Running biomechanics differ during and after pregnancy compared to females who have never been pregnant.

BACKGROUND: Perinatal running participation has increased recently; however, pregnancy related symptoms can limit activity. Perinatal running biomechanics could inform interventions to help perinatal individuals maintain an active lifestyle. RESEARCH QUESTION: Are perinatal running biomaechanics and muscle activation different compared to nulligravida females? METHODS: Sixteen pregnant participants completed self-selected velocity running during second trimester (2 T), third trimester (3 T), and postpartum (PP) and 16 matched controls completed these procedures once in this case control study. Kinematic, kinetic, and electromyography (EMG) data were collected using a motion capture system, force plates, and EMG electrodes. Peak trunk, pelvis, hip, knee, and ankle kinematics and hip, knee, and ankle moments during stance phase, and average and peak erector spinae (ES), gluteus maximus (GMax), and gluteus medius (GMed) EMG amplitude and duration of activation during stance and swing phases were calculated. Independent t-tests were used to compare 2 T, 3 T, and PP to control participants (α < 0.05). RESULTS: Running velocity was slower during 3 T compared to control participants. At all pregnancy timepoints compared to the control group, peak trunk contralateral rotation was smaller. During 2 T and 3 T peak hip flexor moments were smaller. At 3 T pelvis contralateral rotation was smaller, ES average amplitude was greater during swing, GMax percent duration during stance and GMed percent duration during swing were smaller. At PP trunk flexion was smaller and knee abduction was greater (all p < 0.05). CONCLUSIONS: Decreased running velocity may help offset increased demand during pregnancy. During 3 T, greater ES activation, smaller trunk and pelvis motion, and altered gluteal activation could indicate trunk rigidity combined with modified hip stabilizer muscle utilization. During PP, the rigid trunk combined with greater knee abduction may indicate hip and trunk strength deficits. Altered trunk and hip motion and activation could be relevant to pathologies such as perinatal low back, pelvic girdle, or knee pain.

Development of Infant Sitting Postural Control in Three Groups of Infants at Various Risk Levels for Autism Spectrum Disorder.

The purpose of this study was to examine the development of sitting postural control among two groups of infants at elevated risk for autism spectrum disorders (ASD) and a group of infants at typical risk for ASD and its association with cognitive, language and communication skills at a later age. We visited infants in their home environment from the onset of sitting until sitting independence and at 12 and 18 months of age. We collected data on sitting posture (center of pressure), through a portable force platform, as well as communication, cognitive and social behavior assessments at various time points. Our results showed that postural control differences at the onset of sitting, were present among the groups of infants but there were no statistically significant differences among the groups in the development of sitting posture. In addition, there were statistically significant communication differences among the groups and mostly the change in sample entropy in the anterior/posterior direction (posture measure) was significantly correlated with other skills at a later age. This study highlights the importance of investigating multiple at-risk groups to identify unique developmental pathways that may lead to an ASD diagnosis.

Center of pressure characteristics differ during single leg stance throughout pregnancy and compared to nulligravida individuals.

BACKGROUND: Falls are common during pregnancy and present potential for injury to the pregnant individual and the baby. RESEARCH QUESTION: Do center of pressure characteristics during single leg stance differ between participants during and after pregnancy and nulligravida participants in the presence and absence of visual input? METHODS: Nineteen pregnant participants completed testing during the second trimester, the third trimester, and 4-6 months post-partum. Matched, nulligravida females completed testing once. All participants performed single leg stance on a force platform on each limb for up to 20 s with eyes open and with eyes closed. Center of pressure characteristics were compared between pregnant and nulligravida females using three separate 2 × 2 mixed way ANOVAs, one for each pregnancy time point (second trimester, third trimester, and post-partum) with Bonferroni correction. RESULTS: Pregnant females demonstrated smaller single leg stance time with eyes closed during the third trimester. During the second and third trimester, pregnant participants demonstrated smaller sway and sway velocity across eyes open and eyes closed conditions. During the third trimester and post-partum, pregnant participants demonstrated greater median frequency of the center of pressure data. Pregnant participants also demonstrated smaller sample entropy in the anteroposterior direction during the second and third trimesters and in the mediolateral direction during the second trimester. SIGNIFICANCE: The decreased total sway and sway velocity observed during pregnancy may reflect rigidity or a protective strategy during single limb stance. Additionally, center of pressure data were less smooth and more repetitive during pregnancy indicating robust differences in postural control strategies and potentially increased fall risk. Because single limb stance is a component of many activities of daily living, the single limb stance task may have clinical utility for testing or training balance in this population with a goal of decreasing falls.

An exploratory analysis of gait biomechanics and muscle activation in pregnant females with high and low scores for low back or pelvic girdle pain during and after pregnancy.

BACKGROUND: The purpose of this study was to compare gait kinematics, kinetics, and muscle activation between pregnant females with high and low scores for low back and/or pelvic girdle pain during and after pregnancy. METHODS: Twenty participants tested during second trimester, third trimester, and again post-partum. At each session, motion capture, force plates, and surface electromyography data were captured during self-selected velocity over-ground walking. Participants completed the Quebec Back Pain Disability Scale (QBPDS) and were assigned to high (QBPDS ≥15) or low pain groups (QBPDS <15) based on third trimester scores. Two-way mixed model ANOVAs were used to compare high and low pain groups over time. FINDINGS: Nine participants met the high pain group criteria and 11 were low pain. During second trimester the high pain group compared to the low pain group demonstrated smaller peak hip flexor moments, total hip work, percent hip contribution to work, and larger percent ankle contribution to work. Pregnant females demonstrated greater hip, knee, and ankle moments, ankle work, and gluteus maximus muscle activation third trimester than second trimester. INTERPRETATION: Reduced hip and greater ankle contribution to work in the high pain group during second trimester could indicate decreased hip utilization early in pregnancy and may contribute to disability as pregnancy progresses. It is also possible kinetic differences during second trimester reflect an early strategy to reduce pain by avoiding hip joint loading. Increased moments and work during third trimester indicate a clinical imperative to better prepare pregnant females to accommodate increased joint loading and muscular demand.

Validity of the Wattbike 3-Minute Aerobic Test: Measurement and Estimation of V̇o2max.

ABSTRACT: Hanson, NJ, Scheadler, CM, Katsavelis, D, and Miller, MG. Validity of the Wattbike 3-minute aerobic test: measurement and estimation of V̇o2max. J Strength Cond Res 36(2): 400-404, 2022-The Wattbike includes a 3-minute aerobic test (3mAT) along with an estimation of V̇o2max. The estimation equation that is used is from a previous study using a different protocol and sedentary subjects. The purpose of this study was to determine whether (a) the 3mAT is able to elicit V̇o2max, and (b) whether this estimation is accurate. Thirteen cyclists (10 men; age: 29.2 ± 10.0 years, height 178.7 ± 8.3 cm, and mass 75.1 ± 12.5 kg) with a range of experience volunteered for this study. At the first visit, a self-paced V̇o2max (SPV) test was performed to obtain the "true" V̇o2max. At the second session, subjects completed the 3mAT. Primary dependent variables included maximal values of oxygen consumption (V̇o2), carbon dioxide production (V̇co2), heart rate (HR), ventilation (VE), and respiratory exchange ratio (RER). A repeated-measures analysis of variance showed no difference (p = 0.367) between V̇o2max values (3mAT estimation: 54.3 ± 9.3 ml·kg-1·min-1, 3mAT measured: 52.5 ± 8.7, SPV: 54.0 ± 9.7). Paired-samples t-tests showed that HR (p = 0.027) was higher in the SPV (184.7 ± 10.6 vs. 180.9 ± 6.3 b·min-1), whereas RER and V̇co2 were both higher in the 3mAT (1.29 ± 0.10 vs. 1.19 ± 0.06 and 4.92 ± 1.01 vs. 4.62 ± 0.98, respectively; both p < 0.05). The intraclass correlation between the V̇o2max measured from the SPV and 3mAT was 0.96 (95% CI: 0.88-0.99, p < 0.001), and between the 3mAT measured and estimated values was 0.91 (95% CI: 0.71-0.97 p < 0.001). If an athlete has access to a Wattbike, they can complete the 3mAT, receive their V̇o2max estimation, and be confident of its accuracy.

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.

Identifying Gait-Related Functional Outcomes in Post-Knee Surgery Patients Using Machine Learning: A Systematic Review.

Modern lifestyles require new tools for determining a person's ability to return to daily activities after knee surgery. These quantitative instruments must feature high discrimination, be non-invasive, and be inexpensive. Machine learning is a revolutionary approach that has the potential to satisfy the aforementioned requirements and bridge the knowledge gap. The scope of this study is to summarize the results of a systematic literature review on the identification of gait-related changes and the determination of the functional recovery status of patients after knee surgery using advanced machine learning algorithms. The current systematic review was conducted using multiple databases in accordance with the PRISMA guidelines, including Scopus, PubMed, and Semantic Scholar. Six out of the 405 articles met our inclusion criteria and were directly related to the quantification of the recovery status using machine learning and gait data. The results were interpreted using appropriate metrics. The results demonstrated a recent increase in the use of sophisticated machine learning techniques that can provide robust decision-making support during personalized post-treatment interventions for knee-surgery patients.

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.

Lower extremity kinetics and muscle activation during gait are significantly different during and after pregnancy compared to nulliparous females.

BACKGROUND: Low back, pelvic, and lower extremity pain are common during and after pregnancy. Understanding differences in mechanics between pregnant and non-pregnant females is a first step toward identifying potential pathological mechanisms. The primary purpose of this study was to compare joint kinetics and muscle activation during gait between females during and after pregnancy to nulliparous females. METHODS: Twenty pregnant females completed testing on three occasions (second trimester, third trimester, and post-partum), while 20 matched, nulliparous controls were tested once. Motion capture, force data, and surface electromyography were averaged across seven trials during gait. Lower extremity kinematics, lower extremity moments and work normalized to pre-pregnancy body mass, work distribution, and peak and average muscle activation amplitude were calculated. Independent t-tests were conducted between pregnant and nulliparous females at each time point. RESULTS: Compared to controls, peak hip abductor moments were greater throughout and after pregnancy. Females in second trimester also demonstrated greater sagittal negative ankle work and greater percent contribution of the ankle and smaller percent contribution of the hip to negative work. Compared to controls, during third trimester there were greater knee abductor, ankle plantarflexor, and ankle dorsiflexor moments and greater work at the ankle and total work. Several moment and work variables continued to be elevated post-partum compared to controls. Gluteus maximus muscle activation amplitude was smaller in second trimester and post-partum compared to controls. SIGNIFICANCE: While overall joint demands were greater during and after pregnancy, there was a smaller relative sagittal utilization of the hip early in pregnancy and smaller gluteus maximus muscle amplitude during second trimester and post-partum. Because the gluteus maximus muscle contributes to force closure and dynamic stability of the low back and pelvis, relative gluteus maximus disuse, concurrent with increased joint loads, could potentially contribute to pain during and after pregnancy.

Measurement of Pectoralis Minor Muscle Length in Women Diagnosed With Breast Cancer: Reliability, Validity, and Clinical Application.

BACKGROUND: Decreased pectoralis minor muscle length is common after primary breast cancer treatment and can result in an abnormal position of the scapula. This position can contribute to shoulder pain and pathomechanics and can lead to problems such as impingement syndrome, rotator cuff tears, and frozen shoulder. Currently, there are limited reliable methods for measuring pectoralis minor length. OBJECTIVE: The objective of this study was to examine the reliability and validity of measuring pectoralis minor length in women diagnosed with breast cancer. DESIGN: This was a cross-sectional reliability and validity study. METHODS: Bilateral pectoralis minor length (in centimeters) was assessed using a palpation meter in women (N = 29) diagnosed with breast cancer by 2 licensed physical therapists who were masked to the measures. Bilateral pectoralis minor length was also measured using a motion capture system to assess validity. RESULTS: Intratester reliability (intraclass correlation coefficient, ICC [3,k] = 0.971; 95% confidence interval [CI] = 0.939-0.986; standard error of measurement [SEM] = 0.16 cm) and intertester reliability (ICC[3,k] = 0.915; 95% CI = 0.81-0.962; SEM = 0.31 cm) were excellent for the palpation meter on the affected side and the unaffected side (intratester reliability: ICC[3,k] = 0.951; 95% CI = 0.897-0.977; SEM = 0.19 cm; intertester reliability: ICC[3,k] = 0.945; 95% CI = 0.877-0.975; SEM = 0.22 cm). Significant correlations were found between the motion capture system and the palpation meter on the affected side (r = 0.87) and the unaffected side (r = 0.81). Bland-Altman plots between the palpation meter and the motion capture system demonstrated that all the measures fell within the limits of agreement. LIMITATIONS: This study encountered possible errors with the accuracy of the motion capture system tracking because of the proximity of the markers and inherent volumetric restrictions. CONCLUSIONS: The palpation meter is a reliable, valid, easily administered, and cost-effective tool for assessing pectoralis minor length in women with breast cancer.

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.

VALIDITY OF HAND-HELD DYNAMOMETRY IN MEASURING QUADRICEPS STRENGTH AND RATE OF TORQUE DEVELOPMENT.

BACKGROUND: A hand-held dynamometer (HHD) offers a reliable and valid method to quantify quadriceps strength in a clinical environment. While measures of peak strength provide functional insights, most daily activities are performed quickly and do not require maximum strength. Rate of torque development (RTD) measures better reflect both the demands of daily activity and athletic movements. The capacity to obtain RTD measures in clinical settings is possible with an HHD, but the validity of RTD measures has not been quantified. HYPOTHESIS/PURPOSE: To determine the validity of an HHD to measure quadriceps isometric strength metrics compared to isometric strength measures obtained on an isokinetic dynamometer. It was hypothesized that the HHD would be a valid measure of peak torque and RTD at all time intervals when compared to the isokinetic dynamometer. STUDY DESIGN: Descriptive laboratory study. METHODS: Twenty healthy participants (12 male, 8 female) (age = 23.7 ± 2.9 years, height = 174.6 ± 10.1 cm, mass = 76.4 ± 15.9 kg, and Tegner = 6.7 ± 1.2) performed maximum isometric quadriceps contractions on an isokinetic dynamometer and with an HHD. Outcome measures included quadriceps peak torque and RTD at three intervals (0-100, 0-250 ms, and average). Pearson product-moment correlation coefficients and Spearman's rank correlation coefficient were used to determine relationships between devices. Bland-Altman Plots with Limits of Agreement (LOA) calculations were used to quantify systematic bias between measurement techniques. RESULTS: There was a significant correlation between the isokinetic dynamometer and the HHD for peak torque (p<.001, r = .894) and all RTD measurements (p<.002, r = .807; ρ = .502-.604). Bland-Altman plot LOA indicated the HHD overestimated peak torque values (19.4 ± 53.2 Nm) and underestimated all RTD measurements (-55.2 ± 190.7 Nm/s to -265.2 ± 402.6 Nm/s). CONCLUSION: These results show it is possible to obtain valid measures of quadriceps peak torque and late RTD using an HHD. Measures of early RTD and RTDAvg obtained with an HHD were more variable and should be viewed with caution. LEVEL OF EVIDENCE: Diagnostic, Level 3.

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.

COMPARISON OF CLINICAL FATIGUE PROTOCOLS TO DECREASE SINGLE-LEG FORWARD HOP PERFORMANCE IN HEALTHY INDIVIDUALS.

BACKGROUND: Return to activity decisions after anterior cruciate ligament reconstruction (ACL-R) are limited by functional performance tests often performed in a non-fatigued state. Fatigue can improve test sensitivity, but current methods to induce fatigue are typically bilateral tasks or focus on the quadriceps muscle in isolation. HYPOTHESIS/PURPOSE: To determine the effects of a two-minute lateral step-down fatigue test compared to a 30-second side-hop test on single-leg forward hop distance in healthy individuals. It was hypothesized that participants would demonstrate decreased hop distance with both tests, but the two-minute lateral step-down fatigue test would result in greater deficits in single-leg forward hop distance. STUDY DESIGN: Randomized crossover. METHODS: Twenty healthy participants (16 females, 4 males; age = 23.7±3.0 years, height = 153.8±36.2 cm; mass = 64.4±12.8 kg; Tegner = 6.8±1.2) were asked to perform single-leg forward hop for distance pre- and post-fatigue. Participants were randomly assigned to one of the two fatigue tests, 30-second side-hop or 2-minute lateral step-down test, during the first visit. They returned within a week and performed the same sequence of tests but underwent whichever fatigue test was not assigned at the prior visit. RESULTS: There was a significant decrease (p < 0.001) in single-leg forward hop distance following the 30-second side-hop test (pre = 134.1±23.7 cm, post = 126.2±24.4 cm) and the two-minute lateral step-down test (pre = 135.0±26.1 cm, post = 122.7±27.4 cm). The decrease in hop distance was significantly greater (p < 0.001) for the two-minute lateral step-down test compared to the 30-second side-hop test. CONCLUSION: The two-minute lateral step-down test resulted in a greater decrease in hop performance compared to the 30-second side-hop test. The results establish a threshold for expected changes that occur in a healthy population and that can then be compared with an injured athlete population. The two-minute lateral step-down exercise may be an effective method of inducing fatigue to better mimic performance in a sports environment to inform return-to-sport decisions. LEVEL OF EVIDENCE: Level 1b- Therapy.

Common carotid artery peak systolic velocity ratio predicts high-grade common carotid stenosis.

OBJECTIVE: Screening for common carotid artery (CCA) stenosis with duplex ultrasound (DUS) velocity criteria alone can be limited by within-patient and between-patients hemodynamic variability. This study aimed to evaluate inter-CCA velocity ratio criteria to predict high-grade CCA stenosis. METHODS: This was a retrospective review of consecutive patients who underwent computed tomography angiography and DUS peak systolic velocity (PSV) measurements of bilateral CCAs, independently recorded, between 2008 and 2014. Patients with dampened CCA waveforms on DUS composed group B. The remainder without dampened waveforms constituted group A. Inter-CCA PSV ratios were calculated by dividing the higher CCA PSV by the lower one of the other side, so the ratios would always be ≥1. Ratios were subsequently paired with each respective unilateral CCA diameter stenosis and differential bilateral CCA diameter stenosis. A quadratic regression model was fitted to predict unilateral and differential stenosis. Receiver operating characteristic curve was used to determine optimal ratios for ≥50% and ≥80% CCA stenosis. The study excluded patients with carotid artery occlusion. RESULTS: From a total of 201 patients, 193 patients were included in group A and 8 in group B. Within group A, 31 patients had ≥50% unilateral stenosis and 17 had ≥50% differential stenosis. All stenoses ≥50% were identified on the same side with the higher PSV. Inter-CCA PSV ratio predicted ≥50% unilateral (r(2) = 0.536; P < .001) and differential stenosis (r(2) = 0.581; P < .001). In group B, all patients had ≥60% stenosis that was near or involved the vessel origin. An increasing inter-CCA PSV ratio showed a trend toward contralateral high-grade stenosis (r(2) = 0.596; P = .1). Receiver operating characteristic curves showed an optimal threshold CCA ratio ≥2.16 for ≥50% unilateral stenosis with 92% accuracy, 62% sensitivity, and 98% specificity (area under curve = 0.854; 95% confidence interval, 0.759-0.948) and a ratio ≥2.62 for ≥50% differential stenosis with 97% accuracy, 83% sensitivity, and 98% specificity (area under curve = 0.94; 95% confidence interval, 0.835-1). CONCLUSIONS: DUS-based CCA PSV ratio can accurately predict unilateral and differential high-grade CCA stenosis. Also, in patients with unilateral dampened waveforms, it implied contralateral severe proximal stenosis. This parameter should be further validated in prospective studies and may serve as an adjunct screening tool to detect high-grade CCA stenosis.

Cyborg beast: a low-cost 3d-printed prosthetic hand for children with upper-limb differences.

BACKGROUND: There is an increasing number of children with traumatic and congenital hand amputations or reductions. Children's prosthetic needs are complex due to their small size, constant growth, and psychosocial development. Families' financial resources play a crucial role in the prescription of prostheses for their children, especially when private insurance and public funding are insufficient. Electric-powered (i.e., myoelectric) and body-powered (i.e., mechanical) devices have been developed to accommodate children's needs, but the cost of maintenance and replacement represents an obstacle for many families. Due to the complexity and high cost of these prosthetic hands, they are not accessible to children from low-income, uninsured families or to children from developing countries. Advancements in computer-aided design (CAD) programs, additive manufacturing, and image editing software offer the possibility of designing, printing, and fitting prosthetic hands devices at a distance and at very low cost. The purpose of this preliminary investigation was to describe a low-cost three-dimensional (3D)-printed prosthetic hand for children with upper-limb reductions and to propose a prosthesis fitting methodology that can be performed at a distance. RESULTS: No significant mean differences were found between the anthropometric and range of motion measurements taken directly from the upper limbs of subjects versus those extracted from photographs. The Bland and Altman plots show no major bias and narrow limits of agreements for lengths and widths and small bias and wider limits of agreements for the range of motion measurements. The main finding of the survey was that our prosthetic device may have a significant potential to positively impact quality of life and daily usage, and can be incorporated in several activities at home and in school. CONCLUSIONS: This investigation describes a low-cost 3D-printed prosthetic hand for children and proposes a distance fitting procedure. The Cyborg Beast prosthetic hand and the proposed distance-fitting procedures may represent a possible low-cost alternative for children in developing countries and those who have limited access to health care providers. Further studies should examine the functionality, validity, durability, benefits, and rejection rate of this type of low-cost 3D-printed prosthetic device.

Quantifying thigh muscle co-activation during isometric knee extension contractions: within- and between-session reliability.

Muscle co-activation around the knee is important during ambulation and balance. The wide range of methodological approaches for the quantification of co-activation index (CI) makes comparisons across studies and populations difficult. The present study determined within- and between-session reliability of different methodological approaches for the quantification of the CI of the knee extensor and flexor muscles during maximum voluntary isometric contractions (MVICs). Eight healthy volunteers participated in two repeated testing sessions. A series of knee extension MVICs of the dominant leg with concomitant torque and electromyographic (EMG) recordings were captured. CI was calculated utilizing different analytical approaches. Intraclass correlation coefficient (ICC) showed that within-session measures displayed higher reliability (ICC>0.861) and lower variability (Coefficient of variation; CV<21.8%) than between-session measures (ICC<0.645; CV>24.2%). A selection of a 500ms or larger window of RMS EMG activity around the PT delivered more reliable and less variable results than other approaches. Our findings suggest that the CI can provide a reliable measure for comparisons among conditions and is best utilized for within-session experimental designs.

The influence of visual perception of self-motion on locomotor adaptation to unilateral limb loading.

Self-perception of motion through visual stimulation may be important for adapting to locomotor conditions. Unilateral limb loading is a locomotor condition that can improve stability and reduce abnormal limb movement. In the present study, the authors investigated the effect of self-perception of motion through virtual reality (VR) on adaptation to unilateral limb loading. Healthy young adults, assigned to either a VR or a non-VR group, walked on a treadmill in the following 3 locomotor task periods--no load, loaded, and load removed. Subjects in the VR group viewed a virtual corridor during treadmill walking. Exposure to VR reduced cadence and muscle activity. During the loaded period, the swing time of the unloaded limb showed a larger increase in the VR group. When the load was removed, the swing time of the previously loaded limb and the stance time of the previously unloaded limb showed larger decrease and the swing time of the previously unloaded limb showed a smaller increase in the VR group. Lack of visual cues may cause the adoption of cautious strategies (higher muscle activity, shorter and more frequent steps, changes in the swing and stance times) when faced with situations that require adaptations. VR technology, providing such perceptual cues, has an important role in enhancing locomotor adaptation.

The effect of virtual reality on gait variability.

Optic Flow (OF) plays an important role in human locomotion and manipulation of OF characteristics can cause changes in locomotion patterns. The purpose of the study was to investigate the effect of the velocity of optic flow on the amount and structure of gait variability. Each subject underwent four conditions of treadmill walking at their self-selected pace. In three conditions the subjects walked in an endless virtual corridor, while a fourth control condition was also included. The three virtual conditions differed in the speed of the optic flow displayed as follows--same speed (OFn), faster (OFf), and slower (OFs) than that of the treadmill. Gait kinematics were tracked with an optical motion capture system. Gait variability measures of the hip, knee and ankle range of motion and stride interval were analyzed. Amount of variability was evaluated with linear measures of variability--coefficient of variation, while structure of variability i.e., its organization over time, were measured with nonlinear measures--approximate entropy and detrended fluctuation analysis. The linear measures of variability, CV, did not show significant differences between Non-VR and VR conditions while nonlinear measures of variability identified significant differences at the hip, ankle, and in stride interval. In response to manipulation of the optic flow, significant differences were observed between the three virtual conditions in the following order: OFn greater than OFf greater than OFs. Measures of structure of variability are more sensitive to changes in gait due to manipulation of visual cues, whereas measures of the amount of variability may be concealed by adaptive mechanisms. Visual cues increase the complexity of gait variability and may increase the degrees of freedom available to the subject. Further exploration of the effects of optic flow manipulation on locomotion may provide us with an effective tool for rehabilitation of subjects with sensorimotor issues.

Variability of lower extremity joint kinematics during backward walking in a virtual environment.

Backward walking (BW) shows significant differences with forward walking (FW) and these differences are potentially useful in rehabilitation. However the lack of visual cues makes BW risky. The purpose of this study was to investigate the effect of visual cues provided by a virtual environment on FW and BW on gait variability. Each subject underwent four conditions of treadmill walking at self-selected pace. The subjects walked backwards in three conditions and forwards in the fourth condition. A virtual corridor was displayed to the subjects in the FW condition (forward optic flow) and two of the backward conditions (forward and backward optic flow). The third BW condition was a control condition (no visual cues). Gait variability measures of the hip, knee and ankle range of motion and the stride interval were analyzed. Magnitude of variability was evaluated with the coefficient of variation and structure of variability with approximate entropy. Significant differences were demonstrated between the FW and the BW gait characteristics as well as in gait variability (for both magnitude and structure of variability). No significant differences were found between the three BW conditions as a result of the direction of visual cues. In order to get optimal benefit of BW in the aged and the diseased, optical flow of visual feedback may need to be manipulated in a different manner than FW. Future studies will explore other parameters of visual cues like the velocity of optic flow and appearance of obstacles to obtain the best visual cue configuration for rehabilitation.