Why do you think that running will degrade your cycling?

If cycling is your primary sport, schedule your important (key) cycling sessions then make sure you don't do a hard or long run the day before that cycling session. Otherwise, your cycling workout will be compromised. I'm speaking as a 50+ year old so recovery is key for me.

Previous experience mostly. Also I find it hard to believe I'd be able to improve my cycling by cycling less and running more... Though I'm happy to be proved otherwise.

So don't cycle less. Add running into your training, with the runs placed appropriately in your schedule that still allows you to maximize your quality cycling workouts.

Okay. So this week's training as an example week:

Mon - Moderate - 2.5 hours (2hr tempo)

Tue - Recovery commutes - 2.5 hours

Wed - Easy with openers - 1.5 hours

Thu - Club 10m TT - 2 hours (inc. ride there + back)

Fri - Endurance - 4-5 hours

Sat - Off

Sun - Moderate - 4 hours (3hr tempo)

This is the final week of a block so pretty heavy before recovery next week. Also I have a lot of free time (student) but will be back to full time working in the next month. When would you add runs? After the tempo on Monday, race Thursday and tempo Sunday? Easy days easy, hard days hard and all that...

The bit I find hard is "placed appropriately in your schedule". Where would you suggest the runs go in the schedule posted above? Thanks

Do a moderate intensity run on Tuesday (whatever that might be). Run short (20-30 minutes) off the bike Friday (or Sunday). And do a long run on Saturday (again, whatever that might be for you).

There is plenty of room here to add easy running into this that will get you back to some amount of run fitness.

If you road race, there's no question for me that if I carry fatigue from running into key high intensity bike workouts it doesn't really work out optimally.

To answer his question, I either do an easier bike workout a day after running OR take an off day.

I don't go run for 75min one day and hop on the bike the next expecting to do 90min with some crit intervals or some 3x8's or something.

If you log both your run and bike TSS together, you can get an idea of what I'm talking about.

If you need to have a little rest or form to do a bike workout anyway because it's tough, don't expect to go running the day before and have it be any different.

If it were me, I'd organize it by what you want to do that week.

Run/bike mix week:
2.5 hrs run, 5 hrs bike..........all tempo and SS

Bike week:
just one or two 5k and then your normal bike stuff

Running degrades your cycling if it causes you to flunk out on planned HIIT workouts on the bike.

Ok if its a time thing I understand but there are a LOT of triathletes that are good at both.