The TRUTH about Cardiovascular Training (Cardio)
If it comes to cardio, I personally recommend two types. High-Intensity Interval Training (HIIT) and Low-intensity Steady State cardio (LISS). Benefits of cardio include increased ability to utilize oxygen efficiently, improved blood flow thus more circulating androgen levels.
Any kind of endurance, aerobic (with oxygen) cardio should be avoided, to eliminate all risk of chronic cortisol (stress hormone) elevation from training. It does nothing to help you and thus should be avoided. Running generally reduces your metabolism. Look at marathon runners, they are skinny and lack of muscle. Their heart rate is low as well, which is a sign of low metabolism. Just think about it. Your heart adapts in a way so that you preserve as much energy possible so that you can finish the race.
Walking is an example of LISS
Walking is a great thing to do for your body, I recommend getting in about 45-60 min of walking per day or 10k steps. Walking is great for reducing cortisol and clearing your mind. Thus leading to better recovery.
Sprinting is an example of HIIT
Sprinting is great for increasing testosterone production. Look at sprinters, they are all jacked. Their physiques are a testament to the power of the explosive movements to increase circulating androgens which impact muscle density, neural power, and low body fat levels. If you do consider doing this, perform it once a week as it too counts as proper training due to the nervous system fatigue, so be cautious of your recovery. When you begin the program, I wouldn't recommend sprinting initially but after 3 weeks you can introduce sprinting.