The one handed backhand is a simpler stroke than the forehand. If that doesn’t seem accurate to you, chances are you’re executing the shot incorrectly.
There are only a few fundamental tenets of the one-handed backhand, the first of which is something we’ve already discussed at length: The Fundamental Theorem of Tennis:
The racket and the forearm form a 90o angle, and the ball is contacted in front of the body.
The one-handed backhand is far less forgiving of late contact than the forehand is, so tracking the ball into a contact point well in front of the body is of pivotal importance.
There’s also less natural unwinding of the forearm-racket angle on the one-handed backhand than there is on the forehand. On the forehand, it’s very common to see the angle unwind from 90o at maximum wrist lag, to more like 135o by contact, and the wrist actually goes into flexion by the follow-through.
When striking the one-handed backhand, on the other hand, the 90o angle is typically maintained all the way through the swing and follow-through. This leads to a much more consistent string angle, and thereby a much more fault tolerant contact, than if the player were to allow their wrist angle to unwind.
The Upper Back is King
Elite one-handed backhands are driven primarily by the upper back and the abdominals, although some players, like Stan Wawrinka, occasionally add some hip rotation. That’s not super common, though, and hip rotation isn’t necessary to have a world class backhand. Many players, such as Roger Federer, hardly ever use hip rotation to power their backhands.
The simplest effective one-handed backhand utilizes almost solely the upper back to power the swing. It consists of turning away from the ball, barely pulling your racket back, and then using that strong upper back to drive your entire racket-arm system forward through the ball.
This can be performed flat, by simply driving the racket through the ball, or with some topspin, by driving the racket up and through the ball. On the simplest effective one-handed backhand, neither the hips nor the abs are used for racket speed generation.
Don’t Pull Your Elbow Forward
It’s very important that the one-handed backhand is driven primarily with the upper back and not with the weak muscles of the triceps. Many players, when they try to mimic what the swing looks like, instead pull forward with the (weak) muscles in their arms, leading with their elbow, instead of using their (strong) upper back musculature to drive the entire racket-arm system forward as a unit.
The Abs are Queen
Many players with elite one-handed backhands, such as Stan Wawrinka and Dennis Shapovalov, engage their abdominals on almost every backhand. This is done by turning the core away from the ball during preparation, and then unwinding towards the target during the forward swing.
Unlike on the forehand, the chest should not face the target at contact on the one-handed backhand. Even when the abs are used to power the swing, the chest will still typically face 90o away from the target by contact. This is because the optimal contact position for the one handed backhand is with the body sideways from the target, not facing it.
Typically, the non-hitting arm extends backwards to counter-balance the hitting arm during the swing, unlike on the forehand, on which both arms move together. The more abdominal rotation is used, the less you’ll see this counter-balancing effect, and the more biomechanically similar your forehand and backhand will be.
Adjusting to Contact
Just like on the forehand, adjustment should be made primarily by sitting lower with the legs and tilting the torso. This will allow you to drive a low backhand using the same muscles you use when driving a typical height backhand.
The best way to learn proper adjustment is to develop an understanding of what it feels like to drive the ball with your upper back, and once you get more advanced, with both your upper back and your abs.
Then, try to do that every time, even on awkward contact heights. Eventually, you’ll naturally start adjusting by sitting lower and angling your torso, because if you do anything else, you’ll have to fundamentally change the way you drive your swing.