Biomechanics. Flashcards
Define Biomechanics
study of human movement that applies physics and mechanics to enhance performance, optimize movement, and improve safety. It analyzes forces to correct inefficiencies, maximizing power, speed, and accuracy while reducing injury risk and aiding rehabilitation.
Motion
refers to movement and the path of a body e.g. human body: the speed an athlete runs during a race or manipulation of an object by the human body e.g. javelin thrown in the air. 3 types: linear, angular, general
Linear motion
Movement of the body in the same direction, time and speed. e.g. ski jumping. swimmers gliding off a wall. Efficient linear motion: reduces resistance, allows athletes to maintain speed and conserve energy. Aids in performance directed towards achieving shortest most efficient pathway: poor application = swimmers who use an irregular arm pull.
Angular motion
Rotational movement around an axis e.g. gymnast rotating around a high bar. Greater angular velocity can improve performance in rotational movements, such as faster spins in gymnastics or powerful pedal strokes in cycling. inhibit performance for those trying to achieve linear motion
general motion
A combination of linear and angular motion e.g. Bowling a cricket ball combines running (linear) and bowling (angular). Combining both motions efficiently enhances movement fluidity and power, leading to more effective performance in sports actions.
Speed
speed = distance/time. A player who can move quickly has a distinct advantage in games such as touch football, rugby and soccer because not only is that player difficult to catch, but they can use their speed to pass opponents quickly in defence. Speed potential = genetic type of muscle fibres in body. Can also be developed in the faster rotation of joints e.g. in the sprinter, the hip and shoulder joints require rotation of the arm and legs. The faster a sprinter moves their arms and legs through the contraction of muscles pulling on the bones to generate movement, the more speed will be generated.
Velocity
Velocity refers to the speed of an object in a given direction: the rate of positional change of an object. V= displacement/time
Acceleration
refers to the rate of change in speed of a moving object e.g. when moving from a jog to a sprint someone is positively accelerated as speed is increasing. When they are slowing back down, they are negatively accelerating as speed is decreasing. E.g. In a sprint start, the quadriceps, hamstrings, gastrocnemius, and glutes contract to generate force for acceleration. Abdominal muscles provide stability, while hip and shoulder joints enable arm and leg movement to maintain speed.
Angular momentum
Combines the understanding of angular motion and momentum. Athletes that rely on rotational movements to generate power such as in golf see that if the object (club) is greater in mass (heavier) it will generate a greater angular momentum and thus produce more force that is transferred into the ball. That is why drivers tend to be heavier than a 9 iron club as the driver is intended to hit the ball further.
Balance and stability
Balance (ability to maintain a stable position) and– are the alignment of the body’s centre of gravity over the base of support. 2 types: static – maintain balance while stationary e.g. defending netball shot and dynamic – maintain balance while moving e.g. cartwheel on a beam
Stability: the ability to resist being displaced or moved
Vital for movement and sport performance assisting with skill execution. By effectively contracting muscles to secure joints while using bones as structural support you can optimise your body’s ability to stay upright and avoid falls.
Centre of gravity
the point at which all the weight is evenly distributed and about where an object is evenly balanced. Knowing the position of the COG is very important to improving movement in sport e.g. athletes adjust their body as they are moving to ensure their COG is balanced to prevent them from falling over e.g. High jumpers lower their centre of gravity in the steps before take off to help them propel their body over a vertical path. E.g. static activites: to balance on your hands and head in a head stand the COG must be controlled by base support. If it moves away from a perpendicular position directly over the base you’ll fall.
Base of support
imaginary line drawn around all parts of the body in contact with the ground at any given point. Affects stability and control of equilibrium. Narrow: only small force is needed to make one loose balance work hard to ensure COG remains within the base e.g. pirouettes. Wider = essential for stability COG remains well within the boundaries e.g. wrestlers widen base to prevent opponents from moving them into disadvantageous positions enhance balance. e.g. standing on one leg decreases your base of support whilst lowering your centre of gravity and standing on 2 feet spread apart increases your balance and stability
fluid mechanics
the movement of a body through liquid (water) or gas (air), and the forces that affect it. It plays an important role in understanding efficient movement: helping to reduce drag and fatigue. Understanding fluid mechanics = important for movement as physical activities e.g. running and swimming all take place in fluid environments.
Fluid mechanics principles leading to efficient swimming
Materials like polyethylene and carbon fibre improve body position in water, reducing wave drag. Modern swimsuits use carbon fibre and polyethylene, which trap tiny air pockets, increasing buoyancy. Swimsuits minimize frictional drag (caused by water clinging to the body). Streamlined Body Position: Swimmers often practice maintaining a streamlined position to reduce drag. Techniques such as tucking the chin and keeping the body straight are crucial for effective streamlining
Flotation
The ability to float on the surface of a liquid. The body’s buoyancy depends on factors like body composition, muscle tension, and position in the water. e.g. Swimmers use body position to maximize flotation and reduce drag. improved flotation helps reduce energy expenditure allowing athletes to maintain better endurance and efficiency in the water.
Centre of buoyancy
the centre point of the mass below the water and is the point in an object or body where the buoyant force acts. A body that is denser than water will sink. The centre of buoyancy shifts with changes in body position. A stable centre of buoyancy helps athletes maintain streamlined positions, reducing resistance and improving control in the water. e.g. Swimmers adjust body position to manipulate the centre of buoyancy and control depth. To float, a swimmer must maintain a streamlined position by contracting muscles, especially the abdominals, to keep the core at the water’s surface. Muscle action, bone movement, and joint rotation aid buoyancy. Minimal joint angles in the shoulders and hips help keep limbs close to the body for optimal streamlining.
Fluid resistance
The force opposing movement through a fluid (water or air), which slows down motion. It includes drag and lift forces. Reducing fluid resistance improves speed and efficiency –> helping athletes move more effectively through water or air with less effort. Cycling: The superman position minimized frontal area, reducing form drag and allowing smoother airflow around the body.
* The hand position adjustment improved streamlining, reducing turbulent airflow and pressure drag, which helped decrease aerodynamic resistance and increase speed
Drag
force that opposes the forward motion of a body or object reducing its speed or velocity. Drag forces run parallel to flow direction (airflow, water), exerting a force on the body in the direction of the stream. E.g. when a swimmer pushes off the pool wall following a turn. The swimmer’s forward motion gradually decreases due to resisting forces applied by the water, which makes the swimmer stop unless arm or leg action begins. A body that is streamlined (contoured to reduce resistance) and technically efficient moves through the medium, creating less drag than a body that is not as streamlined.
Lift
the component of a force the acts at right angles to the drag. Propels swimmers forward in the water, they can harness this force to improve movement. To create life they must: maintain streamlined position (head in line w body), engage abdominal muscles (keep body in streamlined position), keep the hands in a sculling position (acts to catch the water and push it past the swimmer)
Newtons 3 laws of motion
- Newton’s 1st law – an object remains at rest or in constant motion unless acted upon by an external force
- Newton’s 2nd law – the acceleration of a body is directly proportional to and in the same direction as, the force acting on the body.
- Newton’s 3rd law – when one body exerts a force on a second body, the second body simultaneously exerts a force that is equal and opposite in direction to that of the first body.
Force
is a push or pull that causes a person or object to speed up, slow down, stop or change direction. The body applies force, the body absorbs force, the body can apply force to an object.
Kinematics
The study of objects in motion and how technique adjustments can increase the efficiency of motion to achieve a greater outcome
Kinetics
The study of the body that creates force and how this relates to the object being acted upon
Magnus force effect
he force exerted on a spinning object moving through a fluid (air or witer) causing it to curve in it’s trajectory. The rotation of the object causes the air to move faster on one side and slower on the other. The side with faster airflow has lower pressure, while the side with slower airflow has higher pressure. The object moves toward the low-pressure side, resulting in a curved path.
Safe movements
Unsafe movements can cause significant damage to the body through body acute (sudden) and chronic (gradually over time) injuries. Biomechanical principles and analysis can be applied to ensure the forces that are impact on the body minimise the risk of injury.
Barbell squat
Correct technique in a barbell squat prevents injury, particularly to the lower back. Proper body positioning and joint alignment—knees bent and apart—provide a stable base. A wider base and lower centre of gravity improve stability and allow greater force generation increasing stability, reducing fall risk. Similarly, a small shoulder joint angle can cause imbalance. Keeping knees soft throughout prevents stress on the joint, protecting cartilage and tendons. At top of the dead lift activate your glutes to relieve your hamstring. Pelvis and vertebra aligned to minimise forces going through joints
Movement efficiency
Athletes aim to perfect technique to enhance movement efficiency, which involves optimizing motor patterns to use just the right amount of force while conserving energy. Efficient movement allows athletes to perform actions with minimal effort and reduced fatigue.
* A more efficient runner uses refined technique to maintain speed with less energy, enabling them to sustain performance longer.
* A weightlifter with proper mechanics, engaging hips rather than the lower back, lifts the same weight more efficiently, reducing energy expenditure and injury risk.
* Inefficient swimmers create more drag due to poor body positioning, requiring extra effort to move through the water.
Biomechanical analysis, often using video software, helps identify inefficiencies, allowing athletes to refine technique for optimal performance.
Safety in regards to force
one of the major principles that can help prevent injury and make movements safer. e.g. Wearing pads in cricket to absorb some of the force of the ball when it hits the players legs. E.g. rugby tackles: broad base and using muscles such as the quads and pecs to absorb force and avoid being unstable. headgear absorbs and distributes force…
Specific needs of athletes w disabilities
Biomechanics can assist athletes with disabilities to develop better movement efficiency, technique and performance. The advancement of technology and understanding of biomechanical principles has led to the development of specialised equipment to support performance.
Wheelchair racing
E.g. wheelchair racing: aerodynamic frame – reduces air resistance for higher speeds, three-wheel design – streamline she minimises drag, extra wheel adds stability, Tilted rear wheels – Improves balance, prevents tipping, and enhances force transfer. Lightweight carbon fibre – Less energy required to accelerate and sustain speed –> decreases friction. In order to obtain maximum momentum, the athlete must be able to apply a large force through the arms to the rim of the wheels, which will generate speed. The development of upper body strength is important for wheelchair athletes to help with their movement.
Buoyancy
Buoyancy is the upward force exerted by a fluid on an object, allowing it to float or appear lighter in water. body composition, muscle tension positioning.
Absorb forces
Our body absorbs force by transferring the force to our muscles, where contractions in the opposite direction absorb the force. n order to absorb large forces safely, our body seeks to absorb the force by increasing the time of absorption, increasing the movement length used to absorb the force, or increasing the area in which the force is absorbed. The body will also apply a force in the opposite direction, usually using an eccentric contraction. Safety of landing in netball: the athlete can make the eccentric contraction go for longer by allowing a larger bend at the joints. Alternatively, the muscles can create a more forceful contraction to absorb more force over s shorter period, though this is harder to control. Catching a baseball: The force from the ball is absorbed by the body through eccentric contractions in the shoulders, trunk and arms. These contractions absorb the force over a longer period of time, making it easier to control and increasing the chances of the athlete holding onto the ball.
applying/creating force
How the body applies force particularly relates to Newtown’s third law: for every action (force) there is an equal and opposite reaction. In order for our bodies to move, either upwards or horizontally (downwards is caused by gravity most of the time), we need to apply forces to the ground and then move as a result of the equal and opposite reaction force.
The body creates force by manipulating the gravitational force on the body and by generating force using its muscles. Muscular contraction provides the force used to create movement around joints. Most of the forces of the body act using a lever system which converts a smaller input force (from your muscles) into a larger output force.
sprinting events it is important for the athlete to get out of the blocks quickly. For this to happen, the athlete needs to apply a force in a downward and rear direction in order to have a reaction force that propels them forward. In order to increase this force, the athlete gets low to the ground and angles their body forward so that they can generate a larger force in the backwards direction and accelerate their body in a forwards direction
