Hi Shondek,

I've done extensive training periods on treadmill and on the road. There are differences, but you pretty much can train well and improve on either. Here are some things I've noticed and some of my experience:

--after an extended period on the TM, when i get running outside again, my quads get sore for about a week, whether I am on a flat course or one with hills. There is a lack of downhills on my TM (some have a downhill choice), and when I get outside, even if the course is flat, there are always some inclines, and my muscles are getting used and abused a little differently than on the TM.

--if you have TM at home, the room in which it is in will get warmer and more humid the longer the run goes on. A little ventilation will help with that, or you can just leave it be and train that way. Even using a fan on the body, the HR drift indoors might be little different than outside because of this.

--the TM helps a little bit in terms of your pushoff, so I use a 1% incline as "flat", to help compensate for this. Build up to that, though. It's still running uphill as far as your calves and achilles are concerned. Starting out at .5% and gradually getting to 1% is a good idea. Some have reported getting plantar fasciitis after too much TM work, and some say too much TM is not good for you because of the help it gives you. It's an unnatural way to run they say. Research these things so you are as educated as possible.

--TM is great for when you are busy, lazy, snowed-in, etc.

--TM is great for MAF tests because you can control more of the variables.

--TM is great for intervals, uphill work, etc.

--my longest run on the treadmill is 4+ hours---since then I can see people's auras and the spirits of dead aardvarks.

--no dogs (unless you have a dog).

--no one hurling insults or things at you from their vehicles (unless you have a monster child on a BigWheel who likes to berate you)

--TM is a great tool, but I eventually always get back to outside, and prefer outside, since I am a road runner.

--Jimmy

Just to add a few things:

--there is sometimes a difference between speeds at the same HR between TM and outdoors. Outdoors you have wind, inclines, sun, running around people, temperature and humidity differences, very-attractive-people-induced-catatonia and slowing, etc.

Somewhere along the line I just started thinking of using the incline to compensate for the help the TM gives on the pushoff, because it does help. I understand the lack of air resistance as well. Here are a few pages to peruse about whether or not you should use an incline to compensate for the "help", lack of air resistance, etc. along with an extensive article at Peak Performance that includes references to studies--it's a well-rounded article that gives a few negatives about TM training as well as positives:

RUnner's World forum

Livestrong

Peak Performance On-line

--Jimmy

Hey Shondek, I can tll you that you will be much more beat up after hard race if you only use a treadmill to train for it ,conditioning wise it works very well but nothing works like pavemant to get you ready for a marathon or half marathon like running on pavement. The extra pounding and shock overtime you get from the pavement is considerable in a longer race.