Here is my crazy theory on how to do weight training without any weights. According to this theory, there is no need to go to gym for any weight training purpose. You can do anytime anywhere. No need for buying any equipment.
The theory is…
Every muscle in our body have another set of muscle that works in opposite direction. Ex: Biceps <=> Triceps,
I don’t know names of all those muscles, but you can check it yourself that you have two sets that work in opposite direction.
For example you want to do exercise for biceps, instead of weights (which just act as force in the opposite direction of your intended movement) just use your triceps muscle. So it will be like you imagining a heavy weight. But actually using your triceps to simulate that weight.
Your body does not know the difference between weight and your simulated weight. All it cares is about opposite force, no matter from where it is coming.
So same theory applies to all other muscles in your body. *I have used this theory and got a perfect body without going to gym. Now it is your turn to try.
[** it is lie, I have not tried it yet. It needs lot of mental patience to simulate the weights perfectly]