"When I retired from athletics, that urge to be really competitive on a physical state completely died"
The former world-champion hurdler insists and three-time Olympian reveals she would never compete in any celebrity version of the programme as she has no intention of ever experiencing physical pain again.
"I just like feel like my time is done, I spent 14 years chasing that athletics dream," stresses the 39-year-old Cork woman, who has two families in tonight's final.
"Even when I train now, I train to stay healthy, I never go into the place where it's physically painful or it's a big effort.
"I don't have it in me anymore. It's like I went to the well too many times. I would be useless if I went on Ireland's Fittest Family. I would get knocked out straight away, I would probably start crying, I would be horrendous. When I retired from athletics, that urge to be really competitive on a physical state completely died."
Derval has the Mileys, from Co. Kildare ,and the Cullens, from Co. Wexford, in the final, but is wary facing hurling legend Davy Fitzgerald, who has the Mahoneys, from Co. Wexford.
"He is really focussed, the two of us can be really intense, because we take things really seriously," she reflects. "Out of all the coaches, myself and Davy are the two that are most likely to absolutely murder each other. So I always have to remind myself that it's only a competition and that we still have to be friends afterwards."
While fellow Corkonian Donncha O'Callaghan also has a team in the final, the Allens, from Co. Tipperary, their fellow county person Anna Geary will be watching from the sidelines.
Whatever about Ireland's Fittest Family, Derval's biggest challenge is handling her two lovely young children, Daphne (five-and-a-half) and Archie (nearly two), who lives with them and her husband Peter O'Leary by the sea in Crosshaven.
Daphne is in Junior Infants, but missed most of her terms last year due to lockdowns and also when her school closed due to a Covid case on the premises.
"It's been really disruptive, it's not fine for me, but she loves being at home," says Derval. "So she is living her best life, she thinks this is the best thing ever. But I have to say the whole schooling, I'm particularly useless at it."
Like everyone, Derval is fed up of the ongoing restrictions. However, the lockdowns haven't stopped her from running her own online business and product shop, which has 9,000 subscribers paying €9-a-month, which she beams is "fantastic".