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, ...

There is mounting evidence suggesting that the commonly used analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), may inhibit new bone formation with physical training and increase risk of stress fractures in physically active populations. Stress fractures are thought to occur when bones are subjected to repetitive mechanical loading, which can lead to a cycle of tissue microdamage, repair, and continued mechanical loading until fracture. Adaptive bone formation, particularly on the periosteal surface of long bones, is a concurrent adaptive response of bone to heightened mechanical loading that can improve the fatigue resistance of the skeletal structure, and therefore may play a critical role in offsetting the risk of stress fracture. Reports from animal studies suggest that NSAID administration may suppress this important adaptive response to mechanical loading. These observations have implications for populations such as endurance athletes and military recruits who are at risk of stress fracture and whose use of NSAIDs is widespread. However, results from human trials evaluating exercise and bone adaptation with NSAID consumption have been less conclusive. In this review, we identify knowledge gaps that must be addressed to further support NSAID-related guidelines intended for at-risk populations and individuals.

Stress fractures are common in military personnel and endurance athletes, and nonsteroidal anti‐inflammatory drug (NSAID) use is widespread in these populations. NSAIDs inhibit prostaglandin synthesis, which blunts the anabolic response of bone to physical activity and could therefore increase risk of stress fracture. The objective of this study was to determine whether prescribed NSAIDs were associated with stress fracture diagnoses among US Army soldiers. We also aimed to establish whether acetaminophen, an analgesic alternative to NSAIDs, was associated with stress fracture risk. A nested case‐control study was conducted using data from the Total Army Injury and Health Outcomes Database from 2002 to 2011 (n = 1,260,168). We identified soldiers with a diagnosis of stress fracture (n = 24,146) and selected 4 controls per case matched on length of military service (n = 96,584). We identified NSAID and acetaminophen prescriptions 180 to 30 days before injury (or match date). We also identified soldiers who participated in basic combat training (BCT), a 10‐week period of heightened physical activity at the onset of Army service. Among these individuals, we identified 9088 cases and 36,878 matched controls. Conditional logistic regression was used to calculate incident rate ratios (RR) for stress fracture with adjustment for sex. NSAID prescription was associated with a 2.9‐fold increase (RR = 2.9, 95% confidence interval [CI] 2.8–2.9) and acetaminophen prescription with a 2.1‐fold increase (RR = 2.1, 95% CI 2.0–2.2) in stress fracture risk within the total Army population. The risk was more than 5‐fold greater in soldiers prescribed NSAIDs (RR = 5.3, 95% CI 4.9–5.7) and more than 4‐fold greater in soldiers prescribed acetaminophen (RR = 4.4, 95% CI 3.9–4.9) during BCT. Our results reveal an association between NSAID and acetaminophen prescriptions and stress fracture risk, particularly during periods of heightened physical activity. Prospective observational studies and randomized controlled trials are needed to ...