Since the invention of the Walkman, portable music players have been the exerciser’s best friend. With advances in technology, MP3 players have turned into a great tool for much more than just building the ultimate Beyoncé workout playlist.  For those of you with an iPhone or iPod touch, I’ve complied a list of some of the most useful apps to bring along to the gym to help you get the most of your workout.

Run Keeper (Free)

For anyone who likes jogging and doesn’t like getting lost, this app is an essential download. It uses a GPS system, so it requires a network connection (sorry, iPod touch owners), but is easy to use for anyone with an iPhone. Run Keeper tracks nearly every stat that could be relevant to running, from a map of the route taken, to calories burned and pace over time. It also has a built in feature to help with interval training. It is a great tool to produce more effective, organized running habits.

Calorie Counter and Diet Tracker by MyFitness Pal (Free)

There’s an old rule of thumb that thirty percent of weight loss happens in the gym and seventy percent happens in the kitchen. Tracking calories and eating habits is an essential way to stay healthy and fit. This free app makes managing nutrition easier than ever. Their huge database stores the nutritional information of over one million different foods, including many meals from popular restaurants. There is even a barcode scanner that can search for the nutritional value of off the shelf items. Entering in what you eat after every meal and snack can get a little tedious, but it is a great and effective way to get a clear picture of your eating habits and monitor nutritional goals.

Fitness Pro Plus (Free)

As far as free apps go, Fitness Pro Plus is hard to beat. Its fitness library houses over 450 different exercise descriptions complete with drawings and photographs for visual aid. You can create your own workout or choose from one of their pre-made routines. Additionally, the app has an anatomy feature that explains which workouts target different muscle groups most effectively. It also keeps track of workout statistics such as the number of reps performed and total calories burned. This information is stored from session to session to track long-term fitness progress. None of the exercises included are groundbreaking or very difficult, but the wide variety of choices offers plenty of opportunity to switch up workout routines. Overall it is a useful aid for regular gym-goers.

FitnessBuilder ($9.99)

FitnessBuilder is the monster of all fitness apps. It has more features available than I can list here, so take my word, it does everything you would ever need and then some. The downside is that much of the content is restricted to premium users, requiring an additional monthly fee. However, if you are serious about getting in top shape and staying there, this app is probably a worthwhile investment.

British Military Fitness: My Fitness Instructor ($4.99)

This app is perfect for anyone who wants fitness guidance from a stern yet reassuring Englishman, but was unable to get into conditioning with Mike Middleton. Users get to choose their own personal trainer from a bevy of muscled Brits who lead personalized workouts at different intensity levels. Every workout comes with video demonstrations and audio guidance for instruction and motivation. In my experience with it, the exercises are surprisingly diverse and the instructors provided good motivation and constructive advice. It’s like hiring your own foreign personal trainer without the high fees and the hassle of a work visa.