Most of you probably haven’t heard of open and closed chain exercises. But chances are, you do them all the time without even knowing it. It’s important to understand the difference between the two because one type is safer while the other can increase your risk of pain and injury. Do you know the difference?The “chain” that these terms refer to is the kinetic chain of the body, which simply means that all of your bones and muscles are connected in a “chain” and therefore the movements you make are also part of a that kinetic chain.Open Chain Exercises: Put simply, your hand or foot is free to move during an open chain exercise (like a chest press). These types of movements tend to isolate a single muscle group and a single joint. For example, the one joint involved during a leg extension is the knee and the muscle group it isolates is the quadriceps. Open chain exercises can be done with or without added weight, but when weight is added, it’s usually placed at the distal (far away) portion of the limb (like the ankle). Examples of open chain exercises include chest presses, biceps curls, leg curls, and leg extensions (with or without added weight).Closed Chain Exercises: During these movements, your hands or feet are in a constant, fixed position (usually on the ground) during the exercise (such as pushups). Closed chain exercises work multiple joints and multiple muscle groups at once. For example, a squat involves the knee, hip and ankle joints, and multiple muscles groups (quads, hamstrings, hip flexors, calves and glutes). Closed chain exercises can be done with body weight alone or with added weight. When external weight is added, it is usually rested across the back of the shoulders or the front of the chest, which is considered much safer than the “distal” placement of weight during open chain exercises. Examples of closed chain exercises include pushups, pull-ups, squats, and lunges, all of which can be done with or without added weight.So why does this matter?In general, fitness experts, physical therapists, and athletic trainers agree that closed chain exercises are better for you. Here’s why: 1. Closed chain exercises better mimic activities of daily living, which means they improve your “functional” fitness. They’re great for athletes, too, since sports require multiple joint and muscle movements to happen at once. Very few movements in real life or in athletics isolate joints and muscles like open chain exercises do. 2. Closed chain exercises work many muscle groups at once. That’s great for the reasons above, but also because you can get more benefit in less time. 3. Closed chain exercises are safer for your joints—especially the knee joint, which is very vulnerable to stress and injury. The force involved in closed chain exercises like lunges and squats is compressive, meaning it actually stabilizes the joint and helps strengthen it. In contrast, open chain exercises, like knee extensions or hamstring curls produce shear force, which stresses the knee joint (and the ACL) and is more likely to result in injury. What does this mean for you?If you suffer from joint pain or previous joint injury, you should try to avoid open chain exercises at that particular joint. So, if your knees are bad, do squats and lunges (closed chain exercises) instead of leg extensions or leg curls (open chain exercises). If you injured your elbow, do pushups (closed chain) instead of chest presses (open chain); if you have shoulder issues, try pull-ups in lieu of overhead presses, and so on.In general, the knee joint is the most vulnerable joint in the entire body. So it’s a good idea to limit the amount of open chain exercises you do for the lower body—especially with heavy weights—to prevent problems from occurring in the first place.Personally, I think this gives even more reason to vary your exercise program. I do both open and closed chain exercises, but I NEVER perform any open chain exercises for the lower body unless it involves little to no added weight. That means that I do not use machines for leg extensions or hamstring curls, because the added weight and the position of that weight (again, on the “distal” part of the leg) is risky for the already-vulnerable knee joint. Squats and lunges are some of the best exercises you can do anyway, so those are my go-to exercises for the lower body. Since the joints of the upper body aren’t as prone to injury as the knee is, I do both open and closed chain exercises, but I try to vary between the two on a regular basis.How about you? Will you avoid open chain exercises now that you know the difference?