Ireland's top physio has warned how the road-running craze taking over the nation "will leave joggers on the scrapheap".
Internationally famous Gerard Hartmann - who treats many of the world's elite sports stars - says he has never, in his whole career, seen so many runners pounding the pavements as there are today.
The Limerick-based physiotherapist warned that running on hard surfaces is brutal on the body: it leads to multiple injuries such as shin splints, patella tendonitis, stress fractures, lower back damage and disc problems.
Hartmann - physical therapist to successive Irish Olympic teams whose clients include champion runners Sonia O'Sullivan and Paula Radcliffe - said physio clinics are packed out since the running phenomenon took hold.
He explained: "I advise all my clients: do 80pc of your running on grass. I can't overestimate the damage on your body that running on hard surfaces causes.
"The streets and roads are cracked and cambered, you are bouncing up and down on a hard surface, and the impact of it is three times your body weight. So for a 10-stone person, the impact transmission rate is about 30 stone on your body.
"When you run downhill on a road, it's seven times your body weight. Go to a park, find a soft surface. Just don't run on the road." And he now believes the couch to 10k brigade are guaranteeing significant injuries.
He said many runners are making the error of not conditioning their bodies to be fit for running.
"Running is free, convenient and it needs no equipment, so it's hugely popular.
"It is exhilarating to be out running in the open air, and some people get 'runner's high', which is a sense of euphoria after bouts of long running.
"There is a great cardiovascular benefit, and runners are aerobically fit, but overdoing it is extremely bad for your body.
"When you combine this with someone who doesn't do any flexibility training and doesn't do any strength exercising, then you are looking at guaranteed injuries. People are running themselves on to the scrapheap."
He says when he hears someone running 60 kilometres a week, he advises them to half that and spent the rest of the time doing Pilates, circuit training and yoga.
"Flexibility is the key to preventing injury, we should all do 15 minutes of it a week and, ideally, maybe a yoga class a week.
Hartmann - former Irish Ironman and triathlon champion - says marathons, and other endurance type events, are too much for the average person and we are pushing ourselves too much and defeating the purpose of fitness.
"For most people, the distance of a marathon is too much for the body.
"You'd want to be training your body for two years before taking on a marathon, even three. It needs to be built up slowly and consistently with 5k runs, 10k runs, half marathons, and doing hours of circuit training a week over that time.
"But we have people now taking on these big events like triathlons and ultra-marathons, whose bodies were never trained, who are de-conditioned. They don't come from a running background and their bodies are not given time to adjust.
"They might run for hours but ask them to do a simple plank exercise, and they fall flat on their faces. Building up core strength is crucial."
He advises clients to make running just one part of their weekly routine.
"I advise maybe 40 minutes of jogging a week, two hours of strength and conditioning circuit training and a yoga class or at least 15 minutes of stretching every week.
"Circuit training has the benefit that the body continues to burn calories afterwards and increases your metabolism. It keeps your body strong and fit - keep the running just for the enjoyment of it."
Hartmann has treated 61 Olympic medal winners and 47 world champions.
Now 53, he quit sport after he fractured his hip in a freak cycling accident. He moved his clinic from Florida to Limerick in 1996.
Aside from O'Sullivan and Radcliffe, he has treated Australian 400-metre champion Cathy Freeman, Kenyan Khalid Kanouchi, as well as Colin Jackson and Linford Christie.
Pilates guru Rosanna Davison recently said she has removed running from her fitness regime, and chooses other types of aerobic fitness instead.
The former schools athlete said: "Running is too high impact for me. I do three hours of Pilates a week and use the cross trainer instead."
Illusionist Keith Barry has not been able to run since he shattered his leg in a car accident in 2007.
"I can't run, I do gym training to keep fit instead," said Keith.