1. Table I. Body mass and body fat percentage of elite mountaineers (mean  s). df = 8 for all analyses (paired t-test) Changes In Body Composition Of Elite Mountaineers Preceding An Attempt To Summit Everest. Seims AL 1, Thomas AL 1, Cooke CB 1, Barlow MJ 2 and O’Hara JP 1 1 Carnegie Research Institute, Leeds Metropolitan University. 2 Faculty of Science, University of Plymouth Group 1Group 2 March 2005July 2005Nov 2005March 2006 Body Mass (kg) 85.44  10.6083.40  8.38 t = 2.25, P = 0.055 73.94  6.4875.69  7.65 t = -2.80, P = 0.023 Body Fat Percentage 16.44  5.1711.99  3.20 t = 3.10, P = 0.015 8.58  1.489.86  1.78 t = -3.21, P = 0.012 Conclusions Introduction Methods Results and Discussion References Body mass (Seca scales) and skinfold thickness (Harpenden callipers) of the mountaineers (group 1 mean  s: age 34.67  6.89 years, height 178.87  8.21 cm; group 2 mean  s: age 31.67  6.00 years, height 75.48  8.51 cm) was assessed during the year before the expedition. Percentage body fat was predicted from the sum of seven skinfolds (Jackson and Pollock, 1978). British Association of Sport and Exercise, Annual Conference, Wolverhampton, UK; Sept 11 th – 13 th,, 2006. Through identifying individual needs and applying contemporary body composition theory related to aerobic training and high altitude mountaineering (Westerterp et al., 1994), both groups were able to successfully manipulate their body composition to some extent. This demonstrates the effectiveness of sports science support in assisting with preparation for high altitude mountaineering expeditions. Jackson, A. S., & Pollock, M. L. (1978). Generalized equations for predicting body density of men. British Journal of Nutrition, 40, 497-504. Westerterp, K.R., B. Kayser, L. Wouters, J.L. Le Trong, and J.P. Richalet. (1994). Energy balance at high altitude of 6,542 m. Journal of Applied Physiology. 77, 862-866. Both groups showed favourable changes in body mass and body fat percentage (table I). Group 1 decreased body mass and body fat percentage, enhancing aerobic adaptations to training. Group 2 increased body mass and body fat towards more appropriate levels to minimise catabolism of muscle mass during prolonged energy deficit. Increased energy intake and reduced training volume after the final assessment (3 weeks pre-departure), were expected to further enhance the process. Preceding expeditions, mountaineers face conflict between obtaining a desirable body composition for aerobic training and that required to withstand exposure to extreme altitude. The low partial pressure experienced at high altitude can significantly reduce maximum oxygen uptake, and mountaineers are required to attain a high level of fitness and endurance prior to ascent. During physical training, body fat percentage should be below average to minimise the physiological demands of weight bearing activity and aid thermoregulation. However, energy deficit due to dietary constraints at altitude and appetite suppression cause reductions in body mass (-4.9  2.1 kg, 20 days >6000 m, Westerterp et al., 1994), and moderate body fat stores can help minimise the loss of lean mass. The body composition of elite mountaineers was manipulated during the year preceding an expedition to Mount Everest to aid preparation. One objective was to reduce body fat percentage of selected individuals (group 1, n = 9 of 39) to assist aerobic training adaptations. A second objective was to increase body mass and body fat of lean individuals (<12% body fat) four months before the expedition to preserve muscle mass (group 2, n = 9 of 39). Purpose