Evangeline P. Soucie1, Gena R. Gerstner1,2, Megan R. Laffan1, Abigail J. Trivisonno1, Hayden K. Giuliani-Dewig1, Jacob A. Mota3, Eric D. Ryan1. 1University of North Carolina at Chapel Hill, Chapel Hill, NC. 2Old Dominion University, Norfolk, VA. 3University of Alabama, Tuscaloosa, AL.

BACKGROUND: Previous research has speculated that segmental bioelectrical impedance spectroscopy (sBIS) measures of characteristic frequency (CF) and phase angle (PA) may reflect skeletal muscle size and quality, respectively. Further, quadriceps muscle size and quality have also been found to influence stair climb performance (SCP) in career firefighters. Therefore, the purpose of this study was to examine the relationship of sBIS measures of CF and PA with SCP in career firefighters. METHODS: Thirty-eight male career firefighters (age: 32.2±8.0 yrs, stature: 178.6±8.1 cm, body mass: 92.9±19.3 kg) volunteered for this study. Participants refrained from vigorous exercise for 48 hours and fasted at least eight hours prior to visiting the laboratory on one occasion. Following a 10-minute lying period, sBIS was used to assess CF and PA of the dominant thigh. Characteristic frequency was normalized to body mass to represent a proxy for relative muscle size. Emitting electrodes were placed 10 cm distal to the anterior superior iliac spine and 10 cm proximal to the tibial tuberosity. The sensing electrodes were placed five cm inside the emitting electrodes. Prior to the stair climb, participants consumed a standardized shake to break their fast. Participants performed a stair climb assessment wearing a 22.73kg weight vest to simulate the weight of their personal protective equipment and self-contained breathing apparatus. After a warm-up, participants climbed a flight of stairs four times (104 total steps) without stopping or holding onto the handrails. Pearson’s product-moment correlation coefficients (r) were used to determine the associations between sBIS measures (i.e., CF and PA) and SCP (i.e., completion time). A stepwise regression analysis was used to determine the relative contributions of CF and PA on SCP. An alpha level of ≤0.05 was set to determine statistical significance. RESULTS: There was an association between both CF and SCP (r= -0.390, P=0.016) as well as PA and SCP (r= -0.516,P˂0.01). The stepwise analysis suggested that PA alone significantly contributed to SCP (R2=0.246, P˂0.01). CONCLUSIONS: These results suggest that CF and PA, estimates of muscle size and quality, influence SCP, with PA being the most significant predictor of SCP in career firefighters.

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