Lionel Sanders remains confident of being able to compete at this year’s IRONMAN World Championship – despite suffering a mystery injury which is likely to hamper his training for at least another month.
Twice a runner-up in the season’s showcase event, the 37-year-old Canadian’s bid for glory in Nice this year has been rocked by a gluteal issue which left doctors baffled and raised serious questions over when he will be able to compete again. One thing which is certain is he will now not be racing IRONMAN Lake Placid on Sunday July 20.
Unable to walk after completing a recent training session, his subsequent MRI and CT scans both came back clear, while a series of specialists were unable to find the root cause of his discomfort.
Fearing it could be a stress fracture of the sacral, he stopped training completely for a whole week and after seeking further medical advice now believes he could be suffering from the dietary-related condition known as Relative Energy Deficiency (RED-S).
RED-S affects athletes when their energy intake is not high enough to meet the demands of their training and competing schedule. It can affect a wide range of bodily functions including metabolism, menstrual function, bone health, immunity, protein synthesis and cardiovascular health.
Sanders, who started the season with impressive 70.3 wins at Oceanside and St George, had focused his entire campaign around another tilt at a title which has so far eluded him.
Now he faces a race to be ready for that September showdown, admitting that he won’t be able to run again for a number of weeks and that he will need to make major changes to his diet as he looks to recover and rebuild for the remainder of 2025.

Sanders on mystery injury
Speaking on his latest YouTube VLOG post (which you can watch at the bottom of this page), Sanders admits that while the last few weeks have been tough, the realisation that RED-S could be a contributing factor to his injury problems may just enable him to come back stronger and fitter.
“It has been a very difficult last three weeks,” he said. “I had originally intended to do Eagleman, and everything was going really, really well. Preparations were going as good as they could.
“And one evening, about three weeks ago, I did a 20K run. It felt great, I didn’t feel anything during the run but later that evening, I started to feel something a little in my gluteal area, and I didn’t think much of it.
“Next morning, I did my bike workout. Felt it a little bit afterwards but just chalked it up as maybe a little glute strain. Did a run that evening and felt it ever so slightly in the middle of the run. And then that evening, it just absolutely ballooned, and I couldn’t put pressure on my right foot. I couldn’t walk.”
With his scans coming back clear and showing no signs of injury, he had no choice but to put everything on hold.
“I was still having sharp pain, basically in every movement. I couldn’t walk normally, couldn’t go downstairs, couldn’t lift anything,” he said. “I took a week completely off of everything – the first time I’ve taken a week off in literally 15 years – and I can still feel it just walking around.
“Unfortunately, this is an extremely difficult injury to diagnose and to know exactly what it is. It’s evading the machines right now. It could still very well be a stress fracture or a stress reaction. So we’ve had to just take the approach of that is what it is.
“I’m back swimming. Fortunately, that doesn’t seem to aggravate it, and I actually seem to be getting better. Tomorrow, I’m getting back on the bike and we’ll go from there. I would think it is just a small fracture, and I caught it early, and so it’s just not showing itself on imaging. And you just need to give the body time to recover.
“We’re playing it by ear. I’m giving it a minimum of four weeks completely off running. And even then, I would say it will probably be more like six weeks off running.”
Dealing with setbacks
And in typical Sanders style, the ever-positive athlete is already starting to see the positives of a situation that he believes could have been holding him back for years, and might just be the key to unlocking improved fitness and performance in the future.
“I was so discombobulated and really frustrated at first because I just felt like I had corrected all of my errors from a training standpoint, and I was training so well, I was proving to myself that it works, that I understand what I’m doing. I’m racing well, I’m feeling great doing it. And so it just didn’t make any sense to me. It’s come out of nowhere.
“I realised after some research that RED-S is when you are not eating enough on top of your training, the amount that you’re burning while training to support your body’s functions. I would target 2,000 calories excess of what I burn in a day, and I’ve been doing that for the last ten years. However, I should be targeting 3,200 to 3,500 calories.
“I’ve not been doing that, and I have literally every single symptom of RED-S. You ain’t winning a world title if you’re not aware of how much you need to eat. That was a gaping hole in my game that I didn’t understand.
“And I’ll be honest with you. This has been an absolute blessing because this was probably the gentlest way that I could ever learn this lesson. And wow, that’s a huge performance killer.”
Amended 2025 race schedule
As for the rest of the season, and that all-important September date in Nice, Sanders has already set his sights on returning for the IRONMAN 70.3 at Louisville on August 17, before then kicking on with the planned European preparations for the World Championship.
“The season is not over. It’s a s****y, s****y time, but it also isn’t because if I do things right and I’m able to get back to it at the start of July, then I think Nice is still going to happen,” he said. “I might have to level my expectations a bit, but I still think I can do well in Nice.
“So as of right now, I’m hoping, praying, and I have a good feeling that I’m going to be back at it in three weeks or so. We’ll be in Nice, and then hopefully we’ll come back home, do a little more prep, and then I should be full steam for Marbella (the 70.3 World Championship in November).
“I think we may have just found, who knows, two, three, four percent performance gain when I get back to it because the reality is that your body can’t repair itself properly if you’re not giving it the energy it needs. So I have no idea where we’re headed, but I’m actually quite excited.”