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Orr, RM, Robinson, J, Hasanki, K, Talaber, KA, Schram, B, and Roberts, A. The relationship between strength measures and task performance in specialist tactical police. J Strength Cond Res 36(3): 757-762, 2022-Specialist tactical police officers (STPOs) carry heavier on-body loads than generalist police officers. Improvements in strength may mitigate the impacts of these heavier loads. The aim of this investigation was to determine the correlations between absolute and relative strength measures and occupational task performance in STPOs. Retrospective data were provided for 47 male specialist police officers from an elite Australian police unit. Data included body mass (mean = 89.0 ± 8.58 kg), strength measures (1 repetition maximum measures for a bench press, squat, deadlift, and pull-up), and task performance measures (85-kg victim drag wearing 15 kg of operational load and 5-km pack march wearing 40 kg of operational load). Pearson's correlations were conducted to determine relationships between measures and were plotted on a linear regressions model. Significant, moderate to strong correlations were found between all strength measures and victim drag performance and significant negative moderate correlations between relative bench press, absolute and relative squat, and absolute and relative pull-up and pack march times. The absolute deadlift had the strongest correlation to the victim drag (r = 0.747, p0.01) while the relative pull-up showed the strongest correlation with pack march performance (r = -0.466, p0.01). The requirement to lift a portion of the dummy off the ground during the victim drag may explain the increased importance of absolute strength while the requirement to transport load affixed to the body may explain the importance of relative strength requirements. Improvements in absolute and relative upper- and lower-body strength may improve task performance in this population.

The Microsoft Xbox One Kinect™ (Kinect V2) contains a depth camera that can be used to manually identify anatomical landmark positions in three-dimensions independent of the standard skeletal tracking, and therefore has potential for low-cost, time-efficient three-dimensional movement analysis (3DMA). This study examined inter-session reliability and concurrent validity of the Kinect V2 for the assessment of coronal and sagittal plane kinematics for the trunk, hip and knee during single leg squats (SLS) and drop vertical jumps (DVJ). Thirty young, healthy participants (age = 23 ± 5yrs, male/female = 15/15) performed a SLS and DVJ protocol that was recorded concurrently by the Kinect V2 and 3DMA during two sessions, one week apart. The Kinect V2 demonstrated good to excellent reliability for all SLS and DVJ variables (ICC ≥ 0.73). Concurrent validity ranged from poor to excellent (ICC = 0.02 to 0.98) during the SLS task, although trunk, hip and knee flexion and two-dimensional measures of knee abduction and frontal plane projection angle all demonstrated good to excellent validity (ICC ≥ 0.80). Concurrent validity for the DVJ task was typically worse, with only two variables exceeding ICC = 0.75 (trunk and hip flexion). These findings indicate that the Kinect V2 may have potential for large-scale screening for ACL injury risk, however future prospective research is required.

The Microsoft Kinect V2 for Windows™, also known as the Xbox One Kinect, includes new and potentially far improved depth and image sensors which may increase its accuracy for assessing postural control and balance. The aim of this study was to assess the concurrent validity and reliability of kinematic data recorded using a marker-based three dimensional motion analysis (3DMA) system and the Kinect V2 during a variety of static and dynamic balance assessments. Thirty healthy adults performed two sessions, separated by one week, consisting of static standing balance tests under different visual (eyes open vs. closed) and supportive (single limb vs. double limb) conditions, and dynamic balance tests consisting of forward and lateral reach and an assessment of limits of stability. Marker coordinate and joint angle data were concurrently recorded using the Kinect V2 skeletal tracking algorithm and the 3DMA system. Task-specific outcome measures from each system on Day 1 and 2 were compared. Concurrent validity of trunk angle data during the dynamic tasks and anterior–posterior range and path length in the static balance tasks was excellent (Pearson's r > 0.75). In contrast, concurrent validity for medial–lateral range and path length was poor to modest for all trials except single leg eyes closed balance. Within device test–retest reliability was variable; however, the results were generally comparable between devices. In conclusion, the Kinect V2 has the potential to be used as a reliable and valid tool for the assessment of some aspects of balance performance.