Power work and energy sport biomechanics

8/13/2019 Power work and energy sport biomechanics

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Matt Pain

Office UU1.07

E-mail: [email protected]

Power as an Indicator of Co-ordination


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Overview

Mechanical Energy Transfer Between Segments

Passive Energy Transfer

Power Balance into and out of a Segment

Internal Work Versus External Work Some examples


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Last week we looked at energy and power calculations.

Fenn's method fractional approach

Elftmann's method joint work/power

Mechanical power is not the whole story but it can

provide lots of useful information.

Gross movement of the body occurs about the joints.


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The majority of work done by or on the body is done on or

by muscles moving limbs about joints.

Calculating the joint power histories will give an indicator

of the joint co-ordination.

Diagram 5.6 Winter 1990


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For a single joint with a single extensor and flexor the

joint power allows us to find the muscle power.

Humans do not have multiple joints and multiple muscles

for extensors and flexors about these joints.


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Two problems:

Muscle indeterminacy - more muscles across a joint than

number of joints. This is will be covered in more detail

next lecture.

Energy transfer between segments - segments that touch

will exert forces on each other, if there is motion this

means energy transfer.


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In its simplest form this can be considered a passive effect.

e.g. flipping book pages

rapidly move your forearm with your wrist

relaxed.


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Passive Energy Transfer

Fii

Fj

Vj

Vi

j

Energy going into segment i

Energy going out of segment j

This is in addition to active muscle forces acting across a joint.


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Power Balance into and out of a Segment

Change in energy of a segment which is made up of:

Passive power flow distal end Muscle power flow distal end

Passive power flow proximal end

Muscle power flow proximal end


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Sporting Examples

Javelin

(Menzel, 1986)

Baseball pitching

(Stodden et al., 2001)

High front kick(Sorensen et al., 1996)


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Internal Work Versus External Work

These calculations are from external measurements and

so do not give the full picture.

We are commonly interested in the work we can do on anoutside body, thrown implement, lifting weights, jumping.

But we need to do work just to make us move.


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Hidden pow eris that which is being produced but cannot

be measured by these techniques.

To find out the actual work being done by a group of

muscles hidden power needs to be included.


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The names you give to define these is not the important

point.

Knowing that external measurements of work have to be

interpreted in light of different energy usage is.


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Some examples of hidden work:


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Examples in different sports

Consider some sports with different goals.

What are the following events trying to maximise or

minimise?

If we analyse the mechanical energy and power involved

how much help could we give the athlete?


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Ultra long distance runner


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Weightlifter


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Discus thrower


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Baseball pitcher


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Wrestler


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Synopsis

However in most sports smooth precise movements are

required to make best use of the different energy transfer

systems.

Good technique is often subjectively thought of as being

smooth or graceful and usually arises through efficient

use of energy.

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Power work and energy sport biomechanics

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