Basically the title? Did anyone have success with such a training method? I recently fell in love with running. I live near mountain trail surrounded by 2-2.9k meters mountain peaks. It’s surrounded by three mountains actually. Love it! I was wondering if I can substitute zone 2 rides with runs? Are there similar adaptations? It should be in my opinion as both running and cycling in that zones is increasing mitochondria. I get it, running will not make me faster on the bike. I studied physiology in university 10 years ago, but not deep enough to answer my own question. Is running increasing mitochondria in different muscles than cycling? I am a bit confused. Maybe I will need less volume with zone 2 running than cycling to see any improvements, as running is harder.
Nah I’d plan your runs and rides separately. ‘Replacing’ a 1 hour zone 2 ride with a 1 hour run just doesn’t make sense due to how much wear and tear running does to your body.
Check out barryp’s triathlon run plan (google it-- it’s on slowtwitch.com forums) and switch to a triathlon-focused bike plan on trainerroad. Your Tri bike plan will have fewer z2 rides and fewer rides overall, but plenty of intensity 
There’s two ways of looking at it:
- Run to be a better runner. Ride the bike to be a better cyclist.
- Fitness is fitness.
There’s something said for specificity… but fitness does carry over. Back in my 20’s when I was skinny, running 100 mile weeks and could run a sub 30 min 10k, I would crush the hills drawing all kinds of praise on the local MTB ride. That is until they all passed me on the downhill and saw how soft I was. 
As a coach I often get swimmers and soccer players out to run cross country. They absolutely crushed it!
But at the pointy end… it is those who are wholly committed to that singular goal.
That said very few are at the pointy end. Life is short and am all for doing what you love. If you find enjoyment in running your local trails do it!
Different muscles.
Generally it is accepted that cycling improves running, but running doesn’t improve cycling.
There’s a running thread and many triathlon threads you might get good direction from.
Keep your running short and easy, and progress volume slowly.
Maybe if you are not good at running. But elite runners I know can transfer over to the bike quite well.
That’s not quite the same thing. The general fitness from other sports will carry to a degree.
Improving cycling will come from training cycling, hardly at all from training running. What will come from running will be increased fatigue and injury risk.
Not my words, I’m just the messenger here.
I did running only for a long time and was good at it (could keep a fast pace - felt great).
I did cycling and running half/half for a year (bc of injury and to see if I would like this variety) and sucked at both in pace for running and power for cycling (however, had amazing endurance).
I’m cycling only since the end of last year and getting good at it (FTP going up).
Moral of my story: If you like both and enjoyment, fitness is your aim: do both. If you want to be good at one, just do that one.
I mix both (2x-3x bike and 1x run a week). However, my primary objective is to stay active and maintain a healthy lifestyle. No racing whatsoever (only with my past-self). 
Thinking about the same thing. Currently doing 4 rides per week, but want to add 1x run per week instead of a 1h zone z2 ride.
How would you update the TR training plan. Remove the 4th week or just replace the 4th ride with a run? 
Hi there, I started this thread before year and a half, so I can share some experience now.
I fell in love with trail running. Cycling is still my primary sport. I did about 100 runs since I started this topic. At the begging I had the cardio of a horse from cycling, but knee pain and discomfort were my limiter due to various reasons . It took long time to address problems.
I incorporated more strength training for my lower body. I got ITB flares and etc due to weak glutes.
Instead of running longer running shorter, but more frequent helps with adaptation of tissues. Thats was my main problem and after talking to a ultra trail marathon runner who frequently does 50-100k + miles races I was convinced that my joints and tissues do not have sufficient time to adapt to the stress of running. What would do 6x5k runs a month to a tissues? Thats what he asked me? barely nothing. As you may already know joints, ligaments ITBs and other tissues need months and years to adapt, that was my case. I was not running enough to make my tissues to go in “strengthening mode” instead they are always in “repair mode” since the stress is present for short time and its induced again after 5-6 days. You can check Wulfs law for load management and tissues adaptations. If you have problem with knees consider the mention thing above.
My advices are:
- go slower and shorter at the begging. You will have the cardio of Ferrari from cycling and chassis of retro car, that can’t handle the speed of engine.
- do more runs. Sometimes I do recovery run in off days 15-20 mins just to remind my knees that they are in “strengthening mode”
if you do strength training incorporate more lower body. This will help cycling and running.
Generally running will not make you better cyclist, but will make you better athlete. You will get general adaptations from running like increase in Vo2 max, increase hearth stroke, increased blood volume, some muscle endurance and more bone density. Thats enough for healthier life. I now do 50% cycling and 50% running plus strength training. I will not win races and it’s not my goal in life to do so. Just like cycling running is great for mental health. Sometimes I get bored from cycling around and there comes running to make my life a bit funnier.
Good luck.
I miss being able to run. But I’ve found MTB gives me much of what I miss from running.
Thank you very much for sharing your experience. 
I’m in the exact same situation as you was. I have to take things really slow.. currently just jogging/walking and increasing the length of jogging for each time, but just increased to 5min jog / 2 min walk x 3 and 3rd interval I had to stop and just walk as knee was hurting 
it’s hard not to be 20 anymore…Im sure things will come with patience. At least I’m motivated to do both cycling and include a bit of running before my strength training sessions 1-2 times per week.