Run Sessions

Power using Stryd or Garmin power is an algorithm that uses data from GPS and accelerometry to create a power figure. The number is a made-up number, which is why Garmin and Stryd's power numbers are vastly different. This doesn’t make them wrong, its just worth noting as you cannot compare them. Without going into a lot of details, Garmin's power is inferior to Stryd's as there is no factoring of wind or air resistance.

Power is a unit that reflects the work that is being done.

Pace/speed is a unit that tells you how fast you are moving over the ground.

Cyclists never use speed as a metric to gauge work, as there are a lot of factors that make it useless. Races, however are won by the fastest time, not the most work.

Swimmers only use pace as a measurement of work as anything else has until now proven to be very complicated.

Runners. Runners are in a funny place. Pace is so ingrained and simple to measure and it’s affected by fewer variables than cycling. But unless you're running on a flat road on a windless day, it’s still a pretty poor metric of work.

Pace is primarily affected by

• Surface

• Elevation

• Wind

So, how do you use pace to manage and prescribe training intensities and racing strategies?

Ideally, you don’t, you use power. But if you aren’t, it’s best they understand how training intensities work, and then we can make some educated guesses.

Why use power over pace?

We have found that running to power is a better gauge of the work being performed in sessions, which means we can quantify the training load better.

We have also found that once accustomed to how power works, runners are better able to pace their efforts in anything from LIA to VO2max efforts.

Pacing strategies for races are more relevant in power terms than in pace.

There is a lot written about training zones. All they really do is segment an athlete’s range of speeds into ranges where certain types of training are most effective.

In this chart, we have data from a lab test using 6-min stages increasing in intensity with each stage. Heart Rate oxygen uptake and Blood Lactate were measured during and at the end of each stage.

We have three key points identified

• Lactate Threshold 1

• Lactate Threshold 2

• Power/velocity at VO2max.

The parameters mark where there are significant shifts in physiology.

Below LT1 its’s all very aerobic; few carbs are being used, and fat is the primary energy source.

It's still aerobic between LT1 and LT2, but more carbs will be burnt to fuel the work (and consequently, less fat), which will only increase as LT2 approaches.

Between LT2 and pVO2max, carbs are burnt exclusively to fuel the exercise, and there will be a significant increase in hydrogen ions (the stuff that makes your muscles hurt) that will significantly reduce how long you can maintain that workload.

Over VO2max you require energy that you cannot achieve with the combustion of carbs alone, and you are accessing significant amounts of energy anaerobically (without oxygen). The higher you go, the less sustainable it is.

We are mainly interested in what’s happening below VO2max from a training and racing perspective.

VO2max and LT2 or FTP (whichever you use) are fairly easy to identify in the real world. Many of the devices (Garmin etc) we use give accurate figures for VO2max (but not necessarily the speed at VO2max, which would be much more useful).

LT1 is much more difficult to identify, and arguably, this is the most important one!

How are the zones established?

A big limitation of pace is in the definition of pacing zones. Most platforms define zones as a percentage of LT/FTP. This doesn’t work for many athletes. Those who are ‘faster’ runners will find their lower-intensity run pace is too fast and slower runners will find the paces set for lower-intensity runs are below walking pace. Slower runners have a much narrower range of paces available to them (the same is also true of swimming but that’s another topic).

The following is how we use and define the zones, we label them similarly to how we label session types.

Training zone terms and percentages of FTP/LT2