Thursday Training Theme: This week’s favourite training session

polar-m600-trainingTheme: Threshold

I treat this session as an alternative to the standard 2×20′ session and it has other benefits too. It consists of 3 series of 90-second intervals at FTP and is perhaps not as hard as it looks because the 30-second recovery before each 90 second effort period significantly helps the ease-of-execution.

For example, instead of this session, today I was contemplating doing 2×20′ @85-90% FTP and I probably would have found the 2×20 the harder of the two workouts; although that probably reflects a bit of a collapse in my threshold abilities in recent years and a simultaneous motivational increase towards working much harder on shorter efforts aka my friends tend to do hills and I tag along for the ride.

I was also bringing in a little bit of fatigue to the workout but nothing crazy.

Workout Details

Here is the FTP Boosting Session: warmup followed by 3x [7x{30secs@Z1, 90secs@FTP} 8′ RI]

Duration: about 80 minutes if you include a proper warmup

A bit of simple maths sees you staying at FTP for over 30 minutes in total.

Workout Results From Different Perspectives

Xert’s View

My automatic FTP, calculated in Xert and used in the chart below, is perhaps 10-20w lower than reality, although it’s normally ‘about right’.

Here are the results according to Xert and, surprisingly to me, the workout virtually never ate into my maximum power available (MPA, not shown).

RPE View

I’d say the session felt uncomfortable a lot of the time; probably overall it was 6 out of 10 based on my breathing based on these training zones.

Humon Hex view and SmO2

The effort periods seemed to require me to spend a lot of time in the RED zone according to Humon Hex and the following chart probably reflects exactly how I felt and is based on SmO2 data from the Hex.

Looking at Humon’s SmO2 data as SmO2 zones (now shown in Garmin Connect), I get the following chart which clearly shows Z4/Z4 SmO2 efforts

Yet, as I say, by the end I didn’t feel all that tired and could have gone harder. Sure the workout is not designed to be a maximal effort but it felt a tad easier than it should

HR Zones in Golden Cheetah

I created the workout on Training Peaks using %ages of FTP rather than absolute amounts to define the effort periods, that way I will be able to re-use the workout. Of course, this then relies on the FTP being correct on the Wahoo (which I think it is). I reckon an additional 10w would actually have got my heart rate up to the higher echelons in HR Zone 4. As the actual Golden Cheetah chart shows this was a solid Zone 3 session by heart rate, where really much of the last 2 lots of 7 effort periods should have had quite a lot of Zone 4 time (but didn’t)

Q: Why is there a mismatch of data from the different zones?

I’ve perhaps not explained that too well. But I’d summarise some of the stats like this

  • power was supposedly at the upper end of Z4, assuming the FTP is right. But FTP was probably about 10-15w too low, small in percentage terms
  • If the FTP was right I think I still would have found 2×20@90%FTP quite a bit harder than this session
  • heart rate shows a clear Z3 workout
  • SmO2 was easily in Z4

My interpretation of the stats from this workout is that

  1. I seem to be able to deliver oxygen but not use it. Therefore I should get down to the gym more often
  2. I should do more threshold workouts than I do
  3. Training Zones don’t always match one another in any case.



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