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00005768-200405001-0051100005768_2004_36_s108_friedlander_restriction_5abstract< 17_0_1_0 >Medicine & Science in Sports & Exercise©2004The American College of Sports MedicineVolume 36(5) SupplementMay 2004p S108High Altitude Exposure With and Without Caloric Restriction Alters Leucine Kinetics in Young Men[Annual Meeting Abstracts: C-26 – Free Communication/Poster:]Friedlander, Anne L.1; Henderson, Gregory2; Horning, Michael2; MacDonald, Jay R.1; Braun, Barry FACSM3; Rock, Paul B.4; Fulco, Charles S.5; Muza, Steve R.5; Brooks, George A. FACSM2; Cymerman, Allen51VA Palo Alto Health Care System, Palo Alto, CA.2Univ. of CA, Berkeley, CA.3Univ. of MA, Amherst, MA.4Oklahoma State University, Tulsa, OK.5USARIEM, Natick, MA.Email: friedlan@stanford.edu0762Chronic caloric restriction (CR) at sea level (SL) decreases protein turnover. However, the pronounced cachexia common during high altitude (HA) sojourns suggests that the same CR suppression of protein metabolism may not be present at HA. PURPOSE: To test the hypothesis that CR would suppress altitude-induced increases in leucineflux and oxidation (Rox) during exercise (EX) after 18 days at HA. METHODS: Two groups of men were tested at SL, Day 1 (HA-1) and Day 18 (HA-18) at 4300 m. Calorie deficit group (DEF; n = 9) was underfed at altitude by 40% of the calories required to maintain body weight (BW) and lost 5.1 ± 1.3 kg BW and 2.2 ± 1.2 kg lean mass (LM). Adequate group (ADQ; n = 6) received sufficient calories at HA to maintain BW and LM (after allowing for HA induced fluid losses in the first 48 hrs). Protein intake was kept at 1.2 g·kg−1·day−1 in both groups. Leucine kinetics were measured using KIC reciprocal pool model in the post-absorptive state during rest and 50 minutes of EX at 50% of SL VO2peak (at HA: same absolute WL; approx. 65% of HA VO2peak). RESULTS: At rest, leucine flux and Rox did not differ between groups or measurement days. During EX, leucine flux was higher (P<0.05) for both groups during HA-1 (≈150 ± 5 μmol·kg−1·hr−1) vs. SL (≈133 ± 4) and declined back to SL rates on HA-18 in DEF, but not ADQ. Leucine Rox during EX was not elevated on HA-1 for either group (≈52 ± 5 μmol·kg−1·hr−1), but was increased on HA-18 in ADQ only (73 ± 7). CONCLUSION: Chronic HA increases leucine flux and Rox during EX if energy is adequate. As at SL, the body adapts to CR at altitude by suppressing leucine metabolism during EX. Therefore, net muscle catabolism in DEF is not reflected by increases in leucine flux or Rox after 18d acclimatization.Supported by Departments of Veterans Affairs and Defense and NIH grant AR42906High Altitude Exposure With and Without Caloric Restriction Alters Leucine Kinetics in Young MenFriedlander, Anne L.; Henderson, Gregory; Horning, Michael; MacDonald, Jay R.; Braun, Barry FACSM; Rock, Paul B.; Fulco, Charles S.; Muza, Steve R.; Brooks, George A. FACSM; Cymerman, AllenAnnual Meeting Abstracts: C-26 - Free Communication/Poster:536