The LIFTMOR trial (love the name) published in 2018 demonstrates significant improvements in lumbar spine and femoral neck density in women who engaged in just 2 strength training sessions per week for 8 months. This is a great demonstration that exercise that is appropriately challenging and well designed does not have to take a ton of time! The control group, who performed a low intensity exercise program, lost bone density :( . You can find the full trial here.
