Don't think that 15 minutes of warm-up is unnecessary. 15 minutes is the basic time for effective warm-up. Some experts even warm up for more than 30 minutes. Effective warm-up is the basis to ensure the training effect.

But you don't have to run to warm up. I think if your training is centered on the bodybuilding training system, then there is no need to warm up by running. It really depends on personal habits. The really necessary warm-up is foam shaft relaxation, static stretching and dynamic warm-up.