(71) RELIABILITY AND VALIDITY OF A NOVEL OVERHEAD LOAD CARRIAGE AND POSTURAL INTEGRITY SCREEN FOR TACTICAL PERSONNEL

Purpose: Determine the reliability and validity a novel overhead carry screen to comprehensively assess overhead load carrying capacity and postural integrity. Methods: Seventeen male (n=11) and female (n=6) resistance trained ( >2 yrs of 3d/wk) subjects with substantial overhead loading experience (Mean ±SD: 23.3±3.3yrs, 78.0±12.8kg, 175.5±9.3cm, 21.4±6.6%BF) completed common upper body tests of muscular strength and loaded carriage to advise development of a novel overhead carry screen (OCS). Subjects were screened for acceptable glenohumeral and scapulothoracic asymmetries, limitations, and neuromuscular control prior to formal study inclusion. Subjects conducted 4 separate testing sessions with protocol familiarization and standardized arrival conditions. Upper body muscular strength endurance was evaluated via 10-repetition maximum (10-RM) bench press (BP) and overhead press (OHP) protocols involving 3 warm-up sets and a maximum of 3 working sets with 3-min inter-set rest to achieve a 10-RM. Relative load ratios (OHP/BW and OHP/BP) were calculated using the resulting 10-RM loads to determine OCS carriage load. The OCS protocol incorporated the Fundamental Capacity Carry Screen (FCS) setup, requiring subjects to walk around a 25ft figure 8 course for maximal distance and time while maintaining standardized postural characteristics. The FCS required one trial of a maximal effort suitcase-carry with 75% BW load in 2 sandbags (37.5% BW/limb). The OCS protocol employed 75% of the two different load ratio iterations in random order using a single sandbag held longitudinally in a fully extended position overhead and full (10-min) inter-set recovery. Criterion validity of both OCS load variations was calculated via Pearson correlation with common BP, OHP, and FCS outcomes as standards. Test-retest reliability, calculated via intraclass correlation coefficient (ICC), was conducted across three trials in the last session using the SB load iteration with the highest validity. Results: Calculation of load carriage ratio iterations using common upper body strength tests resulted in feasible %BW loads of 39% (OHP/BW) and 47% (OHP/BP) for the two OCS trials. OHP relative load lifted demonstrated a large correlation with carriage distance (cDIST) of both OCS load iterations (39%BW: r=0.40, 47%BW: r=0.41). The calculated OHP/BP load ratio also exhibited large correlations with OCS 47%BW load cDIST (r=0.40), carry load (cLOAD, r=0.39), and carry time (cTIME, r=0.51). OCS and FCS outcomes were poorly (r< 0.10) correlated. The 47%BW OCS protocol revealed good test-retest reliability via ICC for cTIME (0.90, 95% CI: 0.80-0.96) and cLOAD (0.87, 95% CI: 0.74-0.95), but poor reliability for cDIST (0.25, 95% CI: -0.02-0.57). Conclusions: While the two OCS load iterations were devised based on common and validated measures of upper body musculoskeletal strength, conducting the OCS with 47%BW load facilitated a more robust outcome correlation with two common strength metrics. Further, total carry time and carriage load should be used as viable OCS outcomes compared to total carry distance based on the repeatability of results. Practical Applications: To maximize tactical operator safety, durability, and longevity, this novel OCS protocol may serve as an effective pre-training screening tool to identify load-based shoulder girdle and torso dysfunction in upright posture likely to be exacerbated by and compromised in scenarios of compounding training density. Acknowledgements: None.