Ultrasonography-derived cross-sectional area (CSA) and echo intensity (EI) are increasingly utilized by investigators to study muscle size and quality, respectively. We sought to examine age, sex, and region (proximal, middle, distal) differences in vastus lateralis and rectus femoris CSA and EI, and determine whether correction for subcutaneous fat thickness influences the magnitude of EI differences. Fifteen younger men (mean age=23 years), fifteen younger women (21 years), eleven older men (74 years), and fifteen older women (70 years) participated. Clear differences were observed among age, sex, and region for vastus lateralis CSA (p≤0.013, d=0.38-0.73), whereas rectus femoris CSA was only different between younger and older participants at the proximal region (p=0.017, d=0.65). Uncorrected EI was greatest at the distal region of both muscles (p<0.001, d=0.59-1.38), with only the younger men having significantly lower EI values than the other groups (p≤0.043, d=0.37-0.63). Subcutaneous fat correction resulted in a marked increase in the magnitude of sex-specific EI differences (p≤0.032, d≥0.42). Additionally, subcutaneous fat correction increased the uniformity of EI throughout the thigh. These findings highlight considerable region-specific differences in muscle size and quality among younger and older men and women, and highlight the need to correct for subcutaneous fat thickness when examining EI.
Novelty Bullets
• Rectus femoris CSA is similar between younger and older adults except at the most proximal site evaluated.
• Age- and sex-specific differences in uncorrected EI are non-uniform across the thigh.
• Correction for subcutaneous fat thickness substantially increased EI in women, resulting in greater sex differences.
The high ICCs and low SEMs suggest that ultrasonography-derived rectus femoris percent fat may be a reliable tool for tracking changes in lower extremity intramuscular adiposity.
Individuals with spinal cord injuries (SCI) commonly present with component risk factors for cardiometabolic risk and combined risk factors for cardiometabolic syndrome (CMS). These primary risk factors include obesity, dyslipidemia, dysglycemia/insulin resistance, and hypertension. Commonly referred to as “silent killers”, cardiometabolic risk and CMS increase the threat of cardiovascular disease, a leading cause of death after SCI. This narrative review will examine current data and the etiopathogenesis of cardiometabolic risk, CMS, and cardiovascular disease associated with SCI, focusing on pivotal research on cardiometabolic sequelae from the last five years. The review will also provide current diagnosis and surveillance criteria for cardiometabolic disorders after SCI, a novel obesity classification system based on percent total body fat, and lifestyle management strategies to improve cardiometabolic health.
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