‘Nordic’ Hamstrings Exercise – Engagement Characteristics and Training Responses

Abstract

The present study examined the neuromuscular activation characteristics of the hamstrings during the ?Nordic? hamstrings exercise (NHE) and changes in the eccentric strength of the knee flexors with NHE training. Initially, the normalised root mean square electromyographic (EMG) activity of the hamstrings of both limbs during various phases (90?61?, 60?31? and 30?0? of knee extension) of the NHE were determined in 18 soccer players. Subsequently participants were randomly allocated to either a training (n=10) or control group. The isokinetic eccentric peak torques of the dominant and non-dominant limbs were recorded at 60, 120 and 240?/s pre- and post-training. The EMG values of both limbs were comparable (P=0.184) and greater EMG activity was recorded at more extended knee positions of the NHE (P=0.001). 4 weeks of NHE training significantly improved peak torque by up to 21% in all assessment conditions. Data indicate the hamstrings of both limbs are engaged identically during the NHE and training results in gains in the eccentric peak torque of the hamstrings of both limbs; these gains may augment the force that the hamstrings can withstand when forcefully stretched, attenuating injury risk.

The effect of Nordic hamstring strength training on muscle architecture, stiffness, and strength

“…Additionally, when fascicle increases have been shown to occur, they increase fairly quickly; 3-5 weeks into eccentric training (Blazevich et al 2007;Baroni et al 2013;Guex et al 2016;Bourne et al 2016). The current NH intervention length of 6 weeks was similar to previous studies (Iga et al 2012;Delahunt et al 2016). Given these findings it seems unlikely that an increase in muscle fascicle length is responsible for the injury protection provided by NH exercise.…”

“…Over a 4-week NH intervention, Clark et al (2005) showed an approximate 6° shift in the angle of peak concentric torque towards knee extension. In contrast to these two reports, the knee angle of peak eccentric hamstring torque was unchanged following 4 and 6 week NH interventions (Iga et al 2012, Delahunt et al 2016. Only one study to date has directly evaluated hamstring length adaptations following a NH strength intervention, showing a 20.8% fascicle length increase after 10-weeks (Bourne et al 2016).…”

“…Eccentric training, specifically the NH curl, has been shown to improve hamstring muscle strength, even more so than traditional concentric-focused training exercises (Mjølsnes et al 2004). While, previous studies found increased hamstring muscle strength and neuromuscular control after a 4-week and 6-week NH training program, there were no changes to angle of eccentric peak torque (Iga et al 2012;Delahunt et al 2016). The present muscle volume increase (11%) and PCSA increase (12%) seen in the BFLH are comparable to eccentric training muscle volume gains in the literature (Alegre et al 2006;Duclay et al 2009;Baroni et al 2013;Franchi et al 2014).…”

“…NH strengthening programs are effective in improving eccentric strength, muscle activation, and jump height performance (Mjølsnes et al 2004;Clark et al 2005;Tansel et al 2008;Iga et al 2012;Delahunt et al 2016). Eccentric strength gains following NH interventions, 4-10 weeks in length, range from 11-21% (Mjølsnes et al 2004;Iga et al 2012;Delahunt et al 2016), with no significant concentric strength gains (Mjølsnes et al 2004;Clark et al 2005;Tansel et al 2008).…”

“…Eccentric strength gains following NH interventions, 4-10 weeks in length, range from 11-21% (Mjølsnes et al 2004;Iga et al 2012;Delahunt et al 2016), with no significant concentric strength gains (Mjølsnes et al 2004;Clark et al 2005;Tansel et al 2008). Neural adaptations also occur following NH programs, with higher hamstring muscle activation during the NH exercise after a 6-week intervention (Delahunt et al 2016).…”