When you think of reasons you can't work out, time and ambition usually top the list.
But for those suffering from physical limitations like Sarah Reinertsen, getting a working limb might be the biggest challenge.
"I had my left leg amputated when I was seven years old. I didn't have an opportunity to do sport. I'm gonna prove people wrong," said Reinertsen, an ironwoman triathlete.
She recently competed in a marathon that required running seven races in seven days on seven continents.
She did her first few marathons on her regular walking leg but realized there were more advanced tools to help.
"When you're an amputee and you want to get active you may have a leg that you can walk in but there are prosthetics out there that if you want to do sports and take it to the next level, you can. And though we know that a lifestyle filled with health and fitness improve your health across-the-board it's just not medically paid for," Reinertsen said.
Reinertsen will tell you there is no insurance for these type of prosthetics but the Challenged Athletes Foundation can help out.
"CAF is a nonprofit here in California that actually serves people with disabilities around the world. They pay for those running prosthetics, they pay for my cycling leg. Anywhere from $15,000 to $35,000 out of pocket," said Reinertsen.
Reinertsen uses Ossur prosthetics, which is the exclusive prosthetic partner of the challenged athletes foundation but husband Brooke Raasch says there is more to the organization than helping those who need a prosthetic.
"You could have cerebral palsy, you could be blind. They certainly help with a couple thousand athletes a year to stay active - help with equipment, they help with entry fees, they help with flights to get to races," said Raasch, who works for Ossur.
The Challenged Athlete Foundation has been around for 25 years and has raised over $50 million to help those like Reinertsen move to a healthier lifestyle.