Running injuries – what does the science say about preventing them?

Introduction

I recently met some fellow older runners at the Expo in the three days leading up to the Gold Coast Marathon. While standing on your feet for that long isn’t conducive to a fast half-marathon, the discussions did highlight to me how many runners carry injuries into events or get gut upsets in training and racing. I’ve thus decided to write two articles – one on gut upsets and how to avoid them and this one on what science says about preventing running injuries.

Here is a quote that says a lot in terms of how to prevent running injuries:

Running as an exercise can strengthen the limbs, develop the lungs, exercise the will and promote circulation of the blood. The clothing should be light, the head bare and the neck uncovered. Care must be taken not to overdo.(Scientific American, 1883)

Good advice from the past that still holds today I say! In terms of injury prevention, the last sentence summarises the current scientific evidence on how to prevent running injuries. Let’s now look at that research in some depth.

 Facts on running injuries

Research has shown that approximately 50% of runners experience injuries yearly with 25% of runners having an injury at any one time. While studies have shown wide variability in injury incidence of between 20-80%, there is conclusive evidence that:

  1. Higher running distances per week in male runners increases risk of injury
  2. A history of previous injury in the previous 12 months increases the risk of a new injury by 150%
  3. Increased training distance per week appears protective against knee injuries
  4. Distances greater than 40 miles (65 km) per week is the strongest risk factor almost tripling the risk of injury
  5. Daily running and the length of runs are also related to injury incidence

 The Risk Factors

There are many risk factors that are often implicated in running injuries. Let’s look at them in turn.

  • Anatomical Factors. Research has highlighted that the three major culprits are high-arched feet, leg length differences, and hip muscle weakness.
    • High arched feet have consistently been shown to produce higher landing impact forces and the foot to be more rigid during running. They have been consistently linked to greater risk of injury – particularly in front of knee pain, forefoot pain and recurrent stress fractures with 40% of runners with stress fractures having high arched feet. Interestingly, no research supports the use of orthotics or arch support to lessen injury risk.
    • Leg length differences have been implicated in hip, pelvis, iliotibial band syndrome (ITB), and lower back injuries in runners.
    • Hip muscle weakness is commonly linked to running injuries. In particular, hip abductor (muscles that take the legs outward to the side) and hip flexors (raise the thigh up when we run) weaknesses appear the culprits.

If you have any of these three risk factors, spend the time and money to see a sports physiotherapist or podiatrist with a running background for individualised assessment and treatment.

  • Eccentric Strength. Muscles can contract by shortening their length (concentric) or lengthening (eccentric). In running, most of the running muscles eccentrically contract as well as concentric. However the research strongly suggests the more forceful eccentric type contraction appears the culprit in running injuries. Thus, strengthening muscles eccentrically has been shown by research to benefit patellar (knee cap) and Achilles tendon injuries, front of knee pain, and hamstring injuries.  
  • Orthotics. These shoe inserts replace the removable insole found in all running shoes unless you are into the new age barefoot-type running shoes (more on those later!). Some are custom-built or off-the-shelf but all are aimed at correcting individual runner biomechanical issues, cushioning the foot, and/or prolonging how long it takes to fatigue the muscles. Recent research suggests these have a role in reducing stress fracture incidence, the symptoms of painful arches, and front of knee pain.
  • Running Shoes. While these vary in quality and type (cushioning and motion control), the consensus of research suggest that well-made and cushioned running shoes decrease the risk of injury. However, sports medicine professionals also strongly suggest that these shoes need to be fitted for both foot and running gait differences to reduce injury risk. For example, a motion control shoe is needed for overpronators (turning outward of the foot at the ankle on landing) or a cushion-type shoe for people with arch problems and supinators (turning inward of the foot at the ankle on landing). Barefoot running or use of Vibram shoes with little or no cushioning or motion control appears a fad at present. Yep, I’ve read the book too – a great yarn! It talks about native runners in the desert who run on sand or trails and have for centuries, not soft city slickers who run on concrete or asphalt! While the proponents say the shortened stride and lower-impact mid-foot or forefoot strike are proposed to reduce decrease injury risk, the other point of view is the increased risk of stress fractures when running on hard surfaces.
  • Running Surfaces. Running surfaces may be associated with injuries. Research has shown that females suffer more injuries when running on concrete or asphalt, but most studies have found no association of increased injury rates with harder surfaces, hilly terrain, running in the dark, or running speed.
  • Stretching. Two recent and systematic reviews of the literature examined the relationship between stretching and injury prevention in sport or sports performance in general. They concluded that there is no evidence to support stretching before or after exercise in preventing injury. However, there are a couple of studies that have specifically examined stretching in runners. They found a slightly lower injury rate in runners who stretched after running. Another study also found that stretching positively benefited runners with plantar fasciitis (sharp heel pain). I always stretch both before and after runs – my body is used to it and I rarely if ever suffer injuries. Research says stretches shorter than 10 seconds have no benefit and longer than 60 seconds no greater impact than stretches 10-60 seconds in length. More on the importance of flexibility for masters athletes in Chapter 9 of The Masters Athlete.
  • Warm-Up. Little research has examined the relationship between warm-up and injuries in runners. The limited research does suggest warming up decreases injury risk.
  • Psychological Factors. Interestingly, research suggests that associators (people who focus on their fatigue or injuries while running) have higher injury rates than dissociators (people who focus on their fatigue or injuries while running). Another study of 30 runners found that Type A personality (highly strung) have a much higher risk of multiple injuries than Type B personality (easy going) runners.
  • Training Errors. Excessive mileage (is there a work kilometerage?) is the BIGGEST and most common training error that leads to injury. Research suggests up to 60% of run injuries are due to training errors with over 50% of these due to excessive training distances. Importantly, research has shown that it’s the sudden change in routine (increase in intensity, change of terrain, increased frequency of running) or excessive distance explains up to 72% of injuries in runners. Another study showed running all year round increased risk. So what’s the optimal distance? Several studies have suggested that greater than 40 miles (65 km) per week leads to greater risk of injury in males with no studies having been done on females. Training studies done on runners has also shown that as frequency of running increased from one to three to five times per week, the rate of injury increased. Erratic training schedules such as greater than 10% increases in weekly distances, going straight into hill training, or starting interval training too quickly, also increases injury rates. For older runners, be wary of training with others who may be younger, fitter or faster. Getting sucked into ‘group think’ can lead to training errors and increased risk of injury. The above research suggests this may be a trap for you. Chapter 4 of the book The Masters Athlete has a whole chapter on the Principles of Training for Older Athletes. It details the smart way to train to prevent injury, stay well, and perform at your best.

 Conclusion

Excessive and rapid increases in running distance or intensity is a major risk factor in running injuries. Moderate risk factors appear to be previous injuries and high arched feet. Lower risk factors linked to run injury are leg length differences, poor quality running shoes, warm-up and stretching. However, it all boils down to training smart by being professionally examined by a sports physiotherapist or podiatrist,  progressively increasing your distance and intensity of training by a maximum of 10% per week, and wearing the right running shoe for your foot type, training terrain and running style. At the risk of pushing it, my book, The Masters Athlete, has a whole chapter on injury prevention and management for older athletes. If you liked this article, there is also an article on Shin Splint prevention on my website.

See you out there and keep exercising for life!

 Sources: Fields, K. and others. (2010). Prevention of running injuries. Current Sports Medicine Reports, 9(3): 176-182.

Van Gent, R. and others. (2007). Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. British Journal of Sports Medicine, 41: 469-480.