Indoor Interval Training Sessions Request

Looking at my power and heart rate zones, you would be looking at around the upper part of zone 4 HR for the 4 min intervals and lower part of zone 4 for the 2 x 20's.

That probably equates to around 90-92% on the 4 mins and 85% on the 2 x 20's. They're not supposed to be pleasant, but they are pretty effective for me at least.

As I said before, you need to account for the fact that your HR will creep up over the period of the interval for the same power.

I tend to do 6 x 4 at a set power, then next session 7 x 4 at the same power, then back to 6 x 4 but increase the power slightly, then 7 x 4 at the increased level etc.

you really don't want to have anything left in the tank at the end of the 2 x 20's but it takes a few sessions to get to the point where you know how hard you can go, as you want to hold the output steady for the whole interval so start a little lower and keep pushing harder each session until you find the threshold. The 5 mins in between really doesn't have the right to go so quickly!

The time honoured 2 x 20min intervals (5 mins rest between intervals) at FTP are a good session that fits in an hour

Also I like 7 x 4min intervals (1 min rest between intervals) at above FTP.

FTP is functional threshold power, and is basically the maximum power you can sustain for 1 hour (we are talking absolute max not just a hard pace)

Do the bikes have power measurements? I find power is a very good way of keeping the pressure on for this type of interval, as HR will tend to increase gradually over the interval for the same power output.