Biomechanics of Repetitive Motion Sports

By Nayan Pallegar

Undergraduate Student, Molecular and Cellular Biology

University of California, Berkeley

Dr. Charulatha Nagar, MD

Northwestern Medicine and Northwestern University School of Medicine

Abstract

Golfer’s elbow is common in athletes who engage in repetitive biomechanical motions. The identification of golfer’s elbow is commonly misunderstood due to a wide variety of differential diagnoses. This paper’s primary focus is to explain the common biomechanics that cause golfers’ elbows and the possible different sources of pain around the medial part of the elbow. This review will also highlight the problems and the anatomy of the medial part of the elbow. Treatment of a golfer’s elbow will also be an important point of discussion.

Introduction

Golfer’s elbow, also known as medial epicondylitis, is a common sports injury resulting from continuous microtrauma to the medial flexor tendon and the pronator muscles of the elbow¹. Pain originates towards the medial part of the elbow but can divaricate down to the wrist. The pronator muscles associated with causing golfers’ elbows are the pronator teres, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis; these five muscles all work together to form the flexor tendon of the medial epicondyle¹. A wide variety of sports have similar technical aspects involving movements used to generate power.

Biomechanics

In sports such as baseball, football, tennis, and javelin, the medial part of the elbow is subject to a great amount of tension. Sports involving the generation of momentum to throw an object with force have common techniques, requiring your elbow to be horizontally in line with your head to maximize the power/velocity of a throw. Once the elbow is up towards the head, the elbow will lead through the throw, with the arm extending and protonating alongside the hand⁷.

Phases of upper body biomechanic movement during throwing motion

Sports that require force to be exerted to throw an object put pressure on medial musculotendinous and ligamentous all working with the epicondyle². The general motion in releasing an object from your hand involves throwing an object from a state of no forward velocity to generating forward velocity at high speeds. Upon repetitive motion, it begins to overwork the flexor-pronator muscle group, leading to medial epicondylitis². Racquet sports are not an exception to the elbow-up technique of power generation. Sports such as tennis and badminton also utilize the elbow-up position to hit serves and overheads. The motion of serves and overheads are initiated with the elbow up and the elbow precedes the racquet in moving upwards into the serve/overhead motion³. The elbow goes from a position of being below the racquet to being above the racquet, creating torque that helps accelerate the racquet into the ball. Over time, by continuously serving and hitting overheads, much like throwing a ball, deterioration of the musculotendinous and ligamentous of the elbow, in turn, contributes to medial epicondyle².

Phases of upper body biomechanic movement during serving motion

Pronation in most sports refers to rotating your arm to the point where the palm of the hand faces outward and the thumb points down to the ground. Pronation in throwing sports and racquet sports are useful for adding speed alongside spin to a ball. Pronation is a naturally occurring mechanism and physiologically our arms instinctively pronate when engaging in a throwing mechanism to help slow down our arm towards the end of the motion⁴. When athletes pronate properly they avoid damage to the elbow by preventing full elbow extension. Repeatedly fully extending your elbow on motions similar to throwing a baseball is asking for injury as you never want your arm to reach a fully straightened-out position.

Symptoms and Diagnosis

Pain along the medial part of the elbow is the basic characteristic of medial epicondylitis. The gravity of pain varies, but pain is usually felt upon the use of the elbow, wrist, or forearm. Range of motion upon first feeling pain by the medial part of the elbow may be normal, but it may become increasingly limited leading to flexion contracture. Flexion contracture is most commonly seen in athletes who engage in repetitive throwing movements⁵.

Ulnar neuritis and ulnar collateral ligament instability need to be considered as they are possible in athletes who continuously have their elbows fluctuating above and below their head. Ulnar neuritis refers to the inflammation or irritation of the ulnar nerve which is located towards the inside of the elbow, but right behind the medial epicondyle². The ulnar collateral ligament is responsible for supporting and stabilizing the arm as it goes through throwing motions². The key to pinpointing the exact cause of injury and determining whether pain is caused by medial epicondylitis is by using an MRI or dynamic ultrasonography. MRI and ultrasonography are useful in determining whether tears in the pronator muscles connected to the epicondyle have occurred and if there are any other medial elbow problems such as ulnar collateral ligament tears².

Proposed Treatment Strategies

Treatment for medial epicondylitis varies depending on the persistence of the injury. It is important to first avoid movements that may be causing pain at the medial part of the elbow. Common acute treatments to help reduce inflammation and reduce pain include icing the area of pain and taking anti-inflammatory medication⁶. Chronic pain can be addressed by using a brace for support and corticosteroids to reduce swelling. Long-term pain may need to be addressed with more serious measures such as surgery where medial epicondyle release and open tendon repair may be done².

Conclusions

Medial epicondylitis of the elbow is common in athletes who continuously engage in certain biomechanical movements shared across a variety of sports. Athletes’ vulnerability to injury is largely determined by stroke mechanics and must be constantly worked with to make sure technical changes to movements lead to improved performance. With many other injuries originating around the elbow, diagnosing medial epicondylitis is important to ensure an athlete’s successful recovery and performance. Well-structured prevention plans and treatments whether nonsurgical or surgical will help mitigate pain towards the medial part of the elbow.

References

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