Kinesiology and the 2016 Olympics Part II: Impulse when landing

During the first post on the Olympics I discussed how many different injuries can occur when an athlete lands from a jump.  Not only is the amount of force they have to absorb when landing a key factor, but the time over which that force is applied is also a very important factor.  Impulse is the product of the average amount of force and the time over which that force is applied.  In the graph below (Flannagan, S., 2014), the impulse for both the "stiff" landing and the "soft" landing are the same, but the amount of force that has to be absorbed by the jumper with a "stiff" landing is twice that of the force in the "soft" landing.  So, what is a "stiff" landing and what is a "soft" landing?  In a "stiff" landing, the joints of the lower extremity, primarily the hips, knees, and ankles, stay in a more extended position and do not give, or flex, as the person lands.  This means that the ground reaction force is applied over a very short time period.  In a "soft" landing, the person flexes their hips, knees, and ankles (technically dorsiflexion of the ankles) as they land to increase the amount of time over which the ground reaction force is applied.  This leads to a lower amount of stress placed on the lower extremity. That's why it is important to teach young athletes to perform a soft landing by flexing the joints of the lower extremity when they land (second figure below).

Flannagan, S.P. (2014) Biomechanics: A case based approach (1st ed.), Jones & Bartlett.

Kinesiology and the 2016 Olympics: Part I Tibia/Fibula Fracture

Yesterday, French gymnast Samir Ait Said suffered a horrible fracture (warning, graphic picture at the bottom of this post) of his tibia/fibula during the vaulting event.  Gymnastics as a sport carries a high degree of risk, and to me, vaulting might be the most dangerous event.  The gymnast runs as fast as possible, uses the vault to launch themselves as high as possible into the air, and then performs a series of flips and twists before landing.  Here is the video of the injury if you want to watch it. Gymnasts, and athletes in other sports, such as basketball and volleyball, land repeatedly during practice and games/competitions, and these types of fractures are very rare.  So, what went wrong to cause this injury and others similar to it (think about Kevin Ware in the NCAA basketball tournament a few years ago).

First, because Said projected himself so high in the air, when he landed he applied a large amount of force to the ground, and due to Newton's 3rd law of motion (for every action there is an equal and opposite reaction), the ground applied a large amount of force back to his foot.  Also, because gymnasts are taught to "stick the landing" in order to maximize their score, a large amount of force is applied in a very short time period (the product of the average amount of force and the time over which it is applied is called impulse, which applies to almost every Olympic sport/event).  Now, the mat helps dissipate some of this force, but it was still likely hundreds of pounds of force, probably 4-5 times greater than his own body weight.  However, he has probably landed from this same height with around the same amount of force hundreds of times during his gymnastics career, and never suffered an injury like this.  So, what really went wrong this time?

If you watch the video, you will notice that he did not complete his last rotation, and therefore was not able to get his feet directly underneath his body, or his base off support was not directly under his center of mass.  Ideally, when landing from a jump, it's best if the feet are directly underneath the person' center of mass.  Going back to Newton's third law, this will ensure that the ground reaction force is applied in the vertical direction and will be transferred directly up the person's lower extremity.  When Said landed, his feet were not directly under his body, so instead of the force from the ground being applied mainly in the vertical direction, it is applied at about a 45 degree angle from the ground.  The created a bending moment around the midpoint of his tibia and fibula, and because of the large amount of force, both the tibia and fibula broke.  I'll do another post discussing the relationship between the amount of loading placed on a bone and how much it can deform before breaking.  While this was a devastating injury for Said, hopefully with surgery and many months of rehabilitation he can make a full recovery.  It also demonstrates that in many sports, the most dangerous part is landing from a jump.  While fractures like this are pretty rare, other injuries such as ankle sprains, achilles strains/tears, and ACL tears often times occur when landing from a jump.

Kinesiology and the Olympics and Brett Favre

 Four years ago during the 2012 London Olympics, I did a series of blog posts about "Biomechanics and the Olympics" which highlighted some events and the biomechanical aspects of those events.  I've been encouraged to do that again (by my wife), so this year I'm going to call it "Kinesiology and the Olympics" and broaden the scope some to examine some other aspects of Kinesiology and how it relates to the Olympics.  I'm going to try and analyze some non-traditional events like race walking and hope to do 3-4 posts a week.  I might even have a guest blogger or two.

On another sports related note, Brett Favre is being inducted into the Pro football Hall of Fame this weekend.  Favre was my favorite football player growing up.  I got to watch him play at Southern Miss when I was a kid, watching several great performances including the upset over Alabama in 1990.  I followed his professional career through Green Bay, New York, and Minnesota, and eventually got to see him play in the NFL for the Jets against the Titans.  Last year my uncle, Steve Knight, was inducted into the Mississippi Sports Hall of Fame (he has the most wins of any college basketball coach in Mississippi history) and Favre was also inducted the same night.  It was a real pleasure to watch him play although I do feel older now that he is in the Hall of Fame.  Thank you for the memories, Brett.

What happened and what's going on

I lot of things have happened since my last post back in August.  We had a successful fall semester and are now well into the spring semester.  We started our doctoral program in Kinesiology in August and currently have 5 PhD students, including two in biomechanics, Brandon Miller and Jeff Simpson. We also have a really good group of Master's students.  With the help of these students and the guidance of Dr. Chander and myself, we have gotten the Neuromechanics Laboratory up and running. We have a number of projects that we have recently completed or that are being completed examining a wide variety things such as military boots and fatigue, balance and cognition, and hypergravity training.  We are leaving this week for the Southeast American College of Sports Medicine Conference in Greenville, S.C., with 2 doctoral students, 3 Master's students, and one undergraduate student where we will make 7 research presentations, and hopefully recruit some more graduate students.  I'll post an update with some pictures from the conference in the near future.

On a more personal note, Natalie turned one in January, and she definitely keeps us on our toes.  It has been really fun to watch her achieve her motor milestones and observe the differences between her developmental progression compared to Cameron.  Speaking of Cameron, he will turn 5 in March and start Kindergarten in August.  He is a really good big brother that just loves to take care of his sister!

Update on Things

Well, it's been quite awhile since my last blog post.  Natalie, our daughter who was born January 5th (6 weeks early), will be 7 months old on Wednesday.  She's still on the small side, but she is doing really well.  She has gone from 2 lbs, 15 oz and 15.5 inches at birth to 11 lbs, 10 oz and 23.5 inches at 6.5 months.  She is a very happy baby (except for car rides) and so far she has met all her motor milestones, which are sometimes delayed in premature babies.  Our son Cameron turned 4 years old in March and will be beginning a pre-K program next week.  We just finished our first season of kickball, which was a lot of fun, and somehow I ended up coaching his team.  Time really does go by quickly.  As far as things go at Mississippi State, we are starting our kinesiology doctoral program this Fall, and we obtained some space in our building and started a neuromechanics lab this past spring (with Dr. Chander).  This new lab space and the presence of doctoral students will allow us to conduct some exciting research in the future.  I was also promoted to associate professor and granted tenure, which would not have been possible without the help and support of so many people, especially my wife Amy.  The future looks bright here.

On another note, I wanted to take a little bit of time to brag about my uncle, Steve Knight.  He has been the head basketball coach at William Carey University for the past 33 years.  I used to be a ball boy for him back when I was younger.  This weekend, he was inducted in the Mississippi Sports Hall of Fame, which is such an incredible honor.  He has won 610 games during his tenure (making him the all time leader in wins among Mississippi college basketball coaches)  and several league and tournament championships.  It was a really special night for him and our family, and it was also cool to see him sitting up on the stage next to Brett Favre, who was my favorite football player growing up.  We are really proud of Steve and the legacy that he has set.  I was never a great basketball player, but he helped me a lot growing up with my game and gave me the chance to be around a college basketball team, and for that I am grateful.

The newest little Knight!

Well, it's the first week of February and this is my first blog post of 2015.  But, there is a good reason for that.

The pictures above are of our daughter, Natalie Elizabeth Knight.  Her due date was on Valentine's Day, but due to some complications, she was born on January 5th via an emergency C section.  She was (and still is) very small.  She only weighed 2 lbs., 15 oz. when she was born, and was 15.5 inches long.  One of the reasons for the emergency C section was because she was not growing much at all in the womb.  Even though she was 6 weeks early and very small, she has not had any complications. She was born here in Starkville at Oktibbeha County Hospital, and she did not have to be transferred to a NICU.  The nursery staff at OCH is just phenomenal and took such wonderful care of us.

When Natalie was born, they told us that she would have to weigh 4 pounds before we could take her home, which could take a month or more.  She has steadily been gaining weight since her birth, and on Tuesday, we got to take her home even though she was just shy of 4 pounds because she has been doing so well.  We went back yesterday for a weight check and she now weighs 4 lbs., 2.4 oz.  She is truly a miracle baby and we are so excited to have her at home so we do not have to keep making trips up to the hospital.  I will post updates every now and then about her progress, and I hope to be able to do some more kinesiology/biomechanics posts here in the near future as things settle down.

Happy Fall!

I realized that we are almost 3/4 of the way through the semester and I haven't blogged since the beginning of the semester.  It's been a very busy semester and I just haven't kept up with it like I should have.  I wanted to post a picture of Cameron in his Captain America costume from Halloween last week.   It's hard to believe that he will be 4 years old in March.  I have to go talk to his preschool class tomorrow about being a kinesiology professor, and while Cameron just loves the skeletal system, his preschool class might be a bigger challenge than teaching 18-22 year olds.  I have a graduate student that conducted her thesis research with a therapeutic horseback riding program held out in French Camp, MS (a very small but nice place with great facilities). She is looking at the influence of horseback riding on motor function among children with Autism.  Cameron just loves horses, so I decided to take him out there one day.  He had a great time and even got to ride a horse for the first time after the regular sessions were completed.  He got to go back out to French Camp again last week and ride a different horse.  I am looking forward to seeing the results of this study once Jennifer analyzes her data.  I'll post another blog soon analyzing some of the injuries that have occurred this football season.