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The Influence Of Percent Body Fat On Skeletal Muscle Quality In Firefighter Personnel: 3142 Board #207 June 3, 3: 30 PM - 5: 00 PM.

Firefighters are a critical part of public safety and perform various physically demanding jobs in dangerous situations. Recent studies suggest firefighters have a greater prevalence of overweight and obesity than the general public. Excess body fat has been associated with an increased risk of musculoskeletal injury and poor performance. Skeletal muscle quality (i.e. degree of intramuscular fat) can be examined using ultrasonography (US) and has recently been shown to be an important contributor to lower extremity performance. However, contrasting findings exist for the relationship between US derived muscle quality and a marker of body composition. PURPOSE: The aim of this study was to examine the relationship between skeletal muscle quality and percent body fat (%BF) and in career firefighters. METHODS: Body composition was assessed in twenty-eight male firefighters (mean ± SD: age, 34.6±3.2; stature, 179.9±5.4cm; body mass 103.7±22.2kg) using a fourcompartment (4-C) model that utilizes body volume (BV) from air displacement plethysmography, total body water (TBW) from bioelectrical impedance spectroscopy, and bone mineral content (BMC) from dual-energy x-ray absorptiometry. Muscle quality was assessed using panoramic brightness-mode US of the vastus lateralis (VL). Ultrasound images were collected on the right thigh with subjects lying in the supine position and the leg propped at 50 degrees of knee flexion. The US probe was positioned perpendicular to the skin, moving lateral to medial in the traverse plane of the VL. Transmission gel was applied to the US probe in order to enhance acoustic coupling. ImageJ software was used to determine echo intensity (EI) or the mean gray scale value of the selected muscle region of interest. The EI values were corrected for subcutaneous fat depth. The relationship between %BF and EI was assessed using Pearson’s correlation coefficient (r) with an alpha level set a priori at P≤0.05. RESULTS: There was a significant positive relationship between %BF and VL EI (r=.517, P<0.01). CONCLUSION: These findings indicated that greater total %BF is associated with decreased muscle quality. The high rates of obesity in the fire service continues to be a public health concern which may also influence skeletal muscle performance. Grant Funding: Supported by NIOSH Grant T42OH008673