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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) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%