Q: Mike, when exactly and why should one wear a weightlifting belt? How exactly does it help and for what exercises should it be used?

A: This is a tricky subject. Simple answer is that you should wear the belt if your doctor or therapist tells you to :)

It may be necessary if you have a back condition (which may be diagnosed by your doctor or physical therapist as I indicated above). But aside from that, a weighttraining belt is basically a crutch for you, taking off some of the work normally done by your lower back and abdominal muscles. Using it all the time leads to chronic underdevelopment of those muscles which may in turn lead to injuries during weight training and/or normal activities.

A belt can also let you get away (temporarily at least) with using poor form on exercises such as squats, but sooner or later the poor form will catch up with you. As always, make sure that you learn and ALWAYS maintain good form above all else.

So my recommendation is to not use the belt unless your doctor tells you to. If you have aches and pains in lower back, you should ideally see your doctor/therapist or, if that's not an option, at least take it easy and rest until the injury fully heals (and restart with light exercises instead of jumping right away to your old heavy weights). Do NOT get into the habit of using belt just because it feels easier or more comfortable -- only do so if a professional recommends it.

I should also say that the belt only serves its purpose when doing compound lower-body exercises, such as olympic lifts, squats, and deadlifts -- it serves absolutely no purpose for things like bicep curls.