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. . . Published ahead of Print

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Copyright © 2016 American College of Sports Medicine

Influence of Step Rate on Shin Injury and Anterior Knee Painin High School Runners

Lace E. Luedke1,2

, Bryan C. Heiderscheit3, D. S. Blaise Williams

1,4, and Mitchell J. Rauh

5

1Rocky Mountain University of Health Professions, Provo, UT; 2Department of Kinesiology,University of Wisconsin – Oshkosh, Oshkosh, WI; 3Department of Orthopedics and

Rehabilitation, Department of Biomedical Engineering, University of Wisconsin, Madison, WI;4VCU RUN LAB, Virginia Commonwealth University, Richmond, VA; 5Physical Therapy

Program, San Diego State University, San Diego, CA

Accepted for Publication: 22 January 2016


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Copyright © 2016 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.

Influence of Step Rate on Shin Injury and Anterior Knee Pain

in High School Runners

Lace E. Luedke 1,2 , Bryan C. Heiderscheit 3, D. S. Blaise Williams 1,4 , and Mitchell J. Rauh 5

1Rocky Mountain University of Health Professions, Provo, UT; 2Department of Kinesiology,

University of Wisconsin – Oshkosh, Oshkosh, WI; 3Department of Orthopedics and

Rehabilitation, Department of Biomedical Engineering, University of Wisconsin, Madison, WI;

4VCU RUN LAB, Virginia Commonwealth University, Richmond, VA; 5Physical Therapy

Program, San Diego State University, San Diego, CA

Address correspondence:

Lace E. Luedke, 108B Albee Hall, University of Wisconsin-Oshkosh, 800 Algoma Boulevard,

Oshkosh, WI 54901-8630, Phone: (920) 636-6369 Fax: (920) 424-7447. Email:

[email protected]

There was no funding received for this project. The authors have no conflicts of interests to

disclose. The results of the present study do not constitute endorsement by ACSM.

Medicine & Science in Sports & Exercise, Publish Ahead of PrintDOI: 10.1249/MSS.0000000000000890


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ABSTRACT

Purpose: High school cross country runners have a high incidence of injury, particularly at the

shin and knee. An increased step rate during running has been shown to reduce impact forces and

loading of the lower extremity joints. The purpose of this prospective study was to examine step

rate as a risk factor for injury occurrence.

Materials/Methods: Running step rates of 68 healthy high school cross country runners (47

females; 21 males; mean age 16.2±1.3 yrs) were assessed at a fixed speed (3.3±0.0 m/s) and self-

selected speed (mean 3.8 0.5 m/s). Runners were prospectively followed during the

interscholastic season to determine athletic exposures, occurrences of shin injury and anterior

knee pain, and days lost to injury.

Results: During the season, 19.1% of runners experienced a shin injury and 4.4% experienced

anterior knee pain. Most injuries (63.6%) were classified as minor (1-7 days lost). At the fixed

speed, runners in the lowest tertile of step rate ( 164 steps/min) were more likely (OR=6.67;

95% CI, 1.2-36.7; p=0.03) to experience a shin injury compared to runners in the highest tertile

( 174 steps/min). Similarly, for self-selected speed, runners in the lowest tertile ( 166

steps/min) (OR=5.85; 95% CI, 1.1-32.1; p


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110% of their preferred step rate, 45 healthy male and female runners were able to decrease the

mechanical energy absorbed at the hip and knee (16). A 15% increase from preferred step rate

reduced vertical impact peak and instantaneous and average loading rates in 10 male runners

(17). The shorter step lengths associated with higher step rates at a given speed reduce tibial

shock attenuation (22).

Mechanisms for step rate’s influence on A KP may be related to lower extremity joint

loading and kinematics. Peak patellofemoral joint force is often increased in individuals with

PFPS (11); however, a 10% increase in running step rate reduces peak patellofemoral joint force

and stress by 14% (19, 20). This effect is due in part to the heel landing closer to the body’scenter of mass when step rate is increased (16). Peak hip adduction, which has been

prospectively associated with risk of AKP (25), has been shown to decrease when step rate is

increased by 10% (16).

While the use of step rate manipulation is promising for the treatment of injured runners

(2, 37), there is limited information on whether step rate has value as a screening tool to identify

those at greater risk for sustaining a lower extremity injury (32). Thus, the purpose of this study

was to examine step rate as a risk factor for the occurrence of shin injury and AKP. We

hypothesized that runners with a lower step rate would have a higher incidence of shin injury or

AKP.


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METHODS

Subjects . Sixty-eight high school cross country runners (47 females and 21 males; age =

16.2 ± 1.3, mass = 59.6 ± 9.0 kg, height = 168.1 ± 8.7 cm) were prospectively followed during

an interscholastic season. Members of one northeastern Wisconsin high school ’s boys’ and girls’

cross country teams without a current running-related injury were recruited for the study. The

study protocol was approved by the Rocky Mountain University of Health Professions

Institutional Review Board. All subjects provided informed consent and guardian/parental

consent when required.

An a priori power analysis was performed. Based on prior studies of injuries among crosscountry runners, we expected that 48-60% of the injuries would be shin- and knee-related (27,

30). There has been little reported on the distribution of step rate in a running population. Thus,

using conservative estimated distributions (26, 28), we hypothesized that those in the low step

rate (high risk) group would have twice the risk or incidence of shin injury or AKP than those in

the high step rate (low risk) referent group (29). Using an alpha value of 0.05, power of 0.80, a

conservative expected relative risk of 2.0, a sample of 121 runners was estimated to show a

statistically significant relationship between step rate and shin injury or AKP (21, 26-30).

Classification of injuries. Runners were tracked during the interscholastic season to

identify occurrences of shin injury and AKP, and days lost to any injury. Prior to the season,

team coaches and athletic trainers were instructed in the use of the Daily Injury Report for

tracking AEs and days lost to injury (31). AEs are a total of all attended practices during the

season. If an athlete skipped a day of practice or missed a day due to illness or schedule conflict,

that day was not counted as an AE nor as a day missed to injury. An injury was defined as a

medical problem resulting from athletic participation that required a runner to be removed from a


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practice or competitive event or to miss a subsequent practice or competitive event (30). Runners

able to return to full, unrestricted participation prior to the end of practice or meet were not

considered injured in this study (30). Coaches and athletic trainers recorded absences or

limitations due to injuries and the injury site (30). Injury severity was based on days lost and

classified as mild (1-7 days lost), moderate (8-21 days lost), or major ( 22 days lost) (29).

If a runner reported shin or knee pain, a licensed physical therapist or licensed athletic

trainer examined the athlete to determine whether criteria were met for shin injury [ 1) continuous

or intermittent pain in the tibial region, 2) exacerbated with repetitive weight-bearing activity,

and 3) localized pain with palpation along the tibia (26, 36)] or AKP [ 1) pain around the anterior

aspect of the knee, 2) insidious onset, and 3) no evidence of trauma (e.g., falls, twists) (38)].

Study protocol. Within the first 3 weeks of the season, after running an 800m warm-up

on an outdoor track, each subject ’s running step rate was assessed at a fixed speed of 3.3 m/s and

at self-selected speed (mean 3.8 0.5 m/s). For the fixed speed trial, runners performed a 400m

run at 3.3 m/s following a pacing runner traveling at the required speed. After 2 minutes rest, a

second 400m trial was performed at a self-selected speed corresponding to approximately 80%

of their 5-km race effort or a 15-point Borg Rating of Perceived Exertion scale score of 16 (1).

The self-selected speed trials were run individually to minimize the influence of other runners.

To minimize the inclusion of speed changes within the trials, subjects began running

approximately 10m before the start line and data collection began as they crossed the start line.

The average step rate during each of these runs was determined for each individual using a Polar

RCX5 wristwatch with S3+ Stride Sensor secured to the shoelaces (Polar Electro Inc., Lake

Success, NY.) The Polar S3+ Stride Sensor has been shown to accurately and reliably measure

step rate with a 1.4% error rate (2-3 steps/minute) (15).


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Subjects also ran in a 3.22 km (2-mile) cross country time trial during the first week of

the season as part of their normal team training plan. Their finish times were recorded for the

study to provide demographic information on running performance.

Questionnaire . Subjects completed a pre-season questionnaire that included: age, school

grade, sex, height, weight, and prior running injuries.

Data Analysis

Injury rates were calculated based on an injury to the shin or AKP, and injury severity.

The initial injury rate was defined as the number of initial injuries per 1,000 AEs, counting only

AEs up to the initial shin injury or AKP. An initial injury was defined as the athlete’s first injuryincident during the season (27, 30). The subsequent injury rate was defined as the number of shin

injuries or AKP cases occurring after the initial injury per 1,000 AEs, counting only athletic

exposures that occurred after the initial injury in the denominator. The total injury rate was

defined as the total number of shin injuries and AKP cases per 1,000 athletic exposures (30).

The likelihood of injury by step rate was analyzed by categorizing the 3.3 m/s and self-

selected speed distributions into dichotomous (i.e. high/low) and tertile groups as there were no

known reported step rate thresholds available to categorize runners.

Univariate odds ratios (ORs) and 95% confidence intervals (CI) were calculated for shin

injuries and AKP based on step rate at 3.3 m/s and self-selected speeds. Separate univariate ORs

and 95% CIs were also calculated for female and male runners to allow for comparison to

previous studies reporting sex-specific data (27, 33).

For multivariable analyses, the measure of association was the adjusted OR estimated

from multivariable logistic regression analysis. For the overall sample, sex, prior injury, and

BMI were included in the final multiple logistic modeling due to their potential confounding


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effects. These factors have been previously associated with increased risk of running-related

injury (29, 35). An alpha level of 0.05 was used to determine statistical significance for all tests.

Epi Info (CDC, Atlanta, GA) was used for all incidence rate analyses, and SPSS Version 22.0

(SPSS Inc, Chicago, IL) was used for all other statistical analyses.

RESULTS

Baseline Characteristics. At baseline, although males were significantly taller (p0.05). Overall, 57.4% of runners reported a prior running injury (55.3%

of females and 61.9% of males.) No significant differences in step rate were found between

runners with and without prior running injury at 3.3 m/s (169.7 6.8 and 169.8 7.6 steps/min for

runners with and without prior running injury, respectively; p=0.95) or self-selected speeds

(171.7 9.0 and 170.6 7.4 steps/min for runners with and without prior running injury,

respectively; p=0.59).

Injury incidence. During the season, 19.1% of runners experienced a shin injury and

4.4% experienced AKP. Initial injury rates per 1000 AEs were 5.0 for shin injury (1.9 for

females and 12.1 for males) and 1.4 for AKP (1.3 for females and 1.5 for males) (Table 2).

While males had a higher likelihood of shin injury (OR=8.06; 95% CI 2.11-30.80) than females,

the rates for AKP were similar. Most shin and knee injuries (63.6%) experienced were classified

as minor (1-7 days lost) (Table 2).


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Step Rate and Injury. Runners in the lowest tertile for step rate at the fixed speed ( 164

steps/minute) were more likely (OR=6.67; 95% CI, 1.2-36.7; p=0.03) to experience a shin injury

compared to runners in the highest tertile ( 174 steps/minute). In our dichotomous analysis,

runners in the lower half of step rate values ( 170 compared to 171) at 3.3 m/s were more

likely to experience a shin injury (OR=5.3; 95% CI, 1.1-26.2) (Table 3). Likewise, at self-

selected speed, runners in the lowest tertile ( 166 steps/minute) (OR=5.85; 95% CI, 1.1-32.1;

p=0.04) were more likely to experience a shin injury compared to runners in the highest tertile

( 178 steps/minute). Runners in the lower half of step rate values at self-selected speed also had

a higher likelihood of shin injury ( 172 compared to 173) (OR=5.70; 95% CI, 1.2-28.2) (Table

4). No significant relationships were found between step rate and AKP at either speed.

For all runners, after adjusting for prior injury and BMI, a lower step rate was associated

with shin injury at 3.3 m/s ( 170 compared to 171, p=0.03; 164 compared to 174; p=0.03)

and self-selected speed ( 172 compared to 173, p=0.02; 166 compared to 178; p=0.04)

(Table 5). As we observed a sex-bias with shin injury, we then adjusted for sex in themultivariable logistic model. After controlling for sex, prior injury and BMI, shin injury was not

significantly associated with step rate at 3.3 m/s (p=0.26) or self-selected speed (p=0.06).

DISCUSSION

The primary purpose of this study was to examine whether step rate was associated with

shin injury or AKP among high school cross country runners. We evaluated this relationship by

assessing the runners ’ step rate at two different speeds while they ran over-ground and followed

them throughout the season to see who would incur an injury. Overall, our results suggest that

runners with lower step rate values at either speed were at higher likelihood of shin injury.


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We observed a higher incidence for shin injury and lower incidence of AKP than

previously reported. Rauh et al. reported rates of 3.6/1000 AEs for shin and 2.5/1000 AEs for

knee injury (30) while our rates were 6.8/1000 AEs and 1.1/1000 AEs for shin and knee injury,

respectively. Unlike their findings and others (26, 27, 30), we observed a higher rate of shin

injury among the males (15.7/1000 AEs) than females (2.7/1000 AEs) and equal rates of AKP in

males and females (1.1/1000 AEs). This is in contrast to prior prospective studies which reported

significantly higher rates of shin injuries in females (30) and a retrospective study noting slightly

higher rates for tibial injuries and patellofemoral pain in females (33). The higher rate of shin

injury for the males in our sample may be partially due to a higher percent of males in our studycompleting workouts at higher training loads and mileage than the females throughout the season

as most team practices were time- rather than distance-based.

To fulfill our sample size estimate, we made every effort to include all 154 cross country

runners from the participating high school. However, only 68 (44.2%) decided to volunteer for

the study. Despite the smaller sample size, e ven after controlling for BMI and prior injury,

runners in the lowest tertile for step rates at both fixed and self-selected speeds were found to be

at a higher likelihood of shin injury. Higher BMI values have been associated with shin injury

risk in high school cross country runners (26) and a history of prior injury has been linked with

higher risk of subsequent running injury (27). Our findings suggest step rate was not

significantly minimized as a result of prior injury. When we included sex in the modeling, the

associations with lower step rate were no longer statistically significant. However, this finding

may be more attributed to a small sample size studied where males were found to have a higher

incidence of shin injury. Prior studies of adolescent runners with larger sample sizes have


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consistently shown that females were more likely to incur shin injuries such as medial tibial

stress syndrome or other exercise-related leg pain (26, 27, 30).

Our finding that lower step rates were associated with shin injury might be partially

related to longer step lengths and higher shock attenuation. At a given velocity, step rate and step

length are inversely related; thus lower step rates coincide with longer step lengths. Edwards et

al. determined reducing stride length by 10% reduced peak tibial contact force and likelihood of

tibial stress fracture by 3-6% (9). Shock attenuation and energy absorbed at the tibia increased

during the impact phase of running when step length was increased (22) or stride rate decreased

(5). Increasing stride length by 30% resulted in a 43% increase in shock attenuation (22).In addition to shorter step lengths, higher running step rates are associated with decreased

ground reaction forces, impact shock, attenuation and loading (32). This may be a result of less

vertical displacement of the center of mass (10, 16), a more vertical leg posture at initial contact

(10) or a decreased angle of inclination, the angle between the foot and the ground. Decreasing

the angle of inclination may reduce or eliminate the distinct impact transient in vertical ground

reaction force at initial contact (16).

There were fewer cases of AKP than anticipated based on prior research. However, this

may be partially attributed to overall sample size studied. As only 3 runners experienced time

loss secondary to AKP, the study was not adequately powered to demonstrate a risk relationship

for step rate. At 3.3 m/s, all 3 cases were in the lower half of step rate values and 2 of the 3 were

in the lowest tertile at self-selected pace. As step rate modification is a successful adjunct to

treatment of runners with AKP (37), a larger prospective cohort sample is recommended as it

may help to appropriately examine this risk relationship based on kinematics and kinetics

associated with knee injury.


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Runners’ self-selected step rates and lengths appear to be based more on metabolic

efficiency rather than injury prevention (4). Adult runners’ preferred step rates minimized their

oxygen consumption but not their shock attenuation (14). Absorbing shock with active structures

like muscle has a higher metabolic cost than shock absorption by passive structures like

ligaments, articular cartilage, and bone (14). However, shock absorption via passive structures

likely increases injury risk as these structures can be overloaded (14). While small increases in

step rate to reduce joint loads may initially increase oxygen consumption or rating of perceived

exertion (4, 16), a recent study demonstrated recreational runners did not compromise their

running efficiency after 6 weeks of training with 5-10% increases in step rate (13).A major strength of this study was the use of a prospective design as it allowed the risk

profile of each runner to be established before the injury occurred, thus reducing the likelihood

of recall or measurement bias (27). In addition, to our knowledge, this was the first study to

examine step rate as a risk factor for running-related injuries in competitive adolescent runners.

Because of the study’s small sample size, the confidence intervals for odds ratios were fairly

wide. The relationship between step rate and could AKP not be examined adequately and further

analysis of this relationship needs to be studied in larger cohort studies.

While runners who increase their step rates from preferred values reduce impact forces

(5, 16, 17, 20, 32), there is limited evidence supporting ideal or abnormal step rate values with

respect to injury. Step rates around 180 steps/min are often recommended. For example, Chi

Running suggests 170-180 steps/min as part of their training recommendations while the Pose

Method advises step rates of 180 steps/min or greater (8, 12). However, this advice is not based

on injury incidence but more so on Daniels’ observations of 1984 Olympic distance runners (6).

While a target step rate of 180 steps/min may have merit for elite level distance runners during


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competition, the findings from our study suggest injury risk reduction may occur at step rates as

low as 171 steps/min.

Without established normative values or commonly used step rate thresholds for injury

risk , we grouped runners based on the sample population’s step rate distribution. In the

dichotomous groupings (i.e., 170 vs. 171; 172 vs. 173), runners in the low step rate group

had step rates below the mean, while those in the lowest step rate group for tertiles had step rates

less than 1 standard deviation below the mean of Heiderscheit et al. ’s sample (172.6 8.8 at their

self-selected speed of 2.9 0.5 m/s) (16). Heiderscheit et al. ’s population is used for comparison

as there are no known sources reporting step rate in high school runners and other studies

assessing the influence of step rate on running parameters used smaller samples of 4-10 runners

(32). Additional studies with larger samples sizes are recommended to further validate these step

rate cut points and their association with injury.

Some possible limitations with respect to data collection should be considered. The use of

a pacing runner during the 3.3 m/s condition may have influenced the high school runners’ step

rates. However, this would not have occurred during the self-selected runner speed condition, as

a pacer was not used. Also, w hile an individual’s leg length or height may influence self -selected

step rate, we did not attempt to scale step rate values based upon these anthropometric variables

as they have been found to explain less than 10% of the variance in stride length (step rate)

during running (3).

While a single variable like step rate may not explain the majority of the risk relationship

for a specific injury, it may be an important variable to consider as it can be easily assessed

outside of the laboratory. Biomechanics are considered a potentially modifiable intrinsic risk

factor for sports injuries in adolescents. While some reports suggest running technique is


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automatic or inherent, both healthy and injured adult runners have demonstrated the ability to

quickly make modifications to their running technique with various forms of gait retraining

including audio and visual cueing (13, 16, 37, 39). Any change to preferred running style

typically increases metabolic costs initially (4, 14), but oxygen consumption during an initial 6

minute bout of running at 110% of preferred step rate wasn’t significantly different than at the

preferred rate (14). This suggests there may be potential to modify self-selected step rate at

minor metabolic costs to reduce injury risk in a sport with high injury rates (9, 14, 22).

CONCLUSION

In the current prospective investigation, high school cross country runners with the

lowest step rates during running at both fixed and self-selected speeds were at a greater

likelihood of shin injury. Future studies are needed to determine whether step rate manipulation

may be incorporated for high school distance runners to reduce shin injury risk and time lost

during the cross country season.

Acknowledgements

There was no funding received for this project.

The authors would like to thank Lara Bleck, PT for her contribution to data collection.

The authors have no conflicts of interests to disclose.

The results of the present study do not constitute endorsement by ACSM.


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39. Willy RW, Buchenic L, Rogacki K, Ackerman J, Schmidt A, Willson JD. In-field gaitretraining and mobile monitoring to address running biomechanics associated with tibial

stress fracture. Scand. J. Med. Sci. Sports [Internet]. 2015. Available from:

http://www.ncbi.nlm.nih.gov/pubmed/25652871. doi:10.1111/sms.12413.

40. Zifchock RA, Davis I, Hamill J. Kinetic asymmetry in female runners with and without

retrospective tibial stress fractures. J. Biomech. 2006;39(15):2792-7.


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TABLE 1 – Baseline characteristics of high school cross country runners.

Total (n=68) Females(n=47)

Males(n=21)

p-value*

Variables Mean (SD) Mean (SD) Mean (SD)Age (y) 16.2 (1.3) 16.2 (1.3) 16.3 (1.5) 0.82Body mass (kg) 59.6 (9.0) 57.1 (7.5) 65.0 (9.8) 0.001Height (cm) 168.1 (8.7) 164.3 (6.3) 176.5 (7.1)


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TABLE 2 – Initial and subsequent anterior knee pain (AKP) and shin injury rates among highschool cross-country runners.

Total (n=68) Females (n=47) Males (n=21)

N AE Rate* N AE Rate* N AE Rate*

Initial injuryAKP 3 2218 1.4 2 1559 1.3 1 659 1.5Shin 11 2218 5.0 3 1559 1.9 8 659 12.1

Subsequent injuryAKP 0 557 0 0 322 0 0 235 0Shin 8 557 14.4 2 322 6.2 6 235 25.5

Subsequent injurySame body part 6 557 10.8 1 322 3.1 5 235 21.3

New body part 6 557 10.8 2 322 6.2 4 235 17.0

Total InjuriesAKP 3 2775 1.1 2 1881 1.1 1 894 1.1Shin 19 2775 6.8 5 1881 2.7 14 894 15.7

Injury severityMinor † 14 2775 5.0 4 1881 2.2 10 894 11.1Moderate ‡ 7 2775 2.5 3 1881 1.6 4 894 4.5Major# 1 2775 0.4 0 1881 0 1 894 1.1

N, Number of injuries; AE, Athletic Exposures.

*Rate per 1000 AEs.†Minor injuries (1 -7 days lost from running).‡Moderate injuries (8 -21 days lost from running).#Major injuries (22 or more days lost from running).


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TABLE 3 – Likelihood of injury and stride rate at 3.3 m/s among high school cross-country runners.

Total (N=68) Females (N=47) Males (N=21)

InjuryClassification

N %injured

OR (95%CI)

N %injured

OR (95%CI)

N %injured

OR (95%CI)

Shin Injury170

steps/min39 28.2 5.30 (1.1,

26.2)*20 10.0 1.40 (0.2,

10.8)19 47.4 0.00

171steps/min

29 6.9 1.00 Ref 27 7.4 1.00 Ref 2 0.0 1.00 Ref

Tertile 1( 164steps/min)

20 40.0 6.67 (1.2,36.7)*

9 11.1 1.1 (0.1,14.3)

11 63.6 0.00

Tertile 2(165-173steps/min)

26 11.5 1.30 (0.2,8.6)

18 5.6 0.5 (0.1,6.4)

8 25.0 0.00


22 9.1 1.00 Ref 20 10.0 1.00 Ref 2 0.0 1.00 Ref

Anterior KneePain

170steps/min

39 7.7 0.00 20 10.0 0.00 19 5.3 0.00

>171steps/min

29 0.0 1.00 Ref 27 0.0 1.00 Ref 2 0.0 1.00 Ref


20 5.0 0.00 9 11.1 0.00 11 0.0 0.00


26 7.7 0.00 18 5.6 0.00 8 12.5 0.00


22 0.0 1.00 Ref 20 0.0 1.00 Ref 2 0.0 1.00 Ref

N, Number at risk; OR, Odds Ratio; 95% CI, 95% Confidence interval; Ref, Reference group=highest step rate group.* p


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TABLE 4 – Likelihood of injury by step rate at self-selected speed (mean 3.8 m/s) among high schoolcross-country runners.

Total (N=68) Females (N=47) Males (N=21)Injury

Classification

N %

injured

OR 95%

CI

N %

injured

OR 95%

CI

N %

injured

OR 95%

CI

Shin injury172

steps/min38 28.9 5.70 (1.2,

28.2)*23 13.0 6.9 (0.6,

74.7)15 53.3 5.71 (0.5,

61.4)173

steps/min30 6.7 1.00 Ref 24 4.2 1.00 Ref 6 16.7 1.00 Ref


21 38.1 5.85 (1.1,32.1)*

11 9.1 1.60 (0.1,28.6)

10 70.0 7.00 (0.5,97.8)

Tertile 2(167-177

steps/min)

26 11.5 1.24 (0.2,8.2)

19 10.5 1.88 (0.2,22.8)

7 14.3 0.50 (0.1,11.1)


21 9.5 1.00 Ref 17 5.9 1.00 Ref 4 25.0 1.00 Ref

Anterior KneePain

172steps/min

38 5.3 1.61 (0.1,18.7)

23 8.7 5.70 (0.3,125.4)

15 0.0 0.00

173steps/min

30 3.3 1.00 Ref 24 0.0 1.00 Ref 6 16.7 1.00 Ref

Tertile 1

( 166steps/min)

21 9.5 2.11 (0.2,

25.2)

11 18.2 9.21 (0.4,

212.3)

10 0.0 0.00


26 0.0 0.00 19 0.0 0.00 7 0.0 0.00


21 4.8 1.00 Ref 17 0.0 1.00 Ref 4 25.0 1.00 Ref



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TABLE 5 – Adjusted models for the likelihood of shin injury by step rate at 3.3 m/s and step rate at self-selected speed(mean 3.8 m/s) among high school cross-country runners (N=68).

Adjusted Model A‡ Adjusted Model B †

Characteristic N % injured OR 95% CI N % injured OR 95% CI

Step rate at 3.3 m/s170 steps/min 39 28.2 5.90 (1.2, 30.2)* 39 28.2 2.85 (0.5, 17.6)171 steps/min 29 6.9 1.00 Ref 29 6.9 1.00 Ref

Tertile 1 ( 164 steps/min) 20 40.0 7.07 (1.2, 41.1)* 20 40.0 3.37 (0.5, 23.8)Tertile 2 (165-173 steps/min) 26 11.5 1.45 (0.2, 9.8) 26 11.5 0.89 (0.1, 7.1)Tertile 3 ( 174 steps/min) 22 36.4 1.00 Ref 22 36.4 1.00 Ref

Step rate at self-selected speed172 steps/min 38 28.9 7.2 (1.4, 38.6)* 38 28.9 5.53 (0.9, 32.0)173 steps/min 30 6.7 1.00 Ref 30 6.7 1.00 Ref

Tertile 1 ( 166 steps/min) 21 38.1 6.25 (1.1, 35.9)* 21 38.1 4.41 (0.7, 29.0)Tertile 2 (167-177 steps/min) 26 11.5 1.36 (0.2, 9.2) 26 11.5 1.27 (0.2, 9.9)Tertile 3 ( 178 steps/min) 21 9.5 1.00 Ref 21 9.5 1.00 Ref


Documents

2016. Influence Os Step Rate on Shin Injury and Anterior Knee Pain in High School Runners