All through our sessions we stress proper squat form: bum back, weight on your heels, lordosis
You have to remember what joint to bend first on your legs when carrying load. You have three joints, which should move first? Think of it this way; whatever joint moves first, takes the whole weight of the move upon it. So think it through: should you move your ankle joint first? Have a look at that tiny, dainty joint– not really that good a choice. How about getting the infamous injury-prone knee to be the focus of all the stress your body and a bar can generate? Or how about, initially, using your massive hip joint? (a tennis-ball sized joint buried in a secure acetabulum, supported by a a massive bum muscle. ( And of-course, I’m not saying your bum is too big).
But here’s the “thing”: God knew you would be confused as to which joint to use, so she “flagged it” with a giant arse-shaped “post it note” in case you forgot. This is the joint strong enough to take all the grief when you begin to squat. Hence we say “bum back” first..
Anyway, lets talk about the Sorensen Test
According to Demoulin et al 2006 ”The test consists in measuring the amount of time a person can hold the unsupported upper body in a horizontal prone position with the lower body fixed to the examining table”
The test is accepted in its discriminative validity, reproducibility, and safety. However debate continues to surround its ability to predict low back pain. No firm explanation, beyond “women rock” , has been offered as to why “chicks” can hold it longer than guys.
Naturally motivation and discomfort tolerance are confounding factors.
A interesting review is available in PDF form at Isometric back Extension tests: a Review of Literature Maureau et al Journal of Manipulative and Physiological Therapeutics Volume 24 • Number 2001, But in essence,this report says this….(yawn….)
“For men, the mean endurance time is 84 to 195 seconds; for women, it is 142 to 220.4 seconds. For subjects with LBP, the mean endurance time range is 39.55 to 54.5 seconds in mixed-sex groups 80 to 194 seconds for men, and 146 to 227 seconds for women” whether thats remotely useful lm not sure, but if you suffer or are prone to lower back pain, (you tend to know by your appalling posture), im going to suggest you move this figure up.
Demoulin C, Vanderthommen M, Duysens C, Crielaard JM. 2006. Spinal muscle evaluation using the Sorensen test: a critical appraisal of the literature. Joint Bone Spine. 2006 Jan;73(1):43-50.