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The Science of Performance |
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Power Runningsm Part 7: Volume
How much should I run? What weekly mileage is best? How many days a week should I run? I think it’s safe to say that every dedicated runner asks these questions at some point in their running life. By correctly answering these questions, you will give yourself a big advantage in maximizing performance and reducing the risk of getting injured. We will attempt to provide you with some answers to these questions in this installment. If you conducted a review of the most common advice given to runners about weekly mileage, here is what you would find: run more. The basic advice is that the more you run, the better your performance will be. Not happy with your latest 5k performance? Then just increase your weekly mileage until you are running 50 – 60 miles per week. Want to run a fast marathon? Then increase your weekly mileage until you are running upwards of 100 miles per week. Certainly, you are advised to add in some speed work too, but make sure you get that mileage up first. “Increasing mileage to improve performance” is probably the most common advice in popular literature. How valid is this advice though? If you have read the first 6 parts of this series, you can probably guess what I’m going to say. After all, I’ve already challenged just about every other piece of standard advice you’ve been given about running. I will give you the answer right up front. Mileage is overrated. More is more; more is not better. Better is better. Research I have two arguments to back up my claims; science and the injury rate of runners. Let’s look at the research first. Despite what conventional wisdom preaches about the importance of weekly mileage, science does not back up this belief. There are no definitive studies showing that increases in volume result in improved performance. For example, David Costill conducted a study of collegiate swimmers where one group trained 1.5 hours per day while another group trained for 3 hours daily. Despite performing twice the volume of training, there was no difference in power, endurance, or performance time between the two groups (1). You might want to read that again. NO difference in performance between the two groups! This is only one study – there are others. Recall the study by Hickson, referenced in part 6 of this series, which showed a decrease in performance despite maintaining exercise volume. Two research studies on marathoners found little to no difference in performance based on weekly training volume (2,3). A 2-year study on cross country skiers found improved performance when intensity was increased, but not when volume was increased (4). At best, research indicates that volume of training exerts a relatively small influence on performance. So, despite what conventional wisdom preaches about the importance of volume, research simply doesn’t back up that advice. Conversely, there are quite a few studies showing performance improving from increased intensity and specificity, but not volume. If you reviewed all the available research on the influence training volume has on performance you would likely come to the same conclusion that exercise physiologists and authors McArdle, Katch, and Katch reached in their exercise physiology textbook, “As for training volume, more is not necessarily better”(5). Injury The second argument against high weekly mileage is the number of injuries that runners experience. At just 40 miles per week, more than half of all runners sustain injury. Additionally, research suggests that one-third to one-half of runners experience an injury each year. That is an incredible number! It means you will sustain a training altering injury every 2 to 3 years. If that statistic is correct, then something is terribly wrong. Why does running produce so many injuries? Injuries can be divided into two classes – extrinsic and intrinsic. Extrinsic injuries occur when an external force exceeds the body’s ability to absorb that force. For example, you fall while running and sustain an injury. Intrinsic injuries, the other type of injury, occur due to some factor inherent in the body itself and have nothing to do with external factors. For example, a runner develops a pain in his Achilles tendon and as training continues over the next several weeks the pain becomes progressively worse. Intrinsic injuries are the most common type of injury sustained by runners. What do intrinsic injuries have to do with volume of training? All training places a stress on the body. The more training you perform and the harder your training the greater the stress on the body. As training volume and frequency increase, the body is subjected to more and more stress. Intrinsic injuries are a clear indication that the training load placed on the body has exceeded the adaptive ability of the body. Injury indicates that the runner has reached his breaking point. Essentially, an excessive training volume results in an injury. Studies reveal that the rate of injury increases as the volume of training increases. Dr. George Sheehan in his book George Sheehan on Running to Win reports that the frequency of injury rises rapidly when mileage reaches 40 miles per week or 4 hours a week of running (6). Along similar lines, other studies indicate a rapid rise in the frequency of injury after just 3 days a week of running (7). Obviously each individual athlete has their personal breaking point but, on average, the majority of athletes significantly increase their chance of injury when they increase their volume of training beyond 3 – 4 days a week of running or about 4 hours of running per week. How Much Volume? In summary then, volume exerts a relatively small influence on performance. In practical terms this means that large increases in weekly mileage are required for small improvements in performance. However, the problem with increasing mileage is it significantly increases the risk of injury. It is to be expected that about half of all runners will sustain injury when mileage reaches about 40 miles per week of running. With these two facts in hand, I recommend 2 – 3 days a week of running for runners of average talents. Those runners with above average genetic talent can run more often, say 4 or 5 days per week, while elite level talent can run even more often – 6 or more times per week. Remember though, additional days of running do not necessarily result in an improvement in performance plus it can dramatically increase the risk of injury. Why run more volume if it doesn’t make you faster and only results in increasing your chances of getting injured? For those of average genetic talent, performance can be maximized with just 2 – 3 days per week of running if the right types of runs are conducted. Till next time, keep on running. Reference:
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