Does cardio fitness transfer across exercises?
Cardiovascular adaptions do carry across diferent types of cardiovascular activities.
Carry over from improvements such as increased mitochondrial density in muscle fibres, which allows muscles to produce energy more efficiently, depends on the similarity of muscles used between the exercises.
Increased mitochondrial density in the calves from running will help bike riding more than it will swimming, although it will probably help your kicking.
To answer the question, yes, the cardiovascular benefits will carry across to other types of cardio to some degree.
However, the extent of carry over will depend on the similarity of the exercises and subsequent adaptations.
Running isn’t the best way to become a better swimmer, but someone who can run 10km will swim further than someone who cannot run 10km, if both people are equally untrained swimmers.
Mental toughness almost carries over completely, which is often forgotten.
The ability to push through tough training, whether it be burning lungs or muscles, or internally questioning whether to stop or not, carries across different types of training.
You begin to develop strategies to manage these thoughts and pain, some people even get to the point where they begin to enjoy it (the challenge, not the pain).
I personally find this true when doing high-intensity work - I can look back to longer duration work and tell myself that this is significantly shorter and then push through.
On the flipside, there are times towards the back end of a run or something like that when I want to stop and walk, but I can think back to a really tough rowing session that had me on the ground for the 30-minutes after
I often think back to when I had all of my clients do a 30-second max effort sled push in the gym.
It was a Saturday, so I had eight sessions that day, and every single person who did this all-out exercise was thoroughly exhausted.
I had a two-hour gap between my second-last and final session, so I decided to give the session a go and see what all the fuss was about.
Remember: 30 seconds of pushing a sled (all out) - that was it.
Afterwards, I was so fried that I lay on the ground for 30-minutes.
I decided to walk around the block to get some air - I made it 30-meters and turned around, setting up camp in the shower for the next 30 minutes.
Even though I carried on more than any client who did the session that day, I still look back on that session and recall the absolute fatigue.
So when I’m nearing the end of a longer, lower-intensity running session it’s easy to think of that and push through.
It doesn’t work all of the time, but it’s a handy tool to have when looking to maintain the effort.