Biomechanics is the study of the mechanical principles of movement in living organisms. Think of the body as a machine, where bones act as levers, joints serve as pivot points, and muscles function as the motors that generate the force needed to move these levers. These components allow for every action from breathing to complex acrobatics. These mechanical factors govern all human movement, determining our efficiency, power, and stability as we navigate the physical world.
Core Components of Biomechanics
Biomechanics is divided into two main branches. The first is kinematics, which describes motion without considering the forces that cause it. Kinematics quantifies variables like the position of a limb, the velocity of a swinging arm, or a runner’s acceleration. For example, a kinematic analysis could describe the angle of the knee joint during a kick or the trajectory of a basketball to the hoop.
The second branch, kinetics, studies the forces that cause or change motion by analyzing internal and external forces. Internal forces are generated by the body, primarily through muscle contractions. An example is the force your bicep generates to lift a heavy bag. External forces originate outside the body and include gravity, air resistance, and the ground reaction force exerted by the ground back on the body. When you jump, the impact you feel upon landing is a direct result of this ground reaction force.
Influence on Human Movement and Performance
Optimizing biomechanics improves physical performance through movement efficiency, which is producing maximum output with minimum energy expenditure. When movement is efficient, less energy is wasted on counterproductive motions, allowing an individual to perform better and for longer.
In running, factors like stride length, cadence (steps per minute), and foot strike pattern are analyzed for speed and endurance. Overstriding, where the foot lands too far in front of the body’s center of mass, creates a braking force and increases impact shock. Adopting a shorter stride with a higher cadence can reduce these braking forces and improve running economy.
This principle extends to strength sports like powerlifting, where a lifter’s technique influences how much weight they can safely move. A powerlifting-style squat with a wider stance and a low-bar position increases the torso’s forward lean. This adjustment shifts the mechanical load to the hip muscles, allowing the lifter to handle greater loads. In sports involving throwing or swinging, athletes use sequential coordination to generate power, transferring energy from larger segments like the hips and torso to smaller, faster segments like the arm and hand.
Role in Injury and Rehabilitation
When body mechanics are faulty, the risk of injury increases. Poor biomechanics can lead to injury through a single traumatic event or repetitive stress. This happens when forces applied to tissues like muscles or bones exceed their capacity to absorb the load.
Repetitive stress injuries often develop from sustained postures or movements with improper form, such as neck and back pain from poor desk ergonomics. A forward head posture increases the mechanical load on the cervical spine. This forces the neck muscles to work constantly to support the head’s weight, leading to muscle imbalances and pain.
Acute injuries can also result from flawed biomechanics during high-speed movements. Many non-contact ACL tears in the knee occur when landing from a jump or rapidly changing direction. These injuries often happen when an athlete lands with a relatively straight knee that collapses inward (knee valgus). This alignment creates rotational forces on the knee joint, stressing the ACL beyond its breaking point.
Rehabilitation relies on biomechanical analysis to identify and correct the mechanical faults that contributed to the injury. This involves retraining movement patterns, strengthening weak muscles, and improving flexibility to restore proper joint function. Addressing the root biomechanical cause helps facilitate recovery and reduce the risk of future injury.
Assessment and Modification of Biomechanical Factors
Professionals assess biomechanical factors using methods ranging from simple observation to laboratory technology. A physical therapist or coach can perform an observational gait analysis to identify asymmetries or inefficient patterns as a person walks or runs. For a detailed evaluation, clinicians use tools like high-speed video motion capture to measure joint angles and velocities. Force plates are another tool used to measure ground reaction forces during activities like landing, providing data on the loads the body experiences.
Once inefficiencies are identified, several strategies can modify them. Corrective exercise involves strengthening weak muscles and stretching tight ones, such as strengthening the gluteal muscles to improve hip stability. Technique coaching refines the form of specific movements, like a running coach guiding an athlete to increase cadence. Ergonomic adjustments modify a person’s environment to better fit their body, such as adjusting an office chair’s height. These modifications work together to improve movement quality.