L22 - relative phases

Question 1

How is DRP typically summarised across multiple cycles?

Answer 1

Using the mean and standard deviation to describe variability and coordination consistency.

Question 2

What is discrete relative phase (DRP) used for?

Answer 2

To measure the relative timing between two key events or joints in a movement cycle.

Question 3

What is the formula for calculating discrete relative phase (DRP)?

Answer 3

drp = ((t2-t1)/T) x 360 degrees
Where:
t1, t2 = time points of interest
T = duration of the cycle

Question 4

What is a phase angle in biomechanics?

Answer 4

An angle representing a point in a phase plane, defined by joint angular displacement and velocity.

Question 5

How do you calculate a phase angle (ϕ)?

Answer 5

ϕ=tan ^−1
( angulardisplacement /
angularvelocity)

Question 6

Why do we normalise displacement and velocity in centred phase planes?

Answer 6

To centre the origin

Scale both variables from −1 to +1

Enables consistent 0–360° phase angle calculations

Question 7

What is the formula to normalise a variable for centred phase angle analysis?

Answer 7

= 2 ((x(t) - min(x)) / (max(x) - min (x))) - 1
Where 𝑥 is the signal (e.g., angle or velocity) and t is the time/frame index.
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Question 8

What does a positive relative phase mean?

Answer 8

The proximal segment is ahead of the distal segment in phase space.

Question 9

What does a negative relative phase mean?

Answer 9

The distal segment is ahead of the proximal segment in phase space.

Question 10

What is continuous relative phase (CRP)?

Answer 10

A measure of joint coordination across every time frame in a movement cycle.