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

Objective This study investigated intraindividual differences of intratendinous blood flow (IBF) in response to running exercise in participants with Achilles tendinopathy. Design This is a cross-sectional study. Setting The study was conducted at the University Outpatient Clinic. Participants Sonographic detectable intratendinous blood flow was examined in symptomatic and contralateral asymptomatic Achilles tendons 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 min (U5-U120) after a standardized submaximal constant load run. Main Outcome Measure IBF was quantified by counting the number (n) of vessels in each tendon. Results At Upre, IBF was higher in symptomatic compared with asymptomatic tendons [mean 6.3 (95% CI: 2.8-9.9) and 1.7 (0.4-2.9), p < 0.01]. 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 = 0.05]. 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 to 1.2), p < 0.01]. Conclusion Irrespective of pathology, 47-63% of Achilles tendons responded to exercise with an immediate acute physiological IBF increase by an average of one to two vessels (responders). A higher amount of baseline IBF (approximately five vessels) and a prolonged exercise-induced IBF response found in symptomatic ATs indicate a pain-associated altered intratendinous neovascularization.

Automated summary

The study found that regardless of pathology, 47-63% of Achilles tendons responded to exercise with an immediate acute physiological IBF increase, with symptomatic tendons showing a higher baseline IBF and prolonged IBF response.