Effects of proprioceptive neuromuscular facilitation stretching at low-intensities with standing toe touch on developing and maintaining hamstring flexibility

Abstract

Background: Proprioceptive neuromuscular facilitation (PNF) stretching at low intensities has been rarely investigated. Previous studies have shown that hamstring flexibility after stretching is only temporary.

Objective: The aim of this study was to assess the effect of low intensities (40% and 10% of maximum voluntary isometric contraction, MVIC) of PNF stretching on hamstring muscles and to assess the effect of standing toe touch on the duration of hamstring flexibility.

Methods: This was a single-blind randomized controlled trial. Sixty-four healthy adults (age, 22.67 ± 1.73 years) were selected and divided into four groups: 40% intensity PNF stretching (P40), 10% intensity PNF stretching (P10), 40% intensity PNF stretching with toe touch (P40 with TT), and 10% intensity PNF stretching with toe touch (P10 with TT). Hamstring flexibility was measured using the active knee extension test (pre-stretching, post-stretching, and 3, 6, 9, 12, and 15 min after PNF stretching).

Results: In the P40, P40 with TT, and P10 with TT groups, significant changes were observed at all time points after stretching (p < 0.05). In the P10 group, significant changes were only observed immediately post stretching (p = 0.006) and at 3 min (p = 0.029) after stretching. In terms of maintaining the duration of flexibility, the P40 with TT and P10 with TT groups were superior to the P40 and P10 groups.

Conclusion: PNF stretching at low intensity, approaching 40% of MVIC, led to more flexibility than 10% MVIC. Additionally, standing toe touch after PNF stretching is recommended to develop and maintain hamstring flexibility.

Keywords: Flexibility; Hamstring muscles; Low-intensity; Proprioceptive neuromuscular facilitation stretching; Toe touch.