Balance and Torque

Define torque.

The rotary effect of a force about an axis of rotation, measured as the product of the force and the perpendicular distance

balance

a persons ability to control equilibrium

line of gravity

an imaginary line that extends from the center of gravity to the base of support.

base of support

area bound by the outermost regions of contact between a body and support surface or surfaces

equilibrium

balance between the applied force and internal forces for a body in motion

Center of gravity:

point around which the mass and weight of a body are balanced, no matter how the body is positioned

stability

resistance to disruption of equilibrium

What are the relationships among force, moment arm, and torque?

torque = force X moment arm An increase in force or moment arm will result in an increase in torque

What is the relationship among the line of gravity, base of support, and center of gravity?

BOS - as wide as possible CG - closer towards the side of BOS in which force will be acting upon LG - as short as possible

How can you control the length of the moment arm(s) for resistance in movement situations? For effort?

Bringing in your arm vs extending it out Throwing like a girl→ arm stays closer to the body because girls typically lack upper body strength More accurate because the moment arm is shorter, but less force is produced

Muscles that insert close to the joint are in a better _____ position.

SPEED AND RANGE

identify and define the components of a system of levers

-Lever: a simple machine that allows you to gain a mechanical advantage in moving or applying a force to an object -Effort force: the outside force applied that is required to move an object -Moment arm for effort: shortest (perpendicular) distance between a force's line of action and an axis of rotation. -Fulcrum: the point about which the lever rotates Resistance arm: distance between axis and the resistive force applied -Moment arm for resistance: shortest (perpendicular) distance between a resistance force and an axis of rotation. -Resistance force: the force at which the effort force must overcome to do work -Effort arm: distance between the fulcrum and the effort force

What is the optimum mechanical angle of pull for a muscle?

90 degrees because moment arm for the muscle will be as long as it will ever be and generate the greatest torque

Explain why it is much more difficult to balance on a non-moving bicycle at a stop light than it is to balance on a bicycle in motion.

A bicycle in motion (with rotating wheels) is more stable so it is harder to fall off of a moving bike. An object in rotational motion is more stable and the faster it spins, the more stable it becomes. Any object rotating around its own axis is more stable then when not rotating. Something moving fast is more stable than something moving slowly.

identify each class of lever, describe its advantages and disadvantages, and give examples of classes found in the human body

Class 1: A class 1 lever has the fulcrum placed between the effort and load. The movement of the load is in the opposite direction of the movement of the effort. Force and speed are inversely related to each other. Examples: Atlanto-occipital or head and the first vertebra.The weight (resistance) is the head, the pivot is the joint, and the muscular action (force) come from any of the posterior muscles attaching to the skull, such as the trapezius. Class 2: has the load between the effort and the fulcrum. (wheelbarrow) All second-class levers in the body work at a mechanical advantage because the muscle insertion is always farther from the fulcrum than the load. Second-class levers are levers of strength, but speed and range of motion are sacrificed for that strength. Example: is found in the lower leg when someone stands on tiptoes. The fulcrum is formed by the metatarsophalangeal joints, the resistance is the weight of the body, and the force is the gastrocnemius and soleus muscles pushing upward from calcaneus bone through the Achilles tendon. Class 3: has the effort between the load and the fulcrum; most common in the body; works well for speed; never has an advantage Example: forearm: the fulcrum is the elbow, the effort is applied by the biceps muscle, and the load is in the hand.

List the characteristics/factors that will decrease stability.

Decreased friction Smaller base of support COM in respect to BOS → closer to edge=less stable Smaller mass Height of mass→ higher COM=less stable Linear motion→ rotation is more stable

Muscles that insert further from the joint are in a better ____ position.

FORCE

What is the law of the levers?

FW1= FW2 Equal weights at equal distances are in equilibrium, and equal weights at unequal distances are not in equilibrium but incline towards the weight which is at the greater distance. If, when weights at certain distances are in equilibrium, something is added to one of the weights, they are not in equilibrium but incline towards that weight to which the addition was made.

What advantages/disadvantages are there to fully extending joints and/or implements in the performance of movement skills?

If joint is extended, object can be projected further, BUT need to be stronger and projectile is less accurately projected

What is the function of the bones, joints, and muscles in the body's leverage system?

In the human body, the joints are fulcrums Bones act as levers. Muscle contraction provides the effort that is applied at the muscle's insertion point on the bone. The load is the bone itself, along with overlying tissues and anything else you are trying to move with that lever.

How do structural modifications such as condyles, tuberosities, and sesamoid bones influence the ability of a muscle to produce torque?

Increase length, increase torque

What is meant by the term "advantage" when it is used in reference to simple machines? i.e. what is meant by saying you have a force advantage or a speed and range advantage?

It means that the output of the machine is greater than the input of the machine. Force advantage- can do more work than energy put in → work exceeds the amount of energy to produce the movement (we get more out of it) → creates a speed/range disadvantage A third class lever will never produce a force advantage Second class levers produce force advantage Speed/range advantage- more force needed, but longer range → creates an effort force disadvantage

List the characteristics/factors that will increase stability when receiving a force.

Large BOS CG is positioned closer to the oncoming force Height of CG should be lower

What is the relationship between the optimum positions for physiological and mechanical force production in muscles?

Length-tension relationship When it is slightly stretched because it produces the greatest amount of actual force Can't have optimal physiological and mechanical advantages at the same time

ow will lengthening and/or shortening resistance arms influence performance?

Lengthening arm= go further, be stronger Shortening arm = less force because less resistance force, doesn't go as far

List types of simple machines and give examples of those found in the human body

Lever Pulley: quads, psoas or quads and the knee moving upwards ` Wheel and axle: shoulder and hip internal rotation Incline place: slope squat Wedge: teeth bc one side is thick and one side is thin Screw:

What two factors determine the amount of torque a bone-muscle lever system can produce?

Moment arm Force