About Threshold Running
I feel I have touched on what threshold running or tempo running is in previous blog posts but have never prepared one specifically about that type of run.
When I started technifying my training through the introduction of some marathon training concepts I encountered plenty of literature talking about threshold sessions. Some other books, programs, videos and internet articles referred to tempo intervals, others talked about lactate threshold (LT) and others mentioned anaerobic threshold (AnT) or even functional threshold power (FTP). It was a mine field and I was really confused about the entire thing.
I knew there was a type of fast run that was supposed to help improve fitness level but I was not sure about how to do it and why it was good for me. So instead of buying into every session I read about in every book I tried to understand the concept behind what it is that helps me improve my fitness. That also meant not caring too much for the extremely technical and scientific terminology from a physiological point of view. I did, of course, read about all the technical terminology but in the end running should be easier than trying to decipher what OBLA stands for. Onset of Blood Lactate Accumulation, in case you’re wondering.
So I will try to explain threshold running in a simple way. Or the best I can. This is not necessarily scientifically accurate for those scholars amongst us as I want to focus on the running piece and not so much on what causes what and the difference between correlation and causality. There are plenty of forums where the technicalities, scientific research and physiological theories are discussed at length. Think of this as threshold running for dummies (which really helps me simplify things).
As we increase the intensity at which we run the energetic demands to feed our muscles change too. Very simple. The higher intensity the activity, the more we burn. There is a point, however, at which a by-product (lactate) that’s produced in those high intensity efforts accumulates at a faster rate our blood can clear it. At that point our muscles can’t keep performing at that reached intensity anymore and we begin to slow down. In practical terms I’m talking about that moment at the track or during a very fast race when our legs suddenly start feeling heavy and like they’re full of lead. I think we’ve all experienced that when setting off too fast in a parkrun.
With that concept in mind it would therefore make sense to, in order to maximise our training, be able to either improve the point at which that happens or the ability to run just below that point for longer periods.
How do we do that? There are several ways of knowing what that point is. The most accurate is by actually measuring the lactate levels in the blood during a run. Lactate tests on a treadmill are fairly common and extremely accurate. Another similar test (even more accurate but different to measurements of lactate) would be measuring oxygen and carbon dioxide concentration of the inhaled and exhaled air on a treadmill.
When athletes take those tests they are able to understand at what intensity that point of no return is by using heart rate as the easiest indicator of effort. This means that any runner who has had one of those tests has a corresponding heart rate % to their lactate threshold or to their anaerobic threshold.
This is the way I know my own thresholds. I usually take one of those tests just before I embark on a marathon training program to understand where my thresholds are and what that corresponds to in heart rate terms. My latest test from 2018 showed that my anaerobic threshold is surpassed at around 174 beats per minute. That means that staying under that figure when running (using a heart rate monitor and strap) allows me to stay in the zone where I can maximise my running.
The reason this is a good thing is because if we can increase the time we can spend running just under that threshold we can train our bodies to last longer at higher intensity efforts. The moment we cross the threshold we become inefficient and our time is up in that race. Once we’re over the threshold the anaerobic system is in full flow and that is a very finite source of energy to feed our muscles so it’s a matter of time (up to 20 minutes maybe) before we get to our maximum heart rate if our legs are still moving by then).
So the name of the game is to find that point of no return and stay under it for as long as possible. What happens if we don’t know where that point is for us because we don’t have a heart rate monitor and we haven’t tested ourselves on a treadmill?
Luckily, there are easier (less accurate) ways of determining that threshold. Research has shown that in fairly well trained athletes that threshold is reached after 60 minutes of maximum effort. In order to understand what that is we can look at what pace we might be able to hold for 60 minutes of racing. This can be easily obtained by looking at our 10k or half marathon times.
If we run a flat out 10k at the beginning of our training program we can easily adjust that pace to understand what our Threshold pace should be. In practical terms anyone running a 10k at 3'45"/km can extrapolate what pace they would run for 60 minutes (around 3'50" to 3'55"/km) and use that as their threshold pace.
Threshold sessions need to be designed to maximise the amount of time spent just below the HR threshold. If we use my example the aim would be to run for as long as possible under 174bpm.
Now, the body is not a machine that can be configured with some sort of cruise control to run at 174bpm from the moment go. Instead, it takes us a few minutes for the muscles to warm up and for the heart rate to slowly go up to that point. If we get there too quickly we will not be able to stop it when we get there, if we get there too slowly we may start to fade muscularly. It’s a very difficult art to run at threshold.
The below graph shows how the heart rate increases over time at a set pace. Then that heart rate is close to going over the threshold it’s time for a recovery and start again. This is from a 3x17'@T session I did last year.
Since the effort corresponds to that of the pace we would have for a 60 minute race we can assume that the maximum time we’d spend at that pace would be around 40 minutes to allow for the non-racing scenario of a training run. Even when fresh, 40 minutes at that pace would be quite ambitious, so it is easier to break it down into smaller chunks or “tempo intervals”.
So instead of 40’ at 3'50"/km, that 37 minute 10k runner would start with 2–5 minute efforts closer to HM pace. Something like 3 or 4 times 5 minutes at 3'55"/km with a about 3 minutes recoveries.
As our fitness improves we can stretch those runs to maybe 10–15 minutes of continuous effort such as 5’@T (2’R) + 2x10’@T (3’R) + 5’@T or 2x15’@T (4’R).
At my fittest I have been able to complete 40 minutes at threshold pace/intensity (between 160bpm and 170 bpm or zone 4) after a decent warm up.
I have used an example for a 37 minute 10k runner but the threshold effort or intensity applies to most levels. To the faster runners the effort is closer to what they would do for a half marathon whereas for runners with 10k times around 60 minutes, the threshold pace would be very similar to their 10k pace.
