Clinical Biomechanics in Sports Flashcards

A collegiate baseball pitcher presents with shoulder pain. A biomechanical analysis reveals that his trunk rotation reaches peak velocity significantly before his pelvis does. This finding is MOST indicative of a flaw in which biomechanical principle?

Answer: Kinetic chain sequencing

The kinetic chain in throwing describes the efficient, sequential transfer of energy from the lower body, through the trunk, to the arm. The proper sequence involves the pelvis reaching peak rotational velocity before the trunk. When the trunk rotates prematurely, it disrupts this proximal-to-distal energy transfer, forcing the shoulder and arm to generate more force, which can lead to injury.

A recreational runner complains of recurrent medial tibial stress syndrome (MTSS). A gait analysis using force plates is most likely to reveal which of the following kinetic characteristics during the stance phase of running?

Answer: A high vertical instantaneous loading rate (VILR)

Studies have shown a strong association between higher impact-related ground reaction force variables and running injuries. A high vertical instantaneous loading rate (VILR) indicates that the impact forces are being applied to the lower extremity very rapidly after foot strike. This rapid loading can overwhelm the capacity of the tissues, including the tibia, to absorb the shock, contributing to injuries like MTSS.

A basketball player sustains a non-contact knee injury while landing from a jump. Video analysis shows a 'valgus collapse' of the knee. This observed movement pattern is MOST commonly associated with an injury to which structure?

Answer: Anterior cruciate ligament (ACL)

Dynamic knee valgus, or 'valgus collapse,' involves a combination of femoral adduction, hip internal rotation, and knee abduction. This specific movement pattern places significant strain on the Anterior Cruciate Ligament (ACL) and is recognized as a primary mechanism for non-contact ACL injuries. The ACL is crucial for resisting anterior tibial translation and rotational loads, which are both components of the valgus collapse motion.

A tennis player presents with symptoms of lateral epicondylalgia ('tennis elbow'). Biomechanically, this condition is most often aggravated by repetitive eccentric loading of which muscle group during a backhand stroke?

Answer: Wrist extensors and supinators

Lateral epicondylalgia primarily involves the tendons of the wrist extensor muscles, particularly the extensor carpi radialis brevis (ECRB). During a tennis backhand, these muscles work eccentrically to control the wrist and stabilize it against the force of the ball's impact, and repetitive microtrauma from this loading can lead to tendinosis.

Which of the following describes a key biomechanical role of the scapula during overhead throwing to prevent shoulder impingement?

Answer: Providing a stable base and upwardly rotating to clear the acromial space

Proper scapular motion, or scapulohumeral rhythm, is critical for healthy shoulder function. During arm elevation, the scapula must upwardly rotate, posteriorly tilt, and externally rotate. This coordinated movement elevates the acromion process, which increases the subacromial space. Failure to do so (scapular dyskinesis) can lead to impingement of the rotator cuff tendons and subacromial bursa.

A gait analysis of a long-distance runner reveals excessive foot pronation at midstance. This biomechanical finding is MOST commonly linked to an increased risk for which of the following conditions?

Answer: Plantar fasciitis

Excessive or prolonged pronation causes the foot's arch to flatten more than normal, which increases the tensile strain on the plantar fascia. This repetitive strain during the stance phase of running can lead to micro-tears and inflammation, resulting in plantar fasciitis. While overpronation can contribute to a cascade of issues up the kinetic chain, its most direct effect is on the structures supporting the arch.