Open Kinetic Chain Exercises: Definition, Examples, and Benefits

What is an example of an open kinetic chain exercise?

An excellent example of an open kinetic chain (OKC) exercise is the Leg Extension, where the distal segment (the foot) is free to move in space, allowing for isolated work on the quadriceps muscles.

Understanding Kinetic Chains

In exercise science and biomechanics, the concept of a "kinetic chain" refers to the way our body's segments (bones, joints, and muscles) are linked together. This concept, originally developed by mechanical engineer Franz Reuleaux in 1875 and later applied to human movement by Dr. Arthur Steindler in the 1950s, describes how movement at one joint can affect movement at other joints within the chain.

Kinetic chain exercises are broadly categorized into two types:

• Open Kinetic Chain (OKC) Exercises: Characterized by the distal segment (the hand or foot) being free to move in space.
• Closed Kinetic Chain (CKC) Exercises: Characterized by the distal segment being fixed or in contact with a stationary object.

Defining Open Kinetic Chain (OKC) Exercises

Open kinetic chain exercises involve movements where the end of the limb (such as the hand in an arm exercise or the foot in a leg exercise) is not fixed against a resistance or surface. This allows for movement of the joint(s) in isolation without significantly affecting adjacent joints in the same kinetic chain.

Key characteristics of OKC exercises include:

• Distal Segment Free: The hand or foot is free to move.
• Non-Weight-Bearing: Often performed without bearing body weight through the working limb.
• Isolated Muscle Activation: Tend to target specific muscles or muscle groups, making them excellent for hypertrophy, strength development in a particular range of motion, and early-stage rehabilitation where weight-bearing is not yet advisable.
• Greater Shear Forces: Can sometimes place higher shear forces on joints due to the isolated movement and lack of co-contraction from surrounding muscles for stability.

Classic Example: The Leg Extension

The Leg Extension is a quintessential example of an open kinetic chain exercise. Performed on a machine, it directly illustrates the principles of OKC.

How it Works (Leg Extension):

• Setup: The individual sits on the machine with their knees bent and the padded lever resting against the lower shin, just above the ankles.
• Movement: The individual extends their knees, pushing the lever upwards until their legs are straight or nearly straight. The foot is not fixed to the ground but moves freely through the air.
• Muscles Involved: This exercise primarily targets the quadriceps femoris muscle group, which consists of four muscles: the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.
• Why it's OKC: The distal segment (the foot) is not fixed to the ground or any immovable object. It moves freely in space against the resistance of the machine, allowing for highly isolated contraction of the quadriceps. Movement at the knee joint occurs largely independently of the hip or ankle joints.

Other Common Open Kinetic Chain Exercises

While the leg extension is a clear example, many other exercises fit the OKC definition:

• Bicep Curl: The hand (distal segment) holding the dumbbell or barbell moves freely towards the shoulder.
• Triceps Pushdown: The hand (distal segment) on the cable attachment moves freely downwards.
• Leg Curl: The foot (distal segment) moves freely towards the glutes as the hamstring muscles contract.
• Overhead Press (Seated Dumbbell): While the torso is stabilized, the hands holding the dumbbells move freely overhead.
• Bench Press (Barbell or Dumbbell): The hands holding the barbell or dumbbells move freely, pushing the weight away from the chest.
• Lat Pulldown: The hands on the bar move freely downwards towards the chest.

Benefits of Open Kinetic Chain Exercises

OKC exercises offer several distinct advantages in a well-rounded fitness or rehabilitation program:

• Targeted Muscle Isolation: They excel at isolating and strengthening specific muscles or muscle groups, which is beneficial for bodybuilding, addressing muscular imbalances, or rehabilitating a specific muscle.
• Rehabilitation Focus: In early stages of rehabilitation, when weight-bearing or complex multi-joint movements are contraindicated, OKC exercises allow for controlled, pain-free movement and muscle activation.
• Hypertrophy: The ability to isolate muscles and apply direct tension can be highly effective for muscle growth.
• Accessibility: Many OKC exercises are performed on machines, which can provide external stability and guide the movement, making them accessible for beginners or those requiring precise movement patterns.
• Strength in Specific Ranges: Useful for building strength in specific portions of a joint's range of motion, which can be beneficial for athletes or individuals with limited mobility.

Considerations and Applications

While beneficial, it's important to understand the context and potential limitations of OKC exercises:

• Less Functional for Daily Life/Sports: Because they typically involve isolated movements and often don't mimic the multi-joint, coordinated actions of daily activities or sports (which are usually CKC), they may have less direct carryover to functional strength.
• Joint Stress: In some cases, the isolated nature and lack of co-contraction can lead to higher shear forces on joints (e.g., the leg extension on the knee joint, especially with heavy loads or improper form).
• Complementary Role: For a comprehensive training program, OKC exercises are best used in conjunction with closed kinetic chain exercises. CKC exercises (like squats, lunges, push-ups) promote stability, balance, and integrated muscle action, which are crucial for functional strength and injury prevention.

Conclusion

The Leg Extension stands as a prime example of an open kinetic chain exercise, perfectly illustrating how the distal segment moves freely to isolate a specific muscle group. Understanding the distinction between open and closed kinetic chain exercises allows fitness enthusiasts, personal trainers, and kinesiologists to strategically design programs that address specific goals, whether it's building isolated muscle strength, aiding rehabilitation, or enhancing overall functional movement. Both types of exercises play vital, complementary roles in a comprehensive and effective training regimen.