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ORIGINAL RESEARCH article

Front. Physiol.
Sec. Exercise Physiology
Volume 15 - 2024 | doi: 10.3389/fphys.2024.1496825
This article is part of the Research Topic Unveiling Functional and Structural Physiological Transformations Through Muscle Stretching View all 5 articles

Acute effects of proprioceptive neuromuscular facilitation stretching on reduce rectus femoris muscle stiffness: a dose-response shear-wave elastography study

Provisionally accepted
Sara Kranjc Sara Kranjc 1Mojca Fink Mojca Fink 1Masatoshi Nakamura Masatoshi Nakamura 2Žiga Kozinc Žiga Kozinc 1*
  • 1 Faculty of Health Sciences, University of Primorska, Koper, Slovenia
  • 2 Faculty of Rehabilitation Sciences, Nishikyushu University, Kanzaki, Saga, Japan

The final, formatted version of the article will be published soon.

    Proprioceptive neuromuscular facilitation (PNF) stretching is widely used to increase range of motion, but its underlying mechanisms are not well understood. This experimental, parallel group design study investigated the acute effects of PNF stretching on rectus femoris muscle stiffness and explored a potential dose-response relationship. Thirty healthy young adults (23 females, 7 males) were randomly assigned to either a PNF stretching group (n = 15; 22.96 ± 2.2 years) or a control group (n = 15; 23.3 ± 2.1 years). Rectus femoris stiffness was measured using shear-wave elastography (Resona 7, Mindray, China) at two locations (distal and proximal) before and after the second, fourth, and sixth sets of PNF stretching. The protocol involved six sets, each with three 10-second stretches and 5-second maximal contractions. The results indicate that PNF stretching had no statistically significant effect on muscle stiffness, with no main effects of group (F = 0.05; p = 0.830) or time (F = 0.545; p = 0.653), and no significant interactions. However, the proximal location showed a substantially higher shear modulus compared to the distal location (F = 63.6; p < 0.001; η² = 0.69), independent of group or time. These findings highlight a location-specific difference in muscle stiffness that was unaffected by the intervention. In conclusion, PNF stretching did not acutely reduce rectus femoris stiffness compared to passive rest, regardless of the number of stretching sets performed. Further research is needed to understand the muscle-specific effects of PNF stretching.

    Keywords: Muscle elasticity, acute effects, dose-response, ultrasound elastography, stretching intervention

    Received: 15 Sep 2024; Accepted: 23 Dec 2024.

    Copyright: © 2024 Kranjc, Fink, Nakamura and Kozinc. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Žiga Kozinc, Faculty of Health Sciences, University of Primorska, Koper, Slovenia

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