(26) THE IMPACT OF THE VISUAL SYSTEM ON DYNAMIC STABILITY WHILE WEARING FIRE-SPECIFIC EQUIPMENT AND GEAR

Purpose: To explore the effect vision had on dynamic postural stability during a single-leg landing and stabilization (SLLS) task. Methods: 24 fire cadets participated in the study (25.97±4.90 yrs, 180.76±9.15 cm, and 80.64±22.68 kg). Participants performed three SLLS trials under three different conditions: 1) without equipment and gear (EQG), 2) with EQG, and 3) with EQG and a tented BAShield (EQG-S). All conditions requiring EQG included a self-contained breathing apparatus, turnout coat, pants, boots, hood, gloves, and helmet (mass, 24.5 kg). The SLLS task required the participant to drop onto their dominant leg from a 30 cm box placed 10% of their height away from a 40 cm x 60 cm force plate. Upon landing, participants had to remain motionless for 10 seconds. The first, 3 seconds of the vertical ground reaction forces (VGRF) after initial ground contact (IGC) were used to calculate the DPSI. IGC was defined as the instant the VGRF exceeded 5% body weight. A higher DPSI value represents worse dynamic postural stability. A repeated measures ANOVA was conducted to determine the effects of vision on DPSI while donning EQG. Results: Mauchly's test of sphericity indicated that the assumption of sphericity had been violated, χ2(2) = 14.798, p < .001. Epsilon (ε) was 0.671, calculated according to Greenhouse and Geisser (1959), and was used to correct the one-way repeated measures ANOVA. DPSI was statistically significantly different across conditions, F(1.343, 30.880) = 134.448, p < .001, η² = .854. DPSI increased from 0.375±0.054 without EQG to 0.528 ± 0.079 with EQG and to 0.562 ± 0.086 with EQG-S. Post hoc analysis with a Bonferroni adjustment revealed that DPSI was statistically significantly higher going from without EQG to with EQG [-0.153 (95% CI, -0.187 to -0.119), p < .001], and from without EQG to with EQG-S [-0.187 (95% CI, -0.225 to -0.149), p < .001], and from with EQG to with EQG-S [-0.034 (95% CI, -0.052 to -0.016), p < .001]. Conclusions: The findings of this study suggest that diminished sensor inputs from the visual system alter postural stability while donning EQG. Practical Applications: Firefighter strength and conditioning programs should incorporate balanced training activities that require donning of EQG. Balance training should also be performed within scenarios that diminish visual inputs. Low-visibility balance training activities would require firefighters to rely more heavily on the somatosensory and vestibular systems to maintain stability. Acknowledgements: Tulsa Fire Department, Tulsa, OK, USA