Impact of combined lumbar spine fusion and total hip arthroplasty on spine, pelvis, and hip kinematics during a sit to stand task.

Lumbar fusion is a risk factor for hip dislocation following total hip arthroplasty (THA). The objective was to compare joint/segment angles during sit-stand-sit in participants that had a THA with and without a lumbar fusion. The secondary objective was to compare pain, physical function, disability, and quality of life. This cross-sectional study includes participants that had THA and lumbar fusion (THA-fusion; n = 12) or THA only (THA-only; n = 12). Participants completed sit-stand-sit trials. Joint/segment angles were measured using electromagnetic motion capture. Angle characteristics were determined using principal component analysis. Hierarchical linear models examined relationships between angle characteristics and groups. Pain, physical function, and disability were compared using Mann-Whitney U tests. Upper lumbar spine was more extended during sit-stand-sit in the THA-fusion group (b = 42.41, P = 0.04). The pelvis was more posteriorly and anteriorly tilted during down and end sit-stand-sit phases, respectively, in the THA-fusion group (b = 12.21, P = 0.03). There were no significant associations between group and other angles. THA-fusion group had worse pain, physical function, disability, and quality of life. Although differences in spine joint, pelvis segment, and hip joint angles existed, these findings are unlikely to account for the increased incidence of hip dislocation after total hip arthroplasty in patients that had spine fusion.

Inter-segment coordination amplitude and variability during gait in patients with knee osteoarthritis and asymptomatic adults.

BACKGROUND: Inter-segment coordination examines the timing and coupling of multiple body segments and provides a complex understanding of how the neuromuscular system controls the body. Research is required to examine if inter-segment coordination during gait differs between individuals with different knee osteoarthritis (OA) severities and asymptomatic adults. RESEARCH QUESTION: Do inter-segment coordination amplitude and between-trial variability during gait differ between individuals with varying levels of knee OA severity and asymptomatic adults? METHODS: This observational, cross-sectional study included participants with mild/moderate knee OA (n = 38), severe knee OA (n = 24), and asymptomatic adults (n = 51). Participants ambulated overground at self-selected speeds. Data were collected with an eight-camera motion capture system and two force plates. Continuous relative phase (CRP) was used to quantify sagittal plane inter-segment coordination amplitude and between-trial variability for the thigh-shank and shank-foot pairs. Hierarchical linear models examined if CRP variables were related to the group (asymptomatic, mild/moderate OA, severe OA) after accounting for gait speed and gait phase. RESULTS: Thigh-shank CRP amplitude was significantly associated with group variables. The severe OA group had lower CRP amplitudes than both asymptomatic (b=8.57, 95 % confidence interval=2.75-14.38) and mild/moderate OA (b=5.69, 95 % confidence interval=-0.25 to 11.62) groups. Thigh-shank CRP variability was also associated with group. The severe OA group had lower CRP variability than the asymptomatic group (b=0.45, 95 % confidence interval=0.12-0.78); there were no differences between severe and mild/moderate OA groups (p > 0.050). There were no significant associations between any of the shank-foot CRP measures and the groups. SIGNIFICANCE: Lower thigh-shank CRP amplitude and variability in individuals with severe knee OA represents a more rigid motor system. These individuals could be attempting to stabilize their knee in response to a loss of passive stability or in response to pain. They might have difficulty adapting their gait to perturbations.

The Association of Age and Sex With Joint Angles and Coordination During Unanticipated Cutting in Soccer Players.

Deficits in movement patterns during cutting while running might place soccer players at risk of injury. The objective was to compare joint angles and intersegment coordination between sexes and ages during an unanticipated side-step cutting task in soccer players. This cross-sectional study recruited 11 male (four adolescents and seven adults) and 10 female (six adolescents and four adults) soccer players. Three-dimensional motion capture was used to measure lower-extremity joint and segment angles as participants performed an unanticipated cutting task. Hierarchical linear models examined relationships between joint angle characteristics with age and sex. Continuous relative phase was used to quantify intersegment coordination amplitude and variability. These values were compared between age and sex groups using analysis of covariance. Adult males had greater hip flexion angle excursions than adolescent males, while adult females had smaller excursions than adolescent females (p = .011). Females had smaller changes in hip flexion angles (p = .045), greater hip adduction angles (p = .043), and greater ankle eversion angles (p = .009) than males. Adolescents had greater hip internal rotation (p = .044) and knee flexion (p = .033) angles than adults, but smaller changes in knee flexion angles at precontact compared with stance/foot off (p < .001). For intersegment coordination, females were more out-of-phase than males in the foot/shank segment in the sagittal plane. There were no differences in intersegment coordination variability between groups. Differences in joint motion during an unanticipated cutting task were present between age groups and sexes. Injury prevention programs or training programs may be able target specific deficits to lower injury risk and improve performance.

Differences in inter-segment coordination between high- and low-calibre ice hockey players during forward skating.

The objective was to compare lower extremity inter-segment coordination between high-calibre and low-calibre ice hockey players during forward full stride skating. A 10-camera Vicon motion capture system collected kinematic data on male high-calibre (n = 8) and low-calibre (n = 8) participants. Continuous relative phase (CRP) was calculated for shank-sagittal/thigh-sagittal, shank-sagittal/thigh-frontal and foot-sagittal/shank-sagittal segment pairs. Principal component analysis (PCA) was used to extract features of greatest variability of the CRP and hierarchical linear model investigated relationships between principal components and skill level. High-calibre players demonstrated more out-of-phase coordination (higher CRP) of shank-sagittal/thigh-sagittal throughout glide/push-off (p = 0.011) as well as a delay in the transition to more in-phase coordination during early recovery phase (p = 0.014). For shank-sagittal/thigh-frontal (p = 0.013), high-calibre players had more out-of-phase coordination throughout the entire stride. High-calibre players were also associated with an earlier transition to more out-of-phase coordination of the foot-sagittal/shank-sagittal during push-off (p = 0.007) and a smaller difference in CRP between mid-glide/early recovery (p = 0.016). Utilising more out-of-phase modes of coordination may allow players to more easily adjust to optimal modes of coordination throughout skating strides. Skating drills incorporating varying speed, directionality and external stimuli may encourage the development of more optimal coordination during skating.

Pilot Study of Embedded IMU Sensors and Machine Learning Algorithms for Automated Ice Hockey Stick Fitting.

The aims of this study were to evaluate the feasibility of using IMU sensors and machine learning algorithms for the instantaneous fitting of ice hockey sticks. Ten experienced hockey players performed 80 shots using four sticks of differing constructions (i.e., each stick differed in stiffness, blade pattern, or kick point). Custom IMUs were embedded in a pair of hockey gloves to capture resultant linear acceleration and angular velocity of the hands during shooting while an 18-camera optical motion capture system and retroreflective markers were used to identify key shot events and measure puck speed, accuracy, and contact time with the stick blade. MATLAB R2020a's Machine Learning Toolbox was used to build and evaluate the performance of machine learning algorithms using principal components of the resultant hand kinematic signals using principal components accounting for 95% of the variability and a five-fold cross validation. Fine k-nearest neighbors algorithms were found to be highly accurate, correctly classifying players by optimal stick flex, blade pattern, and kick point with 90-98% accuracy for slap shots and 93-97% accuracy for wrist shots in fractions of a second. Based on these findings, it appears promising that wearable sensors and machine learning algorithms can be used for reliable, rapid, and portable hockey stick fitting.

Vastus medialis intramuscular fat is associated with reduced quadriceps strength, but not knee osteoarthritis severity.

BACKGROUND: Vastus medialis intramuscular fat has been proposed to be a modifiable determinant of knee cartilage loss in patients with knee osteoarthritis. The objective was to determine whether vastus medialis intramuscular fat relates to osteoarthritis severity and quadriceps muscle strength in patients with non-traumatic and post-traumatic knee osteoarthritis. METHODS: For this cross-sectional study, participants with knee osteoarthritis were classified into two groups: non-traumatic (n = 22; mean age = 60 years) and post-traumatic (n = 19; mean age = 56 years). Healthy adults were included (n = 22; mean age = 59 years). A 3-Tesla magnetic resonance imaging was used to measure vastus medialis cross-sectional area and intramuscular fat. Isometric knee extensor muscle torque was assessed using an isokinetic dynamometer and normalized to body mass (Nm/kg). Knee osteoarthritis severity was assessed using standing antero-posterior radiographs (Kellgren-Lawrence scores). Regression analyses examined relationships between 1) vastus medialis intramuscular fat with knee osteoarthritis severity and osteoarthritis group, after accounting for sex and body mass index, and 2) knee extensor muscle torque with vastus medialis intramuscular fat, after accounting for sex and vastus medialis cross-sectional area. FINDINGS: Vastus medialis intramuscular fat was positively associated with body mass index (B = 0.321, P < 0.001), but not with osteoarthritis severity or group (P > 0.05). Higher vastus medialis intramuscular fat was associated with reduced knee extensor muscle torque (B = -0.040, P = 0.018). INTERPRETATION: Greater vastus medialis intramuscular fat was associated with lower quadriceps muscle strength in patients with knee OA. It is unclear whether this is due to the accumulation of vastus medialis intramuscular fat or other potential factors, such as diet and physical inactivity.

Automatic detection of passing and shooting in water polo using machine learning: a feasibility study.

There is currently no efficient way to quantify overhead throwing volume in water polo. Therefore, this study aimed to test the feasibility of a method to detect passes and shots in water polo automatically using inertial measurement units (IMU) and machine-learning algorithms. Eight water polo players wore one IMU sensor on the wrist (dominant hand) and one on the sacrum during six practices each. Sessions were filmed with a video camera and manually tagged for individual shots or passes. Data were synchronised between video tagging and IMU sensors using a cross-correlation approach. Support vector machine (SVM) and artificial neural networks (ANN) were compared based on sensitivity and specificity for identifying shots and passes. A total of 7294 actions were identified during the training sessions, including 945 shots and 5361 passes. Using SVM, passes and shots together were identified with 94.4% (95%CI = 91.8-96.4) sensitivity and 93.6% (95%CI = 91.4-95.4) specificity. Using ANN yielded similar sensitivity (93.0% [95%CI = 90.1-95.1]) and specificity (93.4% [95%CI = 91.1 = 95.2]). The results suggest that this method of identifying overhead throwing motions with IMU has potential for future field applications. A set-up with one single sensor at the wrist can suffice to measure these activities in water polo.

Exploring indicators of extremity pain of spinal source as identified by Mechanical Diagnosis and Therapy (MDT): a secondary analysis of a prospective cohort study.

OBJECTIVE: To explore indicators that predict whether patients with extremity pain have a spinal or extremity source of pain. METHODS: The data were from a prospective cohort study (n = 369). Potential indicators were gathered from a typical Mechanical Diagnosis and Therapy (MDT) history and examination. A stepwise logistic regression with a backward elimination was performed to determine which indicators predict classification into spinal or extremity source groups. A Receiver Operating Characteristic (ROC) curve was constructed to examine the number of significant indicators that could predict group classification. RESULTS: Five indicators were identified to predict group classification. Classification into the spinal group was associated with the presence of paresthesia [odds ratio (OR) 1.984], change in symptoms with sitting/neck or trunk flexion/turning neck/when still (OR 2.642), change in symptoms with posture change (OR 3.956), restrictions in spinal movements (OR 2.633), and no restrictions in extremity movements (OR 2.241). The optimal number of indicators for classification was two (sensitivity = 0.638, specificity = 0.807). DISCUSSION: This study provides guidance on clinical indicators that predict the source of symptoms for isolated extremity pain. The clinical indicators will allow clinicians to supplement their decision-making process in regard to spinal and extremity differentiation so as to appropriately target their examinations and interventions.

Inter-segmental coordination amplitude and variability differences during gait in patients with Ehlers-Danlos syndrome and healthy adults.

BACKGROUND: There is limited research examining gait and inter-segmental coordination in patients with Ehlers-Danlos syndrome. The objective was to compare lower extremity inter-segmental coordination amplitude and variability during gait between patients with Ehlers-Danlos syndrome and healthy adults. METHODS: This cross-sectional study included participants with Ehlers-Danlos syndrome (n = 13) and healthy adults (n = 14). Gait data were acquired using a motion capture system and force plates. Participants ambulated at self-selected speeds for five trials. Inter-segmental coordination was quantified using continuous relative phase, which examined the dynamic interaction between the thigh-shank and shank-foot paired segments (i.e. phase space relation). A 2-way mixed analysis of variance examined the effects of groups (Ehlers-Danlos and healthy) and gait phases (stance and swing phase) on inter-segmental coordination amplitude and between-trial variability. Effect sizes were calculated using Cohen's d. FINDINGS: The Ehlers-Danlos group had greater inter-segmental coordination variability compared to the healthy group for foot-shank and shank-thigh segment pairs in the sagittal plane over stance and swing phases (P = 0.04; small to large effect sizes). The Ehlers-Danlos group also had greater variability in the frontal plane at the foot-shank segment pair during stance phase (P = 0.03; large effect). There were no differences in inter-segmental coordination amplitude between groups (P = 0.06 to 0.85). INTERPRETATION: Patients with Ehlers-Danlos syndrome have more variability between gait trials in lower limb motor coordination than healthy adults. This may be related to the impaired proprioception, reduced strength, pain, or slower gait speed seen in this population.

The relationship between knee loading during gait and cartilage thickness in nontraumatic and posttraumatic knee osteoarthritis.

The relationship between knee moments and markers of knee osteoarthritis progression has not been examined in different knee osteoarthritis subtypes. The objective was to examine relationships between external knee moments during gait and tibiofemoral cartilage thickness in patients with nontraumatic and posttraumatic knee osteoarthritis. For this cross-sectional study, participants with knee osteoarthritis were classified into two groups: nontraumatic (n = 22; mean age 60 years) and posttraumatic (n = 19; mean age 56 years, history of anterior cruciate ligament rupture). Gait data were collected with a three-dimensional motion capture system sampled at 100 Hz and force plates sampled at 2000 Hz. External knee moments were calculated using inverse dynamics. Cartilage thickness was determined with magnetic resonance imaging (T1-weighted, 3D sagittal gradient-echo sequence). Linear regression analyses examined relationships between cartilage thickness with knee moments, group, and their interaction. A higher knee adduction moment impulse was negatively associated with medial to lateral cartilage thickness ratio (B = -1.97). This relationship differed between participants in the nontraumatic osteoarthritis group (r = -0.56) and posttraumatic osteoarthritis group (r = -0.30). A higher late stance knee extension moment was associated with greater medial femoral condyle cartilage thickness (B = -0.86) and medial to lateral cartilage thickness (B = -0.73). These relationships also differed between participants in the nontraumatic osteoarthritis group (r = -0.61 and r = -0.51, respectively) and posttraumatic osteoarthritis group (r = 0.10 and r = 0.25, respectively). Clinical Significance: The relationship between knee moments with tibiofemoral cartilage thickness differs between patients with nontraumatic and posttraumatic knee osteoarthritis. The potential influence of mechanical knee loading on articular cartilage may also differ between these subtypes.

Self-reported physical activity is related to knee muscle strength on the unaffected side and walking ability in patients with knee osteoarthritis awaiting total knee arthroplasty: a cross-sectional study.

Background: Additional evidence regarding the effectiveness of self-management programs for patients awaiting total knee arthroplasty is required.Objective: The study aimed to determine if self-reported physical activity was related to muscle strength and walking ability in patients with knee osteoarthritis awaiting total knee arthroplasty.Methods: The study included subjects with knee osteoarthritis awaiting total knee arthroplasty (n = 767). Walking ability and bilateral knee muscle strength were measured as dependent variables. Self-report physical activity was assessed based on the guidelines from the Japanese Ministry of Health, Labor and Welfare. Multiple regression models determined if self-reported physical activity was significantly related to dependent variables, after accounting for other related factors.Results: Physical activity was associated with both higher knee flexion (ß = -0.09, p = .013) and higher extension (ß = -0.09, p = .007) muscle strength on the unaffected side only. In addition, physical inactivity was associated with a lower walking ability level (TUG: ß = 0.08, p = .015; 5mWT: ß = 0.10, p = .005).Conclusions: These results can help health-services providers develop educational and/or self-management programs to maintain muscle strength on the unaffected side and walking ability in patients awaiting total knee arthroplasty.

The Relationship Between Pain-Related Threat and Motor Behavior in Nonspecific Low Back Pain: A Systematic Review and Meta-Analysis.

OBJECTIVE: Although pain-related fear and catastrophizing are predictors of disability in low back pain (LBP), their relationship with guarded motor behavior is unclear. The aim of this meta-analysis was to determine the relationship between pain-related threat (via pain-related fear and catastrophizing) and motor behavior during functional tasks in adults with LBP. METHODS: This review followed PRISMA guidelines. MEDLINE, Embase, PsychINFO, and CINAHL databases were searched to April 2021. Included studies measured the association between pain-related fear or pain catastrophizing and motor behavior (spinal range of motion, trunk coordination and variability, muscle activity) during movement in adults with nonspecific LBP. Studies were excluded if participants were postsurgery or diagnosed with specific LBP. Two independent reviewers extracted all data. The Newcastle-Ottawa Scale was used to assess for risk of bias. Correlation coefficients were pooled using the random-effects model. RESULTS: Reduced spinal range of motion during flexion tasks was weakly related to pain-related fear (15 studies, r = -0.21, 95% CI = -0.31 to -0.11) and pain catastrophizing (7 studies, r = -0.24, 95% CI = -0.38 to -0.087). Pain-related fear was unrelated to spinal extension (3 studies, r = -0.16, 95% CI = -0.33 to 0.026). Greater trunk extensor muscle activity during bending was moderately related to pain-related fear (2 studies, r = -0.40, 95% CI = -0.55 to -0.23). Pain catastrophizing, but not fear, was related to higher trunk activity during gait (2 studies, r = 0.25, 95% CI = 0.063 to 0.42). Methodological differences and missing data limited robust syntheses of studies examining muscle activity, so these findings should be interpreted carefully. CONCLUSION: This study found a weak to moderate relationship between pain-related threat and guarded motor behavior during flexion-based tasks, but not consistently during other movements. IMPACT: These findings provide a jumping-off point for future clinical research to explore the advantages of integrated treatment strategies that target both psychological and motor behavior processes compared with traditional approaches.

Prevalence and mechanisms of injuries in water polo: a systematic review.

OBJECTIVE: To summarise the information available in the literature on the prevalence of injuries in water polo and injury risk factors. METHODS: Protocol was registered on Open Science Framework. MEDLINE, CINAHL, Embase and SPORTDiscus databases were searched for keywords relating to water polo and injuries on 3 February 2021. References were searched for additional studies. Only original research papers in English or French were included, and studies without an injured group were excluded. A data extraction file was made based on the Cochrane Collaboration recommendations. Study quality was evaluated with the Newcastle-Ottawa scales for cohorts and a modified version for cross-sectional studies. RESULTS: The initial search yielded 581 articles, with 5 more added from reference lists, but only 41 remained after removing duplicates and applying inclusion/exclusion criteria. Thirty-one articles identified the head, fingers and shoulders as the most common sites of injury. Ten articles on mechanism of injury focused mainly on the shoulder, with degenerative changes, posture, scapular alignment, strength, flexibility and overhead shooting kinematics as the main injury risk factors. Publication types included cohort studies, cross-sectional studies, and one case series. CONCLUSIONS: Most traumatic injuries affect the hands and the head from unexpected contact with the ball or opponents. Conversely, training injuries seem to affect mainly the shoulder area. Low level evidence suggests a correlation between shoulder injuries and lack of strength or flexibility as well as large volumes of overhead throwing. Further prospective research is needed to investigate risk factors for other body areas.

Hand-Held Shoulder Strength Measures Correlate With Isokinetic Dynamometry in Elite Water Polo Players.

CONTEXT: Previous authors suggest that lack of strength is an important risk factor for injuries in water polo. Hand-held dynamometers have potential as a clinical tool to measure strength, but they have not been validated in water polo players. OBJECTIVE: The purpose of this study was to estimate intertrial variability and concurrent validity of hand-held dynamometer shoulder strength measurements in elite water polo players. METHODS: A total of 19 male and 20 female elite water polo players performed isometric external (ER) and internal (IR) rotation strength tests against a hand-held dynamometer bilaterally in supine position with the shoulder in a 90-90 position. In addition, concentric IR and ER was captured at 90 deg/s with an isokinetic dynamometer, and torque values were determined near the 90-90 position. MAIN OUTCOME MEASURES: Spearman correlation coefficients were calculated for ER torque, IR torque, and ER/IR ratios between the devices. Two-way mixed-model intraclass correlations were used to assess intertrial variability. RESULTS: Correlations between the devices were strong to very strong (ρ = .65-.82, P < .01) for absolute IR and ER but low for ER/IR ratios (ρ = .29, P = .07). There was less agreement at higher torque values. Intertrial variability was low with intraclass correlation values .88 to .93, P < .05. CONCLUSIONS: These results show that hand-held dynamometers are adequate clinical alternatives to measure absolute shoulder strength in water polo players. Stronger players may require stronger evaluators to resist the player's push and obtain reliable results.

Inter-rater Reliability of the McKenzie Method of Mechanical Diagnosis and Therapy for the Provisional Classification of Low Back Pain in Adolescents and Young Adults.

OBJECTIVE: To investigate the inter-rater reliability of Mechanical Diagnosis and Therapy (MDT)-trained Diplomats in classifying adolescents and young adults with lumbar pain. METHODS: Forty-three participants (mean age 15 ± 2 years) with lumbar pain, with or without lower extremity symptoms, were assessed simultaneously by three MDT Diploma holders and classified into one of three groups: 1) Derangement, 2) Dysfunction, 3) Postural/OTHER. Inter-rater reliability was calculated using the Fleiss kappa statistics with 95% confidence intervals (CI). Analyses were repeated with the younger (11 to 15 years old) and older (16 to 21 years old) age groups. RESULTS: There was moderate reliability (Fleiss kappa = 0.50, 95% CI = 0.45 to 0.54) for the entire sample, which was statistically significant (p < 0.001). There was good reliability in older participants (Fleiss kappa = 0.63, 95% CI = 0.57 to 0.70), but poor reliability in younger participants (Fleiss kappa = 0.33, 95% CI = 0.27 to 0.39). There was 100% agreement in classifications among assessors for 70% of participants. DISCUSSION: The MDT system has moderate reliability when classifying lumbar pain in adolescents and young adults. Future reliability studies may include a balanced group for classifications or a second session.

Principal component analysis identifies differences in ice hockey skating stride between high- and low-calibre players.

The objective was to compare joint angles during full stride skating on ice between high- and low-calibre hockey players. High (n = 8) and low (n = 8) calibre male participants completed full stride skating on ice for two to five trials. A 10-camera motion capture system collected kinematic data. Ankle, knee, and hip angles were calculated. Principal component analysis (PCA) identified important angle characteristics and each trial was scored against principal components (PC-scores). Hierarchical linear models examined relationships between PC-scores and skill level with and without controlling for speed. High-calibre participants were associated with greater ankle inversion during push-off and recovery (p < 0.001), greater knee extension (p = 0.051) and external rotation at push-off (p = 0.038), and greater hip flexion throughout stride (p = 0.027) after controlling for speed. Interactions existed between speed and skill level including faster skating speeds were associated with increased plantarflexion at push-off in low-calibre participants while there was no relationship in high-calibre participants. Skating pattern differences between skill levels provide an indication of ideal joint motion during skating. Players should be encouraged to plantarflex the ankle during push-off, extend and externally rotate the knee during push-off, and increase hip flexion throughout stride.

The Influence of Time of Season on Injury Rates and the Epidemiology of Canadian Football Injuries.

OBJECTIVE: To describe injury rates and injury patterns in the Canadian Football League (CFL) according to time during the season, player position, injury type, and injury location. DESIGN: Prospective, cohort study. SETTING AND PARTICIPANTS: Eight seasons from CFL injury surveillance database. INDEPENDENT VARIABLES: Depending on the analysis, time of season (preseason, regular, and playoffs), player position, injury type, and injury location. MAIN OUTCOME MEASURES: Medical attention and time-loss injury rates per 100 athletes at risk (AAR), and prevalence of time-loss injuries per week. RESULTS: The average game injury rate was 45.2/100 AAR medical attention injuries and 30.7/100 AAR time-loss injuries. Injury rates declined by 1% per week over the season for both medical attention (rate ratio = 0.99) and time-loss (rate ratio = 0.99) injuries, with a substantial decline during the playoffs compared with preseason (rate ratio = 0.70-0.77). The number of ongoing time-loss injuries increased over the course of the regular season. Quarterbacks, offensive backs, and linebackers had the highest game injury rates. Joint/ligament and muscle/tendon injuries were the most common injury types for games and practices, respectively. The lower extremity was the most commonly affected area, specifically the lower leg/ankle/foot and hip/groin/thigh. CONCLUSIONS: There was a 1% decline in injury rate per week during the season and a 30% decline during the playoffs. The number of ongoing time-loss injuries increased over the regular season. Current results can aid league officials and medical staff in making evidence-based decisions concerning player safety and health.

The relationship between trunk rotation and shot speed when performing ice hockey wrist shots.

There has been minimal work examining kinematics of ice hockey wrist shots. The objective was to determine if puck and blade speed were related to trunk rotation during wrist shots in elite and recreational players. Elite (n = 10) and recreational (n = 10) ice hockey players completed wrist shots while skating and from a stationary position on real ice. A 14 camera motion capture system collected kinematic data for the trunk, pelvis, stick, and puck. Dependent variables included peak puck and blade speeds. Independent variables included peak trunk rotation angles, trunk rotation range of motion (ROM), and group (elite vs. recreational). Hierarchical linear models compared relationships between dependent and independent variables for both skating and stationary wrist shots. Greater peak trunk rotation away from the net was related (p < 0.05) to faster puck and blade speeds for skating and stationary wrist shots. This relationship was stronger in the recreational group for skating wrist shots (p < 0.01). Greater trunk rotation ROM was related (p = 0.01) to faster puck and blade speeds for the skating wrist shots only. Coaches should encourage players to increase trunk rotation away from the net during wrist shots, especially in recreational players.

The Influence of Lateral and Posterior Total Hip Arthroplasty Approaches on Muscle Activation and Joint Mechanics During Gait.

BACKGROUND: Lateral and posterior total hip arthroplasty (THA) approaches disrupt muscle function, which could impact gait. The objectives of this study were to compare muscle activation and joint mechanics during gait, and isometric strength between participants after lateral and posterior THA approaches and healthy adults. METHODS: Participants 1 year post-THA from either lateral (n = 21) or posterior (n = 21) approaches, and healthy adults (n = 21) ambulated at self-selected speeds. Surface electromyography, optical motion capture, and force plates measured muscle activation and joint mechanics during gait. A dynamometer measured isometric torque. Gait characteristics and isometric torque were compared using analysis of variance and effect sizes (d). RESULTS: Lateral THA group had higher gluteus medius amplitudes during gait compared to the healthy group (P < .01, d = -0.97). Posterior THA group had higher gluteus maximus amplitudes during loading response (P = .02, d = -0.94) and higher hamstring amplitudes during midstance (P = .02, d = 0.45-1.31) than the healthy group. Both THA groups had decreased hip flexion and adduction angle excursions during gait (d = 0.89-1.14), but increased medial rotation angle excursions (d = -1.06 to -0.91), compared to the healthy group. Lateral THA group had lower isometric hip abduction torque than the healthy group (P = .03, d = 0.74). There was no pelvic drop in the THA groups. CONCLUSION: There were few differences in gait and isometric torque between lateral and posterior THA groups. The elevated muscle activation amplitudes in the lateral and posterior THA groups compared to healthy adults were likely due to muscle weakness. Despite these findings, there was no evidence of pelvic drop.