Based on previous studies on RRIs among novice runners, an injury incidence of 20% is expected [7, 14, 18]. Taking into account a dropout rate of 20% [6, 7, 14, 18, 19], the inclusion of 6,000 participants will lead to approximately 4,800 participants at follow-up. With an RRI incidence of 20%, a total of 960 RRIs are expected. Taking into account the need of a minimum of 10 RRIs per risk factor analyzed in a multivariate model, this is sufficient for accounting for the multivariate nature of RRIs [15, 20].
The five-part baseline questionnaire will be administered online after participants give informed consent. Demographics, anthropometrics, and other personal characteristics are covered in part 1. Self-reported body height and weight will be used to calculate BMI (weight (kg) / height2 (m)).
Part 2 covers information on previous running and sports participation [21, 22]. Also information about previous injuries during running (“Have you ever had a running injury?”) and musculoskeletal complaints in other sports (“Have you ever had complaints in your bones, joints or muscles and tendons during sports and exercise?”) are obtained per anatomical site. Information on footwear and insoles is obtained in the second part as well.
Physical activity during daily life is assessed in part 3 with the Short Questionnaire to Assess Health-enhancing physical activity (SQUASH). The SQUASH was designed to give an indication of habitual activity level during an ordinary week. The SQUASH has been tested for validity and reliability with an accelerometer as a criterion measure in a general adult population and has turned out to be reliable and valid [23, 24].
In part 4, the Behavioral Regulation in Exercise Questionnaire-2 (BREQ-2) is used to measure motivation toward exercise in general. The BREQ-2 assesses a motivation and external, identified, interjected and intrinsic regulations, and showed sufficient validity in adults .
In the final part physical, mental and social health is measured. Perceived health is assessed with the Dutch version of the RAND-36 Health Survey (RAND-36), which was translated from the standardized SF-36 Health Survey [26, 27]. The RAND-36 is a validated and reliable measure . Mastery as part of mental health is measured using the 7-item scale of Pearlin and Schooler . Physical health is measured with a 5-item scale on high prevalent health complaints, and social health is measured with the shortened 6-item scale for loneliness [29, 30].
The runners starting with the STR program in March 2013 will receive four follow-up questionnaires at 6, 12, 26 and 52 weeks after beginning with the program. The group of runners who start in September will only receive three follow-up questionnaires at 6, 12 and 26 weeks. In the follow-up questionnaires continuation and reasons for discontinuation of running will be monitored. Participation in other sports will also be monitored in the follow-up questionnaires. Besides questions about continuation of running or other sport activities, all follow-up questionnaires also measure physical activity (SQUASH), motivation toward exercise (BREQ-2), and physical and mental health (RAND-36, 7-items scale of Pearlin and Schooler, 5-item scale on high prevalent health complaints, and shortened 6-item scale for loneliness).
Web-based training log during the 6-week STR program
During the 6-week STR program a weekly training log is sent to the participants. For each training session, data on running exposure (frequency and duration), running surface, perceived exertion and pain is registered. Weekly information on other sports activities (type of sports and exposure that week) is obtained from the training log. When participants do not enter their digital training log after five days, an e-mail reminder is sent automatically.
Perceived exertion will be assessed using Borg’s Ratings of Perceived Exertion (RPE) scale. The RPE scale is widely used in exercise science and sports medicine to monitor or prescribe levels of exercise intensity. Borg’s RPE scale has shown to be a valid measure of exercise intensity .
Pain will be measured by registering anatomical site of the body and severity of pain for each training session. A mannequin will be shown to identify the anatomical site of the running-related pain. By clicking on the anatomical site, the same spot will be pointed red. Severity of pain is additionally subdivided into pain without limitations, pain that causes a restriction in running, and pain which makes running impossible. To classify the severity of pain, a Visual Analog Scale (VAS) is used. When a training session is skipped, the reason for it will be asked (running-related pain, other pain, illness, motivation, or other reason). When running-related pain is the reason, anatomical site and severity of pain will be obtained.
In addition to the pain registration obtained for each training session, the development and progression of overuse injuries is also monitored with a new method as proposed by Clarsen et al. . This method is designed to monitor overuse problems for predefined anatomical locations separately. In the current study, however, this is not ideal because all injury locations are of interest. The proposed method has thus been modified: instead of monitoring pain for each predefined anatomical location, general data is collected and the specific anatomical location is asked for afterwards.
Web-based training log after the 6-week STR program
After the 6-week STR program, a digital training log is sent to the participants every two weeks. This training log is a simplified version of the log that was used during the first six weeks. Information on running exposure, running surface, running-related pain and other sports activities is registered per week instead of at each training session. In this simplified training log, pain registration and monitoring of overuse injuries is similar to the methods used in the first six weeks. Participants who quit running after the STR program can indicate so, and only have to complete the information on other sports activities.
Questionnaire for injured runners
When an RRI is registered in the web-based training log, a questionnaire will be automatically sent to the participant after two weeks. This questionnaire is used to specify medical/paramedical treatment, the order of treatments, type and frequency of the treatment, medical aids, and absence from work, school or training due to the RRI. Injured runners are asked to specify the injury location, if the injury is new or recurrent, what structure is injured (e.g. muscle, tendon, bone or ligament), and the injury mechanism (e.g. strain, sprain, rupture, dislocation, contusion, inflammation or overuse). When the runner is seen by a professional, a diagnosis will be asked. Until recovery from the RRI, every four weeks a follow-up questionnaire on medical/paramedical consumption and absence from work, school or training is sent to the injured runner.
To validate the RRI registration method that is used in this study, approximately 10% of the subjects who sustain an RRI will be contacted by a sports physician. The sports physician will perform a standard physical examination and will then complete the abovementioned RRI questionnaire regarding location, structure, and mechanism of the injury.
RRI cost analysis
From the data derived from the RRI questionnaire and subsequent follow-up questionnaires, direct and indirect costs will be calculated. Costs will also be calculated from a societal perspective. Direct healthcare costs will include costs resulting from medical/paramedical treatment and/or medical aids. Indirect costs will include costs resulting from absence from paid work or unpaid work, as well as leisure time lost. Dutch guideline prices will be used to value resource use . Direct costs of hospital treatment will be estimated on the basis of standard prices from the Health Care Insurance Board . The costs of medication and medical aids are estimated on the basis of prices recommended by the Royal Dutch Society of Pharmacy  and the Health Care Insurance Board [34, 36]. Costs of loss of productivity due to absenteeism from paid or unpaid work will also be included. Costs of absenteeism from paid work are estimated using the friction cost approach with a friction period of four months and based on the mean age- and sex-specific income of the Dutch population. . Costs of productivity loss attributable to unpaid work, such as study and household work, will be estimated at a shadow price of EUR 8.78/hour. All prices are standardized to the year 2012 and will be adjusted for inflation . Total costs will be estimated for each injured athlete by multiplying resource data by cost prices. Total, direct and indirect costs will be calculated by adding costs per category of utilization of healthcare resources.
Incidence of RRIs will be calculated for all participants and for male and female participants separately as the number of new injuries reported per 1000 hours of running exposure. Exposure time (in hours of running exposure) will be calculated from the time the participant started the running program until an RRI is reported (injured runners) or until the end of the program (non-injured runners).
Descriptive data will be presented as means (± s.d.) and frequency distributions.
For identification of risk factors for RRIs only data from the baseline questionnaire and the running log will be used. Data of the follow-up questionnaires will not be used for this purpose, because these data do not contribute to a pre-running risk-profile. It is possible for a single subject to sustain multiple RRIs during the study period. In this case only the occurrence of the first RRI will be used for analysis. Potential risk factors for RRI will be entered into a multivariate Cox regression prediction model. Hazard ratios and the corresponding 95% confidence intervals will be calculated for the factors associated with RRI.
Data of the baseline and follow-up questionnaires will be compared with a repeated-measures ANOVA to examine the health effects of participating in a supervised running program. Reasons for dropout from the start-to-run program will be described and determinants for dropout will be analyzed by multivariate logistic regression models. Course and medical consumption and the associated direct and indirect costs will be described for injured runners.
Missing data will be completed by multiple imputation using the Multiple Imputation by Chained Equations (MICE) procedure, a technique in which missing values are replaced based on estimated relations in the dataset . Ten multiple imputed datasets are generated, whereupon the results of those ten multiple imputed datasets will be combined using the rules given by Rubin .