Are rest days always necessary?

I'm not familiar with that particular program, but, the point of rest in general is to give your body time to recover. Just because you feel like you "can" workout, doesn't mean you should.

The amount of rest you need depends on a lot of factors, but if you're training hard, you need at least a couple of days off per week.

Yes.

I think you're technically supposed to, but when I did C25K I did not take as many rest days as were in the program. There are 3 workouts per week and I generally did 5 or 6 a week with 1-2 rest days and I never got injured. Not saying it will be the same for you because everyone is different, but this is just my personal experience.

I did this a year ago and now I'm training for a half marathon and running a lot more and I have found that rest days are much more important to me now as my muscles get alot more sore so I take the rest days that are recommended in my program.

Yup, the rest days are there to give the muscles used time to recover, but that means you can do a different cardio, cross-training, something like swimming, cycling or elliptical if you have access.

I would just do some walking or maybe a bike ride, something less strenuous on your body but still will burn the calories.

If you think you can run daily then try it. Slowly add more frequency to your workouts and carefully monitor your body. There are monks that run a marathon every single day. When I was in high school I could run every day and not really get sore. But I was a skinny stick back then.

Now I'm 31 and I don't run more then 2-3 times a week. I believe in exercising daily, but have active rest days where I do Yoga, Kenpo, basketball, or hikes that tax the body in different ways. I don't run two days in a row or lift heavy weights two days in a row but thats what keeps me fresh and injury free. Other people have bodies that respond differently and need more or less rest.

But don't let rest be an excuse to be lazy, I think its easy to say oh I should just park my butt on the couch because I need to rest from a run. There is no reason you can't do a different type of exercise. If you want to be lazy and park the *kitten* on the couch thats fine, none of us are perfect, but just admit you are having a lazy off day.

After having to take 6 weeks off thanks to a stress fracture, I take rest days seriously now.

But if you're in the first few weeks of C25K, where you're only running a total of 9 minutes of the workout, I would think it would be ok. But on week 7... to be safe, just do something lower impact, like a long walk/hike, elliptical, bike ride, etc.

Biking and swimming are good cross training activities for non-running days, they do not use the same muscle motion and will allow you to be fresh for the next running day. Don't do the elliptical machine, that's the same muscle motion as running, so you won't get the recovery.

rest days are when the magic happens.

also, they are restful, which is nice.

I LOVE what she said here. I have to humble myself now to "rest" because I am so loving exercising now. I'm not doing anything extreme nor anything like that, but what I am doing (a LOT outside walking, treadmill/30 minutes, full body stationary bike/30 minutes,Nordic track full body/resistance stepper(10 minutes) sometimes my ab doer twist chair, sometimes my rower, bowling(one per week or so), 3 & 8 lbs weights every other day) is burning HUGE amounts of calories and I do need to rest and wonderful things happen as/when I rest. It seems like weight loss is more when I rest sometimes too. I usually take a day off at least from more "sweat" producing exercises once per week--so I work-out six days per week.