Kinematic contribution and synchronization of the trunk, hip, and knee during free-dynamic lifting (original) (raw)
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Journal of biomechanics, 2015
As torso flexion and repetitive lifting are known risk factors for low back pain and injury, it is important to investigate lifting techniques that might reduce injury during repetitive lifting. By normalizing lumbar posture to a subject's range of motion (ROM), as a function of torso flexion, this research examined when subjects approached their range of motion limits during dynamic lifting tasks. For this study, it was hypothesized that experienced lifters would maintain a more neutral lumbar angle relative to their range of motion, while novice lifters would approach the limits of their lumbar ROM during the extension phase of a straight-leg lift. The results show a statistically significant difference in lifting patterns for these two groups supporting this hypothesis. The novice group maintained a much more kyphotic lumbar angle for both the flexion (74% of the lumbar angle ROM) and extension phases (86% of the lumbar angle ROM) of the lifting cycle, while the experienced g...
Inter- and intra-individual variability in the kinematics of the back squat
Human Movement Science, 2019
The purpose of this study was to explore the level of inter-and intra-individual variability in the kinematic profiles of the back squat movement among skilled weightlifters. Ten competitive weightlifters volunteered for participation in this study. Barbell velocity (V Barbell) and angular velocity of the ankle (ω Ankle), knee (ω Knee) and hip joint (ω Hip) were obtained by kinematic recording of six trials at 90% of 1RM in the back squat. Inter-individual variability was assessed by analysing inter-individual differences in the velocity curves through the statistical parametric mapping method. Intra-individual variability was assessed through a correlation analysis between the barbell velocity curves of each trial for each participant. Partial least squares regression analysis, was performed to relate changes in intra-individual variability to movement and anthropometric characteristics. Significant inter-and intra-individual differences were identified in V Barbell , ω Ankle , ω Knee , and ω Hip (p ≤ 0.05). Having a short trunk and thigh, and a long shin in combination with greater anterior-posterior displacement of the barbell and slower velocities during the acceleration phase increased intra-individual movement consistency over movement variability. The results of the present study clearly demonstrate that skilled weightlifters display both significant inter-and intra-individual variability in the successful execution of the back squat.
2021
Objectives: Because the function of the lower limb joints and the role of the trunk muscles in bearing and lifting loads are important, this study aimed to investigate the intervention of the initial body position when controlling inertia and its effect on the strategy of kinetic patterns in the lower limb joints as well as trunk muscle activity during symmetric lifting.Methods: This experimental study included 10 healthy young man. They were asked to lift an 8.4 Kg box at 3 different knee angles (-10, 35, and 70 degree angle of the thigh to the horizon line) symmetrically and at a constant velocity. The extensor moment and power of lower limb joints were calculated using the 3D linked-segment model (LSM). To measure the muscular activity of abdominal muscles (rectus abdominus (RA) and external oblique (EO)) and lumbar muscles (iliocostalis lumborum (IL) and multifidus (MU)), an 8 channel electromyogram (EMG) were used.Results: The results showed the similarity of extensor moment pa...
2021
Lift‐to‐lift variability occurs in repetitive lifting tasks due to alterations in the lifting techniques used by the lifter, resulting in variability in lower back tissue loading. Understanding how trunk variability changes with time in the initial phases of a lifting bout may provide insights into the risk of injury during work startup. The purpose of this study was to quantify the variation of lifting kinematics and kinetics during the initial phase of a lifting bout. Twenty participants performed a repetitive lifting task continuously for 30 min. The load was equivalent to 10% of each participant's body weight and lifting was done at a rate of six lifts/ min. Kinematic variables (three‐dimensional range of motion, angular velocity, and angular acceleration) of the trunk were measured using the Lumbar Motion Monitor and a dynamic biomechanical model estimated peak L5/S1 moment and spine compression. The variances of these variables were compared across 10‐min intervals: 0–10 m...
Effect of Time on the Variability of Lifting Kinematics in a Repetitive Lifting Task
Proceedings of the Human Factors and Ergonomics Society Annual Meeting
A repetitive lifting task affords the opportunity for lift-to-lift variability in the lifting strategy and kinematics which can result in changes in the stresses on the tissues of the low back. To quantify the variation of lifting kinematics over time, ten subjects were recruited to perform repetitive lifting of a load equal to 10% of body weight at a rate of six lifts/min for 30 minutes continuously. Trunk kinematic variables were measured in all three planes of motion using the Lumbar Motion Monitor. The variances of the lifting kinematics were compared for the following ten-minute intervals: 0-10 min, 10-20 min and 20-30 min. Time was found to have a significant impact on variance of the peak sagittal acceleration, with the variance seen in the first ten minutes exceeding that of the other two time intervals. The downward trend in variation of peak sagittal acceleration implies an initial adjustment as the lifters "settle in" to their preferred lifting strategy.
Horizontal and Declined Squats in Healthy Individuals: A Study of Kinematic and Muscle Patterns
ISRN Rehabilitation, 2013
Squats are frequently incorporated in physiotherapy programmes and performed in different ways. Accordingly, muscle and kinematic patterns also differ. The objective was to compare the kinematics and EMG patterns of the major muscles of knee and ankle joints during different squat exercises on horizontal (HP) and 25 ∘ decline (DP) boards. Seventeen healthy individuals performed squats on HP and DP with bilateral support and restriction of trunk movements in the sagittal plane. The knee and ankle angular displacements in the sagittal plane and the EMG activities of the major muscles of the lower limb in four subphases of movement were recorded and analyzed. For the descending phase of the HP squats, the angular excursion, as well as the initial and final positions, was smaller for the knee ( < 0.05) but larger for the ankle ( = 0.01). For the ascending phase of the HP squats, the initial and final positions were larger for the ankle ( < 0.02) and the final position was smaller for the knee ( = 0.05). All muscles remained activated and showed similarity between the tasks ( > 0.44), except for the tibialis anterior in both squat exercises ( < 0.03). The HP and DP squats produced different kinematics (knee and ankle joints) but did not modify the EMG strategy for both movement phases. of Hindawi Publishing Corporation
Ever since it was first observed and especially so in recent years, the phenomenon of the so-called "sticking point'" in resistance training has attracted a substantial amount of sports and exercise science research. Broadly speaking the sticking point is understood as the position in the range-of-motion of a lift at which a disproportionately large increase in the difficulty to continue the lift is experienced. Hence the sticking point is inherently the performance bottleneck and is also associated with an increased chance of exercise form deterioration or breakdown. Understanding the aspects of lifting performance which should be analysed in order to pinpoint the cause of a specific sticking point and therefore devise an effective training strategy to overcome it, is of pervasive importance to strength practitioners and instrumental for the avoidance of injury and continued progress. In this paper we survey a range of physiological and biomechanical mechanisms which contribute to the development of sticking points, and led by this insight review and analyse the findings of the existing observational research on the occurrence of sticking points in three ubiquitous exercises: the bench press, the squat, and the deadlift. The findings of our analysis should be used to inform future research and current resistance training practice.
Movement Coordination during Functional Single-Leg Squat Tests in Healthy, Recreational Athletes
Symmetry, 2022
The single-leg squat (SLS) represents a functional movement task for determining leg function. Objective movement analysis is required to evaluate inter-limb symmetry and movement coordination. Therefore, this study aimed to investigate inter-limb symmetry of SLS kinematics and movement coordination using the modified vector coding technique. A 3D motion capture system and electromyography were used to assess SLS execution and muscle activation of hip ab- and adductors of 17 healthy, recreational athletes. Coordination patterns of hip, knee, and ankle joint movement were assessed by the modified vector coding technique. Statistical parametric mapping revealed no significant differences between both legs (p > 0.05). Inter-limb symmetry also appeared in movement coordination (p > 0.05). Additionally, the analysis of movement coordination indicates knee-dominant, in-phase coordination. However, coordination patterns were different between downward movement, change of direction, a...