Like many health issues, it depends on your genes. Research shows that sit-ups are tough on your spinal discs: rubbery pads that prevent your bones from grinding into one another. Disc degeneration appears to be highly variable and largely tied to genetics. This means that for some people, sit-ups present a high risk of injury. To exercise safely, make sure you take breaks between sets and consider looking for lower impact exercises that flex your muscles — without breaking your back.