• Journal of Korean Medicine Rehabilitation
• /
• v.28 no.2
• /
• pp.105-111
• /
• 2018

Objectives The purpose of this study was to examine the effects muscle fatigue at the knee muscles on balance during standing in healthy adults. Methods Thirty healthy adults were recruited along with their written informed consent. Subjects were randomly assigned to knee extensor group (fatigue on knee extensor, KE), and knee flexor group (fatigue on knee flexor, KF). And subjects performed exercise with each muscle group until muscle fatigue was induced. They were assessed balance ability by functional reaching test (FRT), limit of stability (LOS), and postural sway (one leg standing, normal eye open (NO), normal eye close (NC), pillow with eye open (FO), and pillow with eye close (FC)) before and after fatigue. Results There were significant group differences balance performances in FRT, anterior of limit of stability, one leg standing, and the muscle fatigue of knee muscles were decreased balance performances. The balance performance was affected by visual sense and proprioception. Conclusions These results show that the muscle fatigue of knee muscles decreased balance performance. Therefore, balance exercise program should be trained without muscle fatigue.

• Journal of Korean Institute of Industrial Engineers
• /
• v.33 no.1
• /
• pp.44-51
• /
• 2007

The purpose of this study was to identify the relationship between the cumulative fatigue of trunk muscles andthe period of recovery time during repetitive lifting and lowering tasks with symmetric and asymmetric postures.Ten subjects participated in the experiment. Subjects had 1, 2, 3, 4 and 5 minutes recovery time respectivelywhile they were performing the lifting and lowering task repeatedly for 3 minutes with the weight equivalent to25% level of MVC. EMG signals from ten trunk muscles were collected and the fatigue level was analyzedquantitatively. In results, the local muscle fatigue was no longer accumulated when 5 minutes recovery time wasgiven in symmetric position. For asymmetric position, it took longer minutes to prevent the fatigue accumul-ation. Different trunk muscles indicated slightly different recovery patterns in terms of MPF (Mean Powerfrequency) value.This result would help ergonomist design the length of recovery time to control the cumulative fatigue of trunkmuscles in industry with repetitive lifting and lowering task.

• Physical Therapy Korea
• /
• v.26 no.2
• /
• pp.16-23
• /
• 2019

Background: High-heeled shoes can change spinal alignment and feet movement, which leads to muscle fatigue and discomfort in lumbopelvic region, legs, and feet while walking. Objects: This study aimed to identify the effects of different shoe heel heights on the walking velocity and electromyographic (EMG) activities of the lower leg muscles during short- and long-distance walking in young females. Methods: Fifteen young females were recruited in this study. The experiments were performed with the following two different shoe heel heights: 0 cm and 7 cm. All participants underwent an electromyographic procedure to measure the activities and fatigue levels of the tibialis anterior (TA), medial gastrocnemius (MG), rectus femoris (RF), and hamstring muscles with each heel height during both short- and long-distance walking. The walking velocities were measured using the short-distance (10-m walk) and long-distance (6-min walk) walking tests. Results: Significant interaction effects were found between heel height and walking distance conditions for the EMG activities and fatigue levels of TA and MG muscles, and walking velocity (p<.05). The walking velocity and activities of the TA, MG, and RF muscles appeared to be significantly different between the 0 cm and 7 cm heel heights during both short- and long-distance walking (p<.05). Significant difference in the fatigue level of the MG muscle were found between the 0 cm and 7 cm heel heights during long-distance walking. In addition, walking velocity and the fatigue level of the MG muscle at the 7 cm heel height revealed significant differences in the comparison of short- and long-distance walking (p<.05). Conclusion: These findings indicate that higher shoe heel height leads to a decrease in the walking velocity and an increase in the activity and fatigue level of the lower leg muscles, particularly during long-distance walking.

• Journal of the Ergonomics Society of Korea
• /
• v.25 no.2
• /
• pp.197-204
• /
• 2006

The purpose of this study was to investigate the relationship between the cumulative fatigue of trunk muscles and the period of recovery time during repetitive lifting and lowering task with two different frequencies(4 times/min and 6 times/ min). Eight healthy males with no prior history of LBD(low back disorders) volunteered for this study. Subjects had 2, 3, 4, and 5 minutes recovery time respectively while they were preforming the lifting and lowering task at 15% level of MVC. EMG signals from six trunk muscles were collected and the fatigue level was analyzed quantitatively. In results, the fatigue levels of LES(left elector spinae), RLD(right lattissimus dorsi), LLD(left lattissimus dorsi), RRA(right rectus abdominis) and LRA(left rectus abdominis) were recovered when 3 minutes recovery time was given at 4 times/min frequency. However, the fatgue level of RES(right elector spinae) was recovered when 4 minutes recovery was given. On the other hand, when 6 times/min frequency was used, the RLD, LLD, RRA and LRA were recovered at 5 minutes of recovery time. But for RES and LES, it took longer than 5 minutes to be recovered. This results can be applied to design the adequate length of recovery time to control the cumulative fatigue of trunk muscles in industry with repetitive lifting and lowering task.

• Journal of International Academy of Physical Therapy Research
• /
• v.9 no.2
• /
• pp.1498-1507
• /
• 2018

The purpose of this study was to examine the immediate effect of neck stabilization exercise and Swiss ball exercise on the recovery from the fatigue of neck muscles induced. The turtleneck posture was set artificially by using Smartphone with healthy adults. Repetitively measured ANOVA was executed to examine the changes in the muscle fatigue of sternocleidomastoid, upper trapezius, and splenius capitis among three-time intervals (at the time of general resting, work and after intervention) in the three intervention groups (neck stabilization exercise group, Swiss ball exercise group, and ordinary rest group). There were no significant differences in the changes of fatigue of sternocleidomastoid muscle among all three intervention groups at the time of general resting, work and after intervention (p>.05). Although there was no significant difference in the changes in the fatigue of upper trapezius and splenius capitis muscles between the intervention groups at the time of general resting and work (p>.05), there was the significant difference between the three intervention groups at the time of work and after intervention (p>.05). This study suggest that Swiss ball exercise is more effective in reducing the muscular fatigue of the neck and shoulder at a turtleneck posture than neck stabilization exercise.

• Physical Therapy Korea
• /
• v.5 no.3
• /
• pp.63-71
• /
• 1998

Trunk holding test (Sorensen test) appear to have more value than strength test in prediction the occurrence of low back pain. Electromyographic activity of trunk extensor muscles during these test may provide clues to the etiology of neuromuscular-based low back pain. This study investigated the difference in back muscle endurance between healthy adult men and women using surface electromyographic (EMG) power spectral analysis. Thirty hea1thy subjects (15 men and 15 women) performed an unsupported trunk holding test for 60 seconds. Recording surface electrodes were placed over the erector spinae medially and laterally at vertebral levels of $L_1$ and $L_5$. Slope of total frequency was evaluated using the MP100WSW Fast Fourier Transform spectrum analysis program. The slopes of all indices of back muscle fatigue, except right $L_5$, were significantly steeper in men than in women (p<0.05). Our results indicated that the trunk holding test using EMG power spectral analysis of erector spinae muscles is useful for the evaluation of fatigue rate of these muscles. Our results also showed a higher muscle endurance in healthy adult women than in men.

• Physical Therapy Korea
• /
• v.16 no.3
• /
• pp.16-23
• /
• 2009

The purpose of this study was to investigate the effects of a repetitive lifting task on the level of activation and median frequency of the paraspinal muscles, and to provide basic data of the maximal acceptable duration of the lifting task to avoid muscle fatigue. Ten healthy male subjects were recruited as participants and they repetitively (12 lifts/min) lifted a box ($46cm{\times}30cm{\times}30cm$, 15 kg) for 10 minutes. Electromyographic data (muscle activation and median frequency), heart rate, and Borg CR10 score were recorded at 1, 3, 5, 7, and 9 minutes after the lifting task. Electromyographic data was recorded from the elector spinalis, mutifidus, external oblique abdominis, and rectus abdominis for 1 minute. The results showed that as the repetitive lifting task progressed, the heart rate and Borg CR10 score significantly increased. In addition, activation of the muscles increased. The median frequency significantly decreased over time in the elector spinalis, mutifidus, and external oblique abdominis (right side), except for the external oblique abdominis (left side) and rectus abdominis. It is suggested that the median frequency recorded from a dynamic task is used to monitor muscle fatigue. Furthermore, the repetitive lifting task (15 kg, 12 lifts/min) should not continue for more than 3 minutes in order to avoid muscle fatigue.

• Journal of the Ergonomics Society of Korea
• /
• v.27 no.3
• /
• pp.15-22
• /
• 2008

The purpose of this study was to define the effects of noise and background music on the trunk muscle fatigue during dynamic lifting and lowering tasks. Six healthy male subjects with no prior history of low back disorders participated in this study. The participants were exposed to two levels of background noise such as 40dB noise and 90dB noise and three levels of background music such as no music, slow music, and fast music. Six different combinations of background noise and background music were played while the participants were performing the lifting task at 15% level of Maximum Voluntary Contraction. Electromyography signals from six muscles were collected and fatigue levels were analyzed quantitatively. In results, the 90dB noise increased trunk muscle fatigue and slowed down the recovery. The trunk muscle fatigue was the lowest when the fast music was played for as background. After recovery, the 90dB noise increased trunk muscle fatigue. The trunk muscle fatigue was the lowest when the slow music was played for as background. The results can be useful to manage the cumulative fatigue of trunk muscles due to background noise and music during repetitive lifting and lowering tasks in industry.

• Journal of the Korean Society of Physical Medicine
• /
• v.14 no.4
• /
• pp.93-101
• /
• 2019

PURPOSE: This study tries attempted to provide basic clinical data to reduce pain and improve function by comparing the muscle fatigue of the superficial neck muscles and neck disability index (NDI) by performing McKenzie exercise or passive stretching exercise for chronic neck pain patients. METHODS: Sixteen chronic neck pain patients were selected and divided into the McKenzie group (n=8) and passive stretching group (n=8). The intervention program was performed three times a week for four weeks. The time for one exercise was 30 minutes. Before the intervention, the muscle fatigue the superficial neck muscles and NDI were measured. They were measured again after four weeks using the same method. RESULTS: The median frequency of the superficial neck muscles increased significantly in the McKenzie group and passive stretching group (p<.05). The NDI of both the McKenzie group and the passive stretching group decreased significantly. A comparison of the groups, revealed a significant difference in only the median frequency values of the upper trapezius muscle and splenius capitis muscle (p<.05). The NDI values of both groups were similar. CONCLUSION: Both McKenzie exercise and passive stretching exercises showed a significant difference in the degree of fatigue and NDI. McKenzie exercise delayed the replace of the fast twitch fibers which helped improve the muscle fatigue of the upper trapezius muscle and splenius capitis muscle. On the other hand, additional studies applying more variables for the muscle function to improve the symptom of chronic neck pain patients will be needed.

• Physical Therapy Korea
• /
• v.6 no.2
• /
• pp.16-31
• /
• 1999

The purpose of this study was to assess the fatigue in lumbar and abdominal muscles in patients with chronic low back pain compared with normal subjects using spectral analysis with mean power frequency and median power frequency. The experimental group consisted of twenty subjects who had experienced chronic low back pain for over one year after the onset day. A control group consisted of twenty normal subjects with no history of low back pain. All subjects stood in an apparatus to perform sustained contraction in the lumbar and abdominal muscles for 30 seconds with 60% maximal voluntary isometric contraction (MVIC). The resulting electromyographic (EMG) recorded time serial data were transformed into frequency serial data by Fast Fourier Transformation (FFT). The results were as follows: 1) lumbar muscles measured, the frequency change ratio of both median power frequency and mean power frequency was significantly greater for experimental group compared with control group group (p<0.05). In measured two abdominal muscles (inferior rectus abdominis, obliquus externus abdominis) except superior rectus abdominis, the frequency change ratio of both median power frequency and mean power frequency was significantly greater for experimental group compared with control group (p<0.05). 2) In all three (longissimus thoracis, iliocostalis lumborum, multifidus) lumbar muscles measured, the initial frequency value of both median power frequency and mean power frequency was significantly lower for the experimental group compared with the control group (p<0.05). In the two (inferior rectus abdominis, obliquus externus abdominis) abdominal muscles measured (superior rectus abdominis not included), the initial frequency value of both median power frequency and mean power frequency was significantly lower for the experimental group compared with the control group (p<0.05). These results suggest that in patients with chronic low back pain there is a trend for more fatigue to occur in both lumbar and abdominal muscles than in the normal control group. This would seem to suggest that in treatment programs for patients with chronic low back pain, improvement of endurance in all trunk muscles should be considered.