Another metric we can use to base our prescription of intensity is of course pace. Pace is a great metric on flat terrain assuming no headwinds. If its windy then running into a strong headwind will significantly increase the metabolic effort to run the same pace compared to no wind or with a tailwind.
For flat runs in calm conditions, pace can be used though. As with any intensity metric it needs to be anchored to something. For pace the typical anchors we use are threshold pace, 10k pace or velocity VO2 max pace. Once we have determined an anchor point then we can use percentages of that pace to set the intensity of the various training sessions for our athletes.
Of course, as soon as it comes to hills, pace becomes irrelevant. The effort of maintaining the same pace running up a hill will be much harder than the same pace in the flat.
When it comes to downhill a few factors come into play.
– the downhill skill level of the runner
– the conditioning of ones legs ( especially quads ) to handle that pace
– the metabolic demands of running at that pace
This makes pace unusable as an intensity-defining metric on undulating terrain
For trails the additional challenges of rocks, mud, sand etc all mean pace will fluctuate a lot making it a useable metric to guide intensity.
Another metric that is a derivative of pace is grade-adjusted pace (GAP) . Strava has this and COROS have a similar metric called effort pace (EP) . It’s an attempt to give a pace when running uphill that is the metabolically equivalent pace to running on the flat. So for example you might be running uphill at 6min ks but it’s the equivalent intensity of running 5 min ks on the flat. In this way one can use GAP or EP and keep the intensity steady even on a hilly course.
Which sounds great in theory but as with any model we need to understand how those numbers are derived.
Strava bases its model on heart rate and pace data from literally millions of runs from its vast data base of runners. https://medium.com/strava-engineering/an-improved-gap-model-8b07ae8886c3 What the studies at Strava have done shows that for road runs on terrain that’s not particularly steep the model has a good degree of accuracy . Once you start moving onto steep and steeper terrain, the accuracy of the model starts to fall down.
Combine those steeper hills with trails with rocks, tree roots other obstacles to contend with, then the model is all but useless. So whilst it’s certainly a step in the right direction, for trail runners on steep terrain it’s not a metric that you can use that effectively to help guide intensity
COROS’s Effort pace model uses basically the same thing, but they use your individualized heart rate rather than the studies of millions of runs with the idea that is tailored specifically for you.
As with any model it relies on good data in to be able to produce good data out so if have good heart rate data and good GPS data it can work quite well with the same caveats that on steep terrain and on technical terrain it doesn’t work very well at all.
But if the GPS data is compromised then it may not be that accurate. Wrist heart rate obviously has its problems with accuracy on some people and some watches better than others.
So if the heart rate data is inaccurate, then the effort pace data’s will asp be inaccurate either. That’s not to say we can’t use metrics like effort pace, but you just need to understand that it may not be perfect and don’t take those numbers for gospel when you’re looking at the data afterwards. Have a think about is that number realistic or not? However on good terrain with good GPS cover and an accurate heart rate reading it can provide a useable metric help guide intensity.
Something to keep in mind with great adjusted pace and Effort Pace is from data I’ve seen it often depends a bit on the weight of the athlete. Often I will see that heavier runners struggle more up the hills for obvious reasons than lighter runners. What I see is those athletes are running slower up the hill for the same heart rate than what great adjusted pace or effort pace is saying. The extra weight means they can’t run as fast relative to someone who is much lighter. Flat running carries less of a weight penalty. So if you are coaching a heavier runner, be aware that the greater adjusted pace or effort pace may be getting them to run too fast uphills than what they should be running.
What we see on downhills is that your ability to run downhill is not just governed by how hard you’re working. The steeper the slope, the more two other factors come into play. One is your technique in running downhill and two is how well conditioned your quads are to handle downhill running.
If you take two athletes with the same fitness but one has done a lot more downhill running than the other you will find the downhill runner can run much faster for the same effort than the other runner.
So it’s important to think about how skillful your athlete is on downhills and adjust any guidance on downhill pace according to that. Otherwise they can be running too fast downhill which will increase the risk of injury due to the increased landing forces of running fast downhill.
One thing to keep in mind with running pace, great adjusted pace or effort. Pace is like every other training intensity metric. It is also affected by environmental conditions. What that means is on hot days, humid days running at higher altitude, the same speed or same effort pace will feel harder than running on cooler days or at low altitude. So you always have to consider the environmental conditions your athlete is running in and apply any corrections to the metric you’re using to prescribe their intensity.
There are other watches out there that will supply grade-adjusted pace , for example some of the newer Garmin models . So it can be useful metric, especially if you don’t have other metrics such as power, which is my personal favourite. It is significantly better than just pace alone, which is completely useless on any kind of hills or trails. It can be great when combined with rate of perceived exertion. Where the combination of objective data of great adjusted pace with the subjective data of how the athlete’s feeling gives a good balance of feedback for the athlete on intensity. But if you’re using GAP with your athletes, you have to educate your athlete on the limitations of GAP so they don’t start pushing themselves up too hard, up a really steep slope or running too fast down a really steep decline in order to try and keep their GAP where you’ve told them it should be.
It comes with an error margin and it’s up to you as the coach to look at the data and help guide your athlete on what that error margin might be and when they should use it and when they should ignore what the watch is saying.
In summary, pace by itself is a useless metric unless you’re running purely on the flat with very little wind around, grade-adjusted pace or effort pace can be quite useful if the hill isn’t too steep or technical.
As with any metric, we need to anchor pace to something and for pace, probably the best thing to anchor it to is either a recent 10K race if you’re in the 35 to 50 minute runner or a tested threshold pace.
Environmental conditions will affect pace and GAP just like any other metric. Pace should be adjusted to take into account hotter, more humid days or when running at elevation.