Hamstrings play an important role in hip extension (straightening the hip) and knee flexion (bending the knee), which means they cast a long shadow over everyday activities—from standing up out of chair to walking or running. Balancing hamstring strength with (often-overdeveloped) quadricep strength is also essential to preventing injury. This practice requires the use of socks (or gliders or magazine for those practicing on carpet) and one or two blocks.