Immediate effects of stretching and eccentric exercise on flexibility, stiffness, and strength in older adults with...

This study examined the immediate effects of long-duration static stretching on range of motion (ROM), muscle-tendon unit (MTU) stiffness, and muscle strength in older adults with hamstring tightness and possible sarcopenia.

Sixty-eight older adults (67.2 ± 4.5 years) were randomly assigned to long-duration static stretching (LS), standard-duration static stretching (SS), eccentric exercise (ECC), or control. Joint ROM, fascicle length (FL), MTU stiffness, and knee-flexor peak eccentric torque were assessed at baseline and immediately after a single intervention.

Significant immediate ROM improvements were observed in the LS, SS, and ECC groups (5.5°, 5.6°, and 3.1°, respectively; all p < 0.05), with no between-group differences. MTU stiffness decreased significantly after LS (median: -0.05 Nm/deg) and SS (median: -0.06 Nm/deg; both p < 0.05), whereas no changes were observed in the ECC or control groups. No significant changes in FL were detected, indicating that ROM improvements were not associated with alterations in muscle architecture. A significant main effect of time was found for knee-flexor peak eccentric torque, with no group × time interaction.

A single 30-min session of hamstring stretching did not produce greater acute improvements in ROM, MTU stiffness, or muscle strength than shorter-duration stretching or eccentric exercise. However, the magnitude of these effects did not exceed the threshold for clinical meaningfulness, as defined in the present study. Further refinement of intervention parameters (e.g., position, or intensity) may be required to elicit clinically meaningful changes in ROM in tight and possible sarcopenic muscles.