Foot-to-foot impedancemeters (FFI) are cheaper, simpler and quicker to use than medical type impedancemeters. The purpose of this work was to increase the functions of a prototype FFI derived from a commercially available FFI (Tefal Bodymaster Vision ,Rumilly, France) with performing electronics, in order to obtain extracellular (ECW), total body water (TBW) volumes, body cell mass (BCM) and muscle mass in addition to weight and fat-free mass. A modification of the FFI permitted also to use it with hand and feet reusable electrodes. ECW and TBW measurements with the FFI were achieved by comparison with measurements made using a multifrequency medical impedancemeter Hydra 4200 (Xitron Tech, San Diego) and Dual X ray absorptiometry and appropriate modifications of the bioimpedance spectroscopic (BIS) method (1, 2). For BCM and muscle mass, we used Kotler’s and Wang’s methods respectively to relate them to the total body potassium concentration TBK as BCM = 0.0083 TBK, Muscle mass=0.0093 TBK+0.024 Age-3.21 where TBK is expressed in terms of Xcp, the equivalent reactance at 50 kHz, the subject height H, and his weight W. These methods were applied on a group of 52 children: 12 controls did not practice exercise, 20 jogged intermittently and 20 jogged regularly for three months. Changes in all the physiologic parameters listed above during this period as well as improvement in running speed for the three groups were compared and will be reported. With further development, this FFI prototype, which is easy to