aside from being more challenging for your core compared to lying windshield wipers, it really helps with forearm and biceps development and decompressing your spine. even doing lying windshield wipers requires you to be a little bit more advanced so it means the hanging variation is only for professionals. avoid going fast and to extreme ranges, do not just bring the knee up without raising the hip as well, and avoid keeping your arm fully straight(make sure you bend the elbow a little bit).