Running is a mileage focused sport. Runners typical talk about their training program in terms of weekly mileage, think in terms of weekly mileage, and train in terms of weekly mileage. Prof. Tim Noakes, MD, exercise physiologist, and author of Lore of Running, writes, “Most runners measure the number of kilometers they run each week and assume that mileage alone accurately measures their training loads.”
Due to this mileage focus, workouts are generally described in terms of mileage and intensity. For example, it would not be exceptional to hear something like the following exchange between 2 runners:
“What did you run today?”
“I did 6 miles at tempo pace.”
Most training programs are equally focused on weekly mileage. For example, the training week is often described in terms of weekly mileage.
“What did you do run this week?”
“I ran 40 miles.”
“I’d like to improve my 10k PR by 2 minutes, what do you recommend?”
“How many miles per week are you running now?”
“You should increase that. You have to increasing mileage if you want to get better.”
In fact, it’s not uncommon for complete training programs to be named in terms of weekly mileage. For example, in his popular book, Advanced Marathoning, Pete Pfitzinger, Olympic Marathoner & Exercise Physiologist, provides 3 mileage focused marathon training programs titled:
- One marathon on up to 55 miles per week
- One marathon on up to 70 miles per week
- One marathon on more than 70 miles per week
A review of most other training programs reveals the same focus on mileage.
In addition to runners and training programs thinking and talking in terms of weekly mileage, training goals are commonly set for increasing the number of miles run each week. Runners are routinely encouraged to increase their weekly mileage. For example, Arthur Lydiard is best known for his running prescription that all runners should build up to approximately 100mpw of aerobic running. Or, Mr. Pfitzinger in his article, Essential Ingredients II, Optimizing Your Mileage, says,
“You can build your aerobic base by increasing your running mileage, and/or doing more aerobic crosstraining. Unfortunately, some running writers have spread the misconception that increasing mileage produces little benefit to running performance. How then to explain that the world’s best distance runners typically put in 120 to 160 miles per week?…Racing performance clearly improves after a sustained increase in mileage (and the longer the race, the greater the benefit)…”
The message being sent is clear – to optimize performance, increase your mileage. After all, elites all run high mileage and look how fast they are; you should build your weekly mileage too.
I call this focus on weekly mileage “mileage-based” thinking and training. Mileage-based runners and programs think, talk, and prescribe in terms of weekly mileage. Of course, this is not to say that their focus is exclusively on mileage or that they don’t pay any attention to other training variables. It is to say that mileage plays a primary role in the thoughts and programs of most runners. Should mileage be a primary focus of training? Should training programs be mileage-based? Let’s logically analyze weekly mileage and see what the natural consequences of this focus are.
Are All 20 Mile Runs Created Equal?
Runners train at different paces based on their genetic talents and current level of fitness. That being the case, let’s say there are 2 runners – one is a 2:10 marathoner and the other is a 4:20 marathoner.
Both run 20 miles on the same day, at the same time, on the same course, etc.
Both run at the exact same intensity.
The 2:10 marathoner completes the 20 mile run in 110 minutes or 1 hr, 50 minutes (5:30 pace).
The 4:20 marathoner completes the 20 mile run in 220 minutes or 3 hours, 40 minutes (11:00 pace).
Does the 20 mile run:
a) Cause the same adaptations in both runners
b) Make the same inroad (i.e. cause the same amount of fatigue, muscle damage, glycogen depletion, etc.)
c) Require the same recovery time for both runners
Think long and hard about your answer before reading further.
Training places stress on the body, a stress known as training load. One of the ways the body reacts to the stress of the load placed on it via training is by improving – it gets faster, stronger, and/or more fit. How is the stress of training measured by exercise physiologists? Is it measured by mileage or by some other measure? Most runners, as Prof. Noakes wrote above, “assume that mileage alone accurately measures their training loads”. However, the fact is that training load is not accurately measured by mileage. It is measured by duration and intensity.
Training load = duration x intensity
Who suggests that mileage might not be the best measure of stress or training load? For one, Jack Daniels PhD does. In his book Daniels Running Formula he writes,
“Think Duration, Not Distance
I offer a final note about mileage. Although mileage is a convenient way to monitor work accomplished, it is often better to think in terms of total time spent training than in terms of distance covered… Remember, stress is a function of time spent doing something, so slower runners are often stressed more, even when completing lower mileage than their faster counterparts. That’s why a 20-mile run is more stressful for a slow runner than for a faster individual.
A 20-mile run will take a slow runner 3 or more hours to complete; a fast runner will cover the same 20 miles in 2 hours. This means that the slower runner has taken 50% more steps than the faster person, even though they covered the same distance. It is the number of steps that can wear you down, and it is the extra hour in the heat or on slick roads that takes its toll. It’s not just the 20 miles, it’s the time spent completing those 20 miles. To avoid overtraining and injury, a slower runner may have to run less total mileage than a faster runner.”
Dr. Daniels isn’t the only one who suggests mileage/distance is not the best measure of training. In fact, the exercise physiology community agrees on this topic too. My exercise physiology textbook states:
“Four factors significantly influence the aerobic training response:
- Initial level of aerobic fitness
- Intensity of training
- Frequency of training, and
- Duration of training”
Note that the textbook does not include distance or mileage as a factor of training response. Duration is the factor that is used
Prof. Noakes addresses this same topic in the 4th edition of Lore of Running:
“To identify the optimum training load, you must be able to quantify exactly how hard you are training. Most runners measure the number of kilometers they run each week and assume that mileage alone accurately measures their training loads. Yet that measurement does not quantify the quality of that training. Furthermore, the quality of the training is probably a better predictor of both future performance and the risk of overtraining. Hence, a measure of both the quantity and quality of training is required. Carl Foster of the Milwaukee Heart Institute is one scientist who has pondered this challenge. Foster and colleagues (Foster et al 1996) evaluated the performance of 56 competitive athletes as they increased their training. They calculated the training load as duration of the session multiplied by the average rating of perceived exertion during the session.”
The bottom line is that training load is best measured by duration x intensity.
Training load = duration x intensity
Now that you understand what training load is and how it is measured we can now answer the original question.
Are the two 20 mile runs equal?
The answer is NO.
Why? The answer is no because training load is correctly measured by duration x intensity, not distance x intensity.
The fact that both runners in the example ran 20 miles is immaterial. The training load experienced by each runner is NOT the same. Both runners ran at the same level of intensity, but one runner took twice as long as the other to complete the entire distance. This means that the training load on the 4:20 runner is 2x that of the 2:10 runner. Since the training load is greater for the 4:20 runner, he/she experiences a larger training stimulus, a greater inroad in terms of fatigue, glycogen depletion, etc, and also takes longer to recover (assuming rate of recovery is the same for both runners).
Measuring Weekly Training Load
As we have seen, individual training load is correctly measured by duration x intensity. However, just knowing the training load for each workout is not enough. We also need some way to quantify the overall training load. Why is knowing the total training load important? Prof. Noakes explains, “…there is a limit to the amount of training the body can benefit from. Training beyond that limit produces progressively poorer performances, leading ultimately to overtraining.”
A too high training load leads to overtraining and a worse performance, not a better one. That’s why you need some way to quantify the total training load. How do you measure the total training load? Training load is calculated by summing the training load for each individual workout. By adding up the training load of each workout conducted in a particular week, you will have your total training load for the week. Table 1, drawn from an example in Mr. Pfitzinger’s book Advanced Marathoning, illustrates the calculation of daily and weekly training loads.
Table 1: Calculating daily & weekly training load
|Day||Duration (min)||Intensity (RPE)||Training Load|
|Total Weekly training Load||2535|
Duration is measured in minutes of training. Intensity is measured using the modified Borg scale of Rating of Perceived Exertion (0-10) calculated as a session RPE, or overall intensity of the workout. Total training load is calculated by adding up the individual training load of each workout. In this way weekly training load is properly quantified using the 3 variables influencing fitness – duration, intensity, & frequency.
Analysis of Weekly Mileage Recommendations
I’ve often been told by other runners that since elites are the fastest runners on the planet and they all run high mileage this proves that high mileage is best. Mr. Pfitzinger made the same argument in his earlier quote above. Consequently, the reasoning goes, all other runners should strive to run similar high mileages in order to maximize performance. Now that we understand how to properly measure weekly training load, we can use this information to analyze this particular piece of training wisdom. Let’s take 3 marathoners all following the same training program, which includes running 100 miles per week (mpw), but with individual marathon finishing times of 2:10, 3:15, 4:20.
Table 2 shows the recommended training pace and the percent difference in pace for four different types of runs, for each of our 3 marathoners. Pace recommendations are drawn from McMillan’s pace calculator, at http://www.mcmillanrunning.com/rununiv/mcmillanrunningcalculator.htm.
Table 2: Recommended training paces & % pace difference
|Runner||Recovery Run||Easy/Long Run||Steady State Run||Tempo Run|
|3:15||8:57 (138%)||7:57 (145%)||7:04 (150%)||6:41 (148%)|
|4:20||11:26 (177%)||10:26 (191%)||9:25 (199%)||9:02 (200%)|
Recall that all 3 runners are following the exact same training program. This means they are all running the same daily workouts, for the same distance and intensity levels. They are running the same weekly distance, 100mpw in this example. Knowing that all 3 are following the same training program allows us to calculate the overall weekly training load for each runner. Our calculations reveal that:
- As the fastest runner, the 2:10 marathoner completes his 100 mpw in the least amount of time
- The 3:15 runner takes approximately 1.5x times longer to complete each workout than the 2:10 runner, so his total training time is 150% of the 2:10 runner
- The 4:20 runner takes approximately 2x times longer to complete each workout than the 2:10 runner, so his total training time is 200% of the 2:10 runnef
Table 3: Weekly training load calculated for 3 runners of varying abilities all following the same training program. 100% training load based on total weekly training load of the 2:10 marathoner.
|Runner||Weekly Training Load|
As can be seen in table 3, the weekly training load increases for each decrease in marathon performance. I’ve used just 2 slower runners to illustrate the point, but the point to understand here is that any time 2 or more runners are following the same training program, the slower runners are training at a higher training load than the faster runners. It doesn’t matter if they are training for a 5k, 10k, or a marathon. By definition, any mileage-based training program causes the slower runners to train at a higher training load than faster runners unless that program makes some allowance for the varying performance level of runners. This difference in training loads at the same weekly mileage explains Dr. Daniels comment, “…slower runners are often stressed more, even when completing lower mileage than their faster counterparts.”
What physiological reason can be used to justify having slower runners train at significantly higher weekly training loads than faster runners? Why would the optimal training load for a slow runner be up to 200% or more than that of a faster runner? Can this natural consequence of mileage-based training be justified in any way?
I know of no physiological justification for having slower runners training at a significantly higher training load than faster runners.
Equalizing Training Load
As you now know, the challenge with recommending that non-elite runners run the same or similar weekly mileages as elite runners is that non-elites will be training at a significantly higher training load than elite runners. There is no way around that physiological fact.
If you truly believe that the weekly mileage of elites is optimal, then by definition what you actually believe is that the training load of the elites is optimal. Therefore it follows that you should recommend that same training load for everyone. In other words, slower runners should incur the same training load as elite runners, no matter what weekly mileage that results in.
This means you should recommend that all runners run as close to possible to the same % of easy runs, long runs, speed workouts, etc, as elites. That training duration and frequency should mirror as closely as possible that of elite runners. The only difference, then, between the training of elite runners and non-elites would be mileage – elite will run higher mileage and slower runners will run lower mileages. Both will be training at the same exact training load, but will be running different weekly mileages. In other words, you should recommend that slower runners duplicate the training load of the elite runner in terms of the 3 training variables of frequency, duration, and intensity with no regard to the weekly mileage of the elites. If you had slower runners duplicate the same training load of elite runners, what would that program look like in terms of weekly mileage? Using 100 mpw as our base mileage for elites, table 4 illustrates the breakdown:
Table 4: Weekly mileage resulting in equal weekly training loads for marathoners of differing abilities
|Runner||Weekly Mileage Resulting in
Equal Weekly Training Load
By having the slower runners duplicate the frequency, duration, and intensity of elite runners so as to duplicate the training load of the elites, those runners must run less than 100mpw, often much less. In the above example the 3:15 marathoner reaches the same training load as the elite runner at just 65 mpw. The 4:20 marathoner duplicates the training load of the elite runner at a weekly mileage of just 50 mpw.
Of course, you might say that 100 mpw is actually too low a training volume for an elite runner and that their optimal mileage is actually 120 – 140 mpw. Will that make any difference in the main point? None at all. No matter what weekly mileage you believe to be optimal for elites, the main point is that if you recommend non-elites train at a similar mileages you are forcing slower runners to train at significantly higher training loads than elite runners.
The bottom line is this – if you believe that the high weekly mileage run by elites proves that their training program to be superior, then, by definition, you believe the training load of the elites is optimal. That being the case, if you want to be consistent you must recommend the same training load for everyone, no matter what weekly mileage that translates into. If, instead, you recommend that everyone should run the same weekly mileage as elites, then you are recommending a significantly greater training load than the elites train at, a recommendation that has no physiological support. There is no physiological justification for having slower runners train at much higher training loads than elite runners.
Running is a mileage focused activity. Runners think, talk, and train in terms of mileage. Workouts are usually described in terms of distance run and intensity (I ran 6 miles at tempo pace). Training programs are typically specified in terms of weekly mileage, such as “a 50 mpw marathon training program”. I term this focus on mileage “mileage-based training”.
The challenge with mileage-based training is that mileage is not a good measure of training load. Training places a stress on the body, a stress termed training load. Training load from an individual workout is not measured by mileage; it is measured by duration x intensity. Total weekly training load is correctly measured by summing the training load from each workout conducted in that week.
All mileage-based programs ultimately result in slower runners training at a higher training load than faster runners, unless some allowance is made for the varying performance of runners. There is no physiological justification for recommending higher training loads for slower runners than for faster runners.
It is often suggested that the high weekly run mileage of elites runners proves that high mileage training is best. Based on this belief, common advice is that runner should strive to increase weekly mileage over time, preferably until they are running similar mileages as elite runners. The challenge with this recommendation is that when slower runners train at high mileages they are incurring significantly higher training loads than do elite runners.
If you are a person who truly believes that the high mileage run by elites proves the superiority of that training program, then, by definition, you believe that training load of the elites is superior. That being the case, you should recommend that others duplicate the training load of elites, regardless of the weekly mileage associated with that load.