Influence of Lower Extremity Muscle Size and Quality on Stair-Climb Performance in Career Firefighters

Abstract

The purpose of this study was to examine the influence of lower extremity muscular size and quality on stair-climb performance (SCP) in career firefighters. Forty-six male career firefighters (age = 37.0 ± 7.2 years; stature = 180.2 ± 6.9 cm; body mass = 108.0 ± 19.8 kg) volunteered for this study. Panoramic ultrasound images of the vastus lateralis and rectus femoris were obtained to determine cross-sectional area (CSA) and echo intensity (EI) of each muscle. The CSA of each muscle was then summed together and normalized to body mass (CSA/BM [QCSA]). Additionally, EI was averaged across both muscles (QEI). Participants then performed a timed and weighted SCP assessment where they ascended and descended 26 stairs 4 times as quickly as possible while wearing a weighted vest (22.73 kg) to simulate the weight of their self-contained breathing apparatus and turnout gear. Bivariate correlations and stepwise regression analyses were used to examine the relationships among variables and the relative contributions of QCSA and QEI to SCP. Partial correlations were used to examine the relationship between QCSA and SCP and QEI and SCP while controlling for age and body mass index (BMI). The results indicated that QCSA and QEI were significantly related to SCP before (r = -0.492, p = 0.001; r = 0.363, p = 0.013, respectively) and after accounting for age and BMI (r = -0.324, p = 0.032; r = 0.413, p = 0.005, respectively). Both QCSA and QEI contributed significantly to the prediction of SCP (r = 0.560, p < 0.001). These findings indicate that lower extremity muscle size and quality are important contributors to critical firefighting tasks, which have been shown to be improved with resistance training.

Echo intensity and muscle thickness as predictors Of athleticism and isometric strength in middle‐school boys

“…Removing the influence of age and mass eliminated the significant correlation between VL muscle thickness and peak torque, but not RTD100 or RTD200. These findings are consistent with the growing body of literature that shows significant correlations between lower‐extremity muscle quality and quantity versus physical function in adults …”

“…Echo intensity and muscle thickness are used increasingly in adult studies to examine muscle quality and quantity, respectively. The results of our study are consistent with those that have demonstrated significant relationships between these variables and physical function . Of interest, in older women, quadriceps femoris echo intensity obtained by means of ultrasonography provided better predictive information concerning peak torque and functionality than the actual ratio of muscle strength to size .…”

“…In both men and women, vastus lateralis (VL) and rectus femoris (RF) echo intensity and muscle thickness have shown significant correlation with power output during 30 s maximal sprints on a nonmotorized treadmill, as well as jump power and sprint speed . More recently, echo intensity was reported to correlate significantly with stair‐climbing ability in career firefighters, even when controlling for age and body mass index . In older adults, RF echo intensity has shown moderate correlations with workloads at the ventilatory threshold during tests of maximal aerobic power, gait speed, rate of torque development (RTD), 30 s sit‐to‐stand performance, and maximal strength .…”

“…In a study involving older women, muscle thickness was found to be a predictor of maximal strength, but echo intensity better reflected activities of daily living, thereby suggesting that these variables provide slightly dissimilar information. Collectively, there is ample evidence that echo intensity and muscle thickness serve as unique, independent predictors of muscle function in adults …”

“…3 More recently, echo intensity was reported to correlate significantly with stair-climbing ability in career firefighters, even when controlling for age and body mass index. 11 In older adults, RF echo intensity has shown moderate correlations with workloads at the ventilatory threshold during tests of maximal aerobic power, 12 gait speed, 13 rate of torque development (RTD), 13 30 s sit-to-stand performance, 13 and maximal strength. [12][13][14][15] In a study involving older women, 13 muscle thickness was found to be a predictor of maximal strength, but echo intensity better reflected activities of daily living, thereby suggesting that these variables provide slightly dissimilar information.…”