Squat Lifting Research Articles

Biomechanical Analysis to Determine the Most Effective Posture During Squats and Shallow Squats While Lifting Weights in Women

This study aimed to identify the most appropriate squat posture for women by analyzing different squatting methods and weights. Twelve healthy women were recruited as subjects (age: 20.1 ± 1.2 years, height: 163.4 ± 3.7 cm, weight: 57.9 ± 4.9 kg). The 10-camera Vicon MX13 + motion capture system was used to collect squat and shallow squat motion images at 250 Hz sample rate and a Kistler force plate was used to collect ground reaction force at a 1000 Hz sample rate. The two-way ANOVA (α = .05) was applied to assess for significance. The knee joint torque increased as the weight increased (p < .001). The weight affects maximum knee flexion and joint torque during extension, but no difference was found between the squat and shallow squat methods. Greater knee maximum adduction/abduction and internal/external rotation torque were found in squat lifting. The squat and shallow squat had a similar knee loading under the same weight. Shallow squatting yielded better knee stability, which makes it more suitable for the general female population. Squat training was found to be more suitable for well-trained athletes.

Development of Assist Suit for Squat Lifting Support Considering Gait and Quantitative Evaluation by Three-Dimensional Motion Analysis

Globally, lower back pain is a serious problem. For workers, it not only causes health problems but also has social and economic influences. Lower back pain could be attributed to burden on people’s waists when they handle heavy objects. Ministry of Health, Labour and Welfare in Japan recommends squat lifting, a method of lifting objects with a smaller burden on waist. On the other hand, squat lifting is not commonly used because it requires deep bending of knees to lift an object, leading to a larger work load. Therefore, a leaf-spring type power assist suit for legs has been developed in order to assist squat lifting. However, if the fixing performance of a preceding machine was enhanced, a leaf spring could impede the bending of knee joints during gait motion. In the present study, we developed a power assist suit for legs using a slide mechanism. A leaf spring was chosen so as to meet a target assist torque determined by a motion analysis for lifting objects. In addition, we made a prototype machine with slide mechanism. EMG measurement of the thigh muscle during lifting actions using the prototype machine showed a decrease of up to 46%. It was also confirmed that a machine with slide mechanism could realize a more natural gait than a machine without it.

Design and preliminary evaluation of a flexible exoskeleton to assist with lifting.

We present a passive (unpowered) exoskeleton that assists the back during lifting. Our exoskeleton uses carbon fiber beams as the sole means to store energy and return it to the wearer. To motivate the design, we present general requirements for the design of a lifting exoskeleton, including calculating the required torque to support the torso for people of different weights and heights. We compare a number of methods of energy storage for exoskeletons in terms of mass, volume, hysteresis, and cycle life. We then discuss the design of our exoskeleton, and show how the torso assembly leads to balanced forces. We characterize the energy storage in the exoskeleton and the torque it provides during testing with human subjects. Ten participants performed freestyle, stoop, and squat lifts. Custom image processing software was used to extract the curvature of the carbon fiber beams in the exoskeleton to determine the stored energy. During freestyle lifting, it stores an average of 59.3J and provides a peak torque of 71.7Nm.

Finite Element Analysis of L3-L4 Vertebrae at Various Body Postures Under Osteoporotic Condition

The present study gives detailed quantitative information on the biomechanical behavior of osteoporotic vertebra which can be used in the evaluation of osteoporotic bone fracture. A three -dimensional finite element model has been developed and applied for the analysis of the lumbar L3-L4 disc -body unit under various body postures like normal standing, extension, weight lifting, stoop lift and squat lift. The stress and deformation of disc and vertebrae are compared with the corresponding values at 10% and 20% osteoporotic condition. It is observed that for weight lifting, stoop lifting, and squat lift under 20% osteoporotic condition the maximum value of stress obtained is close to compressive strength of the bone. Also noted that fewer than 20% osteoporotic condition the deformation of the disc is increased to 20.08% under weight lifting postures. Therefore,we come to the conclusion that people at old age should avoid risky postures which result in low back pain or lumbar fracture.

Determination of Joint Load of Human Lower Limb by Using 2D Inverse Dynamics Modelling

The human lower limb is a major part of the human body that is exposed to high joint load during daily activities. Different lifestyles and cultural activities can affect the loading condition generated at the joint during motion. For instance, deep squatting is more frequently performed by Asians compared to Europeans e.g. kneeing on tatami among Japanese and sitting position during prayer among Muslims. The aim of this research is to determine the joint load of the human lower limb during the squat lifting movement by using inverse dynamics of 2-dimensional (2D) human lower limb model. The 2D inverse dynamics modelling was used to describe and compute all the joint force reactions from the known ground reaction and lower limb kinematics. In this study, 2D human lower limb model was analysed during the squat lifting movement. Inverse dynamics computation was performed using MATLAB programming based on Newton-Euler equations to determine the joint forces and moments. The joint loads at ankle, knee and hip joints for every knee flexion angle were obtained and the maximum forces at the ankle, knee and hip were 613.9, 614.1 and 596.1 N, respectively.

Squat Lifting Imposes Higher Peak Joint and Muscle Loading Compared to Stoop Lifting

(1) Background: Yearly, more than 40% of the European employees suffer from work-related musculoskeletal disorders. Still, ergonomic guidelines defining optimal lifting techniques to decrease work-related musculoskeletal disorders (WMSDs) has not been unambiguously defined. Therefore, this study investigates if recommended squat lifting imposes lower musculoskeletal loading than stoop lifting while using a complex full body musculoskeletal OpenSim model. (2) Methods: Ten healthy participants lifted two different weights using both lifting techniques. 3D marker trajectories and ground reaction forces were used as input to calculate joint angles, moments and power using a full body musculoskeletal model with articulated lumbar spine. In addition, the muscle activity of nine different muscles was measured to investigate muscle effort when lifting. (3) Results: Peak moments and peak joint power in L5S1 were not different between the squat and the stoop, but higher peak moments and peak power in the hip, knee, elbow and shoulder were found during squat lifting. Moment impulses in L5S1 were higher during stoop lifting. This is reflected in higher peak electromyography (EMG) but lower muscle effort in prior described muscles during the squat. (4) Conclusions: Squat lifting imposes higher peak full body musculoskeletal loading but similar low back loading compared to stoop lifting, as reflected in peak moments, peak power, and peak EMG.

Squat lifting imposes higher full body musculoskeletal loading compared to stoop lifting.

Squat lifting imposes higher full body musculoskeletal loading compared to stoop lifting.

Classification of Lifting Techniques for Application of A Robotic Hip Exoskeleton.

The number of exoskeletons providing load-lifting assistance has significantly increased over the last decade. In this field, to take full advantage of active exoskeletons and provide appropriate assistance to users, it is essential to develop control systems that are able to reliably recognize and classify the users’ movement when performing various lifting tasks. To this end, the movement-decoding algorithm should work robustly with different users and recognize different lifting techniques. Currently, there are no studies presenting methods to classify different lifting techniques in real time for applications with lumbar exoskeletons. We designed a real-time two-step algorithm for a portable hip exoskeleton that can detect the onset of the lifting movement and classify the technique used to accomplish the lift, using only the exoskeleton-embedded sensors. To evaluate the performance of the proposed algorithm, 15 healthy male subjects participated in two experimental sessions in which they were asked to perform lifting tasks using four different techniques (namely, squat lifting, stoop lifting, left-asymmetric lifting, and right-asymmetric lifting) while wearing an active hip exoskeleton. Five classes (the four lifting techniques plus the class “no lift”) were defined for the classification model, which is based on a set of rules (first step) and a pattern recognition algorithm (second step). Leave-one-subject-out cross-validation showed a recognition accuracy of 99.34 ± 0.85%, and the onset of the lift movement was detected within the first 121 to 166 ms of movement.

Proposal of lower limb power assist suit for Squat Lifting considering walking

Proposal of lower limb power assist suit for Squat Lifting considering walking

Modeling the Multi-Dimensional Phenomenon of Fatiguing by Assessing the Perceived Whole Body Fatigue and Local Muscle Fatigue During Squat Lifting

Whole body fatigue detection is an important phenomenon and the factors contributing to whole body fatigue can be controlled if a mathematical model is available for its assessment. This research study aims at developing a model that categorizes whole body exertion into fatigued and non-fatigued states based on physiological and perceived variables. For this purpose, logistic regression was used to categorize the fatigued and non-fatigued subject as dichotomous variable. Normalized mean power frequency of eight muscles from 25 subjects was taken as physiological variable along with the heart rate while Borg scale ratings were taken as perceived variables. The logit function was used to develop the logistic regression model. The coefficients of all the variables were found and significance level was checked. The detection accuracy of the model for fatigued and non-fatigues subjects was 83% and 95% respectively. It was observed that the mean power frequency of anterior deltoid and the Borg scale ratings of upper and lower extremities were significant in predicting the whole body fatigued when evaluated dichotomously (p < 0.05). The findings can help in better understanding of the importance of combined physiological and perceived exertion in designing the rest breaks for workers involved in squat lifting tasks in industrial as well as health sectors.

Proposal of Non-Rotating Joint Drive Type Power Assist Suit for Lower Limbs Considering Squat Lifting

Lower back pain is a major health concern worldwide. One cause of lower back pain is the burden on the lumbar region caused by handling heavy objects. The Ministry of Health, Labour and Welfare in Japan has recommended “squat lifting” to reduce this burden. However, this technique, which supports a large force on the lower limbs, is not very popular. Therefore, we aim to develop a power assist suit for squat lifting and propose herein a gastrocnemius-reinforcing mechanism. We also discuss the joint torque estimation from a motion analysis of squat lifting to construct a prototype. Finally, we describe the performance of the prototype when mounted on a human body. We found that when using the prototype assist suit, the %MVC (maximum voluntary contraction) of the gastrocnemius while performing squat lifting reduced by 48% compared to the value obtained without using the suit.

An evaluation of the inter-rater and intra-rater reliability of OccuPro's functional capacity evaluation.

BACKGROUND:OccuPro’s functional capacity evaluation (FCE) is used for assessing the client’s readiness to return to work and three separate intra-rater and inter-rater reliability studies are explored here.OBJECTIVE:Three separate studies were conducted on injured and un-injured adults to evaluate the inter-rater and intra-rater reliability of the OccuPro FCE (upper extremity and material handling subtests). All three studies are summarized in this publication.METHODS:In study one, twenty participants completed firm grasp, simple grasp, pinch, fine motor, and gross motor testing. The participants included subjects with an orthopedic or musculoskeletal disorder affecting the upper extremities. In study two and three, 62 participants completed occasional squat lifts, occasional power lifts, occasional carrying, frequent squat lifts, frequent power lifts, and frequent carrying. The participants in all three studies were adult subjects between 20 and 70 years of age. Study one subjects had a previous illness or injury while subjects in study two and three had no history of injury.RESULTS:Results from study one showed that the OccuPro FCE’s four upper extremity subtests have moderate to excellent inter-rater reliability. In study two and three, results showed that the intra-rater reliability of these subtests were excellent and the inter-reliability of these subtests were moderate to good.CONCLUSIONS:These three studies establish inter-rater and intra-rater reliability for the four upper extremity subtests and material handling testing within the OccuPro FCE system. This allows for multiple therapists to use OccuPro’s FCE system with the same patient or multiple patients while having the confidence they will achieve consistent results and make sound return-to work or residual functional capacity decisions.

Variation in lifting kinematics related to individual intrinsic lumbar curvature: an investigation in healthy adults

ObjectiveLifting postures are frequently implicated in back pain. We previously related responses to a static load with intrinsic spine shape, and here we investigate the role of lumbar spine shape...

Elongation of the surface of the spine during lifting and lowering, and implications for design of an upper body industrial exoskeleton

The aim of this study was to assess the elongation of the skin surface of the spine for simulated industrial lifting and lowering tasks to aid the design of industrial exoskeletons worn on the back. Eighteen male participants lifted and lowered a box of varying loads (5 kg, 10 kg, 15 kg) using three techniques (squat, semi-squat, stooped) from the ground to a table. Motion capture sensors attached to the spine from C7 to S1 measured movement. Stoop lifting involved significantly more elongation (mean 71.1 mm; margin of error ±6.9) than squat lifting (mean 36.8 mm; margin of error ±6.9). Load and Task (lift vs. lower) did not have a significant effect on elongation. Elongation of the skin surface of the lumbar spine was greater than for the thoracic spine. These data detail example levels of elongation of the skin surface of the spine, which should be considered in upper body wearable industrial exoskeleton design. Further, exoskeleton design should take into account that the skin surface of the lumbar spine involves greater elongation than the skin surface of the thoracic spine during deep lifting.

Assessment of Whole Body and Local Muscle Fatigue Using Electromyography and a Perceived Exertion Scale for Squat Lifting.

This research study aims at addressing the paradigm of whole body fatigue and local muscle fatigue detection for squat lifting. For this purpose, a comparison was made between perceived exertion with the heart rate and normalized mean power frequency (NMPF) of eight major muscles. The sample consisted of 25 healthy males (age: 30 ± 2.2 years). Borg’s CR-10 scale was used for perceived exertion for two segments of the body (lower and upper) and the whole body. The lower extremity of the body was observed to be dominant compared to the upper and whole body in perceived response. First mode of principal component analysis (PCA) was obtained through the covariance matrix for the eight muscles for 25 subjects for NMPF of eight muscles. The diagonal entries in the covariance matrix were observed for each muscle. The muscle with the highest absolute magnitude was observed across all the 25 subjects. The medial deltoid and the rectus femoris muscles were observed to have the highest frequency for each PCA across 25 subjects. The rectus femoris, having the highest counts in all subjects, validated that the lower extremity dominates the sense of whole body fatigue during squat lifting. The findings revealed that it is significant to take into account the relation between perceived and measured effort that can help prevent musculoskeletal disorders in repetitive occupational tasks.

Design and Evaluation of Passively Powered Knee Exoskeleton (PPKE) for Squat Lifting

Design and Evaluation of Passively Powered Knee Exoskeleton (PPKE) for Squat Lifting

Development of A Passively Powered Knee Exoskeleton for Squat Lifting

Development of A Passively Powered Knee Exoskeleton for Squat Lifting

The Influence of External Load on Quadriceps Muscle and Tendon Dynamics during Jumping.

The influence of external loading on muscle and tendon dynamics during maximal vertical jumping was explored. Ten resistance-trained men performed parallel-depth, countermovement vertical jumps with and without additional load (0%, 30%, 60%, and 90% of maximum squat lift strength), while joint kinetics and kinematics, quadriceps tendon length (LT) and patellar tendon FT and RFDT were estimated using integrated ultrasound, motion analysis and force platform data and muscle tendon modelling. Estimated FT and RFDT, but not peak LT, increased with external loading. Temporal comparisons between 0% and 90% loads revealed that FT was greater with 90% loading throughout the majority of the movement (11%-81% and 87%-95% movement duration). However, RFDT was greater with 90% load only during the early movement initiation phase (8%-15% movement duration) but was greater in the 0% load condition later in the eccentric phase (27%-38% movement duration). LT was longer during the early movement (12%-23% movement duration) but shorter in the late eccentric and early concentric phases (48%-55% movement duration) with 90% load. External loading positively influenced peak FT and RFDT but tendon strain appeared unaffected, suggesting no additive effect of external loading on patellar tendon lengthening during human jumping. Temporal analysis revealed that external loading resulted in a large initial RFDT that may have caused dynamic stiffening of the tendon and attenuated tendon strain throughout the movement. These results suggest that external loading influences tendon lengthening in both a load- and movement-dependent manner.

The effects of task execution variables on resultant vertical ground reaction force acting on foot sole during squat lifting

The main objective of this study was to investigate the effects of task execution variables on the value and point of application of the resultant vertical ground reaction force acting on the foot sole during squat lifting. This can be of particular importance since it may help to recognize the roles of the foot sole parts in bearing the support force during industrial and labor lifting activities. Twelve healthy men lifted a box with 4, 8 and 12 kg masses at fast and slow speeds. Ground reaction force and center of pressure were measured using two parallel Kistler force-plates. In addition, a Vicon system and a 3D linked segment model were used to define the movement pattern. Significant increases resulted for the peak vertical ground reaction force with the increases in the lift speed (P < 0.05) and box weight (P < 0.05). As well a significant increase resulted for the range of center of pressure location with the increase in the box weight (P < 0.05). Moreover, significant interactions (P < 0.05) between the lift speed and box weight were detected. The front and rear parts of the foot had the most important roles in bearing the support force during the beginning and final phases of movement, respectively. Finally, it was concluded that the value and point of application of vertical ground reaction force are seemingly dependent on the momentum of the subject plus box.

U.S. Army Physical Demands Study: Development of the Occupational Physical Assessment Test for Combat Arms soldiers

ObjectivesThe United States Army sought to create a legally defensible, scientifically validated physical pre-employment screening test. The purpose of this study was to identify a single combination of predictor tests that would predict physical performance on all of the criterion measure task simulations relevant to the Combat Arms military occupational specialties. DesignConcurrent validation. MethodsData from 838 (608 males, 230 females) soldiers who completed both the criterion measure task simulations of a military occupational specialty and up to 14 predictor tests were used in the development of the test batteries. Stepwise regressions were used to identify test batteries that significantly predicted performance on the criterion measure task simulations of the military occupational specialties. ResultsThree test batteries were developed based on different subsets of the predictor tests: Test Battery 1 consisted of the medicine ball put, squat lift, beep test, standing long jump, and arm ergometer (adjusted R2=0.80–0.85, p<0.01); Test Battery 2 consisted of the medicine ball put, squat lift, beep test, and standing long jump (adjusted R2=0.79–0.80, p<0.01); and Test Battery 3 consisted of the standing long jump, 1-minute push-ups, 1-minute sit-ups, 300m sprint, and Illinois agility test (adjusted R2=0.55–0.71, p<0.01). ConclusionsTest Battery 2 was selected as the Army’s Occupational Physical Assessment Test. It was highly predictive of performance of the Combat Arms military occupational specialties, required no complex equipment, and covered a range of physical fitness domains.