The quadriceps and hamstrings make up some of the largest muscles in the body and are critical to any lower-body workout. You can perform a variety of free-weight, cable and body-weight exercises to work these muscles, but machines can also be great tools to target the quads and hamstrings. In addition, machines help ensure proper form and are often safer to use when pushing heavy weights.
The lying and seated leg curls are the best machines for isolating your hamstrings. The leg extension machine provides that same level of isolation to the quadriceps. Integrate other leg machine exercises, such as the hack squat and leg press, to work both muscle groups simultaneously. Use a smith machine to perform exercises typically done with free weights, such as back squats, front squats, lunges and deadlifts, to round out a killer hamstring and quadriceps workout.