your instructor is wrong. elbos are more powerfull then punches the problem is most people dont know how to use them effectively. When you use elbo strikes up close you have to maintain the form that you would while throwing punches. Most people dont do that and thats why their elbos suck.
Elbos are a close combat weapon and quite frankly they are under utilized. Imagine this throw your elbows as you would throw a hook uppercut or right cross in the same manner except you retract your hand and only use the elbo. The amount of force is stronger then if you use your arm.
The reason behind that is because you are using the exact same muscles to generate force which is your back and legs but now you are swinging a more compact object around so the strike is more crisp. Also its harder to do damage with your hand because alot of times fighters will dissapate force when the hit doesnt land smoothely because of the wrist with the elbo its one solid blunt object.
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