Background: Forward head posture affects many individuals and can cause pain and dysfunction in the muscles and joints of the head, neck, and shoulders. Objectives: This study aimed to assess muscle activity and onset time of cervical and scapular muscles during 180° shoulder flexion and abduction in individuals with normal head posture (NHP) and in those with forward head posture (FHP), both before and after correction. Design: Cross-sectional study. Methods: Thirty-six individuals were divided into FHP and NHP groups. Muscle activity and muscle contraction onset time of the splenius capitis, sternocleidomastoid, upper middle and lower trapezius, and serratus anterior muscles were measured during shoulder flexion and abduction using wireless surface electromyography. Results: The FHP group exhibited increased muscle activity compared to the NHP group (P<.05), notably in the sternocleidomastoid and middle trapezius muscles, more so during shoulder abduction than flexion (P<.05). Regarding muscle contraction onset time, sternocleidomastoid onset was fastest during shoulder abduction in the FHP group (P<.05), while serratus anterior onset was slowest during both shoulder abduction and flexion (P<.05). Conclusion: These findings highlight distinct muscle activity and muscle contraction onset time patterns based on head posture and shoulder movement. Selective muscle activation strategies may help reduce heightened sternocleidomastoid and trapezius activity and enhance serratus anterior engagement in individuals with FHP.

Sensors for monitoring human body movements have gained much attention in the recent times especially in the health-care sector as these devices offer real-time monitoring of vital physiological signs, enabling health-care professionals to evaluate health conditions and provide remote feedback. In this work, we have fabricated carbon-nanotube (CNT)/ polydimethylsiloxane (PDMS) composite sensor through simple dispersion and freezing method for monitoring flexion movements in humans. Sensors with different CNT loadings, namely 0.1 wt %, 0.5 wt %, and 1 wt % were fabricated and analyzed to find the best performing sensor. Several characterizations like Raman, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), tensile strength measurements, and piezoresistive studies were carried out to study the features of the sensors. Among the fabricated sensors, the one with the loading concentration of 0.5 wt% is found to be most sensitive for flexion applications with higher gauge factor of 533 at 60% strain level, response time of ~ 140 ms and lower hysteresis loss. The feasibility of the sensor for monitoring flexion like finger bending, wrist bending, elbow bending, and knee bending is also analyzed making it ideal for use in sports for athletes, physicians, and trainers to investigate physical performance and well-being.

Background: People these days use smartphone extensively as a means of diverse social activities, but excessive use of it has also created increasing forward head posture (FHP) with neck pain. To improve this FHP, neck stabilization exercise is necessary. Objectives: This study was to investigate the effects of stabilization exercise using biofeedback on FHP subjects with neck pain. Design: A non-randomized, controlled intervention study. Methods: This study chose 18 college students in their 20s whose neck disability index (NDI) was equal to or higher than 10 and cranio-vertebral angle indicated FHP as experimental group. The control group selected 18 persons with no neck pain and a normal range of cranio-vertebral angle. The stabilization movement was performed by applying three phases of pressure, with low of 20 mmHg, intermediate of 25 mmHg, and high of 30 mmHg, using the Stabilizer. To check the effects of stabilization exercise according to pressure, the circumference of deep neck muscles was measured with ultrasonic waves, and the activity of surface muscle of sternocleidomastoid (SCM) was measured using electromyography (EMG). Results: When the circumference of the deep neck flexor was analyzed according to the pressure change during stabilization exercise, the experimental group showed increase at all pressures. The activity of the SCM of the surface muscle increased in both groups as the pressure increased. Conclusion: The application of stabilization exercise was found to be more effective on forward head posture subjects with neck pain at lower pressures.

Background: The craniocervical flexion test (CCFT) was developed for the activation and endurance of deep cervical flexors. However, the muscle thickness and muscle thickness changing ratio of the sternocleidomastoid (SCM) and deep cervical flexor (DCF) muscles in subjects with and without forward head posture (FHP) have not been reported. Objects: To determine the difference in thickness of the SCM and DCF muscles and the difference in the muscle thickness changing ratio between SCM, DCF, and DCF/SCM 20 mmHg and DCF/SCM 30 mmHg between subjects with and without FHP. Methods: Thirty subjects with and without FHP were enrolled. The muscle thickness of the SCM and DCF was measured when maintained at a baseline pressure of 20 mmHg and a maximum pressure of 30 mmHg using a pressure biofeedback unit during the CCFT. Ultrasonography was used to capture images of SCM and DCF muscle thickness during the CCFT, which was calculated using the picture archiving and communication system (PACS). Results: We observed a significant difference within the pressure main effect between SCM and DCF at a baseline pressure of 20 mmHg and a maximum pressure of 30 mmHg (p < 0.05). However, there was no significant difference in the muscle thickness and muscle thickness changing ratio for SCM and DCF during CCFT between subjects with and without FHP. Conclusion: There was no significant difference in the muscle thickness recruitment pattern during CCFT in posture changes between subjects with and without FHP.

Background: The serratus anterior (SA) muscle prevents scapular winging (SW) by stabilizing the medial border of the scapula during arm movement. The upper trapezius (UT) and lower trapezius (LT) muscles may compensate for the weak SA muscle in individuals with SW during shoulder flexion. However, there is no study to examine whether compensation by UT and LT occurs in individuals with SW. Objects: This study compared the muscle activities of UT, LT, and SA as well as the SA/UT activity ratio between individuals with and without SW during shoulder flexion with load. Methods: This study recruited 27 participants with SW (n = 14) and without SW (n = 13). Electromyography data of the SA, UT, and LT muscles and SA/UT activity ratio were recorded and analyzed during shoulder flexion with 25% load of the maximal shoulder flexion force. Independent t-test was used to compare the UT, LT, and SA muscle activities and SA/UT ratio between the groups with and without SW; statistical significance was set at α of 0.05. Results: SA activity was significantly lesser in the group with SW than in the group without SW. However, there were no significant differences in the UT and LT activities and SA/UT activity ratio between the two groups. Conclusion: The SA activity was lesser in the group with SW than in the group without SW with 25% load of the maximal shoulder flexion force, but there was no compensatory muscle activity of the UT and LT observed. Therefore, further studies are warranted to clarify the compensatory strategy of scapular stabilization in individuals with SW during shoulder flexion under other heavy load conditions.

Background: Although various conventional approaches have been employed to reduce spasticity in neurological rehabilitation, only a few studies have shown scientific evidence for its effectiveness. Thus, we introduced a different concept (Ueda method) of rehabilitation therapy that can complement the limitations of conventional therapy. Objects: This study aimed to investigate the immediate effects of the application of the Ueda method on patients with spasticity after stroke via an electrophysiological study. Methods: We conducted a randomized double-blind pilot study in two rehabilitation hospitals involving 30 stroke patients who were randomly allocated to the Ueda (n = 15) and convention (n = 15) groups. Electromyographic data of six examined muscles in both upper extremities of all patients were recorded. The A-ApA index and activation ratios of upper extremity muscles were evaluated and compared between the groups to confirm post-intervention changes in upper-extremity flexor spasticity and flexion synergies. Repeated-measures analysis of variance was conducted to confirm the therapeutic effect (2 × 2) as a function of group (Ueda vs. convention) and time (pre-/post-intervention) on all outcome measures (p < 0.05). Results: In the Ueda group, the mean A-ApA index values differed significantly before and after the intervention (p = 0.041), indicating a weak evidence level; however, the effect size was medium (d = –0.503). The interaction effects of the A-ApA index between the Ueda and convention groups and between pre-intervention and post-intervention stages were significant (p = 0.012). The effect size was large (np 2 = 0.220). In the Ueda group, the activation ratios of the anterior deltoid fiber significantly decreased after the intervention in all reaching tasks. Conclusion: The Ueda method reduces upper-extremity flexor spasticity and changes its synergy in stroke patients and should be considered a rehabilitation therapy for spastic stroke patients.

Background: Bird dog exercise (BDE) is one of the lumbar stabilization exercises that rehabilitate low back pain by co-contraction of the local and global muscles. Previous studies have reported the effect of various type of BDEs (for example, practicing the exercises on various surfaces and changing the limb movement) for muscle co-contraction. Objects: This study aimed to investigate the effect of knee joint flexion position of the raised lower limb on abdominal and back muscle activity during BDE in patients with chronic low back pain (CLBP). Methods: Thirteen males participated in this study (age: 32.54 ± 4.48 years, height: 177.38 ± 7.17 cm). Surface electromyographic (SEMG) data of the internal abdominal oblique (IO), external abdominal oblique (EO), lumbar multifidus (MF), and thoracic part of the iliocostalis lumborum (ICLT) were collected in two knee joint flexion positions (90° flexion versus 0° flexion) during BDE. The SEMG data were expressed as a percentage of root mean square mean values obtained in the maximal voluntary isometric contraction. Results: Greater muscle activity of the IO (p = 0.001), MF (p = 0.009), and ICLT (p = 0.021) of the raised lower limb side and the EO (p = 0.001) and MF (p = 0.009) of the contralateral side were demonstrated in the knee joint flexion position compared to the knee joint extension position. Greater local/global activity ratios of the abdominal muscle (i.e., IO and EO) of the raised lower limb (p = 0.002) and the back muscle (i.e., MF and ICLT) of the contralateral side (p = 0.028) were also noted in the knee joint flexion position. Conclusion: BDE with a knee joint flexion position might be recommended as an alternative lumbar stabilization exercise to enhance muscle activity in both the raised lower limb and the contralateral sides of the trunk for individuals with CLBP

Background: Forward head posture (FHP) causes various posture imbalances associated with the head and neck. Myofascial release is an effective treatment method used for relaxing muscles and reducing muscle hyperactivity, but no studies have been conducted on suboccipital and neck muscles related to FHP. Objects: The purpose of this study was to investigate the immediate effect of roller massages on the cranio-cervical flexion (CCF) range of motion (ROM) and CCF strength applied to suboccipital and neck muscles in subject with forward head posture. Methods: Twenty-four FHP subjects (male: 13, female: 11) were recruited for this study. All subjects were recruited with a craniovertebral angle (CVA) of 53 degrees or less and a head tilt angle (HTA) of 20.66 degrees or higher. CCF strength was measured using Pressure biofeedback unit (PBU) in the supine posture and CCF ROM was measured using smartphone-based inclinometer. Roller massage (RM) was applied to suboccipital and neck muscles for 2 minutes and CCF ROM and strength were remeasured. Results: These results of this study showed that CCF ROM was a significant difference in CCF ROM before and after RM (p < 0.05). CCF strength also showed a significant difference before and after RM (p < 0.05). Conclusion: RM method might be recommended to increase the immediate ROM and strength of CCF in subjects with forward head posture.

Previous studies have reported that deep neck flexor (DNF) exercise can improve neck problems, including neck pain, forward head posture, and headache, by targeting the deep and superficial muscles of the neck. Despite the prevailing opinion across studies, the benefits of DNF can vary according to the type of neck problems and the outcome measures adopted, ranging from positive outcomes to non-significant benefits. A meta-analysis was conducted in this study to assess conclusive evidence of the impact of DNF exercise on individuals with neck problems. We used PUBMED, MEDLINE, NDSL, EMBASE, and Web of Science to search for primary studies and the key terms used in these searches were “forward head posture (FHP),” “biofeedback,” “pressure biofeedback unit,” “stabilizer,” “headache,” and “neck pain.” Twenty- four eligible studies were included in this meta-analysis and were coded according to the type of neck problems and outcome measures described, such as pain, endurance, involvement of neck muscle, craniovertebral angle (CVA), neck disability index (NDI), cervical range of motion (CROM), radiographs of the neck, posture, strength, endurance, and headache disability index. The overall effect size of the DNF exercise was 0.489. The effect sizes of the neck problems were 0.556 (neck pain), –1.278 (FHP), 0.176 (headache), and 1.850 (mix). The effect sizes of outcome measures were 1.045 (pain), 0.966 (endurance), 0.894 (deep neck flexor), 0.608 (superficial neck flexor), 0.487 (CVA), 0.409 (NDI), and 0.252 (CROM). According to the results of this study, DNF exercise can effectively reduce neck pain. Thus, DNF exercise is highly recommend as an effective exercise method for individuals suffering from neck pain.

Background: The flexion-relaxation phenomenon (FRP) refers to a sudden onset of activity in the erector spinae muscles that recedes or fades during full forward flexion of the trunk. Lumbar spine and hip flexion are associated with many daily physical activities that also impact trunk flexion. Shorter hamstring muscles result in a reduction of pelvic mobility that eventually culminates in low back pain (LBP). Many studies have explored the FRP in relation to LBP. However, few studies have investigated the influence of hamstring muscle length on the FRP in relation to the erector spinae muscles during trunk flexion. Objects: This study aimed to investigate the influence of hamstring muscle length on the FRP in relation to the erector spinae muscles during trunk flexion. Methods: Thirty subjects were divided into three groups according to hamstring length measured through an active knee extension test. The 30 participants consisted of 10 subjects who had a popliteal angle of 20˚ or less (Group 1), 10 subjects who had a popliteal angle of 21˚–39˚ (Group 2), and 10 subjects who had a popliteal angle of 40˚ or more (Group 3). A one-way analysis of variance was used to compare the difference in muscle activity of the erector spinae muscles during trunk flexion. Results: The subjects with a shorter hamstring length had significantly higher muscle activity in their erector spinae muscles during trunk flexion and full trunk flexion (p < 0.05). The subjects with a shorter hamstring length also had a significantly higher flexion-relaxation ratio (p < 0.05). Conclusion: The results of this study demonstrate that differences in hamstring muscle length can influence the FRP in relation to the erector spinae muscles. This finding suggests that the shortening of the hamstring might be associated with LBP.

Background: Although various exercises have been performed for patients with chronic low back pain (CLBP), the effects of these exercises including joint mobilization, gym ball exercises, and breathing exercises on flexion relaxation ratio (FRR) have not been compared. Objective: To compare the effects of joint mobilization, gym ball exercises, and breathing exercises on the flexion relaxation phenomenon (FRP) and pain in patients with chronic low back pain. Design: Randomized pretest-posttest control group design. Methods: Thirty-six patients with chronic low back pain who were undergoing rehabilitation at a rehabilitation center were included. The patients were randomly divided into three groups: joint mobilization group (JMG; n=12), gym ball exercise group (GBG; n=12), and breathing exercise group (BEG; n=12). The exercises were performed for 40 minutes a day, twice a week, for a total of 12 weeks. Results: There were no significant differences in FRR between the three groups (P>.05). Significant decreases in the modified visual analog scale (MVAS) scores after intervention between the groups were found (P<.05). The GBG was significantly decreases from the JMG in the MVAS (P<.05). However, there were significant improvements between the pre- and post-interventional findings on FRR and MVAS in the three groups (P<.05). Conclusion: We demonstrated that intervention using joint mobilization, gym ball exercises, and breathing exercises improve FRP and pain in patients with CLBP.

Background: In patients with lumbar spinal stenosis (LSS), lumbar flexion exercise (LFE) is considered a standard therapeutic exercise that widens the space between the spinal canal and intervertebral foramen. However, some researchers have reported that lumbar extension exercise (LEE) may improve lumbar pain and functional ability in patients with LSS. Although exercise intervention methods for patients with LSS have been widely applied in clinical settings, few studies have conducted comparative analysis of these exercise methods. Objects: This study aimed to compare the effects of LFE, LEE, and lumbar flexion combined with lumbar flexion-extension exercise (LFEE) on pain, range of motion (ROM), pelvic tilt angle, and functional gait ability in patients with LSS. Methods: A total of 30 patients with LSS, LFE (n1=10), LEE (n2=10), and LFEE (n3=10) were assigned to each of the three exercise groups. The numerical pain rating scale (NPRS), modified-modified schober test (MMST)-flexion, MMST-extension, pelvic tilt inclinometer, and 6-minute walking test (6MWT) were measured. Results: After the intervention, statistically significant differences were observed in the NPRS (p=.043), MMST-flexion (p<.001), MMST-extension (p<.001), and 6MWT (p=.005) between groups. According to the post hoc test, the NPRS was statistically significant difference between the LFEE and LEE groups (p=.034). The MMST-flexion was statistically significantly different between the LFE and LEE (p=.000), LFE and LFEE (p=.001), and LEE and LFEE (p=.001) groups. The MMST-extension was statistically significantly different between the LFE and LEE (p<.001), LFE and LFEE (p=.002), and LEE and LFEE (p=.008) groups. The 6MWT was statistically significantly different between the LFE and LFEE (p=.042) and the LEE and LFEE (p=.004) groups. Conclusion: This study suggested that LFEE was the most effective exercise for pain and functional gait ability in patients with LSS, LFE was the most effective exercise for lumbar flexion ROM, and LEE was the most effective exercise for lumbar extension ROM.

Background: The bridge exercise targets the gluteus maximus (Gmax) and gluteus medius (Gmed). However, there is also a risk of dominant hamstring (HAM) and erector spinae (ES) muscles. Objects: To analyze the muscle activity the of Gmax, Gmed, HAM and ES during the bridge exercise with and without hip external rotation in different degrees of knee flexion. Methods: Twenty-three subjects were participated. The electormyography (EMG) activity of the Gmax, Gmed, HAM and ES muscles was recorded during the exercise. The subjects performed the bridge exercise under four different conditions: (a) with 90˚ knee flexion, without hip external rotation (b) with 90˚ knee flexion, with hip external rotation (c) with 135˚ knee flexion, without hip external rotation (d) with 135˚ knee flexion, with hip external rotation. Results: There was no significant interaction effect between the degree of knee flexion and hip external rotation. There was a significant main effect for degree of knee flexion in Gmax, HAM muscles activity. Gmax muscle activity was significantly greater in the 135˚ knee flexion position than in the 90˚ knee flexion position (p<.001). While HAM muscle activity was significantly less in 135˚ knee flexion position than in the 90˚ knee flexion position (p<.001). ES muscle activity was significantly less in the 135˚ knee flexion position than in the 90˚ knee flexion position (p=.002). The activity of both the Gmax and Gmed muscles was significantly greater with hip external rotation (p<.001 and p=.005, respectively). Conclusion: For patients performing the bridge exercise, positioning the knee in 135° of flexion with hip external rotation is effective for improving Gmax and Gmed muscle activity while decreasing HAM, and ES muscle activity.

Background: Most of the previous researches on the abnormality of breathing pattern have focused on the silence of functional movements owing to such abnormality, however, have not been clearly identified the relationship between the abnormal breathing pattern on one hand and kinesiophobia and flexion relaxation phenomenon (FRP) on the other hand. Objective: To compare patients with chronic low back pain (CLBP) and healthy person in the abnormality of breathing pattern, kinesiophobia, and FRP during flexion and extension of the trunk. Design: Case-control study. Methods: The research subjects consisted of a group of 15 healthy adults and another group of 15 patients with CLBP. Capnography was used to measure the endtidal CO2 (EtCO2) and respiratory quotient (RQ). The muscle activity of multifidus and erector spinae of the subjects was measured during flexion and extension of the trunk to identify their FRP. The Nijmegen Questionnaire (NQ) and Tampa Scale of Kinesiophobia (TSK) were utilized to measure their breathing patterns and kinesiophobia, respectively. The Kolmogorov-Smirnov (K-S) test was conducted in order to analyze the normal distribution of the measured data. Their general characteristics were identified by the descriptive statistics and the independent t-test was performed to identify the differences between the two groups in terms of abnormality of breathing pattern, kinesiophobia, and FRP. The level of significance was set at α=.05. Results: The patients with CLBP had significantly less EtCO2 and shorter breathing hold time (BHT) than normal healthy person (p<.05). The patient with CLBP also had significantly greater kinesiophobia than healthy person (p<.05), and had less FRP than the healthy person (p<.01). Conclusions: These results suggest that the CLBP had greater abnormality of breathing pattern and kinesiophobia with less FRP than healthy person.

Background: The hamstring muscles in the lower extremity are highly important for knee joint stability and can be classified into medial and lateral hamstrings according to the anatomical position, which have some different functions. To measure the strength of the individual hamstring muscles, manual muscle testing is clinically performed by dividing rotation postures into internal and external postures. However, this has no sufficient scientific background. Objects: This study aimed to test the difference that the tibial rotation would cause in the muscle activity of the medial and lateral hamstrings. Methods: The muscle activities of the biceps femoris, semitendinosus, and semimembranosus were measured in a total of three different postures (neutral position and internal and external rotations) with 3 replications. During the maximal isometric contraction, resistance was constantly provided by the string attached to the strap, not by manual resistance of the examiner. Before and after electromyography measurements, the participants underwent hamstring flexibility measurement using the active knee extension test in the supine position on the treatment table Results: The semitendinosus had a 12.56% reduction in muscle activity in external rotation as compared with that in neutral position. The biceps femoris and semimembranosus showed reduced muscle activities in both external and internal rotations as compared with those in neutral position. Only the women showed significant decreases in the comparison between pre and post-active knee extension. Conclusion: Only the semitendinosus muscle was consistent with the anatomical speculation. However, the reduction in the muscle activity of the semitendinosus as compared with that in neutral position was only 12.56%, the clinical value of which may be difficult to justify.

Background: The craniocervical flexion (CCF) exercise is one of the effective exercise in correcting forward head posture (FHP). However, some people with FHP achieve CCF with compensatory movements, for example, low cervical flexion using superficial neck flexors such as the sternocleidomastoid (SCM) muscle. No study has yet investigated whether a dualpressure biofeedback unit (D-PBU) method to prevent low cervical flexion would be helpful in performing pure CCF movement. Objects: The purpose of this study was to compare the effects of the CCF using D-PBU method and the traditional CCF method on the cross-sectional area (CSA) of the longus colli muscle (LCM) and the activity of SCM muscle in subjects with FHP. Methods: Twentyfour FHP subjects (male: 16, female: 8) were recruited for this study. All subjects performed CCF using two different methods: The traditional CCF method and the CCF using D-PBU method. The CSA of the LCM was measured via ultrasound, and surface electromyography was used to measure SCM muscle activity. Results: The change in CSA of the LCM was significantly larger during the CCF using D-PBU method (1.28±.09) compared with the traditional CCF method (1.19±.08) (p<.05). The SCM muscle activity using the CCF using D-PBU method (2.01±1.97 %MVIC) was significantly lower than when using the traditional CCF method (2.79±2.32 %MVIC) (p<.05). Conclusion: The CCF using D-PBU method can be recommended for increasing LCM activation and decreasing SCM muscle activity during CCF movement in subjects with FHP.

Background: The deep cervical flexor (DCF) muscles have a crucial role in the management of neck pain. For preventing neck pain by activation of the DCF, craniocervical flexion (CCF) is an effective exercise. However, sternocleidomastoid (SCM) muscle is considered to affect negatively the activation of the DCF. SCM muscle which is an accessory muscle for respiration is activated differently depending on types of breathing patterns. It’s not certain that breathing patterns affect the SCM and DCF muscles thickness during CCF exercise. Objects: The purpose of this study was to investigate the influence of breathing patterns on the SCM and DCF muscles thickness during CCF exercise. Methods: Forty-five subjects participated in this study, and they were classified according to their breathing pattern, as follows: Costodiaphragmatic breathing (CDB) and upper costal breathing (UCB) groups. Ultrasonographic imaging of the SCM and DCF muscles was performed during five incremental levels of CCF during tidal breathing and expiration. Results: There was a significant interaction between the breathing pattern and the phase of CCF for percentage of SCM muscle thickness changes (p˂.05). In phase 1 CCF, a percentage of SCM muscle thickness changes was increased in the UCB group than in the CDB group (p˂.05). There was an increase in DCF muscles thickness with each additional CCF phase (p˂.05). Conclusion: Recruitment of SCM muscle was increased in the UCB group while performing CCF with a low intensity. There were no significant differences on DCF recruitment between the breathing pattern groups. Higher CCF exercise intensities elicited a higher DCF recruitment.

This study was conducted to compare the difference between left and right extension and flexion isokinetic muscular strength of the knee, shoulder, and trunk to compare absolute and relative strength in lightand heavy weight Ssireum athletes. Fourteen professional Ssireum athletes were divided into the light (Taebaek and Geumgang) and heavy (Halla and Baekdu) groups according to the body weight. Anthropometric measurements and isokinetic strength (knee: 60º/sec, shoulder: 30º/sec, and trunk: 30º/sec) were assessed for the absolute and relative peak torque values. Left (227.6±48.7 vs 247.0± 23.1 Nm, p=0.05) and right knee (233.7±32.0 vs 266.1±20.5, p=0.05) extension strength in absolute values were significantly different between the groups. Trunk’s extension (318.7±37.9 vs 351.2±57.4 Nm, p=0.03) and flexion (249.8±33.0 vs 302.1±42.4 Nm, p=0.03) strength also showed significant difference between the groups. Significant differences were observed for all relative values except for the left knee and trunk flexion. As for the flexion and extension strength ratios, the shoulder extension to flexion ratios of the light group was 1.32 (p=0.02) times and the heavy group was 1.01-0.98 (p=0.34). The trunk extension strength was 3.6 times that of the body weight in the light group and 2.8 times that of the body weight in the heavy group. Heavy Ssireum athletes’ absolute flexor peak torques were higher in the knee and trunk than in the light athletes. Also, the weight per weight of light athletes had relatively higher strength than the heavy athletes. In addition, the muscle strength ratio was higher in the light athletes. This study suggests that isokinetic strength is different in heavy and light weight class Ssireum athletes.

Background: Methods for exercising serratus anterior (SA) and upper trapezius (UT) muscles are important for the recovery of patients with various shoulder disorders, yet the efficacy of closed or open kinetic chain exercises have not yet been evaluated. Objects: The purpose of this study was to compare the activation of the SA and UT muscles during scapular protraction considering both closed and open kinetic chain exercises. Methods: Thirty subjects were randomly divided into experimental groups (closed kinetic chain exercise) and control groups (open kinetic chain exercise) in which scapular protraction was performed at 90° or 125° shoulder flexion. Electromyographic activity data were collected from the SA and UT muscles per position and exercise method. Results: Separate mixed 2-way analysis of variance showed significant differences in the activation of the SA (F1,28=6.447, p=.017) and the UT (F1,28=35.450, p=.001) muscles between the groups at 90° and 125° shoulder flexion. Also, the SA/UT ratio measures at 90° and 125° shoulder flexion significantly differed between the groups (F1,28=15.457, p=.001). That is, the closed chain exercise was more effective than open chain exercise for strengthening the SA muscle and controlling the UT muscle, 125° of shoulder joint was more effective than 90°. Conclusion: The findings suggest that scapular protraction with shoulder 125° flexion at the closed kinetic chain exercise may be more effective in increasing SA muscle activation and decreasing UT muscle activation as well as increasing the SA/UT ratio than open kinetic chain exercise.

Background: Flexion-relaxation phenomenon (FRP) was a term which refers to a sudden onset of myoelectric silence in the erector spinae muscles of the back during standing full forward flexion. Hamstring muscle length may be related to specific pelvic and trunk movements. Many studies have been done on the FRP of the erector spinae muscles. However, no studies have yet investigated the influence of hamstring muscle flexibility on the FRP of the hamstring muscle and lumbopelvic kinematics during forward bending. Objects: The purpose of this study was to examine the flexion-relaxation ratio (FRR) of the hamstring muscles and lumbopelvic kinematics and compare them during forward bending in subjects with different hamstring muscle flexibility. Methods: The subjects of two different groups were recruited using the active knee extension test. Group 1-consisted of 13 subjects who had a popliteal angle under 30°; Group 2-consisted of 13 subjects who had a popliteal angel above 50°. The kinematic parameters during the trunk bending task were recorded using a motion analysis system and the FRRs of the hamstring muscles were calculated. Differences between the groups were identified with an independent t-test. Results: The subjects with greater hamstring length had significantly less lumbar spine flexion movement and more pelvic flexion movement. The subjects with greater pelvic flexion movement had a higher rate of flexion relaxation during full trunk bending (p<.05). Conclusion: The results of this study suggest that differences in hamstring muscle flexibility might cause changes in people’s hamstring muscle activity and lumbopelvic kinematics.