Team GB sprinter Dina Asher-Smith has condemned PureGym's Luton and Dunstable page on social media for posting a workout titled "12 Years a Slave".
PureGym has apologised after one of its branches advertised the workout to mark Black History Month.
- Black History Month 2020
- Ralph Rowe: Britain's first black Paralympic athlete
- Clive Sullivan: The first black Great Britain captain
The company's Luton and Dunstable gym made a post on Facebook, saying: "Entitled '12YearsOfSlave' (after the epic movie) this is our workout of the month designed by @MattSimpt to celebrate Black History Month.
"Slavery was hard and so is this".
The post received heavy backlash after it circulated online, and it has since been deleted.
Asher-Smith wrote: "I am shocked, hurt and stunned and confused that someone would think it appropriate to use the enslavement and brutal torture of generations of black people to characterise a workout.
"I am in disbelief that somebody thought this was okay. I understand this came from an individual who had gone against corporate protocol and this was not a PureGym sanctioned post or workout.
"Nevertheless, this should not have happened. This is exactly why diversity and inclusion training is so important for all companies and PureGym policies must be tightened so that there is approval over what goes out under their name.
"Black History Month and the Black Lives Matter have shown why we need to have widespread honest and unfiltered education around Black History.
"It is important for everyone to understand why it is so offensive and inappropriate to make this allusion."
PureGym is the largest UK gym brand by membership, and has confirmed it is investigating the matter.
The company said in a statement: "PureGym apologises unreservedly for a post regarding Black History Month made by our gym in Luton and Dunstable.
"This post was wholly unacceptable was not approved or endorsed by the company and was removed when it was brought to our attention.
"We take this matter extremely seriously and are investigating how and why this post was made. Thank you for those people who commented on this post and for raising it with us."
The man who posted the workout, Matt Simpson, has also issued an apology on Twitter: "For those who are coming across me this morning for the first time, I am the individual who posted the "12 years a slave" workout yesterday morning via the PureGym Luton and Dunstable Instagram account.
"I sincerely apologise to all whom I offended and angered in any way, shape or form, directly or indirectly. There was absolutely no malice or ill intentions meant by the post. This was a very ill judged post which I am responsible for.
"There are only excuses for it. Only a place from which the post came. Which was from a proud black man wanting to bring his history together with his passion and profession. Unfortunately as a result I have been vilified and branded racist.
"The branding of PureGym as racist could not be further from the truth in my experience. During my time at the company I have never experienced any racial prejudice and have always been given the tools and support needed.
"This is a very hard lesson for me and wholeheartedly apologise to all effected. I am deeply sorry."