If you swing a punch, is it ineffective? Actually no. It might not be the most efficient way of delivering a blow, but it can hurt. Many times martial artists get caught up some much in technical delivery that they forget that almost any blow can be effective. If you can put bodyweight behind it, it can hurt. Using boxing as an example, punches come in straight or curved. If you spar or fight, you will learn that almost any punch can hurt. So, keep in mind that fighting is not rocket science. Keep it simple.