The functional movement screen (FMS) is a screening tool for injury risk that assesses the movement patterns of individuals and evaluates mobility and stability comprehensively. The FMS consists of 7 component tests; each scored based on the movement patterns within the kinetic chain, asymmetries between the sides, and compensatory movements. The validity of the FMS as a predictor of injury risk has been confirmed in several studies (5,10,11,17). The study by Kiesel et al. (10) examined the relationship between the FMS and serious injury in professional football players. They revealed that professional football players with an FMS score of ≤14 were at a greater risk of serious injury than those with higher scores (10). Other studies reported similar findings in other groups, such as officer candidates (11,17) and female collegiate athletes (5).
Recently, 2 studies investigated normative values of FMS scores for runners. Loudon et al. (12) reported the normative value for running athletes and Agresta et al. (1) reported the value for healthy runners (the mean FMS composite scores were 13.1 ± 1.8 and 15.4 ± 2.4, respectively). Additionally, Agresta et al. (1) investigated the association between FMS scores and injury history. However, no prospective cohort studies have investigated the association between the FMS and running injuries. Running injuries are a serious problem for most runners, especially for competitive runners (8). Unfortunately, some runners are forced to retire from running because of serious running injuries. Previous studies reported some risk factors for running injuries, such as inadequate flexibility (24), muscle weakness and imbalance (16), and deficits in neuromuscular coordination (19). Cook et al. (6,7) stated that these factors also caused poor movement patterns, which were reflected in the lower score of the FMS. Thus, runners with low FMS scores might have certain risk factors for running injury and become more prone to injury. In addition, although Parchmann and McBride (18) reported that the FMS was not significantly associated with sprinting, Chapman et al. (4) revealed that a high FMS score had a positive effect on performance in elite track and field athletes in the long view. Because athletes with a higher FMS score rarely suffered from injury, they could practice continuously and improve their performance. Therefore, we hypothesized that the FMS could predict running injuries.
The receiver-operator characteristic (ROC) curve is a plot of the sensitivity vs. 1 − specificity of a screening test; this analysis is useful in determining the cutoff where the sensitivity and specificity are maximized. In previous studies, the ROC curve was used to determine the validity of the FMS as a predictor of injury risk (3,10,17). In addition, a cutoff value allows determining more easily whether a runner has a potential injury risk simply based on the FMS scores. Therefore, the aim of the current study was to determine the cutoff value and to investigate if the FMS score during preseason could be used to predict running injuries in young competitive runners during season.
Experimental Approach to the Problem
This study, using a prospective cohort design, investigated whether preseason FMS scores could predict serious running injuries during the season in 18- to 24-year-old competitive male runners. Figure 1 illustrates the process of this study in the form of a flow chart. The subjects performed the FMS at their college during preseason, February 2014. To minimize the influence of fatigue on performance, the FMS tests were conducted during the daytime on the day after a non-training day according to each team's schedule. No warm-up was included. The testing days added up to 7 days in total. After the FMS test, follow-up surveys were distributed to the subjects to investigate the incidence of running injuries during the 6-month season. The follow-up surveys were conducted twice at the end of May and August 2014 to reduce a recall bias. Statistical analyses were conducted using the data of the returned surveys. The ROC analysis determined the cutoff, and the logistic regression analysis determined if the FMS could be used for the prediction of running injuries.
A total of 84 competitive male runners volunteered to participate in the study (mean age = 20.0 ± 1.1 years, range = 18–24 years, height = 171.6 ± 4.5 cm, weight = 57.5 ± 4.3 kg). For inclusion, subjects had to be competitive male runners belonging to collegiate track and field teams, were injury free at the time of FMS test in preseason, whose events were middle or long distance, and whose running experience exceeded 1 year. The purpose and methods of this study were explained to the subjects in detail in a verbal statement, and written informed consent was obtained from the subjects. The current study did not include athletes under the age of 18 years; thus, parental or guardian consent was not needed. This study was approved by the Institutional Review Board of Kyoto University (Approval No. E2023).
Before the study, the physical therapists collecting data were instructed on the FMS evaluation method by an FMS specialist. The FMS scoring criteria were used as described by Cook et al. (6,7), and they discussed standardization of the testing.
On testing day, all subjects were questioned about their characteristics, such as age, height, weight, running experience, training sessions per week, weekly mileage, personal best time in their primary event in 2013, and injury history, by questionnaire. To allow comparison between different events, performances were normalized to a percentage of collegiate Japanese record performances (as of March 31, 2013) (4). To assess injury history, we asked the following question: “Have you ever suffered from musculoskeletal injury that was so severe that it required medical attention?” (5). Subsequently, all subjects were briefed on the FMS and were given a demonstration of the movements. After the demonstration, all subjects performed the FMS, which consisted of 7 movement tests to comprehensively assess mobility, stability, and coordination. The 7 tests were the deep squat (DS), hurdle step (HS), in-line lunge (ILL), shoulder mobility (SM), active straight leg raise (ASLR), trunk stability push-up (TSPU), and rotary stability (RS) tests. All tests were scored using standardized scoring criteria (6,7). Each movement test was scored on a 4-point scale (0–3), and the maximal FMS score that could be achieved was 21. A score of 3 was awarded for perfect form, a score of 2 was given for completing the test with compensations, a score of 1 was awarded for not completing the test accurately, and a score of 0 was given if the subjects felt any pain during the test. Each test was performed 3 times, and the highest score was used. Of the 7 tests that comprise the FMS, 5 tests (HS, ILL, SM, ASLR, and RS) were performed and scored separately for the right and left sides of the body. For these bilaterally assessed tests, the lower score was used.
After the FMS test, follow-up surveys were distributed to all subjects through each team's manager to investigate the incidence of running injuries during the 6-month season. If information was missing in the questionnaires, we asked the subjects to answer the omitted questions by contacting them through the team's managers. For the current study, the definition of running injury was a musculoskeletal injury that met the following criteria: (1) the injury occurred as a result of participating in a practice or race in track and field (trauma injuries, such as sprains, were excluded) and (2) the injury was sufficiently severe to prevent participation for at least 4 weeks; this definition was based on that used in previous studies (10,17).
Similar to a previous study (12), interrater reliability was assessed in a subgroup of 10 subjects by 2 physical therapists. Interrater reliability was calculated for the FMS composite score using the intraclass correlation coefficient (ICC, model 2, 1). On the basis of the reliability coefficients, the standard error of measurement
, the minimum difference to be considered real
, and the standard error of prediction
were calculated (23). The Bland-Altman analysis was performed to determine whether systematic error was present. The weighted kappa statistic was used to establish the interrater reliability for each movement test of the FMS.
We divided the subjects into 2 groups with and without running injuries according to the follow-up survey. Comparisons between the 2 groups were made using Student's t-tests (for parametric continuous variables), Mann-Whitney U-tests (for nonparametric continuous variables), or χ2 tests (for categorical variables). The short version of the FMS was calculated from the movement tests that were significant according to the U-tests. The ROC curve was calculated by pairing the FMS score with running injury to determine the cutoff on the FMS that maximized sensitivity and specificity according to previous studies (3,5,10,17). In this context, the FMS can be thought of as a screening test that determines if a runner is at risk for a running injury. An ROC curve is a plot of the sensitivity (true positive) vs. 1 − specificity (false positive) of a screening test. The area under the curve (AUC) was calculated based on the ROC curve. The optimal cutoff was determined based on the Youden index, which consists of the following formula: Youden index = (sensitivity + specificity) − 1 (2). Maximizing this index allows finding the optimal cutoff value. Once the cutoff value was identified, a 2 × 2 contingency table was created dichotomizing those with and without injury and those above and below the cutoff on the FMS. To determine whether a runner, whose FMS score was below the cutoff, had potential injury risk during season, the multivariate logistic analysis was adjusted for each subject's characteristics, including age, height, weight, running experience, training sessions per week, weekly mileage, performance level, and injury history. A value of p ≤ 0.05 was considered to be statistically significant for all analyses. All data were analyzed using the Statistical Package for the Social Sciences version 20.0 (SPSS, Inc., Chicago, IL, USA).
In preseason, 101 runners from 7 teams participated in the FMS, of which 84 returned for the follow-up surveys (response rate was 83.2%).
Interrater reliability for the FMS composite score is shown in Table 1. The ICC (2, 1) was 0.98 (95% confidence interval [CI] = 0.93–1.00), demonstrating excellent reliability, and the Bland-Altman analysis revealed that there was no systematic error present (both fixed bias and proportional bias). Interrater reliability (weighted kappa) for each component movement test is presented in Table 2 and shows that the majority of the FMS tests demonstrated a substantial to excellent agreement. These results were in accordance with the previous studies (9,15,21) and confirmed the reliability of the procedure in the current study.
Functional Movement Screen Score Distribution
The mean FMS composite score was 14.2 ± 2.3 with a range of 7–18. Of the 84 subjects, 43 (51.2%) scored ≤14 on the FMS composite score, indicating that they had a high injury risk according to Kiesel et al. (10). Among all the subjects, 4 reported pain in the DS and TSPU tests, 3 reported pain in the SM test, 2 reported pain in the ILL test, and 1 in the HS and RS tests, which resulted in a score of 0 for these tests.
The distribution of scores for each component movement test is presented in Figure 2. The SM test was the movement with the highest frequency of a score of 3 (65.5%). Conversely, the RS was the movement with the highest frequency of a score of 1 (34.5%); no subject achieved a score of 3 on this test. The DS, HS, ILL, and ASLR tests had the highest frequency of a score of 2 on each test.
Functional Movement Screen Score and Injuries
Among the 84 subjects, 15 (17.9%) experienced running injuries during the season. The comparisons between groups with and without running injuries are presented in Table 3. The mean FMS composite scores were 13.3 ± 2.7 and 14.4 ± 2.2 for subjects with and without any injury, respectively. Although there was a trend for the injury group to have a lower score, this difference was not significant (p = 0.07). Of the 7 tests, the scores on the DS and ASLR tests were significant with the U-test. Using the composite score of the 2 tests, we calculated a short version of the FMS, which was named “DS and ASLR” (score range: 0–6). Figure 3 shows the significant difference in the DS and ASLR score between the injured and the noninjured groups, whose scores were 2.9 ± 1.0 and 4.1 ± 1.1, respectively (p < 0.01).
The ROC curves for the FMS composite and DS and ASLR scores are presented in Figure 4. The cutoff of the FMS composite score was determined to be 14/15, which was consistent with a previous study (10). However, the ROC curve had a relatively low AUC (AUC = 0.65, p = 0.08), and at this point, the sensitivity was 0.73 and the specificity was 0.46. Subjects were dichotomized into groups with FMS composite scores ≤14 and ≥15, which are presented in Table 4. Conversely, the ROC curve for the DS and ASLR score had a relatively high AUC (AUC = 0.79, p = 0.01), and it determined the cutoff to be 3/4 with a sensitivity of 0.73 and a specificity of 0.74 (Figure 4). Subjects were again dichotomized into groups with DS and ASLR scores ≤3 and ≥4, which are presented in Table 5. Among the subjects with a score of ≤3, 11 out of 29 had been injured during the season (injury rate: 37.9%), whereas among the subjects with a score of ≥4, 4 out of 55 (injury rate: 7.3%) had been injured. The logistic regression analysis revealed similar results presented in Table 6. A score of ≤14 of the composite FMS did not significantly influence the incidence of running injuries (odds ratio [OR] = 3.0, 95% CI = 0.8–11.6, p = 0.10). However, the same analysis revealed that a runner with a DS and ASLR score of ≤3 was significantly more likely to become injured even when adjusting for each subject's characteristics (OR = 9.7, 95% CI = 2.1–44.4, p < 0.01).
The purpose of the current study was to investigate whether the FMS could predict running injuries in competitive male runners. The study revealed that the cutoff on the FMS was 14/15, which was in accordance with a previous study (10), but the composite score of ≤14 had low predictability for running injuries. In contrast, the current study also revealed that a DS and ASLR score of ≤3 during preseason was a more useful approach for predicting running injuries during season in 18- to 24-year-old competitive male runners. This is the first study to investigate the validity of the FMS as a predictor for running injuries and to establish the short version of the FMS (DS and ASLR) for screening running injuries.
The mean FMS composite score for the 18- to 24-year-old competitive male runners in the current study was 14.1 ± 2.3, which is similar to the results of college basketball, volleyball, and soccer athletes in the studies by Warren et al. (22) and Chorba et al. (5) (mean scores were 14.3 ± 2.5 and 14.3 ± 1.7, respectively). However, Loudon et al. (12) reported a mean score of 15.0 ± 2.4 for male running athletes, whereas Agresta et al. (1) reported a mean score of 13.1 ± 1.7 for healthy male runners. Although their findings slightly differ from ours, the runners in the current study had a comparable average performance as other runners. Additionally, our scores were relatively lower than the mean composite scores for professional football players (10) and officer candidates (17) (mean scores were 16.9 ± 3.0 and 16.6 ± 1.7, respectively). These differences are expected to occur because distance running mainly requires cardiorespiratory endurance and does not involve as much stability and power as required by football players or officer candidates.
Considering each movement test of the FMS, Figure 2 shows that the subjects performed the best on the SM test, which required mobility of the shoulder and scapula and thoracic spine extension. Because runners need to swing their arms frequently during running, SM is needed to minimize the burden from arm swing. However, the subjects performed the worst in the RS test, which requires multiplane trunk stability during a combined upper and lower extremity motion. This result was similar to the results of previous studies (1,17,20); there were only a few subjects who scored 3 on the RS test. Thus, these findings suggest that the RS test may be one of the more difficult tests of the FMS.
The ROC analysis revealed that sensitivity and specificity were 0.73 and 0.74, respectively. Subsequently, the multivariate logistic regression analysis revealed that subjects with a score of ≤3 on the DS and ASLR were approximately 10 times more likely to have running injuries than those with a score ≥4 after adjusting for each subject's characteristics. The relatively strong predictability of running injuries according to the DS and ASLR score was attributed to the following reasons. First, the DS test by itself had a strong predictability of injuries, which was in accordance with the result of the study by Butler et al. (3). The DS test assesses bilateral symmetrical mobility, especially mobility of hips, ankles, and thoracic spine, and coordination in the close kinetic chain. Renström (19) reported that poor flexibility and deficit in neuromuscular coordination can cause running injuries. Additionally, excessive pronation and knee-in during testing, which were the causes that decreased the score on the DS test (6), were also reported to be risk factors for injury (14). Second, the ASLR test was also found to be related to running injuries; it assesses active hamstring and gastric-soleus flexibility while maintaining a stable pelvis. This finding agreed with the study by Yagi et al. (24), who also reported that limited SLR ability increased the injury risk in high school runners. Additionally, Lysholm and Wiklander (13) reported that flexibility of the hamstrings was a risk factor for injury. Consequently, deficits in the DS and ASLR tests are likely to induce asymmetric or compensatory movement patterns and thus result in running injuries. Thus, the FMS contains both helpful and less helpful movement tests for predicting injury risk in competitive male runners. The HS test assesses stepping ability, which requires mobility and stability of the legs and also coordination. The ILL test requires mobility and stability in the split stance and also coordination. Although these 2 tests seem to be relevant for running, they were not significantly associated with incidence of running injury because most subjects received a score of 2 (91.7% for HS, 86.9% for ILL). Because of their ceiling effects, these 2 tests were ineffective in screening injury risk. As a result, the FMS composite score had low predictability. For the SM, TSPU, and RS tests, there is no solid evidence that SM and core stability influence the incidence of running injuries.
There were several limitations in the study. The first is the definition of injury as a running injury (lost training time ≥ 4 weeks). Although the current study revealed that the DS and ASLR could predict serious running injuries, it is unclear if it could successfully screen the risk of nonserious running injuries (lost training time < 4 weeks). A second limitation was the mode of collecting injury data by a self-report questionnaire because of the absence of athletic trainers in all teams. As a result, relevant details, such as type of injury, were not collected. A third limitation was that the study was carried out among 18- to 24-year-old competitive male runners in Japan. It is unclear whether the results can be extrapolated to other running populations, such as female, older, or recreational runners. Therefore, further study is required to ensure the external validity of the DS and ASLR score for other runners.
First, the study provided reliable normative data for FMS scores among 18- to 24-year-old competitive male runners. These data can be used as reference values for strength and conditioning by professional coaches when they need to assess the injury risk of similar groups using the FMS.
Additionally, the study revealed that a score of ≥4 or ≤3 of the DS and ASLR was more useful for predicting running injuries than the FMS composite score in the 18- to 24-year-old competitive male runners. This finding is meaningful for the strength and conditioning professional who supports a similar group of athletes. First, injury risks can be screened easily by using the DS and ASLR as it only takes approximately 5 minutes. This is an advantage because time is often limited and rather spent on training. Second, it allows the strength and conditioning professional to prevent serious problems in younger runners that could result in retiring from running because of injuries. Timely prediction of injury risks allows initiating strategies for preventing injury. For example, performing hamstring and gastric-soleus stretches are effective in improving scores on the ASLR (7). As to the DS test, the strength and conditioning professional or physical therapist should assess which deficit is limiting influence on this test before conducting corrective exercises. This is because the DS test is affected by many variables, such as the mobility of the hip, ankle, thoracic spine, and shoulder, the stability of the hip, and coordination (7). The current study suggests that, by improving scores on the DS and ASLR in preseason, the incidence of running injuries in 18- to 24-year-old competitive male runners could be reduced.
Special thanks to all the participants who willingly participated in this study.
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Keywords:Copyright © 2015 by the National Strength & Conditioning Association.
distance runner; screening; dynamic assessment; risk factor