435 FO35 – Undertaking an eccentric or isometric training program alongside a periodised sprinting intervention alters strength, architecture and sprint performance in Australian Footballers during a competitive season

Background

Including the Nordic hamstring exercise (NHE) as part of a training program reduces hamstring strain injury (HSI) risk. The lack of NHE implementation may be due to fear of muscle soreness caused by this eccentric stimulus, which has led to interest in isometric interventions. Despite interest in isometric hamstring exercises, there has been limited research into the benefits of these interventions on HSI risk factors and sprint performance.

Objective

Investigate impact of an isometric (ISO) or NHE intervention, alongside a sprint training program on hamstring strength, architecture and sprinting performance in Australian Footballers.

Design

Interventional cohort trial

Setting

Across the pre-season and in-season period of the Victorian Football League (VFL) competition. The VFL is a second tier, semi-professional Australian Football competition.

Participants

25 male athletes (age = 22±3yrs; height = 1.85±0.07m; body mass = 81.3±6.7kgs) were recruited and consented to participating. All 25 athletes completed the study.

Interventions

Across the pre-season and in-season periods, as part of their weekly team resistance training sessions, all participants completed one of either the NHE or ISO hold exercises. All participants also undertook a periodised sprint training intervention prior to their on-field football specific sessions.

Main Outcome Measurements

Biceps femoris long head (BFlh) architecture, isometric and eccentric knee flexor strength and sprint split times were measured before and after the intervention.

Results

Following the intervention both groups had significant improvements in BFlh fascicle length (NHE:1.16cm,p<0.001; ISO:0.82cm,p<0.001), muscle thickness (NHE:0.11cm,p=0.032; ISO:0.21cm,p=0.002) and eccentric strength (NHE:83N,p<0.001; ISO:83N,p=0.018). Both groups finished the intervention weaker isometrically (NHE:-45N,p=0.022; ISO:-80N,p<0.001). The NHE group improved their 5m sprint time 3.3%.

Conclusions

ISO and NHE training with a sprinting program can increase BFlh fascicle length, thickness, and eccentric strength. NHE training also improves 5m sprint time. These findings provide unique, contextually relevant insights into the adaptations possible in semi-professional athletes.