I know its boring on the turbo but try this, it's a fun session on cold winter evenings in january and the time flys past.
O/UT = Over Under Threshold (a heart rate which fluctuates slightly a few beats above and below your threshold or TT Heart Rate)
O/UT PYRAMID
10 mins warm up
1 min @ O/UT
1 min @ EASY SPIN
2 min @ O/UT
2 min @ EASY SPIN
3 min @ O/UT
3 min @ EASY SPIN
4 min @ O/UT
4 min @ EASY SPIN
5 min @ O/UT
5 min @ EASY SPIN
4 min @ O/UT
4 min @ EASY SPIN
3 min @ O/UT
3 min @ EASY SPIN
2 min @ O/UT
2 min @ EASY SPIN
1 min @ O/UT
1 min @ EASY SPIN
10 mins warm down
Total - 1hr 10mins
*The O/UT intervals start from when you start to ramp up the pace, not when you reach the Threshold heart rate - take about 30-45 secs to build up to it on each interval.
When I'm in the middle of the 4-5-4 bit I always feel like giving up cycling