Effects of Nordic hamstring exercise on hamstring stiffness, strength, and flexibility

Kaliarntas, Konstantinos; Morais, Nelson; Souglis, Athanasios

Abstract

INTRODUCTION
Hamsting injuries are among the most common injuries in athletes. Eccentric training has been shown to reduce hamstring injury rates. The Nordic Hamsting Exercise (NHE) is an eccentric exercise performed at short muscle length and has been shown to provoke changes in hamstring muscles. This study aims to assess the effects in eccentric hamstring strength, hamstring flexibility and biceps femoris long head muscle stiffness following a 6-week NHE intervention.

METHODS
Fifteen recreational male and female athletes were randomised into an NHE intervention group (n=7; 5 males and 2 females; age: 24.0±1.8y; height: 172.0±3.0cm; body mass: 85±5.1kg) and a control group (n=8; 4 males and 4 females; age: 24.3±1.3y; height: 172.0±3.0cm; body mass: 72.3±3.4kg). Isokinetic dynamometry (Cybex HUMAC2015, Massachusetts, USA) at 60º/s and 45º for eccentric and isometric peak torque respectively, myotonometry (MyotonPro, Myoton Ltd, Estonia) and manual goniometry were used to measure the outcomes. Each outcome was measured at baseline and after 6 weeks in both groups (5 days before and after the intervention programme). All data presented as means and standard error of the mean (SE). A two-way mixed ANOVA was used for all dependent variables and a level of p < .05 was used to accept significant differences.

RESULTS AND DISCUSSION
There was an 8% increase in eccentric peak torque and 6% increase in the isometric peak torque in the intervention group (p < .05), while both outcomes were reduced in the control group (time*group interactions p<.05). These results are in line with previously published evidence [1,2]. There was a 9% increase in hamstring flexibility in the control group while no changes observed in the intervention group (time*group interaction p<.05). No significant effects were observed in muscle stiffness in both groups (time*group interaction p>.05) (Table 1). Other studies have reported decrease in muscle stiffness after a similar intervention, however, methodological differences and limitations of the current study may be responsible for these differences [3].

CONCLUSIONS
A six-week NHE training programme may increase eccentric and isometric strength, which have both previously described as risk factors for hamstring injury. It seems that NHE has no significant effect in altering muscle flexibility and stiffness. The current evidence may inform training practice in recreational athletes as well as further research.

• Presentation Conference Type: Poster
• Conference Name: ISB 2023 Congress XXIX
• Start Date: Jul 30, 2023
• End Date: Aug 3, 2023
• Deposit Date: May 1, 2023
• Publisher URL: https://www.isb-jsb2023.com/