Acute effects of varying densities of foam roller on hamstring flexibility and eccentric strength

Abstract

Aims: The study compares the effects of varying foam roller density (FRD) on hamstring flexibility (HF) and eccentric hamstring strength (Hamecc) in active males.
Methods: Twenty-eight healthy male participants (height 176.7±5.9 cm; body mass 75.8±9.6 Kg; age 21.6±4.0 years) were randomly allocated to receive either a low density (TriggerPoint™, CORE roller, Texas), medium density (TriggerPoint™, GRID roller, Texas), high density foam roller (FR) (TriggerPoint™, GRID X roller, Texas) or allocated to a control group. Outcome measures included hamstring flexibility (HF) through active knee extension (AKE) (°) and Hamecc by Nordic hamstring curl exercise using the Nordbord, pre and immediately-post FR application.
Findings: Significant FR x time interactions were found for HF (p<0.05). Significant increases in AKE were reported post-FR application for all FR densities (p<0.05). No significant changes in strength parameters (break Angle, Peak and Average Force and Torque) were found (p>0.05). No significant interactions between strength parameters, limb, type of roller or time were found (p>0.05).
Conclusions: FR elicits immediate positive increases in HF through AKE assessment, with the lower density FR displaying the largest increases in HF. No change in strength parameters were noted with the increases in flexibility, however this does not denote that injury risk is reduced because of this. Findings provide practitioners with insight to inform decision making for the implementation of different densities of FR in practical settings.