The prone incline curl effectively stimulates the biceps, along with the other arm flexor muscles whilst eliminating the ability of the athlete to use assistive muscle groups or body movement to help curl the weight.
An interesting element of the prone curl is the role the two biceps heads play. Unlike traditional arm curls, the short (inner) head of the biceps is more or less muted during the curl due to what is known as active insufficiency, therefore placing the majority of the stress onto the long (outer) biceps head. This may be the reason as to why many bodybuilders have reported the prone curl being highly effective for developing the “peak” of the biceps, although we must remember the shape of the biceps is mostly based on your genetics.
A barbell, EZ bar, set of dumbbells or cable pulley are all suitable for the prone curl, allowing for various grips to be experimented with. Remember, using a neutral (palms facing towards each other) or pronated (palms facing down) grip will reduce the biceps activity during a curl and place greater emphasis on the other arm flexor muscles.