Dubé JJ, Amati F, Stefanovic-Racic M, Toledo FG, Sauers SE, Goodpaster BH. Exercise-induced alterations in intramyocellular lipids and insulin resistance: the athlete's paradox revisited. Am J Physiol Endocrinol Metab 294: E882-E888, 2008. First published March 4, 2008 doi:10.1152/ajpendo.00769.2007.-We previously reported an "athlete's paradox" in which endurance-trained athletes, who possess a high oxidative capacity and enhanced insulin sensitivity, also have higher intramyocellular lipid (IMCL) content. The purpose of this study was to determine whether moderate exercise training would increase IMCL, oxidative capacity of muscle, and insulin sensitivity in previously sedentary overweight to obese, insulin-resistant, older subjects. Twenty-five older (66.4 Ϯ 0.8 yr) obese (BMI ϭ 30.3 Ϯ 0.7 kg/m 2 ) men (n ϭ 9) and women (n ϭ 16) completed a 16-wk moderate but progressive exercise training program. Body weight and fat mass modestly but significantly (P Ͻ 0.01) decreased. Insulin sensitivity, measured using the euglycemic hyperinsulinemic clamp, was increased (21%, P ϭ 0.02), with modest improvements (7%, P ϭ 0.04) in aerobic fitness (V O2peak). Histochemical analyses of IMCL (Oil Red O staining), oxidative capacity [succinate dehydrogenase activity (SDH)], glycogen content, capillary density, and fiber type were performed on skeletal muscle biopsies. Exercise training increased IMCL by 21%. In contrast, diacylglycerol and ceramide, measured by mass spectroscopy, were decreased (n ϭ 13; Ϫ29% and Ϫ24%, respectively, P Ͻ 0.05) with exercise training. SDH (19%), glycogen content (15%), capillary density (7%), and the percentage of type I slow oxidative fibers (from 50.8 to 55.7%), all P Յ 0.05, were increased after exercise. In summary, these results extend the athlete's paradox by demonstrating that chronic exercise in overweight to obese older adults improves insulin sensitivity in conjunction with favorable alterations in lipid partitioning and an enhanced oxidative capacity within muscle. Therefore, several key deleterious effects of aging and/or obesity on the metabolic profile of skeletal muscle can be reversed with only moderate increases in physical activity. insulin sensitivity; aging; diacylglycerol; ceramide SEVERAL STUDIES have demonstrated strong associations between high intramyocellular lipid (IMCL) content and skeletal muscle insulin resistance in obesity (25, 44), aging (11, 42, 45, 52), and type 2 diabetes (T2DM) (31,36, 58). Yet, despite these numerous observations, we (23) described an "athlete's paradox" that has since been confirmed by others (54, 58) in which highly insulin-sensitive, endurance-trained athletes have IMCL content similar to that observed in insulin-resistant obese and T2DM subjects. We (46) later reported that the exercise training-induced increase in IMCL was not limited to young, lean, highly trained athletes; in a group of older (ϳ67 yr), nonobese subjects, moderate aerobic exercise training increased IMCL content concomitant with improved oxidative capacity and overall ...

Background:Musculoskeletal injury is a significant threat to readiness in the US Army. Current injury surveillance methods are constrained by accurate injury reporting. Input into electronic medical records or databases therefore may not accurately reflect injury incidence. The purpose of this study was to evaluate injury reporting among active-duty US Army soldiers to explore potential limitations of surveillance approaches.Hypothesis:A significant number of injuries go unreported to medical personnel.Study Design:Cross-sectional study.Level of Evidence:Level 4.Methods:Surveys were completed by soldiers assigned to an Army Infantry Brigade Combat Team. Survey questions inquired about injuries sustained in the previous 12 months, injury onset, and whether injuries were reported to a medical provider. Participants were asked to rank reasons for accurately reporting, underreporting, and/or exaggerating injuries. Chi-square analyses were used to compare differences among underreported injuries in terms of injury onset (gradual vs acute) and sex.Results:A total of 1388 soldiers reported 3202 injuries that had occurred in the previous 12-month period, including 1636 (51%) that were reported and 1566 (49%) that were identified as not reported to medical personnel. More than 49% of reported injuries were described as acute and 51% were described as chronic. Injury exaggeration was reported by 6% of soldiers. The most common reasons for not reporting injuries were fear that an injury might affect future career opportunities and avoidance of military “profiles” (mandated physical restrictions).Conclusion:Approximately half of musculoskeletal injuries in a Brigade Combat Team were not reported.Clinical Relevance:Unreported and untreated injuries can lead to reinjury, chronic pain, performance decrements, and increased costs associated with disability benefits. Additionally, unreported injuries can undermine injury surveillance efforts aimed at reducing the musculoskeletal injury problem in the military.

Over-the-counter pain medication was frequently used for symptom management among Soldiers who did not report their injury to a medical provider.