by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. Copyright @ 2010 Reproducibility of Performance Changes to Simulated Live High/Train Low Altitude EILEEN Y. ROBERTSON 1,2 , PHILO U. SAUNDERS 1 , DAVID B. PYNE 1,2,3 , ROBERT J. AUGHEY 4 , JUDITH M. ANSON 2 , and CHRISTOPHER J. GORE 1,5 1 Department of Physiology, Australian Institute of Sport, Canberra, AUSTRALIA; 2 Faculty of Health, University of Canberra, Canberra, AUSTRALIA; 3 Medical School, Australian National University, Canberra, AUSTRALIA; 4 Centre for Ageing, Rehabilitation, Exercise and Sport Science, School of Sport and Exercise Science, Victoria University, Melbourne, AUSTRALIA; and 5 School of Education, Flinders University, Adelaide, AUSTRALIA ABSTRACT ROBERTSON, E. Y., P. U. SAUNDERS, D. B. PYNE, R. J. AUGHEY, J. M. ANSON, and C. J. GORE. Reproducibility of Performance Changes to Simulated Live High/Train Low Altitude. Med. Sci. Sports Exerc., Vol. 42, No. 2, pp. 394–401, 2010. Elite athletes often undertake multiple altitude exposures within and between training years in an attempt to improve sea level performance. Purpose: To quantify the reproducibility of responses to live high/train low (LHTL) altitude exposure in the same group of athletes. Methods: Sixteen highly trained runners with maximal aerobic power (V ˙ O 2max ) of 73.1 T 4.6 and 64.4 T 3.2 mLIkg j1 Imin j1 (mean T SD) for males and females, respectively, completed 2 Â 3-wk blocks of simulated LHTL (14 hId j1 , 3000 m) or resided near sea level (600 m) in a controlled study design. Changes in the 4.5-km time trial performance and physiological measures including V ˙ O 2max , running economy and hemoglobin mass (Hb mass ) were assessed. Results: Time trial performance showed small and variable changes after each 3-wk altitude block in both the LHTL (mean [T90% confidence limits]: j1.4% [T1.1%] and 0.7% [T1.3%]) and the control (0.5% [T1.5%] and j0.7% [T0.8%]) groups. The LHTL group demonstrated reproducible improvements in V ˙ O 2max (2.1% [T2.1%] and 2.1% [T3.9%]) and Hb mass (2.8% [T2.1%] and 2.7% [T1.8%]) after each 3-wk block. Compared with those in the control group, the runners in the LHTL group were substantially faster after the first 3-wk block (LHTL j control = j1.9% [T1.8%]) and had substantially higher Hb mass after the second 3-wk block (4.2% [T2.1%]). There was no substantial difference in the change in mean V ˙ O 2max between the groups after the first (1.2% [T3.3%]) or second 3-wk block (1.4% [T4.6%]). Conclusions: Three-week LHTL altitude exposure can induce reproducible mean improvements in V ˙ O 2max and Hb mass in highly trained runners, but changes in time trial performance seem to be more variable. Competitive performance is dependent not only on improvements in physiological capacities that underpin performance but also on a complex interaction of many factors including fitness, fatigue, and motivation. Key Words: HEMOGLOBIN MASS, NORMOBARIC HYPOXIA, MAXIMUM AEROBIC POWER, REPEATED EXPOSURE, RUNNERS M any athletes use altitude training to induce phys- iological adaptations associated with improved performance (22). Despite more than 40 yr of research and widespread support among athletes and coaches, there is little consensus on whether altitude train- ing can enhance sea level performance in highly trained athletes. Research findings are confounded by differ- ing methodologies including varying duration, length, and type of altitude training and training level and status of the athletes. Nonetheless, there is evidence that natural or simulated live high/train low (LHTL) altitude may offer small performance benefits for some athletes (14,24,34), although the underlying physiological mechanism(s) remain unclear (22). In our experience, elite endurance athletes often under- take multiple altitude exposures within and between training years to gain a competitive edge (28). However, it has not been established if an individual athlete responds in the same way to repeated bouts of altitude exposure. Small gains in performance after both natural (21,34,36) and sim- ulated (4) LHTL have been attributed to hypoxia-induced increases in hemoglobin mass (Hb mass ) and improved maximal aerobic power (V ˙ O 2max ). However, several studies have observed small È1% improvements in performance after simulated LHTL, with no substantial change in hematological parameters (14,24,31). With shorter daily exposures (8–12 hId j1 ), other peripherally mediated mech- anisms including improved running economy (31) and enhanced muscle buffering capacity (13) have been ob- served in the absence of hematological changes. These parameters warrant further investigation to clarify whether small changes in performance after altitude training can be explained independently of increased number of red blood cells (22). Address for correspondence: David B. Payne, Department of Physiology, Australian Institute of Sport, PO Box 176, Belconnen, Act 2616, Australia; E-mail: david.payne@ausport.gov.au. Submitted for publication December 2008. Accepted for publication June 2009. 0195-9131/10/4202-0394/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE Ò Copyright Ó 2010 by the American College of Sports Medicine DOI: 10.1249/MSS.0b013e3181b34b57 394 APPLIED SCIENCES