Savannah McLain, Sarah Lanham, Mario Keko, Bridget Melton. Georgia Southern University, Statesboro, GA.

BACKGROUND: Explosiveness is a performance variable that often declines with age, stemming from loss of muscle mass and increases in body fat percentage. Research suggests that bone mineral density (BMD) preservation may assist in the maintenance of muscular power as an individual ages, thereby protecting against fractures, falls, and other injuries. Tactical populations, particularly firefighters, are at an increased risk for injury due to the additional load carriage in their profession, and they often perform explosive maneuvers that could lead to injury if muscular power is not maintained. It is unknown whether a firefighter's age or BMD can predict their level of explosiveness. Thus, the purpose of this study was to determine if firefighters’ age or BMD could predict their explosiveness during a maximal-effort vertical jump with a countermovement (CMJ). METHODS: Fifty-five firefighters (179.24+6.23 cm, 95.44+16.82 kg, 33.89+8.82 years) participated in various health and fitness tests used to analyze metrics recommended by the National Fire Protection Agency prior to beginning an individualized wellness program. This study utilized Dual-Energy X-Ray Absorptiometry and a CMJ to assess each firefighter’s BMD and explosiveness, respectively. RESULTS: A linear regression model was used to understand the effect of age and BMD on CMJ performance. All assumptions were met; homoscedasticity was present as assessed by visual inspection of a plot of standardized residuals versus standardized predicted values. Residuals were normally distributed as assessed by visual inspection of a normal probability plot. A statistically significant regression equation was found (F(2,52)=4.703, p=.013), with an R2 of 0.153. Firefighter’s predicted CMJ performance was equal to 46.457-.459(Age)+10.402(BMD), where CMJ performance was measured in centimeters, age was measured in years, and BMD was measured in g/cm3. Firefighter’s CMJ performance decreased .459 cm for each year of age and increased 10.402 cm for every 1 g/cm3 of BMD. Age was found to be a statistically significant predictor of CMJ performance (p=.004) while BMD was not (p>0.05). CONCLUSION: The results suggest that age can be used as a predictor of explosive ability in firefighters, although BMD failed to predict the same outcome. Future research should continue looking at risk factors for firefighter injury, particularly in muscular power declination.

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