Use of the Modified Thomas Test for Hip Flexor Stretching: What Are the Acute and Prolonged Effects?

Background/Objectives: The flexibility deficits of hip flexors have been identified as potential biomechanical risk factors for the lumbo–pelvic–hip complex, with postural repercussions on the trunk and lower limbs. The purpose of this study was to conduct a single gravity stretching experiment and to monitor its acute and prolonged effects. Methods: The sample comprised 14 healthy participants (8 females and 6 males). Data were collected during two-day measurement sessions. These analyzed via Kinovea software. The single intervention (i.e., gravity stretching) was performed on the first day. A modified Thomas test was used at the same time in two ways, both as a measurement and as an intervention tool. Stretching was achieved by relaxing in a position to perform the modified Thomas test where, each participant lies completely relaxed for 3 min, allowing gravity to stretch the hip flexors of the examined limb. Results: After intervention, a significant acute increase in hip extension range of motion and a decrease in knee extension range of motion were found. We did not find any significant prolonged effects; moreover, after 48 h, the hip range of motion almost returned to the initial value. Conclusions: A single 3 min stretch is very effective in terms of achieving immediate changes in the range of motion, but insufficient for long-term improvements in flexibility.