Rheumatology Advance Access published online on October 9, 2008
Rheumatology, doi:10.1093/rheumatology/ken387
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Comment on: The mechanism for efficacy of eccentric loading in Achilles tendon injury: an in vivo study in humans
1Plastic, Hand and Reconstructive Surgery, Hannover Medical School, Hannover, Germany.
Correspondence to:
K. Knobloch, Plastic, Hand and Reconstructive Surgery, Hannover Medical School, Carl-Neuberg-Str. 130625, Hannover, Germany. E-mail: kknobi{at}yahoo.com
SIR, I read with great interest the recent paper by Dr Rees and co-workers evaluating the potential mechanism behind the efficacy of eccentric loading of the Achilles tendon [1]. I would like to congratulate the authors on their interesting approach since the evaluation of the underlying mechanisms of eccentric training in tendinopathy merits attention. However, I would appreciate to comment on some issues raised by the authors. I agree with the authors that besides the published regimen of 3 x 15 repetitions of eccentric training twice a day with knee bent and straight no randomized-controlled trials are currently published evaluating a different dosage and intensity of the eccentric training. One could question the 12 weeks of training as well as a potential increase of the training load (6 x 15 repetitions twice a day or even more) in contrast to the current one. Furthermore, training issues such as periodization as known from sports medicine might well apply to eccentric training in athletes too. These issues are currently not addressed in the literature and warrant further investigation.
However, I disagree with the authors by stating that they published ‘the first article to examine why eccentric loading is successful as a therapeutic intervention for mid-substance lesions of the Achilles tendon’. Actually, four male and three female healthy volunteers were included in their pilot study. Therefore, I would raise the question whether healthy Achilles tendons necessarily react the same as tendinopathic tendons, which is suggested by some of the comments of the authors as seen in the aforementioned statement as well as in the somewhat misleading title: ‘[...] eccentric loading in Achilles tendon injury.’ I do not believe that the conclusions drawn by the authors from their observations in healthy volunteers do necessarily apply to injured tendons too.
In fact, several different papers published address the aforementioned issue of the potential underlying mechanism of eccentric training in tendinopathy. In my view, one should discriminate acute effects of eccentric training (such as those tested in the recent study) in contrast to mid-term effects, such as after 12 weeks of eccentric training, in addition to the fact whether healthy or tendinopathic individuals were tested. From a mechanical point of view, a randomized-controlled trial involving 74 healthy volunteers found that a 6-week eccentric training programme results in changes of mechanical properties of the Achilles tendon [2]. As far as connective tissue turnover is concerned, 12 weeks of eccentric training in Achilles tendinopathy leads to a significantly increased collagen synthesis rate [3]. From a radiographic point of view, acute eccentric training in Achilles tendinopathy patients leads to an immediate 12% increase of the tendon volume on T2-WI with a concomitant 31% increase of the intratendinous signal [4]. Colour Doppler sonography has been applied in tendinopathy evaluating the extent of neovascularization entering the tendon. Interestingly, 12 weeks of eccentric training in tendinopathy has been reported to reduce the degree of neovascularization detected by either colour or power Doppler sonography [5]. In line, quantitative assessment of Achilles tendon microcirculation could reveal a significantly increased capillary blood flow at the point of pain in both insertional as well as in mid-portion tendinopathy [6]. Twelve weeks of eccentric training reduces the pathologically increased capillary blood flow without changes of tendon oxygen saturation [7]. In addition, Achilles tendon venous outflow is facilitated after 12 weeks of eccentric training. As far as the paratendinous tissue is concerned, eccentric-training programme performed daily over 12 weeks reduced the increased paratendinous capillary blood flow in Achilles tendinopathy by as much as 45% and decreased pain level based on a visual analogue scale [8]. Local paratendon oxygenation was preserved while paratendinous post-capillary venous filling pressures were reduced after 12 weeks of eccentric training, which appears to be beneficial from the perspective of microcirculation. In sum, several distinct mechanisms underlying the eccentric training in both healthy and injured Achilles tendons in an acute and mid-term setting have been published to date.
In addition, I would appreciate if the authors could speculate whether gender might play a role for their findings as well. Recently, 85 women were studied with the finding that Achilles tendon diameter was greater in active post-menopausal women [9]. Hormone replacement therapy appeared to ameliorate this effect on the tendon diameter. Achilles tendon microcirculation varies by gender [10]. Symptomatic female patients have similarly elevated tendon capillary blood flow compared with symptomatic male patients suffering from Achilles tendinopathy, but superior tendon and paratendon oxygen saturations and reduced post-capillary venous filling pressures indicate better tendon and paratendon Achilles tendon microcirculation in women. Based on these preliminary clinical data it would be worth studying the impact of gender on tendon properties in the various aforementioned perspectives, since gender might have an impact on biomechanical properties as well.
Disclosure statement: The author has declared no conflicts of interest.
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- Rees JD, Lichtwark GA, Wolman RL, Wilson AM. The mechanism for efficacy of eccentric loading in Achilles tendon injury; an in vivo study in humans. Rheumatology (2008) Advance Access published July 22.
- Mahieu NN, McNair P, Cools A, D’Haen C, Vandermeulen K, Witvrouw E. Effect of eccentric training on the plantar flexor muscle-tendon tissue properties. Med Sci Sports Exerc (2008) 40:117–23.[Web of Science][Medline]
- Langberg H, Ellingsgaard H, Madsen T, et al. Eccentric rehabilitation exercises increases peritendinous type I collagen synthesis in humans with Achilles tendinosis. Scand J Med Sci Sports (2007) 17:298–9.[Web of Science][Medline]
- Shalabi A, Kristoffersen-Wiberg M, Aspelin P, Movin T. Immediate Achilles tendon response after strength training evaluated by MRI. Med Sci Sports Exerc (2004) 36:1841–6.[CrossRef][Web of Science][Medline]
- Ohberg L, Alfredson H. Effects of neovascularisation behind the good results with eccentric training in chronic mid-portion tendinosis? Knee Surg Sports Traumatol Arthrosc (2004) 12:465–70.[Web of Science][Medline]
- Knobloch K, Kraemer R, Lichtenberg A, et al. Achilles tendon and paratendon microcirculation in midportion and insertional tendinopathy in athletes. Am J Sports Med (2006) 34:92–7.
[Abstract/Free Full Text] - Knobloch K. Eccentric training in Achilles tendinopathy: is it harmful to tendon microcirculation? Br J Sports Med (2007) 41:e2.
[Abstract/Free Full Text] - Knobloch K, Kraemer R, Jagodzinski M, Zeichen J, Meller R, Vogt PM. Eccentric training decreases paratendon capillary blood flow and preserves paratendon oxygen saturation in chronic Achilles tendinopathy. J Orthop Sports Phys Ther (2007) 37:269–76.[Web of Science][Medline]
- Cook JL, Bass SL, Black JE. Hormone therapy is associated with smaller Achilles tendon diameter in active postmenopausal women. Scand J Med Sci Sports (2007) 17:128–32.[Web of Science][Medline]
- Knobloch K, Schreibmueller L, Meller R, Busch KH, Spies M, Vogt PM. Superior Achilles tendon microcirculation in tendinopathy among symptomatic female versus male patients. Am J Sports Med (2008) 36:509–14.
[Abstract/Free Full Text]
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  J. D. Rees, G. A. Lichtwark, R. L. Wolman, and A. M. Wilson Comment on: The mechanism for efficacy of eccentric loading in Achilles tendon injury; an in vivo study in humans: reply Rheumatology, February 1, 2009; 48(2): 203 - 203. [Full Text] [PDF]
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