Training

The Science of Performance

Running and Injury

Conventional training methods suggest that increasing weekly training mileage is the best method for improving competitive performance. While increasing mileage may or may not be the best training method for improving performance, one thing is clear – increasing mileage exposes the runner to an increasing risk of injury.

For runners who may be considering adopting a higher mileage training program the following research information on the incidence of running related injury is offered for review.

The information found in tables 1-4 below are drawn from two research studies on the incidence of injury from running. These two studies are not unique - numerous other studies have been done on this topic – and the results are not unique either. The findings of these two studies are representative of the findings of other studies on this same subject.

In the first study, Pollock et al examined the incidence of injury related to different duration and frequency of training. To study the effect of duration on injury he had subjects train either 15, 30, or 45 minutes, 3 times per week. To study the effects of frequency on injury he had subjects train 1, 3, or 5 days per week, 30 minutes per session. The results are tabulated in tables 1 & 2.

Table 1: Effects of duration of training (running) among men on cumulative incidence of injury with training frequency^aand intensity^b held constant for 20 weeks. (1)

Duration (min/day)	No. of participants	Injury Incidence (%)
Control (0)	18	0
15	20	22
30	25	24
45	24	54
a Frequency of training 3 days per week
b Intensity of training 85 to 90% of maximum heart rate

Table 2: Effects of frequency of training (running) among men on cumulative incidence of injury with duration^aand intensity^b held constant for 20 weeks. (1)

Frequency (days/week)	No. of participants	Injury Incidence (%)
Control (0)	13	0
1	15	0
3	25	12
5	18	39
a duration of training 30 minutes per day
b Intensity of training 85 to 90% of maximum heart rate

In a classic study of competitive runners, Koplan randomly surveyed 1250 men and 1250 women registered for a 10-km race, to which 693 men and 730 women responded. The data from his study are tabulated in tables 3 & 4.

Table 3: The effect of amount (miles/week) of training (running) on cumulative incidence of injury in men. (2)

Miles/week	No. of participants	Injury incidence (% per year)
0-9	70	21.4
10-19	191	29.3
20-29	183	36.1
30-39	93	40.8
40-49	25	52.0
>50	31	71.0
Participants were 693 men, mean age 33.4 years, overall injury incidence 37%; 593 (86%) reported mileage run.

Table 4: The effect of amount (miles/week) of training (running) on cumulative incidence of injury in women.(2)

Miles/week	No. of participants	Injury incidence (% per year)
0-9	89	29.2
10-19	221	32.1
20-29	158	41.1
30-39	72	52.7
40-49	14	35.7
>50	21	57.1
Participants were 730 women, mean, mean age 29.9 years, overall injury incidence 38%; 575 (79%) reported mileage run.

In summary, increasing weekly run mileage is associated with a rapidly increasing incidence of injury. Before making a decision to increase weekly mileage runners should be fully aware of the risk they are exposing themselves to. Armed with an accurate understanding of the risks associated with increased training mileage each runner can decide for him/herself if the purported benefits of increasing mileage are greater than the increased risk they will be exposed to.

References:

1. Pollock ML, Gettman LR, Milesis CA, et al Effects of frequency and duration of training on attrition and incidence of injury. Med Sci Sports Exerc 1977; 9: 31-6

2. Koplan JP, Powell KE, Sikes RK, et al. An epidemiologic study of the benefits and risks of running. JAMA 1982; 248: 3118-21

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