Run Like A Pro: Balance Intensities Like A Pro (Part 1)

So like I was saying (lo these many months ago 😬), reading running books by your favorite authors can be a little like a religious devotee reading their religious text. They already know pretty much what's in it, they don't expect a lot of surprises, but sometimes it's good to be reminded of what you know you should be doing that you've maybe gotten a bit away from doing. So we are here to talk about where and when in Run Like A Pro I found myself feeling a bit convicted and like I needed a bit of revival.

The chapter in question is called "Balance Intensities Like A Pro," intensities being whether you're running easy, hard, or somewhere in the middle. 

If you have read 80/20 Running or any other book that discusses how runners should allocate their fast training miles vs. their easy training miles, the advice in this chapter will not come as a shock. In case you haven't, though, a quick overview.

When scientists look at the most successful endurance runners, from 3-10K track specialists to half marathon and marathon road racers, all of them seem to stick quite close to an 80/20 split--that is, 80% of their miles done at an easy, comfortable pace and 20% done at moderate and high intensities (speed work, tempo/threshold runs, etc.). 

The conclusion: "Relatively high training volume at low intensity ... was beneficial for the development of running performance at the top level" (Run Like A Pro (Even If You're Slow), pp. 66-67). The same has been found to be true for elite athletes in other endurance sports such as cross-country skiing, cycling, rowing, swimming, and triathlon.

It's one thing to say "This is what works best for the pros," but the science makes it clear that an 80/20 split of easy vs. hard training is likely to be the most effective approach for just about anyone who wants to improve at endurance sports. (I'll direct you to Run Like A Pro, 80/20 Running, and any number of other science-based titles for a detailed explanation about why.)

If you've been reading here for a while, you might remember that roundabouts fall 2014 I discovered that I had been doing all my "easy" runs way too fast and spent like six months discovering just what "easy" was supposed to feel like. Before then my easy runs were often falling around 8:45-8:50/mile, which, honestly, was not a *hard* pace for me. "That's even slower than marathon pace!" I would argue, which was true, my marathon pace at the time being somewhere around 8:20ish probably. Marathon pace is supposed to be super slow and easy, so if you're running even slower than that, surely this counts as an "easy" pace?

Alas it's just not true. 

OK fine here is a little science.

If you have someone start off walking slowly, then walk faster, then jog really easy, then have them continue running faster and faster and faster, the rate at which their body is consuming oxygen will increase--starting off fairly low while they walk, and rising as they begin to work harder.

If your subject continues to speed up, running faster and faster and faster, their body will eventually reach a point where it literally cannot consume oxygen any faster. Scientists call that point the person's VO₂max. Running at your VO₂max feels super shitty and you can't do it for very long before you have to slow down.

As you watch your imaginary research subject run faster and faster on their way to their VO₂max, you will also see two other notable points at which their rate of oxygen consumption increases noticeably. We label these two points VT₁ (the first ventilatory threshold) and VT₂ (the second ventilatory threshold).

Fun Facts About VT₁:

• Aerobic threshold, basically
• Occurs at the pace you could run for 2.5-3 hours (so ~marathon pace if you're fast-ish, slower than marathon pace if you're a bit slower, & half marathon pace if you're a lot bit slower.)
• About 4 out of 10 in terms of effort at first (obviously it gets closer to 9-10/10 as you approach that 2.5-3 hour mark)
• Divides heart rate zones 2 & 3, basically
• Easy to talk up to this point
• Below, no problem clearing the lactate out of your blood as your muscles produce it

When we pass VT₁, we have to breath a little harder. It's not terribly uncomfortable but it is getting a little harder to talk and the lactate now is starting to accumulate in our blood faster than our body can clear it out.

Fun Facts About VT₂:

• Lactate threshold, basically (also sometimes still called 'anaerobic threshold,' though that term is not exactly accurate)
• Occurs at the pace you could run for about an hour (so ~10K pace for slower folks, half marathon pace for the very fastest elite male runners, and for a lot of us somewhere in between the two)
• About 6-7 out of 10 in terms of effort (again obviously getting harder the longer you stay there)
• Divides heart rate zones 3 & 4, basically
• Almost impossible to talk past this point
• Lactate REALLY starts to build up in the blood!

So yeah -- below VT₁ = "easy", between VT₁ and VT₂ = "moderate", and above VT₂ = "hard".

Now you might be thinking, "But what's wrong with moderate intensity? Obviously no one should do tons and tons of high intensity training, but surely there's no problem with lots of moderate intensity training?"

OK, buckle up, cowboys -- here is where the rubber meets the road if you really want to learn something useful.

Alas, it turns out that VT₁ is a big turning point in how both the body and brain respond to training. While jumping past VT₂ may feel worse than crossing VT₁, VT₁ is a much bigger physiological change than VT₂. Both the brain and body have to suddenly start working a lot harder. There is a big jump in how much the various body systems are stressed, how long it takes to recover, and how much the body can tolerate before there is more harm than good.

What does this mean?

It means that while it may seem intuitively that easy and moderate-intensity running have more in common with each other than with hard running, the science tells us something different. 

In truth, moderate- and high-intensity running have a lot more in common than moderate and easy running do.

How a lot of us think it is:

How science says it really is:

While moderate- and high-intensity running offer lots of benefits, they also have a very high cost for the body and it doesn't take long to reach the point of doing more harm than good. Running under VT₁ (that is, in zone 2) on the other hand, has more modest benefits per minute but the body can tolerate a lot more of it.

Like, A LOT more. 

Tune in next time for more on why this is and why it matters!