Help with sit ups?

[dcstorm097]

I leave to Marine Corps boot camp in about a month and the area I have to improve on the most is sit ups in 2 minutes. Besides sit ups I can do 10 pull ups, circa 11:33 1.5 mile that was tested in an inclined area and rain, and 52 sit ups.When I get to 30 I just crap out and have to do a few and rest and that's how I ended up with 52. I get stinging pain in my lower back and some in my abs. My target area is ideally 100. I admit I am a total beginner on calisthenics and don't have any spinal issues. I weigh 170 at 5'6 and could stand to lose a few pounds, but most of it is muscle mass I want to lose without losing the strength. I gained a lot of this through lifting from hockey as I played at a good competitive level

My question is how many reps should I do? Should I do max reps in x amount of sets? What are some other exercises I could do? Should I STRENGTHEN my lower back with lifting, or stick with body weight, calisthenics, and then work on abs with general exercises? I definitely feel there's something going in my back because I can do 45 seconds on a front plank and then its my lower back that's the first to give out.

[noflyingcars]

sit up is a **** exercise, especially if they are assessed on how many/time.
it's a shame the army has such lousy physical valuation methods.

your lower back hurts because the sit up is mostly done by the hip flexor (and not by the abs), and this pulls violently your lower back vertebrae (towards your belly). Sit up can be really dangerous and can actually tear your spine apart (read wiki if you don't believe it).

suggestion for doing them: keep your spinal erector muscles fully contracted while you go up, this should shield your lower back from being tugged in front (I assume that your lower back is able to deadlift 200+lbs)

other than that, the difficulty of a sit up varies greatly based on where you put your hands. Hands on chest = easy, hands behind head = medium, arms stretched behind back = hard.

dunno if you're required to keep your hands in a certain position during military testing

[dcstorm097]

sit up is a **** exercise, especially if they are assessed on how many/time.
it's a shame the army has such lousy physical valuation methods.

your lower back hurts because the sit up is mostly done by the hip flexor (and not by the abs), and this pulls violently your lower back vertebrae (towards your belly). Sit up can be really dangerous and can actually tear your spine apart (read wiki if you don't believe it).

suggestion for doing them: keep your spinal erector muscles fully contracted while you go up, this should shield your lower back from being tugged in front (I assume that your lower back is able to deadlift 200+lbs)

other than that, the difficulty of a sit up varies greatly based on where you put your hands. Hands on chest = easy, hands behind head = medium, arms stretched behind back = hard.

dunno if you're required to keep your hands in a certain position during military testing

So if I work on strengthening the hip flexors and contracting the spinal erector muscles as you say, will that help?

[noflyingcars]

So if I work on strengthening the hip flexors and contracting the spinal erector muscles as you say, will that help?

what will help is strengthening the spinal erector i.e. deadlift.

the hip flexor pulls in the opposite direction, we can say it's the antagonist of the spinal erectors. The problem with the sit up is that the general population (non-lifters) have a stronger (and short) hip flexor relatively to an absolutely nil spinal erector.

Also, try to not jerk when you sit up.
Of course it's hard not to jerk if you have to get almost 1 sit up a sec, and that's a reason why timing sits up is absurd.