A weightlifter rubs powder in the hands before lifting a weight so as to increase the amount of friction in between the hands and the rod. This helps the lifter to have a better grip on the rod.

How can the amount of friction increase if powder is applied? Isnt it a lubricant?

Weightlifter generally dust their hands by chalk powder to absorb sweat and improve their grip strength by increasing friction between the hands and the rod. The type of chalk powder used by weightlifters is called magnesium carbonate, a white solid that occurs in nature as a mineral.Magnesium carbonate is greatly different from the chalk used on sidewalks and blackboards. It is also different from the talcum powder and baby powder. Talcum powder or baby powder acts as a dry lubricant and absorbs sweat from hands, but they decreases the friction between the rod and hands.