A description of training characteristics and its association with previous musculoskeletal injuries in recreational runners: a cross-sectional study

Hespanhol Junior, Luiz C.; Costa, Leonardo O. P.; Carvalho, Aline C. A.; Lopes, Alexandre D.

doi:10.1590/S1413-35552012000100009

Abstracts

BACKGROUND: Running is one of the most popular physical activities in the world and the number of runners has increased over the past 40 years. One of the consequences of the growing running popularity is the increase of musculoskeletal injuries. OBJECTIVES: To describe the routines, training characteristics and history of injury in recreational runners and to evaluate possible associations between the routines and training characteristics with previous musculoskeletal running-related injuries. METHODS: A total of 200 runners participated in this study. The participants completed an electronic form containing questions about personal characteristics, running experience, training characteristics, type of running shoes, foot type and previous injuries history over the last 12 months. The data were analyzed descriptively as well as by using logistic regression models. RESULTS: The majority of the runners was male, aged 43.0 (SD=10.5) years-old, have a body mass index of 24.2 (IQR=4.3) kg/m², and had training volume of 35.0 (IQR=28.0) kilometers per week. Fifty-five percent of runners had injuries over the last 12 months. The most prevalent injuries observed were tendinopathies and muscle injuries. The variable that showed an association with previous running-related injuries was running experience from 5 to 15 years (Odds Ratio (OR)=0.2; 95%CI=0.1 to 0.9). CONCLUSIONS: The prevalence of running-related injuries over the last 12 months was 55%. The variable running experience was associated with the absence of previous musculoskeletal running-related injuries.

running; sports injuries; rehabilitation; physical therapy

CONTEXTUALIZAÇÃO: A corrida é uma das atividades físicas mais populares do mundo, sendo que o número de praticantes vem crescendo nos últimos 40 anos. Uma das consequências do aumento da popularidade da prática de corrida é o aumento das lesões musculoesqueléticas. OBJETIVOS: Descrever os hábitos, as características de treinamento e o histórico de lesões de corredores recreacionais, além de verificar possíveis associações entre os hábitos e as características de treinamento com lesões musculoesqueléticas prévias relacionadas à corrida. MÉTODOS: Duzentos corredores preencheram um formulário contendo questões sobre dados pessoais, histórico da prática de corrida, características do treinamento, tipo de tênis, tipo de pisada e histórico de lesões nos últimos 12 meses. Os dados foram analisados pela estatística descritiva e modelos de regressão logística. RESULTADOS: A maioria dos corredores eram homens, com idade média de 43 (DP=10,5) anos, índice de massa corporal de 24,2 (IQ=4,3) kg/m², volume de treino de 35 km semanais (IQ=28), e 55% dos corredores relataram apresentar alguma lesão musculoesquelética nos últimos 12 meses. As principais lesões encontradas foram as tendinopatias e as lesões musculares. A variável que apresentou associação com lesão musculoesquelética prévia relacionada à corrida foi a experiência de corrida entre cinco e 15 anos (Odds Ratio (OR)=0,2; IC95%=0,1 a 0,9). CONCLUSÕES: A prevalência de lesões musculoesqueléticas relacionadas à corrida nos últimos 12 meses foi de 55%, e a variável experiência de corrida foi associada com a ausência de lesões musculoesqueléticas prévias relacionadas à corrida.

corrida; lesões do esporte; reabilitação; fisioterapia

ORIGINAL ARTICLE

^IMasters Program in Physical Therapy, Universidade Cidade de São Paulo (UNICID), São Paulo, SP, Brazil

^IISão Paulo Running Injury Group (SPRunIG), São Paulo, SP, Brazil

^IIIMusculoskeletal Division, The George Institute for Global Health, Sydney, Australia

Correspondence to

ABSTRACT

BACKGROUND: Running is one of the most popular physical activities in the world and the number of runners has increased over the past 40 years. One of the consequences of the growing running popularity is the increase of musculoskeletal injuries.

OBJECTIVES: To describe the routines, training characteristics and history of injury in recreational runners and to evaluate possible associations between the routines and training characteristics with previous musculoskeletal running-related injuries.

METHODS: A total of 200 runners participated in this study. The participants completed an electronic form containing questions about personal characteristics, running experience, training characteristics, type of running shoes, foot type and previous injuries history over the last 12 months. The data were analyzed descriptively as well as by using logistic regression models.

RESULTS: The majority of the runners was male, aged 43.0 (SD=10.5) years-old, have a body mass index of 24.2 (IQR=4.3) kg/m², and had training volume of 35.0 (IQR=28.0) kilometers per week. Fifty-five percent of runners had injuries over the last 12 months. The most prevalent injuries observed were tendinopathies and muscle injuries. The variable that showed an association with previous running-related injuries was running experience from 5 to 15 years (Odds Ratio (OR)=0.2; 95%CI=0.1 to 0.9).

CONCLUSIONS: The prevalence of running-related injuries over the last 12 months was 55%. The variable running experience was associated with the absence of previous musculoskeletal running-related injuries.

Keywords: running; sports injuries; rehabilitation; physical therapy.

Introduction

Running is one of the most popular physical activities in the world¹ and the number of runners has considerably increased over the past 40 years. Many people who are looking for a healthier lifestyle, such as controlling the body-weight and improving the exercise capacity may choose running as an exercise modality, which is considered a physical activity of low cost and easy to perform.

One of the consequences of the growing popularity of running is the increase of musculoskeletal injuries among runners, which present incidence rates ranging from 19.4% to 92.4% depending on the target population and also on the definition of the term "musculoskeletal injury" used^2,3. Some studies were carried out aiming to identify possible risk factors for musculoskeletal injuries in runners, and the main factors observed in these studies were the training volume and the presence of previous injuries^1-11.

Many of these studies were conducted with marathon runners^{1,2,8,9,11,12} and also with samples aiming to participate in specific races, usually with lower training volumes (such as races from 4 to 16 km)^4,6,7,10. Two studies were carried out with amateur⁵ or recreational¹³ runners and only one study was conducted on elite runners, however these group of runners presented a weekly training volume (km) similar to the volume of training performed by marathoners¹⁴. Finally, only one study was conducted aiming to measure the association between musculoskeletal injuries and training characteristics in recreational runners without the intention to participate in any particular running race⁵.

It is important to conducted more studies with runners who perform lower training volumes compared with marathoners training and also who are not committed in participating in any specific race, since a large proportion of the runners only run recreationally, not exceeding few kilometers per training session. A better understanding of the profile of recreational runners and also which factors would be associated with musculoskeletal injuries in this population may help in the implementation of prevention strategies with a multidisciplinary approach, where the involvement of physical therapists, medical doctors, coaches and other health care professionals would allow possible effective actions to reduce musculoskeletal injuries on this enormous population of runners.

Therefore, the aims of this study were to describe the habits, the training characteristics and the history of injury in recreational runners. We also aim to investigate possible associations between the habits and the characteristics of training with previous musculoskeletal running-related injuries.

Methods

Study design and participants

This is a cross-sectional study with the participation of 200 runners who answered an electronic form containing questions about their habits, training characteristics and history of musculoskeletal running-related injuries. Participants aged over 18 years old and who have been running for at least six months were considered eligible for this study. Runners who were unable to run at the moment of data collection due to medical restrictions or presence of musculoskeletal injury (muscles, tendons, joints, ligaments and/or bones) were excluded from this study. This study was approved by the Ethics Committee of the Universidade Cidade de São Paulo (UNICID), São Paulo, SP, Brazil (number 13506607/2010) and has been conducted in partnership with CORPORE, an organizing company of running events of São Paulo, Brazil.

An invitation with information about the study was sent by e-mail to 4.000 of the 11.000 CORPORE runner's members and the consent form was attached as a link. After agreed to participate and answered the question confirming that they were musculoskeletal running-related injury free at that moment of the data collection, the participants completed a self-report electronic form (Appendix 1) which was composed by three sections: a) questions related to the participants characteristics such as age, weight, height, running experience, education level and lifestyle; b) questions about history of running (such as the number of running sessions per week, weekly training volume, time per kilometer, the practice of other sports, favorite running races and practice of flexibility exercises) and training characteristics (i.e. number of training sessions in each type of surface, monitoring of training, motivation for running, use of special insoles, running shoes type, number of pair of running shoes used and foot-strike type) and c) questions with regards to the history of musculoskeletal running-related injuries to determine the prevalence of injuries over the last 12 months (this information was collected through several options of symptoms or diagnoses derived from a previous study¹⁵). The definition of musculoskeletal running-related injury used in this study was based on previous studies that also aimed to investigate injuries in runners, being the definition: "any running-related musculoskeletal pain that have being severe enough to prevent the runner to perform at least one training session"^1,5,8,9.

Statistical analysis

The sample size calculation of this study was performed to detect an Odds Ratio (OR) of 1.4, with a statistical power of 80%, with a significance level of 95%, therefore of 200 runners were recruited. Descriptive statistics were calculated to present the characteristics of the participants. The comparison of continuous variables between the runners with and without history of musculoskeletal injury was calculated by using independent samples Student t tests. Mann-Whitney tests were used for non-parametric data and Chi-square tests were used for categorical variables.

Univariate logistic regression analysis was performed to test a possible association between the variables of participants' characteristics, history of running practice and training characteristics and previous musculoskeletal running-related injuries. Variables independently associated with previous musculoskeletal running-related injuries and presented a p<0.20¹ were considered to be included in the multivariate logistic regression model using the Backward Wald method. The coefficient of determination R² described by Nagelkerke was calculated in order to verify the prediction quality of the logistic regression model. The results were presented as OR and their respective 95% confidence intervals. All analyses were performed using SPSS 17.0 for Windows.

Results

The description of the participants characteristics was divided into two groups, being one group named as "with history of injury" and other "without history of injury", as it can be observed in Table 1. The prevalence of musculoskeletal running-related injuries over the last 12 months was of 55% (n=110), and the main reported injuries were tendinopathies (17.3%, n=19) and muscle injuries (15.5%, n=17). Regarding the anatomical site, the most affected region was the knee, with 27.3% (n=30) of the injuries (Table 2).

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Most of the participants were male, and 60% (n=120) of the runners reported a Body Mass Index (BMI) that can be classified as healthy (i.e. lower than 25). Participants who reported to run in a pace between 3 and 6 minutes per kilometer represented 76.5% (n=153) of the sample. Among these runners, 64.2% (n=129) informed that the training session had a mean duration between 60 and 90 minutes. Half of participants classified themselves as non-novice runners, as they have already previous experience with running training and most of the runners reported the use of running shoes with special characteristics "to control" their foot-strike type (neutral, hyperpronated or subpronated). Table 3 describes in greater details the categorized participants information.

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From all variables analyzed, nine presented a p<0.20 on the univariate logistic regression analysis, being age, BMI, running experience, hard surface type (such as asphalt and concrete), practice of other sports, the duration of other sports practice, weekly frequency of other sports practice, the use of running shoes with special characteristics and the knowledge of the foot-strike type (Table 3). All these nine variables mentioned above were included in the multivariate logistic regression analysis. From those, only one variable remained in the final model (running experience between 5 and 15 years) (Table 4). This proposed model explains 7% of the total variance.

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Discussion

Runners' description

The aims of this study were to describe the habits, training characteristics and history of injuries in recreational runners, as well as to evaluate the association of these characteristics with the presence of previous musculoskeletal running-related injuries. The greater majority of runners were men, with mean age of 40 years, BMI classified as healthy, with a mean running experience of approximately five years, four training sessions a week and with a weekly training volume of 35 km. These runners frequently ran on hard surfaces and reported the 10 km running as their favorite race. The prevalence of musculoskeletal running-related injuries over the last 12 months was 55% (n=110). The main reported injuries were tendinopathies and muscle injuries and the knee was the most affected anatomic site. Of all the obtained information from the athletes, the only characteristic that showed association with previous musculoskeletal running-related injuries was running experience.

The proportion of men/women participants of this study, their age, BMI, their running experience and the number of training sessions per week observed were similar to the ones observed in other studies that also analyzed runners^8,11,16, and only one study showed a higher proportion of women¹⁷.

The training volume of the runners from our study was lower in comparison with the distances observed in most of other studies^1,2,8,11. This results' discrepancy may be explained due to the fact of great part of these previous studies were conducted with marathoners^1,2,8,9,11, who usually need a higher weekly training volume. This characteristic observed in the present study makes it one of the first to approach different aspects related to running, using a population of runners who do not intend to run a marathon or a specific running race.

Stretching before and/or after a race/training sessions was frequent among the participants, which is similar to other studies^10,18. In spite of other studies on runners demonstrate that only a small portion performs such exercises^1,9,16. The fact that a high proportion of runners stretch before or after running may be related to fact that athletes and trainers believe that stretching could prevent injuries, in spite of the lack of scientific evidence that supports this belief^19-21.

Most of runners from this study reported to workout without any kind of professional monitoring (Table 3). A study suggests that a percentage about 40% of the runners has some kind of specialized orientation¹², data that is in agreement with our study.

Previous musculoskeletal running-related injuries and associations with training characteristics

The prevalence of musculoskeletal running-related injuries over the last 12 months was 55% (n=110). The most prevalent musculoskeletal injuries reported by the participants were tendinopathies and muscle injuries. In several studies, the patellofemoral syndrome^13,17,22 and tendinopathies^16,23-25 were among the most prevalent injuries in runners. The knee was the most affected anatomic site, as observed in previous studies^3,5,7,16,17. This high rate of knee injuries is usually due to the great magnitude of the impact forces present on the lower limbs while running, which may ranges from one and a half to three times of the body weight²⁶.

The multivariate logistic regression analysis showed that running experience from 5 to 15 years had an association with the absence of previous musculoskeletal running-related injuries (Table 4). Some studies indicated that inexperience in running practice may be a risk factor for new musculoskeletal injuries^2,4,9, in spite of a systematic review have pointed this finding as an uncertain evidence³. The association observed between running experience and history of musculoskeletal injuries may be explained by the fact that greater runner's experience, may promote better adaptation capacity to the musculoskeletal stress imposed by running²⁷. Another possible explanation is what the literature denominates as the "survival phenomenon", because the most experienced runners would be the ones who "survives" from injuries^2,9.

Our results may help runners and coaches to clarify some questions on running training characteristics. In addition physical therapists who are usually responsible for the implementation of injury prevention programs in running groups or teams can help with changing some training factors and, potentially, might reduce the incidence of musculoskeletal injuries in runners. The information of this study is also important for the runners who may be aware about their training routine, stimulating a safer practice. The identification of injuries in runners should also stimulates physical therapists to develop more effective treatment programs for this population with the aim of reducing the recovery time and promoting a return to running in a safer way.

Nowadays, several health professionals who work with running have suggested the use of flexibility exercises (stretching) and/or the prescription of special running shoes with the aim of preventing musculoskeletal injuries, in spite of the lack of evidence supporting their use^19-21,28. Longitudinal studies investigating the influence of these and of other training characteristics on the development of new musculoskeletal running-related injuries should be carry out. In addition randomized controlled trials should be encoureged to test the effectiveness of prevention programs and of rehabilitation protocols of musculoskeletal running-related injuries. Our research group is carrying out a prospective study with runners and the results of this study are likely to be published shortly.

Study limitations

This study had some limitations, such as a sample with a very high education level which might not be considered representative. In addition due to the cross-sectional design the associations observed in our study are only exploratory, not meaning that the associated variables are the cause of musculoskeletal running-related injuries. All data were collected using self-reported questionnaires, which could have influenced our results due to some sort of recall bias.

Conclusions

The prevalence of musculoskeletal running-related injuries over the last 12 months was 55%. The most frequent injuries reported by the runners of this study were tendinopathies and muscle injuries and the knee was the most affected anatomic site. Running experience between 5 and 15 years was associated with the absence of previous musculoskeletal running-related injuries.

Acknowledgments

CORPORE which helped us on the recruitment of the participants as well as on presenting our results to their members. We would also like to thank two physical therapists from the São Paulo Running Injury Group (SPRunIG), Bruno Tirotti Saragiotto e Tiê Parma Yamato, for their important help on this study.

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