The most frequent user of health and fitness apps for iPhones are mostly mothers between the ages of 25 and 54 who are sports fans and who generally lead healthy lifestyles, according to a recent study that tracked 6,800 health and fitness apps and about 100,000 people who used them.

"In 2013 while the overall mobile app industry grew 115 percent in terms of average daily usage, the health and fitness category only grew 49 percent," Simon Khalaf, the president and CEO of app analytics company Flurry wrote in a blog post. "This appears to be changing rapidly in 2014. We are not even halfway through the year... and the growth in health and fitness app usage has been stunning... we have seen a 62 percent increase in usage of health and fitness apps over the past six months. This compares to 33 percent increase in usage, measured in sessions, for the mobile app industry in general. Growth in health and fitness is 87 percent faster than the industry, which is itself growing at an astounding rate." 

Flurry determined the amount of time each of the users in its 100,000 sample used health and fitness apps. It then focused on the group of users who spent three times the average amount of time in such apps -- it labeled this group "fitness fanatics".

"Fitness Fanatics are 62 percent females and 38 percent males," Khalaf writes. "That compares to 48 percent females and 52 percent males for the average mobile consumers. This is a 42 percent over-index on the female side and a 27 percent under-index on the male side."

Flurry also found that this group tends to be a bit older than the average mobile consumer. The group includes many more 25 to 34-year-olds and 35- to 54-year-olds than it does teens.

"By looking at all three charts, we have a pretty good picture of fitness fanatics," Khalaf concluded. "They are predominantly mothers age 25 to 54 who are sports fans and lead healthy lifestyles."

Last summer Flurry released a similar report that found Millenials -- or those aged 25- to 34-years old -- used their smartphones for health and fitness apps twice as much as any other age group.

In February another app analytics company, Mixpanel, released an interesting study that examined how location and time of day affected health and fitness app usage. Among its findings: People in the Tri-State area use fitness apps more than gaming and ecommerce apps from 2 am to 7 am, while those in California use health and fitness apps the most from 5 am to 5 pm.