The Basics Part 3: Volume
How and how much?
This is part three of a “who-knows-how-many” part series. Check out Part 1 and Part 2 if you haven’t already.
The process of training is all about stressing the different tissues and systems associated with performance, and then resting those tissues and systems so that they can come back stronger. Conceptually we know that there is a right amount of stress each day. If you add too much stress to the body, it takes an excessively long time to recover and training gains are minimal. This is over-training. It’s also possible to add not-enough stress, and thus not engage the adaptation process. This is under-training.
The tricky part about this is that it’s really difficult to measure this kind of physical stress! Since the body is made up of literally trillions of cells made up into thousands of tissues and tens of systems, and since every exercise bout (hell, every step) stresses each of those cells and tissues and systems a little differently, even if we can measure one of the pieces directly (usually through some kind of invasive poking and prodding), we can’t possibly measure every piece. To combat this problem, coaches/scientists often use workload (the combination of the duration and intensity of a workout) to act as a proxy for stress. Even if we can’t directly quantify how much a workout stresses the bits, at least we can quantify the workout itself, and then see how the entire human organism reacts to that workout, and voila, we have a way to quantifiably prescribe training!
While this approach is widely used, and works pretty well, it’s important to realize that it’s still imprecise! There are two main problems with workload as a proxy for stress:
First, the same workload can cause different amounts of stress. There are many factors that will change the way your body reacts to the same workout, including but not limited to: sleep the last couple nights, nutrition status, hydration status, stress levels, and freshness levels.
Second, workload can be measured in different ways and mean different things! An important difference between types of workload for the purposes of this discussion is whether the intensity (remember workload = intensity X duration) measured is relative or absolute. Let’s say that in April, Jim can run six miles in one hour averaging 65% of his maximum heart rate (HRmax). If his training goes well, then by July, maybe he can run seven miles in one hour at the same 65% of HRmax. Thus if you’re measuring the workload using heart rate, then that workout is the exact same workload in April and July. Show that to any physicist, however, and he’s going roll his eyes and call you names, because obviously it takes more work to run seven miles than it does to run six. So while the relative workload, or the workload as it compares to Jim’s ultimate capacity (same percentage of max HR) is the same between April and July, the absolute workload, or the actual physical amount of work done is ~16% more in July compared to April!
This difference between absolute and relative workload thus creates a conundrum to training progression. Let’s say Jim runs 10 hours in a week in April and at an average of 65% HRmax, he’ll run 60 miles. If you were Jim’s coach, what would you have him do next to progress the workload by 5% per week (a fairly accepted speed of progression)? Are you going to add 5% more hours per week? Or 5% more miles per week? It’s important to realize that those are not going to result in the same workload! Let’s say you keep increasing the hours 5% by per week, and let’s say he gets 2% faster every week at the same heart rate. At the end of eight weeks, he’ll be running 97 miles per week, in about 14 hours. BUT, if you increase the miles by 5% each week, and with the same 2% improvement per week, at the end of eight weeks he’s running 84 miles per week in about 12 hours. Why are those end numbers so drastically different?
Well, remember that the whole point of training is to increase absolute intensity compared to relative intensity (that 2% increase in speed from above). If you’re trying to get faster at a short race, what you’re trying to do is increase your absolute intensity (speed) at the same relative intensity (maximum HR). In the words of Greg Lemond “It doesn’t get easier, you just go faster.” Similarly, if you want to finish an ultra, you don’t necessarily need to change your absolute intensity (speed), but you do need to lower the relative intensity (HR/feel) at that speed so that you can hold it for the duration of the event. In both cases you’re changing the relationship between absolute and relative intensity.
So if we go back to Jim, you can see that if you’re using relative workload (hours-times-heart-rate) to monitor and progress training, and the relationship between relative and absolute intensity is changing, then when you increase hours you end up increasing the workload twice, once from increasing volume, and once from the increasing absolute intensity.
This is important because this means that if you’re using relative intensity to monitor workload, it can be pretty easy to over-stress your body! For this reason, I think that the classic advice to “increase training by 5% each week” works pretty well when talking about absolute workload metrics of miles, or vertical feet, or calories, or kilojoules, but not for relative workload metrics like hours-times-heart-rate or TSS, or TRIMPS, or ROLLS. For these relative metrics, I think something much smaller like a 1-2% is the max you should go, and you should actually see really good results even when holding relative workload steady!
NOW, a savvy reader might be saying “WTF dude, absolute workload doesn’t really matter, because if the relative workload stays the same, that’s saying that the body is experiencing the same amount of stress.” And you know what, fictional reader, you’re not wrong, but neither are you quite right. While for much of the body, stress is going to correlate nicely with relative intensity, there are important parts, most notably your glycogen stores, which track much more closely with absolute workload. So while it’s 100% true that only measuring absolute intensity isn’t “right,” because the same amount of miles or calories or kilojoules is going to hit very differently if you’re a couch potato versus an elite athlete, it’s also “wrong” to say that only measuring relative intensity is enough to get predictable stress. This is why I recommend the 1-2% increase in relative measures, instead of just saying “don’t use relative measures.”
The real point of all of this though, is to remember that our goal with training isn’t to train the most hours, or burn the most calories, or look the best, or whatever. It’s to change the relationship between absolute and relative intensity. If you’re doing a good job of measuring that relationship regularly through formal or informal testing, and adjusting your workload (however the hell you measure it) to make sure that you’re continuing to improve, then you’re doing it right! Remember that measuring workload is supposed to support gains in fitness, and so if you’re gaining fitness, nothing else fucking matters.