Semitendinosus and biceps femoris long head active stiffness response until failure in professional footballers with vs. without previous hamstring injury

ABSTRACT

This study sought to examine the active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh) during a knee flexor isometric contraction at 20% of maximal voluntary isometric contraction until failure in elite footballers (n = 50, age: 22.3 ± 5.3 years; height: 1.82 ± 0.08 m; body mass: 74.7 ± 9.0 kg). Active stiffness was assessed using ultrasound-based shear wave elastography by means of shear modulus quantification. Comparisons were performed between limbs with (n = 11) vs. without (n = 89) previous hamstring injury. A similar time until failure in the knee flexor fatigue task was observed between groups (p = .401). At the start of the task, lower limbs with previous hamstring injury showed a lower BFlh active stiffness (31.0.1 ± 10.4 kPa, p = .023) and BFlh/ST active stiffness ratio (0.50 ± 0.29), and no differences for ST (72.8 ± 26.8 kPa, p = .221) compared to lower limbs without previous hamstring injuries (BFlh: 38.0 ± 9.6 kPa; ST: 64.0 ± 18.4 kPa; BFlh/ST: 0.65 ± 0.27). During the task, the ST active stiffness in both groups decreased from 80% of task time (p = .032), in the absence of changes in BFlh active stiffness (p = .534), resulting in an increase in BFlh/ST active stiffness from 80% of task time (p = .029). No differences between limbs were observed during the fatigue task for all parameters (p > .099). Future research is warranted to verify if the differences found represent an increased risk of hamstring injury.

Highlights

• The hamstring's active stiffness response to a fatigue protocol in soccer athletes with a history of injury is unknown.

• Athletes with previous injury showed less active stiffness in the biceps femoris long head.

• Similar response to fatigue was observed between athletes with and without hamstring injury history.

KEYWORDS:

• Fatigue
• hamstring
• shear wave elastography
• shear modulus
• knee flexors

Acknowledgement

We thank to Sport Lisboa e Benfica for lending one Aixplorer unit.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work is part of the HamStrong project which is supported by the Fundacao para a Ciencia e a Tecnologia (grant PTDC/SAU-DES/31497/2017); and by CIPER–Centro Interdisciplinar para o Estudo da Performance Humana (unit 447) which is also supported by Fundacao para a Ciencia e a Tecnologia (grant UID/DTP/UI447/2019).