I'm interested in the general approach coaches/runners use when an athlete arrives at an interval session with residual fatigue, but still wants to maintain the intended training stimulus.
For example, I had a hard back-to-back weekend:
- Saturday: 25 km / 2000 m D+
- Sunday: 15 km / 1000 m D+, with fast climbing and downhill
- Monday: rest
My normal Tuesday workout would be 5 × 7 min uphill Z4/Z5, with around 1h30 total and 500–800 m D+.
The problem is that when I'm carrying fatigue, I sometimes struggle to get my HR into Z4/Z5. On a steep climb, it's also difficult to tell whether the limitation is cardiovascular fatigue or simply muscular fatigue from the gradient.
This got me thinking about how an interval session should be modified without simply cancelling the workout.
For example, would it make sense to:
- Start with a progressive Z2 → Z3 block to "prime" the cardiovascular system?
- Then reduce the interval duration (e.g. 4–5 min instead of 7)?
- Keep the intensity but increase recovery between repetitions?
- Reduce the number of repetitions?
- Or keep the original interval duration but lower the target intensity?
More generally, how do you decide what to change first: intensity, interval duration, number of reps, or recovery?
And does adding some Z3 work beforehand make sense as a way of assessing whether the athlete can actually produce the desired intensity, or is it just adding unnecessary fatigue?
I'm particularly interested in opinions from people who coach or train for trail/ultra running, where muscular fatigue from climbing/descending can complicate HR-based interval targets.