Biomech terms + def

Name one goal of a biomechanical analysis?

Understand the kinematics/kinetics of a movement to prevent injury (alternative answer is improve performance)

What’s the diff between qualitative and quantitative analysis

qualitative=non numerical description of variables of interest (think comparison)
quantitative=those same claims but backed by numbers

How do you determine time = 0

With a relevant, repeatable, and reliable event that occurs at the start of every trial to kick off your phase of interest

Give 2 examples of temporal analysis

cadence, duration of contact, duration of flight phase

What’s meant by the term event? Does an event happen in one frame? Give 3 examples

An event is a frame at which something happens in a movement, and it is always a single frame. For example could be toe off moment, minimum TBCM position, max GRF

What are the benefits of skilled subjects in ts analysis?

The movements are practiced so theyre more reliable and consistent, which matters when you’re comparing data between trials.

When setting up a camera what are 3 things you should do prior to data collection to maximize quality of video?

Make camera perpendicular to plane of motion
Make camera level at TBCM position
Take calibration frame
Fit whole subject into frame for entire movement as large as possible
Set shutter speed as fast as possible to avoid blur

What’s a calibration frame?

An image you take with the video camera of an object of known length to convert px to meters

What’s kinematics? What are some variables used for kinematic analysis?

The study of THE EFFECT OF FORCES acting on a system. We could use position, velocity, and acceleration. Useful to describe the geometry of motion (cause/effect from force)

What’s kinetics? Give 3 examples of variables

Study of THE ACTUAL FORCES acting on a system. Variables describe cause of motion and include force, power, impulse, and torque

In musculoskeletal modeling, what assumptions do we make about body segments?

We assume that segments are rigid and the BSP’s actually describe a subject

What’s the center of mass of a segment? How’s it determined?

The balance point of a segment, the point @ which mass of segment is evenly distributed. It’s calculated by finding location of endpoints and using the % distance from proximal end.

What’s TBCM? How’s it determined?

Theoretical point around which mass of whole body is distributed equally, the weighted average of segment centers of mass.

Why could a VJ movemenet have a TBCM different at takeoff vs landing>

Segment configuration (position) is different.

What’re body segment parameters?

Geometric characteristics of segments, there are 4; endpoints, center mass points, mass %, and something else I forgot.
Pros: Allows us to calc TBCM which lets us represent whole body motion
Cons: Theyre avgs and include the BSp assumption that segments are rigid, thus causing error

Are hip, knee, and ankle relative or absolute angles?

Relative

Are shank, thigh, and trunk angles absolute or relative?

absolute.

On an angle-angle graph how is time represented?

Distance between points

Explain the first central difference method

It’s a method to calculate velocity from position data or acceleration from

velocity data. You used every other data point because the calculated

velocity/acceleration can then be assigned to the time step in between

What’s the relationship between position, velocity, and acceleration?

Velocity is change in position divided by change in time. Acceleration is change

in velocity divided by change in time.

What’s the mathematical relationship b/w position, velocity and acceleration?

Velocity is the slope of the position vs. time curve; acceleration is the slope of

the velocity vs. time curve

When analyzing a d vs t graph, when is the pos increasing? when’s it staying the same? When’s the pos decreasing? when’s velocity 0m/s? when’s the velocity positive? when’s it negative?

Position increasing: when the slope is positive (curve is going up)

Position same: when the slope is 0 (curve is horizontal)

Velocity = 0: when curve is flat

Velocity > 0: when slope is positive

Velocity < 0: when slope is negative

When analyzing a v vs t curve when’s the pos increasing? When is position staying the same? when’s it decreasing? when is velocity 0m/s? when’s velocity positive? when’s it negative? When’s acceleration positive? when’s it negative? when’s acceleration 0m/s?

Position increasing: when curve is above 0

Position constant: when curve is at 0

Position decreasing: when curve is below 0

Velocity = 0: when curve is at 0

Velocity > 0: when curve is above axis

Velocity < 0: when curve is below axis

Acceleration > 0: when slope is positive (curve is going up)

Acceleration < 0: when slope is negative (curve is going down)

Acceleration = 0: when slope is 0 (curve is horizontal)

When analyzing an a vs t curve, when’s velocity increasing? when’s velocity decreasing? can you tell if velocity is positive or negative?

Velocity increasing: curve is above axis

Velocity decreasing: acceleration curve is below axis

No, can’t tell if velocity is positive or negative

Describe an example when:
An object velocity is + and acceleration is +
An object velocity is + and acceleration is -
An object velocity is - and acceleration is +
An object velocity is - and acceleration is -

At the exact moment when an object changes direction, what will you see on a vertical position vs time curve? what will you see on a vertical velocity vs time curve?

Vertical position vs. time curve will have a peak; Vertical velocity will cross 0

(going from positive to negative)