"Mums come to us feeling the pressure to bounce back," Norman said.
A quick Google search revealed links telling women how to "lose your mum tum", she said.
"Those kinds of messages are out there all the time. Women are rushing back to boot camp or back to the gym without the understanding that they really need to take this slow."
High-intensity exercise, including running, burpees, crunches and planks, all had the potential to do serious harm to post-partum bodies.
Smith said they were "heartbroken" to hear stories from women around the country who didn't know they should avoid such exercises until they had rebuilt their strength, and had ended up with nasty injuries.
"They don't know what they don't know."
Some of the main dangers of intense exercise after having a baby can include tearing apart your abdominal muscles, which are usually already partly separated from the pregnancy, or suffering pelvic organ prolapse. Such injuries could require surgery to fix.
"It's really important that women know when they do get back into exercise they can't just trust that by walking into a gym they are going to be in safe hands," Norman said.
Many personal trainers had little or no training on safe post-partum exercise.
Traditionally, women were encouraged to wait until at least six weeks after having the baby to start exercising again - with approval from their GP and midwife - but Smith and Norman said every woman was different and might need more time before starting again.
Even then, women should be taking it back to absolute basics and avoiding high-intensity workouts.
Norman said good exercises to begin with included the "superman", with the person on all fours extending opposite hands and legs, as well as "deep, diaphragmatic breathing" and focusing on posture.
It was "really about setting those foundations".
Mobility and stretching were also excellent to work on in the early days.
"Slow and steady really does win the race at the end of the day," Smith said.
"The big message from us is just unfortunately anyone these days, especially with social media, can call themselves a fitness professional."
They wanted mums to know how to advocate for themselves and recognise what could harm them.
They instead moved towards empowering mothers to care for themselves and take it easy.
"We encourage women to spend 20-30 minutes on themselves and make themselves feel good," Norman said.
"Our core message is that exercise makes you feel amazing ... [it's] all about moving forward in terms of physical and mental health."