Effects of Lower-Leg Fascial Flossing on Flexibility and Performance in Collegiate Distance Runners: Ultrasound Evaluation of Fascial Gliding

Background: Long-distance runners frequently experience repetitive loading that may contribute to reduced flexibility, impaired fascial gliding, and neuromuscular performance deficits, all of which may hinder recovery and increase overuse risk. Fascial flossing-a compressive myofascial technique-has gained attention as a potential intervention; however, evidence on its role in post-fatigue recovery remains limited. Hypothesis/Purpose: To determine whether lower-leg fascial flossing improves fascial gliding, flexibility, perceived tightness, and jump performance following running-induced fatigue. Study Design: Randomized controlled cross-over study. Methods: Nationally competitive male collegiate long-distance runners were recruited from a university track and field team via institutional and verbal announcements. Participants completed a treadmill fatigue protocol followed by unilateral lower-leg fascial flossing, with the contralateral leg serving as control. Pre- and post-intervention assessments included ankle dorsiflexion range of motion (Weight-Bearing Lunge Test), perceived tightness (Visual Analog Scale), myofascial gliding via ultrasound cross-correlation analysis, and Reactive Strength Index from repeated rebound jumps. Statistical analysis was performed using a mixed-model repeated-measures analysis to examine condition × time interactions. Results: Seventeen nationally competitive male collegiate distance runners (mean age 20.1 ± 0.8 years) completed the protocol. Significant condition × time interactions were observed for all outcomes. Perceived tightness decreased in the flossed leg but increased in the control leg (p = 0.0499, partial η² = 0.101). Both legs improved dorsiflexion ROM, with greater gains in the flossed leg (p = 0.0084, partial η² = 0.085). RSI declined in the control leg, while the flossed leg maintained performance levels (p = 0.0043, partial η² = 0.109). Myofascial gliding improved only in the flossed leg (p = 0.0093, partial η² = 0.091), suggesting enhanced tissue mobility. Conclusion: Lower-leg fascial flossing enhanced flexibility, reduced tightness, and preserved jump performance after running-induced fatigue. This technique may represent a practical, low-cost, and time-efficient recovery strategy for endurance athletes and practitioners seeking to optimize post-exercise recovery. Level of Evidence: Level 2.