Beyond Stretching: Defining Mobility and It's Implications for Tennis Players

This week I’ll be traveling to London UK to take part in the Functional Range Conditioning (FRC) course (aka an excruciating experience on your hips...or so I've been told). The FRC course - created by Dr. Andreo Spina, owner and founder of Functional Anatomy Seminars - is a system of mobility training rooted in scientific research. I’ve always integrated mobility & flexibility work with my athletes and have a pretty good understanding regarding its underlying mechanisms but why not learn from someone who has devoted their life’s work to improving mobility, joint function and athletic performance. And...he’s worked with a number of pro athletes, including world no. 4 Milos Raonic (see video below):

There's no question tennis has evolved - and is continuing to evolve. You see players sliding on hard courts and contorting their bodies like never before. Just watch a Novak Djokovic or Serena (image below) match, they're essentially doing the splits on a regular basis.

There might be some transfer of traditional stretching to active range of motion (ROM) - i.e. controlling ROM in a particular joint. But...to gain the ability to do the splits, like Serena or Novak, while at the same time smacking a groundstroke back at 100mph - takes more than just a few stretches done daily. In other words, it’s not necessarily just about increasing muscle length, but rather total range of motion about a joint. 

That’s the performance side of mobility, but there seems to be a strong correlation between active ROM of a particular joint and injury risk as well - the more the range deviates from normal, the higher the chances of injury. This is especially true for the tennis shoulder - which we talked about in a previous post regarding its ballistic strength qualities. Older research has suggested that passive internal shoulder range of motion (i.e. when the shoulder is placed into internal rotation by an external force) - aka glenohumeral internal rotation deficit or GIRD - is associated with injury risk in tennis players. Although that may still have some merit, more recent evidence suggests that its full, active range of motion of the shoulder (internal + external ROM combined), that’s a better indicator of injury risk.

In this article we’ll briefly define mobility, explore tennis players’ joint ROM and look at some of the most common tennis injuries - spoiler, you may be surprised by the most prevalent injured area in tennis.

Mobility Defined

Here’s a definition of mobility by Dr. Andreo Spina himself:

“Mobility, defined as the extent of controllable flexibility across articulations (flexibility plus strength), refers to the amount of USABLE motion that one possesses.

In any particular articulation there exists both a passive, as well as an active range of motion. The passive range refers to the angles that are only attainable through passive means (ie. the application of passive, external force). The term ‘flexibility’ has historically been synonymous with this concept and has been the focus of many athletes, trainers, therapists, sports medicine practitioners, and society as a whole. Reasons for this goal have historically included injury prevention, improving athletic performance, retarding the effects of aging, and developing long ‘athletic-looking’ bodies. However, as with most physical exercise activities, stretching and flexibility training has long fallen into the realm of ‘gym science,’ while the true science has failed to be recognized. This has lead to the creation of flexibility training programs, which have been largely ineffective, misguided, dangerous…and that have failed to realize any of the desired goals.

Active ranges of motion are those ranges that are attainable through the application of active internal (muscular) force simulated by nervous system activity. It is these active ranges that can bestow the aforementioned benefits of injury prevention, improved performance (athletic and non-athletic), and lasting articular health.”

What Spina is basically saying is that having “passive range of motion” - usually trained through flexibility/stretching exercises - is essentially not USABLE, especially in the context of sport performance. Although I still believe that passive and static stretching can be useful and should be a part of the tennis player’s program (for other reasons), it may not transfer directly to sport.

When referring to mobility, what we’re effectively saying is that there exists a flexibility AND strength component. In other words, can you actively move a joint through its entire range of motion (this has neuromuscular requirements). More and more experienced strength & conditioning coaches have been using dynamic stretches, a form of mobility work, to improve their athletes’ active range of motion with the hope that it prepares them for the upcoming training/competitive session, decreases injury risk and improves performance.

Common Tennis Injuries

Before we look at ROM in the elite tennis player, let’s talk injuries. Although there may be many reasons a player gets injured - including improper training volumes, strength imbalances/deficits, poor mechanics etc. - I strongly believe lack of ROM is a contributing factor. Not only is lack of ROM potentially inhibiting, but the fact that many players aren’t encouraged to restore ROM after training and matches can worsen the case.

We know tennis is a repetitive sport with specific patterns of movement. These movements require repeated muscular contractions. Targeted tissues - which include muscles, tendons, ligaments, joint capsules, fascia etc. - may become shortened, tight and/or restricted. This could lead to unfavourable adaptations to muscles & joints while impeding function, decreasing performance and increasing injury risk.

So let’s take a quick peek at some of the most common injuries in tennis.

Lower Extremity Injuries in Tennis

It seems that lower-body injuries in tennis are most common and comprise 39-65% of all tennis injuries, according to Ellenbecker. Out of all lower-body injuries, ankle sprains occur most often (highlighted by inversion sprains - i.e. rolling your ankle inwards). This is followed by the thigh region and could include anything from a hamstring, quad or adductor (groin) pull - and most restrictions in the groin area are due to immobile hips! Finally, lower leg, including calf/achilles, knee and foot/toes have the lowest occurrence out of all lower-body injuries in tennis.

Upper Extremity & Trunk Injuries in Tennis

Next we have upper body injuries that tally up between 24-46% of all tennis injuries. The most common sites include the shoulder and elbow but we can’t forget about the wrist (Nadal, Del Po and others have all had rough wrist injuries in the past). The lowest injury rates occur in the low back and abdomen areas with an 8-22% occurrence.

What’s interesting is that most competitive players will experience 1 injury (whether it’s minor or severe) at least once a year.

The Case for Mobility in Tennis

A Closer Look at the Range of Motions of the Tennis Shoulder and the Tennis Hip

The Tennis Shoulder

We already know that the decelerators (external rotator muscles) for many tennis players are weak (read the full article here). But what about range of motion at the shoulder? We already mentioned that GIRD is linked to an increased risk of injury in the overhead athlete (when comparing dominant and non-dominant shoulders). But more recently, researchers are suggesting that total glenohumeral (GH) internal/external ROM of the dominant vs non-dominant shoulder AND total GH internal/external ROM of the dominant arm compared to normative data, are perhaps better predictors of shoulder injury risk. This is based on passive ROM.

When it comes to active ROM, it seems that total active internal/external ROM of the GH joint is likely the MOST important metric to look at. Ellenbecker suggests that anything more than 10 degrees loss from dominant to non-dominant could be a risk factor. Absolute changes in ROM must also be tracked over time. Although to my knowledge, this hasn’t been reported in the literature, anecdotally I’ve seen many top therapists (especially in baseball populations) that measure GH rotation ROM before and after competition. This is critical as acute changes could lead to chronic adaptations...and injuries.

The Tennis Hip

In both male (81 players) and female (28 players) elite players (with nearly half playing on the ATP & WTA), researchers reported statistically significant differences between dominant and non-dominant hip flexion and hip abduction ROM. Male participants also had differences in hip internal rotation when comparing left and right sides. These differences were not huge however (less than 6 degrees on average). It seems that modern tennis affects both hips - as players are hitting backhands similar to forehands in terms of stances, forces imparted on the hips etc.

What’s more telling is that passive ROM was restricted in flexion, extension and abduction for both groups and interestingly, internal & external active hip rotation was normal. Likely because these pros are at a high level and have resources (therapists, strength & conditioning coaches etc) to help improve these critical areas. It’d be interesting to measure these joint angles in younger populations and those that have reported pain in the hip/groin regions.

Unfortunately, to date, there isn’t any research looking at joint ranges for the ankle, wrist or trunk. But I’ll bet that if we did look at these areas, players would be lacking full active ROM.

What's Next

It’s my hope that this article has shed some light on mobility and its relationship to both tennis performance and injury prevention. More articles on this topic will follow, including specific exercises to help improve mobility - remember, that means both strength AND flexibility - in the elite tennis player.

To be continued...

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