A 23-year-old woman almost lost one of her legs after a spin class due to a potentially life-threatening syndrome.
Kaelyn Franco, from the US state of Massachusetts, joined a gym in the cooler months and signed up for a spin class.
She was pushing herself throughout the class but didn't think she was overworking herself, according to NBC News.
"Being someone who played sports all my life, I found it very strange that my legs immediately buckled when I got off the bike," she wrote on Instagram in October.
"I felt like I couldn’t move."
She said her cousins were laughing, but she knew "something was wrong".
The next night, she was crying in pain and she went to hospitalised and diagnosed with rhabdomyolysis, which is sometimes referred to as rhabdo.
According to the Centre for Disease Control and Prevention, rhabdomyolysis is a serious medical condition, which is potentially fatal or can cause permanent disability.
"Rhabdo occurs when damaged muscle tissue releases its proteins and electrolytes into the blood," the CDC says.
"These substances can damage the heart and kidneys and cause permanent disability or even death."
Ms Franco's creatine kinase (CK) levels were so high, a doctor said they had not seen levels like that ever.
"At my highest my CK levels were 259,000 (the normal range is between 33-211 U/L)," she explained on Instagram.
"I couldn’t walk or move and had to be put on a catheter. I was getting nervous seeing my loved ones so worried. I had to get emergency surgery to save my leg and my life."
23-year-old woman's leg 'will never be the same'
The 23-year-old had to undergo surgery to remove the muscle that was breaking down in her bloodstream, her rhabdomyolysis had turned into acute compartment syndrome.
"Seeing my loved ones cry when my surgeon said that this surgery had just saved my life was something I’ll never forget," she said.
"Although my leg will never be the same and I’ll have lifelong complications from this, I am lucky and I am so grateful.
"I am alive and my leg was saved."
Ms Franco shared the Instagram post on October 23 and she said she was still on crutches, unable to walk on her own, but she was at home.
She said she was hopeful she would be able to move again one day and she would document her recovery in order to help others.
At he start of the Instagram post, Ms Franco said this wasn't the first time she had almost lost her life.
"This is my second experience where I have almost lost my life," she said.
"Being only 23 years old, I find it my purpose now to shed light on what I have been through to help others."
She didn't elaborate on what her first life-threatening condition was, but she did promise to share that on her Instagram "to show that no matter what you go through, there is a light at the end of the tunnel".
Do you have a story tip? Email: firstname.lastname@example.org.