For many Americans, yoga is a relaxing activity that provides a variety of health benefits. Most notable are enhanced cardiovascular health, weight reduction and improved respiration.

But for the more than 44 million Americans suffering from osteoporosis or low bone mass, there might be some limitations.

According to research from the Mayo Clinic, individuals with thinning bones due to osteoporosis and osteopenia are at risk of injury if they perform yoga poses which overextend their spines. The researchers examined patients’ health records, medical exams and imaging and found 29 bony injuries. This included compression fractures, degeneration of disks and slippage of vertebrae.

Performing certain yoga poses may be particularly ill-advised for those suffering from severe osteoporosis. Physical therapists say “nonweight-bearing activities” such as swimming, water aerobics and exercise biking are good alternatives for those with more critical cases of osteoporosis.

But before you decide to totally give up on yoga, physical therapists actually say that individuals with osteoporosis can still benefit from the activity. After all, many yoga poses do help build bone density in all four limbs. The Mayo Clinic suggests that simply modifying yoga postures to accommodate an individual’s condition is perfectly viable. The patients that followed this approach reported reduced pain and improved symptoms.

To properly identify which yoga poses and physical activities in general may be unsafe to perform, individuals with health problems are advised by health experts to have a complete medical assessment.