Postural Control Changes When Performing Explosive Ordnance Disposal (eod) Operational Tasks With Eod Personal Protection Equipment (PPE): Bending Over At The Waist

PURPOSE: We examined the stress on the trunk and lower extremity muscles when bending over at the waist (BOW) to investigate a suspicious object was performed while wearing EOD PPE. METHODS: Eleven male participants were recruited in the study (24.5 ± 7.1 years old, 179.1 ± 6.4 cm of height, and 84.3 ± 14.5 kg of weight). Each participant performed a series of EOD operational tasks, including BOW five times in two randomly ordered conditions: while wearing EOD PPE (EOD) and without EOD PPE (NOEOD). Sixteen electromyography (EMG) sensors were placed on both sides of the lower back and lower extremities. Force plates in the ground were used to capture the center of pressure (COP) trajectory while BOW was performed. BOW began from an upright position with the feet shoulder-width apart. The participant initiated BOW by stepping one leg (leading side, self-selected) forward and then leaning over that front knee with or without the hands touching the front knee. The foot on the trailing side remained on the ground. The participant then brought the front leg back to the initial position to end BOW. We conducted paired t-tests with the level of significance set at p < 0.05 for the comparison of COP trajectory and EMG between EOD and NOEOD. RESULTS: The total COP displacement and COP displacement in anterior-posterior and medial-lateral directions are significantly smaller in the EOD condition (0.23 ± 0.06 m vs. 0.32 ± 0.07 m, p = 0.001; 0.10 ± 0.03 m vs. 0.14 ± 0.03 m, p = 0.002; 0.21 ± 0.06 m vs. 0.29 ± 0.0 m, p = 0.001). The table below shows the percentage of muscle activation increased in EOD compared to NOEOD in both sides and the corresponding p values. CONCLUSION: The results demonstrate that despite the smaller body shift that occurred while EOD PPE was worn, the bilateral back muscles were activated more, particularly the leading side. Most muscles surrounding the hip and knee of the leading side activated more while EOD PPE was worn. The weight of EOD PPE poses stress to both concentric and eccentric muscles. - Muscles Leading Side Trailing Side Increased percentage (%)mean ± standard deviation p value Increased percentage (%)mean ± standard deviation p value Erector Spinae 107.69 ± 103.46 0.003 * 36.61 ± 74.08 0.011 * Gluteus Medius 45.06 ± 80.35 0.567 39.75 ± 78.13 0.592 Rectus Femoris 130.02 ± 167.94 0.005 * 82.31 ± 102.47 0.009 * Vastus Medialis 147.88 ± 217.43 0.016 * 140.53 ± 214.66 0.392 Biceps Femoris 159.82 ± 218.21 0.027 * 75.21 ± 98.51 0.340 Tibialis Anterior 34.83 ± 61.15 0.058 64.41 ± 67.03 0.207 Gastrocnemius 77.55 ± 80.68 0.072 30.70 ± 60.03 0.910 Soleus 66.93 ± 47.89 0.003 * 60.11 ± 58.67 0.005 * Funded by the U.S. Army Combat Capabilities Development Command – Soldier Center, Award ID: W911QY2020005.