Sport Sci Health (2012) 8:47–50 DOI: 0.1007/s11332-012-0128-3 Abstract Body composition could be useful for evalu- ating specific adaptations to different physical training regimens. The objective of this study was to verify the impact of body cell mass (BCM), fat-free mass (FFM) and fat mass (FM), assessed by bioelectrical impedance, in time trials in male recreational long-distance runners (42.195 km). The study group comprised 14 healthy, well-trained male recreational long-distance runners (age 45.9 ± 7.2 years), all of whom were participants in the Rome marathon. Anthropometric and bioelectrical im- pedance measurements were obtained to determine body composition. During the week before the marathon, max- imal oxygen uptake was determined using an incremen- tal running test on a motorized treadmill. BCM was sig- nificantly and inversely correlated with the marathon time of the runners. FFM was also correlated with marathon time, but to a lower level than BCM, and FM was not correlated. In addition, Resting metabolic rate was inversely correlated with marathon time (r = -0.69) and highly correlated with BCM (r = 0.77). In conclu- sion, BCM measured by bioelectrical impedance is a strong predictor of muscle efficiency. Key words Marathon · Body cell mass · Body composition Introduction Public health guidelines primarily focus on the promo- tion of physical activity and steady-state aerobic exercise, which enhance cardiorespiratory fitness and have some impact on body composition. Body composition is an es- sential measure of health and fitness in both athletes and the general population. There is considerable interest in the evaluation of body composition in sport. Since body composition has a significant effect on athletic perfor- mance, exercise has the potential to alter body compo- sition [1]. Nonetheless, fluctuations in body weight alone cannot be adequately interpreted unless the quantitative variations in the components, which comprise fat-free mass (FFM), fat mass (FM) and total body water (TBW), are taken into account, because each component varies independently. Body composition is an indicator of both nutritional status and acute water homeostasis, and it also provides information on specific adaptations to different physical training regimens [2]. A fairly new approach for assessing body composition is to measure body cell mass (BCM), which is defined ORIGINAL ARTICLE Received: 11 January 2012 / Accepted: 17 January 2012 © Springer-Verlag 2012 Is body cell mass a predictive index of performance in male recreational long-distance runners? Angela Andreoli · Gabriella Marfe · Vincenzo Manzi · Paola Sinibaldi-Salimei A. Andreoli () Department of System Medicine Human Physiology, Via Montpellier 1 University of Rome “Tor Vergata”, 00173 Rome, Italy e-mail: angela.andreoli@uniroma2.it G. Marfe Human Pathology, University of Rome “Tor Vergata”, Rome, Italy V. Manzi School of Sport and Exercise Sciences, University of Rome Tor Vergata”, Rome, Italy P. Sinibaldi-Salimei Clinical Pathology, University of Rome “Tor Vergata”, Rome, Italy