How To Tell if you are Actually Recovering from your “Recovery” Runs

If you’ve taken a peek at the Founder’s Dashboard, you may have noticed that the vast majority of my easy runs are at a very slow pace – to the point where if I went any slower, I would be going backwards. You may have also noticed that I don’t do any long runs (i.e. over 1 hr). This hasn’t always been the case. When I first started running, almost all my “easy” runs were near the top, and sometimes over, my “Zone 2” heart rate, and I would do weekly long runs up to 1.5 hrs in duration. However, now, I’ve dramatically decreased the pace on my easy runs and completely cut out long runs. This change was prompted in large part by the program I am currently following, commonly known as the Norwegian Singles Method.

If I had to boil NSM down to one core philosophy, it would be maximizing the volume of high-end aerobic work -aka subthreshold/heavy domain training. This is accomplished, in part, by keeping easy days very easy so that you are fresh for your workouts. The general idea is that although easy days can serve a dual purpose of both improving fitness and assisting with recovery, NSM prioritizes the latter.

But how do you know if you’re actually recovering from your recovery runs?

As far as I’m aware, there’s nothing explicit in the NSM protocol that tells you this. There’s just a general recommendation to keep easy runs below 70% of max heart rate. However, while this may be a decent rule of thumb, it is somewhat arbitrary in the same way that setting heart rate zones by max heart rate is arbitrary – these values are not tethered to an individual’s specific physiology.

This is yet another area where ventilation can provide unique insights beyond heart rate or even lactate. Although lactate is regarded in the endurance world as the gold standard for intensity control in the field, it has a number of flaws, largely due to the way it is measured – i.e. by taking a blood sample at the earlobe or fingertip. The issue with this, particularly in the moderate domain, is that by the time blood from the legs reaches your earlobe or fingertip, some or all of the lactate produced by the muscles may be consumed in the same muscle or somewhere else in the body. This is why lactate curves tend to be flat before LT1, which means lactate meters cannot provide an accurate indication of relative intensity within that domain (hence the reliance on the arbitrary 70% of heart rate line).

However, because ventilation corresponds not just to H+ accumulation, but also CO2 production, which increases with intensity, it can provide insights into your present condition at any pace. Accordingly, if your primary goal for a run is recovery, you can compare your ventilation levels to your baseline to assess if you are truly recovering.

If you take a look at the Founder’s Dashboard, you can see that my easy runs are all over the place. Sometimes they progressively get faster. Sometimes they get faster and then slower. Sometimes they just get slower. Sometimes they stay at the same pace. There’s a method to this madness.

I modulate the intensity of my easy runs based on where my ventilation and drift levels are for that particular run compared to my baseline. If my ventilation levels are lower than the baseline and my drift is flat, it’s an indication that my recovery is good and I increase the pace. If my ventilation levels are right around my baseline, it’s an indication that my condition is normal and I maintain the pace. If my ventilation levels are above my baseline, it’s an indication that my condition is impaired and I decrease the pace. And if my ventilation levels remain high and my RPE is also significantly higher than normal, I stop.

The general idea is that if my condition is good, I have capacity to pick up the pace to leverage the aerobic benefits of the workout, but if my condition is poor, to help ensure that I am fully recovered by the next workout, I drop the pace. The goal in that scenario is to decrease the amount of fast twitch fibers that I’m utilizing for the effort. You see, fast twitch fibers tend to share certain characteristics that make them more prone to damage, more prone to cause damage and less prone to fast recovery.

Fast Twitch Fibers Are Less Resilient to Mechanical Stress: Compared to slow twitch fibers, fast twitch fibers tend to be more structurally fragile, which means when they are activated, there is a greater possibility they will suffer microtears from the eccentric load that accompanies every step.

Fast Twitch Fibers Generate More Waste: Compared to slow twitch fibers, fast twitch fibers tend to have a higher ATP cost, thereby producing more waste in the form of H+ and Pi. Additionally, fast twitch fibers have fewer mitochondria and more glycolytic enzymes, so they tend to prefer utilizing carbs for fuel which produces more CO2 per oxygen consumed compared to fat. This waste can cause additional metabolic disturbance/stress on the muscles, slowing recovery.

Fast Twitch Fibers Have Lower Capillary Density: Compared to slow twitch fibers, fast twitch fibers tend to have a lower amount of capillary coverage per square area, which generally corresponds to a lower blood supply. One of the primary ways easy runs are effective for recovery is by stimulating delivery of blood to the leg muscles to assist with the repair process and to clear away byproducts. This may help explain why fast twitch fibers tend to take longer to recover compared to slow twitch fibers.

But how do I know that slowing down will reduce the number of fast twitch fibers that are recruited?

Well, I don’t know for certain, but in the last log, we mentioned Henneman’s size principle, which generally states that the body tends to recruit smaller units before larger units as intensity increases due to activation thresholds. Fast twitch fibers are generally controlled by larger motor neurons, and Henneman’s principle also typically works in reverse. This means that if my ventilation is elevated compared to baseline on a given day, there’s a decent possibility that the higher ventilation is due to additional CO2 production resulting from impaired contractile force and greater fast twitch fiber recruitment. And in that scenario, if I slow my pace, it’s likely that fast twitch fibers will be derecruited first before slow twitch fibers.

So, for example, in my last training log I noted that the day or two after squatting, my ventilation is typically elevated, likely due to muscle damage. Saturday’s easy run, one day after my Friday squats, conformed to this pattern. What I didn’t mention in that log, was that after that morning’s easy run, later that day I did another “easy” session, which, in hindsight ended up being a mistake.

You see, Saturday afternoon, I found myself in a bit of a unique situation. I had an hour of free time all to myself – something that is a very rare occurrence for a father of 3. So I decided to take advantage of the time by going out for a relatively short, “easy” jog. I ended up running around 3 miles at an average 9:44 min/mi pace, with average ventilation of 107, well below my VT1 of 122. Everything felt smooth and comfortable during the run, but little did I know, that the next day I would pay for this terrible indiscretion.

On most Sundays, if my soreness is dissipated, I can usually expect to see my ventilation levels normalize, but that was not the case here. I started out at 11:46/mi, a click above Saturday morning’s easy run pace, but soon noticed that my ventilation was still significantly elevated.

Although sometimes my ventilation will start high but then gradually come down and stabilize at a normal level around 10 minutes into the run, that did not happen here, so I stopped 24 minutes in and lowered the pace to 12 min/mi. Falling back to this pace usually tempers my ventilation, but again, it remained elevated. Perhaps more importantly, I did not feel great, so I decided to cut the run short after just 12 minutes, with the hope that only running 3 miles on the day would provide enough rest so I could be fully recovered for today’s threshold session.

However, although 7:22/mi pace on most days typically puts me in the heavy domain, today’s run appeared to be right on the upper edge, perhaps going over into the severe domain. Usually for these shorter intervals my ventilation will plateau after the 3rd or 4th interval, but here, it continued to creep up, as I hit ventilation levels above my VT2 threshold towards the end. Additionally, my Recovery Score for the last 5 intervals teetered around my VT2 Recovery Score Threshold of 68%. Lesson learned – Keep easy days easy.