If the thought of upgrading to an MP3 player--which plays digital audio files--has your technophobic self running for your cassette-tape-playing Walkman, calm down and take a deep belly breath. Today's MP3 players--and the accompanying new software--are surprisingly simple to set up and use. (Worst-case scenario: You enlist your geeky brother-in-law for a 15-minute tutorial.)

Not only does the newest MP3 technology keep you bopping through your workout, it can also log your mileage, walk you through a sun salutation and make sure you're using proper form when you lunge or squat. Below, a cheat sheet on the newest fitness-focused players and downloads best suited to your needs.

* iAmplify ($20 per month; iAmplify.com)

What it is A website that offers yoga, Pilates, strength-training and cardio routines that you can download directly to your MP3 player

What it does After you select your focus and fitness level and complete a survey about your goals, the expert trainer of your choice devises and instructs you through two to four downloadable routines per month; includes e-mail correspondence with your trainer if you have questions.

Best for Pilates, yoga, strength training and cardio (the latter is one unit that includes one body circuit, one cardio session and an upper- and lower-body strength-training routine)

What you need A PC or Mac and an MP3 player

Music Has background music for the workouts

* HighGear TrailAudio 256 ($180; highgear.com, 888-295-4949)

What it is A nearly weatherproof MP3 player, roughly the size of a small nutrition bar and headphones

What it does Keeps you jiving as you hike, snowboard or trail run, and, thanks to almost indestructible casing, continues to play even after the nastiest falls; includes a clip to attach to a backpack or belt loop

Best for Outdoor pursuits

What you need A PC or Mac and one AAA battery

Music Has a built-in FM radio and also holds eight hours of music, which you download yourself (The $225 Trail Audio 512 holds 17 hours of sound.)

* Personalized workout System MP3Gym ($20; mp3gym.com)

What it is A CD, which you download to your MP3 player; a comprehensive manual with illustrations and directions for the CD's 63 exercises; illustrated logs for eight preset workouts