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BBS1004 Brain, behavior and movement summary of all lectures
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A summary of the lectures in course BBS1004 - Brain, behavior and movement of the bachelor biomedical sciences at maastricht university.
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1. Basic biomechanicsUnits
Base units
kg (mass)
m (length)
s (time)
A (electric current)
Derived units
N (force or weight; kg.m.s-2)
J (energy or work; N.m or kg.m2.s-2)
W (power; J/s or kg.m2.s-3)
Hz (frequency; s-1)
Radian (angle; - or m.m-1) NB 1 rad=57.3o
V (voltage; kg.m2.s-3.A-1)
Translation
Position, velocity and acceleration vector
Origin x=0 , y=0
Direction (angle) and magnitude (a, √(x2+y2))
We assume only 2 dimensions, even though we know that there are 3.
SOS-CAS-TOA (SOH-CAH-TOA) is used to determine side or angle of triangle
Sine = Opposite ÷ Hypotenuse (=schuine)
Cosine = Adjacent ÷ Hypotenuse(=schuine)
Tangent = Opposite ÷ Adjacent
Fy = Fperpendicular sin (a)
Velocity = Δ position / time
Speeds is only a number speed ≠ velocity speed = |velocity|
Acceleration = Δvelocity / Δtime
Newton's Laws
2nd: ΣF=m.a F=m.a
3rd: Faction= -Freaction
* e.g. 100m sprint : velocity is low at the end, acceleration is low at the end as well deceleration
,Rotation
– Angle, angular velocity, angular acceleration
– Torque (Moment) most important in joint movement
Joint angle dependent on convention
Angular velocity = Δjoint angle / Δtime joint angle / Δjoint angle / Δtime time
Angular acceleration = Δjoint angle / Δtime angular velocity / Δjoint angle / Δtime time
Torque (=Moment)
e.g. force on the door
Force times distance to the axis
M = Fm x d [N.m]
Moment arm (=lever arm)
Sign :
– counterclockwise is positive (elbow flexion)
– clockwise is negative (elbow extension)
Axis of rotation
In 3D there are 3 axes of rotation 3 torques
Flexion, extension and hyperextension
Abduction and adduction
External rotation and internal rotation
body movement are caused by joint rotation
E.g. Hand movement by shoulder, elbow, and wrist rotation
Static torque does not produce an angular acceleration
Dynamic torque does produce an angular acceleration
Angle of peak torque = the joint angle where we are the strongest.
Energy
, Etotal = Ep + Ek
Potential energy : Ep = m.g.h height
Kinetic energy : Ek = ½.m.v2 velocity
Elastic energy
Ek is highest when the amplitude is zero in equilibrium position
Ep is highest when the amplitude is maximal
Work, “muscle force times change in length”
W=∫Fds ≈ FxΔjoint angle / Δtime s=F.s.cos(α))
Work = force x displacement
Positive work: direction of movement is same as the direction of exerted force (isotonic concentric)
Positive work results in an increase in kinetic or potential energy or both.
Negative work: direction of movement is in opposite direction of exerted force (isotonic eccentric)
Muscle can be used as motor AND as brake
Motor
Performing (positive) work increases the energy in the system (body)
e.g. increase in velocity (kinetic energy) or height (potential energy)
Brake
Performing negative work decreases the energy in the system (body)
e.g. decrease in velocity (kinetic energy) or height (potential energy)
Power
Power equals work per unit time P = W / Δjoint angle / Δtime t
• Muscle length sinusoidally variated
• Muscle activated electrically
• Muscle force is measured
• Red is work between start and max force
• Green + blue area = work generated during shortening
• Blue area = work dissipated during lengthening
negative
• Green area = net work generated
Muscle work equals Muscle force times Muscle change in length
(work loop) = work done
Translation (muscle) and rotation (joint) Mechanical work in muscles during contraction.
, Isometric contraction
No net length change of muscle
Velocity is zero
Concentric contraction
Bicep muscle shortens, elbow flexes
Positive velocity / power
Eccentric conctraction
Biceps muscle lengthens, elbow extends
Negative velocity / power
Isometric contraction: no mechanical work, muscle length remains unchanged.
Isokinetic: muscle length remains unchanged, produce movements with constant speed
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