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Corey Scholes
08-07-2005, 04:00 PM
Thank you to those that responded to my question (original
included below).

Here is a follow-on to the discussion:

After discussing work-rest ratios with Peter Le Rossignol
(see response below), a 1 min rest interval would be
adequate to 'reset' the ATP energy system, considering the
duration of a step down task is less than a second. Whether
repeated landings would induce fatigue is another
neuromuscular mechanism is still possible I think. This
highlights the problem of most fatigue measures, in that
they tend to track only one mechanism of the neuromuscular
system and are sometimes not task-specific.

In regards to Axel's response, it is important that I have
some kind of feedback system for this study and for future
studies that will include a fatiguing protocol, so that I
can attempt to standardise the level of fatigue across
participants before asking them to performa a step-down
trial.

The only way I can think of to satisfy these requirements is
to have a functional measure rather than a physiological
measure that may reflect the level of fatigue on the sum of
the parts rather than just one process. This may involve
using an incline leg press to simulate a step landing and
measuring the displacement of the limb as a person attempts
to 'catch' the weight.

I wonder if anyone else has come to similar conclusions or
disagrees???

Any input would be greatly appreciated

Corey

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Hello everyone,
>
>I am designing a study to examine the effects of practice
>and task parameters on knee load patterns during step
>landings.
>
>It is important that muscular fatigue is controlled for
>during the experiment protocol and I was wondering if
anyone
>may be able to guide me towards an appropriate rest
interval
>between step landing trials to prevent fatigue accumulation.
>
>I am also very interested in any functional, task specific
>measures of muscular fatigue that anyone has come across
>that would apply to a step-landing movement (essentially
>simultaneous eccentric contractions of the knee & hip
>extensors and ankle plantarflexors)
>
>Any feedback on this issue would be greatly appreciated,
>thanks.
>
>Corey Scholes
>School of Human Movement Studies
>Queensland University of Technology


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Corey,
For your question dealing with work to rest ratios and
repeated dynamic
activities, Wadley & Le Rossignol suggest a 1:3 work:rest
ratio. Full
reference is:

Wadley G, Le Rossignol P. The relationship between repeated
sprint
ability and the aerobic and anaerobic energy systems. J Sci
Med Sport
1998; 1(2):100-110.

If you would like to be more conservative, a 1:6 work:rest
ratio has
been suggested to be the most appropriate to prevent
muscular fatigue
when using electrical stimulation to elicit contraction
(Packman-Braun,
1988).

Also, Madigan & Pidcoe used EMG median frequency in
conjunction with a
subjective assessment of perceived effort to quantify
fatigue in
subjects performing repeated landing tasks. Full reference
is:

Madigan M, Pidcoe P. Changes in landing biomechanics during
a fatiguing
landing activity. J Electromyogr Kinesiol. 2003; 13:491-498.

Good luck,
Cale

Cale Jacobs, PhD, ATC
Orthopedic Research
Lexington Clinic
700 Bob-O-Link Dr
Lexington, KY 40504
(859) 258-8560
cjaco@lexclin.com
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Hi Corey,

it might be of interest whether you really need fatigue
information
synchronously to your exercise in order to use it as a
feedback system
or whether you want to check for fatigue effects in your
parameters
afterwards.
As fatigue is a continous process starting already with the
start of the
exercise rather than a failure point phenomenon you might
want to
control fatigue onsets evident in your data. This will
depend on the
data you are collecting (whether you take force data or
lactat measures
or EMG signals)
What is your setup and which parameters do you intend to
take?
Yours

Axel

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