A US woman who thought her legs were sore from doing an intense gym workout has revealed how she almost died.
Kaelyn Franco, who goes by the handle 'kofranco_' on TikTok, had taken part in her first ever spin class when she ended up in hospital after experiencing severe leg pains.
Doctors immediately diagnosed Franco with rhabdomyolysis – a life-threatening muscle condition.
According to Australia's Healthline, rhabdomyolysis is a serious condition in which damaged muscle fibres enter the bloodstream, leading to kidney failure and other problems.
Franco had to undergo emergency surgery in a desperate attempt to save her limb.
In a series of now viral TikToks, the young woman explained how she thought the pain was a result of the high-intensity workout.
She shared a snap showing off what she thought was muscle gains on her thigh, before cutting to another photo of herself lying in a hospital bed.
"Not me thinking I gained muscle doing a spin class," she captioned the post.
"On September 15 I took a spin class upon a recommendation. I love biking, I love working out, I love being active. So I thought, 'Why not give it a go, right?'" Franco said in one of her clips.
"After I finished the class, I stepped off the bike and my legs and my knees immediately buckled under me and they could not support my weight.
"Fast forward to the next day, I was hobbling around and I was in a lot of pain, here I was thinking it was just soreness and that I would feel better.
"But I didn't feel better and the pain got 10 times worse as the hours went on and eventually I decided to go to the hospital."
Franco explained her symptoms to the medical staff and said they immediately told her she had rhabdomyolysis.
"Rhabo is a breakdown of muscle tissue that releases a dangerous protein in your blood," Franco said.
Doctors hooked her up to an IV drip and monitored her creatine kinase (CK) levels, which are used to measure muscle damage. A regular CK level is between 30-200 units per litre, Franco said – and hers was at about 46,000.
Franco explained that her levels continued to skyrocket, reaching 251,000.
"Doctors at this point brought in a kidney specialist because it really affects your kidneys a lot. they also brought in an orthopaedic surgeon 'cause my legs were so swollen they were getting really, really concerned.
"My CK levels jumped to 259,000 - the highest they ever were while I was there," Franco said.
"I was rushed into emergency surgery and they did a fasciotomy to relieve the pressure in my right leg."
Franco, who spent one week in hospital, is now recovering at home. She is unable to walk.
"I'm not able to do anything by myself. I'm in pain every single day," she said.
"I use crutches to get around but even just walking for two minutes causes me a great deal of pain."
Franco said she decided to share her story not to discourage people from exercising, but to shed light on a topic "not really known or talked about".
"It's important to be cautious of these things because there's a big prevalence in spin classes lately," she said.
She emphasised that she is not a doctor and what she was saying was purely based on her experience, but she believes spin classes should have advice for first-timers "about the dangers of doing the class".
"There should be info on the signs and symptoms [of rhabdomyolysis] and the urgency when the symptoms occur, to go get treatment immediately," she said.
Franco said when starting a new training programme "you should definitely take it slow and steady".
"Always, always listen to your body," she added.
She said she will have life-long complications, but won't let it take away from her happiness and positivity.
Symptoms of rhabdomyolysis
Rhabdomyolysis is the breakdown of damaged skeletal muscle. Most people who are diagnosed with the condition are treated with fluids given via intravenous (IV) drip.
The symptoms of rhabdomyolysis include muscle weakness, low urine output, fatigue, soreness and bruising, according to Healthline.
Rhabdomyolysis is triggered by muscle injury.
"This injury can have physical, chemical or genetic causes. Anything that damages the muscles can cause this condition," Healthline says.
Patients' long-term outlook depends on the degree of kidney damage. If rhabdomyolysis is caught early, they may be able to avoid major complications and return to normal health in a few weeks.
"Several of the symptoms and complications of rhabdomyolysis are serious and may result in death if you don't get treatment for them," Healthline explains.