Marines have been given approval to let their hair down -- at least some of it -- while they work out. Women with medium-length hair are now allowed to wear a "half ponytail" hairstyle during physical training. The style, which pulls the top portion of the hair away from the face and into a ponytail while the rest of the hair remains down -- is one of several new uniform-related changes the commandant signed off on this week. Read more on Military.com.