Archive for the ‘Biomechanics’ category

Bridges – How to spare the back…

March 5, 2010

A couple of weeks ago, a reader asked me to drop some comments on bridges.  It was asked something along the lines of why do coaches insist that gymnasts straighten their legs and keep their feet together when bridging?

I don’t know.

As I noted in my last post, repeated bouts of lumbar flexion are believed to be a potential risk factor lumbar spine disorders such as a herniated disk.  Just the same, the lumbar spine really is not made to excessively arch or hyperextend as is seen when gymnasts perform skills such as bridges, backbends, and back walkovers.  Aside from these skills, when does a gymnast actually assume this type of a position?

Quite honestly, I cannot think of any other skills in which a gymnast assumes this position with so much lumbar hyperextension.  Some may argue that this type of bridge development is necessary for a successful performance of a back handspring.  Or, that’s an argument that I’ve heard a few times over the years.  Is it really?  Below, are three screenshots taken from Shawn Johnson’s first tumbling pass at 2008 National Championships.  Notice that she never gets into the position that we see above and if she did, she wouldn’t be very successful.

Beginning of the BHS After the RO

Flight Phase of BHS - Just Before Hand Contact

During Hand Contact of BHS

Does any gymnast ever assume the position (as shown in the bridge picture above) in a back handspring or any other skill except for bridges, back/front walkovers, etc. ?  The important factor in bridge development is shoulder flexion or often – hyper-flexion.  In other words, we want the arms to be able to be lifted up by the ears or even past without the chest/ribs poking out.

As I discussed in an earlier blog posting, there are other factors that we must consider when a gymnast has “tight shoulders.”  Maybe the issue is not flexibility at all.  Maybe the issue is too much rounding of the upper back that which places the scapula in a poor position.  Maybe it’s a matter of poor scapular stabilization or an imbalance of the scapula musculature.  The key muscles that would limit shoulder hyperflexion are the latissimus dorsi and the pec major/minor.  There are other stretches specific to these muscles that do not stress the low back.

With that said, here is a better way to perform a bridge.  I first came across this suggestion from David Adlard in an old USAIGC publication called STEPing UP.  To minimize the excessive hyperextension of the low back, elevate the feet to above shoulder height and put the emphasis of the stretch on the shoulders.

In the picture below, a trainer colleague, Becky (who used to cheer and tumble in high school) demonstrates.  Thanks Becky!  She’s a little tight in the shoulders, but now this position can better emphasize the muscles that need to be stretched without putting the low back at as much risk.  Afterwards, she even commented something to the effect of – “Wow, that really stretched my upper back…it felt good…”

Feet Elevated Bridge

Do we really need to be doing sit-ups & crunches?

March 4, 2010

Dr. Stu McGill from the University of Waterloo in Canada has strongly advocated that repeated lumbar spinal flexion (i.e. rounding of the low back) may ultimately lead to a disk injury.  The question that remains unanswered is how many will it take to lead to injury?  That’s probably a question that is HIGHLY variable depending upon the individual.

Nevertheless, I have pretty much stopped doing crunch/sit-up-type exercises.  I feel that you can achieve the same effect performing core stabilization exercises such as planks.  The closest that I come to a crunch is a reverse crunch, which I feel is a lead-up to performing a candlestick/lever raise on the floor, hanging on a bar, on the rings, etc.

With that said, here’s a study that was conducted on US Army recruits comparing a sit-up training program vs. a core stabilization program on performance of the US Army Physical Fitness Test.  What was found was that –

“….there was a small but significantly greater increase in sit-up pass rate in the CSEP (5.6%) versus the TEP group (3.9%).”

CSEP = core stabilization exercise program

TEP = traditional exercise program

Effects of Sit-Up Training Versus Core Stabilization Exercises On Sit-Up Performance

Medicine & Science In Sport & Exercise. 41(11):  2072-83, Nov 2009.

What are your thoughts?

What Is Ideal Posture?

February 10, 2010

A couple of weeks ago, Troy created a blog post about training the handstand.  Obviously, as coaches, our goal is to help the gymnasts develop a handstand that is straight as possible.  But, just what exactly is ideal posture???

Well, ideal posture is defined as a straight line passing through….

Photo taken from:

Oatis, C.A. Kinesiology:  The Mechanics & Pathomechanics of Human  Movement, 5th ed. Lippincott et al., 2004.

  • the ear lobe
  • the bodies of the cervical vertebrae
  • the tip of the shoulder
  • mid-way through the thorax
  • the bodies of the lumbar vertebrae
  • slightly posterior (behind) to the hip joint
  • slightly anterior (in front of) to knee joint axis
  • slightly anterior to the lateral malleolus (ankle bone)
One thing worth mentioning is this – if your athletes can’t stand up straight, how can you expect them to be straight when they are upside down on their hands?

I think that handstand development begins by correcting posture and alignment in a standing position as well as both prone (on the belly) and supine (on the back).

Proper Landing Mechanics

February 6, 2010

Received an e-mail the other day requesting more information about proper landing mechanics. Here’s an excerpt from the e-mail:

Could you talk a little about landing positions, if you haven’t already done so?  I remember reading a comment recently about coaches emphasizing legs together on landings, but it makes more kinesiological sense to have knees and feet shoulder width apart.  The Gymnastic Minute on YouTube addressed the correct landing posture today, but I’d like to have a more in-depth explanation.

Here’s the YouTube video that this individual is referring to:

In terms of the feet being together versus apart, a wider base of support allows for more stability.  Secondly, it is nearly impossible to get the hips shifted back enough to allow the glutes and hamstrings to assist in absorbing the energy from the landing if the feet are together.  Why is this important?

Well, here is an article from the NSCA Performance Training Journal (a free online publication on the NSCA’s website) that explains matters more in-depth.  However, I will give you a brief overview.

The hamstrings originate on the ischium of the pelvis and attach on the back of the tibia (shin bone).  Their main job is to bend the knee and their secondary job is to open or extend the hip.  Well, as the knee bends from a landing, the hamstrings will activate and pull the shin bone backwards.  This takes some of the stress off of the anterior cruciate ligament (ACL).  The ACL attaches at the back of the femur (upper leg bone) and the front of the tibia.  Its main job is to prevent the tibia from moving forward too much.  So, if the hamstrings activate and pull the shin backwards, this takes some of the load off of the ACL.

Now for the glute max.  The glute max’s main job is to open the hip (extension).  However, the glute max also helps in controlling rotation of the femur since it partly inserts on the greater trochanter of the femur.  (I say “partly” because part of it also forms with the TFL and creates a sheath that runs down the side of the leg known as the IT Band and this connects on the side of the tibia)  Further, it assists the gluteus medius (as Kris Robinson mentions in the YouTube clip) in preventing the knees from dropping in – known as “valgus” position.

Controlling rotation of the femur and preventing it from dropping inward is very important to knee health.  Coupled with an inwardly rotated tibia,  you’ve got the makings for disaster.  This is why what appears to be a perfect landing could end with the gymnast on the ground in agonizing pain.  Having been witness to a couple of these in my coaching career, I now have a better understanding behind the “why.”

While this is all well and good, the problem is that gymnastics promotes a quad-dominant landing despite the obvious biomechanical problems that it presents.  Despite the traditional gymnastics approach, I encourage all of you to think about the health of your gymnast and consider having them bend at their hips a bit more and push their butt backwards to allow for the glutes and hamstrings to engage more and assist in absorbing the landing.  Your gymnast’s knees will be thankful later.

Anyway, I hope this offers some insight into proper landing mechanics and their importance.

The Hurdle – Part I

January 26, 2010

I wish that I had some pictures to express what I am about to discuss, but I do not unfortunately.  To follow along, the best that I can do is have you reference a YouTube video of Cheng Fei’s Yurchenko 2 1/2 from 2005 World’s in Melbourne.  At :51 seconds in, there is a side view in slower motion.  If you stop the YouTube player, you can see much of what I describe below.  I tried to create screen shots, but the camera quality is not good enough and it’s too blurry.

The hurdle by definition is simply a transition from a run such that the athlete can maintain as much of the horizontal momentum as possible that was generated from the run into their tumbling skill(s) or vault.

When walking/running, the center of mass is constantly moving upwards and downwards. With that said, the goal is to keep the center of mass as constant as possible as any major displacement will affect the horizontal momentum that has been generated.

Despite this, I believe that there should be a bit of a vertical component to the hurdle. I like to see the hurdle go both upwards and forwards. Will you lose a little horizontal momentum? Yes. The same happens in vaulting. But, I believe it’s minimal. The reason that I feel that you must go slightly upwards is because of the back leg and where it contacts the ground.

David Kenwright, Olympic coach in Canada, and someone that I respect greatly, teaches his athletes to try and “scoot” or “shuffle” (I believe is his terminology) their initial contact leg (which is the “kicking” leg of a round-off/cartwheel) underneath of them as it initially contacts the ground. When watching the top tumblers, this definitely seems to be a trend as all of the best do it. Whether they were taught or they do it naturally, it happens.

Stacy Maloney, head coach/director at Swiss Turners in Wisconsin, is another person that I heard discussing the importance of the position of the back leg.  I have uploaded an excerpt from a lecture that he gave at the 2003 Region IV Congress (I believe…I dubbed this from another coach) where he discusses three important aspects of the RO.

Note:  I apologize for the poor sound quality.  I dubbed this video from someone else – from VHS to VHS and I used Dazzle software to convert it to digital format.  If you use headphones or turn up your speakers, you should be able to hear it.

In part II, I will look a little more at the mechanics of the hurdle and my mechanical rationale for the importance of the position of the back leg as such.

Sports Rehab to Sports Performance Teleseminar 2010!!!

January 26, 2010

For those of you who are really geeky like me, here is a link to a series of FREE teleseminars on a variety of topics related to sports performance, rehab, injuries, etc. etc.  And, the best news of all – It’s FREE!!!!

CLICK HERE for the website where you can sign up.

One interview per week, for eight weeks, starting Wednesday, January 27th. Each interview will last from 45 to 70 minutes (depending on the speaker). 8:00pm EST each Tuesday night through March 24th. If you can’t make the call, don’t worry! It will be made available for another 24 hours

Speakers include renowned physical therapists, chiropractors, strength coaches, & athletic trainers.

If you know anything about the physical therapy/rehab world, names like Craig Liebenson, D.C.; Shirley Sahrmann, Ph.D, PT; Stu McGill, Ph.D; Michael Reinold, PT, DPT; etc. are some of the most respected names both nationally and internationally and folks that will be participating in this teleseminar.

If you have any questions about who any of these folks are and what they have done, please leave your question in the comments section and I’ll respond accordingly.  With that said, if you type their names into the PubMed research database, you should find quite a few peer-reviewed journal articles by each listed.

The interviews will be made available for up to 24 hours afterwards.

Super Tight Shoulders…We Must Look At Other Factors…

January 1, 2010

This is in response to recent comments by “Just Another Opinion.” I figured that I might as well make a blog post about it.

Yes, there are other factors outside of merely shoulder flexibility that dictate shoulder range-of-motion. Of particular importance is the position of the scapula as the scapula contributes to upwards of 60 degrees of arm elevation. Thus, when you lift your arm over your head, your scapula must move 1 degree for every 2 degrees that your arm lifts overhead – regardless of whether you are lifting it straight up (shoulder flexion) or bringing up to overhead from the side (shoulder abduction). This is referred to as “scapulohumeral rhythm.” The other 120 degrees of shoulder motion is contributed from the shoulder (glenohumeral) joint itself.

The scapula is controlled actively as it is supported by 17 muscles. Imagine a string that is pulling on an object in 17 directions. It is critical that those forces be functionally balanced so that it can be moved appropriately as the different forces act upon it. When you move your arm in an upward direction, the scapula should upwardly rotate, abduct, and slightly posteriorly tilt on the thorax. If you have certain scapular stabilizers (I won’t get into specifics just, yet…I will in future posts) that are not doing their job appropriately, you’ll get abnormal movement and this can dramatically effect how high one can lift their arm.

Secondly, the degree of “rounding” (thoracic kyphosis) in the upper spine can also have a dramatic effect. Increased kyphosis puts the scapula in the wrong positions and this, in turn, can affect upper arm elevation. Doing regular thoracic mobility, such as foam roller extensions, should be commonplace since gymnasts perform so many pushing activities (casting, pressing, etc.) as well as “hollowing.”

These types of movements really develop the front side of the upper body, but most conditioning programs fail to appropriately balance the upper back and scapular stabilizers. As a result, the kyphosis continues to increase.

Here is an example of thoracic extensions with a foam roller shown by Eric Cressey of Cressey Performance in Hudson, MA.

Lastly, I will talk a little bit more about normal postural development in a future post. Sometimes, in younger children, the resulting kyphosis is a result of a compensation for excessive anterior pelvic tilt – which is actually very normal throughout postural development. In other words, as the child grows, some of those deformities will go away.

So, there is a lot more content on this subject forthcoming in the near future!