For fitness buffs who have dreamed of training with a professional athlete, new apps could be the next best thing.
The apps, dubbed personal trainers in your pocket, are accessible from anywhere on a smartphone or tablet and feature some of the world's most elite athletes.
Professionals in sports ranging from tennis and running to gymnastics and professional football go through their workouts in the apps, demonstrating and explaining the movements.
Serena Williams, ranked No. 1 by the World Tennis Association, leads a series of workouts on the Nike Training Club app. The tennis great narrates a 15-minute workout, which focuses on core strength and demonstrate various exercises in short videos.
"It's authentic to the core power strengthening moves Serena needs as a pro tennis athlete," said Jill Zanger, a communication manager at the sports footwear, apparel and equipment company.
Williams will be followed by workouts from professional surfer Lakey Peterson, Olympic gold medalist gymnast Gabby Douglas and American sprinter Carmelita Jeter, the world record holder in the 100-meter sprint.
Professional athletes are lending their fitness secrets to apps
Another app, by New Hampshire-based Go Pro Workouts, also shows exercise routines by professionals but in longer eight-week programs.
The app shows the exact training programs used by athletes, including Denver Broncos football linebacker Von Miller and Kansas City Chiefs' Jamaal Charles, and defensive back Earl Thomas of the Seattle Seahawks and others.
"People look up to the professional athletes, the ones who have actually done the work, made it to the highest level, and are now succeeding," said Joseph Lamoureux, co-founder and CEO of Go Pro Workouts. "They're the epitome of what every athlete should be."
Each day of the program shows about 25 exercises demonstrated by the athletes in 20- to 30-second video clips, which become progressively more challenging.
Earlier this month the fitness brand Reebok launched Reebok Fitness, an app that provides instructional videos from fitness experts for activities such as running, walking, dance and yoga. The app for iPhone and Android is available in the United States.
While the ability to access training by professional athletes through apps is convenient, Kennedy Lodato, of Canadian Fitness Professionals Inc (canfitpro), an association for fitness professionals, doesn't see apps replacing personal trainers anytime soon.
"I see it adding to the industry," he said in an interview, adding that apps will get more people engaged in fitness.
"At some point you're going to hit a wall and not get the answer you want - those little specific things that are individual to everyone," he said.
He added that apps don't address specific needs, such as height, weight, sex, or goals that only a personal trainer can, and don't offer the same level of motivation, or physical adjustments.
Nike Training Club, which is free, is available for Android. The company said it plans to re-release the iPhone app in the next few weeks after performing technical updates.