I imagine for many people if you’re told to get fit the first thing that comes to mind is some form of cardio such as running, maybe cycling etc.
Now I’m a great believer in having a decent baseline of cardio fitness for lung and heart health long term, and in case you get chased by a bear…….However will that necessarily improve your riding?
If you’re out of breath when riding and generally flagging before your lesson has finished then yes that is something that needs to be addressed. If you are perhaps riding X Country and are out of breath struggling to ride strong and alert right to the finish then yes you need to improve your cardio fitness.
For that aiming to run 5k, maybe cycling 10k or doing a dance class whatever gets your heart rate up and you will actually enjoy and stick to is fine. There can be arguments either way for which method is best so honestly I think you should just find something you will enjoy and therefore keep doing it.
However, if you have never felt yourself flagging during a lesson, you don’t get out of breath after some sustained rising trot then taking up running will not necessarily have a huge impact on your riding, you’d be better off looking at improving your strength and stability to make an impact.
I’m not saying don’t take up running or whatever as people run for different reasons other than fitness. If doing some cardio makes you feel good (runners high is real) then absolutely go for it.Maybe it clears your head and makes you feel better overall then that’s great. That’s why I do cardio, it helps burn some calories for weight management and makes me feel more energetic overall.
What I’m trying to say is some form of cardio is a great addition to a healthy lifestyle but unless you do get out of breath riding or struggling to up your game for lack of stamina then it won’t necessarily improve your performance on its or struggle to up your game for lack of stamina then it won’t necessarily improve your performance on its own. If you want to improve your riding off horse there’s other areas such as stability, force absorption and pro prioception you could start with.