Mr Green is a double Olympian, having competed in the London 2012 and Rio 2016 Olympic Games in the 400m hurdles and 4x400m relay events. He also achieved bronze at both the world championships and European championships.
A spokesman said: "After a career as a successful elite athlete, Jack battled with his own mental health for many years. He then used these experiences to found his own consultancy helping leaders create a happier, more successful workplace.
"The Olympian previously worked as a wellbeing lead for the BBC, and is an ambassador for both Mind and YoungMinds."
His new role involves building relationships with Champion's clients.
“I am incredibly excited to join Champion Health as Head of Performance,” said Mr Green. “I have a passion for the relationship between performance and wellbeing. I have long understood that the foundation to being the best you can possibly be starts with good wellbeing.
“When working in sport I lived by the mantra “A happy athlete is a fast athlete” and this is the same for anyone regardless of your occupation or interests.
“If you want to be successful in your professional life, then you must first allow the human being to thrive by prioritising your wellbeing.
“My purpose in life is to help as many people as possible be the best version of themselves and Champion is the ideal partner for me to fulfil that purpose.
“Performance isn’t about being an Olympic athlete, performance is about being and feeling your best. This is something I want to champion, and I know Champion are passionate about too.
“It wasn’t until I was able to be honest and vulnerable with myself that I was able to get help and begin to thrive myself. These are some of the many values that I hope to bring to Champion in my role as head of performance,” added Mr Green.
He joins Paralympian Amy Conroy, who is an ambassador for Champion Health and has created a series of workouts for the platform.
Champion Health is a Sheffield-based startup that supports businesses who want to enhance the wellbeing of their employees.
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