So, what\u2019s going on? And why might you, as a recreational rider, be affected?<\/p>\n
Narrowing of the vessel
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2025 Tour de France Femmes winner Pauline Ferrand-Pr\u00e9vot is one of several pros to suffer from IAE. Dario Belingheri \/ Getty Images<\/p>\n
\u201cThe term endofibrosis means that somewhere within the wall of a blood vessel is an increase in fibrous tissue, which is essentially scar tissue,\u201d says Professor Nick Cheshire, head of vascular surgery at Royal Brompton Hospital. <\/p>\n
\u201cNormally it\u2019s flexible and soft, especially in young people, but if an area has been irritated over a long period of time, the scar tissue builds up and starts to narrow the blood vessel. This is called \u2018stenosis\u2019, which restricts the blood flow and is a secondary effect to the fibrosis.\u201d<\/p>\n
When a cyclist is resting, all is good. But when they work hard, their muscles demand more oxygenated blood to feed working muscles. This narrowness of the blood vessel reduces blood circulation of the limb, causing pain, weakness or numbness during movement.<\/p>\n
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Leg pain is one of the ways IAE manifests. <\/p>\n
The most common symptoms are a cramping or burning sensation in one leg, usually the thigh but also the calf or buttocks. Generally, it occurs during high-intensity efforts, like out-of-the-saddle ascents or sprinting to the line, but soon settles down once intensity is lowered.<\/p>\n
Another symptom is losing power. This is how it manifested itself in Jungels, who\u2019s had two IAE operations.<\/p>\n
\u201cSymptoms for me were fatigue and a loss of wattage,\u201d says Jungels. \u201cI could feel that I just hadn\u2019t been able to hit those high, intensive numbers for a fair while. My body really struggled when we hit race pace.\u201d<\/p>\n
It was a similar tale for \u0160tybar, who said at the time of his problems in 2023, \u201cI was training well, hitting good numbers and should have been in the best shape of my life, but I just couldn\u2019t perform in races.<\/p>\n
“My legs were so tired, so sore. When we hit a climb, I was immediately dropped and could no longer do the numbers. I didn\u2019t understand. It was such a weird feeling. I felt lost.\u201d<\/p>\n
What are the causes of iliac artery endofibrosis?
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Flexion of the hip in the hunched cycling position is one reason riders like Zden\u011bk \u0160tybar have been afflicted by IAE. Tim de Waele \/ Getty Images<\/p>\n
For the general population, IAE is often down to the usual high-risk factors such as smoking and diabetes, resulting in narrowing blood vessels and painful calf muscles. For professional cyclists, it\u2019s also down to lifestyle factors, albeit the usually positive ones.<\/p>\n
\u201cIt\u2019s down to repeated movements,\u201d says Cheshire. \u201cThe arteries supplying the leg begin at the umbilicus level [commonly known as the naval or belly button]. This is where the main blood vessel exiting the heart divides into two. They\u2019re called the iliac arteries.\u201d<\/p>\n
Each iliac artery divides into an external iliac artery, which continues down the limb and becomes the femoral artery that supplies most of the lower limb, and internal iliac artery, which supplies blood to the pelvic organs, gluteal region and parts of the reproductive organs. It\u2019s the external iliac artery that\u2019s often affected in IAE, especially in cyclists.<\/p>\n
\u201cThe artery comes around the pelvis and into the leg via the groin,\u201d says Cheshire. \u201cTo enter the groin, it has to come under the inguinal ligament. As you\u2019re pedalling, the artery is irritated by the ligament.\u201d<\/p>\n
This can cause kinking and damage to the iliac artery wall, leading to a build-up of fibrous tissue within the artery. This not only narrows the artery but prevents it from dilating during exercise, impairing bloodflow and oxygen supply to the leg. <\/p>\n
The large swathes of blood associated with intense efforts passing through the narrow or kinked artery can cause further microtraumas and endofibrotic changes.<\/p>\n
This repetition of movement is at peak volume in the professional ranks with male pros accumulating over 30,000km in training and racing each year. If there\u2019s an issue, every pedal stroke will only exacerbate the situation.<\/p>\n
Although inconclusive, the cycling position<\/a> has been cited as a major reason, too, with the extreme hip flexion seen in the professional peloton combining with heavy bloodflow during hard efforts to stimulate these endofibrotic changes. That\u2019s how Jungels saw it.<\/p>\n \u201cCycling is a relatively unnatural activity for your body, so where you bend your leg from the hips, scar tissue forms inside,\u201d he said. \u201cAfter nearly 20 years of training, this can build up and prohibit bloodflow.\u201d<\/p>\n Excessively long iliac vessels could also increase the likelihood of kinking during hip flexion, while there are suggestions that systemic factors could also play a part, like some metabolic disorders and autoimmune disease such as Raynaud\u2019s, but this requires further exploration.<\/p>\n \u201cThere are very few studies on endofibrosis and athletes,\u201d says Cheshire. \u201cIt\u2019s a mixed bag. Some sufferers have a single point narrowing; some have a long area of narrowing; some it\u2019s directly underneath the inguinal ligament; some people it’s closer up to where the iliac artery begins. <\/p>\n “Like any arterial disease and narrowing of any form, whether it’s smoking and diabetes related or repetitive injury related, there are often personal anatomical factors that mean one person suffers and another doesn\u2019t.\u201d<\/p>\n Treatment options If IAE is left untreated in cyclists, it can lead to the performance decline mentioned, plus significant vascular damage and, in some cases, permanent functional impairment. <\/p>\n While it\u2019s not typically life-threatening, the impact on an athlete\u2019s career and quality of life can be severe. Which is why treatment is the only option.<\/p>\n \u201cThe ideal treatment is something that avoids damaging the muscles,\u201d says Cheshire. \u201cSo, the ideal treatment is \u2018balloon angioplasty\u2019. This is where a catheter with a small inflatable balloon is inserted into the narrowed section of the artery, which is then inflated to stretch the vessel and improve bloodflow. <\/p>\n “The problem is that this isn\u2019t very effective when faced with the tough fibrous scarring in the elite athlete population.\u201d<\/p>\n This is supported by research including a 2016 study that suggested balloon angioplasty, a minimally invasive procedure, failed in most cases, unlike surgery, which led to a 99 per cent return-to-sport rate.<\/p>\n \u201cSurgery is often the only solution for athletes, which is a really big deal because they might return to the sport, but at what level?\u201d says Cheshire.<\/p>\n \u201cIt often involves an abdominal incision before opening up the artery and then applying a patch.\u201d More specifically, once the artery wall\u2019s been opened, the narrowed section is removed and replaced with a sewn-in patch of tissue, which is either synthetic or from the rider\u2019s own vein.<\/p>\n Like arterial disease in general, it\u2019s more common in men. \u201cA ratio of about four to one, I think,\u201d says Cheshire, \u201calbeit that could be heavily down to the fact there are more male cyclists. But the main problem is in identifying the problem.<\/p>\n \u201cYou see, it depends on the narrowing. If it\u2019s less than 50 per cent, the pulse may be normal. And in fit athletes, it might not even show up on ultrasound. But there\u2019s a much greater chance it will if you increase the blood flow, as if you were exercising.<\/p>\n \u201cIt\u2019s why our investigation labs feature a treadmill and static bike. It\u2019s called the \u2018Stress Doppler\u2019 and the ultrasound is done before and after exercise. It\u2019s not routinely done but it can be invaluable for cyclists.\u201d<\/p>\n Cheshire says that recreational riders can suffer from this condition, too, and if you have concerns that you might be suffering from IAE, mention this stress test to your doctor.<\/p>\n There\u2019s also a diagnostic test called the ABI, or ankle-brachial index. The test measures blood pressure at the ankle and arm both at rest and immediately after exercise, and detects a drop in the ABI caused by reduced blood flow to the legs.<\/p>\n To ensure accuracy it should be performed in the cycling position, with exercise intensity gradually increased until symptoms appear, making the test sensitive enough to identify the condition.<\/p>\n How can you prevent IAE in the first place? That\u2019s a tricky one. You might presume bike fit <\/a>could play a part, but there is no research into its effectiveness.<\/p>\n
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Recreational riders certainly aren’t immune to IAE. Joseph Branston \/Our Media <\/p>\n