this is in reference to the 15 august wod caption: i wonder if back extensions and regular sit-ups are a good indicator of strength/endurance discrepency. one starts horizontal and ends vertical, getting easier through the range of motion while the other starts vertical and ends horizontal. even that oversimplifies the difference as part of the trunk is supported during the first half of the sit-up (with the exception of ghd situps) so there is less of a load on the stomach muscles than during the back extension where the load is constant.
i would think a better comparison would be vertical situps (hanging from a bar or strapped into an inversion board) versus the back extension or regular situps versus good mornings without weight.
moreover, i have noticed the opposite discrepency when doing ghd sit-ups versus ghd back extensions-i can do about 20 proper situps versus about 55-60 back extensions.