Studied by 50 peoplebiomechanics
study of mechanics as it relates to the functional and anatomical analysis of biological systems and especially humans
mechanics
the study of physical actions of forces; further divided into: statics and dynamics
statics
the study of systems that are in a constant state of motion, whether at rest with no motion or moving at a constant velocity without acceleration; all the forces acting on the body are at a steady state resulting in the body being at equilibrium
dynamics
the study of systems in motion with acceleration; the system is unbalanced due to the acceleration and unequal forces acting on the body
mechanical advantage
used to move one point of an object a relatively small distance to result in a relatively large amount of movement of another point of the same object; essentially using a relatively small force to move a much greater resistance; MA=load/effort
kinematics
the study of spatial and timing characteristics of motion of the human body and its segments
the variables of motion
time, displacement, velocity, and acceleration; these will describe both linear and angular motion
time
temporal characteristics of a performance, either of the total skill or its phases
displacement
length and direction of the path an athlete takes from start to finish
angular displacement
direction of, and smallest angular change between, the rotating body’s initial and final position
velocity
displacement per unit of time
angular velocity
angular displacement per unit of time
acceleration
rate of change of velocity
angular acceleration
angular velocity per unit of time
kinetics
focuses on the various forces that produce a movement and the resulting motion
internal forces
generated by muscles pulling via their tendons on bones, and bone-to-bond forces exerted across joint surfaces; cause individual body segment movements
external forces
acting from outside (such as the force of gravity or the force from any body contact with the ground) environment, sport equipment, or opponent; affect body movements
how can the musculoskeletal system be thought of?
a series of simple machines used to increase mechanical advantage
four functions of machines
balance multiple forces
enhance force in an attempt to reduce total force needed to overcome a resistance
enhance ROM and speed of movement so that resistance may be moved further or faster than applied force
alter resulting direction of the applied force
three types of machines producing movement in the body
levers (most common), wheel-axels, pulleys
three types of machines not found in the body
inclined plane, screw, wedge
levers cannot be changed only utilized more effectively (t/f)
true, cannot
lever
a rigid bar that turns about an axis of rotation or a fulcrum
axis (fulcrum)
point of rotation which lever moves
what do bones represent?
levers
what do joints represent?
axes (fulcrum)
what do muscles represent?
force
resistance
can vary from maximal to minimal (may be only the bones or weight of body segment)
point of force application (f)
usually muscle insertion representing the point of effort
point of resistance application (r)
center of mass of lever or location of an external resistance
1st class lever
axis (A) somewhere between force (F) & resistance (R); (far)
2nd class lever
resistance (R) somewhere between axis (A) & force (F); (arf)
3rd class lever
force (F) somewhere between axis (A) & resistance (R); (afr)
mechanical advantage determined mathematically
mechanical advantage = length of force arm/length of resistance arm
single pulleys
function to change effective direction of force applied (mechanical advantage = 1)
compound pulleys
combined pulleys in order to increase mechanical advantage; each addition will increase the mechanical advantage by 1
moment arm
the shortest perpendicular distance from the axis of rotation to the line of action of the force
moment of force
influenced by the magnitude of both the moment arm and the magnitude of force (moment arm x force)
torque
the turning effect of an off center force (moment arm x force)
the ----- the distance of the force arm, the ---- torque produced by the force
greater; more
resistance arm
the distance between the axis and the point of resistance application
if either of the resistance components increase, there must be an \n increase in one or both of force components (t/f)
true, increase
greater resistance or resistance arm requires lesser force or longer moment arm (t/f)
false, greater
greater force or moment arm allows a greater amount of resistance to be moved or a shorter resistance arm to be used.
false, longer
the longer the lever, the less effective it is in imparting velocity
false, more
what type of force do longer levers produce?
linear force
what type of lever should we have for quicker movements?
short lever arm
what does maximal ability of a muscle to develop tension & exert force depend on?
length of muscle
what percentage should a muscle be stretched to to produce the greatest amount of tension?
100%-130%
what percentage will a muscle stretch and lose its ability to exert as much force?
130%+
what percentage will a shorten muscle and no longer be able to produce contractile tension?
50%-60%
balance
process whereby the body’s state of equilibrium is controlled for a given purpose
how does the body become balanced?
the base of support and location of the COM is manipulated; if the line of gravity passes through some part of the body’s base of support (BoS)
stability
a measure of the difficulty with which equilibrium can be disturbed
how to increase static equilibrium
increase BoS
increase inertia of the body (increase the mass)
decrease the vertical distance between the COM and the BoS (lower COM)
increase the distance between the point where a vertical line from the COM intersects the BoS
what happens if an athlete has forward momentum and a pivot point is created?
some or all of the linear motion can be transferred into angular motion
Note
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