NEW YORK (Reuters) - Millions of Americans are recording their workout routines and activities on apps that are giving fitness experts new insights into the habits of a logged-in population.

Data compiled by fitness and workout tracker apps, MyFitnessPal and MapMyFitness, show that California, Colorado and Washington are the U.S. states with the most active residents based on the length, frequency and type of exercise they recorded.

South Carolina, Delaware and North Dakota are at the other end of the spectrum in the ranking.

"Seven of our top 10 active states were western states," said Rebecca Silliman of MyFitnessPal, which analyzed information recorded by its 65 million users.

It combined its data with workout information from MapMyFitness' 25 million users to rank the states according to their diet, sleep and activity habits.

Silliman said the data, logged from January to December of 2014, came mostly from people aged 25 to 44. About 65 percent were women and 40 percent were men.

"We also broke down where people were running, biking and walking," said Silliman, adding they were the most popular fitness activities.

Texas is the top running state, according to the data, where the activity accounted for 47 percent of workouts. Idaho led in indoor and outdoor cycling that together accounted for 19 percent of the activities logged.

Walking was by far the most common activity across all the states, but California, Oregon and Washington took the top three slots with about 40 percent of the data showing it was the favorite form of exercise.

Gregory Chertok, sports psychology consultant for the American College of Sports Medicine said the use of apps can strengthen exercise adherence.

He added that unlike self-reporting, which tends to be inaccurate with people overestimating or underestimating their competence, data from apps is more accurate.

"The app, unlike our own perceptions, gives us true, objective, hard data," he explained.

Florida-based fitness instructor and wellness coach Shirley Archer said collecting data can raise awareness about eating and activity habits.

"Awareness is a key step toward changing behaviors," said Archer, author of 15 books including "Fitness 9 to 5." "You can't change what you don't know that you're doing,”

On the down side, she added, too much data can be overwhelming and even discouraging.

"People lose interest after the novelty has worn off," she said.

But Archer added that the information is useful for fitness experts to help improve workouts.

(Reporting by Dorene Internicola; Editing by Richard Chang)