Despite these minimizing features, we're still faced with an exercise that puts the average participant at an increased level of risk for comparatively little benefit.
My specific objecions:
|Low back risk||the exercise carries a high risk of back injury. Most individuals don't have the strength to do them properly.|
|Hip flexor work||the average group exercise participant doesn't need their hip flexors any stronger. Too many of them have postural problems already from too much hip flexor work (lordosis).|
|Maximal effort||encouraging them to do as many sit-ups as they can in one minute requires an all-out effort - they will be more inclined to push themselves to "get that rep" and will increase likelihood of injury even more.|
|Participant awareness||most often those who have the least ability to perform an exercise properly have the least kinesthetic awareness to notice they are doing so. They are particularly at risk, as they will not be able to judge when to "modify".|
|Inappropriate modification||if you're telling them that the purpose of the exercise is to fatigue the hip flexors, and you demonstrate crunches as the variation, you're no longer fatiguing the hip flexors. To be consistent you'd need to demonstrate another hip flexor variation that was less difficult.|
|Industry guidelines/professional accountability||Since ACE recommends against doing full sit-ups in group exercise classes, your legal culpability is increased if you're an ACE-certified instructor.|
|Perpetuation of exercise myths||While you have identified a specific application (hip flexor fatiguing) where full sit-ups might be appropriate, for the general population who still thinks of them as an abdominal exercise they're really not. Bringing them back into the group exercise setting creates a mixed message, which helps fuel the "I'm tired of listening to those 'exercise experts' who change their mind all the time" phenomenon.|
This is an issue not only in exercise prescription and group exercise class design, but exercise testing as well. The timed sit-up test has often been criticized for all of these reasons as well. More and more, people who wish to assess abdominal muscular endurance prefer to use tests like the Canadian Standardized Test of Fitness curl-up test (which uses crunches instead).
--------"It's my personal opinion that people need to be more clear about what is fact and what is in fact their personal opinion." -- me