MYTH 2 - Lecture 5 - Mechanics of Movement
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Draw a simple muscle structure; label and define
need to include connective tissue (endomysium, perimysium, epimysium) [provide protection from mechanical trauma]; muscle fibre [linked to tendon]
what is the relationship between the number of cross-bridge attachments to actin?
the greater number of CB attachments to actin, the greater the force generated. force is dependant on the amount of cross bridges that are formed and attach to the actin. the brain sends signals so the thick myosin physically connects with the actin. NOTE: if majority of the sarcomeres shorten, then muscle will shorten
What two factors are needed to continuously generate muscle tension?
• ATP 2. Nervous input (motor command) from the brain to carry out movement
Draw the length-tension relationship
check pic on phone and pg 3 slide 2 31/7/18 handout
explain the type of contraction and force velocity relationship
Iso-tonic CONTRACTION - equal tension, muscle length changes Iso-tonic CONCENTRIC - muscle length decreases, muscle force > load e.g. muscle shortening; bicep curl, pull up, running uphill Iso-tonic ECCENTRIC - muscle increases, muscle force < load e.g. muscle lengthening; running downhill, push ups Iso-metric contraction - muscle length is constant, muscle force = load e.g. pushing against a wall, yoga, rock climbing
What can be done to decrease lower back stress
• Lighten the load • Bring the object closer to your body • Bend the knees
What do levers do?
they amplify the input force to provide a greater output force which is known as leverage and most skeletal muscles act using the principle of leverage
what does a lever consist of?
• an axis of rotation [called the fulcrum or pivot] • a resistive force or load • an effort force [the applied force used to move the load]
describe 1st class levers
• effort force and load force are applied to opposite sides of the axis of rotation • effort force and load force act in the same direction
describe 2nd class levers
• effort and load force are applied on the same side of the axis of rotation • effort applied farther from axis than the load effort and load force act in opposite directions • good for strength; poor for moving load quickly or through the large range of motion
describe 3rd class levers
• effort force and load are applied on the same side of axis of rotation • effort force applied closer to the axis than the load effort load and force act in opposite directions • good for moving load quickly or through large range of motion; poor for strength