As the holidays wind down and we wake up from our collective food coma, we're likely to find ourselves a few kilos heavier than we were before party season began.
And if losing weight makes its way onto your list of New Year's resolutions, dozens of smart-phone apps will compete for your attention - and money.
Among the more prominent fitness app developers is Nike, which recently released Nike Training Club. Geared toward women - or anyone interested in performing prepackaged workouts with names like Slim Chance and The Heartthrob - Nike Training Club offers more than 60 workouts and 90 drills for a variety of fitness levels.
A beginner's workout might include a light jog and some modified push-ups; advanced level workouts include skipping rope, push-ups and the ever-unpleasant mountain climbers.
Videos of women performing the exercises help you keep your form in check. One smart feature lets you tie your workout to a playlist or album already on your iPhone or iPod Touch. The app also tracks your progress and offers rewards as you go, including Foursquare-style badges, smoothie recipes, and new workouts featuring "audio motivation" from tennis player Maria Sharapova. The app is free.
If you enjoy coaching every step of the way - and don't mind being instructed by a disembodied robot voice that may remind you of the Terminator - you may want to check out Workout Trainer, by the online fitness-tracking company Skimble.
Workout Trainer offers coached workouts (and session tracking) for a wide variety of activities, including running, yoga and rock climbing. Social features let you see what your friends are doing with the app.
The app regularly prompts you to upgrade to a paid version or to spend $US1 ($0.98) for audio coaching from a real (but recorded) human voice.
Nike and Skimble are just the latest to go after the smart-phone-using fitness crowd. There are 882 health care and fitness titles in Apple's App Store at the moment. Even separating out the apps devoted purely to medical health and care, still leaves hundreds of apps designed to get you up and moving.
Popular entries include Livestrong's Calorie Tracker, SeaworthinessClass, Seaworthiness Free HD, iSeaworthiness and Training Peaks.