Resumen de Influence of Muscle Quality on the Differences in Strength From Slow to Fast Velocities in Career Firefighters

Gena R. Gerstner, Hayden K. Giuliani, Jacob A. Mota, Eric D. Ryan

• The purpose of this study was to examine the relationship between ultrasound-derived muscle quality and the %decrease in peak torque (PT) from slow to fast velocities in career firefighters. Thirty-nine male career firefighters (mean ± SD: age = 36.90 ± 6.87 years; stature = 180.93 ± 6.98 cm; mass = 109.30 ± 20.57 kg; and body mass index [BMI] = 33.24 ± 4.95 kg·m-2) performed 3 maximal concentric isokinetic contractions at a slow (1.05 rad·s-1) and fast (4.19 rad·s-1) velocity in random order. The velocity-related decrease in PT was calculated as the %decrease from 1.05 to 4.19 rad·s-1. Ultrasonography was used to determine subcutaneous fat corrected echo intensity (EI) to represent muscle quality before strength testing. The results indicated that there was a significant relationship between EI and %decrease in PT while adjusting for age (rpartial = 0.331, p = 0.042), and age and BMI (rpartial = 0.325, p = 0.050). These findings suggest that velocity-impaired isokinetic strength may be influenced by alterations in skeletal muscle tissue composition. Future studies are needed to determine whether the %decrease in PT is related to performance during critical firefighter tasks.