TrainingConverting Science into Performance |
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Weekly Mileage and Marathon Performance A commonly held belief amongst runners is that increased weekly mileage will result in improved performance, especially at the marathon distance. Several reasons exist for this belief, chief amongst them is the anecdotal observation that elite marathoners all seem to run relatively high weekly mileages. In support of this belief, scientists have conducted numerous surveys of the training characteristics of marathon participants and detailed studies of the training characteristics of elite marathoners. As a general rule, faster marathon runners tend to run more miles each week than do slower marathon runners. For example a survey of 35 female marathon runners determined a fairly strong relationship (r = -0.74) between average weekly mileage and marathon performance (1). Other surveys have found similar correlations. These anecdotal observations and correlations are typically interpreted to mean that higher mileage is necessary for faster marathon performance. While modern training theory does not suggest that mileage alone is responsible for running performance, it does place great emphasis on the importance of a relatively high volume of training. While there may be a correlation between weekly training distance and marathon performance, it does not automatically follow that increasing weekly training mileage is the cause for the improved marathon performance. As has been pointed out to me many times, correlation is not causation. It is possible that weekly training volume exerts a strong influence on performance. However, it is also equally possible that other factors are causing the improved running performance, but that weekly training mileage gets the credit. Indeed, when scientists have conducted rigorous studies on the influence the various training variables have on performance, volume of training has not been shown to strongly influence performance. So, just how influential is weekly training mileage on marathon performance? Research by Dolgener and colleagues found no difference in the performance in novice marathoners who ran either 4 or 6 days per week (2). Critics of this particular study point out that the total weekly training distance between the two groups was an average of just 9 miles and suggest that this difference is too small to reach a meaningful conclusion on the influence of weekly training mileage. Therefore, lets take a look at two studies examining the influence of weekly training mileage and marathon performance. Research Grant et al In 1982 a group of Scottish researchers wanted to examine the validity of the recommendation that marathon runners need to run relatively high weekly mileages in order to adequately prepare for the marathon (3). To test the validity of this idea they decided to observe the training patterns of a large number of first time marathoners (but not necessarily novice runners). The subjects of this study were 88 first time marathoners preparing for the 1982 Glasgow Marathon. 104 subjects began the study, but 16 dropped out due to illness, injury, etc. The subjects were recruited from 225 runners who attended a training seminar for first-time marathoners at Glasgow University. The subjects were self-selected in as much as they attended the seminar and decided to both run the marathon and keep precise training records of all the data, times, and distances requested at the start of the survey. The average age of the subjects was 36.9 years, with a range of 18 to 70 years. A number of variables were requested of each runner, including their marathon performance time and the average training mileage during the final 12 weeks of training. The average weekly mileage of the subjects during the final 12 weeks of training was 37.2 miles. However, the range of weekly mileage across the 88 subjects was quite extreme, ranging from 15 miles to 63 miles. On the high end of the training spectrum, three runners averaged more than 60 miles per week for 12 weeks and eight runners averaged more than 50 miles per week. On the other end of the spectrum, one runner averaged just 15 miles per week for 12 weeks and three runners averaged 20 miles per week. So, while the average was 37 miles per week, the runners were not limited to a particular weekly mileage and the range of weekly mileage was quite large. What were the results? When correlated, there was a low -0.38 correlation between weekly training mileage and marathon performance. What does this mean? It means that there was a correlation between marathon performance and weekly training mileage. As weekly mileage increased, marathon performance improved. However, it was a very low correlation. Weekly training mileage had a prediction coefficient of just 14%. In other words, while weekly mileage had an influence on performance, it was a weak influence at best, predicting only 14% of marathon performance. The researchers concluded that “…weekly mileage during training is a poor predictor of marathon performance.” and "There is no practical relationship between average weekly training mileage and race time, for novices at least." Franklin et al Another group of researchers wanted “a) to determine the accuracy of predicted marathon finishing time among experienced and inexperienced marathoners, and b) to examine the relationship between training mileage per week and marathon performance”(4). The researchers interviewed 158 contestants of the 1977 RWR Marathon. Subjects were classified according to marathon experience as either first time marathoners, second time marathoners, or experienced marathoners (more than 2 marathons). 127 subjects completed the marathon, consisting of 63 first timers, 29 second timers, and 35 experienced marathoners. The research showed that weekly mileage influenced marathon performance only slightly. Correlation coefficients indicated that 16.7%, 28%, and 9.6% of marathon performance among first timers, second timers, and experienced marathoners respectively was explained by differences in weekly run mileage. It was also discovered that for any given training mileage per week, experienced marathoners ran faster than did first time marathoners. The results are tabulated in table 1. Table 1: the percentage of marathon performance accounted for by weekly mileage
The researchers commented, “…the variation show(s)…that training expressed in miles/week (without control for specific frequency, intensity, or duration) offers little explanation for the differences in marathon performance amongst experienced or inexperienced runners. Since distance is a function of intensity (speed), duration, and frequency, the present results highlight the inadequacy of training distance alone as a major determinant of performance.” Discussion Volume of training is one of the training variables and, as such, has an influence on performance. Of that there is no debate. The debate centers on just how much influence volume of training has on performance, with some placing great emphasis on it while others, myself included, place much less importance on it. These particular studies reinforce the belief that volume of training does not exert nearly as much influence as conventional wisdom suggests. With an average of just 17% of marathon performance being predicted by weekly training volume, other training variables obviously exert much greater levels of influence on performance than does volume of training. In addition to the above findings, there is another item that is of particular interest from these two studies. Marathon training programs in 1970s and 1980s placed their greatest emphasis on high weekly mileage, whereas today the emphasis is at least equally placed on the importance of a long run. Grant et al noted that prominent researchers and running coaches of the day routinely recommended weekly training distances for the marathon of at least 40 miles per week and that runners were commonly cautioned that running less than about 45 miles per week would result in the runner “hitting the wall” during the final miles of the marathon. Today, most training programs place at least equal if not more emphasis on the importance of the long run, with the recommendation that the runner increase the long run to about 20 miles three weeks or so prior to the marathon. Assuming that the runners in these studies generally followed the conventional training advice of the day and focused mostly on total weekly training mileage, we could say then that the runners in these studies did not train specifically to run the marathon distance. Instead, they trained to run a particular weekly mileage. Removing the specificity of the long run from the training program, we are left with only the influence of weekly training volume on performance. Therefore the results of this study are a direct reflection of the runners’ general training approach and are not influenced by the specificity of the long run. If this is truly the case, then the marathon results of the subjects in these two studies were predominately influenced by volume of training and general fitness, providing strong evidence as to the true influence volume of training has on performance. Recall the results of the marathon study by Dolgener. In that study intensity and specificity were the same for both groups while weekly mileage was different for the two groups. Marathon performance was equal for the two groups, with volume of training having no influence on performance. As noted above, the difference in volume of training between the two groups was criticized as being too small to create a measurable result. Considering the results of all three studies, the natural conclusion would be that volume of training does provide a small influence on performance and that relatively large increases in training volume are required before measurable differences in performance arise. Summary These two studies show that weekly training volume is a poor predictor of marathon performance and that volume of training exerts a relatively small influence on performance. The results of these studies are in agreement with the marathon study by Dolgener, reinforcing the ideas that specificity and intensity are much more influential on performance than is volume of training and large increases in weekly training volume are required to affect small increases in performance. Reference:
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