A former athlete who struggles to walk has issued a stark warning to runners training for the marathon – beware of using orthotic insoles.

Dr Daryl Bendel, 44, from Basildon Close, Watford, has competed in a number of marathons and Ironman triathlete competitions over the years.

While training for a 35-mile run in December 2008, he injured a ligament in his right foot and was prescribed the use of orthotic insoles, a foot supporting device that controls joint motion.

South African-born Dr Bendel, who works in the biopharmaceutical industry, said: “I was prescribed the use of orthotic insoles and despite complaining of pain and saying that they were awful and uncomfortable from the outset, I was told to keep on using them.

“You expect the odd aches and pains after a run, but I thought I’d take care of myself by seeing an osteopath.

"I stressed to the practitioner that I didn’t want my training programme modified and that I hoped there would be no risks involved.

“I now find it hard to walk to the train station and have had to stop doing what I love – running.”

Dr Bendel said that since wearing the insoles, he has suffered from thigh pain, knee problems and an inflamed left ankle - diagnosed as tendonitis, where the tendon becomes inflamed, and tenosynovitis, the inflammation of the sheath (synovium) that surrounds the tendon.

He said: “In the lead up to the marathon, I want to get across how important it is runners know the dangers of using orthotic insoles.

“I’ve had to seek physiotherapy, wear an air boot and a number of my professional advisors are not confident that I will ever be able to return to my chosen sport.”

Hector Wells, member of the British Osteopathic Association, said: "Orthotic insoles are often recommended for people who have lower back pain as a result of internal rotation of their legs when they walk - usually because they have flat arches.

“However, if a patient is also experiencing pain or stiffness elsewhere the use of orthotic insoles could exacerbate the problem because the body can't easily adapt to the new posture the orthotics demand.

“It is important for experts to conduct a full health and mobility assessment and for patients to disclose any old injuries and all problem areas before recommending any possible solution, such as the use of orthotics to change their posture by improving their foot arches."