Is the acute impairment of sprint performance induced by Nordic hamstrings exercise attenuated by the repeated bout effect?

Abstract

The Nordic hamstrings exercise (NHE) has been recently proposed as a viable strategy to prevent hamstrings muscles injury, promote hypertrophy and improve sprint performance. Due to its eccentric characteristics, this exercise is also known cause ultrastructural damage to the hamstrings muscles, which is often referred to as exercise-induced muscle damage (EIMD). A recent study showed that the damage induced by NHE has negatively impacted sprint performance both acutely and 1-2 days post-NHE and warranted that the implementation of this type of exercise should be carefully planned by strength and conditioning coaches. However, a broadly studied phenomenon known as the repeated bout effect (RBE) occurs following EIMD, making damaged muscles less prone to future damage induced by identical or similar bouts of exercise. Therefore, the aim of the present study will be to investigate the occurrence and magnitude of the RBE induced by a bout of NHE on indirect markers of EIMD (muscle function, soreness, stiffness and leakage of intramuscular proteins to the systemic circulation) and maximal 30-meter sprint performance (acceleration, mean sprint speed, maximal sprint speed, and sprint force-velocity profile) in college-level athletes. Our hypotheses are that: 1) the initial damage induced by NHE will result - following full recovery - in a potent RBE, and; 2) that this effect will attenuate the negative impacts of a second bout of NHE on sprint performance, especially 1-4 days post-NHE.