The Oscar-winning actor – whose weight has fluctuated over the years – has started a tough exercise regime in a bid to get him into shape.

Writing on his twitter page, he said: "First ride in quite some time. Sore legs, sore ass, be worse tomorrow and the next day. (sic)"

The father-of-two then told one fan: "If i stop exercising my body tries 2 return 2 its heaviest weight. (sic)"

The ‘Gladiator’ star is on a 105-day training period, which he admits is taking its toll.

He said his diet plan includes, includes "taking in roughly 2400 cal/ 2600 cal incl all beverages (sic)", as well as tough workouts, one which left him declaring: “i’m toast (sic)”

In 2009, it was revealed Russell, 47, was using a state-of-the-art gym on the set of ‘Robin Hood’ to avoid gaining weight.

A source said: "Russell is a professional. He knew he was cast to play Robin Hood, not Friar Tuck. He knows he has to stay fit."