Basis for article: The 10% rule is commonly used as a guideline for maximum training progression by runners, coaches, and clinicians, but needs to be further investigated due to a lack of supporting evidence. The overarching question that researchers sought to answer was:
“Is it hazardous to progress by more than 30% over a 2-week period?”
The Danish Novice Running Project was a prospective, observational cohort study involving 933 novice runners (464 females, 469 males) in which their run training was objectively monitored with GPS watches for 1-year. 873 participants completed the study. Each participant was provided a pair of adidas neutral running shoes and a garmin GPS watch. All run programs were self-structured based on each participant’s desire to train.
A running-related injury was defined as “any MSK complaint of the lower extremity or back caused by running that restricted the amount of running (distance, duration, pace, or frequency) for at least 1 week.”
- Participant was then examined within 1-week by a physiotherapist
- Injuries were diagnosed based on clinical examination and diagnostic imaging if necessary (25% of cases). The injuries were categorized as either overuse or traumatic.
Calculation of training volume and change over time:
- Cumulative distance was calculated over a 6-day period prior the completion of every training session (week 1)
- Cumulative distance was calculated from days 7 – 13 prior to the training session (week 0)
- The progression, maintenance, or regression was determined through the following calculation:
- (Total running distance week 1/total running distance week 0) x 100
- Ex. (11 miles/10 miles) x 100 = 110% = 10% total increase in volume from week 0 to week 1
Categorization into the following exposure groups:
- Regression or < 10% progression
- 10 – 30% progression
- > 30% progression
Cox regression models were used to identify cause-specific hazards of the injury risk for a specific injury category
Participants ran a total of 148,491 km over 35,410 training sessions
202 of the 873 runners sustained an injury
- 76 distance-related injuries: patellofemoral pain, IT band syndrome, medial tibial stress syndrome, patellar tendinopathy, glute medius injury, TFL injury, trochanteric bursitis
- 58 pace-related injuries: plantar fasciitis, achilles tendinopathy, tibial stress fracture, hamstring injuries, iliopsoas injuries, and triceps surae injuries
- 52 injuries classified as “other overuse injuries”: medial meniscus tears, stress fractures, and other overuse injuries (not classified as distance
- 16 traumatic injuries: inversion ankle sprains (only injury mentioned)
No significant differences in patient sex, age, body fat%, or BMI between injured and non-injured participants.
Results indicated that it was equally hazardous to increase running distance < 10% and 10 – 30% per week. The highest injury rates were associated with the > 30% per week exposure group (only for the development of distance-related injuries, not pace-related)
Study limitations: No quantification of pace criteria for determination of the pace-related injuries, no classification of intensity ranges associated with injuries
Study strengths: Consistency/standardization of study equipment (shoes, GPS watches) and objective calculations of changes in running volume
Practical application: What stands out to me are the different types of injuries that occur with higher pace vs. higher volume training. Higher volume running led to fascial, tendinous, and muscular injuries to the small, supporting muscle groups of the knee and hip, while higher pace running led to fascial and tendinous conditions of the ankle and foot and injuries to larger muscle groups in the lower leg, thigh, and hip. This makes sense considering the higher amount of muscle fibers involved as running pace increases. In my clinical experience, injury severity increases with higher intensity exercise, as more muscular force development is required. While the < 10% per week and 10-30% per week exposure groups showed no significant difference in injury rates, the authors concluded that a training volume progression of < 10% per week is prudent. I agree with this based on my clinical experience, especially in people who are recovering from an overuse injury or have a history of injury. When recovering from an overuse injury, I typically recommend a training volume progression of 5-8% in a pain-free individual.