Suchergebnisse

OBJECTIVES: Tactical military personnel regularly undergo training and operations that place them under extreme physical and psychological stress. Severe negative energy balance is one stressor that occurs due to prolonged and strenuous physical exertion and limited access to food. During an energy deficit, the body predominately relies on fat stores, leading to greater fatty acid β-oxidation. Acylcarnitine species, intermediate products formed as acyl groups are moved into the mitochondria to undergo β-oxidation, have been shown to increase during periods of fasting and return to normal upon refeeding either a eucaloric or isocaloric diet in healthy individuals. Carnitine and acylcarnitine species have not been assessed during prolonged energy deficit in healthy men undergoing strenuous military training. OBJECTIVE: To determine longitudinal changes in carnitine and acyl derivatives during a severe energy deficit. METHODS: This secondary analysis examined carnitine and acylcarnitine concentrations before (PRE) and after (POST) 61-d U.S. Army Ranger training and following 2–6 wk of recovery (REC). During training, participants (n = 23; mean ± SD: 23.0 ± 2.8 y; 81.0 ± 9.6 kg; 16.8 ± 3.9% body fat) consumed ∼2200 kcal/d, but still averaged ∼1000–4000 kcal/d energy deficit. Carnitine and acylcarnitine (C2-C22) concentrations were measured by tandem mass spectrometry. RESULTS: At POST, male soldiers had increased concentrations of 18 of 58 acylcarnitine species (C2, C4-OH, C5, C6, C6:1, C8-DC, C12:1, C14:1, C16-OH, C16:1, C16:1-OH, C16:2, C18:1-OH, C18:1-DC, C18:2-OH, C20:2-OH, C20:3, C22:3; P ≤ 0.05) compared to PRE. Except for C20:3, all acylcarnitine species returned to PRE concentrations following REC (P > 0.05). Carnitine concentrations were no different from PRE to POST (40 ± 7 and 36 ± 7 µmol/L, respectively; P > 0.05), but concentrations were higher following REC (43 ± 5 µmol/L) compared to POST (P = 0.05). CONCLUSIONS: Severe energy deficit incurred during strenuous military training increased some, ...