“Bend your knees” is one of the most overused and oversimplified cues given not just in tennis, but in sports in general. When most coaches say “bend your knees,” they are trying to cue their student into some form of the basic athletic position: the hips are low and back while the lumbar spine is neutral. The athlete is slightly bent over via hinging at the the hips, and the posterior chain muscles (the glutes, hamstrings, and lower back) are lightly loaded and ready to facilitate explosive movements in any direction.
The problem is that “bend your knees” doesn’t cue most people into this position. Instead, it causes them to, of course, just bend their knees. They shift their weight forward onto their toes, decrease their knee angle, and bend forward with a rounded lower back to prevent from falling backwards. This posture deloads the hamstrings, glutes, and lower back musculature; precisely the opposite of what we wanted.
And unlike the athletic position, this forward-leaning rounded-back position leads to a striking lack of balance, coordination, and explosiveness. The body is in an even more compromised position than before the “bend your knees” cue was given – this alignment is a common cause of both knee and lower back pain.
“Sit Down and Back”
What the athlete should be doing is better described as “sitting down.” Sitting down causes the hips to shift down and back, the knees to track both out and sometimes forward, and a forward lean facilitated by hinging at the hips with a neutral, non-rounded lower back. Thus, by “sitting down” the athlete enters the athletic position, engaging the posterior chain and keeping their balance over either the middle of the foot, or the ball of it, depending on the situation. In the correct athletic position, the knees will bend, but for almost every student, that’s a result of entering the position, rather than the movement that caused them to enter it.
In no instance is the forward knee shearing, toe balancing position students (especially kids) get into upon “bend your knees” appropriate. Here’s the tricky part: after a student enters this position, their knees are in fact bent, so to the untrained eye it can look like the goal of the cue has been accomplished. If the thought process was as simple as: the knees aren’t bent, and they should be, then the coach may believe that the issue (which they perceived as nothing more than “straight legs”) has been fixed. The knees are now bent, after all; that particular joint angle has been “fixed.” But the underlying problem wasn’t actually addressed. The forward knee shearing, rounded back, toe balanced position that most students enter upon “bend your knees” is not the athletic position. We can only hope the coach notices the flaw, back peddles from the “bend your knees” cue, and finds a different way to get the student into the athletic position.
Proprioceptive Awareness Fosters Long Term Success
The entire mess can be avoided if, instead of naively cuing “bend the knees,” we teach our athletes how to proprioceptively feel the athletic position (perhaps the most important static position in tennis). They need to know what it feels like to have their posterior chain loaded, their back flat and hinged at the hips, and, yes, also a smaller knee angle. They need to recognize the sensation of being primed and ready to support explosive movements in any direction; this proprioceptive awareness will improve their balance and athleticism across all sports, not just tennis.
Again, the “bend the knees” cue will not give athletes this awareness, because “bent knees” is just one of many biomechanical changes a person previously unfamiliar with the position will have to take to correctly in order to enter it. “Sit back” or “sit down and back” are far superior cues. Most students will already have an idea of how to coordinate their body to perform a “sit” action, and this cue will hijack that awareness. Notice that “sit” is a human movement, while “bent knees” is a single joint angle.
Joint Angles Are Secondary
Typically, a single joint angle is a symptom, not a cause. It’s not that the “knees aren’t bent,” it’s that the athlete is standing up straight instead of sitting. It’s not that the “hips aren’t square at contact,” it’s that the athlete doesn’t know they’re supposed to be twisting as they swing. You’ll be amazed at how many individual limb placements and joint angles your student will fix on their own, without you having to mention them specifically, just because they’re trying to do something like “twist” or “throw.”
In general, cuing a movement pattern is far more effective than cuing a joint angle. “Twist,” “jump,” “throw,” “sit,” “lunge.” Start broad, then work to narrow as it becomes clear what the athlete’s particular hangups with the movement pattern are. We don’t cue an individual body part until it’s clear that that body part is the critical missing link in an otherwise functional process. Cuing joint angles is for getting the athlete’s movement pattern the last 20% of the way there, and certainly not for getting a kid unfamiliar with the athletic position into it for the first time.