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When lifting an object from the ground a person has many possible whole-body movement solutions to accomplish the task. It is unclear why lifters use most of their available lumbar spine flexion range-of-motion despite many ergonomic guidelines advising against doing so. Experimentally restricting spine motion and observing compensatory movement strategies is one approach to address this knowledge gap. A kinematic analysis was performed on 16 participants who completed symmetrical lifting tasks with and without wearing a spine motion-restricting device. Sagittal trunk, lumbar spine, and lower extremity kinematics, along with stance width and foot orientation in the transverse plane were evaluated between restricted and unrestricted lifting conditions. Restricting spine motion required greater ankle dorsiflexion (p < 0.001), knee flexion (p < 0.001), and hip flexion (p < 0.001) motion in comparison to unrestricted lifting. Motion was reallocated such that hip flexion showed the largest increase in restricted lifting, followed by ankle dorsiflexion, then knee flexion compared to unrestricted lifting. Trunk inclination decreased (i.e., more upright) in restricted compared to unrestricted lifting (p < 0.001). Neither stance width (p = 0.163) nor foot orientation (p = 0.228) were affected by restricting spine motion. These adaptive movements observed indicate lower extremity joint motion must be available and controlled to minimize lumbar spine flexion during lifting., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The Turkish Get-Up (TGU) is a complex and multi-planar exercise; the performer begins in a supine lying position, progresses toward upright standing through a series of 7 stages while holding a mass overhead in one hand, and returns to the original supine lying position through a reversal of the same 7 stages. A descriptive analysis of shoulder muscle activity during the TGU may provide insight toward its use in training and rehabilitation contexts. Our objectives were to: (1) describe the activity patterns from a subset of muscles that span the glenohumeral joint during individual stages of the TGU, and (2) interpret these patterns through comparisons between left- and right-side muscles, and between the up and down phases of the TGU. Twelve individuals with at least one-year experience performing the TGU were included in this study. Surface electromyographic (EMG) recordings were bilaterally obtained from 8 glenohumeral muscle groups while participants performed ten trials of the TGU with a kettlebell in their right hand. Instants representing the start and end of each TGU stage were identified from a synchronized video for each trial, and EMG activities for each muscle were integrated over the duration of each stage. Average integrated EMG and within-participant coefficients of variation were calculated. Overall, the greatest muscular demand occurred during the second (press to elbow support) and fifth (leg sweep) stages. Activities from muscles on the ipsilateral side to the kettlebell (right-side) were greater during stages when the contralateral upper limb did not contribute to supporting the body; however, contralateral (left-side) muscles were invoked during stages when the non-kettlebell-bearing forearm or hand contributed to supporting the body. The results suggest the importance of training both phases of the TGU to gain the most benefit from the exercise and highlights the asymmetric nature of the exercise, which may be particularly relevant for athletes engaged in activities with rotational demands., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Estimation of muscle forces through musculoskeletal simulation is important in understanding human movement and injury. Unmatched filter frequencies used to low-pass filter marker and force platform data can create artifacts during inverse dynamics analysis, but their effects on muscle force calculations are unknown. The objective of this study was to determine the effects of filter cutoff frequency on simulation parameters and magnitudes of lower-extremity muscle and resultant joint contact forces during a high-impact maneuver. Eight participants performed a single-leg jump landing. Kinematics was captured with a 3D motion capture system, and ground reaction forces were recorded with a force platform. The marker and force platform data were filtered using 2 matched filter frequencies (10-10 Hz and 15-15 Hz) and 2 unmatched filter frequencies (10-50 Hz and 15-50 Hz). Musculoskeletal simulations using computed muscle control were performed in OpenSim. The results revealed significantly higher peak quadriceps (13%), hamstrings (48%), and gastrocnemius forces (69%) in the unmatched (10-50 Hz and 15-50 Hz) conditions than in the matched (10-10 Hz and 15-15 Hz) conditions (P < .05). Resultant joint contact forces and reserve (nonphysiologic) moments were similarly larger in the unmatched filter categories (P < .05). This study demonstrated that artifacts created from filtering with unmatched filter cutoffs result in altered muscle forces and dynamics that are not physiologic.

Low-back disorder risk can be modulated by pelvis-thorax coordination when lifting. To objectively discriminate between coordination patterns during lifting, the analytical methods used require evaluation. The primary study objective was to determine if continuous relative phase (CRP) and vector coding (VC) analyses can discriminate between lifting techniques that differ based on biomechanical risk criteria. The secondary objective was to determine if normalization/transformation of input segmental angular position and velocity data is required to discriminate between lifting techniques. Sixteen volunteers performed a sagittal lifting task using freestyle (FRE), flexed spine (FLX), and neutral spine (NTL) techniques. CRP and VC analyses were implemented to quantify pelvis-thorax coordination patterns based on time-normalized, phase-normalized, and Hilbert-transformed segmental angular kinematic data. Mean relative phase angles along with thorax-only and in-phase coupling patterns were significantly different between FRE-NTL and FLX-NTL techniques (p < 0.01), but not FRE-FLX (p > 0.44). This finding was consistent across all relative phase normalization/transformation methods. Therefore, CRP and VC analyses successfully discriminated between different lifting techniques, regardless of the relative phase normalization/transformation method used., (Copyright © 2018 Elsevier Ltd. All rights reserved.)