If I do cardio, will that help build muscle or hurt when the muscles need rest?

I wanted to know if you think it's a good idea to do cardio training on my off days.

Answer:

Doing some light cardio work such as walking or cycling is not going to hinder your muscle gain goals. Doing too much cardio work or going too hard during your cardio work will, in fact, hinder your muscle gain.

There are several reasons for this. In order to gain muscle, you need to eat more calories than your body burns. If you do a lot of cardio work, you are burning a lot of calories that your body could be using to build muscle.

The other reason is that hard cardiovascular training can increase breakdown of the muscle tissue you already have without providing a reason for your body to build bigger muscles, as in weight training. By forcing your body to recover from hard cardio training, you essentially decrease the available resources your body has for building muscle.

I would recommend sticking to 2 days a week of light cardio training for about 20 to 30 minutes per session. Use this is as more of a cardiovascular maintenance type training rather than really trying to improve your fitness otherwise you may limit your muscle gain.

If you want to really improve your cardio, then you should focus your training on that. It is always easier to train towards one goal rather than two goals.