Effects of the Nordic hamstring exercise on the architecture of the semitendinosus

BACKGROUND: Eccentric strength training changes muscle architecture but it is also an important factor for the prevention of injuries and their rehabilitation. OBJECTIVE: To determine the architectural adaptations of the semitendinosus (ST) after an eccentric strength training protocol with Nordic hamstring exercise (NHE), followed by a subsequent detraining period. METHODS: Twenty-three male individuals, aged 25.5 +/- 3.3, completed an 8 week intervention, where the architectural characteristics of the ST were evaluated using a two-dimensional ultrasound before (pretest-week-1), after the training period (posttestweek-9) and at the end of the detraining period (retest-week-13). RESULTS: The post-test scores indicated that eccentric strength training resulted in a significant increase in the fascicle length (FL) (t = -12.5, d = 3.53, P < 0.01) and muscle thickness (MT) (t = -9.69, d = 2.85, P < 0.01), whereas the pennation angle (PA) decreased significantly (t = 6.42, d = 1.76, P < 0.01). In retest, both FL (t = 9.7, d = 2.65, P < 0.01) and MT (t = 9.18, d = 2.65, P < 0.01) decreased significantly, whereas PA showed a significant increase (t = -5.39, d = 1.47, P < 0.01). CONCLUSION: The NHE seems to generate adaptations in ST architecture, which, in addition, are also reversible after a detraining period. These results may have practical implications for injury prevention and rehabilitation programmes.