Biomechanics Animal Movement

Learning Objective Explain the biomechanics of animal movement

Vocabulary Biomechanics Locomotion Kinesiology Anatomy Flexion Extension Adduction Abduction Myofibril Myosin Actin Fascicle Sarcomere Synarthrosis Amphiarthrosis

Biomechanics

Kinesiology Kinesiology is the study of human movement. Biomechanics is one of the many academic sub disciplines of kinesiology.

What is Biomechanics? Biomechanics - the study of the movement of living things using the science of mechanics Biomechanics in kinesiology involves the precise description of human movement and the study of the causes of human movement.

Branches of Biomechanics The major branches of mechanics used in most biomechanical studies. Fluid mechanics - mechanics of fluids Rigid body mechanics – solid bodies Static – objects at rest Dynamics – moving objects Kinematics Kinetics

Anatomy and Biomechanics Anatomy - the study of the structure of the human body. The study of biomechanics requires an understanding of the structure of musculoskeletal systems and their mechanical properties Anatomy provides essential labels for musculoskeletal structures and joint motions relevant to human movement.

Muscles & Bone Movement

Ligaments Attaches bone to bone

Tendons Attach muscles to bones

Cartilage Cartilage Is a type of connective tissue that bends easily Most of the skeleton of an embryo is cartilage In adults, it only remains in the joints, the ears, the nose and at the end of the ribs Cushions the joints

Bones

Bones Organs composed of moist, living tissues Pink=fibrous connective, forms new bone after fractures Blue=cartilage, forms cushion-like surface for joints Inside are osteocytes that secrete bone matrix Yellow bone marrow is stored fat from blood to bone Red bone marrow produces RBC’s

The Appendicular Skeleton Pectoral girdle: Arm bones Wrist and hand bones Scapula (shoulder blades) Clavicles (collar bones) Pelvic girdle: Pelvis Leg bones Ankle and foot bones

The Axial Skeleton Made up of Cranium (skull) Vertebral column (backbone) Sternum (breast bone) Rib cage

Joints The place where bones meet is called a joint Synarthrosis - immovable (i.e.. the skull) Amphiarthrosis - moveable

Joints Moveable joints: Hinge = elbow and knee Ball-and-Socket = shoulder and hip Pivot = base of the skull Gliding joint = wrists

Muscles

Muscle Structure Review

Dissecting Muscles Muscles consist of bundles of muscle fibers (cells), oriented parallel to each other Cells are bundles of myofibrils, which are composed of the contractile proteins actin (thin) and myosin (thick) Proteins form a striped banding pattern that characterizes skeletal muscles Contractile unit of skeletal muscle is the sarcomere

Contracting Filament Model Sarcomere contracts when thin filaments slide over thick Sarcomere shortens, but length of filaments don’t change Heads of myosin (thick) filaments bind ATP so they can bind to actin (thin) filaments Head produces power stroke which moves the actin toward the center of the sarcomere when ADP is released

Muscle Fiber Types Slow fibers better designed for endurance Activities Fast fiber - Weight lifting Each muscle has a mix of the above types

Motion in Vertebrates Motion and locomotion are produced by muscles pulling on bones. Joints in the skeleton allow for parts of the body to flex and extend, allowing for motion. Ligaments attach bones to bones at the joints. Muscles attach to bones by tendons. Origin is on a bone that remains stationary. Insertion is on a bone that moves.

Creating Movement Muscle action shortens or contracts muscles The agonist moves the muscle while the antagonist reverses the movement Antagonistic pairs of muscles are found in all animals

Joint Motions Anatomy also has specific terminology de- scribing the major rotations of bones at joints. “Flexion” refers to a decrease in joint angle in the sagittal plane, while “extension” is motion increasing joint angle. (a) Flexion and extension movements occur in a sagittal plane about a mediolateral axis (b) adduction/abduction of the hip joint occurs in a frontal plane about an anteroposterior axis

Movement Flexion - decreases angle of a joint. Extension - increases angle of a joint. Abduction - movement away from midline. Adduction - movement toward midline. Rotation - turning around an axis.

Lever Systems Muscles and bones work together around joints as systems of levers. Lever systems of muscles and skeletons can be designed either for power or speed. The ratio of load arm (resistance) to power arm (effort) determines the power. A low load arm to power arm ratio provides high power but low speed A high load arm to power arm ratio provides high speed but lower power. Power L:P = 2 Speed L:P = 5

Bipedalism

Bipedalism Upright walking in humans requires a fluid alternation between stance phase and swing phase activity for each leg. Key features are the push-off, using the great toe at the beginning of the swing phase, and the heel-strike, at the beginning of the stance phase.

Arm swinging Erect (bipedal)

resulted in a number of postcranial changes in the legs and feet . . . Bipedal walking resulted in a number of postcranial changes in the legs and feet . . .

Legs Leg bones are much stouter in most primates and have more pronounced dorsal ridges

Comparison of muscles that act to extend the hip. Understanding Physical Anthropology and Archaeology, 8th ed., p. 224

Hinge joint A hinge joint allows flexing and extending along one plane. Pairs of muscles work opposite one another to create motion.

Ball and socket joint A ball and socket arrangement allows rotational movement. Multiple pairs of muscles allow movement in a range of directions.

Advantages for Locomotion It is easier to get food It its easier to find shelter An organism can move away from dangerous conditions or predators It is easier to find mates and reproduce

Why Bipedalism?

Acheulian biface (“hand axe”) Understanding Physical Anthropology and Archaeology, 9th ed., p. 239

Locomotion in Vertebrates

Types of Locomotion Swimming Locomotion on land Gravity not a problem, but friction is Water supports weight, but is dense and presents resistance Legs as oars, jet-propelled, and undulating side to side or up and down Streamlined body shapes aids increased speed Locomotion on land Need to be able to support self and overcome gravity Air presents little resistance, but also little support Energy expenditure to propel forward and keep from falling down Muscles and skeleton more important that streamline shape

Types of Locomotion (cont.) Hopping Tendons in legs store energy when landing, like a spring for the next jump Cost free energy boost Rest with tail and hind feet on ground Costs little energy to maintain Walking and running Overcome friction between foot and ground Walking: 4 legged – 3 on ground all times; 2 legged – part of 1 at all times Running: 4 legged – 2 -3 feet move at once if not all Momentum stabilizes body position

Types of Locomotion (cont.) Crawling Friction adds considerable resistance because of increased contact Undulate body side to side, inch forward, or peristalsis Flying Wings developed to completely overcome gravity Shape must alter air current to create lift Air pressure underneath is greater All based on mircotubule or microfilament systems. Animals in motion Leading edge thicker, lagging edge thinner; top convex, bottom concave or flat