Fascia and Muscle Stiffness in Soccer Athletes with and Without Previous Hamstring Injury

Area of Science:

• Sports Medicine
• Biomechanics
• Musculoskeletal Injury

Background:

• Hamstring injuries, particularly to the biceps femoris long head (BF), remain prevalent in athletes despite prevention efforts.
• The increasing incidence of these injuries necessitates a deeper understanding of the underlying physiological changes.
• Investigating tissue properties like fascia and muscle stiffness may reveal key differences in injured athletes.

Purpose of the Study:

• To compare fascia and muscle stiffness between soccer players with a history of BF injury and uninjured controls.
• To identify differences in biomechanical and neuromuscular characteristics associated with BF injury.
• To explore the relationship between tissue stiffness and functional deficits in returning athletes.

Main Methods:

• Utilized shear-wave elastography (SWE) to measure the shear-wave elastic modulus (stiffness) of BF and semitendinosus (ST) muscles and fascia.
• Recorded surface electromyography (sEMG) during passive and active knee flexion at multiple angles (0°, 45°, 90°).
• Assessed anatomical cross-sectional area (CSA) and maximum isometric strength.

Main Results:

• The injured group demonstrated significantly greater active SWE modulus in BF and ST fascia and muscle compared to controls (p < 0.05).
• Passive stiffness and sEMG activation amplitude were similar between groups (p > 0.05).
• Injured athletes exhibited lower isometric strength and BF anatomical CSA (p < 0.05).

Conclusions:

• Elevated fascia stiffness during active contractions in previously injured athletes may compromise hamstring function.
• These findings suggest that impaired tissue properties contribute to functional deficits in soccer players who have returned to play after BF injury.
• Therapeutic interventions focused on normalizing fascia and muscle stiffness could be beneficial for rehabilitation and injury prevention.