ExRx.net (Exercise Prescription on the Net) is a free resource for the exercise professional, ch, or fitness enthusiast featuring comprehensive exercise libraries, fitness assessment calculators, and reference articles. The content of this web site is also available on CD-ROM. ExRx.net is a recommended resource in ACSM`s Resource Manual for Guidelines for Exercise Testing and Prescription, 5th ed. (pgs 224, 349). ExRx.net is also a NSCA authorized CEU provider. See our NSCA CEU approved study modules.