AUTHOR=Risch Lucie , Stoll Josefine , Schomöller Anne , Engel Tilman , Mayer Frank , Cassel Michael 

TITLE=Intraindividual Doppler Flow Response to Exercise Differs Between Symptomatic and Asymptomatic Achilles Tendons

JOURNAL=Frontiers in Physiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.617497

DOI=10.3389/fphys.2021.617497

ISSN=1664-042X

ABSTRACT=Objective: This study investigated intra-individual differences of intratendinous blood flow (IBF) in response to running exercise in participants with Achilles tendinopathy. Design: Cross-sectional study. Setting: University Outpatient Clinic. Participants: Sonographic detectable intratendinous blood flow was examined in the symptomatic and contralateral asymptomatic Achilles tendon of 19 participants (42±13 years, 178±10 cm, 76±12 kg, VISA-A 75±16) with clinically diagnosed unilateral Achilles tendinopathy and sonographic evident tendinosis. Intervention: IBF was assessed using Doppler ultrasound “Advanced dynamic flow” before (Upre) and 5, 30, 60, and 120 minutes (U5-120) after a standardized submaximal constant load run. Main Outcome Measure: IBF quantified by counting number (n) of vessels in each tendon. Results: At Upre, IBF was higher in symptomatic compared to asymptomatic tendons (mean 6.3 [95% CI: 2.8-9.9] and 1.7 [0.4-2.9], p=0.03). Overall, 63% of symptomatic and 47% of asymptomatic Achilles tendons responded to exercise, whereas 16% and 11% showed persisting IBF and 21% and 42% remained avascular throughout the investigation. At U5, IBF increased in both symptomatic and asymptomatic tendons (difference to baseline: 2.4 [0.3-4.5] and 0.9 [0.5-1.4], p=0.14). At U30 to U120 IBF was still increased in symptomatic but not in asymptomatic tendons (mean difference to baseline: 1.9 [0.8-2.9] and 0.1 [-0.9-1.2], p=0.03). Conclusion: Irrespective of pathology, 47-63% of Achilles tendons responded to exercise with an immediate acute physiological IBF increase by an average of 1-2 vessels (“responders”). Higher amount of baseline IBF (approximately 5 vessels) and a prolonged exercise-induced IBF response found in symptomatic ATs indicate a pain-associated altered intratendinous “neovascularization”.