Threshold Test - is a quick workout to establish your Threshold Heart Rate or Power that will be used to set your training zones.
Description - Start with a 10 minute warm up at a steady pace with 3 bursts of 20 second efforts to get the body warm and the blood flowing. Kick into a high gear and deliver a maximum 30 second effort at high cadence followed by 2 minutes cruising. Repeat a further 3 times. After the final 2 minute recovery ease into a 20 minute time trial effort at at 'not comfortable' perceived effort and hold a consistent pace for the first 15 minutes. With 5 minutes to go try and increase the intensity, with 3 minutes to go try and 'empty out the tank' and go flat out. Enter the average wattage and /or average heart rate for the 20 minute interval in the boxes above and this will calculate your zones.
Tip - executed properly you should 'just' be able to get to the end of the 20 minute interval but dont go too hard too soon and blow up.