Speed training can really enhance any ultra endurance cycling training, but if you have never done it before and/or it's been a while since you have done any fast cycling it can be tricky to know where to start. I quite like using the stepped approach with athletes to (re)introduce speed into their training.
For people who are injury prone, new to speed work or coming back after serious illness/over-training a stepped approach can work well. This means that we gradually build intensity over time in a stepped approach and can move back to the last step that was working if things start to fall apart.
Zone 3 with reference to the table below zone 3 is just above your usual endurance power/speed. Fit athletes can sustain this pace for a long time (up to two hours) but a good place to start is just some longer efforts of 5-6 minutes at this intensity, building up to blocks of up to 20 minutes.
Zone 4 is around your Functional Threshold Power (the maximum speed/power you can maintain for about an hour). As with the previous step we would look to begin with efforts of around 5-6 minutes and build to blocks of up to 10 minutes.
Zone 5 are efforts above your Functional Threshold Power; they can be maintained for up to 5 minutes maximum. I usually start with efforts of up to 1 minute at this intensity and build to 3-5 minutes over time.
Once we have completed all 3 steps we might then choose to have a block focus in one of the three zones in which we look at building more time in that zone.
I would reserve zone 6 for athletes who will need some sprint power for their event and/or as a sharpener when athletes have achieved all the other key fitness criteria for their event.
An important aspect of speed work is that you will need to reduce your overall volume in order to account for the harder work. So you might find you are doing less miles or kilometres per week because you are doing more quality.
This is an important aspect of managing the training stress as you introduce intensity.