Abstract
BackgroundThe relationship between exercise-induced intratendinous blood flow (IBF) and tendon pathology or training exposure is unclear.ObjectiveThis study investigates the acute effect of running exercise on sonographic detectable IBF in healthy and tendinopathic Achilles tendons (ATs) of runners and recreational participants.Methods48 participants (43 ± 13 years, 176 ± 9 cm, 75 ± 11 kg) performed a standardized submaximal 30-min constant load treadmill run with Doppler ultrasound “Advanced dynamic flow” examinations before (Upre) and 5, 30, 60, and 120 min (U5-U120) afterward. Included were runners (>30 km/week) and recreational participants (<10 km/week) with healthy (Hrun, n = 10; Hrec, n = 15) or tendinopathic (Trun, n = 13; Trec, n = 10) ATs. IBF was assessed by counting number [n] of intratendinous vessels. IBF data are presented descriptively (%, median [minimum to maximum range] for baseline-IBF and IBF-difference post-exercise). Statistical differences for group and time point IBF and IBF changes were analyzed with Friedman and Kruskal-Wallis ANOVA (α = 0.05).ResultsAt baseline, IBF was detected in 40% (3 [1–6]) of Hrun, in 53% (4 [1–5]) of Hrec, in 85% (3 [1–25]) of Trun, and 70% (10 [2–30]) of Trec. At U5 IBF responded to exercise in 30% (3 [−1–9]) of Hrun, in 53% (4 [−2–6]) of Hrec, in 70% (4 [−10–10]) of Trun, and in 80% (5 [1–10]) of Trec. While IBF in 80% of healthy responding ATs returned to baseline at U30, IBF remained elevated until U120 in 60% of tendinopathic ATs. Within groups, IBF changes from Upre-U120 were significant for Hrec (p < 0.01), Trun (p = 0.05), and Trec (p < 0.01). Between groups, IBF changes in consecutive examinations were not significantly different (p > 0.05) but IBF-level was significantly higher at all measurement time points in tendinopathic versus healthy ATs (p < 0.05).ConclusionIrrespective of training status and tendon pathology, running leads to an immediate increase of IBF in responding tendons. This increase occurs shortly in healthy and prolonged in tendinopathic ATs. Training exposure does not alter IBF occurrence, but IBF level is elevated in tendon pathology. While an immediate exercise-induced IBF increase is a physiological response, prolonged IBF is considered a pathological finding associated with Achilles tendinopathy.
Highlights
Intratendinous blood flow (IBF) and degenerative tendon changes are a common finding in long-distance runners with Achilles tendinopathy (Hirschmüller et al, 2010)
This study showed that exercise predominantly results in a slight immediate increase of sonographic detectable IBF irrespective of training status and tendon pathology
It is not feasible to discriminate between IBF in runners and recreational participants since runners did not show an elevated amount of resting-IBF or a pronounced response following exercise
Summary
Intratendinous blood flow (IBF) and degenerative tendon changes are a common finding in long-distance runners with Achilles tendinopathy (Hirschmüller et al, 2010). In earlier studies IBF has been associated with ingrowth of neo-innervation in a failed tendon healing process and the onset of tendon pain (Alfredson et al, 2003; Rees et al, 2014). By use of high-resolution ultrasound devices and increasing sensitivity to low flow (Koenig et al, 2010; Risch et al, 2016), IBF has become detectable in up to 35% of asymptomatic Achilles tendons (ATs) (Boesen et al, 2006b; Hirschmüller et al, 2010). Detectability of IBF itself cannot be considered a pathological finding anymore (Boesen et al, 2006b, 2012; Risch et al, 2018a). The relationship between exercise-induced intratendinous blood flow (IBF) and tendon pathology or training exposure is unclear
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