Elsevier

Gait & Posture

Volume 38, Issue 4, September 2013, Pages 847-852
Gait & Posture

Differences in kinetic asymmetry between injured and noninjured novice runners: A prospective cohort study

https://doi.org/10.1016/j.gaitpost.2013.04.014Get rights and content

Highlights

  • Natural levels of asymmetry of kinetic factors in running were high.

  • Differences in asymmetry of impact peak and contact time were significant, but these variables did not remain significant in multifactorial analysis.

  • There were no differences in asymmetry of kinetic and spatio-temporal variables between injured and noninjured runners in this prospective study.

Abstract

Purpose

The purpose of this prospective study was to describe natural levels of asymmetry in running, compare levels of asymmetry between injured and noninjured novice runners and compare kinetic variables between the injured and noninjured lower limb within the novice runners with an injury.

Methods

At baseline vertical ground reaction forces and symmetry angles (SA) were assessed with an instrumented treadmill equipped with three force measuring transducers. Female participants ran at 8 and 9 km h−1 and male runners ran at 9 and 10 km h−1. Participants were novice female and male recreational runners and were followed during a 9-week running program.

Results

Two hundred and ten novice runners enrolled this study, 133 (63.3%) female and 77 (36.7%) male runners. Thirty-four runners reported an RRI. At baseline SA values varied widely for all spatio-temporal and kinetic variables. The inter-individual differences in SA were also high. No significant differences in SA were found between female and male runners running at 9 km h−1. In injured runners the SA of the impact peak was significantly lower compared to noninjured runners.

Conclusions

Natural levels of asymmetry in running were high. The SA of impact peak in injured runners was lower compared to noninjured runners and no differences were seen between the injured and noninjured lower limbs.

Introduction

Annually, 19–83% of all runners sustain a running-related injury (RRI) [1], [2]. Notwithstanding the high risk of sustaining an RRI, running is still one of the most popular physical activities. Injuries most common sustained among runners are medial tibial stress syndrome, patellofemoral pain syndrome, iliotibial band syndrome, stress fractures of the tibia, fibula or metatarsals, plantar fasciitis and Achilles tendinopathy [3]. Risk factors that put runners at higher risk for developing an RRI have been studied extensively [4], [5], [6]. Risk factors for RRIs can be divided into: training, anatomical and biomechanical factors [7]. Because of the high forces applied to the body with each foot strike, kinetic variables like impact peak [7], active peak, and loading rate, were often studied in relation to RRIs [7], [8], [9], [10], [11], [12]. Results from these often small and retrospective studies were contradictory. In a recent prospective study among 210 novice runners, no differences in kinetic peak values were found between runners who developed an RRI and runners who did not [13]. Therefore, magnitude of the impact and active peak forces might not be directly related to the development of an RRI.

Kinetic asymmetries between the left and right leg will expose one of the lower limbs to more stress than the other [14], [15]. Therefore, the musculoskeletal tissue of the leg that is exposed to higher levels of stress might be more susceptible to an overuse injury and it could be possible that reduced symmetry may result in RRIs. Only two studies examined this possible relation between kinetic asymmetry and RRIs [14], [15]. Both studies did not find differences in asymmetry between injured and noninjured runners. However, due to the retrospective character of both studies these findings might as well be the result of the injury. It can be argued that asymmetry is reduced as result of the injury, to decrease loading on the injured side. A prospective study can elucidate the possible causative nature of kinetic asymmetry on RRIs.

Studying the possible relation of kinetic asymmetry to RRIs is of importance for several reasons. Firstly runners at risk could be easily identified by measuring kinetic variables of both legs. Secondly, preventive measures such as the use of insoles or shoe modifications could be developed and introduced to reduce asymmetry in kinetic variables causative in the development of RRIs [16]. And thirdly, running technique could be modified in a way to reduce imbalances in load to the lower extremity and thereby decrease the risk on an RRI [17].

The purpose of this prospective study was threefold. First, describe natural levels of asymmetry. Second, compare levels of asymmetry between novice runners who sustained an RRI and novice runners who did not sustain an RRI. Third, compare kinetic variables between the injured and noninjured lower limb within the novice runners who sustained an RRI. It was hypothesized that runners who had higher levels of asymmetry in impact peak, active peak and loading rate were more likely to sustain an RRI on the side where loading was highest.

Section snippets

Methods

Novice runners between the 18 and 65 years old who had not sustained an injury of the lower extremity in the last 3 months before inclusion were recruited from the GRONORUN 2 study population [13]. The GRONORUN 2 study was a randomized control trial which studied the effect of a preconditioning program on the incidence of RRIs. An RRI was defined as any self-reported musculoskeletal complaint of the lower extremity or back causing a restriction of running for at least 1 week. After baseline

Results

Two hundred ten novice runners enrolled in the study, 133 (63.3%) female and 77 (36.7%) male runners. Mean age was 37.2 ± 11.2 years, body mass index (BMI) was 23.9 ± 3.4 kg m−2. Age (35.9 ± 10.7 versus 39.6 ± 11.4 years) and BMI (23.5 ± 3.5 versus 24.7 ± 3.1) in female runners were significantly lower compared to male runners. Leg length of female runners (0.91 ± 0.09) was significantly shorter than the male runners (0.96 ± 0.05). The incidence of an RRI during the 9-week running program was 16.2%. Twenty-three

Discussion

To our knowledge this is the first published prospective study in novice female and male runners that examined differences in symmetry of kinetic and spatio-temporal variables between injured and noninjured novice runners.

Conclusion

The current study showed that natural levels of symmetry at baseline were different per variable and also inter-individual differences were large. Significant differences were observed in the symmetry angles of the impact peak and contact time by direct comparison, however these relationships did not remain significant once other factors were accounted for in the regression analysis. The hypotheses that injured novice runners had higher levels of asymmetry in impact peak, active peak and

Conflict of interest

The authors declare that they have no conflict of interest.

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