The Impact Of Leg Asymmetry On Stair Climb Performance In Career Firefighters

Abstract

Limb-specific regional tissue distribution can be determined using segmental body composition analyses to indicate between limb asymmetries. It is unclear how leg muscle imbalance, as measured by fat free mass, may contribute to performance on job-related tasks. PURPOSE: The purpose of this study was to examine the relationship between leg fat free mass asymmetry (FFMA) and stair climb performance (SCP) in career firefighters. METHODS: Forty-one firefighters [age: 32.3±8.2 years (20-50); stature: 178.3±7.9 cm (159.2-194.6); mass: 92.3±18.7 kg (65.1-133.2); %BF: 24.1±7.9% (9.9-39.4)] volunteered for this investigation. All participants were free of any neuromuscular, cardiovascular, or metabolic diseases, and were instructed to refrain from caffeine and smokeless tobacco for 12 hours, and vigorous lower body exercise for 48 hours. Following an 8 hour fast, %BF and leg FFM was assessed by a daily calibrated dual-energy x-ray absorptiometry. Participants were fitted with a weighted vest (22.73 kg) to simulate the load of their personal protective equipment and self-contained breathing apparatus. Performance was measured as time to completion (s) of stair assent and decent of 26 stairs (20 cm stair height) four times as fast as possible (104 total stairs). Leg FFMA was defined as ±3% difference between leg fat free mass as a cutoff point. A point biserial correlation between FFMA and SCP was performed. In addition, the relationship between FFMA and SCP, while controlling for age and %BF, was assessed. An alpha level was set a priori at 0.05. RESULTS: The point biserial correlation demonstrated that FFMA was significantly associated with SCP (r=0.519, P<0.001). Due to the large range in age and %BF, a follow-up partial correlation analysis controlling for these variables was performed and indicated a similar relationship between FFMA and SCP (r = 0.561, P<0.001). CONCLUSIONS: These findings suggest that the presence of leg FFMA is related to poorer performance on the stair climb assessment with and without accounting for age and %BF. While age is non-modifiable, maintaining good body composition (i.e., %BF and muscle symmetry) as a firefighter may help preserve performance on fire-related tasks. Strategies to improve body composition may impact SCP in firefighters.