Idk and this worked for me after a long slump and cranky knees. Treadmills felt loud, crowded, and weirdly stressful. The bike was boring at first and my heart rate monitor lied every other ride. Shoes and gadgets are stupid expensive for beginners and half of it solves nothing. I kept it cheap and simple because I was about to quit.
Five days a week, I did 5 minutes easy warm up, 20 minutes easy cardio, 5 minutes cool down. Easy meant I could hold a thread of conversation and breathe through my nose most of the time. Progress was adding 2 to 3 minutes to one day each week or a tiny gear bump while keeping breath steady. One practical tip that saved my knees was setting the bike seat high enough so my knee stayed slightly bent at the bottom. Timer on the phone, same time after dinner, no decisions to make.
