The Influence of Habitual Protein Intake on Body Composition and Muscular Strength in Career Firefighters.

OBJECTIVE: The aim of this research was to determine the relationship among protein (PRO) intake, body composition, and muscle strength in overweight and obese firefighters. A secondary objective was to evaluate differences in body composition and muscle strength among overweight and obese firefighters with low (L; < 0.8 g·kg-1), moderate (M; 0.8-1.0 g·kg-1), and high (H; > 1.0 g·kg-1) PRO intake. METHODS: Relative PRO intake [r_PRO] was evaluated from 3-day dietary logs, self-reported by 43 overweight and obese male career firefighters (mean ± standard deviation; age = 37.3 ± 7.2 years; body mass index = 33.2 ± 5.0 kg·m-2; percent body fat [%BF] = 28.9 ± 4.0%). Body composition (fat mass [FM], %BF, lean mass [LM], percent LM [%LM]) and muscle strength (peak torque [PT], relative peak torque [r_PT] of the leg extensors) were measured using dual-energy x-ray absorptiometry and isokinetic dynamometry, respectively. RESULTS: Greater r_PRO was associated with less FM, %BF, LM (r = -0.498 to -0.363) and greater %LM (r = 0.363), but not muscle strength (p > 0.05). Fat mass (r = -0.373) and %BF (r = -0.369) were associated with lower r_PT; %LM was associated with greater r_PT (r = 0.373). Individuals with L r_PRO had greater FM (mean difference ± standard error: L-H = 10.08 ± 3.18 kg), %BF (L-H = 3.8% ± 1.4%) and lower %LM (L-H = -3.7% ± 1.3%) than those with H r_PRO (p < 0.05) but no significant differences in muscle strength (p > 0.05). CONCLUSIONS: Protein intake > 0.8 g·kg-1 was associated with more favorable body composition in male career firefighters.

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

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.

Relationships Between Neuromuscular Function and Functional Balance Performance in Firefighters.

The purpose of the present study was to examine the relationships between neuromuscular function and functional balance performance in firefighters. Fifty career firefighters (35.1 ± 7.5 yr) performed isometric leg extension and flexion muscle actions to examine peak torque (PT), and absolute (aTQ) and normalized (nTQ; %PT) rapid torque variables at 50, 100, 150, and 200 ms. A performance index (PI) was determined from the functional balance assessment completion time. Partial correlations were used to examine the relationship between the PI and the maximal and rapid TQ variables for each muscle and the composite value, while controlling for demographic data related to the PI. Multiple regression analyses examined the relative contributions of the maximal and rapid aTQ variables, and demographic data on the PI. After controlling for age and %BF, the majority of the later aTQ and nTQ variables (100-200 ms) and PT were associated with the PI (r = -0.501--0.315). Age, %BF, and aTQ100 explained 42-50% of the variance in the PI. Lower rapid strength, increased age, and poorer body composition were related to worse performance during the functional balance assessment. Strategies to improve rapid strength and %BF, especially in aging firefighters may impact dynamic balance abilities in firefighters.

Consistency of a mobile body composition trailer: a novel portable laboratory assessment?

OBJECTIVE: The purpose of this investigation was to (i) assess the test-retest reliability and minimum difference (MD) values of air-displacement plethysmography (ADP) and the Siri 3-compartment (3-C) model in a mobile trailer, and (ii) identify any environmental fluctuations in the trailer. METHODS: percent body fat (%BF) was examined in 22 firefighters on two separate days in a climate-controlled mobile trailer using ADP. Total body water was examined in a subset of participants (n = 12) using bioelectrical impedance spectroscopy (BIS) to determine %BF using Siri's 3-C model. RESULTS: There were no differences in environmental measures (P≥0·138), %BF for ADP (P = 0·276), or %BF for the Siri 3-C model (P = 0·382) between day 1 and day 2. Intraclass correlation coefficient and standard error of measurement values for ADP and the Siri 3-C model were 0·978 and 1·3% and 0·986 and 0·6%, respectively. The MD values were 3·6% and 1·7%, respectively. CONCLUSIONS: These findings indicate that ADP can reliably determine %BF when transported in a climate-controlled mobile trailer. Additional accuracy is achievable with the Siri 3-C model, providing an attractive and promising method to measure body composition in larger scale community-based settings.

The influence of subcutaneous fat on the relationship between body composition and ultrasound-derived muscle quality.

Ultrasound echo intensity (EI) values are a popular assessment of muscle quality. The relationship between EI and total (%fat) and regional (%fatlimb) body composition was examined in 40 men, prior to and after accounting for subcutaneous fat thickness. Uncorrected EI values suggest that muscle quality improves (r = -0.329 to -0.224; P = 0.038-0.165) with greater %fat and %fatlimb. However, corrected EI values indicated that muscle quality decreases (r = 0.711 to 0.798; P < 0.001) with greater %fat and %fatlimb.

The influence of ultrasound measurement techniques on the age-related differences in Achilles tendon size.

Achilles tendon (AT) properties change with age, however the extent to which aging influences the size of the AT may be influenced by the measurement technique. The purpose of this study was to 1) examine the age-related differences in AT size using measures of cross-sectional area (CSA) and thickness, and 2) to determine the test-retest reliability and minimum difference (MD) values of these measures. The size of the AT was examined in 19 young (19.79 ± 2.3 years) and 18 older (69.4 ± 3.1 years) healthy men on two separate occasions using an ultrasonography. The CSA and thickness of the AT were determined by separate transverse and longitudinal scans on the right leg at the same distance from the medial malleolus, respectively. Prior to and after accounting for body mass, AT CSA was larger (P ≤ 0.01) in the older men (64.49 ± 13.87 mm(2)) when compared to the younger men (44.12 ± 16.04 mm(2)), however there were no differences in AT thickness between age groups (P=0.96). In addition, there was no systematic error (P>0.05) between testing days, and the intraclass correlation coefficients, standard error of measurement (expressed as a % of the mean), and MD values for CSA and thickness ranged from 0.80-0.98, 5.46-8.68%, and 5.65-7.94 mm(2) and 0.51-0.86 mm, respectively between both groups. These findings suggest that the reliability of the CSA and thickness measurements were similar, however, CSA was a more sensitive measure to detect the age-related changes of AT size.

Pennation angle does not influence the age-related differences in echo intensity of the medial gastrocnemius.

The reflection of an ultrasound (US) wave is strongest when the propagation direction of the wave is perpendicular to muscle fascicles. Thus, it is possible that muscle echo intensity (EI), a gray-scale US measure of muscle quality, may be influenced by the angulation of muscle fascicles. Therefore, the purpose of this study was to determine if age-related differences in muscle EI values are influenced by differences in pennation angle (PA). Medial gastrocnemius EI and PA were examined using panoramic US imaging in 24 young (19.8 ± 1.7 y) and 21 older (69.3 ± 3.3 y) men. The young men had lower EI values (young = 74.1 ± 6.3 a.u., older = 89.1 ± 8.8 a.u.) and a greater PA (young = 20.0 ± 2.9°; older = 17.2 ± 2.5°) compared with the older men (p < 0.01). In addition, there was a negative relationship (r = -0.473, p < 0.01) between PA and EI with both groups combined, but no significant relationship when the young (r = -0.334, p = 0.111) and older (r = -0.147, p = 0.525) men were examined separately. An analysis of covariance revealed that muscle EI values remained different (p < 0.01) between age groups after adjustment for differences in PA. Thus, after statistically adjusting the mean EI values for the differences in PA, there were still significant age-related differences in EI. These findings may provide further support that the age-related changes in muscle EI values reflect changes in tissue composition (i.e., increase in intramuscular fat and/or connective tissue) commonly reported in older adults.