Effects of high-intensity and blood-flow-restricted resistance training on tendon adaptations in older men.

PURPOSE: This study investigated the effects of combined concentric-eccentric high-intensity resistance training (HIRT) and low-load blood flow restriction training (BFRT) on tendon properties and function in older men.

METHODS

This parallel three-group controlled trial with constrained allocation included two exercise interventions (i.e., HIRT and BFRT) and a non-exercise control (CON). Participants in the exercise groups trained twice weekly for 12 weeks, and the total relative training volume was matched between groups. Assessments before and after the intervention included patellar tendon stiffness as the primary outcome, followed by tendon morpho-mechanical characteristics (cross-sectional area and tangent modulus) and knee extensor strength.

RESULTS

Leg extension one-repetition maximum (1RM) increased in both HIRT (+ 40.4%, p < 0.001) and BFRT (+ 18.1%, p < 0.01) but not in CON (p > 0.05). HIRT significantly increased PT stiffness (+ 5.5%, p = 0.034) but not BFRT (PT stiffness: - 4.1%); the presence of divergent outcomes was supported by a significant time × intervention interaction (p < 0.05). PT cross-sectional area (CSA) increased in both training groups compared with CON (+ 4.3% in HIRT, + 3.6% in BFRT; both p < 0.001) but did not differ between HIRT and BFRT (p > 0.05). Changes in muscle strength correlated positively with tendon adaptations: the change (Δ) in 1RM correlated with Δstiffness (r = 0.35, p = 0.034) and ΔPTCSA (r = 0.45, p = 0.004).

CONCLUSION

These findings suggest that HIRT may be more effective than BFRT for improving tendon mechanical function in older adults, whereas BFRT appears to preferentially affect tendon morphology rather than material properties over 12 weeks.

CLINICALTRIALS: gov Identifier: NCT05744167.