[en] Hamstring muscles are significantly affected by high volume or intensity, unaccustomed or eccentric-based exercises, as a result of muscle strain-induced damage during common movements in team sports (e.g., repeated late swing phases of the running gait cycle) or training methods (e.g., flywheel training). This process of eccentric exercise-induced muscle damage leads to a loss of performance, and most importantly, an increased risk of hamstrings myotendinous injuries. Consequently, it is necessary to identify the recovery status of the hamstring muscles during the post-exercise recovery period, using rapid and cost-effective testing procedures. Therefore, the purpose of the thesis was to assess the different phases of the hamstrings muscle damage-recovery continuum after different exercise models through hamstring-specific neuromuscular tests and associated structural and oxidative damage biomarkers. In Study I, 29 healthy, physically active, young adults (15 males, 14 females) were evaluated during 72 hours after a repeated-sprint training (10x40m, recovery: 3'). The results revealed a high inter-individual variability, identifiable through the assessment of maximal voluntary isometric contraction (MVIC) torque by means of the 90°hip:20°knee test. In addition, participants who lost MVIC torque during the 72-hour recovery period also showed an increase in perceived hamstrings soreness, posterior chain range of motion (ROM) loss by the Jurdan test (only male participants), as well as an upregulation of structural (creatine kinase [CK], sarcomeric mitochondrial CK [sMtCK]) and oxidative damage (malondialdehyde [MDA], oxidative stress index [OSI]) biomarkers. In contrast, participants who did not lose hamstrings MVIC torque also showed no changes in the other neuromuscular and biochemical biomarkers. Subsequently, in Study II, 19 male, regional first-division soccer players were monitored during the 72-hour recovery period after a soccer match. The results demonstrated that early rate of force development (RFD) metrics required more than 72 hours to be recovered after a soccer match. Likewise, rapid force-generating capacity decrements were accompanied by a decrease in posterior chain ROM by the Jurdan test, and an increase in perceived hamstrings soreness and structural (CK, sMtCK) and oxidative damage (MDA, OSI) biomarkers during the recovery period. Finally, a new exercise was designed to specifically target the hamstring muscles (Study III). The results indicated that the novel exercise designed triggers a significant activation of all 4 hamstring muscles, being the lateral positioning muscles (i.e., long and short head of the biceps femoris) the most activated hamstring muscles. Then, in Study IV, 30 healthy, physically active, young adults (15 males, 15 females) were monitored during the recovery period after a training session (5 sets x 10 repetitions). The results indicated that MVIC torque and RFD through the 90°hip:20°knee test were not recovered within 72 hours, as well as posterior chain ROM by the Jurdan test (only male participants) and perceived hamstrings soreness. Finally, the decrease in hamstrings neuromuscular capacities was also accompanied by an increase in biomarkers of structural (CK, sMtCK) and oxidative damage (MDA, OSI) to the myocyte during the 72-hour recovery period. Based on the findings of the studies comprising this thesis, a standard 72-hour recovery period is not adequate to recover the hamstring muscles after sprint-based exercises or flywheel training. The recovery status of the hamstring muscles can be monitored using the 90°hip:20°knee test, especially through early rate of force development (RFD) metrics in both men and women. The screening can be accompanied by the Jurdan test for posterior chain ROM in men, and by serum biomarkers of structural (CK, sMtCK) and oxidative (MDA, OSI) damage. Using this screening, training workloads could be adapted in each microcycle to balance optimizing training with muscle recovery, thus decreasing the risk of myotendinous injuries.

[es] Los músculos isquiosurales se ven significativamente afectados por la tensión muscular durante movimientos comunes en deportes de equipo (p.e., repetidas fases de balanceo tardío del ciclo de carrera) o métodos de entrenamiento (p.e., entrenamiento con dispositivos basados en resistencia inercial). En consecuencia, considerando que los procesos sintomáticos derivados del daño muscular aumentan el riesgo de lesiones miotendinosas, es necesario identificar el estado de recuperación muscular durante el período de recuperación posterior al ejercicio, utilizando pruebas rápidas y asequibles. Por tanto, el objetivo de la tesis fue evaluar las diferentes fases del continuo daño muscular-recuperación de los isquiosurales tras diferentes modelos de ejercicio, mediante pruebas neuromusculares y biomarcadores de daño estructural y oxidativo. En el Estudio I, se evaluaron biomarcadores neuromusculares y bioquímicos durante 72 horas después de un entrenamiento de sprints repetidos específico de deportes de equipo (10x40m, recuperación: 3'). Posteriormente, en el Estudio II, los biomarcadores neuromusculares y bioquímicos se aplicaron a la práctica deportiva real, y fueron monitorizados durante el periodo de recuperación de 72 horas tras un partido de fútbol. Por último, con el fin de ampliar la aplicación de las métricas neuromusculares y los marcadores bioquímicos a un ejercicio analítico con alta sobrecarga excéntrica, se diseñó un nuevo ejercicio dirigido específicamente a los músculos isquiosurales (Estudio III). A continuación, en el Estudio IV, se monitorizaron los biomarcadores neuromusculares y bioquímicos durante el periodo de recuperación posterior a una sesión de entrenamiento (5 series x 10 repeticiones). En conclusión, el estado de recuperación de los músculos isquiosurales puede controlarse mediante el 90°hip:20°knee test, especialmente utilizando métricas tempranas de tasa de desarrollo de fuerza (RFD), tanto en hombres como en mujeres. La evaluación puede acompañarse del Jurdan test para la amplitud de movimiento articular (ROM) en hombres, pero no en mujeres, y de biomarcadores séricos de daño estructural (creatina quinasa [CK], CK mitocondrial sarcomérica [sMtCK]) y oxidativo (malondialdehído [MDA], índice de estrés oxidativo [OSI]). De este modo, se podrían adaptar las cargas de entrenamiento en cada microciclo para equilibrar la optimización del entrenamiento con la recuperación muscular, disminuyendo así el riesgo de lesiones miotendinosas.