When 42-year-old David McCullar thinks back to the early 2000s, a chapter in his life marked by rapid changes, he recalls palm trees, sunny beaches - and panic attacks that made him ill.
"I was throwing up every day," Mr McCullar said.
In 2001, the company he worked for went bankrupt. He lost his job. He left his hometown. He moved over 1,000 miles (1,600km) away, from Detroit, Michigan, to southern Florida.
He was searching for new beginnings but found panic and anxiety. A few years later, Mr McCullar suffered a debilitating back injury. He then returned home where he witnessed his parents going through a divorce. Depression followed.
"It just felt like everything was happening all at once," Mr McCullar said. "I didn't know what was wrong with me. I was thinking maybe I have cancer."
But where gastroenterologists, anti-nausea pills and indigestion drugs failed to make a difference, a podcast about "brain training" and its effects on mental health offered him hope.
Mr McCullar didn't just need medical attention, according to the podcast, he needed to exercise - his brain.
While the concept was relatively new in 2006, when Mr McCullar first heard about it, it has since grown in popularity, and now "mental health gyms" devoted to brain exercises like meditation and journaling are popping up across the US.
Just like routinely lifting weights can help muscles adapt to physical stress, some experts say performing these types of activities regularly can help people adapt to mental pressure.
In 2022, one in four US adults said that most days they are so stressed they cannot function, according to the annual Stress in America survey published by the American Psychological Association.
And, roughly three-quarters of adults (76%) said they have experienced negative health effects due to stress, including headaches, fatigue and depression.
Not long after hearing the podcast, in 2007, Mr McCullar flew to Arizona to see one of the few practitioners at the time with brain-training experience.
"My anxiety had dropped by 50% in one day," he said.
He returned to Michigan inspired and wanting to help others who were struggling like he had. In 2018, he launched Inception, the first mental health gym in the state and one of the first in the country.
"You go to a typical gym because you want to move your body and better your body," Mr McCullar explained. "Same here. You don't have to come in with a diagnosis. You come in because you want to better your psyche."
The gyms encourage people to perform mental health exercises to decrease anxiety and depression.
At Inception, Mr McCullar has designed boot camps and circuit training featuring equipment to help the brain relax: infrared saunas, zero-gravity chairs, flotation therapy tanks and neurofeedback therapy.
Jake Luhrs, founder of YourLife gym in Pennsylvania, recommends journaling to clients seeking to build self-esteem and mental resilience - when they're not lifting weights.
The gym owners hope approaching mental health through a traditional fitness lens will help reduce the stigma that stops millions of adults from seeking help.
More than half of adults in the US - over 28 million people - living with a mental illness do not receive treatment, according to Mental Health America.
"People are already familiar with going to a traditional gym," Mr McCullar said. "We're just normalising mental health by softening it with the word gym."
Vaile Wright, a senior director at the American Psychological Association, agrees that journaling, meditation and other self-soothing activities at mental health gyms are useful holistic approaches to mental health. But they are not replacements for treatment or working with a licensed mental health professional, she said.
"These places typically are not healthcare services," Ms Wright said. "That's what's important to know but not always understood by consumers. So, if they go and they get worse, that could have really significant consequences."
"How do these places handle crisis?" she asked. "How do they decide if somebody needs a higher a level of care?"
Dr Lloyd Sederer, an adjunct professor at Columbia University's Mailman School of Public Health, raised concerns about the fact some mental health gyms exist exclusively online.
Those with "actual emotional distress or illness", Dr Sederer said, will have a hard time committing to any routine activities online. For instance, Alcoholics Anonymous urges against trying to treat alcoholism solely virtually.
"If someone asked me, 'Hey doc, what's the key thing I need to do to get back functioning?' I'd say medication, therapy, diet, sleep, and exercise, those are the core," he said.
Some mental health gyms are equipped with licensed therapists and have no physical fitness element at all.
"A lot of people wait until a crisis hits to start working on their mental health," said Alexa Meyer, co-founder and CEO of COA, an online-based mental health gym using licensed therapists. "Our big mission is: how do we help society start working on their mental wellbeing earlier?"
The average delay between the onset of mental illness symptoms and treatment is 11 years, according to the National Alliance on Mental Illness.
Ms Meyer believes making mental healthcare "fun and accessible and integrated" into daily life is key for optimising mental health.
She hopes people will find the therapists at COA "as fun as your favourite fitness instructor", and the mental fitness classes, with names like Emotional Push-Up, equally engaging.
Ms Meyer defines an emotional push-up as any small exercise that can build emotional strength over time. She likened it to creating a "self-esteem file".
"Every time something good happens to you, or every time you receive positive feedback, drop that in your self-esteem file," she said.
"So that when you are going through a tough time, you can refer back to some of the positive things in your life and the positive feedback you've received."
Like with any fitness routine, "when you do a lot of (emotional) push-ups", Ms Meyer said, "over time you start to build strength."