Firefighting is a very hazardous profession. Firefighters experience an injury rate that is three times higher than other physically demanding professions and the death rate in the fire service is also much higher compared to typical. Throughout the literature, data suggest the physical nature of firefighting contributes to the high incidence of injury and death among firefighters. As such, special interest groups and firefighting organizations advocate for firefighters to exercise and stay fit in order to safeguard their physical health. Yet, despite these efforts, firefighters still experience a very high incidence of back injuries and heart attacks which can lead to early retirement from disability or death. In the first aim of this dissertation, we examined the relationships between specific back fitness tests and history of back injuries in 113 firefighters in an effort to understand which fitness tests may aid in screening firefighters for risk of back injury. We found that a test of lumbar extension flexibility was associated with a higher incidence of back injuries among our sample (p<0.01). In the second aim of the study, we investigated whether perceived fitness was related to history of back injuries since firefighters’ perceptions of their fitness level may direct how they choose to perform job tasks that pose high risk for injury. Within the same sample of firefighters, we found that perceived fitness was not related to history of back injuries nor was the relationship between actual fitness and history of back injuries mediated by perceived fitness. However, perceived fitness correlated with scores on our back strength (r=0.28; p=0.003) and hamstring strength (r=0.21; p=0.03) tests. In the third aim of the dissertation, we sought to develop a treadmill walking protocol to screen firefighters for low aerobic capacity which is a major risk factor for heart attack. Thirty-eight male firefighters wore a vest weighing 20% of their body weight and performed a walking VO2max test in which the treadmill grade increased by 1% each minute. The predicted VO2max from this walking test was very accurate; within a standard error of the estimate of 3.2 ml/kg/min. This new (Moore) protocol requires only a standard treadmill and is more job specific than a running test. In conclusion, more research needs to be conducted to understand how firefighters’ perceived fitness directs their behaviors when performing job tasks and how high levels of fitness can protect against back injuries and heart attacks in firefighters. This dissertation has contributed to the development of screening protocols to aid in preventing these adverse events. / Graduation date: 2013