There is an art to warming up the overhead. It takes skill, precision, dancing on the toes, and rhythm. When I am warming up with my practice partner or opponent, the overhead can be a great indicator of the level of player I am about to face. As like other strokes in the warmup, you are always trying to gather as much information from your opponent. Unlike other strokes, the overhead can quickly tell you a bigger chunk of the story and the truth about your opponent.
If you are returning someone's overhead and it is landing all over court, darting in 10 different location off of 10 different feeds, be careful. I really mean it, be careful. You can easily criss-cross your knees and involuntarily tweak a groin before the match even begins. Here are some simple signs of a poor overhead in warmup:
1) The ball is struck too hard. Veteran players do not hit overheads hard. In fact, they hit them very slow and relaxed. Trying to get a feel for the ball and swing. It's called a warmup. Plus, if you hit the ball too hard, how is your opponent going to bump the ball back? It takes two to warm-up your overhead.
2) You are warming up your volleys from seven feet behind the baseline. Think about that again, you (the lob feeder) are hitting balls out of the air to give them another overhead. Great way to break your knees in the warmup.
3) The overheader is making you run from side to side and up and back. Overheads should be hit within a reasonable 5 feet radius of the returner. All overheads should land at the service line. No exceptions!
4) The overheader needs more than 10 overheads to warm-up. If they can't feel good by 7, they are already considered a rookie.
5) The bounce off the ground should be a closer to 90 degrees than 0. You (the lob feeder) should be tapping lobs back from around your shoulder area, not your knee caps. Lobs made from knees or ankles are terrible overheads because they landed on the baseline. From a consistency point of view, this is too risky in a match.
Watch top junior boys, college players, or professionals warmup overheads. There is an art to a proper overhead. Now if you want to break some knees and injure your opponent's groin- keep swinging for the fences in 10 random locations.