active adults. MAIN OUTCOME MEASURES: An isokinetic dynamometer was used to determine isometric peak torque (in N·m). 1RM testing was performed on a knee extension machine. Linear regression was used to develop a prediction equation, and Bland-Altman plots with limits of agreement calculations were used to validate the equation. RESULTS: There was a significant correlation (P < .001, r = .926) between peak torque (283.0 [22.6] N·m) and the knee extension 1RM (69.1 [22.6] kg). The prediction equation overestimated the loads (2.3 [9.1] kg; 95% confidence interval, -15.6 to 20.1 kg). CONCLUSIONS: The results show that isometric peak torque values obtained on an isokinetic dynamometer can be used to estimate 1RM values for isotonic knee extension. Although the prediction equation tends to overestimate loads, the relatively wide confidence intervals indicate that results should be viewed with caution.

Optimizing Between-Session Reliability for Quadriceps Peak Torque and Rate of Torque Development Measures.

Grindstaff, TL, Palimenio, MR, Franco, M, Anderson, D, Bagwell, JJ, and Katsavelis, D. Optimizing between-session reliability for quadriceps peak torque and rate of torque development measures. J Strength Cond Res 33(7): 1840-1847, 2019-Quadriceps peak torque and rate of torque development (RTD) have relevance for athletic performance and recovery after knee injury. The number of repetitions performed to determine RTD varies between studies, and the associated measurement error has not been established. The purpose of this study was to determine the number of repetitions necessary to optimize the between-session reliability for isometric quadriceps peak torque and RTD measures and to quantify estimates of measurement error. Twenty participants (age = 21.7 ± 1.7 years, height = 172.5 ± 16.0 cm, body mass = 76.0 ± 15.5 kg, and Tegner = 7.1 ± 1.2) volunteered for this study. Quadriceps isometric peak torque and RTD (50, 100, 150, 200, and 250 ms, and maximum torque) were obtained during 2 testing sessions. Between-session reliability was determined using intraclass correlation coefficients (ICC2,k), using the minimal detectable change (MDC) and coefficient of variation (CoV) to quantify measurement error. Between-session reliability was best maximized by using the average of the 3 repetitions with the highest peak torque. Reliability was good for quadriceps peak torque (ICC2,3 = 0.98; MDC = 51.1 N·m; CoV = 38.0%) and ranged from moderate to good for quadriceps RTD measures (ICC2,3 = 0.61 to 0.91; MDC = 264.8 to 738.3 N·m·s; CoV = 38.1-57.9%). Measures of late RTD were less variable and more reliable than early RTD and average RTD measures. These results provide confidence when measuring between-session changes for late RTD measures, but changes in early RTD may be more difficult to distinguish from measurement error. Methods should be used to minimize variability between repetitions and sessions.

Weak associations between body mass index and self-reported disability in people with unilateral anterior cruciate ligament reconstruction.

PURPOSE AND HYPOTHESIS: Individuals with an anterior cruciate ligament reconstruction (ACLR) are susceptible to persistent disability, weight gain and the development of knee osteoarthritis. It remains unclear whether body mass index (BMI) is a factor that influences disability following ACLR. The purpose of this study was to determine the association between BMI and self-reported disability [International Knee Documentation Committee (IKDC) Index] in individuals with a unilateral ACLR. We hypothesized that lower BMI would associate with higher IKDC. METHODS: BMI and IKDC were measured in 668 individuals with a unilateral ACLR (60.9% female, BMI 24.4 ± 3.7 kg/m2, IKDC 84.7 ± 11.9%). Bivariate associations were conducted between BMI and IKDC for the entire sample and selected subsets (gender, ACLR graft type and history of meniscal injury). Multiple regression analyses were used to determine the impact of potential covariates (Tegner score, age and months since ACLR) for significant bivariate associations. After accounting for covariates, there were no significant associations between BMI and IKDC when separately evaluating the cohort based on either gender or history of a concomitant meniscal injury. The odds of achieving age- and gender-matched healthy population average IKDC scores for those with low (<25) and high (≥25) BMI were determined. RESULTS: Lower BMI associated with higher IKDC (r = -0.08, P = 0.04). For the entire sample, BMI did not uniquely predict variance in IKDC (ΔR 2 > 0.001, n.s.) after accounting for covariates. BMI uniquely predicted a significant but negligible amount of variance in IKDC in individuals with a patellar tendon autograft (ΔR 2 = 0.015, n.s.). Individuals with low BMI demonstrated higher odds (odds ratio = 1.45; 1.05-1.99) of achieving population average IKDC scores compared to participants with high BMI. CONCLUSIONS: There was a significant but negligible correlation between lower BMI and lesser disability in individuals with unilateral ACLR and individuals who are underweight or of normal BMI demonstrated higher odds of achieving population average IKDC scores compared to overweight or obese individuals. While an overall association was found between lower BMI and lesser disability, the magnitude of the association remains negligible; therefore, BMI was not a strong clinical predictor of successful ACLR outcomes in this cohort of patients with unilateral ACLR. LEVEL OF EVIDENCE: Cross-sectional prognostic study, Level II.

Reliability of Hip Rotation Range of Motion in Supine and Seated Positions.

CONTEXT: Hip rotation range of motion (ROM) is commonly assessed in individuals with lower extremity or spine pathology. It remains unknown which hip rotation ROM testing position is most reliable. OBJECTIVE: To compare interrater and intrarater reliabilities between hip internal rotation (IR) and external rotation (ER) ROM in supine and seated positions. STUDY DESIGN: Controlled laboratory study. SETTING: University research laboratory. PARTICIPANTS: A total of 19 participants (11 females and 8 males; age = 23.5 [1.2] y; height = 173.2 [8.6] cm; and mass = 69.2 [13.4] kg) without hip, knee, low back, or sacroiliac pain within the preceding 3 months or history of hip or low back surgery were recruited. INTERVENTIONS: Three testers obtained measures during 2 testing sessions. Passive supine and seated hip IR and ER ROM were performed with the hip and knee flexed to 90°. MAIN OUTCOME MEASURES: The primary outcome measures were hip IR and ER ROM in supine and seated positions (in degrees). Interrater and intrarater reliabilities were calculated using intraclass correlation coefficients (ICCs). Minimal detectable change was calculated. Differences between supine and seated hip IR and ER ROM values were assessed using paired t tests (significance level was .05). RESULTS: Supine hip IR and ER ROM interrater and intrarater reliabilities were excellent (ICC = .75-.91). Seated hip IR ROM interrater and intrarater reliabilities were good (ICC = .64-.71). Seated hip ER ROM interrater reliability was good (ICC = .65), and intrarater reliabilities were good to excellent (ICC = .65-.82). Minimal detectable change values for supine and seated hip IR and ER ROM ranged from 6.1° to 8.6°. There were significant differences between supine and seated positions for hip IR and ER ROM (41.6° vs 44.5°; P < .01 and 53.0° vs 44.2°; P < .01, respectively). CONCLUSION: Supine hip rotation had higher interrater and intrarater reliabilities. Hip IR and ER ROM values differed significantly between supine and seated positions and should not be used interchangeably.

Optimal stimulation parameters to detect deficits in quadriceps voluntary activation.

The purpose of this study was to determine optimal stimulation parameters and calculation methods to estimate quadriceps voluntary activation while minimizing participant discomfort. Twelve healthy adults (8 men and 4 women; mean ± SD, age = 36.8 ± 15.6 years, weight = 76.1 ± 12.9 kg, height = 170.2 ± 8.6 cm). Repeated maximal volitional isometric contractions (MVIC) were performed while imposing 4 stimulation combinations (10 or 2 pulses; 400 or 200 V; and variable or standardized current) with the quadriceps in a relaxed state (resting twitch [RT]) and during an MVIC. Quadriceps activation was quantified by calculating the central activation ratio and the percent activation. Discomfort was quantified using the visual analog scale. When comparing calculation methods between the same stimulation parameters, the central activation ratio calculation method produced quadriceps activation values that were significantly greater (p < 0.009) than those derived using the percent activation calculation method. The doublet pulse stimulus produced less discomfort during the RT (p < 0.04) and MVIC (p < 0.001) when compared with all other combinations using a train of stimuli (10 pulses). Correlations for all estimates of quadriceps activation were strong (r = 0.85-0.99, p < 0.001). A doublet pulse stimulus produced discomfort levels that were over 50% lower than a 10-pulse train of stimuli and correlated well (r > 0.88) with activation levels obtained with a 10-pulse train of stimuli. Therefore, the use of a doublet pulse stimulus provides quadriceps activation information equivalent to other methods while minimizing participant discomfort.

The effects of verbal cues on EMG activity during a quadriceps setting exercise.

CONTEXT: A quadriceps setting (quad set) exercise is commonly utilized following knee injury, but there is great variation in cues that clinicians provide to patients when performing the exercise. OBJECTIVES: To determine if internal, external, or visual cues results in the greatest quadriceps electromyographical (EMG) activity during a quadriceps setting exercise in healthy individuals. DESIGN: Descriptive laboratory study. SETTING: University research laboratory. PARTICIPANTS: Thirty healthy individuals volunteered for this study. Participants were given one of five cues in a randomized order: internal cue "tighten your thigh muscles," internal cue "push your knee down," external cue "push into the bolster," external cue "push into the strap," or visual biofeedback using the cue "raise the value on the screen as high as you can." MAIN OUTCOME MEASURES: Normalized vastus lateralis EMG activity. RESULTS: Both visual biofeedback (83.2±24.9%) and "press into the strap" (76.8±24.4%) produced significantly greater (p< 0.001) EMG activity than the push knee down (53.2±27.0%), tighten thigh (52.7±27.3%), or push into the bolster (50.8±26.3) conditions. There was no significant difference (p= 0.10) between the visual biofeedback and "press into the strap" conditions as well as no significant difference (p> 0.38) between the push knee down, tighten thigh, or push into the bolster conditions. CONCLUSIONS: If the clinical aim during a quadriceps setting exercise is to obtain the greatest volitional muscle recruitment, the use of visual biofeedback or pressing into a strap is recommended.

Increased active hamstring stiffness after exercise in women with a history of low back pain.

OBJECTIVE: To compare active hamstring stiffness in female subjects with and without a history of low back pain (LBP) after a standardized 20-min aerobic-exercise session. DESIGN: Case control. SETTING: Laboratory. PARTICIPANTS: 12 women with a history of recurrent episodes of LBP (age = 22.4 ± 2.1 y, mass = 67.1 ± 11.8 kg, height = 167.9 ± 8 cm) and 12 matched healthy women (age = 21.7 ± 1.7 y, mass = 61.4 ± 8.8 kg, height = 165.6 ± 7.3 cm). LBP subjects reported an average 6.5 ± 4.7 on the Oswestry Disability Index. INTERVENTIONS: Participants walked at a self-selected speed (minimum 3.0 miles/h) for 20 min. The treadmill incline was raised 1% grade per minute for the first 15 min. During the last 5 min, participants adjusted the incline of the treadmill so they would maintain a moderate level of perceived exertion through the end of the exercise protocol. MAIN OUTCOME MEASURES: During session 1, active hamstring stiffness, hamstring and quadriceps isometric strength, and concurrently collected electromyographic activity were recorded before and immediately after the exercise protocol. For session 2, subjects returned 48-72 h after exercise for repeat measure of active hamstring stiffness. RESULTS: Hamstring active stiffness (Nm/rad) taken immediately postexercise was not significantly different between groups. However, individuals with a history of recurrent LBP episodes presented significantly increased hamstring stiffness 48-72 h postexercise compared with controls. For other outcomes, there was no group difference. CONCLUSIONS: Women with a history of recurrent LBP episodes presented greater active hamstring stiffness 48-72 h after aerobic exercise.

Quadriceps Strength and Knee-Related Symptom State 6 Months After Anterior Cruciate Ligament Reconstruction.

CONTEXT: Isometric quadriceps strength metrics and patient-reported outcomes are commonly used in return-to-sport assessments in those with anterior cruciate ligament reconstruction (ACLR). Patients may experience clinical knee-related symptoms aggravating enough to seek additional medical care after ACLR. In addition to seeking additional medical care, these patient-reported clinical knee-related symptoms may also influence function after ACLR. However, whether an association exists between these common quadriceps metrics and the patient-reported clinical knee-related symptom state is unknown. OBJECTIVE: To determine if meeting isometric quadriceps strength and symmetry criteria is associated with acceptable clinical knee-related symptoms at 5 to 7 months post-ACLR. DESIGN: Cross-sectional study. SETTING: Laboratories. PATIENTS OR OTHER PARTICIPANTS: We classified individuals at 5 to 7 months post-ACLR based on their isometric ACLR and uninvolved-limb quadriceps strength or quadriceps strength symmetry. We also dichotomized participants based on the Englund et al criteria for unacceptable clinical knee-related symptoms. MAIN OUTCOME MEASURE(S): Quadriceps strength variables were compared between groups using analysis of covariance, and the relative risk of a participant in each quadriceps strength group reporting acceptable clinical knee-related symptoms was determined using binary logistic regression. RESULTS: A total of 173 individuals participated. The isometric quadriceps strength and limb symmetry index were different (P < .001) between quadriceps strength groups. Those categorized as both strong and symmetric had a 1.28 (95% CI = 0.94, 1.74) and individuals categorized as symmetric only had a 1.29 (95% CI = 0.97, 1.73) times greater relative risk of reporting acceptable clinical knee-related symptoms compared with the neither strong nor symmetric group. CONCLUSIONS: The majority of individuals (85%) recovering from ACLR failed to meet either the clinical quadriceps strength or symmetry criteria at 5 to 7 months post-ACLR. Quadriceps strength and quadriceps strength symmetry are clinically important but may not be primary determinants of the clinical knee-related symptom state within the first 6 months post-ACLR.

Age-, Sex-, and Graft-Specific Reference Values From 783 Adolescent Patients at 5 to 7 Months After ACL Reconstruction: IKDC, Pedi-IKDC, KOOS, ACL-RSI, Single-Leg Hop, and Thigh Strength.

OBJECTIVE: To describe age-, sex-, and graft source-specific reference values for patient-reported, physical function, and strength outcome measures in adolescents at 5 to 7 months after anterior cruciate ligament reconstruction. DESIGN: Cross-sectional study. METHODS: Data were collected at 3 universities and 2 children's hospitals. The participants completed at least one of the International Knee Documentation Committee (IKDC) Subjective Evaluation Form, Pediatric IKDC (Pedi-IKDC), Knee Injury and Osteoarthritis Outcomes Score (KOOS), and Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) Scale. Participants also completed single-leg hop tests and/or isokinetic quadriceps and hamstrings strength assessments (at 60°/s). Reference values were summarized using descriptive statistics and stratified for age, sex, and graft source. RESULTS: Reference values were reported for common patient-reported outcomes and measures of physical function and strength from 783 participants (56% females, age = 16. 4 ± 2.0 years) who were in early adolescence (12-14 years, N = 183, 52% females), middle adolescence (15-17 years, N = 456, 58% females), or late adolescence (18-20 years, N = 144, 55% females). Three hundred seventy-nine participants (48.4%) received a bone-patellar tendon-bone autograft, 292 participants (37.3%) received hamstring tendon autograft, and 112 participants (14.3%) received autograft or allograft from an alternative source. CONCLUSION: Reference values for common patient-reported outcomes and measures of physical function and strength differed depending on a patient's age, sex, and graft source. Using patient-specific reference values, in addition to previously described age-appropriate cutoff values, may help clinicians monitor and progress patients through rehabilitation and return to physical activity after anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther 2023;53(4):1-8. Epub: 23 January 2023. doi:10.2519/jospt.2023.11389.

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.

The effect of traditional bridging or suspension-exercise bridging on lateral abdominal thickness in individuals with low back pain.

CONTEXT: Individuals with low back pain (LBP) are thought to benefit from interventions that improve motor control of the lumbopelvic region. It is unknown if therapeutic exercise can acutely facilitate activation of lateral abdominal musculature. OBJECTIVE: To investigate the ability of 2 types of bridging-exercise progressions to facilitate lateral abdominal muscles during an abdominal drawing-in maneuver (ADIM) in individuals with LBP. DESIGN: Randomized control trial. SETTING: University research laboratory. PARTICIPANTS: 51 adults (mean ± SD age 23.1 ± 6.0 y, height 173.6 ± 10.5 cm, mass 74.7 ± 14.5 kg, and 64.7% female) with LBP. All participants met 3 of 4 criteria for stabilization-classification LBP or at least 6 best-fit criteria for stabilization classification. INTERVENTIONS: Participants were randomly assigned to either traditional-bridge progression or suspension-exercise-bridge progression, each with 4 levels of progressive difficulty. They performed 5 repetitions at each level and were progressed based on specific criteria. MAIN OUTCOME MEASURES: Muscle thickness of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) was measured during an ADIM using ultrasound imaging preintervention and postintervention. A contraction ratio (contracted thickness:resting thickness) of the EO, IO, and TrA was used to quantify changes in muscle thickness. RESULTS: There was not a significant increase in EO (F1,47 = 0.44, P = .51) or IO (F1,47 = .30, P = .59) contraction ratios after the exercise progression. There was a significant (F1,47 = 4.05, P = .05) group-by-time interaction wherein the traditional-bridge progression (pre = 1.55 ± 0.22; post = 1.65 ± 0.21) resulted in greater (P = .03) TrA contraction ratio after exercise than the suspension-exercise-bridge progression (pre = 1.61 ± 0.31; post = 1.58 ± 0.28). CONCLUSION: A single exercise progression did not acutely improve muscle thickness of the EO and IO. The magnitude of change in TrA muscle thickness after the traditional-bridging progression was less than the minimal detectable change, thus not clinically significant.

Limb preference impacts single-leg forward hop limb symmetry index values following ACL reconstruction.

Following anterior cruciate ligament (ACL) reconstruction limb dominance for performing tasks is not considered when making rehabilitation progression decisions. The purpose of this study was to determine if strength and functional outcomes differ between individuals who injured their preferred or nonpreferred jumping limb and to determine if these same outcomes differ between individuals who injured their preferred or nonpreferred limb used to kick a ball. A secondary purpose was to determine the association of quadriceps strength and single-leg forward hop performance with patient self-reported function. Forty individuals with ACL reconstruction (age = 20.0 ± 4.6 years, height = 174.2 ± 12.7 cm, mass = 71.2 ± 12.7 kg, time since surgery = 5.3 ± 0.8 months) were included in the study. Primary outcome measures included, International Knee Documentation Committee Subjective Knee Form (IKDC) scores, quadriceps limb symmetry index (LSI) values, and single-leg forward hop LSI values. Limb preference was defined two ways, kicking a ball and performing a unilateral jump. There were no significant differences between groups based on injury to the preferred limb to kick a ball for any of the outcome variables. Individuals who injured their nonpreferred jumping limb demonstrated significantly (p = 0.05, d = 0.77) lower single-leg forward hop LSI values (81.1% ± 19.5%) compared to individuals who injured their preferred jumping limb (94.1% ± 12.6%), but demonstrated no differences in IKDC scores or quadriceps LSI values. Quadriceps LSI and single-leg forward hop LSI explained 73% of the variance in IKDC scores, but quadriceps LSI had the strongest association (r = 0.790). These findings suggests that limb preference influences single forward hop LSI values and should be considered following ACL reconstruction.

Prevalence of Early Knee Osteoarthritis Illness Among Various Patient-Reported Classification Criteria After Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: To compare the prevalence of participants meeting different patient-reported criteria for early osteoarthritis (OA) illness after anterior cruciate ligament reconstruction (ACLR). METHODS: Participants completed the Knee Injury and Osteoarthritis Outcomes Score (KOOS) at a single time point 5.0-7.9 months post-ACLR. We used established KOOS subscale criteria (i.e., Luyten original and Englund original) to define patient-reported early OA illness. A two-by-two contingency table and McNemar's test were used to compare the prevalence of participants who met the Luyten original versus Englund original KOOS criteria for early OA illness. These analyses were repeated using KOOS subscale thresholds based on established population-specific patient acceptable symptom state (PASS) within the Luyten and Englund KOOS criteria (i.e., Luyten PASS and Englund PASS). RESULTS: A greater prevalence of participants with ACLR met the Luyten original criteria (n = 165 [54%]) compared to those who met the Englund original criteria (n = 128 [42%]; χ2  = 19.3, P < 0.001). When using the KOOS subscale PASS as thresholds, a significantly greater prevalence of participants with ACLR met the Luyten PASS criteria (n = 133 [43%]) compared to those who met the Englund PASS criteria (n = 85 [28%]; χ2  = 48.0, P < 0.001). When combining the Luyten and Englund KOOS criteria and using the original/PASS subscale thresholds, respectively, 40%/57% of participants met neither, 24%/15% met only 1, and 36%/28% met both KOOS criteria. CONCLUSION: Regardless of the classification criteria used to define early OA illness, it is concerning that 28-54% of patients report considerable symptoms ~6 months post-ACLR. Our findings will improve the classification criteria to define early OA illness, which may raise awareness for the need of population-specific criteria.

Changes in lateral abdominal muscle thickness during an abdominal drawing-in maneuver in individuals with and without low back pain.

The purpose of this study was to compare lateral abdominal muscle thickness changes in individuals with and without low back pain (LBP) during an abdominal drawing-in maneuver (ADIM) using ultrasound imaging. Twenty individuals (13 females and 7 males, average age 40.1 ± 13.4) with stabilization classification LBP and 19 controls (10 females and 9 males, average age 30.3 ± 8.7) participated in this study. Bilateral measurements were made using ultrasound imaging to determine changes in thickness of the transversus abdominus (TrA) and external and internal oblique (EO+IO) muscles during an ADIM. There were no significant differences in relaxed muscle thickness values or contraction ratios for the TrA or EO+IO between groups or side. Individuals with stabilization classification LBP demonstrated no difference in lateral abdominal muscle thickness during an ADIM when compared with controls without LBP when using a pressure biofeedback device to monitor stability.

Shoulder Strength and Range of Motion in Healthy Collegiate Softball Players.

CONTEXT: Shoulder range of motion (ROM) and strength are key injury evaluation components for overhead athletes. Most normative values are derived from male baseball players, with limited information specific to female softball players. OBJECTIVE: To determine between-limbs differences in shoulder ROM and strength in healthy collegiate softball players. DESIGN: Descriptive laboratory study. SETTING: University research laboratory and collegiate athletic training room. PATIENTS OR OTHER PARTICIPANTS: Twenty-three healthy collegiate softball players (age = 19.9 ± 1.2 years, height = 170.5 ± 4.3 cm, mass = 78.4 ± 11.3 kg). MAIN OUTCOME MEASURE(S): Shoulder ROM (internal rotation [IR] and external rotation [ER]), isometric strength (IR, ER, flexion, abduction [135°], and horizontal abduction), and a measure of dynamic strength (Upper Quarter Y-Balance Test) were obtained. Paired-samples t tests were used to determine between-limbs differences for each outcome measure. RESULTS: Participants had more ER ROM (12° more) and less IR ROM (12° less) in the dominant arm, relative to the nondominant arm. No differences were present between limbs for any of the isometric strength measures or the Upper Quarter Y-Balance Test reach directions. CONCLUSIONS: Female collegiate softball players demonstrated typical changes in ER and IR ROM in the dominant arm and relatively symmetric performance across strength measures, which contrasts with previous findings in male baseball players.

EMG Activity With Use of a Hands-Free Single Crutch vs a Knee Scooter.

BACKGROUND: Foot and ankle injuries frequently require a period of nonweightbearing, resulting in muscle atrophy. Our previous study compared a hands-free single crutch (HFSC) to standard axillary crutches and found increased muscle recruitment and intensity while using the HFSC. Knee scooters are another commonly prescribed nonweightbearing device. The purpose of this study is to examine the electromyographic (EMG) differences between an HFSC and knee scooter, in conjunction with device preference and perceived exertion. METHODS: A randomized crossover study was performed using 30 noninjured young adults. Wireless surface EMG electrodes were placed on the belly of the rectus femoris (RF), vastus lateralis (VL), lateral gastrocnemius (LG), and gluteus maximus (GM). Participants then ambulated along a 20-m walking area while 15 seconds of the gait cycle was recorded across 3 conditions: walking with a knee scooter, an HFSC, and with no assistive device. Mean muscle activity and peak EMG activity were recorded for each ambulatory modality. Immediately following testing, patient exertion and device preference was recorded. RESULTS: The RF, LG, and GM showed increased peak EMG activity percentage, and the LG showed increased mean muscle activity while using the HFSC compared with the knee scooter. When comparing the knee scooter and HFSC to walking, both showed increased muscle activity in the RF, VL, and LG but no difference in the GM. There was no statistical difference in participant preference, whereas the HFSC had a statistically significant higher perceived exertion than the knee scooter (P < .001). CONCLUSION: In this group of young, healthy noninjured volunteers, the HFSC demonstrated increased peak EMG activity in most muscle groups tested compared with the knee scooter. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Effect of isolated hip abductor fatigue on single-leg landing mechanics and simulated ACL loading.

BACKGROUND: Altered movement biomechanics are a risk factor for ACL injury. While hip abductor weakness has been shown to negatively impact landing biomechanics, the role of this musculature and injury risk is not clear. The aim of this musculoskeletal simulation study was to determine the effect of hip abductor fatigue-induced weakness on ACL loading, force production of lower extremity muscles, and lower extremity biomechanics during single-leg landing. METHODS: Biomechanical data from ten healthy adults were collected before and after a fatigue protocol and used to derive subject-specific estimates of muscle forces and ACL loading using a 5-degree of freedom (DOF) model. RESULTS: There were no significant differences in knee joint angles and ACL loading between pre and post-fatigue. However, there were significant differences, due to fatigue, in lateral trunk flexion angle, total excursion of trunk, muscle forces, and joint moments. CONCLUSION: Altered landing mechanics, due to hip abductor fatigue-induced weakness, may be associated with increased risk of ACL injury during single-leg landings. Clinical assessment or screening of ACL injury risk will benefit from subject-specific musculoskeletal models during dynamic movements. Future study considering the type of the fatigue protocols, cognitive loads, and various tasks is needed to further identify the effect of hip abductor weakness on lower extremity landing biomechanics.

Blood Flow Restriction Training.

Muscle weakness and atrophy are common impairments after musculoskeletal injury. Blood flow restriction (BFR) training offers the ability to mitigate weakness and atrophy without overloading healing tissues. It appears to be a safe and effective approach to therapeutic exercise in sports medicine environments. This approach requires consideration of a wide range of factors, and the purpose of our article is to provide insights into proposed mechanisms of effectiveness, safety considerations, application guidelines, and clinical recommendations for BFR training after musculoskeletal injury. Whereas training with higher loads produces the most substantial increases in strength and hypertrophy, BFR training appears to be a reasonable option for bridging earlier phases of rehabilitation when higher loads may not be tolerated by the patient and later stages that are consistent with return to sport.

Quadriceps Strength Influences Patient Function More Than Single Leg Forward Hop During Late-Stage ACL Rehabilitation.

BACKGROUND: A comprehensive battery of tests are used to inform return to play decisions following anterior cruciate ligament (ACL) reconstruction. Performance measures contribute to patient function, but it is not clear if achieving symmetrical performance on strength and hop tests is sufficient or if a patient also needs to meet minimum unilateral thresholds. HYPOTHESIS/PURPOSE: To determine the association of quadriceps strength and single-leg forward hop performance with patient-reported function, as measured by the IKDC Subjective Knee Form (IKDC), during late-stage ACL rehabilitation. A secondary purpose was to determine which clinical tests were the most difficult for participants to pass. STUDY DESIGN: Descriptive Laboratory Study. METHODS: Forty-eight individuals with a history of ACL-R (32 female, 16 male; mean±SD age=18.0±2.7 y; height=172.4±7.6 cm; mass=69.6±11.4 kg; time since surgery=7.7±1.8 months; IKDC=86.8±10.6) completed the IKDC survey, quadriceps isometric strength, and single-leg forward hop performance. The relationship between IKDC scores and performance measures (LSI and involved limb) was determined using stepwise linear regression. Frequency counts were used to determine whether participants met clinical thresholds (IKDC ≥ 90%, quadriceps and single-leg forward hop LSI ≥ 90%, quadriceps peak torque ≥ 3.0 Nm/kg, and single-leg forward hop ≥ 80% height for females and ≥ 90% height for males). RESULTS: Quadriceps LSI and involved limb peak torque explained 39% of the variance in IKDC scores while measures of single-leg forward hop performance did not add to the predictive model. Nearly 90% of participants could not meet established clinical thresholds on all five tests and quadriceps strength (LSI and peak torque) was the most common unmet criteria (71% of participants). CONCLUSIONS: During late-stage ACL rehabilitation deficits in quadriceps strength contribute more to patient function and are greater in magnitude compared to hop test performance. LEVEL OF EVIDENCE: Cross-Sectional Study, Level 3.