Variations in abdominal muscle activities of obese females during abdominal bracing exercise in different body positions.

AIMS: This study evaluated the activities of the Rectus Abdominis (RA) and Transversus Abdominis (TrA) muscles during abdominal bracing exercises (ABE) in different body positions. METHODOLOGY: Electrical activities of both components of the RA and TrA muscles were assessed respectively in 25 obese females via surface electromyography during ABE in four (4) different body positions (crook lying, side lying, standing, and sitting). Each trial lasted for five (5) seconds with an hour rest period between trials. RESULTS: Electrical activities of each of the right RA (p = 0.008) and TrA (p = 0.001) muscles significantly varied across the four trials. For the left components of the RA (p = 0.243) and TrA (p = 0.332) muscles, no significant differences were observed across trials. The highest muscular activities were recorded during the standing trial while the crook lying position resulted in the least muscular activities. CONCLUSION: For the best results, abdominal bracing exercises should be performed in a standing position. The efficacy of adopting these body positions for long-term rehabilitation purposes should be investigated in future studies.

Trunk muscle activation in prone plank exercises with different body tilts.

BACKGROUND: Body tilt changes could affect the intensity/difficulty of core stability exercises, but there is still a lack of knowledge about its impact. OBJECTIVE: To analyse the trunk muscles activation during prone plank exercises at different body tilts. METHODS: Twenty-four young adults who performed recreational gymnastic activities participated in this study. Electromyography activity of the rectus abdominis (RA), external oblique (EO), internal oblique (IO) and erector spinae (ES) was recorded during the performance of six variations of the prone plank exercise (planking with feet supported on the ground [conventional horizontal position] and planking with feet supported on wall bars at five different heights increasing the angle tilt) and an inverted position exercise. RESULTS: The RA, EO and IO activation in all prone plank variations were higher than those observed in the conventional prone plank. In addition, the coefficient of variation of the muscle activation increased with the declination angle, reaching the highest values in the inverted position for the RA and ES muscles. CONCLUSION: The results seem to indicate that the body tilt variation could be used as an easy and inexpensive strategy for modulating the neuromuscular demands and the motor control challenge during planking exercises.

Comparison of trunk muscle activity during lumbar stabilization exercises on stable and unstable surfaces.

BACKGROUND: Lumbar stabilization exercises (LSE) provide dynamic trunk stability, promote muscle strength and endurance, and improve low back pain rehabilitation and performance. OBJECTIVE: To clarify the differences in trunk muscle activity during LSEs on stable and different unstable surfaces. METHODS: Fifteen healthy males performed three exercises (elbow-toe, hand-knee, and side bridge) on stable (floor) and unstable surfaces. Muscle activity of the bilateral rectus abdominis, internal oblique, external oblique, and erector spinae were recorded. Data were compared using the Friedman test. Pairwise comparisons were performed using Wilcoxon's signed rank test if significant differences were observed. RESULTS: In the elbow-toe exercise, muscle activity of the rectus abdominis and right internal oblique increased in the following order: floor, low-difficulty, and high-difficulty unstable surface. In the hand-knee exercise, muscle activity of the internal oblique on the lower-extremity elevated side, external oblique, and erector spinae on the upper-extremity elevated side were greater on unstable surface exercise performance. In the side bridge exercise, rectus abdominis muscle activity was highest on a high-difficulty unstable surface. CONCLUSION: Trunk muscle activity increased during exercise on unstable surfaces. Since the effects of unstable surfaces vary depending on muscle and exercise types, exercise difficulty and surface stability must be considered accordingly.

Immediate Effects of Sprinter-Pattern Exercise on the Lordotic Curve and Abdominal Muscle Activity in Individuals with Hyperlordosis.

Background and Objectives: Abdominal muscle exercises with limb movements are more effective for trunk stabilization than traditional exercises involving trunk flexion alone. This study examined the effects of abdominal exercises incorporating sprinter pattern and crunch exercises on changes in the lordotic curve and abdominal muscle activation in individuals with low back pain caused by hyperlordosis resulting from weak abdominal muscles. Materials and Methods: In this single-blind, randomized controlled trial, a total of 40 participants with hyperlordosis were recruited and randomly assigned to perform either sprinter-pattern abdominal exercises or crunch exercises. The participants assigned to each group performed three sets of ten abdominal exercises. The lumbar lordotic angle (LLA) and sacrohorizontal angle (SHA) were assessed prior to and following the intervention, whereas abdominal muscle activity was gauged throughout the intervention period. Changes in the LLA and SHA were measured by radiography. Abdominal muscle activity was measured using electromyography. Results: The LLA and SHA decreased significantly in both groups (p < 0.001), while the sprinter-pattern exercise group showed a statistically significant decrease compared to the crunch exercise group (p < 0.001). In the activity of the abdominal muscles, there was no significant difference in the rectus abdominis muscle between the two groups (p > 0.005). However, a significant difference between the external and internal oblique muscles was observed, and the activities of both muscles were significantly higher in the sprinter-pattern exercise group than in the crunch exercise group (p < 0.005). Conclusions: Abdominal exercise using a sprinter pattern may be effective in reducing lumbar lordosis by strengthening the abdominal muscles in patients with hyperlordosis.

Surface electromyography analysis of core stabilizing muscles during isometric shoulder contractions in athletes with low back pain.

BACKGROUND: The study was carried out in the athletes with and without Low Back Pain (LBP) to determine the surface electromyography activity of core stabilizing muscles while performing isometric shoulder and trunk contractions. STUDY DESIGN: Cross-sectional study. METHODS: This study enlisted the participation of 40 athletes. Group A included 20 athletes (18 males and 2 females) without LBP, and Group B included 20 athletes (12 males and 8 females) with LBP. Athletes with LBP were assessed using the Modified Oswestry Disability Questionnaire (MODQ) and Visual Analog Scale (VAS) to determine their level of disability and pain severity, respectively. EMG activity of the rectus abdominis, external oblique, longissimus, and multifidus was recorded in both groups as they performed bilateral isometric shoulder and trunk contractions. RESULTS: In the LBP group, EMG activity of the rectus abdominis and external oblique muscles was significantly lower (P < 0.05). The LBP group had significantly more multifidus activity (P = 0.03) than the NLBP group. Among all the exercises, bilateral isometric shoulder extension contraction activated the rectus abdominis, right external oblique, and longissimus group of muscles significantly more (P < 0.05) in both groups. In both groups, bilateral isometric shoulder flexion contraction resulted in significantly higher multifidus muscle activation (P = 0.002). CONCLUSION: The activation of core stabilizing muscles was altered in athletes with LBP. When athletes are unable to contract and activate trunk muscles owing to pain, upper extremity exercises can be used to activate these muscles.

An electromyographical comparison of torso muscle activity and ratio during modified side bridge exercises.

BACKGROUND: Individualized exercise programs based on personal impairment could lead to successful rehabilitation. An effective way to train spine stability is to find exercises that take advantage of the synergistic relation between local and global stabilization systems. OBJECTIVE: This study aimed to investigate synergistic relationship between the muscles of the local and global systems during three modified side bridge exercises compared with traditional side bridge (TSB). METHODS: Twenty healthy participants performed TSB, both leg lift while side-lying (BLLS), torso lift on a 45∘ bench while side-lying (TLBS), and pelvic lift on side-lying (PLS) in random order. Surface electromyography data were analyzed. RESULTS: The results indicate that PLS was effective as TSB on trunk muscle activity. However, BLLS and TLBS demonstrated significantly less rectus abdominal (RA) muscle activity compared to TSB (p< .001). Additionally, BLLS and TLBS had a higher internal oblique (IO)/RA muscle activity ratio than TSB (p< .001). CONCLUSIONS: PLS could be a suitable alternative exercise for individuals who are unable to perform TSB, as it can effectively activate trunk muscles. BLLS and TLBS may be appropriate for training the local stability system, while limiting activation of the RA.

Relationship Between Muscle Activity and Force During Suspended Bridge Exercises.

CONTEXT: Isometric core stability exercises are commonly used to target muscles of the lumbopelvic-hip complex, including the rectus abdominis (RA) and erector spinae (ES). These exercises can be implemented in rehabilitation protocols to increase muscle strength and endurance. Difficulty can be progressed by modifying the base of support or adding an unstable element. Load cells can be affixed to suspension training devices to measure force exerted through the straps during exercise. The primary purpose of this study was to assess the relationship between activity of the RA and ES to force measured through a load cell fixed to suspension straps during bilateral and unilateral suspended bridge exercises. DESIGN: Forty asymptomatic, active individuals completed a single laboratory visit. METHODS: Participants completed 2 bilateral suspended bridges and 2 unilateral suspended bridges held to failure. Surface electromyography sensors were placed over the bilateral RA and ES to quantify muscle activity (% maximum voluntary isometric contraction). A load cell was affixed to the suspension straps to measure force exerted through the straps throughout the duration of the exercise. Pearson correlations were used to determine relationships between force and muscle activity of the RA and ES throughout exercise duration. RESULTS: Force was negatively related to RA muscle activity in bilateral suspended bridges (r = -.735 to -.842, P < .001) and unilateral suspended bridges (r = -.300 to -.707, P = .002 to <.001). Force had a positive relationship with ES muscle activity in bilateral suspended bridges (r = .689 to .791, P < .001) and unilateral suspended bridges (r = .418 to .448, P < .001). CONCLUSIONS: Suspended bridge exercises can be a valuable tool to target posterior abdominal musculature such as the ES to contribute to core stability and endurance. Load cells can be applied during suspension training to quantify the interaction between individuals and the exercise equipment.

Side-To-Side Difference in Electromyographic Activity of Abdominal Muscles during Asymmetric Exercises.

A side-to-side difference in the muscle size of the rectus abdominis has been suggested to increase the strain injury risk. Attenuating the difference in size of the rectus abdominis may decrease the injury risk. To explore ways to highly activate one side of the rectus abdominis, we aimed to clarify the activity levels of both sides of the muscle during asymmetric abdominal exercises. Fifteen male sprinters performed the following five asymmetric exercises for the right and left sides: (i) sit-up twist, (ii) oblique leg raise, (iii) side bridge, (iv) side bridge roll out with the elbow, and (v) side bridge roll out with the foot. Side bridge roll out with the elbow and that with the foot were performed using a wheeled platform. During the exercises, electromyographic signals were recorded bilaterally from the upper, central, and lower portions of the rectus abdominis. We calculated the root mean square of electromyograms during the concentric and eccentric phases of the exercises and normalized to that during maximal voluntary contractions. In all portions of the rectus abdominis, the root mean squares of electromyograms were significantly higher in the moving side than in the non-moving side during the concentric and eccentric phases of the side bridge, the side bridge roll out with the elbow and that with the foot (all p < 0.01), but not in sit-up twist or oblique leg raise. The root mean squares of electromyograms of all portions of the rectus abdominis in the moving side were significantly higher in the side bridge roll out with the elbow and that with the foot than in the side bridge during both phases (all p < 0.01). The results suggest that the application of the wheeled platform to side bridge is useful to highly activate one side of the rectus abdominis.

Changes in Trunk Muscle Activity during Unilateral Weight Bearing and Abnormal Postural Gait in Healthy Individuals.

Background and Objectives: Many people tend to carry their bags or baggage on only one side of their body. Due to smartphone use, people also tend to walk bent forward in a kyphotic posture. In this study, we aimed to assess trunk muscle activity changes due to weight-bearing, carried in the left or right hand, and using three different gait postures. Materials and Methods: We recruited 27 healthy participants (aged 19−75 years) with no history of LBP within the last 6 months before study participation. Electromyographic activities of the lower back and the abdominal muscles of the participants were evaluated using four-channel surface electromyography (EMG). Surface EMG recordings were obtained from four trunk muscles, including the flexor (rectus abdominis (RA), external oblique (EO)) and extensor muscles (lumbar erector spinae (LE), and the superficial lumbar multifidus (LM)), during unilateral weight-bearing tasks and with different gait postures (normal gait, with a sway back, and thoracic kyphosis). Results: In the "unilateral weight-bearing task", there was a significant difference in the activity of all the trunk muscles between the weight-bearing limb side and the opposite side (p < 0.05). The activation of the left trunk muscle was greater than that of the right trunk muscle when the dumbbell was lifted using the right hand. The other side showed the same result. In the "gait posture task" performed by the participants using a sway-back posture, the RA and EO had a higher level of activity in the stance and swing phases compared with that in a neutral gait (p < 0.05). Moreover, in the participants with a thoracic kyphosis posture, the LE and LM had a higher level of activity compared with that in a neutral gait (p < 0.05). Conclusions: Our results indicate that abnormal gait posture and unilateral weight-bearing tasks may impair the balance of trunk muscles, increasing the incidence of LBP. However, further large-scale, prospective, controlled studies are warranted to corroborate our results.

Investigation of Structural Changes in Rectus Abdominis Muscle According to Curl-Up Angle Using Ultrasound with an Extended Field of View.

The rectus abdominis (RA) muscle is related to abdominal muscle contraction and is divided into three sub-sections. In this study, changes in each section according to the curl-up angles were measured using ultrasound with an extended field of view (EFOV) scan and compared with the conventional scan. The results showed that the locations of the measurement position center were consistently detected only with the EFOV scan and that the change ratios in thickness and length between sections at the same angles were not significantly different, suggesting that each section was selectively activated. Furthermore, the ratios of the thickness and length changes in each section were significantly different between the rest position and curl-up angles. Specifically, in the section 2 there was a significant difference in the thickness and length changes between different angles, reflecting the characteristics of RA during contraction, and their variations were less than in the section 3. Therefore, the results suggest that changes in only a section of RA cannot be representative of overall RA activation, EFOV scan method can be useful for investigating the structural characteristics of RA in detail, and the proposed method can obtain various information about muscle contraction for efficient muscle treatment and muscle strengthening.

Influence of Loads and Loading Position on the Muscle Activity of the Trunk and Lower Extremity during Squat Exercise.

This study aimed to investigate the effect of the load and bar position on trunk and lower extremity muscle activity during squat exercise. High bar back squats (HBBS) and low bar back squats (LBBS) were performed in random order at 50%, 60%, and 70% loads of one repetition maximum by 28 experienced healthy adult men who had been performing squats for at least one year. Before the experiment, the maximal voluntary contraction of the vastus medialis, vastus lateralis, rectus femoris, biceps femoris, rectus abdominis, transverse abdominis, external oblique, and erector spinae muscles was measured by means of surface electromyography. In addition, eccentric and concentric exercises were performed for 3 s each to measure the muscle activity. There was a significant difference in muscle activity according to the load for all muscles in the eccentric and concentric phases (p < 0.05), indicating that muscle activity increased as the load increased. In addition, in the comparison between HBBS and LBBS, significant differences were shown in all lower extremity muscles and all trunk muscles except for the external oblique in the concentric phase according to the bar position (p < 0.05). HBBS showed a higher muscle activity of the lower extremity in the eccentric and concentric phases than in LBBS, while LBBS showed a higher muscle activity of the trunk muscle in the eccentric and concentric phases than in HBBS (p < 0.05). HBBS requires more force in the lower extremity than LBBS and is particularly advantageous in strengthening the muscular strength of the quadriceps. In contrast, LBBS requires more muscle activity in the trunk than HBBS and is more effective in carrying heavier loads because of the advantage of body stability. This study suggests that rehabilitation experts apply the bar position and load as important variables affecting the intensity and method of training for target muscle strengthening of the lower extremities and trunk.

Core musculature co-contraction during suspension training exercises.

Suspension training reportedly enhances core musculature co-contraction. This study investigated whether the use of a suspension trainer increases core musculature co-activation during exercises vs. its floor counterpart. Participants were 25 healthy volunteers (16 men, 9 women; age: 27.24 ± 4.02 years). Wireless electromyography electrodes were placed bilaterally at the rectus abdominis (RA), erector spinae (ES), and abdominal obliques (OB). Test order (push-up, bridge, and prone plank) was randomized (exercise and condition) with a 3-min rest period between tests. Co-contraction ratios between muscle groups were estimated by root mean square. Ratios (RA/ES, RA/OB, ES/OB) were analyzed using paired t-tests (P ≤ .05). For all floor exercises, co-contraction of core musculature was significantly higher than suspension trainer. During suspension training, perturbations due to increased agonist activation without similar increases in antagonists may be too intense for untrained or injured individuals. Individuals lacking muscle control to recruit muscles concurrently may benefit from mastering traditional floor exercises to promote joint stiffness and stability before suspension trainer exercises.

Application of Feedback Type on Performance of Abdominal Drawing-In Maneuver in Healthy Adults: A Quasi-Experimental Study of Motor Control and Motor Learning.

OBJECTIVE: The aim of this study was to compare the effects of verbal, tactile-verbal, and visual feedback on muscle activation of the lumbar stabilizers relative to extremity movers during an abdominal drawing-in maneuver when feedback is withheld. METHODS: This quasi-experimental study equally divided 54 healthy adults into 3 feedback groups (verbal, tactile-verbal, and visual) who trained twice per week over a 4-week period to perform supine abdominal drawing-in maneuvers. The percentage of maximum voluntary isometric contraction of rectus abdominis, multifidus (MF), erector spinae, and hamstrings (HS) as an outcome measure was acquired using surface electromyography. A 2-way factorial analysis of variance with bootstrapping allowed for comparison of post-pre difference scores across the interaction of feedback and muscle groups. RESULTS: Hamstring activation decreased in those receiving tactile-verbal feedback relative to an increase in participants given visual feedback. Furthermore, when using verbal feedback, HS activity increased relative to a decline in rectus abdominis, and when presenting visual feedback, HS activity increased relative to a decrease in MF. However, no post-pre changes were seen across muscles with tactile-verbal feedback. CONCLUSION: Although tactile-verbal feedback did not increase MF recruitment, it produced less HS activity than visual feedback. Undesirable HS recruitment may reflect boredom or feedback dependency.

Abdominal Muscle Use During Spontaneous Breathing and Cough in Patients Who Are Mechanically Ventilated: A Bi-center Ultrasound Study.

BACKGROUND: Ultrasound may be useful to assess the structure, activity, and function of the abdominal muscles in patients who are mechanically ventilated. RESEARCH QUESTION: Does measurement of abdominal muscle thickening on ultrasound in patients who are mechanically ventilated provide clinically relevant information about abdominal muscle function and weaning outcomes? STUDY DESIGN AND METHODS: This study consisted of two parts, a physiological study conducted in healthy subjects and a prospective observational study in patients who were mechanically ventilated. Abdominal muscle thickness and thickening fraction were measured during cough and expiratory efforts in 20 healthy subjects, and prior to and during a spontaneous breathing trial in 57 patients being ventilated. RESULTS: In healthy subjects, internal oblique and rectus abdominis thickening fraction correlated with pressure generated during expiratory efforts (P < .001). In patients being ventilated, abdominal muscle thickness and thickening fraction were feasible to measure in all patients, and reproducibility was moderately acceptable. During a failed spontaneous breathing trial, thickening fraction of transversus abdominis and internal oblique increased substantially from baseline (13.2% [95% CI, 0.9-24.8] and 7.2% [95% CI, 2.2-13.2], respectively). The combined thickening fraction of transversus abdominis, internal oblique, and rectus abdominis measured during cough was associated with an increased risk of reintubation or reconnection to the ventilator following attempted liberation (OR, 2.1; 95% CI, 1.1-4.4 per 10% decrease in thickening fraction). INTERPRETATION: Abdominal muscle thickening on ultrasound was correlated to the airway pressure generated by expiratory efforts. In patients who were mechanically ventilated, abdominal muscle ultrasound measurements are feasible and moderately reproducible. Among patients who passed a spontaneous breathing trial, reduced abdominal muscle thickening during cough was associated with a high risk of liberation failure. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT03567564; URL: www.clinicaltrials.gov.

Understanding the impact of lumbar disc degeneration and chronic low back pain: A cross-sectional electromyographic analysis of postural strategy during predicted and unpredicted postural perturbations.

People with chronic low back pain (LBP) exhibit changes in postural control. Stereotypical muscle activations resulting from external perturbations include anticipatory (APAs) and compensatory (CPAs) postural adjustments. The aim and objective of this study was to determine differences in postural control strategies (peak amplitude, APAs and CPAs) between symptomatic and asymptomatic adults with and without Lumbar Disc Degeneration (LDD) using surface electromyography during forward postural perturbation. Ninety-seven subjects participated in the study (mean age 50 years (SD 12)). 3T MRI was used to acquire T2 weighted images (L1-S1). LDD was determined using Pfirrmann grading. A bespoke translational platform was designed to deliver horizontal perturbations in sagittal and frontal planes. Electromyographic activity was analysed bilaterally from 8 trunk and lower limb muscles during four established APA and CPA epochs. A Kruskal-Wallis H test with Bonferroni correction for multiple comparisons was conducted. Four groups were identified: no LDD no pain (n = 19), LDD no pain (n = 38), LDD pain (n = 35) and no LDD pain (n = 5). There were no significant differences in age or gender between groups. The most significant difference between groups was observed during forward perturbation. In the APA and CPA phases of predictable forward perturbation there were significant differences ankle strategy between groups (p = 0.007-0.008); lateral gastrocnemius and tibialis anterior activity was higher in the LDD pain than the LDD no pain group. There were no significant differences in the unpredictable condition (p>0.05). These findings were different from the remaining groups, where significant differences in hip strategy were observed during both perturbation conditions (p = 0.004-0.006). Symptomatic LDD patients exhibit different electromyographic strategies to asymptomatic LDD controls. Future LBP electromyographic research should benefit from considering assessment of both lower limbs in addition to the spine. This approach could prevent underestimation of postural control deficits and guide targeted rehabilitation.

Treatment of rectus sheath hematomas: Eight years of single-center experience with a review of literature.

BACKGROUND: Rectus sheath hematoma is a rare and frequently misdiagnosed cause of acute abdominal pain. In the management of the patients with rectus sheath hematoma, which are mostly with advanced age and comorbid diseases, positive results can be obtained by avoiding unnecessary surgical procedures with correct diagnosis and treatment approaches. The presented study aims to contribute to the lack of algorithms and optimal treatment strategies in the management of rectus sheath hematoma patients with the description of our experience in their management. METHODS: Patients who underwent treatment with the diagnosis of rectus sheath hematoma between May 2010 and July 2018 were retrospectively analyzed. Demographic characteristics, medical histories, physical and laboratory findings and imaging methods, treatment processes, complications, morbidity, mortality, length of hospitalization and long-term follow-up results were searched. Data were analyzed from patient files, hospital computer registry system and radiology archives. Data analysis was performed using Microsoft Excel and IBM-SPSS-Statistics-24. RESULTS: The mean age of the 31 patients was 63.03 years (24-85 years). The female/male ratio (21/10) was 2.1. The most common presenting sign or symptom was abdominal pain (100%), followed by abdominal wall mass in 25 patients (80.6%). Twenty-five patients (80.6%) were receiving some form of anticoagulation and antiplatelet therapy. Diagnosis was confirmed by Computed Tomography in 11 (45.4%), Ultrasonography in five (16.1%) and Computed Tomography with Ultrasonography in 15 (33.3%). Eight patients (25.8%) were evaluated as Type-1, 10 (32.2%) as Type-2 and 13 (41.9%) as Type-3. Mean International Normalized Ratio (INR) value of patients was 2.59. Bleeding was controlled by surgery in three cases (9.6%). The conservative approach was preferred in 28 cases (90.3%). 29 (93.5%) patients were discharged after an average hospital stay of 7.48 days (4-21). One patient died on the postoperative 5th day and other on the 14th day of conservative treatment (6.45% mortality). The mortality rate of conservatively and surgically treated patients was 3.5% and 33.3%, respectively. CONCLUSION: Rectus sheath hematoma should be suspected in elderly patients using anticoagulants with acute abdominal pain, severe cough attacks and an umbilical palpable or radiologically supported mass. Computed Tomography and Ultrasonography should be performed in case of clinical suspicion. Early and correct diagnosis ensures successful conservative treatment and prevents unneces-sary surgical procedures. In the management of cases where clinician experience is at the forefront, we are hopeful that a new effective algorithm system and guidelines for the diagnosis will be identified after increasing the presentations of case series and experiences.

Influence of Abdominal Hollowing Maneuver on the Core Musculature Activation during the Prone Plank Exercise.

This cross-sectional study of repeated measures investigated whether integrating the abdominal hollowing maneuver (AHM) into the prone plank performance is an effective strategy for increasing both the activation of the deep and superficial core musculature. Electromyographical (EMG) responses of rectus abdominis (RA), external oblique (EO), internal oblique (IO), and lumbar erector spinae (LES), and ratings of perceived exertion (RPE) of 20 participants (13 male, 7 female; mean ± standard deviation (SD) age: 24.25 ± 3.54 years; body mass: 66.42 ± 8.40 kg; height: 1.70 ± 9.51 m) were compared across two experimental conditions: the traditional prone plank (STANDARD); and a variation including the AHM (HOLLOWING). Regarding Total Intensity, HOLLOWING resulted in significantly greater EMG response than STANDARD (p < 0.001; Effect size (ES) = 3.01). Specifically, RA showed no significant differences between STANDARD and HOLLOWING (p = 0.056; ES = 0.285). However, for the remaining analyzed muscles, HOLLOWING significantly provided higher EMG activation compared to STANDARD (LES: p = 0.004; ES = 0.619; left EO: p < 0.001; ES = 1.031; right EO: p < 0.001; ES = 1.419; left IO: p < 0.001; ES = 2.021; right IO: p < 0.001; ES = 2.269). Regarding RPE, HOLLOWING reported values significantly greater than STANDARD (p < 0.001; ES = 2.94). In conclusion, integrating the AHM into the prone plank exercise enhances overall abdominal activity, particularly in both obliques. These findings provide updated guidelines for lumbar stabilization and core strengthening in health-related physical fitness programs.

Trunk muscle activity during different types of low weighted squat exercises in normal and forefoot standing conditions.

Squats are considered a useful basic exercise for trunk muscle activation. To gain knowledge about trunk muscle activity patterns depending on the barbell position in beginners, we examined squats with low weights in the back, front, and overhead position. METHODS: Twelve healthy adults (6 women/6 men, age: 29.1 (SD 8.0) y, height: 173.4 (6.9) cm, body mass: 70.1 (9.1) kg) randomly performed the three barbell squats in normal and in forefoot standing. Surface electromyography from external (EO) and internal oblique, rectus abdominis, and erector spinae (ES) was recorded. The centre of pressure path length (CoP) and the motion of the lumbar spine were captured. RESULTS: The overhead squat revealed the highest percent muscle activity, where EO (p = 0.009) and ES (p = 0.03) showed the greatest activity. Forefoot standing did not change overall trunk muscle activities (.05< Hedges' g <.29, 0.17 < p < 0.95) although longer CoP path length (.45 < g < 1.3, p < 0.05) was measured. CONCLUSIONS: Squat exercises with low weight are useful to activate trunk muscles. Activity increases with the difficulty of the squat by frontal or overhead loading, but not by standing on the forefoot. The low weighted squat can target well core muscle activity in training with beginners or in rehabilitation.

The Effect of Respiratory Phase on Abdominal Muscle Activity During Stable and Unstable Sitting Positions in Individuals With and Without Chronic Low Back Pain.

OBJECTIVE: The aim was to assess the abdominal muscle activities during inspiration and expiration at different sitting positions in individuals with and without chronic low back pain (CLBP). METHODS: This study was conducted on 36 participants (18 with CLBP and 18 healthy controls). Ultrasound imaging was used to assess thickness changes of the transverse abdominis, internal oblique, rectus abdominis, and external oblique muscles. Muscle thickness was measured during inspiration and expiration under 3 different stability levels: sitting on a chair, sitting on a gym ball, and sitting on a gym ball with lifting the left foot. The muscle thickness measured in these positions was normalized to the actual muscle thickness at rest in supine lying and presented as a percentage of thickness change. RESULTS: Both groups displayed greater abdominal muscle activities as the stability of the surface decreased during both respiratory phases. However, compared with the healthy controls, the CLBP group showed smaller muscle thickness changes in all abdominal muscles, except the external oblique, in both respiration phases while sitting on a gym ball with lifting the left foot. The CLBP group displayed overactivity of the rectus abdominis muscle relative to the healthy controls while sitting on a chair in both respiratory phases. CONCLUSION: The findings of the study indicate that as the stability of the support surface decreases, individuals with CLBP had more difficulty activating all abdominal muscles in a similar manner compared to healthy controls in both respiratory phases, which might affect both respiration and postural stability.

Internal consistencies of the delayed trunk muscle reaction times following a treadmill-induced slip perturbation while holding and not holding a tray.

BACKGROUND: Reaction time task performance using electromyography (EMG) has been widely studied in the evaluation of motor responses. However, specific testing conditions with tray usage and the reliability of the bilateral trunk muscle reactions have not been proven. RESEARCH QUESTIONS: Are there internal consistencies of the reaction times for a particular condition, such as a handheld task, among the examiners? Is there a delayed reaction time on the dominant abdominal muscle in response to a treadmill-induced slip perturbation while holding or not holding a tray? METHODS: One hundred and nineteen right upper and lower limb dominant individuals (71 female and 48 male subjects) were exposed to a treadmill-induced slip perturbation (0.24 m/s velocity for 1.2 cm) for 0.10 s in standing. The EMG electrodes were placed on both sides of the rectus abdominis (RA) and erector spinae (ES) muscles. The reliability of the test was established by using Cronbach's alpha, intra-class correlation coefficients (ICC2, k), and the standard error of measurements. RESULTS: The results for holding a tray indicated a high degree of consistency based on Cronbach's alpha for the left RA (0.79), right RA (0.86), left ES (0.82), and right ES (0.73) muscles. However, there was a significant reaction time difference among trunk muscles (F = 10.58, p = 0.002) while not holding a tray. The post-hoc results indicated that the right RA muscle was delayed more than the bilateral ES muscles, although there was no significant difference with the left RA muscle. SIGNIFICANCE: Overall, the EMG analyses for the reaction times were highly consistent with and without tray usage. The reaction times of the dominant abdominal muscles were delayed while not holding a tray. Given the high reliability, compensatory strategies by trunk dominance might be considered with a tray usage task.