Fighter pilots’ physical performance and spinal-injury induced flight duty limitations

This thesis investigates the effects of physical fitness, muscle cross-sectional area (CSA) and Gz exposure and their interaction in fighter pilots’ spinal disorders and resulting flight duty limitations (FDL). The primary aim of the study was to evaluate the predictive role of physical and functional fitness tests and muscle CSA in overall low back pain (LBP) and FDL. Other aims were to investigate associations between cumulative Gz exposure and FDL and to study the effects of the gradual increase of exposure on exposure-induced muscular activity responses. Four different study settings were used. Association between functional tests and LBP was studied in a five-year follow-up. Shoulder and neck muscle activity was compared, via electromyography (EMG), between groups of experienced and inexperienced pilots under high Gz exposure. Association between early-career Gz exposure and physical fitness in the pilot selection phase was studied retrospectively among FDL-pilots and non-FDL pilots. Associations between CSA of the lumbar muscles and spinal disorders were studied in a five-year follow-up. The results showed an association between an isometric back endurance test and physical activityrelated LBP. Pull-up and back extension test results obtained in the selection phase were associated with spinal disorder-induced FDL during fighter pilots’ career, but similar association between aerobic fitness and FDL was not observed. Pilots who had experience in flying high-performance aircraft (HPA) had significantly lower shoulder and neck muscle EMG activity at high Gz levels and higher passive G-tolerance than pilots who had no experience in HPA flying. Cumulative Gz exposure during the early career was not associated with subsequent spinal disorder-induced FDL. No association was found between muscle composition or CSA and LBP. Thus, causes and development of spinal disorder -induced FDL seem to be multifactorial. In conclusion, the results show that an adequate level of axial strength and endurance may protect military pilots from spinal disorders. Pilots who had indicated in the selection phase that they do not participate in competitive and guided sports programs may be under an increased risk of spinal disorderinduced FDL. In addition, less experienced pilots may find similar missions more fatiguing than their more experienced colleagues. However, Gz exposure at an individual level does not have a predictive value on future FDL. Keywords: neck pain, low back pain, flight duty limitation, physical fitness, high-performance aircraft, G-force