PDA

View Full Version : EXERCISE MACHINE CURVES



Mel Siff
09-29-1998, 09:58 AM
In a message dated 9/29/98 , JRTELLE@aol.com wrote:

>My dynamic strength curve findings ALL indicate that strength curves/profiles
>change ever rep! ---bottom line single profile cams cant and never will
provide
resistance matching the athletes changing force expressions!! (unless your
doing just one rep and even at that the speed as a function of the loading
pattern manifests different curves----with ~ the same area underneath same!!

BIOMECHANICAL ASSESSMENT

This generally is true of all biomechanical measurements in sport, including
force plate, high speed video and EMG methods, but is does not imply that the
information from single recordings is useless or misleading. This is why time
averaged series of recordings and spectral analytical techniques are also
used, as is fairly routine in electroencephalography and electromyography.
Superficial EMGs are notoriously difficult to record with consistent accuracy
and reproducibility or to interpret without vast experience in the field, so
one cannot rely on these as the sole analytical method for assessing the
efficacy of a specific training modality.

'Eyeballing' of EMG printouts can often misinterpret or miss trends which
emerge from deeper computer analysis, so this is undoubtedly why Prof
Cardinale is using a more complex battery of tests in his analysis of exercise
machines.

MATCHING OF TORQUE CURVES

One of the points often made against exercise machines which are designed to
accommodate to the variation in torque with joint angle is that the cam or
lever system does not adequately 'match' the unloaded or 'isotonically' loaded
joint. The counter argument usually remarks that, with free weights, the
individual can at least accelerate or decelerate the external load to
compensate for changes in joint torque characteristics (sometimes called
'Compensatory Acceleration').

However, this 'compensatory acceleration' method can also be applied during
exercise on any non-isokinetic, centrifugal clutch or feedback-controlled
exercise machine, so arguments about matching of individual 'strength curves'
to 'machine curves' of cam and lever based machines are not that simple.

Dr Mel C Siff
Littleton, Colorado, USA
mcsiff@aol.com

-------------------------------------------------------------------
To unsubscribe send UNSUBSCRIBE BIOMCH-L to LISTSERV@nic.surfnet.nl
For information and archives: http://www.bme.ccf.org/isb/biomch-l
-------------------------------------------------------------------