Audience: Anyone who
goes to the gym
By Jose M Batista
What is it?
Levers consist of
• Fulcrum (Axis, joints)
• Force (muscle pulling from tendon
• Lever ( Long bone)
• Resistance
Advantage in Force
Production
• Less force is needed
• Disadvantage in speed and ROM
• Not as Far
Advantage in
motion and speed
•
Further and faster
•
Disadvantage in force
•
Harder to lift
•
Human movement
Calculations
Torque (moment)=force x
moment arm
With this equation we can
calculate how much force do we
need to move objects around.
Breaking it Down
There are three types of levers
•
First Class Levers
•
Second Class Levers
•
Third Class Levers
First Class Levers
•
Axis is in the middle
•
Examples are see-saw and cutters
•
Advantage in force production
•
In the body (cervical extension)
Example First Class Levers
Second Class Levers
•
Force arm is longer than the resistance arm
•
Examples are wheelbarrow and nut cracker
•
In the body (plantar flexion)
Example Second Class Levers
Third Class Lever
•
Resistance arm is always longer than force arm
•
These are most used in the body
Example Third Class Levers
Length of Lever and Effect
Body must create torque while objects create an opposite
torque
Weight of ball creates torque
Resistance*moment or resistance arm
Weight of ball*distance ball is from axis
Practical Questions
When lifting weights is it more advantages to have longer arms
and legs or would it be a disadvantage and why?
Longer arms means the resistance arm is going to create more
force/torque.
Would you expect 100 meter sprinters to be taller or shorter
and why?
Its advantageous for a longer stride but it’s a disadvantage as
well because you need more force to move that leg.
Why do you think kids going through puberty seem to run
awkwardly?
Their resistance arms are growing and its difficult for them to
move each limb.
Objects of Different Lengths
Objects held in longer limbs travel a greater distance in a
given time period and so can move with higher velocities
and speeds.
Tennis players can hit a tennis ball with more speed with a
straight-arm drive than with a bent elbow because the
lever is longer.
Examples
• Baseball pitchers, golf, football punter, etc.
• Kids leg lengths in running.
• Running speed (cycling rate)
While they will need more force to move limb, they have a
“mechanical advantage in speed and ROM”.
Practical Questions
What affect does choking up on the bat do and how does
it affect hitting the ball? Talk about mechanics and why?
Moving the axis will either make the lever longer or
shorter letting you hit the ball further.
Can a skilled lacrosse player shoot a ball faster with a
defensive pole(72in.) or an attackers pole(42in.)?
An attackers pole is easier to hit the ball because its
moment arm is shorter.
What affect does hitting a tennis serve have when you hit
the ball at its highest point vs. at a lower point?
When you hit the ball at its highest point it would be
easier to cover more ground.
How is it used in general?
• We use levers for everything
• Our muscles and bones act together to
form a lever
• We use levers to move things more
efficiently
• Levers can be used to increase movement
Why is it important?
• Strength advantage
• Movement advantage
• But not both
• Able to pick up things
• Move efficiently
• Obtain better ROM
Recap
Careers using Lever Systems
• Clinicians
• Physical Education Teachers
• Curriculum Developers
• Athletic Trainers
• Exercise Physiologists
• Sport Psychologists Careers