(30) IMPACT OF ON-DUTY ENDURANCE EXERCISE ON FIREFIGHTERS’ NEUROMUSCULAR FUNCTION AND WORKING MEMORY

Purpose: To evaluate the acute impact of on-duty endurance exercise on firefighters’ subsequent neuromuscular function and working memory (WM). Methods: 18 male career structural firefighters (Age: 32.1±4.1 yr; Experience 7.2±4.2 yr; V̇O_2peak: 46.6±5.7 mL/kg/min) completed assessments of neuromuscular function and WM before and after high intensity interval training (HIIT) and continuous endurance exercise (CEE). Sessions were separated by 72 hr. HIIT and CEE velocities were determined from the results of a a maximal graded exercise test. HIIT included 10 intervals of 45 s of work at 110% of the velocity associated with V̇O_2peak and 45 s of passive recovery. CEE included a 30 min bout at 10% below ventilatory threshold. Blood lactate and perceived exertion (RPE; 6-20) were recorded as descriptors of exercise intensity. Neuromuscular outcomes were assessed using dual force plates. Peak force (N) and rate of force development (RFD) at 200 ms (N/s) were assessed during an isometric midthigh pull prior to and immediately post exercise. Postural sway metrics (mean velocity: mm/s; total excursion: mm) were evaluated while wearing personal protective equipment during a 30 s bilateral stance with eyes open prior to and 10 min post exercise. WM was assessed by written recall of 10 variables from a simulated emergency radio communication prior to and 20 min post exercise. Two-way repeated-measures ANOVA with post hoc tests were used to evaluate changes across time points and conditions. Relative difference (RD), partial eta squared (η_p²), and statistical power values are reported. Significance was set at p< 0.05. Results: HIIT yielded higher levels of blood lactate (HIIT: 6.1±1.8 vs. CEE: 3.5±1.2 mmol/L, p≤0.01), but similar RPE levels (HIIT: 15.4±3.1 vs. CEE: 14.8±2.2, p=0.08) compared to CEE. There were no condition, time, or interaction effects on postural sway mean velocity or excursion (p≥0.06). Peak force displayed an effect of time (F(1,16)=23.85, p< 0.01, η_p²=0.60, Power=0.99), with no effect of condition (p=0.14) or interaction (p=0.34). Peak force decrements were observed following completion of HIIT (RD=-4.4%, p< 0.01) and CEE (RD=-6.1%, p< 0.01). RFD yielded an effect of time (F(1,16)=6.24, p=0.024, η_p²=0.28, Power=0.65), with no effect of condition (p=0.79) or interaction (p=0.70). Post hoc analyses did not specify RFD decrements following completion of HIIT (t(1,16)=1.78, p=0.10, RD=-4.3%) or CEE (t(1,17)=1.61, p=0.06, RD=-2.5%). There was an effect of time on WM (F(1,17)=8.58, p< 0.01, η_p²=0.34, Power=0.79). Specifically, CEE significantly decreased WM (RD: -5.8±14.4%; t(17)=1.88, p=0.04; d=0.44), whereas HIIT displayed a non-significant decrease (RD: -7.3±23.0%; t(17)=1.67, p=0.06; d=0.39). There were no condition or interaction effects for WM (p≥0.07). Conclusions: Completion of on-duty HIIT and CEE workouts did not impact firefighters’ postural sway, but CEE did reduce working memory. Practical Applications: Appropriately programmed on-duty endurance exercise may not be detrimental to subsequent static balance in recreationally trained structural firefighters. Participation is encouraged to enhance cardiorespiratory outcomes for health and occupational readiness. Additional research is warranted to further elucidate the impact of CEE on occupational working memory. Acknowledgements: This investigation was funded by the NSCA Foundation Doctoral Student Research Grant.