Running Habits and Injury Frequency Following COVID-19 Restrictions in Adolescent Long-Distance Runners.

PURPOSE: A decline in youth running was observed at the start of the COVID-19 pandemic. We investigated whether the resumption of organized running after social distancing restrictions changed running habits or injury frequency in adolescent runners. METHODS: Adolescents (age = 16.1 [2.1] y) who participated in long-distance running activities completed an online survey in the Spring and Fall of 2020. Participants self-reported average weekly running habits and whether they sustained an injury during the Fall 2020 season. Poisson regression models and 1-way analysis of variance compared running habits while Fisher exact test compared differences in frequencies of injuries during Fall 2020 among season statuses (full, delayed, and canceled). RESULTS: All runners, regardless of season status, increased weekly distance during Fall 2020. Only runners with a full Fall 2020 season ran more times per week and more high-intensity runs per week compared with their Spring 2020 running habits. There were no differences in running volume or running-related injury frequency among Fall 2020 season statuses. CONCLUSIONS: There were no significant differences in running-related injury (RRI) frequency among runners, regardless of season status, following the resumption of cross-country. Health care providers may need to prepare for runners to increase running volume and intensity following the resumption of organized team activities.

Pre-pubertal runners demonstrate greater variability in running kinematics than post-pubertal runners.

BACKGROUND: Adolescents undergo a period of motor incoordination during puberty characterized by high movement variability. It is unknown if differences in running kinematics variability exist among adolescent long-distance runners. RESEARCH QUESTION: Is kinematic variability different among male and female adolescent long-distance runners of different stages of physical maturation? METHODS: We enrolled 114 adolescent long-distance runners (ages 8-19, F = 55, M = 59) in this secondary analysis of a larger cross-sectional study. Participants completed a three-dimensional overground running analysis at a comfortable self-selected speed. Peak frontal, sagittal, and transverse plane hip, knee, and ankle/shoe joint angles from the right leg were identified during stance phase for at least five trials. Variability in running kinematics was quantified as the standard deviation of the peak joint angles among the running trials for each participant. Participants were stratified by sex and stage of physical maturation (pre-, mid-, post-pubertal) and two-way ANOVAs compared between-subjects variability among groups (p ≤ .05). RESULTS: Significant sex by maturation interactions were observed for hip external rotation and ankle external rotation variability. Sex differences were observed for hip internal rotation, with males demonstrating greater variability, and ankle internal rotation, with females demonstrating greater variability. Pre-pubertal runners demonstrated significantly greater variability than mid-pubertal runners for hip flexion, and greater variability than post-pubertal runners for hip flexion, hip adduction, hip internal rotation, and knee flexion. SIGNIFICANCE: Pre-pubertal adolescent long-distance runners demonstrate greater stance phase variability in running kinematics than post-pubertal adolescent long-distance runners, while adolescent males and females demonstrate similar variability. Anthropometric and neuromuscular changes that occur during puberty likely influence running patterns and may contribute to more consistent kinematic patterns for post-pubertal runners.

Can Clinicians Trust Objective Measures of Hip Muscle Strength From Portable Dynamometers? A Systematic Review With Meta-analysis and Evidence Gap Map of 107 Studies of Reliability and Criterion Validity Using the COSMIN Methodology.

OBJECTIVE: To summarize the evidence on reliability and criterion validity of hip muscle strength testing using portable dynamometers. DESIGN: Systematic review with meta-analysis. LITERATURE SEARCH: Five databases were searched from inception to March 2023. STUDY SELECTION CRITERIA: We included studies investigating reliability or criterion validity of hip flexor, extensor, abductor, adductor, or internal/external rotator strength testing with portable dynamometers in injury-free individuals or those with pelvic/lower limb musculoskeletal disorders. DATA SYNTHESIS: We performed meta-analyses for each muscle group, position, and method of fixation. We rated pooled results as sufficient (>75% of studies with correlations ≥0.70), insufficient (>75% of studies with correlations <0.70), or inconsistent (sufficient/insufficient results). We assessed the quality of evidence, created evidence gap maps, and made clinical recommendations. RESULTS: We included a total of 107 studies (reliability 103, validity 14). The intrarater and interrater reliability for hip muscle strength testing across different positions and methods of fixation was sufficient (intraclass correlation coefficient = 0.78-0.96) with low- to high-quality evidence. Criterion validity was less investigated and mostly inconsistent (very low-to moderate-quality evidence) with a wide range of correlations (r = 0.40-0.93). CONCLUSION: Hip muscle strength testing using portable dynamometers is reliable. The use of portable dynamometers as clinical surrogates for measuring strength using an isokinetic dynamometer requires further investigation. Clinicians testing hip muscle strength with portable dynamometers should use external fixation seated for hip flexors, prone or supine for hip extensors, side-lying or supine for abductors and adductors, and prone and seated for internal and external rotators. J Orthop Sports Phys Ther 2023;53(11):655-672. Epub 3 October 2023. doi:10.2519/jospt.2023.12045.

Preferred temporal-spatial parameters, physical maturation, and sex are related to vertical and braking forces in adolescent long-distance runners.

For adults, increasing cadence reduces ground reaction forces, but a lower preferred cadence does not predispose adults to experience higher ground reaction forces. Pubertal growth and motor control changes influence running mechanics, but it is unknown if preferred cadence or step length are associated with ground reaction forces for pre-adolescent and adolescent runners. Pre-adolescent and adolescent runners underwent an overground running analysis at a self-selected speed. Mixed model multiple linear regressions investigated the associations of preferred cadence, step length, physical maturation, and sex on ground reaction forces, while accounting for running speed and leg length. Running with a lower preferred cadence or longer preferred step length was associated with larger peak braking and vertical forces (p ≤ .01), being less physically mature was associated with larger vertical impact peak force and vertical loading rate (p ≤ .01), and being a male was associated with larger loading rates (p ≤ .01). A lower preferred cadence or longer preferred step length were associated with higher braking and vertical forces and being less physically mature or a male were associated with higher loading rates. An intervention to increase cadence/decrease step length could be considered if ground reaction forces are a concern for an adolescent runner.

One size does not fit all: Influence of sex and maturation on temporal-spatial parameters for adolescent long-distance runners.

Runners and coaches are often interested in identifying the "ideal" running form to reduce the risk of injury and improve performance. While differences in pelvis and hip motion have been reported among adolescent female and male long-distance runners of different stages of physical maturation, the influence of sex and/or maturation on temporal-spatial parameters is unknown for adolescent runners. Adolescent runners of different stages of physical maturation (pre-, mid-, post-pubertal) completed an overground running analysis at a self-selected speed. We performed 2 × 3 ANCOVAs (covariate = running speed) to compare temporal-spatial parameters among sex and maturation groups. Pre-adolescents ran with higher cadences and shorter step lengths than mid- (p ≤ .01) and post-pubertal adolescents (p ≤ .01), respectively. Mid-pubertal males and post-pubertal females also ran with higher cadences and shorter step lengths than post-pubertal males (p ≤ .01). When step length was normalized to leg length, less physically mature runners demonstrated longer normalized step lengths (p ≤ .01). Caution is advised when using a "one-size-fits-all" approach for recommending an "ideal" cadence and/or step length for adolescent long-distance runners. A runner's sex, stage of physical maturation and leg length should be considered when assessing and prescribing cadence and/or step length.

Cadence in youth long-distance runners is predicted by leg length and running speed.

BACKGROUND: Lower cadence has been previously associated with injury in long-distance runners. Variations in cadence may be related to experience, speed, and anthropometric variables. It is unknown what factors, if any, predict cadence in healthy youth long-distance runners. RESEARCH QUESTION: Are demographic, anthropometric and/or biomechanical variables able to predict cadence in healthy youth long-distance runners. METHODS: A cohort of 138 uninjured youth long-distance runners (M = 62, F = 76; Mean ± SD; age = 13.7 ± 2.7; mass = 47.9 ± 13.6 kg; height = 157.9 ± 14.5 cm; running volume = 19.2 ± 20.6 km/wk; running experience: males = 3.5 ± 2.1 yrs, females = 3.3 ± 2.0 yrs) were recruited for the study. Multiple linear regression (MLR) models were developed for total sample and for each sex independently that only included variables that were significantly correlated to self-selected cadence. A variance inflation factor (VIF) assessed multicollinearity of variables. If VIF≥ 5, variable(s) were removed and the MLR analysis was conducted again. RESULTS: For all models, VIF was > 5 between speed and normalized stride length, therefore we removed normalized stride length from all models. Only leg length and speed were significantly correlated (p < .001) with cadence in the regression models for total sample (R2 = 51.9 %) and females (R2 = 48.2 %). The regression model for all participants was Cadence = -1.251 *Leg Length + 3.665 *Speed + 254.858. The regression model for females was Cadence = -1.190 *Leg Length + 3.705 *Speed + 249.688. For males, leg length, cadence, and running experience were significantly predictive (p < .001) of cadence in the model (R2 = 54.7 %). The regression model for males was Cadence = -1.268 *Leg Length + 3.471 *Speed - 1.087 *Running Experience + 261.378. SIGNIFICANCE: Approximately 50 % of the variance in cadence was explained by the individual's leg length and running speed. Shorter leg lengths and faster running speeds were associated with higher cadence. For males, fewer years of running experience was associated with a higher cadence.

Brachial plexus birth injury and cerebral palsy lead to a common contracture phenotype characterized by reduced functional muscle length and strength.

Introduction: Brachial plexus birth injury (BPBI) and cerebral palsy (CP) both cause disabling contractures for which no curative treatments exist, largely because contracture pathophysiology is incompletely understood. The distinct neurologic nature of BPBI and CP suggest different potential contracture etiologies, although imbalanced muscle strength and insufficient muscle length have been variably implicated. The current study directly compares the muscle phenotype of elbow flexion contractures in human subjects with BPBI and CP to test the hypothesis that both conditions cause contractures characterized by a deficit in muscle length rather than an excess in muscle strength. Methods: Subjects over 6 years of age with unilateral BPBI or hemiplegic CP, and with elbow flexion contractures greater than 10 degrees on the affected side, underwent bilateral elbow flexion isokinetic strength testing to identify peak torque and impulse, or area under the torque-angle curve. Subjects then underwent needle microendoscopic sarcomere length measurement of bilateral biceps brachii muscles at symmetric joint angles. Results: In five subjects with unilateral BPBI and five with hemiplegic CP, peak torque and impulse were significantly lower on the affected versus unaffected sides, with no differences between BPBI and CP subjects in the percent reduction of either strength measurement. In both BPBI and CP, the percent reduction of impulse was significantly greater than that of peak torque, consistent with functionally shorter muscles. Similarly, in both conditions, affected muscles had significantly longer sarcomeres than unaffected muscles at symmetric joint angles, indicating fewer sarcomeres in series, with no differences between BPBI and CP subjects in relative sarcomere overstretch. Discussion: The current study reveals a common phenotype of muscle contracture in BPBI and CP, with contractures in both conditions characterized by a similar deficit in muscle length rather than an excess in muscle strength. These findings support contracture treatments that lengthen rather than weaken affected muscles. Moreover, the discovery of a common contracture phenotype between CP and BPBI challenges the presumed dichotomy between upper and lower motor neuron lesions in contracture pathogenesis, instead revealing the broader concept of "myobrevopathy", or disorder of short muscle, warranting increased investigation into the poorly understood mechanisms regulating muscle length.

Validity of an artificial intelligence, human pose estimation model for measuring single-leg squat kinematics.

Few studies have investigated the validity of 2D pose estimation models to evaluate kinematics throughout a motion and none have included adolescents. Adolescent athletes completed single-leg squats while 3D kinematic data and 2D sagittal and frontal plane videos were recorded. Sagittal and frontal plane joint motion throughout the single-leg squats and angles at peak knee flexion were compared among 2D pose estimation, 3D motion analysis, and traditional 2D motion analysis techniques. Statistical parametric mapping compared waveforms while Pearson's correlation compared the relationships of joint angles at peak knee flexion among techniques, respectively. We observed significant waveform differences between 2D pose estimation and 3D motion analysis at the beginning and end of the squat for sagittal plane hip and knee motion, for most of the squat for frontal plane hip motion, and throughout the entire squat for sagittal plane ankle motion and frontal plane pelvic motion. We observed moderate-to-strong relationships (r = 0.68-0.94) for sagittal plane joint angles between 2D pose estimation and 3D techniques. We observed fair correlations (r = 0.53-0.54) for frontal plane pelvic and hip joint angles between 2D pose estimation and 3D motion analysis. We observed poor relationships for the frontal plane knee angle between 3D motion analysis with 2D pose estimation (r = 0.20) and traditional 2D motion analysis (r = 0.05), respectively, but observed a strong relationship (r = 0.95) between the 2D techniques. 2D pose estimation is a valid alternative to 3D motion analysis and traditional 2D motion analysis for evaluating most sagittal and frontal plane angles during a single-leg squatting task.

Global Positioning System Watches and Electronic Journals: Are Training-Load Measures Similar in High School Cross-Country Runners?

PURPOSE: Running programs are designed to progress training loads by manipulating the duration, frequency, and/or intensity of running sessions. While some studies use journals to monitor training load, others have used wearable technology. The purpose of this study was to compare the validity of self-reported and global positioning system (GPS)-watch-derived measures of external and internal loads in high school cross-country runners. METHODS: Twenty-two high school cross-country runners participated in the study during fall 2020. Participants recorded running sessions using a GPS watch and self-reported the running session using an electronic journal. External (distance and duration) and internal loads (session rating of perceived exertion [sRPE], average, and maximum heart rate) were retrieved from the GPS watch and electronic journal. Correlations compared relationships, and Bland-Altman plots compared agreements between GPS-watch-derived and self-reported measures of training loads. RESULTS: We found moderate relationships between self-reported and GPS-watch-derived measures of external loads (distance: r = .76, moving duration: r = .74, and elapsed duration: r = .70) and poor relationships between internal loads (sRPE vs average heart rate: ρ = .11, sRPE vs maximal heart rate: ρ = .13). We found mean differences of -0.8 km (95% = -6.3 to +4.8 km) for distance, -4.5 minutes (95% = -27.8 to +33.2 min) for moving duration, and 2.7 minutes (95% = -27.8 min to +33.2 min) for elapsed duration. CONCLUSIONS: High school runners overreported running distance and duration using self-reports, and self-reported and GPS-watch-derived measures of internal loads demonstrated poor agreement. Coaches and clinicians should use caution when comparing results from studies using different methods of monitoring training loads.

Influence of hamstring flexibility on running kinematics in adolescent long-distance runners.

BACKGROUND: Studies have found no or minimal differences in running kinematics between flexible and inflexible adult runners. The interaction between hamstring flexibility and running kinematics has not been reported in adolescent long-distance runners. RESEARCH QUESTION: Does hamstring flexibility influence running kinematics in adolescent long-distance runners? METHODS: Adolescent long-distance runners (n = 140, ages 9-19) were enrolled in our cross-sectional study. Hamstring flexibility was assessed with the forward bending Beighton task. Runners were categorized if they tested positive or negative on the forward bending task. Participants ran at a comfortable self-selected speed on a treadmill. Runners who tested positive on the forward bending task (n = 17) were matched with runners who tested negative on the task (n = 17) according to sex, physical maturation, and running speed. Statistical parametric mapping compared trunk, pelvis, hip, and knee kinematic waveforms throughout the gait cycle and independent sample t tests compared temporal-spatial parameters between the groups. RESULTS: Runners who tested positive on the forward bending task demonstrated significantly greater anterior pelvic tilt during stance (average difference = 4.8° ± 0.4°, p < .001) and swing (average difference = 4.3° ± 0.2°, p < .01) compared to runners who tested negative on the forward bending task. No significant differences were found between groups for the remaining kinematic waveforms or for any temporal-spatial parameters (p > .05). SIGNIFICANCE: This is the first study to report the interaction between hamstring flexibility and running kinematics in adolescent long-distance runners. The greater anterior pelvic tilt demonstrated by runners with greater hamstring flexibility may place more eccentric demands on the hamstring musculature. However, as there were no other differences in joint kinematics or temporal-spatial parameters between groups, greater hamstring flexibility does not appear to have a significant interaction with running kinematics when running at sub-maximal speeds. Our results suggest hamstring flexibility does not predispose adolescent long-distance runners to sub-optimal segment positions associated with running-related injuries.

Acute changes in sagittal plane kinematics while wearing a novel belt device during treadmill running.

Somatosensory feedback is used in walking retraining; however, its utility in running is less feasible due to the greater associated speeds. The purpose of this study was to examine the acute effects of wearing a novel running belt device on sagittal plane running kinematics. Ten healthy runners ran on a treadmill with and without the use of a running belt device within a repeated measures study design. Temporal-spatial characteristics and sagittal plane knee and ankle kinematics were recorded with three-dimensional motion analysis. Wilcoxon Signed-Rank Tests revealed significant decreases in centre of mass vertical displacement (z = -2.083, p = 0.003), tibial inclination at initial contact (z = -2.803, p = 0.003), and stance phase knee joint excursion (z = -2.701, p = 0.003), and greater knee flexion at initial contact (z = -2.803, p = 0.003) when the belt was donned. No differences were observed in step rate (z = -0.351, p = 0.363), foot inclination angle at initial contact (z = -2.090, p = 0.018), or peak knee flexion during stance (z = -1.172, p = 0.121). Findings suggest that donning a running belt can minimise specific high-risk biomechanical characteristics in runners with particular kinematic profiles.

The influence of maturation and sex on pelvis and hip kinematics in youth distance runners.

OBJECTIVES: This study aimed to investigate differences in stance phase pelvic and hip running kinematics based on maturation and sex among healthy youth distance runners. DESIGN: Cross-Sectional. METHODS: 133 uninjured youth distance runners (M = 60, F = 73; age = 13.5 ±â€¯2.7 years) underwent a three-dimensional running analysis on a treadmill at a self-selected speed (2.8 ±â€¯0.6 m·s-1). Participants were stratified as pre-pubertal, mid-pubertal, or post-pubertal according to the modified Pubertal Maturational Observation Scale. Stance phase pelvis and hip range of motion (RoM) and peak joint positions were extracted. Two-way ANCOVAs (sex, maturation; covariate of running velocity) were used with Bonferroni-Holm method to control for multiple comparisons with a target alpha level of 0.05. RESULTS: A two-way interaction between sex and maturation was detected (p = 0.009) for frontal plane pelvic obliquity RoM. Post-hoc analysis identified a maturation main effect only among females (p˂0.008). Pelvic obliquity RoM was significantly greater among post-pubertal (p = 0.001) compared to pre-pubertal females. Significant main effects of sex (p = 0.02), and maturation (p = 0.01) were found for hip adduction RoM. Post-hoc analysis indicated a significant increase in hip adduction RoM from pre-pubertal to post-pubertal female runners (p = 0.001). A significant main effect of sex was found for peak hip adduction angle (p = 0.001) with female runners exhibiting greater maximum peak hip adduction compared to males. CONCLUSIONS: Maturation influences pelvic and hip kinematics greater in female than male runners. Sex differences became more pronounced during later stages of puberty. These differences may correspond to an increased risk for running-related injuries in female runners compared to male runners.

Quantification Method and Training Load Changes in High School Cross-Country Runners Across a Competitive Season.

CONTEXT: Running programs traditionally monitor external loads (eg, time and distance). Recent efforts have encouraged a more comprehensive approach to also account for internal loads (eg, intensity, measured as the session rating of perceived exertion [sRPE]). The combination of external and internal loads accounts for the possible interaction between these loads. Although weekly changes in training loads have been reported between external loads and the combination of external and internal loads during 2- and 4-week training cycles, no authors have indicated whether these differences occur during an entire cross-country season in high school runners. OBJECTIVE: To compare changes in training loads, as measured by (1) external loads and (2) combined external and internal loads in high school runners during an interscholastic cross-country season. DESIGN: Case series. SETTING: Community-based setting with daily online surveys. PATIENTS OR OTHER PARTICIPANTS: Twenty-four high school cross-country runners (females = 14, males = 10, age = 15.9 ± 1.1 years, running experience = 9.9 ± 3.2 years). MAIN OUTCOME MEASURE(S): Week-to-week percentage changes in training load were measured by external loads (time, distance) and combined external and internal loads (time × sRPE [timeRPE] and distance × sRPE [distanceRPE]). RESULTS: Overall, the average weekly change was 7.1% greater for distanceRPE than for distance (P = .04, d = 0.18). When the weekly running duration decreased, we found the average weekly change was 5.2% greater for distanceRPE than for timeRPE (P = .03, d = 0.24). When the weekly running duration was maintained or increased, the average weekly change was 10% to 15% greater when external and internal loads were combined versus external loads alone, but these differences were nonsignificant (P = .11-.22, d = 0.19-0.34). CONCLUSIONS: Progression in the training load may be underestimated when relying solely on external loads. The interaction between internal loads (sRPE) and external loads (distance or time) appears to provide a different measure of the training stresses experienced by runners than external loads alone.

Changes in Motivation, Socialization, Wellness and Mental Health in Youth Long-Distance Runners During COVID-19 Social Distancing Restrictions.

Purpose: The COVID-19 pandemic impacted the sporting and exercise activities of millions of youth. Running is an activity that could be maintained while social distancing restrictions were implemented during the pandemic. However, a recent study has indicated that youth runners reported lower running distance, frequency, and intensity during COVID-19. The reason for this reduction and the impact on overall well-being is unknown. Therefore, the purpose of this study was to determine if the social distancing restrictions during the 2020 COVID-19 pandemic influenced running motives, socialization, wellness and mental health in youth long-distance runners. Methods: A customized, open online questionnaire was provided to runners 9-19 years of age who participated in long-distance running activities including team/club cross-country, track and field (distances ≥800 m), road races, or recreational running. Participants responded to questions about demographics, motive for running, and wellness (sleep quality, anxiety, running enjoyment, food consumption quality) 6-months before as well as during social distancing restrictions due to COVID-19. Wilcoxon signed rank tests compared differences for ratio data and Chi-square tests were used to compare proportions before and during COVID-19 social distancing restrictions. Statistical significance was set at p ≤ 0.05. Results: A total of 287 youth long-distance runners (male = 124, female = 162, unspecified = 1; age = 15.3 ± 1.7 years; running experience = 5.0 ± 2.3 years) participated. Compared to their pre-COVID-19 responses, youth long-distance runners reported lower overall motivation to run (p < 0.001) and changes to most motive rankings (p < 0.001 to p = 0.71). The proportion of youth running alone increased during COVID-19 (65.8%) compared to pre-COVID-19 (13.8%, p < 0.001). Youth long-distance runners also reported less running enjoyment (p = 0.001), longer sleep duration (p < 0.001), lower sleep quality (p = 0.05), more anxiety (p = 0.043), and lower food quality consumed (p < 0.001) during COVID-19 social distance restrictions. Conclusion: The COVID-19 social distancing restrictions resulted in significant decreases in motivation and enjoyment of running. The removal of competition and team-based interactions likely had a role in these decreases for this population. Continuing team-based activities (e.g., virtual) during social distancing may help with maintaining motivation of youth long-distance runners. Reduced running occurred concurrently with reduced overall well-being of youth long-distance runners during the COVID-19 pandemic.

Sport Specialization and Quality of Life among Middle- and High-School Long-Distance Runners of Different Injury Status: A Retrospective Study.

Running-related injuries are prevalent in adolescent long-distance runners. The aim of our retrospective study was to compare differences in sport specialization, running habits,quality of life, and sleep habits among middle-and high-school long-distance runners of different injury statuses. Middle- and high-school long-distance runners across the United States were recruited via cross-country coaches and athletic directors between January and May 2020. Participants completed an online survey with questions related to demographics, sport specialization, running habits, quality of life, sleep, and self-reported injury history. Overall, 306 participants completed the survey (male = 107, female = 176, unspecified = 23; age = 15.7 ± 1.1 years). Of the participants, 178 (58.2%) reported no history of injury, 101 (33.0%) reported a previous injury, and 27 (8.8%) reported a current injury. Middle- and high-school runners with a current injury reported significantly lower overall health (p= .01) and average distance per run (p = .05) than uninjured runners. No significant differences were found among injury status and sport specialization level, quality of life, sleep habits, or running volume (p> .05). Runners with a self-reported previous or current injury do not appear to be classified as high-specialized runners more frequently than uninjured runners.

Tibial acceleration and shock attenuation while running over different surfaces in a trail environment.

OBJECTIVES: Increased tibial axial acceleration and reduced shock attenuation are associated with running injuries and are believed to be influenced by surface type. Trail running has increased in popularity and is thought to have softer surface properties than paved surface, but it is unclear if trail surfaces influence tibial acceleration and shock attenuation. The purpose of this study was to investigate peak triaxial and resultant tibial acceleration as well as axial and resultant shock attenuation among dirt, gravel, and paved surfaces. DESIGN: Fifteen recreational runners (12 females, 3 males, age=27.7±9.1 years) ran over dirt, gravel, and paved surfaces in a trail environment while instrumented with triaxial tibial and head accelerometers. METHODS: Differences between tri-planar peak tibial accelerations (braking, propulsion, axial, medial, lateral, and resultant) and shock attenuations (axial and resultant) among surface types were assessed with one-way ANOVAs with Bonferroni post-hoc tests. RESULTS: No significant differences were found for tibial accelerations or shock attenuations among surface types (p>0.05). CONCLUSIONS: Dirt and gravel trail running surfaces do not have lower tibial accelerations or greater shock attenuation than paved surfaces. While runners are encouraged to enjoy the psychological benefits of trail running, trail surfaces do not appear to reduce loading forces associated with running-related injuries.

Sport Specialization in Middle School and High School Long-Distance Runners.

CONTEXT: Previous reports suggested that highly specialized adolescent athletes may be at a higher risk of injury, worse sleep quality, and less sport enjoyment than low-level specialized athletes. To date, the sport specialization literature has primarily addressed adolescent athletes in a variety of sports. However, whether the findings on sport specialization in predominantly nonrunning athletes are generalizable to adolescent long-distance runners is unknown. OBJECTIVE: To compare injury history, running volume, quality of life, sleep habits, and running enjoyment among male and female middle school and high school long-distance runners at different sport specialization levels. DESIGN: Cross-sectional study. SETTING: Online survey. PATIENTS OR OTHER PARTICIPANTS: A total of 102 male (age = 15.8 ± 0.9 years) and 156 female (age = 15.6 ± 1.4 years) uninjured middle school and high school athletes who participated in long-distance running activities (completion rate = 50.7%). MAIN OUTCOME MEASURE(S): Participants were stratified by sex and sport specialization level (low, moderate, or high). Group differences were assessed in self-reported running-related injuries, running habits, EQ-5D-Y quality of life, Pittsburgh Sleep Quality Index sleep quality, sleep duration, and running enjoyment. RESULTS: Highly specialized male and female middle school and high school long-distance runners reported more months of competition per year (P < .001), higher weekly run distance (P < .001), more runs per week (P < .001), higher average distance per run (P < .001), and greater running enjoyment (P < .001) than low-level specialized runners. Adolescent boys reported a higher average weekly run distance (P = .01), higher average distance per run (P = .01), and better sleep quality (P = .01) than adolescent girls. No differences among sport specialization levels were found for running-related injuries (P = .25), quality of life (P = .07), sleep quality (P = .19), or sleep duration (P = .11) among male or female middle school and high school runners. CONCLUSIONS: Highly specialized male and female middle school and high school long-distance runners reported higher running volumes and running enjoyment than low-level specialized runners. However, high-level specialized runners did not describe a greater number of running-related injuries, lower quality of life, or lower sleep quality or duration as expected.

Impact of COVID-19 Social Distancing Restrictions on Training Habits, Injury, and Care Seeking Behavior in Youth Long-Distance Runners.

Purpose: The COVID-19 pandemic impacted the sporting and exercise activities of millions of youth. Running is an activity that could be maintained while social distancing restrictions were implemented during the pandemic. If running-related injuries do occur, these restrictions may also influence the access to care or care seeking behavior of this population. Therefore, the purpose of this study was to determine if the social distancing restrictions during the 2020 COVID-19 pandemic influenced training habits, injury, and care seeking behavior in youth long-distance runners. Methods: A customized, open online questionnaire was provided to runners 9-19 years of age who participated in long-distance running activities including team/club cross-country, track and field (distances ≥800 m), road races, or recreational running. Participants responded to questions about demographics, running habits, RRIs, and health care provider visits 6-months before as well as during social distancing restrictions due to COVID-19. Wilcoxon signed rank tests compared differences for ratio data and Chi-square tests were used to compare proportions before and during COVID-19 social distancing restrictions. Statistical significance was set at p ≤ 0.05. Results: A total of 287 youth long-distance runners (male = 124, female = 162, unspecified = 1; age = 15.3 ± 1.7 years; running experience = 5.0 ± 2.3 years) participated. Compared to their pre-COVID-19 responses, youth long-distance runners reported lower distances run per week (p < 0.001), fewer runs per week (p < 0.001), fewer hard runs per week (p < 0.001), fewer number of injuries (p < 0.001), and fewer injuries per 1,000 km (p = 0.002) during the COVID-19 social distancing restrictions. A lower proportion of participants reported in-person health care provider visits (p < 0.001) and a lower proportion of visits were made to an athletic trainer during COVID-19 social distancing restrictions compared to prior to COVID-19 (p < 0.001). Conclusion: The COVID-19 pandemic resulted in significant decreases in both training and injuries which were different compared to previous reports in an adult population. Many of the runners who sustained an injury during COVID-19 social distancing restrictions did not seek care, with the most prominent reduction in visits to an athletic trainer. This could impact future injury and chronic pain.

Screw Anterior Distal Femoral Hemiepiphysiodesis in Children With Cerebral Palsy and Knee Flexion Contractures: A Retrospective Case-control Study.

BACKGROUND: In children with cerebral palsy who demonstrate hamstring tightness, increasing attention is being paid to less invasive methods of correcting knee flexion contractures. Guided growth principles represent one such approach, and in tandem with a serial extension casting protocol, may provide a less invasive method of addressing these contractures. To date, no evidence is available on this combination of procedures. The purpose of this study was to investigate the effectiveness of a combined lengthening/guided growth procedure (hamstring lengthening, percutaneous anterior screw hemiepiphysiodesis, and serial extension casting) in addressing knee flexion contracture, and to compare this approach to hamstring lengthening and serial extension casting alone. METHODS: Measures from preoperative and postoperative gait analyses were reviewed retrospectively for 10 patients with cerebral palsy who underwent anterior screw hemiepiphysiodesis and hamstring lengthening followed by serial extension casting [anterior epiphysiodesis (AE) group]. These findings were compared with measures from 19 patients with cerebral palsy who underwent hamstring lengthening followed by serial extension casting [no anterior epiphysiodesis (NAE) group]. Postoperative changes in clinical, functional, and kinematic parameters were assessed. Radiographic parameters were also assessed for the AE group. RESULTS: In the AE group, improvements were measured in knee contracture, popliteal angle, peak stance phase knee extension, knee range of motion, and Gait Deviation Index. Similar results were observed in the NAE group. In the AE group, the lateral distal femoral angle increased into extension by 20.9 degrees at an average of 26-month follow-up. Both groups showed an increase in pelvic tilt postoperatively. There were no surgical complications associated with the screw anterior hemiepiphysiodesis. Four patients did have complaints of knee pain, but the pain was attributable to the implants in only one patient. DISCUSSION: The AE group demonstrated statistically greater postoperative improvement in popliteal angle, knee flexion contracture, and peak knee extension during stance than the NAE group. Both procedures led to improvements in clinical and functional measures, indicating the validity of this approach as a means of correcting flexion contracture that is less invasive and allows immediate weight bearing. LEVEL OF EVIDENCE: Level III-therapeutic study.

Improved Clinical and Functional Outcomes in Crouch Gait Following Minimally Invasive Hamstring Lengthening and Serial Casting in Children With Cerebral Palsy.

BACKGROUND: Serial extension casting represents a novel solution for addressing residual knee flexion contractures following hamstring lengthening in children with cerebral palsy. The purpose of this study was to investigate postoperative changes in patients following hamstring lengthening with a serial casting protocol. METHODS: Measures from preoperative and postoperative gait analyses were reviewed retrospectively for 19 patients with cerebral palsy who underwent hamstring lengthening followed by serial extension casting. Postoperative changes in clinical, functional, and kinematic parameters were assessed using paired parametric methods. RESULTS: Improvements were measured in popliteal angle, knee contracture, peak stance phase knee extension, sagittal plane range of motion of the knee during walking, Gait Deviation Index, and pediatric outcomes data collection instrument Global score. Nearly 80% of the cohort (15/19 patients) demonstrated a significant or moderate response to the intervention, whereas 20% demonstrated no improvement. Of note, significantly increased anterior pelvic tilt was also observed. CONCLUSIONS: Hamstring lengthening combined with a serial casting protocol was associated with significant postoperative improvements in a range of clinical (eg, knee contracture), functional (eg, pediatric outcomes data collection instrument Global), and kinematic (eg, knee extension in stance) parameters. Improvements following this minimally invasive surgery were comparable to outcomes from procedures with higher complication rates. LEVEL OF EVIDENCE: This is a Level III Therapeutic Study (retrospective study investigating the results of a treatment).