Acute effects of warming up on Achilles tendon blood flow and stiffness

The aim of this study was to investigate the acute effect of frequently used warm-up exercises on the Achilles tendon blood flow and stiffness. In doing so, we want to explore which exercises are suitable to properly prepare the athlete's Achilles tendon in withstanding high amounts of loading during sport activities. This knowledge could help sport physicians and physiotherapists when recommending warm-up exercises that are able to improve sport performance while reducing the injury susceptibility. Achilles tendon blood flow and stiffness measurements of 40 healthy subjects (20 men and 20 women) aged between 18 and 25 years were obtained before and immediately after 4 different warm-up exercises: running, plyometrics, eccentric heel drops, and static stretching. The effect of these warm-up exercises and possible covariates (sex, age, body mass index, rate of perceived exertion, and sports participation) on the Achilles tendon blood flow and stiffness was investigated with linear mixed models. The level of significance was set at α = 0.05. The results of this study showed a significant increase in Achilles tendon blood flow and stiffness after 10 minutes of running (p < 0.001 and p < 0.001) and plyometrics (p < 0.001 and p = 0.039). Static stretching and eccentric exercises elicited no significant changes. From these results, it could be suggested that warm-up exercises should be intensive enough to properly prepare the Achilles tendon for subsequent sport activities. When looking at Achilles tendon blood flow and stiffness, we advise the incorporation of highly intensive exercises such as running and plyometrics within warm-up programs