Sep 3, 2009, 5:00 GMT
Madonna is to run a 151-mile, six-day race.
US singer Madonna Madonna - who is dating 22-year-old Brazilian model Jesus Luz - said: "My body is an important instrument as well as my voice. Does working out really help with singing? Yeah, absolutely. Using your diaphragm properly is connected to having good posture.. EPA/JIM HOLLANDER
The '4 Minutes' singer is in training for the gruelling Marathon des Sables in Morocco, which is due to take place next April.
A source told America's Star magazine: "She's always been in great shape, but she is now taking things to a whole other level. She is serious about doing it."
The 51-year-old star is so keen to triumph she has warned her management to keep her schedule free for the whole month.
Madonna is known for her super-toned physique and adheres to a strict eating plan and exercise regime.
On occasions she has been forced to defend her ultra-healthy lifestyle and "unwomanly" muscular body.
Madonna - who is dating 22-year-old Brazilian model Jesus Luz - said: "My body is an important instrument as well as my voice. Does working out really help with singing? Yeah, absolutely. Using your diaphragm properly is connected to having good posture.
"Your body is one organism. You can't separate it. If you are not in good health your vocal cords will suffer. Everything will suffer."
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