Since you spent a whole lot of time and effort trying to build the muscle mass you have, it would really be disappointing if suddenly it was diminishing as a results of the excess cardio you’re doing. This is a bit mistake among a lot of novices, who dive in head first on the cardio in hope to lose body fat, but end up losing more muscle mass, and gaining fat! It’s sad but a very real aspect of training for specific events.
There is always a risk when you implement cardio for fat loss, instead of watching your nutrition a lot more carefully. It’s hard enough keeping muscle mass on with food changes in itself. Throw in the endless cardio, and you have a recipe for disaster.
If you must do some form of cardio, I suggest HIIT a couple of times a week for no longer than 20 minutes at a time. That would need to be monitored very closely for loss in muscle mass.
For a more relaxed, ideal approach, I would suggest walking as a form of cardio. I know it’s a good old fashioned body building strategy, but it works very well, and you won’t lose any muscle mass in the process.
But here is the deal though, it’s give an take with either. You are going to have to do some trialing and testing on yourself. Let me give you one more successful strategy to proceed with cautiously..
Intermittent fasting!
One of the best ways to lose body fat fast, and keep on putting muscle mass. The only thing with this is that you really must eat enough protein, which can be hard with the restricted eating phases. What I would suggest with this is to start small, say a 12 hour fasting window, and shrink it accordingly. If you start seeing yourself losing mass, then scale it back, or only fast for a few days per week.
This strategy works so well, you won’t even have to think of cardio, let alone perform any. This is a win, win all round. Just monitor closely and tweak.
I found this to be the best strategy, given that you trigger human growth hormone to build muscle and burn body fat at the same time. Your metabolism magnifies, and you will become a bit of a fat burning machine! The results are wonderful, and worth the restricted eating phases.
I hope this answers your question, and helps you make a more informed, and more strategic outcome to your issue. Feel free to contact me any time on my website or join me on fb and insta social. Please feel free to upvote this answer if it has been useful in some way to you.