People often suggest alternating 1 minute at 60% Heart Rate with 1 min at 90% HR or whatever but I find that it takes me almost a minute getting from 60% to 90% and another minute in reverse.
Therefore if if I do 6 cycles of 1 min at 60%, 1 min at 90% it takes me 24 minutets to complete rather than 12 minutes!

i.e. 6 CYCLES:

1 min getting HR from 60% to 90%
1 min with HR at 90%
1 min for HR to come back down to 60%
1 min with HR at 60%

How do other people factor all this into their routine or am I understanding the HIIT method all wrong?

Many Thanks

That's definiely an.....unique way of looking at it. Judging by heart rate it would probably take you about a minute and a half to 2 minutes to drop down to a low HR. If you can not, than you are probably like many others who are not ready for HIGH intensity interval training. No biggie, either you will have to lower the intensity or develop a stronger lactic acid energy system (trust me it is either one or the other).