A Cross-Sectional Analysis of the Muscle Strength, Spinal Shrinkage and Recovery During a Working Day of Military Police Officers

Abstract Background: Military personnel has a large prevalence of back, especially those involved in patrolling routines as they are required to wear heavy protective equipment. Patrolling includes long periods sustaining the protective equipment is sustained in a sitting either on or in a motor vehicle (motorcycle or car). Thus, understanding spinal loading of Military Police Officers (MPO) after patrolling by car (CAR; n=14), motorcycle (MOT; n=14), and administrative (ADM; n=14) routines is relevant to establish preventive strategies. Design: The torque of the trunk and working and anthropometric characteristics were assessed to explain and spinal loading using stature variation measures. Precise stature measures were performed before and after a 6h journey (LOSS) and 20min after a resting posture (RECOV). The isometric peak torque of the trunk extensor (PTE.BM-1) and flexor (PTF.BM-1) muscles were measured before the working journey. Results: The LOSS was similar between CAR and MOT (4.8 and 5.8mm, respectively) after 6h of patrolling. The ADM presented the lowest LOSS (2.8mm; p0.05). Vibration may explain the greater spinal loading involved in CAR and MOT in comparison to the ADM. A GLM analysis revealed that only BMI was the only explanatory factor for stature loss. No independent variables explained RECOV. The ability of the trunk muscles to produce force did not influence LOSS or RECOV between groups. Conclusions: MPOs involved in CAR or MOT patrolling may require greater post-work periods and strategies designed to reduce the weight of the protective apparatus to dissipate spinal loading. The external load used in patrolling is a relevant spinal loading factor.