BCMJ, Vol. 44, No. 7, September 2002, page(s) 356-361—BC Centre for Disease Control
C.A.M. Johnston, MD, CCFP, Dip Sports Med & J.E. Taunton, MD, FACSM, Dip Sports Med & B. Zumbo, PhD & D.R. Lloyd-Smith, MDCM, Dip Sports Med & D.C. McKenzie, MD, PhD
Vancouver Sun Run: A study of the training habits and general health of its participants
This study of 717 runners indicates two surprising findings: greater distance run per week and less stretching are associated with fewer running injuries.
The Vancouver Sun Run is an annual 10 km running event. Of the 45080 entrants, 34430 people completed the event in 2001. The popularity of running is illustrated by the growth of this event, which began in 1985 with only several hundred participants. Research of running injuries has likewise increased, but few studies have been conducted on race participants.[1-3] Mass participation running events offer the benefit of studying all levels of runners.
The purpose of this study was to:
• Describe the training habits and general medical health of participants in a 10 km running event.
• Determine the incidence of injured runners, location of injuries, and factors predictive of injury.
A survey was designed to collect the data for this study. It was administered on the Internet and was a link from the event web site. Participants registered as part of a team or as individuals by the web site, mail, fax, or in person. Sun Run organizers provided access only to individual participants (approximately half of all runners). Awareness of the web site was achieved through local radio and television programs. Fliers with the survey web site were distributed at the sponsor’s fair organized for race package pickup in the 3 days prior to the run. Completed surveys were eligible for one of 25 prizes. Survey responses were collected 2 months prior to and 1 week following the Sun Run. Completed surveys totalled 717, and the responses were tabulated into the SPSS software package.
The questionnaire was divided into segments collecting information on:
• Past Sun Run participation and predicted race time.
• Training habits—shoe brand and their use in terms of kilometres and months, kilometres per week, kilometres and time per run, number of runs per week, months in current running program, total years running, stretching habits, training surfaces, competitive level, and cross-training habits.
• Health assessment—the presence of running injuries and medical conditions, as well as any medications or supplements taken.
• Demographics—age, gender, height, weight, marital status, education.
A running injury is present if the respondent agrees to one or more of the following statements:
• Experience symptoms (includes pain, stiffness, numbness, tingling, weakness) during or immediately after a run.
• Experience symptoms within the time span of starting a new run program.
• Reduce your mileage, stop running, or seek medical advice due to symptoms.
• Feel symptoms are related to running.
The response rate was estimated at 3% (717 responses out of 22,500 individual registrants).
There were 295 male respondents and their average age was 40.1 ± 12.4 years, height was 1.76 ± 0.8 m, and weight was 79.5 ± 12.4 kg. There were 418 female respondents and their average age was 36.2 ± 10.9 years, height was 1.63 ± 0.8 m, and weight was 63.0 ± 9.5 kg. The female to male ratio (60:40) was identical in both survey respondents and all Sun Run participants. An analysis of age ranges was similar between respondents and all Sun Run participants with the exception of fewer respondents aged less than 18 years and more respondents between the ages of 35 and 49 years. The education level of the study group and the total Sun Run population was also similar, with approximately 90% having post-secondary education.
A slight majority of respondents (58%, n = 412) were past Sun Run participants, with the number of past races ranging from 1 to 16. Of all Sun Run participants, 52% were first-time participants. Most past participants (79%, n = 325) have run four or fewer times. The survey sample is comprised of a greater percentage of runners who tend to be seeded or fast and a lesser percentage of walkers (<45 minutes = seeded, 46 to 55 = fast, 56 to 89 = not so fast, >90 = walker). Most (91%, n = 652) considered themselves “recreational.”
Asics, New Balance, and Nike brand running shoes (n = 468) constitute two-thirds of the shoes used for the Sun Run. Only one-quarter of runners (n = 542) have used their shoes for longer than 600 kilometres, beyond which it has been suggested there is increased loss of their shock-absorbing abilities.[4] Of note, 60% (n = 431) are unaware of their model. The majority of Sun Run participants run 5 km to 10 km per run (65%, n = 463), 30 minutes to 60 minutes per run (70%, n = 500), 3 to 4 times per week (62%, n = 443), and 5 km to 32 km per week (81%, n = 579). Information on all Sun Run participants indicates that a greater percentage train 3 or more days per week. Almost half (n = 342) reported not to have a weekly long run. Three-quarters (n = 505) have been involved in their current training program less than 5 months. Slightly more than half (61%, n = 437) have been running less than 5 years. Only 19% (n = 133) have a running career greater than 10 years. Most (89%, n = 637) report stretching “almost always” or “sometimes.” Runners who stretch before, during, and after a run are 67% (n = 482), 14% (n = 101), and 83% (n = 598) respectively. The most commonly used training surfaces (used “always” or “sometimes”) in order of preference are hard (95%, n = 676), uphill (78%, n = 558), soft (70%, n = 499), downhill (70%, n = 486), and track (30%, n = 212). The majority of Sun Run participants are involved in cross-training activities, with only 18% (n = 125) of participants involved almost exclusively in running. The specific cross-training activities are in Figure 1.
The majority of participants consider themselves in good (26%, n = 187), very good (40%, n = 287), or excellent (28%, n = 197) health. Further analysis of health can be achieved by looking at running injuries and general medical health of survey respondents. In the past year, 55% (n = 392) of survey respondents stated they had an injury, and of these individuals, 43% (n = 168) had an injury at the time of their response. Localization of the running injuries is shown in Figure 2. The knee is the most commonly injured area (n = 182) of the lower extremity. Shin (n = 98), foot (n = 83), thigh (n = 83), hip (n = 69), ankle (n = 68), and calf (n = 64) pains are reasonably similar in their frequency. The self-report nature of these injuries prevents defining the specific diagnoses. Medical illness and medication use are presented in Figure 3 and Figure 4. Respiratory (n = 62), endocrinology (n = 37), psychiatry (n = 35), cardiovascular (n = 33), and gastrointestinal (n = 28) systems are the most commonly affected on a self-report basis. However, vitamins and minerals (n = 143), and alternative medications (n = 60) are the most commonly consumed medications.
A binary logistic regression analysis was used to assess the contribution to running injury of the variables reported above in the results section. Kilometres per week (P = .023) and stretching (P = .013) are statistically significant and negatively related to running injury currently and in the past 12 months.
Our study population differs from those in other studies of race participants with respect to age, gender, running experience, and race distance. Our respondents are predominantly female and an average age of 40 years. The demographics of our respondents are likely influenced by the need for Internet access. Compared to all Sun Run participants, our sample has a much higher percentage of runners compared to walkers, and these runners tend to be older, faster, and more likely to be past participants of the Sun Run. This needs to be taken into consideration if one attempts to generalize the results of the survey sample to all Sun Run participants. These demographics are similar to last year’s Sun Run study (J.E.T., Ryan M.B., Clement D.B., D.C.M., unpublished data). Jacobs and Berson studied a group that is more representative of competitive 10 km runners.[1] They were younger and more experienced runners (competitions and years running) who ran faster, more often, and for a greater weekly distance. Only 20% were women. Kretsch and colleagues studied marathon participants who were younger and new to the marathon distance.[2] Women constituted 60% of this sample yet only 5% of the event. Marti and colleagues sampled exclusively male entrants of a 16 km race who were greater than 16 years old.[3] Similar to the subjects of Jacobs and Berson, subjects were younger, more experienced, and ran faster.[1]
Our goal was to sample as many runners as possible. The absolute number of responses and response rates of past surveys ranged from 451 to 4335 (average 1598) and 41.8% to 87.3% (average 70.9%). The previous Sun Run survey had more survey responses but no formal response rate. The increase in survey length from 1 to 4 pages may account for this decrease in survey response.
As a study population, race entrants are least likely to be injured as compared to study volunteers or running groups. Hoeberigs stated when calculating injury incidence, “methodological issues are at least as important as etiological factors.”[5] Four features that influence running injury incidence are:
• Definition of a runner.
• Definition of a running injury.
• Length of the study observation period.
• Presence of causative or protective factors to running injury.
Variation in any of these features can yield differing incidence rates.[5]
The definition of a runner has been standardized as entrants into a running event. Running injury has been defined by any restriction in running. In one instance, it was defined as inability to run for 1 week (J.E.T., Ryan M.B., Clement D.B., D.C.M., unpublished data). Marti and colleagues defined three grades of injury based on how training was affected.[3] Running injury incidence over 1 year was 29% to 46%.[2,3] The incidence over a 2-year period was 47% in the more competitive 10 km sample. This may have underestimated the real value since runners withdrawn from the race or currently injured were excluded.[1] The marathon group, in fact, had the lowest rate of injury and the most inclusive running injury definition of all these studies.[2] We have chosen a more inclusive definition without further stratification based on severity. It is not surprising that our study has the highest injury incidence.
The site of injury has remained consistent across all of these studies. The knee is the most common site of injury. Due to the self-report nature of our data collection, a medical diagnosis was not identified. A recent review of the running injuries at the Allan McGavin Sports Medicine Centre identified patellofemoral pain syndrome, iliotibial band friction syndrome, meniscus pathology, and patellar tendinopathy as being the most commonly diagnosed running-related knee injuries (C.A.M.J., J.E.T., D.R.L.-S., B.Z., unpublished data). Shin, calf, ankle, and foot pains are reasonably similar in their frequency.
Each of these studies has attempted to define factors predictive of running injury, but the results are quite variable. Data on the intrinsic causes of injury have not been collected in these studies. There are no significant differences between the training habits of injured and non-injured populations (J.E.T., Ryan M.B., Clement D.B., D.C.M., unpublished data). Self-reported causes of injury were listed. Kretsch and colleagues were not able to define any relationships between running injuries and training variables.[2] Jacobs and Berson identified the following as positively correlated with injury: miles per week, days running per week, pace, races per year, lack of participation in other sports, and marathon running.[1] A logistic regression analysis by Marti and colleagues yielded significant positive associations with weekly mileage, past injury, and the attitude “I train to compete.”[3] A dose-response effect of miles/week was not found.
Our analysis indicates the following:
• The more kilometres one runs per week, the less likely a running injury occurs.
• The less one stretches, the less likely a running injury occurs.
These results need to be interpreted with caution. With regard to the distance run per week, small subgroup numbers are in the two highest ranges of mileage per week. The stretching categories have less variation in category size. Despite a relatively large sample size, small subgroup numbers are present in some cases, and this can limit the ability of statistical tests to generate meaningful results.
Possible explanation for the association of increased distance and decreased presence of injury include a “healthy runner” effect, where injured individuals self-select themselves from running longer distances. Another hypothesis involves a musculoskeletal adaptation with increased running experience that reduces injury risk despite higher weekly running distances.[6]
A recent systematic review of randomized controlled trials of stretching in the prevention of lower limb soft-tissue running injuries identified two studies in which stretching occurred remote from the running session, and three studies in which runners stretched immediately before running. In only one study—in which stretches were conducted remote from the training for 30 seconds and a total of five sets—was there a reduced risk of injury. There was no suggestion that stretching increased injury. Different stretching protocols were used (range of one to five sets and stretches held for 10 to 30 seconds).[7] Shrier critically reviewed studies of stretching before exercise with a control group.[8] All studies involving a running population suggested that stretching did not prevent injury. It was even suggested there was a nonsignificant trend toward a higher injury rate in those who did stretch. A corresponding review of the basic science literature on stretching and skeletal muscle strain highlighted the following four possible reasons to explain this trend:
• An increase in compliance decreases the amount of energy that can be absorbed.
• Varying sarcomere lengths allow for injury during eccentric muscle contractions despite the fact that all sarcomeres are not stretched beyond their normal length.
• Mild stretching can cause damage at the cellular level.
• Stretching masks muscle pain.[8]
It has been postulated that the association between increased risk of running injury and stretching may be related to the observation that injured runners are normally counselled to stretch and have a higher risk of re-injury.[9]
Medical conditions in race participants have been studied only once before.[2] Most participants (84%) indicated no serious past medical history. The most common conditions included hypertension, asthma, and psychiatric disorders. Only 14% took any medications and they seemed to reflect the medical conditions indicated, including anti-inflammatories used for running injuries. In our study group, a greater number of organ systems are affected, though the more common conditions are similar. The exception is the increased frequency of thyroid and cholesterol conditions. Of the medications taken, 60% are vitamins, minerals, or alternative medications. The remainder reflect the medical conditions noted with the exception of the oral contraceptive pill and hormone replacement therapy. This is quite a significant difference in the medication profile as compared to the Kretsch and colleagues study.
Entrants in a local 10 km running event were surveyed regarding their training habits and general medical health, including running injuries. The study is unique in that it seems to be the first survey to be conducted entirely web-based. Our respondents are predominantly female of an older average age compared to previous studies. There is a high injury rate, though the injury definition is the most inclusive of those in the literature. The self-report system used and the absence of professional assessments has prevented learning the diagnosis and severity of these injuries. Predictive factors of running injury included less distance run per week and the use of stretching. This study highlights the breadth of medical systems affected in a cohort of runners. Vitamins, minerals, and alternative medications were more widely consumed than the traditional medications taken for conditions affecting the identified medical systems.
This study was supported by a grant from the Nike Research Foundation.
References
- 1. Jacobs SJ, Berson BL. Injuries to runners: A study of entrants to a 10000 meter race. Am J Sports Med 1986;14:151-155. PubMed Abstract
- 2. Kretsch A, Grogan R, Duras P, et al. 1980 Melbourne marathon study. Med J Aust 1984;141:809-814. PubMed Abstract
- 3. Marti B, Vader JP, Minder CE, et al. On the epidemiology of running injuries: The 1984 Bern Grand-Prix study. Am J Sports Med 1988;16:285-293. PubMed Abstract
- 4. Fredericson M. Common injuries in runners: Diagnosis, rehabilitation, prevention. Sports Med 1996;21:49-72. PubMed Abstract
- 5. Hoeberigs JH. Factors related to the incidence of running injuries: a review. Sports Med 1992;13:408-422. PubMed Abstract
- 6. van Mechelen W. Can running injuries be effectively prevented? Sports Med 1995;19:161-165. PubMed Citation
- 7. Yeung EW, Yeung SS. A systematic review of the intervention to prevent lower limb soft tissue running injuries. Br J Sports Med 2001;35:383-389. PubMed Abstract
- 8. Shrier I. Stretching before exercise does not reduce the risk of local muscle injury: A critical review of the clinical and basic science literature. Clinical J Sports Med 1999;9:221-227. PubMed Abstract
- 9. Brill PA, Macera CA. The influence of running patterns on running injuries. Sports Med 1995;20:365-368. PubMed Abstract
C.A.M. Johnston, MD, CCFP, Dip Sports Med, J.E. Taunton, MD, FACSM, Dip Sports Med, B. Zumbo, PhD, D.R. Lloyd-Smith, MDCM, Dip Sports Med, and D.C. McKenzie, MD, PhD
Dr Johnston is a recent graduate of the Allan McGavin Sports Medicine Centre Fellowship and UBC Family Practice Research Fellowship, and currently works at the Allan McGavin Sports Medicine Centre. Dr Taunton is a professor in the Division of Sports Medicine in UBC’s Department of Family Practice. Dr Zumbo is a professor of measurement, evaluation, and research methodology and an associate member of the Department of Statistics at UBC. Dr Lloyd-Smith is a physician at the UBC Student Health Service and the Allan McGavin Sports Medicine Centre. Dr McKenzie is a professor in the Division of Sports Medicine in UBC’s Department of Family Practice.
