Bad Effects of Leg Weights

X-rays of human foot and leg

Leg and ankle weights are sometimes used to augment exercise or training in hopes of seeing faster or greater results. The theory behind using these weights is that they increase resistance on the legs so you will burn more calories, develop muscle more quickly and be able to run or jump faster than you could before. Adding weights to your legs usually won't result in these improvements, however, and may actually increase your chance of injury.

Foot and Ankle Injuries

Depending on the size and positioning of your leg weights, you may be putting additional strain on your feet and ankles, making them more prone to injury. As most weights of this kind strap around the ankle, wearing weights puts a hard surface against the bones of your upper foot and ankle that can rub against the ankle when you move, hit against the foot and ankle if the weights are loose and potentially cause more serious injuries if you fall or accidentally twist your ankle during exercise.

Movement Restriction

Although leg weights are often used by runners and other athletes in hopes of increasing speed, in many cases the weights restrict your normal range of motion and change your natural gait, which results in a slower overall speed. This restriction is caused by the increased weight that your legs must bear and the positioning of the weights on your ankles; the muscles of your legs must work harder to move the weight, resulting in the muscles tiring faster and making smaller motions to compensate.

Tendon and Ligament Injury

The increased weight on your legs puts more of a strain on the connective tissues of the leg, especially because your legs typically support body weight from below and aren't used to supporting weight at the ankles. When running or performing other exercise, the increased weight at the bottom of your legs can cause overextension, tendon strain and other connective tissue injuries as your connective tissues must deal with additional force to which they are not accustomed.

Knee, Hip and Back Pain

Having weights on your legs increases the strain placed on your knees, hips and lower back. Depending on the amount of weight you use, leg weights can significantly increase the force of impact that your body experiences with each foot strike. This impact is absorbed by the ankles, knees, hips and lumbar vertebrae; increasing the impact also increases the amount of impact force that your joints and back must absorb. The increased impact can result in joint injury, swelling within the joints, changes in spinal alignment and other joint problems.

Muscle Imbalance

The muscles of your legs have to work harder to lift your feet when weights are present, resulting in the quadriceps muscles becoming stronger at a faster pace. The hamstring muscles that act as an antagonist to the quadriceps don't experience this increase, however; the hamstrings will perform the same amount of work, and in some cases the weights may actually decrease the amount of work that the hamstrings have to do when lowering your foot. As the muscle imbalance increases, so does your risk of muscle injury during exercise.

Slowing Weight Loss

Leg weights increase the amount of energy that your leg muscles require to run, jump or perform other exercises. Depending on the actual weight you use when training, this can result in the body prioritizing its energy sources to burn carbohydrates and other high-energy fuels first. When this occurs, fat is not burned as readily and your muscles may tire before the body begins using its fat stores.