I have heard that imagining you are exercising will actually increase your fitness.
I was wondering if maybe I could dream that I am exercising?
Also, whilst exercising I like to listen to music. Is that possible in a dream?
Yes it is possible to listen music but I don think that you will loose some weight in your sleep!!!
I agree with Fiko, you can listen to music in your dreams (I have before) but I don’t think you’d lose weight by excercising…
Last year I had a dream that I was jogging again and looking up into towering trees that were full of birds and all kinds of natural life – it was such a great feeling, after not having jogged in real life for so long, that I made an appointment to get my knee working again with a physical therapist and now I’m up to walking at almost 5 miles per hour. So I would say that dreaming about exercise DOES help – it inspires you to figure out how to do it again.
That’s pretty cool al! 
However, can you train some of your physical abilities in the dreamworld?
Like. You train like boxing and try new things out, would you know how to do the same things in the physical world after the dream? (Of course not to go overboard and go all crazy and do things that are physically impossible)
Ohhhh, I remember some study i saw done where people were asked to either work out their pinky for 5 minutes a day, dont work out at all, or THINK about working out their pinky for 5 minutes a day. My statistics may not be accurate cuz i saw it ages ago but i think the ones who DID exercise increased pinky stength by 50%, and the ones who THOUGTH about it increased strength by 30%. Thats amazing!
according to this that means you can increase your strength by dreaming about say lifting weights.
Hmm … no, I have to say that idea has never even occurred to me! But it sounds like something I would like to try. For example, I would like to be able to sing (but can’t!). I might just try this sometime soon (singing a high note in my imagination right this very moment!).
As said before, dreams can inspire you, and i might add: to teach you “how to”. While the real training will be done in real life, in dreams you can try out different techniques, or let your brain figure out what is the best way to “how to” certain things.
For example, in dreams you sometimes face the situation, what you really need to face next day IRL. So your brain is pre-working out some solutions how to perform in such situation. Sometimes the solution is better than this what you would have figured out IRL, and you just perform like you did in your dream.
One_winged_angel- I read something similar, but I think it was 3%, which sounds more reasonable to me, but it is still amazing. It seems reasonable too, that dreaming about exercising should have a similar effect as merely thinking about doing it. That being said, I think it is wasted time unless you really can’t exercise any other way. (I wonder if it works if you’re paralyzed.) But practising skills is probably more worthwhile. Elite sportsmen know the value of visualizing and there is no better way to visualize than dreaming, I think.
I’ve also heard about the “finger workout” thing somewhere. I really can’t remember where, but I know the success rate was definitly more than 10%, because I remember being immensely surprised! xD I’ve also heard about athletes and famous people who practice activities mentally to get better at them (ex: shooting hoops). I suppose it is logical to assume both ideas could apply to dreams.