Youth Distance Running and Lower Extremity Injury: A Systematic Review

istance running is a popular youth sport. This systematic review identi ed and examined the effects of youth distance running and lower extremity musculoskeletal injury. Scienti c databases were searched from database inception to May 2020. Two hundred and fty-eight full texts were screened, with nine articles retained for data extraction. Seven of the studies were case reports or case series. Two case reports involved an apophyseal hip fracture. No correlation was found between running mileage or gender and sustaining an injury. Middle school runners reported fewer injuries than high school runners. Cross country accounted for less than 10% of injuries in youth under 15 compared to other track activities. The main nding was a paucity of research. Available literature suggests youth can participate in distance running with minimal adverse effects. One exception may be increased vulnerability to growth plate injury. Additional research is needed, especially in those under 10, as literature in this population is nonexistent. Keywords:cross country; distance running; youth; adolescent; lower extremity injury 1. Introduction Distance running has become increasingly popular among youth athletes over the past decade.

youth can participate in distance running with minimal adverse effects. One exception may be increased vulnerability to growth plate injury. Additional research is needed, especially in those under 10, as literature in this population is nonexistent. Keywords:cross country; distance running; youth; adolescent; lower extremity injury 1. Introduction Distance running has become increasingly popular among youth athletes over the past decade. In 2007, an estimated 12 million children between ages 6 and 17 participated in running [1]. Distance running was the most common and second most common physical activity among girls and boys ages 12 to 15, respectively [2]. The participation of youth runners in long distance events has also progressed, with reports of youth marathon nishers as young as 7 years old [3] and 100-km ultramarathon nishers as young as 12 years old [4]. The increase of distance running can result in a surge of youth injuries, as one study demonstrated a 34% increase in running-related injury incidence in children six to 18 presenting to U.S. emergency departments from 1994 to 2007 [2]. Distance running-related injuries in the adult [5–8] and high school [9–12] populations are well researched, as opposed to injuries in youth runners, which led us to focus only on the middle school and younger population. Skeletally immature runners are different than adult counterparts as they may be more vulnerable to injuries involving the physis and muscular-tendon attachment sites [1,13]. Although there is insuf cient evidence on the effects of youth distance running, runners younger than 15 have completed marathons with few adverse outcomes. From 1982 to 2007, 310 youth runners, ages seven to 17, nished the Twin Cities Marathon with less injury incidence than adult nishers [3]. Youth runners had a medical encounter incidence of 12.9 of 1000 nishers, compared to 24.6 of 1000 nishers in adults [3]. Of the 310 youth runners, only four (1.29%) required medical attention, all mild in severity, and required no intervention besides a short period of rest [3]. Those four athletes were between the ages of 16–17 and no runners younger than 15 required medical assistance. Likewise, the Students Run LA

1000 nishers, compared to 24.6 of 1000 nishers in adults [3]. Of the 310 youth runners, only four (1.29%) required medical attention, all mild in severity, and required no intervention besides a short period of rest [3]. Those four athletes were between the ages of 16–17 and no runners younger than 15 required medical assistance. Likewise, the Students Run LA Program, from 1989–2018, had more than 63,000 youth runners, as young as 12 years old, complete a marathon with no reports of adverse outcomes [14]. However, a study of 225,344 children (ages 6–18) who presented Int. J. Environ. Res. Public Health2021,18, 7542.

Int. J. Environ. Res. Public Health2021,18, 7542 2 of 12 to U.S. emergency departments showed that the highest injury rate (45.8 per 100,000 US population) was in runners between ages 12 and 14 [2]. Controversy exists whether distance running is safe for youth runners. The rst statement on risks in distance running for youth was published in 1982 by the American Academy of Pediatrics (AAP), which disapproved long-distance running events for chil- dren prior to physical maturation [15]. The International Amateur Athletic Federation of England guidelines stated that intense training in children can cause physeal damage and unnecessary psychological stress [16]. The AAP statement was updated in 1990, recom- mending that until further data are available on the relative risk of endurance running, if children enjoy the activity and are asymptomatic, there is no reason to preclude them from training for and participating in endurance running events [17]. The latest updates, although based on expert opinion, recommend accounting for the maturity level of the runner [14]. Self-motivated youth runners should complete a supervised training program, remain pain and injury free, meet appropriate weight and height gains, and maintain adequate sleep and nutritional needs for the demands of a growing body [14]. To the best of our knowledge, there has been no systematic review to date published that has investigated the effects of distance running for those under the age of 15 and lower extremity musculoskeletal injury. Therefore, the purpose of this systematic review was to identify and examine all of the available literature speci c to lower extremity musculoskeletal injuries in youth runners under the age of 15. 2. Methods 2.1. Data Sources and Searches We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The study was registered in PROSPERO; registration number CRD42019136428. The search was conducted by a medical librarian in MEDLINE (via PubMed), EMBASE (via Elsevier), and Scopus (via Elsevier) using both keywords and sub- ject headings representing distance running, running injuries, and the pediatric population. Editorials, commentaries, and animal studies were excluded. The search covered the time frame from database inception through 7

was registered in PROSPERO; registration number CRD42019136428. The search was conducted by a medical librarian in MEDLINE (via PubMed), EMBASE (via Elsevier), and Scopus (via Elsevier) using both keywords and sub- ject headings representing distance running, running injuries, and the pediatric population. Editorials, commentaries, and animal studies were excluded. The search covered the time frame from database inception through 7 May 2020. Reproducible search strategies can be found in the Appendix. 2.2. Subjects Studies were eligible for inclusion if the following criteria were met: (1) participants were under 15 years of age, (2) the distance reported was at least 800 m, and (3) the athlete sustained an injury to the lower extremity from running. The exclusion criteria included: (1) sports that were not strictly running (i.e., soccer), and (2) study design that was an editorial, review article, conference report, or letter to the editors. 2.3. Operational De nitions Distance running: Our operational de nition for distance running was either described as cross country or a minimum of 800 m if the distance was speci ed. We chose 800 m as the minimum distance to be included in this review as this has been considered a distance when the body transitions from anaerobic to aerobic system utilization [18]. Furthermore, we wanted to include a distance that would be sensitive enough to yield the highest number of studies. Youth running: Our operational de nition of youth running was population under 15 years of age. Our focus was to maximize the potential to include runners of middle school age or younger and to exclude high school runners. 2.4. Study Selection Results from our search strategy were uploaded into Covidence (Veritas Health In- novation;), a systematic review software. Duplicate citations were automatically identi ed and removed by Covidence. Two reviewers (TP, RM) indepen-

Int. J. Environ. Res. Public Health2021,18, 7542 3 of 12 dently screened references by title and abstract. A third independent reviewer (CF) settled any disputes between reviewers. 2.5. Data Extraction Two independent reviewers (TP, RM) extracted the data from the included studies. The data extracted included the study design, participant demographics, total running mileage, and type of lower extremity injury sustained. 2.6. Quality Assessment Risk of bias was assessed using the Modi ed Downs and Black checklist [19] for non-case reports. The 26-item checklist consists of four subscales with the categories of reporting, external validity, internal validity (bias), and internal validity (confounding selection bias). Two reviewers (CF and YW) completed the checklist independently. A third reviewer (TP) settled disagreements between the two reviewers. 3. Results 3.1. Study Selection The search strategy (Appendix) resulted in 4384 articles. After duplicates were removed, there were a total of 2176 articles. Upon completion of the title and abstract screening, 258 articles were retained for full text screening. After full-text screening, eight articles were retained for data extraction. One additional article [20] was later identi ed through a hand search resulting in a total of nine articles that met eligibility criteria and were included in the qualitative analysis (Figure).Int. J. Environ. Res. Public Health 2021, 18, x 4 of 16 Figure 1. PRISMA Flow Diagram. 3.2. Study Characteristics Two of the nine articles included were cohort studies: a retrospective descriptive ep- idemiological study and an observational prospective cohort study. Table 1 includes data extracted from those two studies. Seven of the nine included articles were case reports or case series. Data extracted from those articles are included in Table 2. Figure 1.PRISMA Flow Diagram. 3.2. Study Characteristics Two of the nine articles included were cohort studies: a retrospective descriptive epidemiological study and an observational prospective cohort study. Table data extracted from those two studies. Seven of the nine included articles were case reports or case series. Data extracted from those articles are included in Table.

studies: a retrospective descriptive epidemiological study and an observational prospective cohort study. Table data extracted from those two studies. Seven of the nine included articles were case reports or case series. Data extracted from those articles are included in Table.

Int. J. Environ. Res. Public Health2021,18, 7542 4 of 12 Table 1.Quantitative Study Characteristics. Author, Year, Design Population (Sample Size, Age) Running Exposure Outcome Downs and Black Risk of Bias Cohort Studies Goldman et al., 2020 Observational Prospective Cohort Study 720 MS participants (7th and 8th graders) in SRLA marathon training program 28-week marathon training program 3 weekday training runs 1 long weekend run Began with 2-mile runs and increased to a maximum 20-mile run prior to marathon Week 5: 5K Week 14: half-marathon Week 9 and 17–20: school holiday closures Mean distance per week: 9.87–22.82 m Injury sites across all runners Knee (33%) Lower leg (19%) Foot (14%) Ankle (13%) Thigh (6%) Hip (6%) 102 reported MS injuries HS runners more likely to report an injury than MS runners (p< 0.001) 20.8% of HS runners reported injuries versus 14.2% of MS runners (p< 0.001) MS runners who sustained an injury ran signi cantly greater distance on average per week than non-injured MS runners (14.1 mi vs. 11.5 mi,p< 0.001) 15 Reid et al., 2012 Retrospective Epidemiological Study National Estimates *: Age 10–12: 25,243 injuries (95% CI: 20,125–30,362) Age 13–14: 53,504 injuries (95% CI: 43,286–63,722) Cross country events 10–12 year-olds: Estimated 1234 (4.9%) injuries 13–14 year-olds: Estimated 4964 (9.3%) injuries Most frequently injured body part across all runners: Lower extremities (58.2%) Upper extremities (19.0%) Trunk (13.8%) 17 MS: Middle School; SRLA: Students Run Los Angeles; HS: High School * N was national estimates based on weighted data for 4496 actual cases from the National Electronic Injury Surveillance System of the US Consumer Product Safety Commission.

Int. J. Environ. Res. Public Health2021,18, 7542 5 of 12 Table 2.Case Report Characteristics. Author, Year Population Running Exposure Symptoms Outcome Case Reports Clancy et al., 1976 1 out of the 13 cases reported was a 14-year-old male cross-country runner Cross country running One-month history of gradual onset of pain around right anterior iliac crest Experienced pain when running and coughing or sneezing Fracture separation of the anterior portion of right anterior iliac apophysis Localized tenderness over right anterior iliac crest. This pain was reproduced with resisted abduction of affected hip. Complete relief of symptoms and full return to running after four weeks of rest Daffner et al., 1982 1 of the 4 cases reported was an 11-year-old male runner Running 2–3 m per day One-month history of pain and localized swelling in the proximal right tibia Pain with direct pressure to proximal tibia, running and walking Right tibial stress fracture Mild swelling over proximal medial tibia 8 cm distal to joint line and radiograph con rmed circumferential area of periosteal new bone, thickened posteriorly Discharged on minimal activity and improved rapidly Dull, 2000 14-year-old female competitive cross-country athlete Running 20 to 30 miles per week including up and down hill running exercises Bilateral hip pain localized to ASIS, anterior thigh and low back. Pain was greater on the left. Hill running seemed to exacerbate her pain more than any other activity. Initially tried conservative treatment and returned to a moderate running regimen, ve days later pain intensi ed with sharp grabbing sensations in the anterior thigh and pelvis Bilateral avulsion fractures of the pelvis apophyses Apophyseal separation fracture of the left anterior superior iliac crest Seven months after returning to activity following left apophyseal separation fracture, experienced avulsion fracture to right anterior superior iliac crest Training was ceased for a short period of time, and she returned to a successful running regimen within 12 weeks Gamble, 1986 13-year-old female competitive athlete Running, placed rst in her age bracket in a 10 km race prior to onset of symptoms Two-month history of increasing pain and swelling of right knee One-month

to right anterior superior iliac crest Training was ceased for a short period of time, and she returned to a successful running regimen within 12 weeks Gamble, 1986 13-year-old female competitive athlete Running, placed rst in her age bracket in a 10 km race prior to onset of symptoms Two-month history of increasing pain and swelling of right knee One-month prior to presentation experienced sensation of the knee giving way while trying to accelerate while running Tender to palpation of patella and discomfort with patellar compression and maximal quadriceps contraction Symptomatic dorsal defect of the right patella Excisional biopsy was performed. Four months after surgery, she had full range of motion and no symptoms.

Int. J. Environ. Res. Public Health2021,18, 7542 6 of 12 Table 2.Cont. Author, Year Population Running Exposure Symptoms Outcome Case Reports Nishio et al., 2012 14-year-old male member of track athletics club Running more than 10 km daily One-month history of progressively worsening pain in medial aspect of the left thigh Pain was initially experienced only after running but progressed to also occur with weightbearing activities Adductor insertion avulsion syndrome CT: presence of periosteal reaction and intracortical linear hypoattenuation and showed no fracture line MRI: periosteal, cortical, and intramedullary signal intensity abnormalities Treated with initial avoidance of weight bearing using crutches for ambulation, followed by progressive weight bearing for two weeks. Symptoms resolved completely seven weeks after initial evaluation and he had normal gait without pain. At three months returned to gradual running program. Ross et al., 2008 14-year-old male cross-country runner Cross country training, began training 2 months prior to presentation Three to four weeks into training developed pain in left distal thigh. Soon after also began to experience right thigh pain. Bilateral supracondylar stress fracture Decreased activity to pain-free levels with acetaminophen for pain. At one-month follow-up he was pain free and allowed to gradually return to running. Sakamoto et al., 2008 12-year-old male member of a track athletics club Running more than 5 km a day Seven-week history of discomfort in distal left thigh when running Symptoms were gradually worsening, with discomfort increasing to pain four weeks prior to presentation Tenderness over distal thigh and increased pain with weightbearing Pathological insuf ciency fracture associated with nonossifying broma in the distal femur CT: showed radiolucent cortical lesion seen on plain radiographs as a well-de ned area of decreased density in the cortex, consistent with a diagnosis of NOF, with periosteal new bone Initial avoidance of weightbearing using two crutches for ambulation, followed by progressive weightbearing over ve weeks. Three months after onset, he had normal gait without pain and returned to running. ASIS: anterior superior iliac spine; Km: kilometers; CT: computed tomography; MRI: magnetic resonance imaging; NOF: nonossifying broma.

with periosteal new bone Initial avoidance of weightbearing using two crutches for ambulation, followed by progressive weightbearing over ve weeks. Three months after onset, he had normal gait without pain and returned to running. ASIS: anterior superior iliac spine; Km: kilometers; CT: computed tomography; MRI: magnetic resonance imaging; NOF: nonossifying broma.

The review explores the relationship between youth distance running and lower extremity injuries.