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Sports Biomechanics

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Sports Biomedicine and Nutrition                                                                                                    ST07001388

Name: Jamie Williams

Student Number: ST07001388

Course: Sport Biomedicine and Nutrition

Module: Biomechanics

Word Count: 2228

Sports Biomechanics and Functional anatomy

In this assignment I will provide an overview of relevant anatomical structure of my chosen lower limb joint, which will be the knee. I will then go on to discuss the role of technology in general (i.e. how human movement and joint function can be measured) and describe how it can be used to analyse performance in various different sports.

The knee

The knee is essentially made up of four bones. The femur, which is the large bone in your thigh, attaches by ligaments and a capsule to your tibia. Below and next to the tibia is the fibula, which runs parallel to the tibia. The patella, or what we call the knee cap, rides on the knee joint as the knee bends. ‘When the knee moves it does not just bend or straighten, there is also a slight rotational component in this motion. The knee muscles which go across the knee joint are the quadriceps and the hamstrings. The quadriceps muscles are on the front of the knee, and the hamstrings are on the back of the knee. The ligaments are equally important in the knee joint because they hold the joint together’. (Elaine N. Marieb, Katja Hoehn 2007) The knee joint also has a structure made of cartilage, which is called the meniscus or meniscal cartilage. The meniscus is a C-shaped piece of tissue which fits into the joint between the tibia and the femur. It helps to protect the joint and allows the bones to slide freely on each other. There is also a bursa around the knee joint. A bursa is a little fluid sac that helps the muscles and tendons slide freely as the knee moves.

There are two cruciate ligaments located in the center of the knee joint. The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are the major stabilizing ligaments of the knee. The posterior cruciate ligament prevents the femur from sliding forward on the tibia (or the tibia from sliding backwards on the femur). Whilst the anterior cruciate ligament prevents the femur from sliding backwards on the tibia (or the tibia sliding forwards on the femur). Most importantly, both of these ligaments stabilize the knee in a rotational fashion. Thus, if one of these ligaments is significantly damaged, the knee will be unstable when planting the foot of the injured extremity and pivoting, causing the knee to buckle and give way. When the knee is unstable, athletes often complain of a sensation that the knee will ‘give way’ from under them, this sensation is because of an ACL injury, the knee is sliding to much. This can be a problem because each episode of instability (the ‘giving away’ sensation) can cause damage to the knee cartilage. Therefore an ACL injury makes athletes more prone to developing arthritis and meniscus tears.

Many sports require a functioning ACL to perform common manoeuvres such as cutting, pivoting, and sudden turns. These high demand sports include:

  • Football
  • Soccer
  • Basketball
  • Skiing
  • Gymnastics
  • Hockey (Ice and Field)
  • Wrestling
  • Lacrosse
  • Rugby

‘Damage to the knee structures can increase the risk of developing secondary osteoarthritis and possible long-term disability. Such severe knee injuries may require changes in sports or work activities that usually place high functional demands on the knee’ (Platzer, Werner 2004). They also stated that over the past decade, the diagnosis and management of knee disorders have been refined significantly. These advances have greatly improved the ability to persevere knee function, allowing patients to return to their desired level of sporting activities. The treatment of anterior cruciate ligament ruptures has been revolutionised with new surgical techniques being introduced allowing for more aggressive rehabilitation. Arthroscopic treatment of the meniscus (shock-absorber cartilage) now encompasses repair as well as more limited excision compared to traditional techniques in which the whole meniscus was removed through an open incision. Subsequently more meniscal tissue can be preserved, which is vital in reducing the level of force transmitted through the knee joint.

Of all body joints, the knees are the most susceptible to sports injuries because of their high reliance nonarticular factors for stability and the fact that they carry the body’s weight. The knee can absorb a vertical force equal to nearly seven times body weight. However, is very venerable to horizontal blows, such as those that occur during blocking and tackling in football. ‘When thinking of common knee injuries, remember the three Cs: collateral ligaments, cruciate ligaments, and cartilages (menisci)’ (Elaine N. Marieb, Katja Hoehn 2007). Most dangerous are lateral blows to the extended knee. These forces tear the tibial collateral ligament and medial meniscus attached to it, as well as the anterior cruciate ligament. It is estimated that 50% of all professional football players have serious knee injuries during their careers.

Although less devastating than the injury just described, injuries that affect only anterior cruciate ligament (ACL) are becoming more common particularly in women’s sports become more vigorous and competitive. Most ACL         injuries occur when a runner changes direction quickly, twisting a hyper-extended knee. A torn ACL heals poorly, so repair usually requires a ligament graft using connective tissue taken from one of the larger ligaments (e.g. semitendinosus).

Technology is evolving

Technology has been evolving within sport for years for example in ice hockey we have the evolution of the hockey stick, the already dangerous sport of hockey quickly became even more dangerous. Originally hockey players wore little protective gear besides gloves and skates but with better sticks came harder shots and a more fast paced game which caused many injuries.

Up until recently, tennis has relied on the keen eye of just their officials to make the calls on the court. Now there are a few systems being used to ensure the correct call is made every time.

The first is Cyclops, it is used to determine if serves are in or out. The machine projects five or six infra-red horizontal beams of light along the court 10 mm above the ground to determine this. The ball will break the plane of the infra red beams if it is out of bounds.

The Hawkeye technology is used to judge whether a ball is in our out. In 2005 it was tested by the ITF and certified for professional use. The system uses a computer linked to a network of cameras to recreate the balls path and judge to the millimeter if the ball was in or not. The implementation of the Hawkeye technology has led to players receiving a number of challenges to use when they believe a shot may have been called incorrectly. In March of 2008, the ITF set the standard for Hawkeye challenges at 3 per set for players. This technology now has given players the ability to challenge critical decisions and ensure they are rewarded for their efforts.

Manufacturers in every sport are continuously trying to upgrade and improve their equipment, and the athletes themselves are striving to take their performance to the ultimate level.

Taking drugs to enhance performance is a covert and illegal activity. But if you are using for example, high performance swimsuit it's legal and it's pretty obvious that's what you're doing. Speed skaters used to skate with a fixed skate and then somebody had the idea of hinging the blade so that as you pressed on the ball of your foot it kept the blade in contact with the ground, acting like a clapperboard. It meant the skate was always in contact with the ice so that the skater is always pushing.

How can we measure human movement?

Human movement and joint analysis can be measured in a variety of ways. Firstly we have gait analysis. Gait analysis is commonly used to help athletes run more efficiently and to identify posture-related or movement-related problems in people with injuries. Video Gait Analysis can help to identify any biomechanical inefficiencies in an athlete’s running style, that may cause injury problems if wearing shoes that do not suit the way they run.

In addition, any existing injury problems brought on through running can often be explained and understood through a gait analysis, common problems identified include:

 Fallen/Collapsed Arches


 Leg Length Discrepancies

 Knee Alignment

 Shoulder Alignment 

Another way we can measure movement is by pressure measurements, ‘they provide a good indication of how the foot or shoe contacts with the ground and transfers load during ground contact and fast lateral to medial plantar loading  transitions have been related to rearfoot motion’ (Hagman, 2002). Planter pressure measurement systems are able to record plant loading transitions at high data acquisition rates and therefore have the potential to predict rapid movement characteristics of the foot and lower leg. This would open up the possibility of using a relatively simple measurement approach (pressure mat) to estimate movement transients during running that may be associated with the risk of overuse injury.

Rugby analysis

Rugby has developed over the years in terms of technology, with rugby as its been played now, fast and a high intensity game, we now have the technology in place to help the referee to make crucial decisions and help players themselves improve their game with video analysis. One new peace of technology in place is the ‘sports performer’. Many of the top rugby clubs in England and Wales have implemented a new video analysis software package into their training program, designed to enhance the development of its high performance players. Sport performer is a state-of-the-art analysis program which allows the academy coaches to break the game down into numerous components, from targeting individual performance and set-piece plays, to gaining an overall analysis of a team’s playing patterns.

It’s a software package where you can specify exactly what you want out of the game. You don’t have to code redundant information; with Sports Performer you can mould the information that’s specific to your style of play. As opposed to the standard statistics you get on TV during a test match, Sports Performer gave you detailed key performance indicators which were far more informative and relevant to a player’s or team’s performance. The TV stats that you see at half time often aren’t a good reflection of what’s happening on the field as they just reflect the opinions of the commentators. With Sports Performer you’re able to get key performance indicators that really help to focus on the details of your game. If your game is about dominating at the set-piece and that’s where you launch your attack from, over a number of games you’ll get to a point that denotes where you win. It may be that if you get 70% of quality set-piece, anything above that you win and anything below that you lose. So that’s where the key performance indicators you get from Sports Performer are so relevant to your game. This extremely effective in improving team performance. If you’ve got four or five things as your key performance indicators, it's powerful stuff to give teams at half time, because rather than getting stuck into them and complaining about their poor half, you can give them crucial information as to how to improve things so they can hit their targets.  There are some ridiculously priced programs out there, but Sports Performer is really economical.

The modern game of rugby union places high physical stresses on the knee joint e.g. Garraway et

al (2000) reported that in Scotland’s border region 26% of all injuries (in senior amateur clubs) were sustained by the knee. Ligament damage is the most common type of knee injury pathology (Webb and Corry, 2000) and of the intra-articular knee ligaments the anterior cruciate ligament (ACL) is most frequently injured (Johnson, 1983; Steele, 1999). In rugby union the ACL injury rate has been determined at 0.07 per 1000 ‘exposures’ for men and 0.36 per 1000 ‘exposures’ for women (Levy et al., 1997). With an estimated 500,000 adults playing each week in England alone (The Rugby Football Union, 2001) a substantial amount of ACL injuries will be sustained during the course of a season. The ACL provides 86% of the resistance to anterior displacement and 30% of the resistance to medial displacement of the tibial condyles (Palistanga et al., 1998). It also limits hyperextension and acts as a restraint to varus or valgus angulation, and when the knee is near full extension, internal and external rotation (Webb and Corry, 2000). Therefore, ACL deficient knees are more prone to ‘giving way’ when performing ‘cutting manoeuvres’ whereby there is a rapid change in direction, usually at speed (e.g. a side-step). ‘Rugby is classed as a high-risk (level 1) activity and participation is discouraged for ACL deficient individuals’ (Webb and Corry, 2000). Subsequently after an ACL rupture a reconstruction is generally required in order to return to competitive participation. Different player positions in rugby union may place different demands on the ACL as Player position and ACL reconstruction in rugby union regards to these ‘cutting manoeuvres’. For instance the stresses may be greater for a member of the back line who tend to perform ‘cutting manoeuvres’ at higher running speeds compared with front row players. To date, there is little research investigating the demands of a sport on the functional stability of the ACL deficient knee and the implications after reconstructive surgery.


Technology has not only helped with improvement in sports clothing and equipment design but it has helped in the way that athletes train and the way the trainers understand the human body.

The understanding of science and the human body has helped coaches and athletes to approach and break records. Top athletes will now not only have a top class trainer working with them but will also have the knowledge base of top scientists from such fields as physiology, psychology, nutrition and biomechanics all helping to improve the athlete. These are all things that the athletes or the 1960's and 70's had to do without.


Kreighbaum, E., Katharine, B.M. (1996). Biomechanics; A Qualitative Approach for Studying Human Movement, Allyn & Bacon.

Mark, R. Mark, L. (2006).Plantar pressure measurements during barefoot and shod running – relationships to lower limb kinematics. Liverpool John Moores University, U.K

Palastanga, N., Field, D. and Soames, R. (1998). Anatomy and Human Movement, structure and function. 3rd edition. Butterworth-Heinemann.

Webb, J. and Corry, I. (2000). Injuries of the sporting Knee (series). Knee instability: isolated and complex British Journal of Sports Medicine.

Jamie Williams

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