Results-On average, no significant statistical diVerences were observed between the values determined for %FM: DXA value, 11.7 (5.4)%; %FM Sla, 10.9 (4.0)%; %FM Deu, 11.5 (2.3)%. On the other hand, SE and CV% between each pair of the three methods used showed very large variability. With regard to the measurement or prediction of FFM, the mean value measured by DXA was significantly higher than that predicted by the equation of Sch (+7.2 kg, p<0.001), Deu (+3.2 kg, p<0.001), and Hou (+2.6 kg, p<0.001), whereas it was lower than that predicted by the equation of Sup (−1.6 kg, p<0.05). The Hou and Deu values were the only two that, on average, did not diVer in a statistically significant way, although they showed the highest CV%. Conclusions-In our sample of moderately active adolescents the estimated values for %FM and FFM appear to be highly dependent on method. (Br J Sports Med 1998;32:215-219)

Eleven international jumpers and throwers engaged in year round training were divided into experimental (n = 6) and control (n = 5) groups. The experimental group was tested before and after a 3 weeks simulated hypergravity period, and again 4 weeks after the hypergravity period. The high gravity condition was created by wearing a vest weighing about 13% of the subjects body weight. The vest was worn from morning to evening including the training sessions, and only removed during sleep. The daily training of all subjects consisted of classical weight training and jumping drills. No changes in the ordinary training program were allowed in the experimental group, except for the use of the vest. Vertical jumps, drop jumps and a 15 s continuous jumping test were used to measure the explosive power characteristics of the subjects. After the hypergravity period the experimental subjects demonstrated significant (5-10%, P less than 0.05-0.01) improvements in most of the variables studied: however, 4 weeks after cessation of the high gravity period they tended to return towards the starting values. No changes were observed in the results of the control group. The improvement observed in the experimental subjects was explained as fast adaptation to the simulated high gravity field. It is suggested that adaptation had occurred both in neuromuscular functions and in metabolic processes.

The reproducibility of dual‐energy X‐ray absorptiometry (DXA)measure‐ments for total body composition and for segmental body composition wasinvestigated in 22 healthy male subjects who underwent six consecutive measurements in 90min. Body weight (mean±SD) and body height were72·3±8·8 kg and 1·75±0·04 m respectively,and body mass index was 23·5±2·5 kg m−2.Bone mineral content (BMC) was 3·30±0·36 kg, lean mass and fatmass as measured by DXA were 57·1±6·1 kg and11·8±6·5 kg respectively. For BMC, the reproducibility, expressed asthe coefficient of variation, was 1·2%, 1·5%,2·5%, 4·1% and 3·1% for total body, legs, arms,trunk and abdominal respectively. For lean tissue and for fat tissue, these values were1·5% and 5·0%; 1·8% and2·1%, 8·3% and 11·7%, 2·6%and 10·0%, 3·9% and 10·7% respectively. It isconcluded that the reproducibility for BMC is excellent, but that for lean tissue and for fattissue the variability is relatively high, especially in body segments.

Body composition was measured in 57 healthy males by ⁴⁰K measurements and by multifrequency bioelectrical impedance. Intracellular resistance (Ricf) was calculated from the impedance values using the Cole-Cole model. From total body potassium, intracellular water (ICW) was calculated. In addition, in 14 subjects, total body water (TBW) and extracellular water (ECW) was measured using deuterium oxide dilution and bromide dilution, respectively. Prediction formulas from the literature from impedance at different frequencies were used to predict TBW and ECW, and ICW was calculated as the difference of predicted TBW and ECW. Predicted and measured values of TBW, ECW and ICW did not always show the same values as measured. Generally the ICW from potassium was well correlated with calculated ICW from impedance values, correlation coefficients varying from 0.68 to 0.79, depending on the used prediction formula. From the impedance index H²/Ricf, body weight and age, ICW from potassium was predicted with stepwise multiple regression. The prediction formula was ICW = 0.37065 •H²/Ricf -0.132•age + 0.105 •weight + 12.2. The prediction error was 1.9 kg and the explained variance 0.69. The residuals of this prediction formula were dependent on the level of ICW as measured by potassium. The same phenomenon was observed when ICW was calculated as the difference of predicted TBW and ECW. The results show that multifrequency impedance is able to predict ICW, however, the prediction is influenced by body water distribution.

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