How Much Should You Run? – Part 3: Injury
Running injuries seem to be a fact of life. It seems that it’s not a matter of if you are going to get injured, but when you are going to get injured.
Why does running produce so many injuries and what do running injuries have to do with training volume?
These are the questions we will answer this time around.
“Law 3: Each Injury Indicates a Breakdown” 1
“The key to comprehending an inappropriate overuse injury risk is to realize that this implies excessive tissue stress over time without adequate recovery.”2
The first thing to realize about injuries is that they are caused by placing repetitive stress, or loads, on the body greater than the body can handle. The second quote really sums it up well. You typically don’t get injured from just one run. You get injured when the body is not allowed sufficient time to recover between runs.
“High training volumes and previous injury are two of the most important predictors of injury (Powell et al. 1986; Marti, Vader, et al 1988; Brill and Macera 1995; Van Mechelen 1992).” 3
“When researchers at the University of South Carolina studied 583 veteran runners recently, they found that the most important predictor for injuries was total mileage. Those who ran 40 miles a week or more were more likely to get hurt. This doesn’t mean you should never do more than 40 miles a week in your training…However, the research does suggest that, over the long haul, more quality miles may be the way to go…Mike Keohane, who competed in the 1992 U.S. Olympic Trials Marathon and is now a New York City-based running coach, says his ideal training week would look like this: A long run, a tempo run, and a hilly run.”4
Note that the South Carolina study was conducted on veteran runners, not beginners or sedentary subjects. This is important because it clearly indicates the injury rate for experienced runners in similar to that observed in beginner runners. Runners are frequently told that with proper training and time that they can safely and successfully increase their weekly mileage. This study clearly indicates otherwise.
“Training intensity was between 85 and 90 percent of maximum heart rate and involved workouts 3 days/week for 15, 30, or 45-min duration (for the first group)… and for 30-min 1, 3, or 5 days/week (for the second group)…Injury occurred in 22%, 24% and 54% of the 15, 30, and 45-min duration groups and in 0%, 12%, and 39% of the 1, 3, and 5-day/week groups, respectively.”5
Note that running 30 minutes 3 days/week resulted in an injury rate of 12% – 24%. Running 30 minutes 5 days/week resulted in an injury rate of 39%. Running 5 days a week for 45 minutes each time resulted in an injury rate of 54%. This study does a great job of illustrating the increasing risk of injury associated with increasing training volumes. Each increase in training volume results in an increase in rate of injury. This study didn’t continue beyond 5 days of training but we can extrapolate what the injury rate would be for additional days of running.
In order to determine what training factors are associated with running-related injuries, researchers asked a random sample of entrants to a 10K race to complete a questionnaire. 47% of the of the respondents indicated they had sustained a running-related injury in the previous 2 years.6 “Injured runners differed significantly from non-injured runners in that they were more likely to have run more miles per week, run more days per week, …” The researchers also noted there was no association between running intervals, sprints, or hills and incidence of injury.
Notice that in the two previous studies, injury was related to total running volume, not speed work. Conventional wisdom holds that speed work causes injury. Research challenges that belief. What I suggest is that when already overtrained runners add in speed work, injury results. The speed work was simply the straw that broke the camel’s back. The high mileage caused the runner to be overtrained. The addition of the speed work pushed the runner over the edge. Speed work could have been added without injury if the runner had not previously overtrained with too high mileage.
“A questionnaire was sent to all 960 entrants in a major city marathon race to obtain information on training related injuries. A total of 497 replies were received; of these 287 (58%) had incurred some form of injury during preparation for the race. Seventy-one of these individuals reported more than one injury. Almost all injuries affected the lower limb…”7
“The purpose of this study was to examine musculoskeletal injury incidence in amateur triathletes…Seventy-two recipients responded…Three-quarters (75%) sustained triathlon-related musculoskeletal injuries during training due to overuse. A majority experienced training interruption and interference with daily functioning and sought professional help for their injuries.” 8
Compare the rates of injury in these two studies. The significant thing about the triathlon study is that triathletes typically train at higher volumes than do runners, but triathletes generally run less mileage than runners. For example, the book Training Plans for Multisport Athletes, prescribes a peak of 13 training hours in a week for an Olympic distance triathlon of which only 3 hours is comprised of running. For the half ironman, a peak of 15 ½ hours is prescribed consisting of just 3 ½ hours of running divided amongst 3 runs in a training week. Other studies indicate that despite running less overall volume than equally trained runners, triathletes experience leg injuries at equal or greater rates than runners. In this study and others like it, the incidence of injury was significantly higher in triathletes than runners (75 – 99% vs. 50% for runners), indicating that overall volume of training has a profound effect on injury rates.
“Using a survey questionnaire design, we investigated the incidence, site, and nature of jogging injuries amongst all participants of a popular 16 km race…Of 4,358 male joggers, 45.8% had sustained jogging injuries during the 1 year study period…Occurrence of jogging injuries was independently associated with higher weekly mileage, history of pervious running injuries, and competitive training motivation…”9
Researchers at the University of Amsterdam conducted a review of the available research on running injuries. Here’s what they had to say. “Given the limitations of the studies it appears that for the average recreational runner, who is steadily training and who participates in a long distance run every now and then, the overall yearly incidence rate for running injuries varies between 37 and 56%…About 50 to 75% of all running injuries appear to be overuse injuries…”10
One third to one half of all runners will get injured every year and as many as 75% of those injuries are from overuse. Amazing. Remember, those injuries are related to overloading due to excessive mileage more than anything else.
Injury doesn’t occur just one step beyond optimal training. It occurs at some significant point beyond optimal training. Think of training volume as a continuum with zero training on the far left of the continuum and injury at the far right. Optimal training would be somewhere in the middle of the continuum. To reach injury you would necessarily pass beyond optimal training to reach the point of injury. Training at a volume resulting in injury, by definition, would mean that you are training at a volume significantly higher than optimal.
Even if high mileage were the best method for improving performance, the rate of injury would ensure that most runners would not achieve their best due to injury. Realistically, the high rate of injury experienced by runners suggests something is terribly amiss in the conventional training suggestion of more = better. It is unlikely that in order to reach optimal performance the body would require a level of stress that would simultaneously result in injury and decreased performance.
Lastly, we must address the concept of “easy runs”. Easy runs are widely promoted as a method of recovering from hard training days, as a means of consolidating gains from other training sessions, as building the aerobic base, and as a way of increasing weekly mileage and hence performance. There is no evidence that easy runs accomplish any of these goals. If easy runs increased the recovery rate, we would expect to see less injury and improved performance from those runners who employ easy runs on a regular basis. That is clearly not the case, since injury is associated with mileage and not intensity. Instead, easy runs increase mileage which in turn dramatically increases the risk of injury. Easy runs won’t make you fast or help you recover faster. They will, however, push up your weekly mileage and increase your chances of becoming injured.
In conclusion, research clearly indicates that high volume training is a high risk activity for the vast majority of runners. Since injury indicates that an excessive load has been placed on the body over time, it indicates that high volume training causes overtraining and injury and not the increase in performance so widely attributed to it. When injury research is combined with the research on volume and tapering, a compelling case can be made against the necessity of high volume training as a method for optimizing performance.
- Noakes T (2001). The Lore of Running, 749.
- Martin D., Coe, P (1997). Better Training for Distance Runners, 397.
- Noakes T (2001). The Lore of Running, 751.
- Hanc, J. Do the Right Thing, Runners World, Volume 38, Number 11, 62–62.
- Pollock ML, Gettman LR, Milesis CA, Bah MD, Durstine L, Johnson RB. Effects of frequency and duration of training on attrition and incidence of injury. Med Sci Sports. 1977 Spring; 9(1): 31-6.
- Jacobs SJ, Berson BL. Injuries to runners: a study of entrants to a 10,000 meter race. Am J Sports Med. 1986 Mar-Apr; 14(2): 151-5.
- Maughan RJ, Miller JD. Incidence of training-related injuries among marathon runners Br J Sports Med. 1983 Sep; 17(3): 162-5.
- Wilk BR, Fisher KL, Rangelli D. The incidence of musculoskeletal injuries in an amateur triathlete racing club. J Orthop Sports Phys Ther. 1995 Sep; 22(3): 108-12.
- Marti B, Vader JP, Minder CE, Abelin T. On the epidemiology of running injuries. The 1984 Bern Grand-Prix study. Am J Sports Med. 1988 May-Jun; 16(3): 285-94.
- Van Mechelen W. Running injuries. A review of the epidemiological literature. Sports Med. 1992 Nov; 14(5): 320-35.