Dynamic upper extremity dominant tasks such as throwing, hitting, and serving occur as the result of the integrated, multisegmented, sequential joint motion, and muscle activation system known as the kinetic chain.(1)
Also see our previous blog on kinetic chain exercises
Kinetic link principle
The kinetic link principle describes how the human body can be considered in terms of a series of interrelated links or segments.
Movement of one segment affects other segments that are both proximal and distal to the first segment.
These kinetic link systems are a series of sequentially activated body segments.(2)
The upper extremity can be viewed as a series of links including the trunk, scapulothoracic articulation, scapulohumeral or glenohumeral joints, and distal arm regions.
Each of these links can be considered independent anatomically and biomechanically, but with reference to human function must be considered a unit.(2)
Concept of proximal-to-distal sequencing
The goal of nearly all sport-related activities such as throwing, serving, and kicking a ball is to achieve maximal acceleration and the largest possible speed at the end of the linked segments.
The concept ideally states that motion should be initiated with the more proximal segments, and proceeds to the more distal segments, with the more distal segment initiating its motion at the time of the maximum speed of the proximal segment.
Each succeeding segment would generate larger endpoint speeds than the proximal segment.(2)
Although the throwing motion is an extremely rapid movement occurring within only 0.145 s, the effective synchronous sequencing of the body segments is vital to maximize the efficiency of the kinetic chain.(2)
Factors influencing Kinetic chain
Sciascia et al. suggested that the kinetic chain is influenced by multiple factors including:
Strength and range of motion (ROM) of hip,
Strength and ROM of shoulder,
Knee and Ankle mobility.
Efficient kinetic chains
Efficient kinetic chains have been shown to demonstrate decreased joint loads, maximum velocity and maximal force production during throwing.(2)
For this, it is important to have coordinated movement between the lower and upper body to help prevent injury, including proper timing for muscle activation and coordination to safely transfer energy from the lower extremities.
When this is not operating optimally, stress can develop on areas that are not used to accommodating these stresses (3) and the kinetic chain gets disrupted.
Dysfunction of kinetic chain during throwing increases stress placed on distal segments and can result in shoulder and elbow pathologies
Inadequate hip ROM and poor balance may significantly affect an athlete’s ability to transfer energy along the kinetic chain, resulting in dysfunctional movement and increased stresses on the shoulder and elbow.(2)
Role of trunk in maintaining an efficient kinetic chain
The trunk is the vital structure to deliver the force produced by the lower limbs to the upper limbs.
Proper trunk movement is important during throwing, as it is integral to the transfer of energy to distal body segments during the throwing motion.
Reduction in the development of kinetic energy of trunk increases the demand in the distal segment to maintain the same energy for the release of a ball (throwing), resulting in increased stress in the shoulder and elbow joints.
The hip/trunk area contributes approximately 50% of the kinetic energy and force to the entire throwing motion; decreased hip ROM in the dominant side hip compared with non-dominant side is highly correlated with shoulder injury and poor throwing mechanics
The scapula and glenohumeral joints are the key in facilitating energy transfer produced by lower limbs and trunk. (2)
Factors that can alter the kinetic chain:
Poor muscle flexibility
Poor muscle endurance
Decreased hip range of motion
Decreased shoulder range of motion
Poor spinal mobility
Weakness i n muscles of the rotator cuff (3)
Reduction in trunk kinetic energy development
Can Lower extremity injuries affect the transfer of kinetic chain link in overhead athletes?
Lower extremity (LE) injuries are a common source of disability and time-loss for overhead athletes.
The most predominantly affected soft tissues are the muscles, most commonly the Hamstrings.
The gastrocnemius-soleus complex and Achilles tendon injuries can lead to significant time missed from sport, and they are notorious for lingering pain even as an athlete returns to play.(4)
Kibler et al. proposed that inadequate hip ROM and poor balance may significantly affect an athlete’s ability to transfer energy along the kinetic chain, resulting in dysfunctional movement and increased stresses on the shoulder and elbow, and several studies have shown a correlation between poor lower extremity balance and overhead injuries including UCL tear. (2)
Principles of management of injuries in overhead athletes must focus on facilitating transfer of energy
The vast majority of lower extremity muscle injuries in overhead athletes are managed by nonoperative rehab protocol. (4)
Exercises for overhead athletes should focus on linking the shoulder and lower extremity to facilitate the transfer of energy and power from the lower extremity to the upper extremity.(3)
Conventional management has included relative rest, compression clothing, non-steroidal anti-inflammatory medications, various forms of manual and physiotherapy, and injections with autologous blood products such as platelet-rich plasma.
The treatment must progress through a stepwise plan emphasizing extremity range of motion, followed by muscle strengthening, agility training, and finally sport-specific exercise with frequent assessments to determine when the athlete is ready to return to practice and, ultimately, full competition.
An early phase of traditional physiotherapy for lower extremity muscle injury is maximizing core strength, trunk stabilization, and lower extremity flexibility, as multiple studies have shown that decreased core stability, decreased lower extremity flexibility, and fatigue are key risk factors for lower extremity muscle injury. They also reduce re-injury rates.
One must then begin to focus on muscle strengthening. This phase should place an emphasis on eccentric training of the injured muscle, which has been shown to be an essential method for muscle rehabilitation and future injury prevention. Its also reduce time-loss compared to non-eccentric muscle loading.
At Valley Healing Hands, we provide the best Physical Therapy treatment for overhead injuries. We provide an atmosphere developed for athletes with a one on one ratio for the best quality of care needed for maximum outcomes and return to play. Our physical therapist are highly qualified and will plan an individualized treatment routine, customized to your specific needs.
If you are an athlete or not, and if you are suffering from overhead injuries; or if there is disruption in the transfer of kinetic energy from you lower limbs to the upper limbs, you are at the right place. Contact us and be sure that our patients are highly satisfied with our services. You can learn about what they have to say about us here and get connected to us here. Our patients love us and you too will! We can get you back in the game!!!
1. Kinetic Chain Rehabilitation: A Theoretical Framework https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3361354/#
2. Step by Step Guide to Understanding the Kinetic Chain Concept in the Overhead Athlete https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7174497/
3. Importance of Lower Extremity Strengthening for Overhead Athletes https://www.athletico.com/2018/01/15/importance-lower-extremity-strengthening-overhead-athletes/
4. Lower Extremity Muscle Injuries in the Overhead Athlete https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9789236/