Biomechanics – understanding the terms that make our bodies move

One of the under-utilised ways for an individual to improve their fitness is to acquire a deeper understanding and knowledge of biomechanics. This is because the greater the understanding of how the body moves and the capacity of joints, bones and ligaments to perform certain actions, the easier it is to improve the execution of the movements required for each specific exercise or sporting activity.

Individuals who incorporate proper biomechanics are able to pursue their potential to its highest level and help minimise the potential for injury; be that as a sports professional or a recreational exerciser aiming for improvements in fitness and everyday wellness.

Another reason is that demystifying the language used by fitness professionals leads to greater understanding by participants. It’s not unusual for sports instructors to assume that what they think of as everyday fitness terms are commonly understood by participants, who in reality find them confusing. Individuals may feel reluctant to seek clarification because they don’t want to appear uninformed. Moreover, instructions on some sports equipment can refer to biomechanical terms and positions, so understanding what they mean will make it easier to get the most out of the equipment.

Analysis of the mechanics of human movement is referred to as biomechanics. It is the science of explaining how and why the human body moves in the way that it does. This includes the interaction between the performer and his or her equipment and environment. Biomechanics plays a major part in the design that goes to produce the Technogym range of equipment.

A good example of how biomechanics has been used to provide comfort and functionality for the user is Unica. Designed and built with the same materials as professional gym equipment, with a refined and elegant design, Unica is the most comprehensive physical fitness and muscle-strengthening equipment that exists. The compact design allows more than 25 different exercises to be done in just one and a half square metres, without substituting any part of the machine. Biomechanics and the easy start system allow correct, safe use of the equipment whatever the user’s experience.

Among biomechanics we can find the concepts of kinetics (the analysis of the forces acting on the body) and kinematics (the analysis of the movements of the body). Five important components in biomechanics are motion, force, momentum, levers and balance:

Motion is the movement of the body or an object through space. Speed and acceleration are important parts of motion.

Force is a push or pull that causes a person or object to speed up, slow down, stop or change direction.

Momentum is the product of a weight and its velocity when moved.

Levers Our arms and legs act as levers; there are three parts to a lever – the resistance arm, the fulcrum, and the axis of rotation.

Balance is about being stable. An important principle of balance is the alignment of the body’s centre of gravity over the base of support. Having a good balance is important for many sporting and exercise activities.

 

In biomechanics, every motion of the body is described starting from the anatomical position. The anatomical position is when a person is standing upright looking straight ahead, arms at the side with palms facing forward, the feet slightly apart at the heels, and toes pointing forward. There are three anatomical or Cardinal planes in the anatomical position, as described below.
The sagittal or median plane divides the body into two sides (left and right), with a few exceptions: motions of flexion (decreasing the angle of a joint/bending the joint) and extension (increasing the angle of the joint/straightening the joint) occur in the sagittal plane.
The second division of the body is the frontal or coronal plane, which bisects the body into front and back portions. Again, there are a few exceptions: motions of abduction (moving a limb away from the centre/medial line of the body) and adduction (moving a limb towards the centre/medial line of the body) occur in the frontal plane.
Finally, the transverse or horizontal plane divides the body into upper and lower portions. Movements of rotation occur in the transverse plane. Diagonal patterns of movement occur when components of all three cardinal planes of motion are combined at the same time.

 

The axes of the body are straight lines running through the body like arrows, perpendicular to each other. Whereas the cardinal planes are used to describe the spatial zones in which the body moves, the axes describe the main pivotal/rotational points of body movement. The three main axes are:

 

Transverse, which runs left to right through the waist area.

Longitudinal, which runs directly through the centre of the body from head to toe.

The Medial axis, which joins the hips and the shoulders diagonally.

 

The following terms are used to describe specific movements of the body that occur in the cardinal planes and along the axes. Some of them have slipped into everyday language so it is helpful to be familiar with these terms as they are frequently included in exercise instructions:

 

Dorsiflexion - decreasing the angle of the ankle joint

Plantarflexion - increasing the angle of the ankle joint

Elevation - moving a body part in a superior (towards the head) direction

Depression - moving a body part in an inferior (away from the head) direction

Eversion - rotating the ankle so that the sole of the foot points away from the other

Inversion - rotating the ankle so that the sole of the foot points towards the other

Lateral rotation - rotating them away from the centre/medial line of the body

Medial rotation - rotating a limb towards the centre/medial line of the body

Pronation - rotating the forearm so that the palm faces down if the forearm is flexed

Supination - rotating the forearm so that the palm faces up if the forearm flexed

Retraction - posterior movement (towards the back of the body) of the arm at the shoulder

Protraction - anterior movement (towards the front of the body) of the arm at the shoulder

Lateral flexion - bending the spine to the side, away from the centre/medial line of the body

 

Another important concept to grasp in understanding how the body moves is articulation. Articulation is the movement of two or more bones at a joint. There are three types of joints in the body, but the one that provides the greatest range of movement, and so is fundamental to understanding how the body moves, is the Synovial joint.

 

Synovial joints are where the bone is separated by a lubricating fluid and cartilage. Synovial joints are typified by having a relatively large range of motion. The nine basic features of synovial joints are:

 

  1. Articular Cartilage
  2. Ligaments
  3. Tendons
  4. Muscles
  5. A Synovial Membrane
  6. Synovial Fluid
  7. Bones
  8. A fibrous capsule
  9. A joint cavity

 

There are six types of synovial joints in the body:

Ball and Socket - this is the champion of all joints. Made up of a ball, which fits snugly into a socket, its structure allows movement in all axes: flexion, extension, abduction, adduction, rotation and circumduction (a combination of all the others in a circular motion). The two ball and socket joints of the body are at the hip and at the shoulder. The hip joint has a deeper socket, which gives its stability but limits the range of motion. The shoulder has a shallower joint, which gives it a wider range of motion but reduced stability, and is one of the reasons why a dislocated shoulder is so common.

Gliding/plane - two flat surfaces sitting one on top of the other. These surfaces can glide or rotate. Examples of these joints are found in the feet and hands.

Hinge - a very simple joint that allows movement in only one axis as its structure prevents rotation. The hinge joint allows flexion and extension, for example at the elbow.

Pivot - this allows rotation along one axis; the long axis. It is the pivot joint connecting the radius bone to the elbow that allows the forearm to rotate (pronation and supination).

Ellipsoid - very similar to a ball and socket, however its ligaments and oval shape prevent rotation in all axes. That said, it still has the ability to rotate on two axes, which allows flexion, extension, abduction, adduction and circumduction, for example as in the wrist.

Saddle - similar to the ellipsoid but its rotation is limited by the bones’ structure/shape. One of the bones forming the joint is shaped like a saddle with the other bone resting on it like a rider on a horse. The bone sitting on the saddle can flex, extend, abduct, adduct, circumduct and very slightly rotate. The thumb joint is an example of a saddle joint.

 

The other type of joint that allows movement is a cartilaginous joint. Here bones are joined together by either hyaline cartilage or fibrocartilage. These joins have a limited range of motions for example the ribs and the spin.

The classic trade off for joints is increased flexibility leads to decreased stability. Where this occurs as a result of wishing to increase flexibility for improved sports performance (stretching, yoga), this can be compensated to some extend by strengthening the muscles around the joints.

The science of biomechanics plays a major role in improving the performance of both individuals and sports equipment. Whilst it would take many years to become a specialist in biomechanics, having a basic understanding of the more common principles can help those participating in exercise and sports to manage their bodies effectively.