Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes.

Ketosis, the metabolic response to energy crisis, is a mechanism to sustain life by altering oxidative fuel selection. Often overlooked for its metabolic potential, ketosis is poorly understood outside of starvation or diabetic crisis. Thus, we studied the biochemical advantages of ketosis in humans using a ketone ester-based form of nutrition without the unwanted milieu of endogenous ketone body production by caloric or carbohydrate restriction. In five separate studies of 39 high-performance athletes, we show how this unique metabolic state improves physical endurance by altering fuel competition for oxidative respiration. Ketosis decreased muscle glycolysis and plasma lactate concentrations, while providing an alternative substrate for oxidative phosphorylation. Ketosis increased intramuscular triacylglycerol oxidation during exercise, even in the presence of normal muscle glycogen, co-ingested carbohydrate and elevated insulin. These findings may hold clues to greater human potential and a better understanding of fuel metabolism in health and disease.

Regional cartilage properties of three quadruped tibiofemoral joints used in musculoskeletal research studies.

Quadruped joints are commonly used in musculoskeletal studies as a surrogate for human joints despite inherent differences in tissue properties. Although concerns exist regarding model validity, relatively few studies comparing the mechanical properties of quadruped tissue exist. This study aimed to characterise the regional intrinsic mechanical properties and thickness of tibiofemoral cartilage from three quadrupeds used in modern musculoskeletal research. Osteochondral plugs were removed from the major weight-bearing regions of porcine (6 months), bovine (18-24 months) and ovine (approximately 5 years) tibiofemoral joints. The equilibrium elastic modulus and permeability of the cartilage were derived by combining the creep indention deformation results and calculated tissue thickness within an in-silica model. Results showed significant interspecies and regional variation in cartilage thickness. Cartilage was thickest on porcine femoral condyles whereas ovine cartilage was consistently thinner across all sites. Furthermore, porcine tissue had a significantly lower equilibrium elastic modulus and significantly higher permeability than ovine cartilage. The results highlight the importance of considering the interspecies and regional variation in quadruped tissue properties when selecting animal joints for musculoskeletal investigations.

The effect of bone fragment size and cerebrospinal fluid on spinal cord deformation during trauma: an ex vivo study.

OBJECT: The purpose of the study was to assess the effect of CSF and the size of the impacting bone fragment area on spinal cord deformation during trauma. METHODS: A transverse impact rig was used to produce repeated impacts on bovine and surrogate cord models. Tests were recorded with high-speed video and performed on specimens with and without CSF and/or dura mater and with 3 different impactor areas. RESULTS: The CSF layer was found to reduce the maximum cord deformation significantly. A 50% reduction in impact area significantly increased the maximum cord deformation by 20-30%. The surrogate model showed similar trends to the bovine model but with lower absolute deformation values. CONCLUSIONS: Cerebrospinal fluid protects the cord during impact by reducing its deformation. A smaller bone fragment impact area increases the deformation of the cord, in agreement with clinical results, where a higher impact energy-possibly giving rise to smaller fragments-results in a worse neurological deficit.