The Study Of Human Movement Biology Essay

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Kinesiology is the study of human movement while Biomechanics is defined as the study of the movement of living things using the science of mechanics ( Hatze, 1974). The principal objective in the latter is how forces on biological systems create movement. Forces on living organisms originate motion, being it healthy due to growth, or unsatisfactory due to the overloading on tissues leading to injuries. [1]

In other words Biomechanics provides essential knowledge on the most adequate and harmless movement patterns, facilities and applicable exercises to enhance human movement. Since kinesiology professionals deal with human movement every day, Biomechanics is their most important tool which allows them to improve movement or make human movement safer.

2.1.2 Why study Biomechanics?

Scientists from different fields (e.g., kinesiology, engineering, zoology) tend to show a strong interest in biomechanics. Within kinesiology, biomechanists have applied biomechanics in the world of sport and exercise. The utilisation of biomechanics can be divided into two main fields: the enhancement of performance and the reduction of injury. Enhancing Performance

Biomechanics is most appropriate where technique is the principal asset compared to the physical aspect thus enabling kinesiology professionals to assign technique changes and deliver instructions to better performance.

In essence biomechanics is the science of movement technique, thus biomechanics is the fundamental contributor to a very valuable skill of kinesiology professionals: the qualitative analysis of human movement. [ 2 ]

It is interesting to note that there are fewer biomechanical studies in this area rather than preventing and treating injuries. This is due to the fact that it takes longer time to carry out and report scientific research while coaches and athletes tend to improvise and try new techniques on their own. While technique is always applicable in human movement, in some sports the psychological and physiological aspects play a more important role in the performance and success of an athlete.[1] Reducing and treating injuries

Biomechanical research is an essential tool to prevent and treat injury. Biomechanical studies help to avoid injuries by providing information on mechanical properties during movement. This information is essential for tissue engineers in order to rebuilt the damaged or broken tissues in a way to adapt to the mechanical environment and ensure whether the engineered tissues are good enough to sustain the forces, stresses and strains of normal tissues.[3]

Engineers and occupational therapists use their knowledge of biomechanics to design and construct equipment while also setting up work schedules to help with rehabilitative exercises. Qualitative analysis of gait (walking) is also important for the therapist to analyze his patients while also being essential for the treatment of many locomotor system conditions. [1]

2.2 Mechanical Behaviour of Bone

2.2.1 Bone Structure

Bone tissue is a connective tissue whose solid architecture allows it to perform supportive and protective tasks. Similar to other connective tissues, it consists of a cellular component and an organic extracellular matrix of fibers [4]. The distinguishing aspect of bone is its elevated composition of inorganic constituents, in the form of mineral salts that amalgamate firmly with the organic matrix. The inorganic segment of bone assembles a compact and strong tissue, whilst the organic component provides malleability and resilience to the bone.[5] Compact Bone and Cancellous Bone

Compact or cortical bone contains many osteons or Haversian systems. Figure 2.1 shows that the osteon itself is made up of concentric series of layers of calcified matrix. At the boundaries of each layer, small gaps known as lacunae, contain one bone cell or osteocyte[6]. Various minute channels, called canaliculi, radiate in all directions from each lacuna connecting the lacunae to each other into the Haversian canal. From the osteocytes, cell processes extend into the canaliculi, allowing nutrients and oxygen to move from the blood vessels in the Haversian canal to extend to the bone cells.[5]

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Figure .1: Detailed bone structure [7]

Figure 2.2: Internal structure of bone [7]At macroscopic level, all bones constitute of two types of tissue which are: compact or cortical bone, and cancellous or trabecular bone. As shown in Figure 2.2, Compact bone sets up the outer shell of the bone and due to its dense configuration it has a similar structure to ivory. Cancellous bone is found within this shell and it consists of thin plates, or trabeculae meshed in a loose structure allowing room between the trabeculae for blood vessels and marrow. Cancellous bone tissue is also formed in layers therefore it is a lamellar bone, but it does not embody haversian canals. Nutrients are delivered to the osteocytes through tiny canalculi from blood vessels travelling through the red marrow. All bones are enclosed by a dense course membrane named periosteum. It coats nearly the whole surface area of the bone except for the joint areas, which are coated with articular cartilage. Its outer layer is diffused by blood vessels and nerve fibers that transpire into the protective layer via Volkmann’s canals. Meanwhile its inner layer is made up of an osteogenic layer that embraces bone cells responsible for developing new bone during growth and repair. Cancellous bone is always enclosed within cortical bone but the quantity of each type differs among bones due to functional prerequisites. [6]

The strength of all bones depends on the quantity of its mineral deposits and collagen fibers. Also diets and physical activity have a major effect on its strength. Loading of bones during physical activity, results in higher osteoblast activity. If, because of total immobilazation, bone is not exposed to any physical activity, the bone density, stiffness and mechanical strength will decrease. This phenomenon, where bones remodel according to the mechanical stress sustained in that surface of bone is summarized as Wolff’s law, which states that bone is laid down where needed and resorbed where not needed( Wolff, 1892).[5][1] Biomechanical properties of bone

As previously mentioned bone tissue is made up of an external layer (cortical bone) and the inner layer (cancellous bone). Biomechanically, this combination results in a composite material in which a strong, brittle material is enclosed in a weaker, more malleable one resulting in a material that is strong for its given weight.[5]

The mechanical properties contrast in the two bone types. Cortical bone is stiffer (will fracture when the strain exceeds 2%) while cancellous is less stiff and can withstand higher strain of about 75% in vitro. Since the cancellous bone has a porous structure, it is more capable to store energy rather than the cortical bone.

Three important variables that describe the mechanical properties of bone are the maximum load that the bone can withstand before it breaks (e.g. tensile, compressive, shear), maximum deformation for failure to occur and the energy that bone can store before it fails[7]. Furthermore the rate at which the bone is loaded impacts its biomechanical behaviour. Since bone is stiffer, it withstands a high load to failure ratio when loads are implemented at higher rates. Moreover bone has the capability to store more energy before failure at higher loading rates bounded by the condition that these rates remain within the physiologic range.[5]

The loading rate is important because it determines the fracture shape and the volume of soft tissue damage at fracture. When a bone cracks the energy stored is liberated. This implies that: at a low loading rate, the energy can spread throughout the whole creation of a single crack while the soft tissues and bone remains almost unharmed, while at a high loading rate the higher energy reserved cannot spread promptly enough through a single crack, thus results in damage to bone and soft tissues.

2.3 Mechanical Behaviour of Tendons and Ligaments

2.3.1 Structure of Tendons and Ligaments

The role of the tendons is to connect muscle to bone and to transfer tensile loads thus enabling joint motion. The function of the ligaments, which in turn attach bone to bone, is to guide joint motion and limit excessive mobility.

Tendons and ligaments are tough connective tissues with the greatest chemical composition being collagen and ground substance. The collagen fibers in the tendons differ from the ones found in ligaments since they aligned differently. The fibers that make up the tendons have a regular, parallel arrangement, which enables the tendons to deal with the high unidirectional tensile loads to which they are exposed during activity. The fibers within ligaments are not completely aligned in parallel thus can withstand small tensile loads in a variety of directions.