Significant Differences In Muscle Activity Research Articles

Age-Related Changes in Morphology and Function of Scapular Muscles in Asymptomatic People

BackgroundAging is a contributing factor to rotator cuff tears. Dysfunction of the scapular muscles can be a potential cause of rotator cuff tears. Although aging can contribute to dysfunction of the scapular muscles and subsequently result in rotator cuff tears, the effects of aging on scapular muscles are unclear. ObjectiveTo determine changes in sizes and electromyographic activities of the scapular muscles with age in asymptomatic subjects. DesignCross-sectional study. PatientsFifty-four asymptomatic subjects without shoulder pain and dysfunction (18 male and 36 female) were recruited for this study. Subjects consisted of 19 people aged 20-39 years (young adult group, 27.2 ± 5.2 years), 17 people aged 40-59 years (middle age group, 49.9 ± 6.6 years), and 18 people aged 60-79 years (elderly group, 68.0 ± 7.1 years). MethodsUsing ultrasonography, we measured the muscle thickness of the trapezius (upper and lower portions), serratus anterior, and middle deltoid muscles during rest with the subject in a sitting position. Activities of the same muscles were measured with surface electromyography during shoulder elevation in the scapular plane up to 120°. The electromyographic data were analyzed at ranges 0°-30°, 30°-60°, and 60°-90°. Analysis of variance and Bonferroni multiple comparisons were used for statistical analysis. ResultsMuscle thickness of the lower trapezius in the elderly group was decreased significantly compared with that in the young adult group (95% confidence interval −0.40, 2.24; P < .001) and middle age group (95% confidence interval −0.34, 1.89; P = .012). There were no significant differences in muscle activity and activity ratio between groups. ConclusionIn scapular muscles, muscle thickness of the lower trapezius significantly decreased with aging, although there were no decreases in muscle thicknesses of the other muscles between different age groups. For the functional change, aging may not affect the scapular muscle activities and balance of the activities between the deltoid and scapular muscles. Level of EvidenceIV

CHARACTERISTICS OF ANKLE MUSCLE ACTIVITY DURING TILTING MOVEMENTS ON A WOBBLE BOARD

BackgroundBalance training is a common component of rehabilitation after ankle sprains. A relatively high activity of the peroneus longus (PL) to the activity of the tibialis anterior (TA) (a low...

The magnitude of muscular activation of four canine forelimb muscles in dogs performing two agility-specific tasks.

BackgroundThe purpose of this study was to measure the muscular activation in four forelimb muscles while dogs performed agility tasks (i.e., jumping and A-frame) and to provide insight into potential relationships between level of muscular activation and risk of injury. Muscle activation in eight healthy, client-owned agility dogs was measured using ultrasound-guided fine-wire electromyography of four specific forelimb muscles: Biceps Brachii, Supraspinatus, Infraspinatus, and Triceps Brachii – Long Head, while dogs performed a two jump sequence and while dogs ascended and descended an A-frame obstacle at two different competition heights.ResultsThe peak muscle activations during these agility tasks were between 1.7 and 10.6 fold greater than walking. Jumping required higher levels of muscle activation compared to ascending and descending an A-frame, for all muscles of interest. There was no significant difference in muscle activation between the two A-frame heights.ConclusionsCompared to walking, all of the muscles were activated at high levels during the agility tasks and our findings indicate that jumping is an especially demanding activity for dogs in agility. This information is broadly relevant to understanding the pathophysiology of forelimb injuries related to canine athletic activity.

융복합 디지털 콘텐츠를 활용한 당구 스트로크 시 숙련자와 비숙련자의 근활성도 및 뇌파에 미치는 영향

본 연구의 목적은 당구 숙련자와 비 숙련자를 대상으로 당구 스트로크 시 근활성도와 뇌파를 비교 분석함으로써 두 집단 간의 차이를 규명하여 객관적이고 과학적인 데이터를 통해 당구의 효과와 효율적인 훈련 방법을 위한 기초 데이터를 제시하는데 있다. 연구결과 숙련자와 비숙련자간에 근활성도에는 유의한 차이가 나타나지 않았으며 뇌파에서도 유의한 차이가 나타나지 않았다. 따라서 당구 스트로크 시 숙련자와 비숙련자 간의 근활성도와 뇌파에는 긍정적인 영향을 미치지 않은 것으로 확인되었다. 이러한 원인은 연구대상자의 부족, 일회적인 실험, 그리고 심리적 및 생리적인 실험 통제를 완전히 하지 못했기 때문이라고 생각되며 이와 관련하여 본 연구에 대한 기전을 보다 명확하게 밝히기 위해서는 추후 생리 및 심리적인 실험통제가 이루어진 상황에서의 연구가 이루어져야 할 것으로 사료된다. The purpose of this research is aimed at billiards experts and non-experts during the billiard stroke: a comparative analysis of concentration and muscle activity, identifying the differences between the two groups by the objective and scientific data is presented to propose the basis for effective and efficient training methods of billiards. The results of the study showed no significant differences in muscle activity and concentration between experts and non-experts. Therefore, the muscle activity and concentration between the experts and non-experts had no positive effect during the billiard stroke. These causes are thought to be as a lack of research subjects, being a one-time experiment, and not being able to control psychological and physiological experiments completely. In this regard, psychological and physiological experiments are considered to be controlled for further study to determine the principles more clearly.

A study on the relationships among hand muscles and form factors of large-screen curved mobile devices

The aim of this study is to determine the effect of form factors (curvature rate, depth) of mobile devices on hand comfort when using large-screen curved mobile devices. To that end, four muscles (APB, APL, FDI, EDC) were selected and mockups for experiment were developed with four curvature rate levels (flat/100/200/300R) and five depth levels (3/5/7/9/11 mm). User experiment was conducted using three interactions (tapping, dragging, and texting) that usually take place on smartphones. EMG signal of each participant was measured. Combination of curvature and depth could maximize the physical comfort of hands and fingers through the experiment so that the interaction effect between form factors and tasks could be identified. Our results revealed that only APL and FDI had statistically significant muscle activity amounts across the curvature rates. With respect to effect of depth, all four muscles showed statistically significant difference in muscle activity. Moreover, results from the interaction effect among task levels of two tasks (target location of tapping and direction of dragging) and two form factors showed no interaction effect in either tapping or texting. The results of this study could be used to determine the optimal range for form factors of curved screen mobile devices in terms of physical comfort of the hand while using large-screen devices.

The influence of foot arch on ankle joint torques andon sEMG signal amplitude in selected lower leg muscles

Abstract Introduction: This study sought to assess the influence of proper foot arch on electromyographic activity of selected lower limb muscles. The aim of this work was to evaluate the effects of foot arch on the activity of selected muscles and to determine whether electromyography might help to identify types of flat feet resulting from muscle- or ligament-related causes. Material and methods: The experiment involved 24 students of the Faculty of Rehabilitation, University of Physical Education in Warsaw. To determine Clarke’s angle, all study participants were examined with a podoscope. Based on the obtained results, the subjects were divided into two groups. The experimental group consisted of 12 individuals with low foot arches, while the control group included students with proper foot arches. The surface EMG (sEMG) signal was recorded from the following muscles: peroneus longus, tibialis anterior, gastrocnemius and soleus. First, the sEMG signal was recorded while measuring MVC for ankle extensors and flexors. Then, it was recorded in the following positions: free standing, two-leg standing on tiptoe, one-leg standing on tiptoe, pressing the first metatarsal head to the ground standing on heels. Results: No significant differences in muscle activity between the groups with low and proper foot arches were noted (p&gt;0.05). Muscle activity did not prove to be a differentiating factor. Moreover, no differences were found in torques of ankle extensors and flexors between both groups. Conclusions: The findings of the study confirmed the hypothesis that the size of the foot arch had no effect on electromyographic activity of lower limb muscles. It was also revealed that flat feet did not lead to the weakening of muscle strength of ankle flexors and extensors.

Activation of Spinal Stabilizers and Shoulder Complex Muscles During an Inverted Row Using a Portable Pull-up Device and Body Weight Resistance.

Youdas, JW, Keith, JM, Nonn, DE, Squires, AC, and Hollman, JH. Activation of spinal stabilizers and shoulder complex muscles during an inverted row using a portable pull-up device and body weight resistance. J Strength Cond Res 30(7): 1933-1941, 2016-We recorded muscle activation normalized to a maximum voluntary isometric contraction (% MVIC) during an inverted body weight row using a commercially available portable pull-up device. Surface electromyographic (EMG) analysis was conducted on 13 male and 13 female subjects performing 4 inverted row exercises: (a) pronated grip both feet weight-bearing (WB); (b) supinated grip both feet WB; (c) pronated grip one leg WB; and (d) supinated grip single-leg WB. Nine muscles were analyzed: (a) posterior deltoid (PD), (b) latissimus dorsi (LD), (c) biceps brachii (BB), (d) lower trapezius (LT), (e) upper trapezius (UT), (f) lumbar multifidus (LM), (g) middle trapezius (MT), (h) lumbar thoracis (LTh), and (i) rectus abdominis (RA). Normalized peak EMG activity was examined separately for each muscle with 9 repeated measures analysis of variance (ANOVA) at α = 0.05. Post hoc comparisons of EMG activation across exercises for statistically significant ANOVAs were conducted with Bonferroni corrections for multiple comparisons. We observed statistically significant differences in EMG activation of the LD between supinated and pronated double-leg WB (p = 0.001) condition. Additionally, we found statistical significance in the UT between pronated and supinated single-leg WB (p = 0.007). No statistically significant differences in muscle activation existed between single- and double-leg WB in any muscles. Four muscles (BB, LD, LT, and PD) demonstrated very high (>61% MVIC) EMG activation during all 4 exercise conditions. Three muscles (UT, MT, and LM) demonstrated high (41-60% MVIC) activation, whereas 2 muscles (LTh and RA) demonstrated moderate (21-40% MVIC) activation. Four inverted row exercises activated the LD, UT, MT, LT, and BB at levels conducive to strengthening.

Effects of a Simulated Game on Muscle Activation in Youth Baseball Pitchers.

It is generally accepted that playing with fatigue is a primary predictor of injury in youth baseball because muscular fatigue is believed to alter mechanics during the arm cocking and acceleration phases. Therefore, the purpose of this study was to quantitatively describe gluteal and upper extremity muscle activations in youth baseball pitchers during a simulated game. Twenty-three youth baseball players (11.2 ± 0.8 years; 151.4 ± 8.7 cm; 47.5 ± 10.8 kg) participated. Data were collected through a Delsys Bagnoli-8-channel electromyography system. Single differential electrodes (interelectrode distance: 10 mm) were attached to the bilateral gluteus maximus and medius and throwing side latissimus dorsi, lower trapezius, and serratus anterior and upper trapezius. After warm-up, participants were instructed to throw randomly provided game situations over a regulation distance (46 feet; 14.02 meters) to a catcher. Three, 4-seam fastballs for strikes, thrown in the first and last innings of the simulated game were selected for analysis. A multivariate analysis of variance revealed no statistically significant differences in muscle activity at the 3 phases of the throw, between first and last innings of the simulated game with an observed power of 0.274 (phase 1: foot contact to maximum shoulder external rotation), 0.297 (phase 2: maximum shoulder external rotation to ball release), and 0.226 (phase 3: ball release to maximum shoulder internal rotation). Examining muscle activations as a pitcher approaches fatigue provides information on how long a pitcher can perform before mechanical alterations occur. Although this study did not reveal significant changes, it did reiterate the fact that pitch counts may be working in possibly preventing a youth pitcher throwing to fatigue.

The effect of combined exercise with slings and a flexi-bar on muscle activity and pain in rotator cuff repair patients.

[Purpose] The purpose of this research was to determine the effect of combined exercise with slings and a Flexi-Bar on muscle activity and pain in rotator cuff repair patients. [Subjects and Methods] This research evaluated 20 rotator cuff repair patients divided randomly into groups of 10 as the control group and the experimental group. The experimental group performed combined exercise with slings and a Flexi-Bar. Both the experimental and control groups were treated with a transcutaneous electrical nerve stimulator and continuous passive motion. Muscle activity was measured with surface electromyography. Pain was measured with the visual analogue scale. The paired t-test was used to compare groups before and after the experiment. The independent t-test was used to assess the differences in the degree of change between the two groups before and after the experiment. [Results] Subjects of both the experimental group and control group showed significant differences in muscle activity and pain. However, as compared with the control group, there was significant differences in the muscle activity and pain in the experimental group. [Conclusion] These results indicate that combined exercise with slings and a Flexi-Bar is effective in improving muscle activity and decreasing pain in rotator cuff repair patients.

Clinical effectiveness of a Pilates treatment for forward head posture.

[Purpose] This study compared the effects of pilates and an exercise program on the craniovertebral angle, cervical range of motion, pain, and muscle fatigue in subjects with a forward head posture (FHP). [Subjects and Methods] A total of 28 sedentary females (age 20 to 39 years) with FHP were randomly assigned to pilates (n=14) and combined (n=14) exercise groups. The study was a randomized, controlled, double-blind study with the two groups performing exercise 50 min/day, 3 days/week, with an intensity of 11–15 rating of perceived exertion (RPE) for ten weeks. The main outcome measures were craniovertebral angle, cervical range of motion (ROM), pain levels assessed by visual analog scale (VAS), and neck disability index (NDI). Surface electromyography was also used to measure muscle fatigue. [Results] There were significant increases in craniovertebral angle and cervical ROM in the pilates group, but none in the control group. The only significant differences in muscle activity were recorded in the sternocleidomastoid muscle in the pilates group. Both exercise programs had positive effects on pain measures, as VAS and NDI were significantly decreased. [Conclusion] The results suggest that pilates could be recommended as an appropriate exercise for treatment of FHP in sedentary individuals.

The effects of the angles of the knee and heel-off on the muscle activity during a bridge exercise

PURPOSE: The purpose of this study is to investigate the effects of the angles of the knee and heel-off on the muscle activity during a bridge exercise. METHODS: 15 healthy adult men and women with the balance ability and joint working range required for performing a bridge exercise participated in this study, in which 120°, 90° and 60° angles of the knee-flexion and heel-off were applied during the bridge exercise. RESULTS: Our data showed that there were significant differences in muscle activities of elector spinae and rectus abdominis when 120°and 60°angles of the knee were applied, of internal oblique when 120°and 60°were applied, and external oblique when 90°and 60°were applied. When heel-off was applied, there were significant differences in muscle activities of elector spinae and rectus abdominis when 120°and 60°were applied, of internal oblique when 120°and 60°were applied, and external oblique when 90°and 60°were applied. CONCLUSION: In this study on an application of heel-off to the bridge exercise, we showed that the effect of †Corresponding Author: ptlsk@deu.ac.kr This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. the angles of the knee on the muscle activities of elector spinae, rectus abdominis, internal oblique and external oblique were all similar to the regular bridge exercise, but overall muscle activities were increased with heel-off when compared with the regular bridge exercise.

Muscle activation, blood lactate, and perceived exertion responses to changing resistance training programming variables

Ratings of perceived exertion (RPE: 0–10) during resistance training with varying programming demands were examined. Blood lactate (BLa) and muscle activation (using surface electromyography: EMG) were measured as potential mediators of RPE responses. Participants performed three sets of single arm (preferred side) bicep curls at 70% of 1 repetition maximum over 4 trials: Trial (A) 3 sets × 8 repetitions × 120 s recovery between sets; (B) 3 sets × 8 repetitions × 240 s recovery; (C) 3 sets × maximum number of repetitions (MNR) × 120 s recovery; (D) 3 sets × MNR × 240 s recovery. Overall body (RPE-O) and active muscle (RPE-AM) perceptual responses were assessed following each set in each trial. Biceps brachii and brachioradialis muscle EMG was measured during each set for each trial. RPE-O and RPE-AM were not different between Trial A (3.5 ± 1 and 6 ± 1, respectively) and Trial B (3.5 ± 1 and 5.5 ± 1, respectively) (p < .05). However, RPE-AM was significantly greater in Trial C (7.5 ± 1.5) and Trial D (7.5 ± 1.5) than in Trial B (p < .05). There were no significant differences in muscle activation or BLa between trials; however, work rate (tonnage/min) was greater in Trials C and D compared to Trial B. In conclusion, BLa and muscle activation were not related to RPE, but resistance training variables, such as work rate, may impact on RPE when intensity (%1RM) and the number of sets completed remain constant.

Comparison of muscle activation of hip belt squat and barbell back squat techniques

BACKGROUND: Hip belt squats are believed to have been introduced in 1970. By removing the load from the shoulders and upper trapezius, the hip belt squat places emphasis on the legs with less load on the spine. No peer-reviewed research exists on the muscle recruitment patterns of a hip belt squat, or how it compares in muscle activation to other squatting activities. OBJECTIVE: The purpose of the study was to determine lower extremity muscle activation in a hip belt squat (SquatMax = MD) in comparison with a barbell back squat. METHODS: Thirteen participants performed four repetitions of an 8-RM squat using three different techniques: hip belt squat without a band, hip belt squat with a band, and barbell back squat. Electromyographic data were collected from six muscles: quadriceps, biceps femoris, hip adductors, hip abductors, gluteus maximus, and gastrocnemius. RESULTS: ANOVA revealed no significant difference in muscle activity between devices. The only muscle group statistically different between genders was the gastrocnemius (p = 0.04). Hip adductor activity was lowest and hip abductor activity was highest when performing a hip belt squat with the band for both genders. Likewise, the adductor to hamstring ratio was lowest with the hip belt squat. CONCLUSIONS: Given the lack of significant difference in the muscle activity between the squat techniques, one needs to look at other attributes to determine both the scientific and, consequently, the practical value. Given the placement of the belt around the pelvis, one positive attribute for the hip belt squat is the ability to unload the shoulders and spine. Another positive attribute for the hip belt squat is the higher hip abductor to adductor ratio. This could be very important for injury prevention and patella tracking. While the back squat has slightly higher hamstring recruitment, which is important in ACL injury prevention, the hip belt squat may address this by offsetting the free weight with the use of an additional band. If a free weight hip belt squat device is available, it may be a better alternative to the traditional barbell squat technique.

Muscle activity patterns in different standing postures in people with recurrent lower back pain

Background: Excessive lordosis or kyphosis of the spine is thought to be a cause of lower back pain (LBP), and reportedly creates irregularities in lumbar extensor activity (Shirado, 1995). The iliopsoas (ILIO) is thought to play a role in LBP in patients with recurrent LBP (RLBP) (Lee, 2013). Recent research has shown that activity of local muscles deep in the trunk is important in preventing LBP (Hodges, 2009), althoughmany details of this remain unclear. There have been no reports on differences in lumbar extensor activity related to different postures between people with and without RLBP. Purpose: To clarify differences in lumbar extensor activity between people with and without RLBP with respect to different standing postures, and to elucidate how the trunk and hip flexors used in lumbar extension are responsible for controlling lower back and spinal alignment. Methods: Subjects included 11 adults with RLBP (RLBP group), and nine healthy adults with no history of orthopedic diseases in the legs or trunk (pain-free group). We measured activity of the ILIO, multifidus (MF), iliocostalis lumborum (IL), and iliocostalis thoraces (IT) muscles using an MQ16 (Kissei Comtec). Each subject stood in a relaxed standing posture, a flat posture, a swayback posture, and a lordosis posture. Subjects maintained the postures for ten seconds with the help of pictures, verbal instructions, and manual guidance while we measuredmuscle activity. Additionally, we placedmarkers in eleven locations, including T1, T7, T12, L3, S2, ASIS, PSIS, the greater trochanter, and the knee joint lateral epicondyle. We took pictures of each posture with a digital camera, and defined each posture by calculating the alignment of the thoracic vertebra, the lumbar, and the pelvis based on the angle change at each. Differences in muscle activity between the two groups were assessed by an independent t-test using SPSS 12.0J. A P-value < 0.05 was considered significant. Results: In the standing posture, there were no significant differences in muscle activity between the two groups. In the flat posture, MF and IT muscle activity was greater in the RLBP group than in the pain-free group (P< 0.05). In the swaybackposture, ITmuscle activitywas greater in theRLBP group than in the pain-free group (P< 0.05). In the lordosis posture, MF muscle activity was greater in the RLBP group than in the pain-free group (P< 0.05). Conclusion(s): Muscle activity increased in global muscles and decreased in local muscles in people with RLBP. However, muscle activity in the upright and lordosis postures suggested that hyperkinesia in the MF, which is a local muscle, plays a role in lumbar lordosis. Furthermore, in the RLBP group, maintenance of vertical stability in the spine seems to be attained not only by the lumbar extensors, but also due to hyperkinesia in the IT,which plays a role in lumbar extension. Implications:This studywill lead to newdevelopments in physical therapy for people with RLBP by clarifying posture control patterns in these patients.

Gender difference in lower limb muscle activity during landing and rapid change of direction

Summary Objectives The purpose of the study was to examine gender differences in lower limb muscle activity during jump landing and rapid change of direction. Equipment and methods Surface electromyography (EMG) of the rectus femoris, biceps femoris and gluteus maximus were recorded for 10 male and 10 female basketball, volleyball or netball players performing five repetitions each of two tasks; (1) landing from a maximal height vertical jump and, (2) 45° rapid change of direction on their dominant leg. Independent sample t -tests were conducted to determine sex differences and paired samples t -tests were conducted to determine task differences in peak EMG muscle activity. Results Rectus femoris muscle activity was significantly greater in females compared to males during jump landings and rapid change of direction. Biceps femoris muscle activity was significantly greater in males compared to females during jump landing. No significant gender differences in gluteus maximus muscle activity were found during jump landings or rapid change of direction. These findings suggest that significant differences in muscle activity of the quadriceps and hamstrings exist between males and females when performing jump landing and change of direction movements, which may place females at greater risk of ACL injury compared to males, for example.

The effects of bag style on muscle activity of the trapezius, erector spinae and latissimus dorsi during walking in female university students.

Back pain is common in adolescents which has been associated with carrying a bag. However, there is little research examining the effects of bag style in female adolescents. The aim of the study was to investigate the effects of different bag conditions on muscle activity of the trapezius, erector spinae and latissimus dorsi muscles in female university students during walking. Twelve female university students walked on a treadmill for 5 minutes at 1.1 m/s during five conditions; control, 1 strapped rucksack, 2 strapped rucksack, ipsilateral shoulder strap and contralateral shoulder strap, each containing 10% bodyweight. Electromyography for the trapezius, erector spinae and latissimus dorsi was recorded for the last 30 s of each condition. Two-way ANOVA and paired t-tests were used to identify differences between right and left muscles and between bag conditions. Results showed that muscle activity of the left trapezius was significantly higher than the right trapezius during the 1 strap rucksack condition. For the left trapezius, the 2 strapped rucksack and the control condition had significantly lower muscle activity compared to the 1 strapped rucksack and the ipsilateral shoulder strap. For the left erector spinae muscle, there was significantly greater muscle activity when wearing the contralateral shoulder strap compared to the control. For the right erector spinae, significantly lower muscle activity was observed when wearing the 2 strapped rucksack compared to the ipsilateral shoulder strap and contralateral shoulder strap. There were no significant differences in muscle activity of the latissimus dorsi muscles between any of the bag conditions. These findings suggest that a two strapped rucksack should be used when carrying loads to reduce spinal muscle activity which may, in turn, reduce reports of back pain in female adolescents.

チェンソーを用いる伐倒作業姿勢の違いが体幹筋群の筋活動量に与える影響

Many forestry workers who use chain-saws suffer from low back pain. Previous studies have reported that low back pain is related to the working postures while felling a tree with a using chain-saws. However, no previous study has investigated trunk muscle activities during work. The purpose of this study was to clarify the relationship between working postures while holding a chain-saw, and trunk muscles activities as measured by surface electromyography (EMG). Subjects were 10 males who were not forestry workers. Four task postures while holding a chain-saw were tested: standing, 30(o) trunk flexion, 90(o) trunk flexion and half-kneeling. EMG recordings were obtained bilaterally of the lumbar paraspinal (LP) muscles and rectus abdominis (RA) muscles. Raw EMG data were processed by integrating the EMG and normalizing them to %MVC. The paired t-test was used to detect statistical differences in the activities between the right and left LP muscles and RA muscles. One-factor repeated measures ANOVA was used to compare the bilateral LP and RA muscle activities among the 4 different postures. The significance level was set to less than 5%. In the half-kneeling posture, the right LP muscle activity was 14.7% higher than the left LP muscle activity (p<0.05); however, there were no significant differences in muscle activities among the other postures. The right LP muscle activity of 30(o) trunk flexion posture was 25.6% higher than that of the standing posture, and 14.2% higher than that of half-kneeling posture (p<0.05). The bilateral LP muscle activities of the 90(o) trunk flexion posture were the highest of the 4 postures, 16.7% higher than the half-kneeling posture (p<0.05) right LP muscle activity. There was a tendency of increase in the left LP muscle activity when trunk flexion angle increased, but no significant differences among the 4 postures were found. The bilateral RA muscle activities were low and did not significantly differ among the 4 postures. This study showed that when the trunk is flexed, the LP muscle activities change asymmetrically, with the right LP muscle activity increasing significantly compared to the standing posture and the half-kneeing posture, but there was no significant difference in the left LP muscle activity. These results suggest that working postures that involve trunk flexion while felling a tree with a holding chain-saw may lead to increased loading of the LP muscles.

Effects of different types of exercise on muscle activity and balance control.

[Purpose] This study analyzed the effects of isotonic, isokinetic, and isometric exercises of ankle joint muscles on lower extremity muscle activity and balance control. [Subjects and Methods] The subjects were 30 healthy adults (15 males) in their 20s who were randomly assigned to three different exercise method groups of 10 people each. The isokinetic exercise group performed three sets at an angular velocity of 60°/sec, including a single rest period after every set of 10 repetitions. The isometric exercise group performed three sets consisting of three 15 repetitions of a 15-second exercise followed by a 5-second rest. [Results] Multivariate analysis of variance revealed that depending on the exercise method, the non-dominant tibialis anterior, gastrocnemius muscle, and peroneus longus showed significant differences in muscle activity for weight-bearing non-dominant sides; when the dominant side was weight-bearing, the dominant gastrocnemius and peroneus longus showed significant differences in muscle activity; and the non-dominant and dominant sides showed significant differences in balance control depending on the duration of support in the area. [Conclusion] Muscle fatigue from the three exercise methods produced a decline in muscle activity and balance control; due to the fatigue before exercise, the side that did not perform the exercises was affected.

Development and Evaluation of Rollator for Elderly Farmers

Objective: This study aims to develop and evaluate a multi-purpose rollator, which may be used as a seat, as a traditional walker, or as a storage basket for elderly farmers. Background: The rollators on the market are not user-friendly designed and seen inconvenient for elderly farmers to use, although they are sold at considerably high price. Since they lack enough space to load stuffs and are not durable or stable enough, they do not seem to be suitable for elderly farmers to use in rural areas. Method: Two types of methods were used in this study. First, the survey consisted of 19 questions was conducted among elderly farmers in rural areas, after using the developed rollator, to evaluate the usability of the rollator developed in this study. Second, EMG experiment was conducted to compare the existing rollator and developed rollator quantitatively. Through this experiment, we tried to verify the differences of muscle responses, when using the traditional and the developed ones, which have their own brake system, in the ramp. Results: The developed rollator was highly evaluated in most of the questions in the usability survey, except for the Weight category in which the opinions were divided into three different types (Worse: 31%, Similar: 30%, Better: 36%). The result of EMG experiment showed that the existing rollator (7.4%MVC) demands more muscle strength than the developed rollator (5.5%MVC) does. By statistically analyzing the results of upper limb and lower limb respectively, we found out that all the muscles except deltoid in upper limb showed statistically significant differences in muscle activity when using the existing and the developed rollator. However, there was no statistical difference in lower limb muscles. Conclusion: The developed rollator in this study has maximized the functionality of the brake system, the storage and the chair, which were pointed out as the weaknesses of existing rollators. Furthermore, the developed rollator is designed to be more user-friendly, safe, durable, and effective for elderly farmers to use in rural areas, where roads are rough and bumpy. Application: We expect that the emergency brake system developed in this study would be utilized for other convenience equipment, such as strollers and carts, and that it would be able to develop and produce more secure and reliable equipment in the future.

Immediate improvements in activation amplitude levels of the deep abdominal muscle following a sacroiliac joint manipulation during rapid upper limb movement

To assess the immediate effects on the electrical activity of the transversus abdominis/internal oblique (TrA/IO) muscle during rapid voluntary upper limb movements before and after a sacroiliac joint (SIJ) manipulation. Twenty healthy subjects who had innominate fixation, assessed by standing flexion test, were recruited. All subjects were submitted to SIJ manipulation and the TrA/IO muscles were evaluated bilaterally, before and after the procedure, through surface electromyography while ten random rapid upper limb flexions or abductions were performed. Normality was accepted, and the paired t-test was used to determine data differences (p < 0.05). The correlations were calculated using Pearson correlation coefficient. All subjects presented an increase of SIJ mobility after manipulation (negative standing flexion test). Significant differences in muscle activation were noted to ipsi- and contralateral TrA/IO recruitment, prior to (A1) and after (A2) the manipulation. The A2 data were statistically greater than those in the A1. The Pearson coefficient revealed a strong correlation between the TrA/IO side and the increase in muscle activation amplitude level. Also, the data showed a moderate to strong correlation between this last variable and the moments of evaluation. The SIJ manipulation immediately improved the electrical activity of the TrA/IO muscle during rapid voluntary upper limb movements, suggesting improved segment stability and an increment to the afferent stimuli in order to affect the motor response.