Having a neck that built up can cause breathing problemsAlso if you are worried about your neck you can just do isolated neck muscle exercises. I currently do a weighted neck curl with a 15 lb weight and lateral neck curls with the same weight. The neck strain you might get from a sit-up would probably be due to fast whipping movements or applying a load to your neck by having your hands behind your head and trying to begin the sit-up/crunch motion by using your arms to pull your head up.
Or if you want to look like a real BDSM psycho you can buy a head harness like at 6m10s here with varying tension band to apply resistance to neck exercises.
Tbh i think he looks better without the rubber hose implanted in his neck.Also if you are worried about your neck you can just do isolated neck muscle exercises. I currently do a weighted neck curl with a 15 lb weight and lateral neck curls with the same weight. The neck strain you might get from a sit-up would probably be due to fast whipping movements or applying a load to your neck by having your hands behind your head and trying to begin the sit-up/crunch motion by using your arms to pull your head up.
Or if you want to look like a real BDSM psycho you can buy a head harness like at 6m10s here with varying tension band to apply resistance to neck exercises.