Background: Musculotendinous reactive strength is a key factor for the utilization of elastic energy in sporting activities such as running.
Aim: To evaluate the relationship between musculotendinous reactive strength and lower-limb stiffness during running as well as to identify age-related differences in both variables.
Methods: Fifty-nine amateur endurance runners performed three 20-cm drop jumps and a constant 3-min easy run on a motorized treadmill. Reactive strength index and dynamic lower-limb stiffness were calculated with a photoelectric cell system by jumping and running, respectively. Additionally, sit to stand difference in plantar arch height was assessed as a static lower-limb stiffness measure. The cluster analysis allows the comparison between younger and older runners.
Results: No significant correlations were found between jumping reactive strength and running lower-limb stiffness. The younger group performed better at drop jumps (p = 0.023, ES = 0.82), whereas higher-but-no-significant results were found for reactive strength index and stiffness-related metrics.
Conclusions: Musculotendinous vertical reactiveness may not be transferred to combined vertical and horizontal movements such as running.
Keywords: jumping; performance; plyometric exercises; running; stretch-shortening cycle.