• International Journal of Advanced Culture Technology
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• v.7 no.1
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• pp.209-215
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• 2019

In order to provide a safe free-weight-training environment to people without workout trainers, we suggest a smart bench press machine with an automatic weight control system sensitive to user tiredness. Physical weight plates on the machine are replaced with a hydraulic cylinder as a press load and the cylinder knob is coupled with a step motor to change its tensile force automatically in-between lifting exercises. Three subjects participated to verify the usability of the smart bench press machine. They were asked to lift a 6-RM press load 10 times with 3 different lifting conditions: 1) no assistance, 2) a human assistance, and 3) the automatic weight control. All subjects were not able to complete the 10 sets without assistance due to tiredness, but they finished the full sets under the two assistive conditions. Average lifting speeds under the automatic weight control condition showed the most consistent level. Normalized quasi-tension data based on surface electromyogram signals of both Pectoralis Majors revealed that the subjects maintained the target muscle activation level above 50% but not more than 80% throughout the 10 sets. Therefore, the smart bench press machine is expected to both keep pace with the lifting exercise and reduce risk of injuries due to excessive muscle tensions.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.119-124
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• 2003

Despite rapid technological advance and increased automation facilities, many jobs and activities in our living require manual materials handling(MMH). These include wide variety of activities such as moving things, lifting bags. boxes or cartons, etc. Many studies found that handle could affect on maximum acceptable weight of lifting, but there were few studies f3r the effects of work posture and coupling in lifting tote box. This study performed that ten male college students were required to lift a tote box with and without handle for three postures (bending, straight, right angle posture). From the experiment, following results were obtained. (1) MVC reduced maximum 23% by type of handle. (2) MVC was highest in straight posture, but was lowest in right angle posture. (3) As a result of ANOVA, MVC paid attention to posture and coupling. (p<0.01) (4) To all handle types, biceps brachii activity was increased in right angle posture. but reduced in straight posture. (5) To all posture, biceps brachii activity was most lively in no handle. The results of MVC measurement, subjective rating, EMG analysis, statistic analysis showed that maximum acceptable weight of lifting was influenced by type of handle and straight posture was more comfortable than other postures. Based on these results, it was concluded that acceptable weight of lifting has to differ for work posture and coupling.

• Journal of the Ergonomics Society of Korea
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• v.25 no.2
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• pp.11-22
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• 2006

The muscular-skeletal disorders(MSDs) that have become a major issue recently in Korean industrial safety area are mainly caused by manual material handling task. The objective of this study is to provide scientific data for the establishment of work safety standard for Korean workers through the experiments of lifting task under various conditions, in order to prevent the muscular-skeletal disorders in the industrial work site. Eight male college students were recruited as participants. Three different lifting frequencies(1, 3, 5 lifts/min) and three twisting angles(including the sagittal plane and two asymmetric angles; i.e., 0°, 45°, 90°) for symmetric and asymmetric tasks, respectively, with three lifting range from floor to knuckle height, knuckle to shoulder, floor to shoulder height for one hour's work shift using free style lifting technique were studied. The maximum acceptable weight of load(MAWL) was determined under the different task conditions, and the oxygen consumption, heart rate, and RPE were measured or recorded while subjects were lifting their MAWLs. The results showed that: (1) The MAWLs were significantly decreased as the task frequency and task angle increased.; (2) The heart rate, oxygen consumption, RPE significantly increased with an increase in lifting frequency although maximum acceptable weight of lift decreased.; (3) The highest heart rate and oxygen consumption was recorded at the lifting range of floor to shoulder, followed by floor to knuckle and knuckle to shoulder.; (4) The RPE value showed that subjects perceived more exertion at the high frequency rate of lifting task and lifting range of floor to shoulder height. (5) The modeling for MAWL using isometric strength, task angle and lifting frequency were developed. It is expected that use of the results provided in this study may prove helpful in reducing MMH hazards, especially from lifting tasks for Korean, and can be used as a basis for pre-employment screening.

• Journal of the Ergonomics Society of Korea
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• v.21 no.1
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• pp.27-32
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• 2002

The objective of this study was to investigate the effects of fatigue, caused by frequent manual lifting. on lifting velocity and lifting acceleration. Ten male volunteers performed lifting at a rate of 4 times per minute, continuously, for two hours using the free-style posture A box($30cm{\times}30cm{\times}20$) with a fixed weight (15.9 Kg) was used as the load for lifting, Heart rate, oxygen consumption, and EMG were also measured to estimate the level of fatigue, The posture as well as acceleration was recorded. The results showed that the lifting acceleration at the end of two hour increased significantly (20%, p<0.001) compared to the acceleration after fifteen minutes of lifting. It was also found that subjects changed their lifting postures as the result of fatigue. All subjects also indicated pain in their upper legs and the lower back at the conclusion of the experiment.

• Proceedings of the ESK Conference
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• 1992.10a
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• pp.18-21
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• 1992

The objective of this study was to investigate the effects of fatigue, caused by frequent manual lifting, on lifting velocity and lifting acceleration. Ten male volunteers performed lifting at a rate of 4 times per minute, continuously, for two hours using the free-style posture. A box $(30cm{\times}30cm{\times}20cm)$ with a fixed weight (15.9kg) was used as the load for lifting. Heart rate, oxygen consumption, and EMG were also measured to estimate the level of fatigue. The posture as well as acceleration was recorded. The results show that the lifting acceleration at the end of two hour increased significantly (20%, p<0.001) compared to the accleration after fifteen minutes of lifting. It was also found that subjects changed their lifting postures as the result of fatigue. All subjects also indicated pain in their upper legs and the lower back at the conclusion of the experiment.

• Journal of Korean Institute of Industrial Engineers
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• v.11 no.2
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• pp.87-99
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• 1985

The purpose of this study is to analyze the changes in centers-of-gravity (COG), acceleration and body posture and their associated effects both on EMG and on the maximum capability of weight lifting during Clean & Jerk and Snatch motions. Displacement, velocity, acceleration of joints were obtained from film analysis. Also levels of exertions on 11 major muscle groups were obtained from EMG analysis during a lifting cycle. The EMG data were measured from Telemetry System which is useful in field experiments. Magnitude and direction of force, change in center-of-gravity were extracted from COG data which were measured from force platform. The results of this study can be to be useful both to coaches and to athletes in weight-lifting.

• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.153-159
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• 2011

The purpose of this study was to develop an innovative training model and method to improve the posture and motion, while pulling up during weight lifting by evaluating the problems of Korean weight lifters performing this motion. To investigate the effectiveness of the new training method substitute members of the Korean national weight lifting team performed both the original pull up technique and new pulling training technique while kinetics and kinematics were recorded. For this study, the first phase of the new training method is more appropriate than the original training with the pull up drop slow deadlift to the knee joint. For the second phase, the new training motion is deemed to be more effective than the current box deadlift motion. Also, this new motion corrects the posture as there is more anterior hip joint motion(about 10 cm) and the knee flexes to about 120 degrees. For the third phase, starting about 10cm above the knee the box snatch high pull up is identified as a more suitable training method. For the forth phase, the box top snatch method is judged to be a more effective training method than the original top snatch training method.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.96-100
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• 2012

Low back pain (LBP) is a major issue in modern industrialized society which is mainly caused by manual material handling (MMH) tasks. The objective of this study was to provide scientific data for establishing work standard for Korean workers throughout the laboratory experiment including some specific lifting tasks. Thirty male college students were recruited as participants. The maximum voluntary contraction (MVC), recommended weight limit (RWL), and psychophysical safety weight using Borg's CR-10 scale were studied. Results showed that the RWL was 8.4% MVC higher than the proposed psychophysical safety weight. Based on this result, it is suggested that the NIOSH lifting equation (NLE) should not be directly applied to Korean without reasonable modifications. The ratio of psychophysical safety weight to MVC was ranged from 20.1 to 26.4%. It is expected that use of the methodology in this study may provide better expectation of the work ability of Korean for reducing lower back pains caused by MMH.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.89-93
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• 2009

The muscular-skeletal disorders that have become a major issue recently in Korean industrial safety area are mainly caused by manual material handling task. The objective of this study is to provide scientific data for the establishment of work safety standard for Korean workers through the experiments of lifting task under various conditions, in order to prevent the muscular-skeletal disorders in the industrial work site. This study used the psychophysical approach to determine the maximum acceptable weight(MAWL) for seven young male subjects, and used isometric and isoinertial strength variables as predictors to develop prediction models. Also, the oxygen consumption, heart rate, and RPE were measured or recorded while subjects were lifting their MAWL. Three different lifting frequencies(1, 3, 5lifts/min) with two lifting range from floor to knuckle height and knuckle to shoulder height for one hour's work shift using free style lifting technique were studied. These results may not only provide scientific data in establishing the safety standards for Korean workers' lifting tasks, but also contribute preventing the rapidly increasing muscular-skeletal disorders lately on the industrial site.

• Korean Journal of Applied Biomechanics
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• v.28 no.4
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• pp.199-205
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• 2018

Objective: The purpose of this study was to examine the effect of increase in barbell weight on closely related variable to the anterior cruciate ligament (ACL) injury which are knee joint kinematics, joint load, joint moment, and maximum load attainment point during snatch of the weight lifting. Method: The subjects of the study were 10 male Korean national weight lifting athletes (69 kg 5, 77 kg 5; age: $21.80{\pm}3.91yrs.$, height: $168.00{\pm}4.06cm$, weight: $75.00{\pm}4.02kg$, career: $7.8{\pm}3.99yrs.$, snatch records: $168{\pm}4.06kg$). The weight of the barbell during the snatch operation was set at 70%, 75% and 80% of the highest records for each subject studied. Results: The result obtained from the one-way repeated measure ANOVA are as follows: With increased barbell weight, the extension moment of the left knee joint was higher in the 80% condition than the 70% (p<.001). However, other variables were not statistically significant difference. According to the factor analysis of the variables related to maximum load attainment point of the ACL major injury variables, the first sub-factor was the internal shear force, the posterior shear force, the abduction moment, and the muscle activity of the VL. The second sub-factor was the extension moment of the knee joint, compressive force, adduction moment, and the third sub-factor was the muscle activity of BF. Conclusion: These results indicate that the possibility of ACL injury can be lowered when performing a stable snatch movement.