Leg extension

The leg extension is a resistance weight training exercise that targets the quadriceps muscle (m. quadriceps femoris) in the legs. The exercise is done using a machine called the Leg Extension Machine. There are various manufacturers of these machines and each one is slightly different. Most gym and weight rooms will have the machine in their facility. The leg extension is an isolated exercise targeting one specific muscle group, the quadriceps. It should not be considered as a total leg workout, such as the squat or deadlift.

Leg extension

The exercise consists of bending the leg at the knee and extending the legs, then lowering them back to the original position. The exercise targets all four heads of the quadriceps. These heads consist of the vastus lateralis, vastus intermedius, vastus medialis and rectus femoris. Research has shown, performing the leg extension at a 40-degree angle rather than the typical 80-degree angle can promote more rectus femoris activation.[1]

Risk of injury

Some fitness professionals and coaches advise against using an isolating leg extension machine because they believe it puts unnatural pressure on the knees and ankles.. However, this concern is based more on anecdotal evidence than on solid research. Whilst there is some evidence that the leg extension's unnatural moment arm places constant tension on the anterior cruciate ligament (ACL), there is no proof that this increases the risk of injury, except for those with pre-existing ACL issues. The leg extension is a good exercise for isolating muscular contraction in the quadriceps, but as with all isolation exercises, should be included in a holistic resistance training program working all muscles, especially antagonistic muscle pairs (such as the quadriceps, hamstrings, and gluteal muscles), to avoid muscular imbalances, which are associated with increased injury risk.