Lauren A. Pierpoint

Load type influences motor unit recruitment in biceps brachii during a sustained contraction

Twenty subjects participated in four experiments designed to compare time to task failure and motor-unit recruitment threshold during contractions sustained at 15% of maximum as the elbow flexor muscles either supported an inertial load (position task) or exerted an equivalent constant torque against a rigid restraint (force task). Subcutaneous branched bipolar electrodes were used to record single motor unit activity from the biceps brachii muscle during ramp contractions performed before and at 50 and 90% of the time to failure for the position task during both fatiguing contractions. The time to task failure was briefer for the position task than for the force task (P=0.0002). Thirty and 29 motor units were isolated during the force and position tasks, respectively. The recruitment threshold declined by 48 and 30% (P=0.0001) during the position task for motor units with an initial recruitment threshold below and above the target force, respectively, whereas no significant change in recruitment threshold was observed during the force task. Changes in recruitment threshold were associated with a decrease in the mean discharge rate (-16%), an increase in discharge rate variability (+40%), and a prolongation of the first two interspike intervals (+29 and +13%). These data indicate that there were faster changes in motor unit recruitment and rate coding during the position task than the force task despite a similar net muscle torque during both tasks. Moreover, the results suggest that the differential synaptic input observed during the position task influences most of the motor unit pool.

Fatigability of the dorsiflexors and associations among multiple domains of motor function in young and old adults

Declines in neuromuscular function, including measures of mobility, muscle strength, steadiness, and patterns of muscle activation, accompany advancing age and are often associated with reduced quality of life and mortality. Paradoxically, older adults are less fatigable than young adults in some tasks. The purpose of this study was to determine the influence of age on fatigability of the dorsiflexors and to evaluate the ecological validity of this test by comparing it to motor function subdomains known to decline with advancing age. The community-dwelling older adults (n=52, 75.2±6.0years) were more fatigable than young adults (n=26, 22.2±3.7years), as assessed by endurance time for supporting a submaximal load (20% of one-repetition maximum; 1-RM) with an isometric contraction of the dorsiflexor muscles (8.9±0.6min and 15.5±0.9min, p<0.001), including participants matched for 1-RM load and sex (Y: 13.3±4.0min, O: 8.5±6.1min, n=11 pairs, 6 women, p<0.05). When the older adults were separated into two groups (65-75 and 76-90years), however, only endurance time for the oldest group was less than that for the other two groups (p<0.01). All measures of motor function were significantly correlated (all p<0.05) with dorsiflexor endurance time for the older adults, and multiple regression analysis revealed that the variance in endurance time was most closely associated with age, steadiness, and knee flexor strength (R(2)=0.50, p<0.001). These findings indicate that dorsiflexor fatigability provides a valid biomarker of motor function in older adults.

Epidemiology of Injuries in United States High School Track and Field: 2008-2009 Through 2013-2014

Background: Track and field is one of the most popular high school sports among boys and girls, but epidemiological research on the sport and its individual events has been limited. Purpose: To describe injury rates and patterns in boys’ and girls’ high school track and field. Study Design: Descriptive epidemiology study. Methods: A retrospective epidemiological analysis of injury and exposure data from a longitudinal national high school sports injury surveillance system was conducted. Results: From 2008-2009 through 2013-2014, 2485 track and field injuries occurred during 2,962,308 athlete exposures (0.84 injuries per 1000 athlete exposures). Injury rates were higher in competition versus practice for both sexes. Girls had higher injury rates than boys overall (rate ratio, 1.37; 95% CI, 1.27-1.48) and in practice (rate ratio, 1.60; 95% CI, 1.46-1.76), but competition injury rates did not differ. Overuse/chronic injuries accounted for 27.5% and 36.2% of boys’ and girls’ track and field injuries, respectively. The majority of injuries were to the lower extremity. Sprints, distance running, and jumps accounted for over 65% of all track injuries. Boys sustained a greater proportion of injuries in relay events (injury proportion ratio, 2.02; 95% CI, 1.69-2.36) but fewer in hurdle events (injury proportion ratio, 0.51; 95% CI, 0.23-0.78). Conclusion: Injury rates varied by event, sex, and competition versus practice exposure. To increase effectiveness, targeted strategies for injury prevention should be driven by an understanding of such differences. Because many track and field injuries are overuse/chronic across sexes and for both competitions and practices, coaches and athletic trainers should be adept at recognizing early injury symptoms, intervene to treat minor injuries in order to prevent severe injuries, and ensure the prompt diagnosis and management of all injuries.

Injury Recurrence Among High School Athletes in the United States: A Decade of Patterns and Trends, 2005-2006 Through 2015-2016:

Background: As participation in high school athletics increases, so does the number of adolescents experiencing sports-related injury. Understanding injury patterns is an important component to developing and evaluating prevention and rehabilitation programs. Purpose: To analyze recurrent injury rates and patterns among high school athletes, to compare recurrent injuries with new injuries, and to evaluate injury trends over time. Study Design: Descriptive epidemiology study. Methods: High school sports injury data on 24 sports were collected from 2005-2006 through 2015-2016 via the High School RIO (Reporting Information Online) surveillance system. Injury rates were calculated as number of injuries per 10,000 athletic exposures (AEs). Injury rate ratios and injury proportion ratios (IPRs) were calculated to compare differences among subgroups. Results: Overall, 78,005 injuries were sustained during 40,195,806 AEs, for an injury rate of 19.41 per 10,000 AEs. Of these, 69,821 (89.5%) were new injuries, and 8184 (10.5%) were recurrent. The ankle was the most commonly injured body part among recurrent injuries, while the head/face was the most common body part that sustained new injuries. Ligament sprains were more often recurrent, while concussions were more commonly diagnosed as new, although concussions represented 16.7% of recurrent injuries. Trends for recurrent injuries over time were relatively stable. The proportion of athletes who had >3 weeks of time loss or medical disqualification (15.8% vs 13.3%; IPR, 1.19; 95% CI, 1.13-1.26) or who voluntarily withdrew from sport (2.5% vs 1.1%; IPR, 2.33; 95% CI, 2.00-2.73) was significantly greater for recurrent injuries than new injuries. Furthermore, a greater proportion of recurrent injuries resulted in surgery (8.1% vs 6.0%; IPR, 1.34; 95% CI, 1.24-1.46). Conclusion: Although only 10.5% of all injuries were recurrent, they more frequently resulted in missing >3 weeks of playing time and were more often managed surgically when compared with new injuries. The rate of recurrent injuries has not increased over the past decade.

Epidemiologic comparisons of soccer-related injuries presenting to emergency departments and reported within high school and collegiate settings

BackgroundFew studies compare sports injury patterns in different settings. This study described the epidemiology of soccer injuries presenting to emergency departments (EDs) and compared injuries presenting to EDs to injuries presenting to collegiate and high school athletic trainers (ATs).MethodsSoccer-related injuries (product code 1267) in the National Electronic Injury Surveillance System (NEISS) that were sustained by individuals at least two years of age in 2004–2013 were included. High School Reporting Information Online (HS RIO) data for high school soccer injuries during the 2005/06–2013/14 academic years were compared to NEISS data for those aged 14–17 years in 2005–2013. National Collegiate Athletic Association Injury Surveillance Program (NCAA-ISP) data for collegiate soccer injuries during the 2009/10–2013/14 academic years were compared to NEISS data for those aged 18–22 years in 2009–2013. All datasets included weights to calculate national estimates. Injury proportion ratios (IPRs) with 95% confidence intervals (CIs) compared nationally estimated injury distributions between the HS RIO/NCAA-ISP and NEISS data subsets.ResultsDuring the study period, 63,258 soccer-related injuries were captured by NEISS, which translates to an estimated 2,039,250 injuries seen at US EDs nationwide. Commonly injured body parts included the head/face (19.1%), ankle (17.6%), hand/wrist (15.3%), and knee (12.2%). Common diagnoses included sprains/strains (34.0%), fractures (22.2%), and contusions (17.7%). Compared to their respective age ranges in NEISS, sprains/strains comprised a larger proportion of injuries in HS RIO (48.3% vs. 33.7%; IPR = 1.38; 95% CI: 1.33, 1.42) and NCAA-ISP (51.3% vs. 37.0%; IPR = 1.39; 95% CI: 1.31, 1.46). In contrast, fractures comprised a smaller proportion of injuries in HS RIO than in NEISS (7.5% vs. 18.6%; IPR = 0.43; 95% CI: 0.39, 0.47) and NCAA-ISP (2.8% vs. 15.7%; IPR = 0.18; 95% CI: 0.14, 0.22).ConclusionsATs more commonly reported injuries that are easily diagnosed and treated (e.g., sprains/strains); EDs more commonly reported injuries with longer recovery times and rehabilitation (e.g., fractures). Although ED surveillance data can identify the most severe sports-related injuries, high school and college sports surveillance may better describe the breadth of sports-related injuries. Our findings may provide further support for school-based sports medicine professionals, but further research is needed to comprehensively examine the potential economic and health-related benefits.

Development of nap neurophysiology: preliminary insights into sleep regulation in early childhood.

Although all young children nap, the neurophysiological features and associated developmental trajectories of daytime sleep remain largely unknown. Longitudinal studies of napping physiology are fundamental to understanding sleep regulation during early childhood, a sensitive period in brain and behaviour development and a time when children transition from a biphasic to a monophasic sleep–wakefulness pattern. We investigated daytime sleep in eight healthy children with sleep electroencephalography (EEG) assessments at three longitudinal points: 2 years (2.5–3.0 years), 3 years (3.5–4.0 years) and 5 years (5.5–6.0 years). At each age, we measured nap EEG during three randomized conditions: after 4 h (morning nap), 7 h (afternoon nap) and 10 h (evening nap) duration of prior wakefulness. Developmental changes in sleep were most prevalent in the afternoon nap (e.g. decrease in sleep duration by 30 min from 2 to 3 years and by 20 min from 3 to 5 years). In contrast, nap sleep architecture (% of sleep stages) remained unchanged across age. Maturational changes in non‐rapid eye movement sleep EEG power were pronounced in the slow wave activity (SWA, 0.75–4.5 Hz), theta (4.75–7.75 Hz) and sigma (10–15 Hz) frequency ranges. These findings indicate that the primary marker of sleep depth, SWA, is less apparent in daytime naps as children mature. Moreover, our fundamental data provide insight into associations between sleep regulation and functional modifications in the central nervous system during early childhood.

Eye Injuries in High School and Collegiate Athletes

Background: Although eye injuries constitute a small percentage of high school and college sports injuries, they have the potential to be permanently debilitating. Hypothesis: Eye injury rates will vary by sport, sex, and between the high school and college age groups. Study Design: Descriptive epidemiology study. Level of Evidence: Level 3. Methods: Data from eye injury reports in high school and college athletes were obtained from the National High School Sports-Related Injury Surveillance System, High School Reporting Information Online (HS RIO) database over a 10-year span (2005-2006 through 2014-2015 school years) and the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP) over an 11-year span (2004-2005 through 2014-2015 school years). Injury rates per 100,000 athlete-exposures (AEs), injury rate ratios (RRs), and 95% CIs were calculated. Distributions of eye injuries by diagnosis, mechanism, time loss, and surgery needs were also examined. Results: A total of 237 and 273 eye injuries were reported in the HS RIO and the NCAA ISP databases, respectively. The sports with the highest eye injury rates (per 100,000 AEs) for combined high school and college athletes were women’s basketball (2.36), women’s field hockey (2.35), men’s basketball (2.31), and men’s wrestling (2.07). Overall eye injury rates at the high school and college levels were 0.68 and 1.84 per 100,000 AEs, respectively. Eye injury rates were higher in competition than practice in high school (RR, 3.47; 95% CI, 2.69-4.48) and college (RR, 3.13; 95% CI, 2.45-3.99). Most injuries were contusions (high school, 35.9%; college, 33.3%) and due to contact (high school, 89.9%; college, 86.4%). Only a small percentage of injuries resulted in time loss over 21 days (high school, 4.2%; college, 3.0%). Conclusion: Eye injury rates and patterns vary by sport, sex, and between the high school and college age groups. Although severe injuries do occur, most eye injuries sustained by high school and college athletes are minor, with limited time loss and full recovery. Clinical Relevance: Additional focus needs to be placed on preventing eye injuries at the collegiate level in women’s and men’s basketball, women’s field hockey, and men’s wrestling.

Head impact locations in US high school boys’ and girls’ soccer concussions, 2012/13-2015/16

This study describes concussions and concussion-related outcomes sustained by high school soccer players by head impact location, sex, and injury mechanism. Data were obtained for the 2012/13-2015/16 school years from the National High School Sports-Related Injury Surveillance System, High School RIO™. This Internet-based sports injury surveillance system captures data reported by athletic trainers from an annual average of 162 U.S. high schools. Data were analyzed to describe circumstances of soccer concussion (e.g., symptomology, symptom resolution, and return-to-play time) by impact location (i.e., front- [face included], back-, side-, and top-of-the-head) and sex. Most concussions were from front-of-the-head impacts (boys, 30.5%; girls, 34.0%). Overall, 4.1 ± 2.2 and 4.6 ± 2.3 symptoms were reported in boys and girls, respectively. In boys, symptom frequency was not associated with head impact location (p = 0.66); an association was found in girls (p = 0.02), with the highest symptom frequency reported in top-of-the-head impacts (5.4 ± 2.2). Head impact location was not associated with symptom resolution time (boys, p = 0.21; girls, p = 0.19) or return-to-play time (boys, p = 0.18; girls, p = 0.07). Heading was associated with 28.0% and 26.5% of concussions in boys and girls, respectively. Most player-player contact concussions during heading occurred from side-of-the-head impacts (boys, 49.4%; girls, 43.2%); most heading-related ball contact concussions occurred from front-of-the-head (boys, 41.4%; girls, 42.6%) and top-of-the-head (boys, 34.5%; girls, 36.9%) impacts. Head impact location was generally independent of symptom resolution time, return-to-play time, and recurrence among high school soccer concussions. However, impact location may be associated with reported symptom frequency. Further, many of these clinical concussion descriptors were associated with sex.

EPIDEMIOLOGY OF ROCK CLIMBING INJURIES TREATED IN UNITED STATES EMERGENCY DEPARTMENTS, 2006–2015

Background Rock climbing, an increasingly popular sport internationally, has become more accessible to broader populations with increasing numbers of climbing gyms and clubs. Even more participation should result from competitive climbings inclusion in the 2020 Tokyo Olympics. Describing injury patterns among broad populations of climbers is a first step in developing recommendations for increasing the safety of both recreational and competitive climbers. Objective Describe incidence, characteristics, and trends of rock climbing injuries presenting to United States (US) emergency departments (EDs) from 2006–2015. Design Retrospective descriptive epidemiology. Setting US EDs. Patients Patients presenting with climbing injuries. Assessment of Risk Factors Case reports were obtained from a large national hospital surveillance system that included sample weighting factors enabling calculation of national estimates. Main Outcome Measurements Injury incidence and characteristics. Results An estimated 39,285 climbing injuries were treated in US EDs from 2006–2015; incidence increased by 36% during that period. The majority of injured climbers were male (70.0%) and aged 20–39 years (57.5%). Ankles (21.7%) and lower legs (16.0%) were the most commonly injured body parts. Fractures (28.4%) and sprains/strains (27.3%) were the most common diagnoses. Most common mechanisms included falls (73.0%) and acute non-contact (13.0%). Overall, 12.1% of injuries treated in the ED resulted in hospitalization. Males (OR=1.91, 95% CI=1.11–3.30) and climbers who fell >20ft (OR=7.46, 95% CI=4.01–13.71) were more likely to be hospitalized than other injured climbers. Hospitalization was most frequent for fractures (66.6%) and head injuries (19.8%). Conclusions Climbing injury incidence increased over the past decade with young males most commonly injured. While lower limb injuries were the most commonly treated, head injuries accounted for nearly 20% of all hospitalizations. Such basic descriptive epidemiology studies characterizing injuries among broad populations of climbers can inform health care coverage decisions at competitions and drive future injury prevention efforts.

Epidemiology of knee internal derangement injuries in United States high school girls’ lacrosse, 2008/09-2016/17 academic years

ABSTRACT Research on knee internal derangement (KID) injuries in high school girls’ lacrosse is limited, yet needed to identify sport-specific risk factors. This study describes the epidemiology of KID injuries in United States high school girls’ lacrosse during the 2008/09–2016/17 academic years. Athletic trainers (ATs) reported injury and athlete-exposure (AE) data to the High School Reporting Information Online (RIO) surveillance system. KID injuries involved the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), lateral collateral ligament (LCL), and menisci. Injury rates per 10,000AE and injury rate ratios (IRR) with 95% confidence intervals (CI) were reported. Linear regression assessed injury rate time trends. ATs reported 148 KID injuries (rate = 1.92/10,000AE). The injury rate was higher in competition than practice (IRR = 8.40; 95%CI: 5.66–12.49). ACLs comprised a large proportion of KID injuries (46.6%). The ACL injury rate increased over time (P = 0.002), highlighting the need to develop/refine lacrosse-specific KID injury prevention programs.