In 2001, Spernoga, et. al., Enhancing flexibility which is a key component of optimizing athletic performance and reducing the risk of injuries. Proprioceptive neuromuscular facilitation (PNF) stretching techniques have been highlighted for their effectiveness in improving range of motion compared to other stretching methods like passive, ballistic, or static stretching. This study aims to investigate the duration of improved hamstring flexibility resulting from a unique, one-time, modified hold-relax stretching protocol.

Conducted at a preparatory military academy athletic training room, the study featured a 1 x 1 mixed-model, repeated-measures design. A total of 30 male subjects with limited hamstring flexibility in the right lower extremity participated, with an average age of 18.8 years. The subjects were randomly assigned to either the control (no-stretch) group or the experimental (stretch) group. The dependent variable measured was hamstring flexibility, quantified in degrees of active knee extension while the hip was flexed to 90 degrees.

Before the intervention, all subjects performed a warm-up routine consisting of six active knee extensions, with the final repetition serving as the baseline measurement. The experimental group engaged in a series of five modified hold-relax stretches, without any rotation, whereas the control group rested supine on a table for five minutes. Post-stretching measurements were taken at intervals of 0, 2, 4, 6, 8, 16, and 32 minutes following the protocol.

Analysis of variance indicated significant interactions between the experimental and control groups over time, as well as significant main effects for both group assignment and time. Post hoc analysis using Dunnett’s method revealed noteworthy enhancement in knee-extension range of motion among the experimental group. The increased flexibility persisted for up to 6 minutes after the conclusion of the stretching protocol.

This study’s findings underscore the potential benefits of a specific sequence of five modified hold-relax stretches in promoting hamstring flexibility. Notably, the positive impact endured for a considerable period, extending up to 6 minutes following the stretching routine’s completion. These results emphasize the efficacy of tailored stretching protocols like modified hold-relax techniques in achieving short-term gains in hamstring flexibility, which could potentially translate to improved athletic performance and injury prevention strategies.

Reference: Spernoga, S. G., Uhl, T. L., Arnold, B. L., & Gansneder, B. M. (2001). Duration of maintained hamstring flexibility after a one-time, modified hold-relax stretching protocol. Journal of athletic training, 36(1), 44.