Dr. Siff,

	The work of Wohlfahrt et al (1993) looked at dynamic versus static
exercises of the abdominal muscles based on the statement by Fleck and
Schmidt (1981) that dynamic exercise does not necessarily result in
increased isometric skill. 

	Haggmark and Thorstensson (1979) identified no significant
difference in the ratio of muscle fibre types in the rectus or oblique
abdominal muscles but the transverse abdominis showed greater Type I fibres
and the Type II fibres were significantly smaller.This along with the
explanation of Norris (1993) shows the abdominals as having endurance and
rapid contraction capabilities. 

	What Wohlfahrt et al (1993) found was that the capacity of the
abdominals to perform dynamic functions does carry over to their stabilising
function but only when a high number of repetitions are performed at a slow
cadence (3 seconds per repetition). 
	
	This seems to suggest against the use of a timed sit-up test and aim
more towards the ability to perform high numbers of repetitions at a slow
pace as a good indicator of abdominal muscle endurance.

Mark Healy	
QMUC
Edinburgh
Scotland

Destiny is not a matter of chance, it is a matter of choice


-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, November 25, 1999 12:59 PM
To: [log in to unmask]
Subject: SITUP TESTING


Recently a student asked me the following offline question.  My response may

be of some interest here.  Any further comments are welcome.

<<What is you view, Dr Siff, on the use of timed  sit-ups as a measure of 
muscle endurance?  The definition of muscle endurance says: it is the
ability 
for the muscle to repeatedly exert itself till exhaustion.  Now with timed 
sit-ups, strong, but not really fit guys can do1 or 2 minutes  easily
without 
being exhausted at all. I don't even think that this limited time even
allows 
the muscles to exert themselves to exhaustion.>> 

***Several comments:

1.  Why do anyone wish to test abdominal endurance when these muscles serve 
the primary purpose of stabilisation, a quality which depends on strength, 
not endurance?  I have often spoken at conferences about this issue and 
rarely come across a single exercise scientist who has tested the 1RM (1 
repetition maximum) or even the 5RM of the abdominal muscles.

2.  Why test the abdominals and not a larger number of muscles?  Since the 
principle of specificity is involved in human function, testing the 
abdominals alone cannot be extrapolated to apply to overall muscle
endurance.

3.  Rapid execution of situps strongly and reflexively recruits the hip 
flexors and the abdominals, so that this test can hardly be regarded as a 
test of abdominal muscle endurance, especially since this test usually is 
done with the subject's feet restrained.  Rapidity of rebound can also 
involve the use of stored elastic energy and distort the picture of what 
exact process is involved in this so-called "endurance" activity.

4.  There are two major categories of muscle endurance, namely static and 
dynamic endurance.  The usual rapid test does not give any information of 
endurance under static or very slow (quasi-isometric) muscle action (which 
may be involved in stabilising the trunk in strength sports such as rugby, 
weightlifting, wrestling, gymnastics , judo, etc).

5.  Often the limitation to this sort of movement is local muscle ischaemia,

since the continuous strenuous activity tends to inhibit blood flow, so that

it may be difficult to distinguish between true local muscle endurance and 
the effects of local ischaemia or impaired blood flow.

6.  Another limitation is the fact that every subject has a different RPE 
(Rating of Perceived Effort) of any exercise, so that some folk can continue

an action for much longer than others because of mental, rather than
physical 
qualities.

7. The time element does not specifically test for endurance.  Instead it 
tends to estimate the mean power over a certain interval (work done per unit

time).

8.  Since all exercise involves an element of motor skill (and situp tests 
are no exception), it is important for all subjects to achieve comparable 
levels of skill if we are to compare performances of isolated muscles.

9.  Strength and endurance performance is often a function of bodymass 
(generally, the heavier one is, the lower one's relative strength), so are
we 
justified in comparing the unadjusted performances of subjects of different 
bodymass?

10.  The leverages involved in trunk flexion differ from person to person,
so 
that a person with a highly efficient lever system is intrinsically better 
equipped to produce strength and power than someone with a less advantageous

lever system.

So, in summary, I agree with any misgivings about using the traditional
timed 
situp test as a way of assessing human muscle endurance and wonder why its 
use has persisted for so long.

Dr Mel C Siff
Denver, USA
[log in to unmask]
(413) 832-9446 (FAX)



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