The impact of inter-limb leg lean tissue mass asymmetry on stair climb performance in career firefighters

Abstract

The purpose of this study was to examine the influence of inter-limb leg lean tissue mass (LTM) asymmetry on stair climb (SC) performance in firefighters. Forty-one career firefighters (age = 32.3 ± 8.2 years, body mass = 92.1 ± 18.6 kg, stature = 178.3 ± 7.9 cm) visited the laboratory on one occasion and completed a whole body and leg composition assessment followed by a timed and weighted SC task. Percent body fat (%BF) and leg LTM were determined during a DEXA scan and regional thigh analysis. Asymmetry was assessed by the percent difference between limbs (dominant limb LTM - non-dominant limb LTM)/dominant limb LTM × 100) and a ± 3% cut-off for asymmetry classification. Participants ascended and descended 26 stairs four times as quickly as possible while wearing a weighted (22 kg) vest. Point biserial correlations were used to assess the relationship of inter-limb leg LTM asymmetry and SC performance before and after controlling for age and %BF. Results indicated that inter-limb leg LTM asymmetry was associated with longer SC task time (poorer performance) both before (r = 0.432, P = 0.005) and after (r = 0.502, P = 0.001) controlling for age and %BF. Our findings indicated that inter-limb leg LTM asymmetry negatively impacts firefighter SC performance, which may be improved with appropriate exercise interventions.

Keywords: Tactical; ageing; body composition; occupational health; occupational performance.

Figure 1.

Examples of the boundaries (highlighted in yellow) used for the limb lean tissue mass analysis from a dual energy x-ray absorptiometry scan (A) and of the stair climb task with weighted vest (B).

Figure 2.

Box-and-whisker plots for asymmetry classification and stair climb time. Median values are marked with a bold line within the boxes. The lower and upper boundaries represent the 25^th (Q1) and 75^th (Q3) percentiles. The lower and upper whiskers indicate the value for (Q1 – [1.5 * Interquartile Range]) and (Q3 + [1.5 * Interquartile Range]), respectively. N = 40 male career firefighters.