Head Impact Exposure in Female Collegiate Soccer by Activity Type.

Soccer, one of the most popular sports in the world, has one of the highest rates of sports-related concussions. Additionally, soccer players are frequently exposed to nonconcussive impacts from intentionally heading the ball, a fundamental component of the sport. There have been many studies on head impact exposure in soccer, but few focus on soccer practices or practice activities. This study aimed to characterize the frequency and magnitude of head impacts in National Collegiate Athletic Association Division I female soccer practice activities using a custom-fit instrumented mouthpiece. Sixteen players were instrumented over the course of 54 practice sessions. Video analysis was performed to verify all mouthpiece-recorded events and classify practice activities. Category groupings of practice activities include technical training, team interaction, set pieces, position-specific, and other. Differences in head impact rates and peak resultant kinematics were observed across activity types and category groupings. Technical training had the highest impact rate compared to other category groupings. Impacts occurring during set piece activities had the highest mean kinematic values. Understanding drill exposure can help inform coaches on training plans aimed to reduce head impact exposure for their athletes.

Characterization of head impact exposure in boys' youth ice hockey.

Ice hockey has one of the highest concussion rates among youth sports. Sensor technology has been implemented in contact and collision sports to inform the frequency and severity of head impacts experienced on-ice. However, existing studies have utilized helmet-mounted sensors with limited accuracy. The objective of this study was to characterize head kinematics of contact events in a sample of youth boys' hockey players using a validated instrumented mouthpiece with improved accuracy. Head kinematics from 892 video-verified events were recorded from 18 athletes across 127 sessions. Median peak resultant linear acceleration, rotational velocity, and rotational acceleration of video-verified events were 7.4 g, 7.7 rad/s, and 576 rad/s2, respectively. Contact events occurred at a higher rate in games (2.48 per game) than practices (1.30 per practice). Scenarios involving head contact had higher peak kinematics than those without head contact. This study improves our understanding of head kinematics in boys' youth hockey.

Characterization of On-Field Head Impact Exposure in Youth Soccer.

The objective of this research was to characterize head impacts with a validated mouthpiece sensor in competitive youth female soccer players during a single season with a validated mouthpiece sensor. Participants included 14 youth female soccer athletes across 2 club-level teams at different age levels (team 1, ages 12-13 y; team 2, ages 14-15 y). Head impact and time-synchronized video data were collected for 66 practices and games. Video data were reviewed to characterize the type and frequency of contact experienced by each athlete. A total of 2216 contact scenarios were observed; heading the ball (n = 681, 30.7%) was most common. Other observed contact scenarios included collisions, dives, falls, and unintentional ball contact. Team 1 experienced a higher rate of headers per player per hour of play than team 2, while team 2 experienced a higher rate of collisions and dives. A total of 935 video-verified contact scenarios were concurrent with recorded head kinematics. While headers resulted in a maximum linear acceleration of 56.1g, the less frequent head-to-head collisions (n = 6) resulted in a maximum of 113.5g. The results of this study improve the understanding of head impact exposure in youth female soccer players and inform head impact exposure reduction in youth soccer.

On-Field Evaluation of Mouthpiece-and-Helmet-Mounted Sensor Data from Head Kinematics in Football.

PURPOSE: Wearable sensors are used to measure head impact exposure in sports. The Head Impact Telemetry (HIT) System is a helmet-mounted system that has been commonly utilized to measure head impacts in American football. Advancements in sensor technology have fueled the development of alternative sensor methods such as instrumented mouthguards. The objective of this study was to compare peak magnitude measured from high school football athletes dually instrumented with the HIT System and a mouthpiece-based sensor system. METHODS: Data was collected at all contact practices and competitions over a single season of spring football. Recorded events were observed and identified on video and paired using event timestamps. Paired events were further stratified by removing mouthpiece events with peak resultant linear acceleration below 10 g and events with contact to the facemask or body of athletes. RESULTS: A total of 133 paired events were analyzed in the results. There was a median difference (mouthpiece subtracted from HIT System) in peak resultant linear and rotational acceleration for concurrently measured events of 7.3 g and 189 rad/s2. Greater magnitude events resulted in larger kinematic differences between sensors and a Bland Altman analysis found a mean bias of 8.8 g and 104 rad/s2, respectively. CONCLUSION: If the mouthpiece-based sensor is considered close to truth, the results of this study are consistent with previous HIT System validation studies indicating low error on average but high scatter across individual events. Future researchers should be mindful of sensor limitations when comparing results collected using varying sensor technologies.

Assessing the association between on-field heading technique and head impact kinematics in a cohort of female youth soccer players.

There is concern that exposure to soccer headers may be associated with neurological sequelae. Training proper heading technique represents a coachable intervention that may reduce head acceleration exposure. The objective was to assess relationships between heading technique and head kinematics in female youth soccer players. Fourteen players (mean age = 14.4 years) wore instrumented mouthpieces during practices and games. Headers were reviewed by three raters to assign a technique score. Mixed models and LASSO regression evaluated associations of technique with peak linear acceleration (PLA), rotational acceleration (PRA), rotational velocity (PRV), and head impact power ratio (HIP Ratio) while adjusting for session type and ball delivery. Two hundred eighty-nine headers (n = 212 standing, n = 77 jumping) were analyzed. Technique score (p = 0.043) and the technique score - session type interaction (p = 0.004) were associated with PRA of standing headers, whereby each 10-unit increase in technique score was associated with an 8.6% decrease in PRA during games but a 5.1% increase in PRA during practices. Technique was not significantly associated with any other kinematic metrics; however, peak kinematics tended to decrease as technique score increased. LASSO regression identified back extension and shoulder/hip alignment as important predictors of peak kinematics. Additional research on heading technique and head acceleration is recommended.

Characterizing Exposure to Head Acceleration Events in Youth Football Using an Instrumented Mouthpiece.

Understanding characteristics of head acceleration events (HAEs) in youth football is vital in developing strategies to improve athlete safety. This study aimed to characterize HAEs in youth football using an instrumented mouthpiece. Youth football athletes (ages 11-13) participating on two teams were enrolled in this study for one season. Each athlete was instrumented with a mouthpiece-based sensor throughout the season. HAEs were verified on film to ensure that mouthpiece-based sensors triggered during contact. The number of HAEs, peak resultant linear and rotational accelerations, and peak resultant rotational velocity were quantified. Mixed effects models were used to evaluate differences in mean kinematic metrics among all HAEs for session type, athlete position, and contact surface. A total of 5,292 HAEs were collected and evaluated from 30 athletes. The median (95th percentile) peak resultant linear acceleration, rotational acceleration, and rotational velocity was 9.5 g (27.0 g), 666.4 rad s-2 (1863.3 rad s-2), and 8.5 rad s-1 (17.4 rad s-1), respectively. Athletes experienced six (22) HAEs per athlete per session (i.e., practice, game). Competition had a significantly higher mean number of HAEs per athlete per session and mean peak rotational acceleration. Peak resultant rotational kinematics varied significantly among athlete positions. Direct head impacts had higher mean kinematics compared to indirect HAEs, from body collisions. The results of this study demonstrate that session type, athlete position, and contact surface (i.e., direct, indirect) may influence HAE exposure in youth football.

Pilot characterization of head kinematics in grassroots dirt track racing.

OBJECTIVE: The objective of this study was to utilize an instrumented mouthpiece sensor to characterize head kinematics experienced by grassroots dirt track race car drivers. METHODS: Four dirt track race car drivers (ages 16-19) were instrumented with custom mouthpiece sensors capable of accurately measuring head motion during racing. Sensors were deployed before races and recorded tri-axial linear acceleration and rotational velocity for approximately 10 min at 200 Hz. Film review was performed to identify data associated with racing laps. For each lap, moving average kinematics were computed and subtracted from the head motion signals to obtain 'adjusted' head motion accounting for lower frequency variance due to periodic motion around the track. From adjusted data, linear and angular head perturbations (i.e., deviations from moving average) were extracted using a custom algorithm. RESULTS: Data was collected during 400 driver-races. A total of 2438 laps were segmented from mouthpiece recordings. The median (95th percentile) peak linear acceleration, rotational velocity, and rotational acceleration of all laps were 5.33 (8.28) g, 2.89 (4.60) rad/s, and 179 (310) rad/s2, respectively. Angular perturbations occurred most frequently about the anterior-posterior axis (median lap frequency = 6.39 Hz); whereas linear perturbations occurred most frequently in the inferior-superior direction (7.96 Hz). Nine crash events were recorded by the mouthpiece sensors. The median (95th percentile) peak head kinematics of these events were 13.4 (36.6) g, 9.67 (21.9) rad/s, and 630 (1330) rad/s2. CONCLUSIONS: Mouthpiece sensors can be used to measure head kinematics during active racing. Laps, head perturbations, and crashes may be useful units of observation to describe typical head kinematic exposure experienced by drivers while racing. Subsequent research is needed to understand the associations between repetitive racing exposure and neurological function. Higher magnitude events (i.e., crashes) are not uncommon and may result in concussion or more severe injury. Results represent novel characterizations of head kinematic exposure experienced in a dirt track racing environment. This information may inform evidence-based strategies (e.g., vehicle/seat design) to improve driver safety.

Header biomechanics in youth and collegiate female soccer.

Concerns about the effects of intentional heading in soccer have led to regulatory restrictions on headers for youth players. However, there is limited data describing how header exposure varies across age levels, and few studies have attempted to compare head impact exposure across different levels of play with the same sensor. Additionally, little is known about the biomechanical response of the brain to header impacts. The objective of this study was to evaluate head kinematics and the resulting tissue-level brain strain associated with intentional headers among youth and collegiate female soccer players. Six youth and 13 collegiate participants were instrumented with custom mouthpiece-based sensors measuring six-degree-of-freedom head kinematics of headers during practices and games. Kinematics of film-verified headers were used to drive impact simulations with a detailed brain finite element model to estimate tissue-level strain. Linear and rotational head kinematics and strain metrics, specifically 95th percentile maximum principal strain (ε1,95) and the area under the cumulative strain damage measure curve (VSM1), were compared across levels of play (i.e., youth vs. collegiate) while adjusting for session type and ball delivery method. A total of 483 headers (n = 227 youth, n = 256 collegiate) were analyzed. Level of play was significantly associated with linear acceleration, rotational acceleration, rotational velocity, ε1,95, and VSM1. Headers performed by collegiate players had significantly greater mean head kinematics and strain metrics compared to those performed by youth players (all p < .001). Targeted interventions aiming to reduce head impact magnitude in soccer should consider factors associated with the level of play.

Comparison of women's collegiate soccer header kinematics by play state, intent, and outcome.

Although most head impacts in soccer are headers, limited knowledge exists about how header magnitude varies by on-field scenario. This study aimed to compare head kinematics during on-field headers by play state (i.e., corner kick, goal kick, free kick, throw-in, drill, or live ball), intent (i.e., pass, shot, or clearance), and outcome (i.e., successful or unsuccessful). Fifteen female collegiate soccer players were instrumented with mouthpiece-based head impact sensors during 72 practices and 24 games. A total of 336 headers were verified and contextualized via film review. Play state was associated with peak linear acceleration, rotational acceleration, and rotational velocity (all p < .001) while outcome was associated with peak linear acceleration (p < .010). Header intent was not significantly associated with any kinematic metric. Headers during corner kicks (22.9 g, 2189.3 rad/s2, 9.87 rad/s), goal kicks (24.3 g, 2658.9 rad/s2, 10.1 rad/s), free kicks (18.0 g, 1843.3 rad/s2, 8.43 rad/s), and live balls (18.8 g, 1769.7 rad/s2, 8.09 rad/s) each had significantly greater mean peak linear acceleration (all p < .050), rotational acceleration (all p < .001), and rotational velocity (all p < .001) than headers during drills (13.0 g, 982.4 rad/s2, 5.28 rad/s). Headers during goal kicks also had a significantly greater mean rotational acceleration compared to headers during live ball scenarios (p < .050). Successful headers (18.3 g) had a greater mean peak linear acceleration compared to unsuccessful headers (13.8 g; p < .010). Results may help inform efforts to reduce head impact exposure in soccer.

Reliability of analysis of the bone mineral density of the second and fifth metatarsals using dual-energy x-ray absorptiometry (DXA).

BACKGROUND: Metatarsal fractures, especially of the fifth metatarsal, are common injuries of the foot in a young athletic population, but the risk factors for this injury are not well understood. Dual-energy x-ray absorptiometry (DXA) provides reliable measures of regional bone mineral density to predict fracture risk in the hip and lumbar spine. Recently, sub-regional metatarsal reliability was established in fresh cadaveric specimens and associated with ultimate fracture force. The purpose of this study was to assess the reliability of DXA bone mineral density measurements of sub-regions of the second and fifth metatarsals in a young, active population. METHODS: Thirty two recreationally active individuals participated in the study, and the bone density of the second (2MT) and fifth (5MT) metatarsals of each subject was measured using a Hologic QDR x-ray bone densitometer. Scans were analyzed separately by two raters, and regional bone mineral density, bone mineral content, and area measurements were calculated for the proximal, shaft, and distal regions of the bone. Intra-rater, inter-rater, and scan-rescan reliability were then determined for each region. RESULTS: Proximal and shaft bone mineral density measurements of the second and fifth metatarsal were reliable. ICC's were variable across regions and metatarsals, with the distal region being the poorest. CONCLUSIONS: Bone mineral density measurements of the metatarsals may be a better indicator of fracture risk of the metatarsals than whole body measurements. A reliable method for measuring the regional bone mineral densities of the metatarsals was found. However, inter-rater reliability and scan-rescan reliability for the distal regions were poor. Future research should examine the relationship between DXA bone mineral density measurements and fracture risk at the metatarsals.