High Rep Box Jumps and Achilles Injuries

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I was on my 297th rep with about 50 seconds left in open WOD 13.2 and on 298 I found myself on the floor with only one working foot.  Box jumps were always a go to movement for me and now I am looking at a 9-12 month recovery before I will be back to 100%.  That is a hard pill to swallow for a former collegiate basketball player and fairly competitive CrossFitter.  This was the first year I wouldn’t qualify for Regionals.  The infamous Achilles rupture……

In case you have been living under a rock for the past three years there is a fairly animated debate about the use of high rep box jumps within the CrossFit Community.  Acute ruptures of the achilles tendon usually occur in middle-aged men during athletic activities. Most ruptures occur when pushing off with the weightbearing foot while extending the knee; however, injury can also occur during sudden or violent dorsiflexion of a plantar flexed foot (eccentric contracture, the receiving position of a bounding box jump).   A large percentage of achilles tendon injuries are preceded by some degree of tendinosis or paratenonitis in combination with overuse.  Tendinosis is a noninflammatory condition that involves intratendinous degeneration and atrophy due to repetitive microtrauma, aging, or a combination of these.  Isolated paratenonitis is characterized by inflammation that is limited to the paratenon. It is especially common in middle- and long-distance runners, who report localized pain after strenuous activity. (Daniel S. Heckman, 2009)  These particular cases are not the ones that this article will address because they are generally accompanied by symptoms that can be identified and alleviated, ultimately preventing catastrophic injury.  There are a lot of people with their own opinions and more than a couple horror stories.  I’m not writing this to give you my opinion; there are far too many of those floating throughout the vast interweb.  The purpose of this article is to provide you as a trainer, box owner and athlete information that can assist you in determining what is safe for you and your athletes and what the major associated factors are that COULD contribute to an achilles tendon injury.  Notice I didn’t say WILL contribute.  There are arguments that bounding (or rebounding) box jumps performed in high volume will induce Achilles ruptures.  For the community to dub “box jumps” as the culprit and absolute cause of Achilles injuries would be premature or even short sighted.  It appears that where this argument has gone astray is cause versus association.  You should know the difference and be educated on the factors involved just like we do with nutrition.   Association does not justify cause.  Gary Taubes, the author of “Good Calories, Bad Calories”, has spent the better part of two decades arguing the differences between cause and association to those in the field of nutrition.   It would be wise for us to do the same here.  We could start by simply asking the question, “What causes achilles ruptures?”  It’s doubtful that we would definitively come to the conclusion that bounding box jumps is the answer without considering any other options.   I don’t care what you do, only that you are informed.   I don’t want anybody to have to fight through this kind of rehabilitation.  Not even people who use the squat rack for bicep curls.  Knowing is half the battle…..

Rupturing your Achilles is like buying a Jeep.  Suddenly everywhere you look there is someone that has been there.  Blogs, support groups, chat rooms… the works.   All for the newest members of the drop foot club.  I’ve gotten stories of everything from just stepping out of bed to box jumps to beach volleyball.  Each of them just shakes their head with a look of pity for the new member of the club.  As I write this, 5 months post-op, I can tell you that I’m not afraid of high rep box jumps, nor am I on the anti-box jump hate train.  I’m in the middle and look at it for what it is: an injury that could or couldn’t happen.  There are a lot of logical, fact based arguments for both camps, which is why it’s important for you to know where you and your athletes stand statistically.  When it boils down to it, it’s just a numbers game.  You either win the Achilles lottery or you don’t.  But, there are some things you can do to improve or diminish your odds.

If you Google “Achilles tendon rupture” you will get something to this effect: symptoms- soreness, poor flexibility, tight muscles, swelling, stiffness, and wait for it….. Hearing a snapping or popping noise during the injury (yes that was actually what I heard).  Causes will be listed as every sport ever invented, including curling.   So a word of caution to you ice shaving warriors out there. Sounds pretty general and uninformative right?  Almost to the point that we should never get out of bed because we are all somehow doomed to blow up the back of our ankles.  In order to collect some measurable, observable and reproducible data I’ve narrowed it down to five major contributing factors, some of which are well known, others not so much:


  • Gender/Age:  Most common in men in their 40′s and 50′s with a 5:1 ratio of injuries male: female
    • Mobility:   Biomechanics affect your likelihood of injury with any movement.  (Overpronation of the feet, valgus knees etc.)
    • General competency as an athlete with a movement (experienced/high or low level athlete)
    • Training program: frequency of jumping, running combined with the amount of time you spend in Oly shoes (shortening your heel chord)
    • Antibiotic use: specifically  Flouroquinolones


There are certainly other factors that we could analyze.  Nutrition is one that could be discussed at nauseating length, but CrossFit has done a solid job of challenging traditional thought and getting people more educated on quality nutrition and hydration. For this reason, I have chosen to omit it from this discussion.  That being said, the above five factors are the most understood and allow for quantification or modification of the likelihood of injury occurrence.  Let’s jump in!

Age and gender aren’t anything we can prevent or change.   Be aware of what categories you fall into and understand your likelihood for injury.  Just know that there are always statistical outliers so this doesn’t mean that it won’t happen to you because you are a 20 year old female.

Mobility is something that has come to the forefront of CrossFit thanks to the genius of Dr. Kelly Starrett and the creation of the MWOD.  I have to admit that I’m a Supple Leopard groupie and have witnessed the good that comes from taking care of your body and understanding movement patterns.   If you have poor flexibility in the ankles (can’t do a pistol), or you have valgus (caved in) knees while performing explosive movements with the tendons and muscles off axis you stand to be at higher risk of injury due to your mechanics.  Conversely, I’ve seen plenty of poorly performed box jumps go without injury.  Work on your mechanics every day and improve your motor patterns!   Up stream, downstream, mash parties; you know the drill.  It takes time but you can completely re-program yourself and this will reduce your chances of injury.

General competency with a movement is whether or not the athlete can safely and consistently perform a bounding box jump.  There are a large number of athletes that actually cannot.  Novice CrossFitters generally don’t possess the accuracy, coordination, precision or agility to perform that movement at a high level.  Some athletes are not technically sound when loading the hips, knees and ankles for jumping.  This can lead to improper load order sequencing and place larger than necessary force on the smaller joints.  Trying to operate outside of one’s own capacity can lead to degraded performance. The bounding box jump has obvious benefits of increased power output, but it is not the end all be all of jumping. Inexperienced athletes end up stepping down during high volume box jumps because it’s energy efficient, not necessarily because they want to.

The previous three factors are probably common knowledge in your box.  I’m going to spend a little more time on the last two factors because they seem to be the least addressed or recognized within the community and are arguably the most relevant issues with respect to CrossFitters.

Training programs will come into play specifically in the higher level athletes.  Is 150 box jumps every week a good idea? Should you never program 150 box jumps?  How much time have you spent running over the course of the previous 5-6 months?  Same question goes for jumping (on a box, or double unders)?  What does the overall volume for that athlete look like?  Are you doing a program that biases Olympic lifting?  With the growth of CrossFit has come the growth of weightlifting.  This has proven to be a good relationship for both sports.  With more weightlifters comes a higher frequency of athletes wearing Oly shoes. One condition that alters the functional demands placed on lower limb muscle-tendon units is the use of high heeled (HH) shoes. (Neil J. Cronin, 2012) Spending a significant amount of time in Oly shoes results in a shorted position of the achilles tendon. If this sounds like your regimen then you should understand what could happen. There are numerous articles in medical journals on the significance of HH use among women and the risks associated with prolonged wear of a raised heel (studies starting with a heel height of 5cm, the avg effective heel on an Oly shoe ranges from 1.905 to 3.175cm).  Orthopedic literature has demonstrated that long-term HH use has been found to shorten medial gastrocnemius muscle fascicles and increase achilles tendon stiffness. (Neil J. Cronin, 2012)   Take that into account if you see high volume jumping and you have been in your Oly shoes every day for the past 4 months.  Human movement requires an ongoing, finely tuned interaction between muscular and tendinous tissues, so changes in the properties of either tissue could have important functional consequences.  Other studies have found that the use of HH shoes does not immobilize the muscle tendon units but rather coerces them to operate at reduced length.  Length adaptations may be provoked by habitual activity and the functional demands imposed. (R. Csapo, 2010)  This would be something to consider when going from prolonged bouts in shortened tendon positions into high volumes of jumping that will repeatedly reach extreme range of motion (EROM).  Not an ideal scenario right? This is by no means an assault on Oly shoes.  If you don’t have a pair, you should get some.  We tell our athletes if they are serious about lifting weights the first thing they need to do is invest in a pair of shoes.  Olympic lifting shoes will help you to move maximum weights optimally.  Use outside of heavy lifting is a crutch for poor mechanics or worse mobility.  You don’t need your Oly shoes for metcons. Don’t be naïve to the possibility that there could be long-term risks involved if you ignore your heel chords and don’t frequently combat the effects of elevated heel shoes.  Your chances of injury are slim, but there is an increased potential for injury with prolonged use.

Flouroquinolone antibiotic use is arguably the least addressed issue when it comes to this topic.   The links between this antibiotic class and tendon injuries is concerning because these are frequently prescribed drugs and people are completely unaware that they are at an increased risk for injury when used.   Calculated risk is different than ignorant risk. Flouroquinolones were introduced in the early 1980’s for bacterial respiratory conditions.   It is well documented that flouroquinolones such as Ciprofloxacin, Levofloxacin, Norfoxacin, Perfloxacin, and Ofloxacin are associated with increased risk of tendon injuries, mostly the achilles (88%). This injury pattern occurs at such a high rate that they now require a “Black Box Warning” from the Food and Drug Administration.  Between 1991 and 1999 the incidence of flouroquinolone users was 722/100,000 person-years.  (Jacob Sode, 2007)  In the medical field it’s common knowledge.  Ask any doctor, nurse, corpsman, medic or pharmacist and they will confirm your inquiry.  The actual cause for the association is unknown, but is believed to be due to the direct toxicity and degeneration changes on collagen fibers. (Zhanel, 2003)  It is estimated that spontaneous ruptures occur in about 1 in 100,000 people. The FDA says “taking the drugs appears to TRIPLE OR QUADRULPLE the risk”.   One specific study conducted between 1991- 2002 revealed a mean increase in injuries of 22.1% but as high as 60%.  The total number of ruptures evaluated during that time period was 1,538, 75% of which were males. Although actual daily dosages are unknown, patients who took the prescribed drug were three times more likely to sustain an injury within 90 days of the first dosage.  Times of injury after taking the drug range anywhere from two hours to six months.  (Jacob Sode, 2007)  Flouroquinolones are a first line standard in health care.  You should leave the determination of use up to the healthcare professionals, but at the very least have the conversation with your provider.  Try to come up with a protocol for scaling your programming and determine how long that time line should be after using these antibiotics.  An open honest relationship with your physician is never a bad idea.  I was ignorant to all of this until I was injured.   Naturally I began sifting through the almighty internet.  Research this with caution and a fine tooth comb.  YouTube documentaries such as “Certain Adverse Affects” can be a bit disturbing. This documentary is the “Food Inc.” or “Forks Over Knives” equivalent of the narcotic production and approval process.   Just remember that not everything on the internet is true or completely accurate.


None of these factors means you are certain to rupture your achilles tendon.  The counter argument to all this is the achilles tendon strength and the more than 20 million box jumps preformed during the last 3 years of the open.   The fast transition from eccentric to concentric movement in the bounding box jump will increase the load on the tendon and can increase chances of injury, but the achilles tendon is the strongest tendon in the body and a healthy tendon can handle huge loads.   Achilles tendons are believed to have a breaking stress of about 100 MPa. However, whereas most tendons experience peak stresses below 30 MPa, the human achilles tendon may experience peak stresses in excess of 70 MPa during maximal eccentric plantar flexions. (M. Kongsgaard, 2005)  How much is that?  70 MPa=1,461,980.396 lbs/sq ft!!    Let’s say that arbitrarily 100 people ruptured tendons during the last three years of the open (I only know of or have heard of less than 2 dozen).  That is a 0.000005% chance of injury.  Presented another way, a 99.999995% chance of not injuring yourself.  Obviously, this is only taking into account three WODs over the course of 36 months.  If we could take into account an entire year’s worth of WODs the injury rate would likely be higher, as would the number of box jumps performed.  We can safely assume that the figures would vary only slightly.  Your average odds of winning the Mega Millions Lottery are not much better (0.00000000569114597006% or 1 in about 175M).  The math here is by no means definitive (mostly because it’s my math) but you get the drift.  Those numbers don’t support the claim that box jumps cause ruptures.  If box jumps were the actual cause, then injury rates would be much higher (likely into the thousands).

It is quite possible that proper attention to reducing this injury pattern won’t be addressed until it happens to a high profile athlete. After all, most people don’t concern themselves with issues that don’t directly affect them.  It could happen to any high profile CrossFit athlete, pick one. In CrossFit it most recently happened to Cheryl Brost during Regionals. It also recently happened to Kobe Bryant who is arguably one of the biggest names in all of sports.  There has been no debate about stopping the way basketball players run, cut, or jump.   Annie Thorisdottir dropped out of the open this year due to an injury sustained while deadlifting.  Is there a growing movement to stop people from moving large loads quickly?  Examples like this are endless and can be debated to no end.  CrossFit has a growing slice of the community that is now a competitive sport, not just a strength and conditioning program.  With sports come injuries.   Some injuries are clear cut, others are not.  It’s likely that there are underlying issues involved in any injury, and in most cases the simple act of playing sport isn’t the cause of an injury.  There has been no precedent set that would suggest that the possibility of injury will deter athletes from playing sports.  Knowing only that fact, one could argue that it’s our responsibility to indentify causes of injury if possible.  If a cause cannot be undeniably identified then we must be as educated as possible on the risks and all the factors that increase that risk.

Use the five factors detailed above and assess your athletes (and yourself) to see how many of those factors apply.  Probably at least one, if not multiple.  It is pretty indisputable that in the sport of CrossFit, box jumps are the mechanism that results in achilles tendon injuries, but that does not mean that they are the cause.   You could have all five of these factors apply to you and never sustain an achilles injury.  You could have one, two or none and sustain the injury tomorrow. My scenario is as follows:

1)     32 yr old male (strike one)

2)     Good ROM and religious mobilizer with no symptoms or pains prior to injury

3)     Box jumps are in my wheel house

4)     Starting in Oct of 2012 I ditched running and was on the platform 5 days a week working on my lifts (strike two)

5)     I had taken Cipro for three days about 6 weeks prior to the injury (damn..)

As box owners and stewards of CrossFit, it’s our responsibility to be as informed as possible so that we can make the best decisions for the prolonged health of our members and the community.    I can tell you that in our gym we now have members step down off the box.  That doesn’t mean we won’t ever let them bound.   I’ll let them do it occasionally because there are benefits to be gained there.  If I have an athlete that has a shot at making it to the big stage I would start incrementally adding small doses of bounding box jumps into the programming.  This would facilitate a reasonable time frame for any adaptation needed for an athlete and is a good idea for any increased volume in training.  It’s risk versus reward and you have to make that calculation yourself.   Ultimately there will still be people for and against bounding box jumps and all I will tell you is make an informed decision on what is best for your athletes.  The risk is obviously there, so understand the factors involved and do everything you can to mitigate it.  I can assure you the road to recovery is one of the longest in all of sports.    Mobilize, talk to your physician about the use of flouroquinolones, and don’t spend so much time in your Oly shoes!

Collaborated by Fern and Dr. Rich Redlinger