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Biomechanics of Resistance Training

KIN 265 - Berry College - Dept. of Kinesiology
by

David Elmer

on 16 September 2016

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Transcript of Biomechanics of Resistance Training

Biomechanics of Resistance Training
mechanics
"bio" = life
how all the parts of your anatomy work together so you can move
skeleton
muscles
axial skeleton
appendicular skeleton
skull
vertebral column
ribs
sternum
everything else
joints
all held together by
uniaxial
biaxial
multiaxial
- movement in one plane
- movement in two planes
- movement in all three planes
e.g. elbow
e.g. wrist
e.g. shoulder
vertebral column
7
12
5
fused -
5
planes?
toward the back
superior
inferior
posterior
toward the back
closer to the head
farther from the head
toward the front
medial
lateral
toward midline
away from midline
anterior
proximal
distal
closer to trunk
farther from trunk
directional terms
deep
superficial
sagittal
frontal
transverse
longitudinal axis
(through transverse plane)
mediolateral axis
(through sagittal plane)
(through frontal plane)
anteroposterior
axes
agonist
antagonist
"prime mover"
synergist
neutralizer
assists indirectly in a movement
eliminates unwanted movements
opposes movement
rigid structure
pivot point
(fulcrum)
forces
= lever!
can be arranged to:
increase force output
(at the expense of range of motion)
increase range of motion
(at the expense of force required)
types of levers:
1st class
2nd class
3rd class
force
axis
resistance
force
resistance
axis
resistance
force
axis
more force output, at the expense of needing to move farther
greater range of motion (speed), at the expense of requiring greater force input
more force output or greater range of motion, depending on the location of the axis
almost all of our joints are arranged as third class levers
muscles contract very forcefully over a short distance, produce large movements
Human Strength and Power
Force = mass x acceleration
Work = force x distance
Power = work / time
units:
force
: Newtons
distance
: meters
work
: joules (or Newton-meters)
power
: watts
(weight is a type of force)
(distance over which the force is overcome - usually vertical distance)
Work = torque x angular displacement
cross-sectional area
arrangement of fibers
joint angle/muscle length
biomechanical factors in strength
neural control
joint angle velocity
strength-to-mass ratio
types of
resistance
gravity
inertia
friction
fluid resistance (drag)
elasticity
negative work?
F = m x a
g
g
gravity only acts downward, so the moment arm of a weight is always horizontal
the difficulty of a lift may not be consistent across all parts of one repetition
especially important in regard to proper free-weight lifting technique
cam-based machines:
recruitment
rate coding
initial strength gains from resistance training are due to improved neural control
maximum force is related to cross-sectional area, but not necessarily total muscle volume
greater number of contractile units working in parallel
pennate muscles are capable of greater force
more contractile units fit in parallel in the same amount of space
muscle pennation angle is not fixed
if an athlete increases body mass by 15%, but force capability by 10%, then an athlete's ability to accelerate (power) is reduced
smaller athletes tend to be stronger pound-for-pound than larger athletes
strength is related to cross-sectional area (dimensions squared)
muscle mass is related to volume (dimensions cubed)
formula:
load lifted / body weight
2/3
tends to favor middle-weight athletes
may not be an actual bias
joint biomechanics concerns
back
shoulders
knees
always under a compressive force
increased force when lifting or carrying objects
back muscles operate at a mechanical disadvantage
low back is particularly susceptible to injury
when lifting, back should be flat or moderately arched, not rounded
breath-holding?
weight belts?
greatest range of motion
very unstable
lots of bones, muscles, ligaments, and tendons in the area that can rub against each other and cause damage
unintended rotation is prevented by ligaments and cartilage, which can be damaged relatively easily
patella (knee cap) is subjected to large forces during resistance training
wraps may not reduce injury, and may actually damage parts of the patella
but... they can increase performance by helping extend the knee
fiber type
type I
type IIA
type IIX
Full transcript