OBJECTIVE:Despite the identification of persistent neuromusculoskeletal control deficits and secondary musculoskeletal (MSK) injury after a concussion, no clear explanation exists to explain this interaction. This article explored the association between the intention to disclose a concussion and intention to disclose an MSK injury among adolescent athletes. DESIGN:Cross-Sectional. SETTING:Online Survey. PATIENTS OR OTHER PARTICIPANTS:Five hundred sixty-four athletes between the ages of 12 and 18 years [male = 58.2%, age = 15.8 (1.8)]. INDEPENDENT VARIABLES:Sex, gender, age, and socioeconomic status. MAIN OUTCOME MEASURES:Online survey exploring determinants of musculoskeletal and concussion injury disclosure intentionality, knowledge of signs and symptoms, as well as attitudes, perceived social norms, and perceived behavioral control surrounding injury disclosure. RESULTS:There was a strong, positive correlation between intention to disclose a concussion and intention to disclose an MSK injury (r = 0.578, P < 0.001). Knowledge of signs, symptoms, and consequences, attitudes toward disclosure, and perceived social norms surrounding injury disclosure of both concussion and MSK injury were also shown to be significant predictive determinates. Male adolescent athletes were significantly more likely to report both an MSK injury and a concussion. In addition, although a history of concussion decreased concussion disclosure intentionality, a history of MSK injury increased MSK injury disclosure intentionality. CONCLUSIONS:Intention to disclose a concussion was positively associated with intention to disclose an MSK injury. Future studies should address the effect of cross-cutting interventions to improve attitudes surrounding concussion and MSK injury disclosure that may also influence perceived social norms surrounding injury reporting.

Context: Although research indicates that the key to minimizing the effect of musculoskeletal injury, improving care, and mitigating long-term effects is to improve early injury care seeking, little is known about barriers to early musculoskeletal injury disclosure and care seeking. Objective: To identify which determinants predicted sportrelated musculoskeletal (MSK) injury disclosure by adolescent athletes. Design: Cross-sectional study. Setting: Online survey. Patients or Other Participants: A total of 564 adolescent athletes (58% male, age = 15.81 +/- 1.8 years). Main Outcome Measure(s): Online survey exploring determinants of age, gender, race, socioeconomic status, injury knowledge, attitudes, perceived social norms, and perceived behavioral control surrounding MSK injury disclosure, intention to disclose MSK injury, and actual behavior of disclosing MSK injury. Results: Of the respondents, 457 (80.2%) reported having sustained >1 (mean = 3.2 +/- 2.2; range = 1-10) MSK injuries related to sport. Those who endorsed having experienced an MSK injury disclosed not reporting or purposefully hiding 77% of their suspected MSK injuries. Several factors influenced a high intention to disclose MSK injury. Specifically, for each unit increase in total MSK injury knowledge (Exp[beta] = 1.061, (3 = 0.054, P = .020, 95% CI = 1.031, 1.221) and attitude (Exp[beta] = 1.070, (3 = 0.064, P < .001, 95% CI = 1.027, 1.115) score, 6% and 7% increases in the likelihood of a high intention to disclose an MSK injury, respectively, were observed. Moreover, for each unit increase in the social norm score (Exp[beta] = 1.178, beta= 0.164, P < .001, 95% CI = 1.119, 1.241), an 18% increase in the likelihood of a high intention to disclose an MSK injury was noted. Conclusions: Designing interventions geared toward increasing the knowledge of signs and symptoms of MSK injury, improving attitudes surrounding disclosure, and better understanding the social context of disclosing MSK injuries may improve MSK injury disclosure behavior and reduce the associated social and economic burdens of these injuries.

OBJECTIVE: To estimate anterior cruciate ligament reconstruction (ACLR) return-to-play (RTP) factors and proportions across all National Collegiate Athletics Association (NCAA) sports. DESIGN: Systematic review with prognosis and etiology components. LITERATURE SEARCH: Two independent reviewers searched PubMed, Cochrane Library, and Embase databases using terms related to RTP, ACLR, and NCAA for articles published up to June 30, 2023. STUDY SELECTION CRITERIA: Articles were included if RTP proportions or factors affecting RTP were reported and if the study population included NCAA collegiate athletes recovering from an ACLR. DATA SYNTHESIS: The proportion represents the total number of athletes who returned to play after ACLR over the total number of ACLR athletes from each cohort. The cumulative proportion represents the aggregated total from each included study. When eligibility information was available (ie, athletes in their final year of eligibility), RTP proportions were adjusted. The Newcastle-Ottawa Scale (NOS) was used to assess the study quality and scored by 2 raters. RESULTS: Nine studies were included. RTP criteria varied across the studies. Proportions of RTP ranged from 69% to 92%, with a cumulative RTP proportion after ACLR of 84% (628/745). The primary factors associated with the proportion of RTP were scholarship status, competitive eligibility remaining, depth chart position, and surgical graft type. CONCLUSIONS: The cumulative proportion of RTP was 84% and was associated with patient-specific and operative factors. Psychological and functional factors were not routinely reported, and rehabilitation protocols were unknown. Data were not explicitly available for any athletes outside of Division I. The criteria for RTP after ACLR varied. J Orthop Sports Phys Ther 2024;54(10):1-9. Epub 10 September 2024. https://doi.org/10.2519/jospt.2024.12483.

Context: Individuals with anterior cruciate ligament reconstruction (ACLR) often fail to return to their previous level of sport performance. Although multifaceted, this inability to regain preinjury performance may be influenced by impaired plyometric ability attributable to chronic quadriceps dysfunction. Whole-body vibration (WBV) acutely improves quadriceps function and biomechanics after ACLR, but its effects on jumping performance outcomes such as jump height, the reactive strength index (RSI), and knee work and power are unknown. Objective: To evaluate the acute effects of WBV on measures of jumping performance in those with ACLR. Design: Crossover study design. Setting: Research laboratory. Patients or Other Participants: Thirty-six individuals with primary, unilateral ACLR. Intervention(s): Participants stood on a WBV platform in a mini-squat position while vibration or no vibration (control) was applied during six 60-second bouts with 2 minutes of rest between bouts. Main Outcome Measure(s): Double-leg jumping tasks were completed preintervention and postintervention (WBV or control) and consisted of jumping off a 30-cm box to 2 force plates half the participant's height away. The jumping task required participants to maximally jump vertically upon striking the force plates. Results: Whole-body vibration did not produce significant improvements in any of the study outcomes (ie, jump height, RSI, and knee work and power) in either limb (P = .053-.839). Conclusions: These results suggest that a single bout of WBV is insufficient for improving jumping performance in individuals with ACLR. As such, using WBV to acutely improve jumping performance post-ACLR is likely not warranted. Future research should evaluate the effects of repeated exposure to WBV in combination with other plyometric interventions on jumping performance.

BACKGROUND:Quadriceps dysfunction is common following anterior cruciate ligament reconstruction and contributes to aberrant gait biomechanics. Changes in quadriceps composition also occur in these patients including greater concentrations of non-contractile tissue. The purpose of this study was to evaluate associations between quadriceps composition, function, and gait biomechanics in individuals with anterior cruciate ligament reconstruction. METHODS:Forty-eight volunteers with anterior cruciate ligament reconstruction completed gait biomechanics and quadriceps function and composition assessments. Gait biomechanics were sampled during downhill walking (-10° slope) on an instrumented treadmill. Quadriceps function (peak torque and rate of torque development) was assessed via maximal isometric contractions, while composition was evaluated via ultrasound echo intensity. FINDINGS:Greater quadriceps peak torque was associated with a greater peak knee extension moment (r = 0.365, p = 0.015). Greater vastus lateralis echo intensity (i.e. poorer muscle quality) was associated with less knee flexion displacement (r = -0.316, p = 0.032). Greater echo intensity of the vastus lateralis (r = -0.298, p = 0.044) and rectus femoris (r = -0.322, p = 0.029) was associated with a more abducted knee angle at heel strike. Quadriceps peak torque explained 11-16% of the variance in echo intensity. INTERPRETATION:Both quadriceps function and composition influence aberrant gait biomechanics following anterior cruciate ligament reconstruction. Quadriceps composition appears to provide insight into quadriceps dysfunction independent of muscle strength, as they associated with different gait biomechanics outcomes and shared minimal variance. Future research is necessary to determine the influence of changes in quadriceps composition on joint health outcomes.

Quadriceps dysfunction is common following anterior cruciate ligament reconstruction (ACLR) and likely contributes to post-traumatic knee osteoarthritis (PTOA). Poor quadriceps muscle quality (i.e. greater non-contractile composition) and function are reported in the ACLR limb and are related to poorer self-reported function. While gait biomechanics over level ground typically normalize within two years post-ACLR, aberrant gait characteristics are still present during downhill walking. As greater demands are placed on the quadriceps walking downhill, poor muscle quality and neuromuscular characteristics of the quadriceps may contribute to aberrant gait biomechanics. PURPOSE: To evaluate associations between quadriceps morphology, function, and gait biomechanics during downhill walking in individuals with ACLR. METHODS: 48 volunteers who were 3.8 ± 2.5 years removed from ACLR walked on an instrumented treadmill at their self-selected speed on a downhill slope (-10°) for 2 minutes. Gait outcomes (peak vGRF, knee flexion and adduction angles, and internal knee extension and abduction moments; and sagittal and frontal knee angles at heel strike) in the ACLR limb were averaged over the first 10 steps from the second minute of gait. Quadriceps function was assessed via isometric peak torque (PT). Quadriceps morphology was assessed via echo intensity (EI) of the vastus lateralis (VL) and rectus femoris (RF) obtained from transverse plane ultrasound images. Partial correlations were used to evaluate associations between quadriceps characteristics (PT and EI) and gait biomechanics outcomes while controlling for gait speed. RESULTS: Greater quadriceps PT was associated with a greater peak knee extension moment (r = 0.365, p = 0.015). Greater VL EI was associated with lesser knee flexion displacement (r = -0.316, p = 0.032), and greater EI of the RF (r = -0.322, p = 0.029) and VL (r = -0.298, p = 0.044) was associated with a more abducted knee angle at heel strike. CONCLUSION: Those with poorer quadriceps muscle quality strike the ground with less knee flexion and a more abducted knee, possibly to avoid medial compartment loading, where PTOA is most common. Future research should investigate interventions aimed at improving quadriceps quality/composition and function post-ACLR and their influence on downhill gait.

PURPOSE:Neuromuscular deficits and atrophy after anterior cruciate ligament reconstruction (ACLR) may be accompanied by changes in muscle composition and poor quadriceps muscle quality (QMQ). Quadriceps atrophy occurs after ACLR but improves within the first three postoperative months, yet this hypertrophy could be attributable to increases in noncontractile tissue (i.e., poor QMQ). The purposes of this study were to evaluate changes in QMQ after ACLR and to determine if changes in QMQ and cross-sectional area (CSA) occur in parallel or independently. METHODS:A longitudinal prospective cohort design was implemented to evaluate QMQ and CSA in 20 individuals with ACLR and 12 healthy controls. Participants completed three testing sessions (baseline/presurgery, 1 month, and 3 months) during which ultrasound images were obtained from the vastus lateralis (VL) and rectus femoris (RF). QMQ was calculated as the echo intensity (EI) of each image, with high EI representing poorer QMQ. Anatomical CSA was also obtained from each image. RESULTS:RF and VL EI were greater at 1 and 3 months in the ACLR limb compared with baseline and the contralateral limb and did not change between 1 and 3 months. VL and RF CSA in the ACLR limb were smaller at 1 and 3 months compared with the contralateral limb and controls (VL only) but increased from 1 to 3 months. Changes in QMQ and CSA were not correlated. CONCLUSIONS:QMQ declines within the first month after ACLR and does not improve by 3 months although hypertrophy occurs, suggesting that these morphological characteristics change independently after ACLR. Poorer QMQ represents greater concentration of noncontractile tissues within the muscle and potentially contributes to chronic quadriceps dysfunction observed after ACLR.

PURPOSE:This study aimed to describe the epidemiology of ACL tears in NCAA men's and women's sports. METHODS:Injury and exposure data collected within the NCAA Injury Surveillance Program from 2014/2015 to 2018/2019 were analyzed. ACL tear frequencies, injury rates (IR), and injury proportions were used to describe injury incidence by sport, event type, injury mechanism, and injury history. Injury rate ratios (IRR) were used to examine differential injury rates, and injury proportion ratios (IPR) were used to examine differential distributions. RESULTS:A total of 729 ACL tears were reported from 8,474,401 recorded athlete exposures (AE) during the study period (IR = 0.86 per 10,000 AE), and the competition-related ACL tear rate was higher than the practice-related rate (IRR = 5.52, 95% confidence interval [CI] = 4.75-6.39). Among men's sports, the highest overall ACL tear rate was observed in men's football (IR = 1.44 per 10,000 AE), whereas among women's sports, the highest overall rate was observed in women's soccer (IR = 2.60 per 10,000 AE). Among sex-comparable sports, ACL tear rates were higher in women's basketball, softball, and soccer, as compared with their men's counterparts. ACL tears were more prevalently attributed to player contact mechanisms in men's sports than women's sports (IPR = 1.73, 95% CI = 1.37-2.19), but more prevalently attributed to noncontact mechanisms in women's sports than men's sports (IPR = 1.17, 95% CI = 1.01-1.35). CONCLUSIONS:ACL tear risk in women's sports continues to warrant attention and prevention efforts. Given the differential rates by event type, future research efforts may also evaluate initiatives to reduce competition-related injury burden in NCAA sports.

Isokinetic thigh strength symmetry is assessed to inform return to sport (RTS) decisions following ACL reconstruction (ACLR). However, ACL reinjury rates are high suggesting isokinetic strength symmetry may not identify functional impairments and readiness to RTS. PURPOSE: To examine whether isokinetic strength limb symmetries are related to functional hop and landing biomechanics limb symmetries. METHODS: Retrospective analyses were performed on 21 ACLR RTS testing sessions (3 M, 8F: 18.2 ± 3.1 yrs, 69.4 ± 19.0 kg, 169.5 ± 6.3 cm, 8.9 ± 2.8 months post-op). Peak concentric knee extension and flexion torque were measured bilaterally at 90, 180, and 240 deg/sec using an isokinetic dynamometer. Single leg forward hop (FH), crossover hop (CH), and triple hop (TH) max distances were recorded across 2 trials. 3D biomechanics were evaluated following a single leg hop (SLH) over a hurdle (height = 7.6 cm) and a drop vertical jump (DVJ) from a box (height = 20 cm). The average peak external knee abduction moment, vertical ground reaction force (vGRF), and knee valgus ROM during the deceleration phase [initial contact (vGRF>10 N) to peak knee flexion] were calculated across 3 trials. Limb symmetry index (LSI) for each isokinetic torque and functional hop test, and normalized symmetry index (NSI) for landing biomechanics were calculated. Pearson correlations evaluated whether isokinetic torque limb symmetries were related to functional hop and landing biomechanics limb symmetries. RESULTS: All correlations are summarized in Table 1. CONCLUSION: Extension torque symmetry at 90 deg/sec was related to functional hop tests and to the SLH distance across all testing speeds. Flexion torque symmetry at 90 deg/sec was related to DVJ knee valgus ROM. No other relationships were observed with other hop tests or landing biomechanics. RTS decisions based on isokinetic strength symmetry may not account for all functional performance and landing asymmetries that increase risk of reinjury.

The countermovement jump (CMJ) is commonly utilized by sport performance staff and may provide insight into neuromuscular function. However, most CMJ force plate software calculates 70+ metrics from a single CMJ, leading to clinician information overload and confusion. Many of these metrics are mathematical derivatives of each other and likely provide duplicative information. PURPOSE: Use a data-driven approach to determine how many “things” CMJs measure and classify the 70+ metrics by what they measure. METHODS: As standard of practice, the West Virginia University Football Team regularly performs CMJ testing conducted by the Strength & Conditioning Staff. Since 2021, 6,154 CMJs have been performed by 177 athletes using the Hawkin Dynamics force plate system. Hawkin Dynamics calculates 74 metrics for each CMJ. A parallel plot analysis was performed to determine how many components or “things” are being measured across the 74 metrics. Sparse principal component analysis which maximizes near-zero weight for each component, then allowed for each metric to be grouped or classified according to the component upon which they have the greatest weight. RESULTS: The parallel plot analysis indicated that 9 components should be extracted. The grouping of CMJ metrics can be seen in Tables 1 & 2. CONCLUSION: While the number of metrics derived from CMJs seem to expand each year, only 9 “things” are actually being measured. It is suggested that clinicians use the classification groupings from this analysis and select no more than one metric from each group to limit the unnecessary evaluation of duplicative information. Table 1. - Group 1 Group 2 Group 3 Group 4 Jump Height Avg. Braking Force Player Weight L/R Peak Braking Force Avg. Relative Propulsive Force L. Force at Peak Braking Force Jump Momentum L/R Avg. Braking Force Peak Relative Propulsive Force R. Force at Peak Braking Force Propulsive Net Impulse L/R Peak Propulsive Force Flight Time Peak Braking Force Positive Impulse L/R Avg. Propulsive Force Avg. Propulsive Velocity Avg. Propulsive Force Avg. Propulsive Power L/R Avg. Braking Rate of Force Development Takeoff Velocity L. Avg. Braking Force Peak Propulsive Power L/R Braking Impulse Index Peak Velocity R. Avg. Braking Force L. Avg. Propulsive Force L/R Propulsive Impulse Index Avg. Relative Propulsive Power Peak Propulsive Force R. Avg. Propulsive Force L/R Peak Landing Force Peak Relative Propulsive Power Positive Net Impulse Avg. Landing Force L/R Avg. Landing Force mRSI L. Force at Peak Propulsive Force L. Avg. Landing Force Relative Propulsive Net Impulse Force at Minimum Displacement R. Avg. Landing Force R. Force at Peak Propulsive Force Propulsive Impulse Braking Impulse Table 2. - Group 5 Group 6 Group 7 Group 8 Group 9 Stiffness Braking Phase Avg. Relative Braking Force Unweighting Phase Countermovement Depth Propulsive Phase Impulse Ratio Unweighting Phase Percentage Peak Landing Force Braking Phase Percentage Time to Takeoff Avg. Braking Velocity Braking Rate of Force Development Relative Peak Landing Force Propulsive Phase Percentage Braking Net Impulse Avg. Braking Power R. Avg. Braking Rate of Force Development L. Force at Peak Landing Force RSI Relative Braking Impulse Avg. Relative Braking Power L. Avg. Braking Rate of Force Development R. Force at Peak Landing Force Relative Braking Net Impulse Peak Braking Power Peak Relative Braking Force Relative Propulsive Impulse Peak Relative Braking Power

Advancements in technology allow for the collection of motion data in non-laboratory settings utilizing portable cameras and software eliminating the burdens of time intensive set up (e.g. placing reflective markers) and training. However, when interpreting markerless motion capture data it is important to consider the variance of normal human movement during the administered movement tasks, particularly when deploying serial movement screenings throughout the course of a sports season or rehabilitation. PURPOSE: To determine the inter-day variance of frontal plane knee movement during double- and single-leg squats utilizing markerless motion capture. METHODS: 13 participants (6 M, 7 F) completed 3 consecutive movement screens per day/session on 3 consecutive days utilizing the Moovment software and Microsoft Azure Kinect camera sampled at 15 Hz. Frontal plane displacement (cm; medial = negative, lateral = positive) for double- and single-leg squats were evaluated and defined as the position of the knee center at the bottom of the squat minus its starting position. Relative inter-day variance was evaluated via intraclass correlation coefficient (ICC) and absolute inter-day variance/bias was determined via Bland-Altman Limits of Agreement (LOA) with grid expansion matching. RESULTS: Moderate relative relationships were observed and 95% of the data points fell within a 6 cm to 8 cm range (difference between Upper and Lower LOA) with minimal bias. (Table 1) CONCLUSION: When using markerless motion capture technology to test patients across time, differences observed which exceed the LOA bands are likely to be “real” or potentially meaningful; whereas, changes within the LOA bands are expected healthy human variation. These findings aide clinicians looking to differentiate typical human movement variability from aberrant biomechanics. Future research should further evaluate the efficacy and reliability of markerless motion capture devices. Table 1 - ICC Lower LOA Upper LOA Bias Double-leg squat: Right leg 0.663 -3.880 3.313 -0.283 Double-leg squat: Left leg 0.618 -2.964 3.208 0.122 Single-leg squat: Right leg 0.537 -2.99 3.768 0.389 Single-leg squat: Left leg 0.533 -3.822 4.178 0.178

Context Despite the increased risk of musculoskeletal (MSK) injury after a concussion, little is known about the determinants of such a risk. Moreover, the authors of previous reports of increased risk of MSK injury after a concussion have neglected to account for the high level of undisclosed concussions. Objective To explore the association between the intention to disclose a possible concussion and the intention to disclose an MSK injury. Design Cross-sectional study. Setting Online survey. Patients or Other Participants One hundred seven National Collegiate Athletic Association Division I athletes (females = 79%, age = 19.4 ± 1.4 years). Main Outcome Measure(s) Online survey exploring determinants such as injury knowledge, attitudes, perceived social norms, and perceived behavioral control surrounding concussive and MSK injury disclosure. Results A significant association between high intention to disclose a concussion and high intention to disclose an MSK injury (χ2 = 19.276, P < .001, Cramer V = 0.482) was observed. Spearman rank correlations suggested no correlation between concussion nondisclosure (25%) and MSK injury nondisclosure (52%). Multivariate binomial regressions indicated that perceived social norms were the strongest determinant (β = 1.365, P = .002) of high intention to disclose concussion, while attitudes toward MSK injury (β = 1.067, P = .005) and perceived social norms (β = 1.099, P = .013) were the strongest determinants of high intention to report MSK injury. Conclusions Individuals with high intention to report concussion symptoms also demonstrated high intention to report MSK injury. Strong positive associations were seen between known determinants of intention to disclose concussion and adapted versions of those same determinant domains in intention to disclose MSK injury. As those with high intention to disclose concussion also displayed high intention to disclose MSK injury, intention to disclose injuries generally may play a role in explaining the increase in MSK injury after a concussion.

BACKGROUND:Aberrant gait biomechanics contribute to post-traumatic knee osteoarthritis development following anterior cruciate ligament reconstruction (ACLR). Walking gait biomechanics are typically evaluated post-ACLR by identifying discrete, peak values in the load acceptance phase of gait (i.e. first 50 %). As these approaches evaluate a single time instant during the gait cycle, functional data analysis (FDA) techniques that evaluate the entire stance phase waveform are becoming more common in the literature. However, it is unclear if these analysis approaches identify the same biomechanical phenomena.RESEARCH QUESTION:The purpose of this study was to determine whether four gait biomechanics analysis approaches identify the same aberrant gait characteristics in individuals with ACLR.METHODS:Twenty-four individuals with ACLR and 24 healthy controls completed gait analyses on an instrumented treadmill. Four analysis approaches were employed to compare the vertical ground reaction force and sagittal knee angles and moments during the first 50 % of the stance phase between groups and between limbs in the ACLR cohort: 1) comparison of peak values from individual trials (Peak), 2) comparison of peak values from time-normalized ensemble waveforms (Ensemble Peak), 3) FDA via functional ANCOVA (FANCOVA), and 4) FDA evaluating overlap of the 95 % confidence intervals for each waveform (FDA-CI).RESULTS:The Peak, Ensemble Peak, and FANCOVA approaches identified highly similar group and limb differences in the biomechanics outcomes with respect to both magnitude and temporal location. However, the FANCOVA approach indicated that these differences were distributed across large portions of the load acceptance phase and that differences existed outside the first 50 % of stance. The FDA-CI approach was generally not effective for identifying aberrant gait biomechanics.SIGNIFICANCE:Peak and FANCOVA approaches to gait analysis provide similar findings. Future research is necessary to determine if the additional information afforded by FANCOVA provides insight regarding the mechanical pathogenesis of post-traumatic knee osteoarthritis.

PURPOSE: Approximately half of all anterior cruiciate ligament (ACL) injuries occur in young, athletic populations, including collegiate athletes. Following ACL injury, there is a heightened risk of secondary ACL injury and post-traumatic osteoarthritis, highlighting the detrimental nature of early life knee injury. Therefore, the purpose of this study was to describe the epidemiology of ACL injury in National Collegiate Athletic Association (NCAA) athletes. METHODS: ACL injuries reported by athletic trainers to the NCAA Injury Surveillance Program during 2014/15 - 2018/19 in 23 NCAA men's and women's sports were examined. Injury incidence (characterized as Injury Rate (IR) per 10,000 athlete exposures (AEs)) was examined both pooled and stratified by event type (practices/competitions). The distribution of ACL injuries was examined by injury mechanism (player contact/non-contact/other) using frequencies (%s). Differential injury incidence was examined across event types and sex (for sex-comparable sports) using Injury Rate Ratios (IRR); IRRs with 95% Confidence Intervals (CI) excluding 1.00 were considered statistically significant. RESULTS: A total of 729 ACL injuries were reported, resulting in IRs of 0.80/10,000 AEs and 0.95/10,000 AEs in men's and women's sports, respectively. ACL injury rates were most commonly reported in men's football (N = 267, IR = 1.44) and women's soccer (N = 118, IR = 2.60). Amongst all sports, competition related ACL rates were higher in men's (IR = 2.37) and women's sports (IR = 2.59) than practice related rates (IRs: men's = 0.43, women's = 0.48). Practice injury rates remained stable across the study period, while competition rates fluctuated. Injuries were more prevalently attributed to player contact in men's sports (39.7%) than in women's sports (22.9%). CONCLUSIONS: In most sex-comparable sports, overall ACL rates were higher in women's sports compared to men's sports in NCAA athletes from 2014/15 - 2018/19. Injury rates were greater in competition compared to practice in both men's and women's sports. This corroborates previous literature detailing higher ACL injury rates during competition and in females. Future research should evaluate the translation between injury reduction programming during practice to competition-related ACL injury programming.

Ironman-distance triathlons are multisport endurance events with rigorous demands and injury risk. Although injury profiles of triathletes have been reported, studies investigating injuries related to traumatic events are few and limited by self-reported injuries, small sample sizes, and inconsistent injury definitions. PURPOSE: To determine and characterize musculoskeletal and dermatological trauma-related injuries among world championship Ironman-distance triathletes. METHODS: A retrospective study of 3,646 standardized medical tent records from 2008-2019 was performed. Medical records were documented by nurses and physicians at a single Ironman-distance championship competition and descriptive statistics were utilized to evaluate demographics, injury frequency, and injury type. Chi-Squared analyses were used to compare the frequency of non-trauma and trauma-related injuries during different race segments. RESULTS: In total, 217 athletes presented to the medical tent with trauma-related injuries, an incidence of 59.5 per 1000 athletes. Musculoskeletal (n = 51), dermatologic (n = 119), or a combination of both injuries (n = 47) were common among trauma-related injuries. The most common musculoskeletal pathologies were musculoskeletal pain (37.3%), joint injuries (24.1%), and fractures (14.5%). The most common dermatologic injuries were abrasions (53.3%), lacerations (10.1%), and contusions (9.2%). Trauma-related injuries were predominantly localized to the shoulder (23.5%), head (18.0%), and hip/groin (13.8%). The cycling segment of the race had significantly more trauma-related injuries than the running and swimming segments (χ2 (2) = 116; 18.15 p < .001). Within our analytic sample, 79 athletes did not finish the race, of which 17 (4.7 per 1000 medical encounters) were transferred to the hospital. No statistical significance was observed among sex and age as risk factors for trauma-related injuries. CONCLUSION: Though most trauma-related incidents are often unavoidable during ultra-endurance competition, increased awareness of specific musculoskeletal and dermatological injuries is crucial. These injuries are somewhat common and occur most commonly during the cycling segment of triathlon races.

Aberrant gait biomechanics following anterior cruciate ligament reconstruction (ACLR) likely contribute to post traumatic osteoarthritis (PTOA) development. Gait biomechanics are typically assessed overground, but the use of instrumented/force-measuring treadmills is increasingly common. The purpose of this study was to compare gait biomechanics overground and on an instrumented treadmill in individuals with ACLR and healthy controls. Twenty-four individuals with ACLR and 24 healthy controls completed overground and gait biomechanics assessments. Biomechanical outcomes included peak vertical ground reaction force (vGRF), internal knee extension (KEM) and abduction (KAM) moments, and knee flexion (KFA) and adduction angles; KFA at heel strike; knee flexion displacement; and inter-limb symmetry for each outcome. Peak KEM (P < 0.001, 95%CI [-0.016,-0.007 xBW*Ht]) and vGRF (P < 0.001, 95%CI [-0.09.-0.03 xBW]) were significantly less symmetrical in the ACLR group compared to the control group on the treadmill but not overground. Additionally, peak KEM was smaller in the ACLR limb compared to the contralateral limb both overground (P = 0.005, 95%CI [-0.010,-0.001 xBW*Ht]) and on the treadmill (P < 0.001, 95%CI [-0.015,-0.007 xBW*Ht]), but this difference was 1.8x larger on the treadmill compared to overground. Peak KFA (P = 0.001, 95%CI [-4.2, 1.2]) and vGRF (P < 0.001, 95%CI [-0.07,-0.03 xBW]) were smaller in the ACLR limb on the treadmill but not overground. These findings suggest aberrant gait biomechanics are exacerbated during treadmill walking post-ACLR and that evaluating kinematics and kinetics on instrumented treadmills may be valuable for assessing risk factors of PTOA development.

Quadriceps dysfunction is a common, chronic complication following anterior cruciate ligament reconstruction (ACLR) that contributes to aberrant gait biomechanics and poor joint health. Vibration enhances quadriceps function in individuals with ACLR, but the duration of these effects is unknown. This study evaluated the time course of the effects of whole body vibration (WBV) and local muscle vibration (LMV) on quadriceps function. Twenty-four volunteers with ACLR completed 3 testing sessions during which quadriceps isometric peak torque, rate of torque development, and EMG amplitude were assessed prior to and immediately, 10, 20, 30, 45, and 60 min following a WBV, LMV, or control intervention. WBV and LMV (30 Hz, 2g) were applied during six one-minute bouts. WBV increased peak torque 5-11% relative to baseline and control at all post-intervention time points. LMV increased peak torque 6% relative to baseline at 10 min post-intervention and 4-6% relative to control immediately, 10 min, and 20 min post-intervention. The interventions did not influence EMG amplitudes or rate of torque development. The sustained improvements in quadriceps following vibration, especially WBV, suggest that it could be applied at the beginning of rehabilitation sessions to "prime" the central nervous system, potentially improving the efficacy of ACLR rehabilitative exercise.

Quadriceps dysfunction is common following anterior cruciate ligament reconstruction (ACLR). Whole body (WBV) and local muscle (LMV) vibration improve measures of quadriceps function such as corticomotor excitability, central activation ratio (CAR), peak torque (PT), and rate of torque development (RTD) in those with ACLR. However, it is unknown if baseline quadriceps function influences the response to vibration. PURPOSE: To evaluate relationships between baseline quadriceps function and changes in these measures following WBV and LMV. METHODS: Quadriceps function was assessed in 20 individuals with ACLR (age 21 ± 1 yr; time since ACLR 51 ± 21 mo) prior to and following WBV and LMV administered on separate days. Quadriceps PT, RTD, and CAR were assessed via maximal voluntary isometric contractions (MVIC) during which a supramaximal electrical stimulus was applied. Corticomotor excitability was assessed via the active motor threshold (AMT), motor evoked potential (MEP), and spinal reflexive excitability was assessed via the Hoffmann-reflex (H:M ratio). Six 60s bouts of WBV or LMV (30 Hz, 2 g) were administered while the subject stood in slight knee flexion. Pearson correlations were used to evaluate relationships between baseline values for each measure of quadriceps function and the respective pre-post change scores following WBV. RESULTS: For WBV, lower MEP baseline values were associated with greater MEP change scores (P = 0.02, r = -0.52). No other relationships were significant for WBV (P = 0.19 - 0.88, r = -0.31 - -0.03. For LMV, lower RTD baseline values were associated with greater RTD change scores (P = 0.004, r = -0.61). No other relationships were significant for LMV (P = 0.38 - 0.75, r = -0.21 - 0.12). CONCLUSION: Individuals with lower baseline MEP exhibited greater MEP increases following WBV and those with lower RTD displayed greater RTD increases following LMV. These findings suggest that individuals with ACLR who possess larger deficits in quadriceps function may glean greater benefit from vibration. Quadriceps function is chronically suppressed after ACLR, and vibration may be a viable rehabilitation approach for patients with chronic deficits in quadriceps function. However, ACLR patients in whom quadriceps function is nearly restored may receive limited benefits from this approach.

Background: Altered gait biomechanics have been linked to post-traumatic knee osteoarthritis development following anterior cruciate ligament reconstruction surgery, but the persistence of aberrant gait biomechanics after the first year post-surgery is inconsistent in the literature. Gait biomechanics are typically evaluated on a level surface, but this task may not elucidate discrepancies in individuals further removed from surgery due to the simplicity of the task. Graded surfaces are common in real-world ambulation and may exacerbate aberrant gait biomechanics due to greater mechanical demands. Methods: Forty-seven individuals post-anterior cruciate ligament reconstruction (4 +/- 3 years post-surgery) and forty-seven uninjured controls completed gait analysis under level, uphill, and downhill conditions on an instrumented treadmill. Outcomes included knee flexion displacement and peak knee flexion angle, vertical ground reaction force, and knee extension and abduction moments. Findings: Knee extension moment and knee flexion displacement were lesser in the surgical limb compared to the contralateral during the downhill condition, with lesser knee flexion displacement also observed during the level condition. Additionally, knee extension moment was less symmetrical in the surgical group during both uphill and downhill conditions compared to controls. Knee flexion displacement was less symmetrical in the surgical group during both level and downhill conditions compared to controls. Interpretation: Graded surfaces elucidate aberrant gait biomechanics in individuals more than 1 year post-anterior cruciate ligament reconstruction that are not apparent during level walking. These findings suggest that gait assessment on level surfaces may mask existing deficiencies, and warrant emphasizing ambulation of graded surfaces during anterior cruciate ligament rehabilitation.

Conflicting evidence exists regarding the presence of aberrant gait biomechanics after the first year post-anterior cruciate ligament reconstruction. Overground walking may not elucidate differences in those further removed from surgery due to the unexacting nature of the task. Deleterious gait biomechanics following ACLR are partly attributable to quadriceps dysfunction. Downhill walking may exacerbate aberrant gait biomechanics, as this task places greater demands on the quadriceps compared to level walking. PURPOSE: To compare gait biomechanics between individuals with ACLR and healthy controls during level and downhill walking conditions. METHODS: 24 individuals more than 1 year removed from primary ACLR (83% female, age= 21 ± 3 yr, time since ACLR 44 ± 26 mo, BMI= 23 ± 3 kg/m2) and 24 healthy controls (79% female, age= 21 ± 1 yr, BMI= 24 ± 3 kg/m2) completed both level and downhill (10°grade) gait biomechanics assessments on an instrumented split-belt treadmill at their preferred walking speed. Peak variables were evaluated over the first 50% of stance including the vertical ground reaction force (vGRF), internal knee abduction moment, internal knee extension moment, knee flexion angle, and knee abduction angle. Moments were normalized to %body weight∗height (%BW∗Ht) and vGRF was normalized to %body weight. Dependent variables were compared across groups and conditions via two-way repeated measures ANCOVA controlling for gait speed. RESULTS: There were no significant condition∗group interaction effects nor group main effects for any outcomes. However, there were significant condition main effects for peak internal knee extension moment (p = 0.020, level to downhill mean increase of 0.042 %BW∗Ht) and peak knee flexion angle (p = 0.018, level to downhill mean increase of 13.2°). CONCLUSIONS: Downhill walking necessitates a larger internal extension moment and knee flexion angle compared to level gait. Our results suggest that changes in gait biomechanics between level and downhill conditions do not differ between individuals with ACLR > 1 year post reconstruction and controls. These results suggest that aberrant gait biomechanics may be mitigated over time in those with ACLR.