Hey Guys
I train 6x a week. I am in my first month of base so I its all Z2. Weekday 90min - 2hours. Weekend 3-5 hours.
I want to replace 2 of my rides with runs. A 45minute run and one long run going up to 2 hours. I run on the trails and walk up the hills so its all Z2. Right now I am at 30minutes of running and I am adding 5-10min per week.
Thoughts?
I’d say go for it if that’s what you’d like, but I wouldn’t expect a 1:1 effect.
From my personal experience, cycling has a very large carryover to my running performance but vice versa the effect is much smaller. I ran my fastest 10K on 90% cycling, yet when I ditched cycling for my marathon training (~4 months) my cycling fitness went down real fast.
My personal experince run training doesnt carry over to the bike but bike training does carry over to running.
Might just be me though, having said that I know many people that have experienced the same.
Ha. Just posted very similar, that is what I find.
I lost ~40 watts of my threshold Marathon training even though I was still cycling 3 times a week.
It depends, running is much harder on the body, if you are not used to running for a long time it will take a long time to build up to doing enough volume to make a difference to your fitness.
A 45m Z2 run is only going to be equivalent to a 45 Z2 ride.
Having said that I found that when I added in some extra Z2 volume on top of my normal plan with a 30-40minute run on my lunch break a few times a week I did see improvements.
x3.
But as long as you’re aware of the impacts/limitations, there’s no reason not to add running, if that’s what you want to do.
I’ll be adding running back into my schedule starting in September, with some 5 mile trail races in the late Fall.
If you are a cyclist, your fitness carries over to running (but cycling fitness decreases a bit).
If you a runner, your fitness carries over to cycling (but your running fitness decreases a bit).
If you run and wear ankle socks while cycling, you are a triathlete. 
When training heart and lungs (central adaptations) you can benefit from running but it is not beneficial for any periferal adaptations (increased mitochondrial density and function along with increased in capillarization) as it is sports specific.
I wouldn’t replace my z2 rides with running as my priority is cycling. VO2max intervals is a distinct maybe…You may have different priorities.
If you want to build up slow without having an immediate big drop-off in overall volume, you could consider starting by doing them as short brick runs off the bike, then only drop the cycling workouts once they get a bit longer.
What I experienced is: especially when starting where I live, in the city, I am a lot easier a lot more in m desired HR zone while running, while with cycling, the first / last 10min are always kind of on/off.
My assumption is, that I have a better time in zone ratio plus the impact of running (e.g. better bone density), that’s why I try to include it every week to every two weeks.
I can’t for the life of me run at z2 HR. I’ll stay there for a mile or so and I’m lucky to see under 155-160 the rest of the time (max hr 202). I’m sure this is a fancy way of saying “I ain’t a runner and dont know Jack about how to properly run”
100% yes! As others have said, you might not be quite as fast a cyclist, but you’ll be a healthier and stronger human!