USING ADVANCED STATISTICS TO ANALYZE PHYSIOLOGICAL PARAMETERS DURING SUBMAXIMAL ISOMETRIC CONTRACTIONS OF THE NECK IN HELICOPTER AIRCREW

Introduction: Our previous work in the area of flight-induced neck strain has identified statistically significant differences in flight history, neuromuscular, and metabolic variables as they pertain to pain reports in helicopter aircrew members. However, to date, these differences have not been detected under submaximal or non-fatigued conditions that are similar to NVG flight. Methods: 40 helicopter aircrew (22 pilots, 18 flight engineers (FE) performed graded submaximal isometric contractions of cervical flexion, extension, and left and right lateral flexion while bilaterally monitored with electromyography (EMG) and near-infrared spectroscopy (NIRS). The splenius capitis and sternocleidomastoid were monitored with only EMG while the upper trapezius was monitored with both EMG (root mean square, normalized median frequency) and NIRS (oxyhemoglobin, deoxyhemoglobin, total oxygenation index, total hemoglobin, cytochrome-c oxidase). The resulting waveforms for each of the EMG and NIRS variables were loaded for principal components analysis (PCA) with the covariance matrix. The stratified PCA scores (symptomatic vs. asymptomatic; pilot vs. FE) for each waveform variable were analyzed using parametric (one- or two-way ANOVA) or non-parametric tests (Kruskal-Wallis), as warranted. Results: Statistically significant differences were observed during the four contractions by position, by symptom reports, and by position and pain symptom reports. Discussion: Using this statistical analysis, differences were found during submaximal workloads for the neck musculature of symptomatic and asymptomatic helicopter aircrew.