The role of neuromuscular inhibition in hamstring strain injury recurrence

Abstract

Hamstring strain injuries are amongst the most common and problematic injuries in a wide range of sports that involve high speed running. The comparatively high rate of hamstring injury recurrence is arguably the most concerning aspect of these injuries. A number of modifiable and nonmodifiable risk factors are proposed to predispose athletes to hamstring strains. Potentially, the persistence of risk factors and the development of maladaptations following injury may explain injury recurrence. Here, the role of neuromuscular inhibition following injury is discussed as a potential mechanism for several maladaptations associated with hamstring re-injury. These maladaptations include eccentric hamstring weakness, selective hamstring atrophy and shifts in the knee flexor torque-joint angle relationship. Current evidence indicates that athletes return to competition after hamstring injury having developed maladaptations that predispose them to further injury. When rehabilitating athletes to return to competition following hamstring strain injury, the role of neuromuscular inhibition in re-injury should be considered.

Biceps Femoris Long Head Architecture

“…Inhibition o f the previously injured hamstrings seems to be greatest at long muscle lengths (34), and this would be expected to shift torque-joint angle relationships to shorter lengths. It has also been argued that neuromuscular inhibition and its preferential effect on eccentric strength after hamstring injury (25,26) may also contribute to the persistence of architectural deficits (14). Fascicles may shorten in response to the reduced excursions experienced in the early stages of recuperation.…”

“…Shifts in the angle o f peak torque toward shorter muscle lengths have been proposed to be indicative o f a reduction o f in-series sarcomeres and muscle fascicle length (6). Lesser fascicle lengths after HSI, hypothesized previously (6,14), might be most troublesome for reinjury because these would increase muscle susceptibility to eccentrically induced microscopic muscle damage, which may be a precursor to macroscopic damage in the form of a muscle strain injury (23). However, it is not yet known if a previously strained biceps femoris long head (BFlh) displays shorter fascicles compared to an uninjured BF|h.…”

Architectural adaptations of muscle to training and injury: a narrative review outlining the contributions by fascicle length, pennation angle and muscle thickness

“…From the available literature, the isokinetic dynamometry-derived torque-joint angle relationship has been used to postulate the effects of prior hamstring strain injury on fascicle length 9 85–87. These studies suggest that a shift in the angle of peak torque of the knee flexors towards shorter lengths in individuals with a previously injured hamstring, is the result of a reduction in the number of in-series sarcomeres, and a decrease in the optimum length for force production 9 20 87…”

ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION & THE HAMSTRINGS Implications for injury prevention & rehabilitation

“…These deficits appear to persist even after a successful return to sport (Fyfe et al, 2013), which suggest that conventional rehabilitation programs are ineffective in restoring optimal structure and function to this most commonly injured muscle. Given that the acute T2 patterns observed after a single exercise bout closely match the hypertrophic adaptations experienced as a consequence of 10 weeks of training (Bourne, Duhig, et al, 2017), the results of the current study suggest that the Nordic hamstring exercise is unlikely to be the optimal stimulus for restoring BFLongHead volume in cases of atrophy.…”

“…The mechanism(s) increasing the risk of future HSI in individuals with a history of this injury remain unclear; however, it is likely to occur from the contribution of a number of maladaptation's following HSI (Fyfe, Opar, Williams, & Shield, 2013;Opar et al, 2012) or the persistence of risk factors that contributed to the initial injury (Croisier, Forthomme, Namurois, Vanderthommen, & Crielaard, 2002;Silder, Heiderscheit, Thelen, Enright, & Tuite, 2008;Witvrouw et al, 2003).…”