Answer: None of the above
All joking aside, can this question be more vague? If we follow the obvious, we would think about cardiovascular training.
Although I am not a big fan of the traditional cardio workouts on these types of machines, in my opinion, anybody who starts a training program can benefit from 10 to 20 minutes of sweat. It helps to build up cardiovascular capacity and to just get things going. What I don’t approve however is to overdo it. Spending a few months doing 30 minutes a day on a treadmill as the only means of working out is a waste of time. As with any type of activity, you become better, build strength and stamina. So doing the same thing, same intensity and speed days in and days out, is pure stupidity.
Don’t forget that after a few short weeks, you start losing weight and you gain endurance. So if you don’t increase the resistance or keep the same pace, you are actually doing less and making less progress than when you started.
But If I had to chose one? I would opt for the bike. I would even up the ante with the Assault bike a.k.a. airdyne.
This is by far one of the most effective cardio machine around. I love to do Tabata on the assault bike since you can really bring up the heart rate in a really short amount of time if you give it a go.
Same question (bike, elliptical or treadmill?) for fat loss purpose.
For those who follow my posts, you must already know my answer. I go for the most bang for your bucks equipment when it comes to getting results in the gym. Obviously, you can’t forget about diet, which is the main issue for fat loss. But, what you do in the gym, and how you do it, keeps the results coming.
Any piece of equipment, when used properly, can produce results. Do what you can with what you have and enjoy the results!