Neuromuscular Factors Associated With Stair Climb Performance In Firefighters

Abstract

PURPOSE: The weighted stair climb is a critical and essential occupational task for career firefighters. However, limited data is available investigating the influence of neuromuscular function on stair climb performance (SCP). The purpose of this study was to examine the influence of lower extremity strength, power, fatigability, and steadiness on SCP. METHODS: Forty-one firefighters (32.34±8.20 yrs) completed one laboratory visit where they completed leg extension strength testing of the dominant leg on an isokinetic dynamometer to determine peak torque (PT). Participants then traced a line at 10% (Stead10) and 50% (Stead50) of PT for 30 seconds to determine steadiness (coefficient variation of torque). Fatigability was determined from the reduction in PT following 30 consecutive isotonic contractions (80° of range of motion) at 40% of their PT. Peak power (PP) was determined from the highest value during the first five isotonic contractions. PT and PP were normalized to body mass (kg) prior to analysis (PT/kg and PP/kg). Following a 20-minute rest, participants then completed a weighted (22.73 kg vest) stair climb by ascending and descending 26 steps, four times. Pearson’s product-moment correlation coefficients were used to examine the associations between each neuromuscular variable and SCP. A stepwise multiple regression analysis was then completed to determine the relative contributions of all neuromuscular variables on SCP. An a priori alpha level of ≤ 0.05 was used to determine statistical significance. RESULTS: Faster SCP was associated with greater PP/kg (r = -0.530; P=0.001), PT/kg (r = -0.421; P=0.007), and lower fatigability (r = 0.389; P=0.014). The stepwise multiple regression analyses determined that PP/kg and Stead50 were the most significant predictors of SCP (R2 = 0.442; P=0.013). CONCLUSIONS: Our findings suggest that lower extremity power output and motor control are the strongest neuromuscular predictors of SCP. These findings are impactful considering these variables can be improved with exercise.