Start with a good warm up; 15 minutes progressing from Zone 1 into Zone 3, followed by 5 minutes easy spinning. The main session is 2 x 12 minutes, to be ridden as described below. Settle into a threshold pushing effort (same power from 'Session 4'), but after every 2 minutes ramp it up it for 30 seconds to a threshold pulling effort (Zone 5). Then back into pushing again. So, 2 mins steady-hard, then 30 seconds hard. Take 10 minutes easy spinning between the two sets. Warm down = 10 minutes easy Zone 1