The Tennis Shoulder: What Happens During the Follow-Through & How to Train It
There’s no question the shoulder takes a beating in tennis. I mean, players use it on every shot. Whether that’s to create lots of torque to hit a big forehand or to stabilize the shoulder when punching a volley...the shoulder has many functions and roles. But perhaps the biggest toll on the shoulder occurs in a movement you wouldn’t normally consider...the deceleration phase (aka the follow-through phase) of the serve. This is the moment after impact where the posterior muscles of the shoulder act in an eccentric manner to essentially stop the head of the humerus from being dislodged from the glenoid fossa (aka think arm dislocating from shoulder...that wouldn’t be fun). Ellenbecker & Kovacs (2008) call the deceleration phase “the most violent of the tennis serve”. That’s a pretty big statement, and probably something that needs to be considered in the training of the tennis shoulder. But why exactly is this phase of the serve so critical? What type of strength is necessary? And what kind of exercises can tennis players incorporate into their program to optimize the serve & keep the shoulder healthy? We’ll explore all of these points in this article, so read on.
The Stressed-out Shoulder in Tennis
When analyzing the shoulder in tennis, it’s important to know some of it's key characteristics during the serve - specifically, the deceleration phase. Before we continue, it's worth noting that the serve produces the most stress on the shoulder of any stroke in tennis. It has the highest muscle activity and generates the highest internal forces compared to all other strokes.
Here are some specifics. Immediately after ball impact, the posterior muscles of the shoulder along with serratus anterior, biceps brachii, deltoid and latissimus dorsi, are all working to decelerate the arm. That’s not to say the internal rotators aren’t working, because they are, otherwise the racquet would stop dead in it’s tracks right at impact. But the muscles during the deceleration phase contract eccentrically (this is important so remember it!), and are more active than the internal rotators that are contracting concentrically. Learn more about contraction types here. This eccentric contraction of the posterior shoulder muscles helps prevent excessive distraction and possible injury.
But how much stress is actually placed on the glenohumeral joint (main shoulder joint during serving/throwing) during this phase? Well, Fleisig (1995) stated that forces acting on the this joint during the acceleration and follow-through phases were as much as 1x a player’s bodyweight. Think about that the next time you’re hitting the gym or putting a program together. WE CANNOT neglect upper-body strength & power work, especially in muscles that are active during the serve...like the barbell pullover, dumbbell bench press, a variety of shoulder specific work and probably most importantly, PLYOMETRIC EXERCISES of the shoulder complex. Sit tight we’ll get to the exercises.
Furthermore, the internal rotators can have max speeds during the serve that measure up to 3000 degrees/s (this is what's been measured but I believe modern players produce even higher speeds). Just less than half of what a maximum throw or pitch in baseball would produce. So it does take a good amount of strength to decelerate the shoulder, especially considering the speeds were dealing with.
What Does this Repetitive High-Speed Serving Do to the Shoulder?
The repetitive stresses that take their toll on the shoulder are apparent when looking at both strength levels as well as range of motion & flexibility. In terms of flexibility, that’s a whole other topic that we’ll save for it’s own blog post down the line.
As for strength aspects of the serve. When testing the strength of the shoulder, researchers found, not surprisingly, that there was an increased ratio of internal rotation strength when comparing the dominant vs non-dominant arm. So serving increases internal rotation strength. That’s something we should be aware of in terms of training as well, especially considering that a recent study found a high correlation between internal rotation isometric strength and serve speed - players who had greater internal rotation strength served faster (Baiget 2016)! I outlined the importance of serve speed and how to train it in a previous post - you can check that out here.
However, what may be more important in terms of injury prevention and long-term success of the serving shoulder is the strength ratio between the internal and external rotators. Using an isokinetic assessment protocol, researchers tested strength levels of the internal & external rotators (Ellenbecker 2003). What did they find? A big fat difference between the two. There appears to be a strength deficit of the external rotators.
Of course to some degree this muscle imbalance is normal when it comes to the tennis player. Just like pitchers in baseball, to be able to throw fast or serve big, the internal rotators have to be strong enough to produce high velocities. However, the same researchers noted that a recommended external/internal rotation ratio should be around 66-75% - in other words, the external rotators should be AT LEAST 2/3 the strength of the internal rotators. BUT...when testing over 100 elite players from the ages of 12-21, they noticed that the average ratio was only 50% (or 1/2). This can lead to a host of issues like impingement, joint instability, tendonosis etc. I think it’s safe to say that tennis players should train the decelerators.
How to Minimize the Stress on Shoulder
Before we move on to some of the exercises, let’s quickly look at how to minimize the stress on the shoulder during the serve. The most effective way to decrease stress in the posterior shoulder during the deceleration phase is by improving serve mechanics. Researchers found that less skilled players actually had greater muscular contributions at the shoulder, likely due to an improper use of the kinetic chain - i.e. these players, compared to skilled players, have difficulties synchronizing the lower body with upper body to generate efficient power and stroke mechanics. They end up overusing and fatiguing the muscles of the shoulder....which is probably why most shoulder (& elbow) injuries in tennis occur in recreational players.
How To Train the Decelerators to Protect the Tennis Shoulder
Whether mechanics are sound or not, it’s critical for players to train the decelerators in effective ways to protect the shoulder from injury...and to optimize function for practice & competition.
Training the posterior shoulder provides important muscle balance to the tennis player (or near muscle balance as perfect muscle balance DOES NOT exist). Traditionally, players are deficient in these decelerator muscles primarily because they don’t train them.
So how exactly do we train them? Although I believe resistance band exercises can be very helpful when warming up or training the posterior shoulder* (especially when coming off an injury), they aren’t dynamic enough and don’t have the ballistic quality that’s required, and that’s seen during the service motion. Similarly, traditional strength exercises are vital - I mean we saw earlier that the shoulder can be under high forces during the serve - but again, they aren’t specific enough to the velocity demands of serving. It is therefore important to train the shoulder in a repetitive fashion but also explosively (to build power endurance). That’s why plyometric exercises that require a rapid stretch and subsequent contraction of the shoulder are recommended (and not just by me, but by researchers too).
*Here’s a great band exercise by Mike Reinold’s - Mike is a shoulder specialist and has worked with a plethora of overhead athletes.
Below are 4 plyometric ball exercises that can be utilized. They progress from less intense to more intense and should be incorporated into every player’s training and warm-up protocols.
Exercise 1 - Side-Lying External Rotation Toss
This exercise is the least taxing on the posterior shoulder partly due to the fact that you’re positioned in such a way that’s less favourable in terms of producing high speeds and power. Using a lighter ball to start is preferable (500g or less).
Exercise 2 - Standing Vertical Eccentric Flip
With this movement we're starting to get more ballistic by utilizing a greater stretch of the internal rotators. Keep in mind that the higher the toss or the greater the weight of the ball, the more stress is placed on the decelerators when CATCHING.
Here are 2 more ballistic, higher intensity exercises for the tennis shoulder:
Exercise 3 - Reverse Throws
Although this exercise doesn't really train the eccentric/deceleration component of the posterior shoulder (the bounce off the wall dampens the speed), it does still train the posterior shoulder (concentrically). Pitchers use this drill to prepare the decelerators to handle higher velocities - those that occur during the acceleration & follow-through phases of a pitch (or tennis serve).
Exercise 4 - Reverse Catch & Throw
Similar to reverse throws but a catch is incorporated. This exercise works both the eccentric (when you catch the ball) and concentric portions of the posterior shoulder. More importantly, it forces the shoulder to improve its dynamic stability and to utilize the stretch shortening cycle efficiently - which will help to absorb and produce higher arm velocities. Increase the intensity by increasing the weight of the ball, the speed of the throw (by the coach) and the height of the throw (by the coach).
Important points to consider when training the tennis shoulder with plyo balls
Progress from lower intensity to higher intensity exercises.
Use lighter loads (plyo balls that weigh roughly 500g to start - or lower for juniors under the age of 14 - and progress to plyo balls that are no more than 2000g - anything above that could lead to too much stress on the shoulder).
Start with rep ranges of 10-12 and progress to 15-20.
Set ranges begin at 1-2 and progress to 3 or more.
These exercises can also act as warm-up exercises for the shoulder before practices & matches as part of a thorough upper-extremity pre-tennis protocol (critical for injury prevention).