Mechanics is a branch of physics that is concerned with the description of movement and how forces create motion and movement. Biomechanics is the study of how living things move.  Sport biomechanics is the science of explaining how and why the human body moves, specifically athletes engaged in their sport activities (Brukner et al, 2014). Within this specialized field of biomechanics, the laws of mechanics are applied in order to gain a greater understanding of athletic performance.  This would include the interactions between the athlete, their equipment and the environment.

Biomechanics is traditionally divided into the areas of kinematics and kinetics.

Kinematics is the branch of mechanics that deals with the geometry of the motion of objects, including displacement, velocity, and acceleration (without taking into account the forces that produce the motion). Examples would be walking, or a soccer kick, including the major joint actions such as hip flexion, knee extension and possibly the flexion at the ankle.

Kinetics is the study of the relationships between the force system acting on a body and the changes it produces in body motion (Hall, 2019).   In terms of this, there are skeletal, muscular and neurological considerations we need to consider.  Examples would be lifting a barbell:  the barbell produces a moment of force acting on your forearm (Brukner et al, 2012). 

The ground is the primary source of power for just about every skill.  Newton’s third law states that with every action, there is an equal and opposite reaction.  That initial action is the athlete applying force into the ground, and the ground responds by applying that force back onto the athlete.  The athlete takes this ground force and uses individual segments to create unique coordinative patterns that transfer that force to a desired end point (hitting hand, kicking foot, etc.) (Gearssports.com, 2024).

How well we move our segments at a specific speed and time, creates an ideal movement pattern that is referred to as a Kinematic Sequence.  When your kinematic sequence is correct, you are in the right biomechanical window to achieve peak skill execution because your body has maximized the amount of ground force that is transferred through to your desired point. When your sequence is off, this leads to inconsistency, inaccuracy, injury, and overall poor performance.

How you apply force into the ground dictates much of what will become of your movement.   Which muscle groups are activating? How quickly? In what order?  This pattern is your Kinetic Sequence.  It is how your body is absorbing the ground force and transferring it to the next segment.  Your body’s ability to transfer this force in a specific way plays a huge role in the successful execution of your skills.

By analyzing sports biomechanics, changes can be implemented to improve and enhance sports performance, rehabilitation, and injury prevention.

Incorrect technique can cause abnormal biomechanics which can lead to injuries. For example, pace bowler cricket players (similar to a baseball pitcher) with problematic mechanics are at risk for the injury pars interarticulars a fracture of a bone in the spine (Forrest et al, 2017).   A study of fast pace bowlers showed they generally adopted a hyper-extended spine as they prepared to deliver the ball.  An average of 8X force is transmitted through the body for every bowl bowled by a fast bowler – the majority falling on the front foot during the delivery stride. This force when coupled with the extreme range of lower back movement puts the lumbar spine at high risk of injury. Given the repetitive nature of this physical activity, the probability of overuse injury is high due to the longer duration of stress the body undergoes. This is also exactly the reason why lower back stress fracture happens to be the most common type of injury suffered by fast bowlers.

Tennis players need to ensure their swing incorporates their body core and lower legs into the stroke properly so the lower body/core can load the energy and transfer load and energy up the kinetic chain into the arm and wrist to abate some of the wrenching of the body about a longitudinal axis.  Otherwise, they are at risk for wrist extensor tendonitis (Stuelcken et al, 2017).  This is an excellent example of how kinetics matter.  In tennis, the wrist/hand complex forms the crucial final link in the kinetic chain between the body and the racquet and is very important in the production of a tennis stroke.  While the loads experienced at the wrist during tennis stroke production seem to be below threshold levels for a single event, the cumulative effects of these loads through repetition would appear to be an important consideration, especially when inadequate time is allowed to complete normal processes of repair and adaptation.

The sport of running has a very high degree of repetitive motion, making it very important for the mechanics to be correct.  The knee and the ankles are the most commonly injured sites. For runners, abnormal running mechanics can result in the stabilizing muscles (glutes, hips, and core) working excessively hard and over contracting, causing increased load to the tendons and shin bone.  One example would be heel striking with your foot, rather than running on the front third of the foot.  Or incorrect footwear which can affect posture and biomechanics (Goom et al, 2016).

Humans are dynamic bodies, that respond to their environment, and which change over time.  It is inevitable that an athlete’s mechanical form in their sport will evolve intentionally through training, and unintentionally via psychomotor changes. Understanding the nuances of the mechanics of your sport, and of your body in engaging your sport can help you sustain your performance over time.

As an individual athlete it can be difficult to track one’s own mechanics.  In that regard a coach or even a team member can be helpful to watch your movement patterns, and give you feedback.  Also, it can very useful to be filmed so you can watch your own technique and movements and try and make adjustments.

References

Brukner P. 2014.  Brukner and Khan’s clinical sports medicine.  4th ed.  North Ryde, Australia:  McGraw-Hill.  ISBN-13978-0-07099-813.1

Forrest MR, Hebert JJ, Scott BR, Brini S, Dempsey AR. Risk factors for non-contact injury in adolescent cricket pace bowlers: a systematic review. Sports medicine. 2017 Dec;47(12):2603-19.

Goom TSH, Malliaras P, Reiman MP, Purdam CR.  Proximal hamstring tendinopathy:  clinical aspects of assessment and management.  J Orthop Sports Phys Ther.  2016 Jun;46(6):83-93.

Hall SJ. 2019. Equilibrium and human movement. In: Hall SJ. Basic Biomechanics. 8th ed. New York:  McGraw-Hill. 

Stuelcken M, Mellifont D, Gorman A, Sayers M. Wrist injuries in tennis players: a narrative review. Sports medicine. 2017 May;47(5):857-68.