The effects of various stair-climbing exercises on functional mobility and trunk muscle activation in community-dwelling older adults: A pilot randomized controlled trial.

BACKGROUND: Stair-climbing (SC) is an essential daily life skill, and stair-climbing exercise (SCE) serves as a valuable method for promoting physical activity in older adults. This study aimed to compare the impact of SCEs with heel contact (HC) and heel off (HO) during SC on functional mobility and trunk muscle (TM) activation amplitudes in community-dwelling older adults. METHODS: In the pilot randomized controlled trial, participants were randomly allocated to either the HC group (n = 17; mean age 75.9 ± 6.3 years) or the HO group (n = 17; mean age 76.5 ± 4.6 years). The HC participants performed SCE with the heel of the ankle in contact with the ground, while the HO participants performed SCE with the heel of the ankle off the ground during SC. Both groups participated in progressive SCE for one hour per day, three days per week, over four consecutive weeks (totaling 12 sessions) at the community center. We measured timed stair-climbing (TSC), timed up and go (TUG), and electromyography (EMG) amplitudes of the TMs including rectus abdominis (RA), external oblique (EO), transverse abdominus and internal oblique abdominals (TrA-IO), and erector spinae (ES) during SC before and after the intervention. RESULTS: Both groups showed a significant improvement in TSC and TUG after the intervention (P < .01, respectively), with no significant difference between the groups. There was no significant difference in the EMG activity of the TMs between the groups after the intervention. The amplitude of TMs significantly decreased after the intervention in both groups (P < .01, respectively). CONCLUSION: Both SCE methods could improve balance and SC ability in older adults while reducing the recruitment of TMs during SC. Both SCE strategies are effective in improving functional mobility and promoting appropriate posture control during SC in older adults.

Stimulus zones of Vojta method and trunk control in children with spastic-type cerebral palsy: A quasi-experimental pilot study.

BACKGROUND: Vojta method improves motor function by inducing a response by pressing the stimulus zones. PURPOSE: To determine the effect of the stimulus zones on trunk muscle thickness, trunk control, trunk angle, and gross motor function in children with spastic-type cerebral palsy. METHODS: A quasi-experimental pilot study was conducted with 19 children with spastic-type cerebral palsy divided into two groups: Vojta method group (n = 10) and general physical therapy group (n = 9). Each group underwent a 6-week intervention, and assessments were conducted to evaluate abdominal muscle thickness, trunk control, trunk angle, and gross motor function. RESULTS: In the Vojta method group, the change rate in the thickness of the internal oblique and transversus abdominis increased significantly within the group (P < 0.05) and the difference (post-pre) of the transversus abdominis was higher (P < 0.05). The trunk angle increased significantly within the group when thoracic 7 and 11, lumbar 3, and sacrum 1 were supported (P < 0.05). There was a significant difference in trunk angle difference (post-pre) between groups when thoracic 11 and sacrum 1 were supported (P < 0.05). Segmental assessment of trunk control and gross motor function measure-88 scores were significantly increased within the group in all groups (P < 0.05). CONCLUSION: The stimulus zones of the Vojta method could improve trunk control in children with spastic-type cerebral palsy through intra-abdominal pressure and anti-gravity movement.

Maximum trunk tip force assessment related to trunk position and prehensile 'fingers' implication in African savannah elephants.

African elephants have a wide range of abilities using their trunk. As a muscular hydrostat, and thanks to the two finger-like processes at its tip, this proboscis can both precisely grasp and exert considerable force by wrapping. Yet few studies have attempted to quantify its distal grasping force. Thus, using a device equipped with force sensors and an automatic reward system, the trunk tip pinch force has been quantified in five captive female African savanna elephants. Results showed that the maximum pinch force of the trunk was 86.4 N, which may suggest that this part of the trunk is mainly dedicated to precision grasping. We also highlighted for the first time a difference in force between the two fingers of the trunk, with the dorsal finger predominantly stronger than the ventral finger. Finally, we showed that the position of the trunk, particularly the torsion, influences its force and distribution between the two trunk fingers. All these results are discussed in the light of the trunk's anatomy, and open up new avenues for evolutionary reflection and soft robot grippers.

Muscle Strength Asymmetries of the Lower Limbs and Trunk in Ballet Dancers.

BACKGROUND: Ballet dancers are expected to use their bodies symmetrically during training, because dance movements are performed on both sides. However, there is a general belief that ballet training encourages the use of one side of the body more than the other. Frequent repetition of a particular exercise can lead to body asymmetries and musculoskeletal injuries. The aim of this cross-sectional study was to investigate the presence of lower limbs and trunk muscle strength asymmetries in ballet dancers and secondly to assess whether there is a difference between professional dancers and ballet students. METHODS: Ballet students (n=19) and professional ballet dancers (n=23) performed maximal voluntary isometric contractions of the trunk (flexion, extension, lateral flexion), hip (flexion, extension, adduction, abduction, external and internal rotation), knee (flexion, extension) and ankle (flexion, extension) on isometric dynamometer. RESULTS: The results showed that the percentage of ballet dancers with contralateral muscle strength asymmetries >10% ranged from 22.5% (ballet students) to 31.6% (professional dancers). The percentage of ballet dancers deviating by >10% from the normative maximum torque agonist/antagonist ratio ranged from 56.5% to 100%. A statistically significant difference between ballet students and professional ballet dancers was found in the trunk flexion/extension ratio (t(40) = -3 .55; p = 0.001; d = 0.55). CONCLUSION: This study revealed strength asymmetries in the lower limbs and trunk in ballet dancers, both professionals and students. Further research is needed to develop appropriate complementary exercise to address and eliminate asymmetries in muscle strength in ballet dancers.

Towards an accurate rolling resistance: Estimating intra-cycle load distribution between front and rear wheels during wheelchair propulsion from inertial sensors.

Accurate assessment of rolling resistance is important for wheelchair propulsion analyses. However, the commonly used drag and deceleration tests are reported to underestimate rolling resistance up to 6% due to the (neglected) influence of trunk motion. The first aim of this study was to investigate the accuracy of using trunk and wheelchair kinematics to predict the intra-cyclical load distribution, more particularly front wheel loading, during hand-rim wheelchair propulsion. Secondly, the study compared the accuracy of rolling resistance determined from the predicted load distribution with the accuracy of drag test-based rolling resistance. Twenty-five able-bodied participants performed hand-rim wheelchair propulsion on a large motor-driven treadmill. During the treadmill sessions, front wheel load was assessed with load pins to determine the load distribution between the front and rear wheels. Accordingly, a machine learning model was trained to predict front wheel load from kinematic data. Based on two inertial sensors (attached to the trunk and wheelchair) and the machine learning model, front wheel load was predicted with a mean absolute error (MAE) of 3.8% (or 1.8 kg). Rolling resistance determined from the predicted load distribution (MAE: 0.9%, mean error (ME): 0.1%) was more accurate than drag test-based rolling resistance (MAE: 2.5%, ME: -1.3%).

Unanticipated mid-flight external trunk perturbation increased frontal plane ACL loading variables during sidestep cuttings.

Unanticipated trunk perturbation is commonly observed when anterior cruciate ligament (ACL) injuries occur during direction-changing manoeuvres. This study aimed to quantify the effect of mid-flight medial-lateral external trunk perturbation directions/locations on ACL loading variables during sidestep cuttings. Thirty-two recreational athletes performed sidestep cuttings under combinations of three perturbation directions (no-perturbation, ipsilateral-perturbation, and contralateral-perturbation relative to the cutting leg) and two perturbation locations (upper-trunk versus lower-trunk). The pushing perturbation was created by customised devices releasing a slam ball to contact participants near maximum jump height prior to cutting. Perturbation generally resulted in greater peak vertical ground reaction force and slower cutting velocity. Upper-trunk contralateral perturbation showed the greatest lateral trunk bending away from the travel direction, greatest peak knee flexion and abduction angles, and greatest peak internal knee adduction moments compared to other conditions. Such increased ACL loading variables were likely due to the increased lateral trunk bending and whole-body horizontal velocity away from the cutting direction caused by the contralateral perturbation act at the upper trunk. The findings may help understand the mechanisms of indirect contact ACL injuries and develop effective cutting techniques for ACL injury prevention.

Gender-specific reference values of dynamometric and non-dynamometric trunk performance in individuals with different body fat percentages: A preliminary study.

Trunk muscles maintain steady effort with adequate strength and endurance. When the muscle performance is subpar, it might cause lower back discomfort. No reference for trunk strength and endurance has been established previously. The aim of this study was to determine the normative reference values for dynamometric and non-dynamometric tests in people with various body fat percentages. Two hundred sixty-four participants aged 19-40 years old were recruited in this cross-sectional study. The Siri equation was used to calculate the individuals body fat proportions, which were divided into normal, high, and very high body fat for men and women. The Modified Sorenson's and the Back-Leg-Chest Dynamometric tests were utilized to measure muscular performance. The means of strength in females with normal, high, and very high body fat percentages were 27.39, 25.75, and 25.37 N/m2, respectively. The males in the same category had the means of 56.48, 51.79, and 60.17 N/m2, respectively. The highest mean of endurance in females was in those with normal body fat percentage (42.28), so did males (71.02). Our findings suggest that males had higher trunk muscle strength and endurance than females, and normal-body-fat individuals had the greatest endurance regardless of gender.

Assessment of Isokinetic Trunk Muscle Strength and Fatigue Rate in Individuals after Bariatric Surgery.

Background and Objectives: Lean body mass loss after bariatric surgery (BS) is remarkable, despite an effective long-term mass reduction and significant declines in comorbidities. A person's functional capacity is adversely affected when their skeletal muscle strength declines by up to 30%. This study aimed to assess the isokinetic trunk muscle strength and fatigue rate in individuals after BS. Materials and Methods: This study included fifty-eight patients, both male and female, ranging in age from 19 to 45. Twenty-seven individuals had BS and twenty-seven healthy people served as the control group. The primary outcomes were the measurement of the concentric and eccentric isokinetic muscle strength of the trunk flexor and extensor muscles. An isokinetic dynamometer (Biodex Rehabilitation and Testing System 3) was used for the assessment of the isokinetic muscle strength. Noraxon EMG was used to determine a secondary outcome, which was the median frequency slop (MF/time) and root mean square slop (RMS/time) of the lumbar erector spinea muscle at 50% of the Maximum Voluntary Isometric Contraction (MVIC). Outcome measures were assessed for both groups. Results: Compared to the control group, the bariatric group showed a lower mean value of both concentric and eccentric isokinetic muscle strength for the flexor and extensor trunk muscles (p < 0.05). In terms of the EMG fatigue rate, the RMS slope increased significantly more than that of the control group, while the MF slope decreased (p > 0.05). Conclusions: The current study found that, in comparison to the healthy subjects, the BS group showed reduced levels of fatigue and isokinetic strength in the trunk muscles. Based on these results, it is recommended that individuals who underwent BS take part in tailored rehabilitation programs to avoid potential musculoskeletal issues in the future.

Either Autonomy Support or Enhanced Expectancies Delivered Via Virtual-Reality Benefits Frontal-Plane Single-Leg Squatting Kinematics.

Our purpose in this study was to determine the effects of a virtual reality intervention delivering specific motivational motor learning manipulations of either autonomy support (AS) or enhanced expectancies (EE) on frontal plane single-leg squatting kinematics. We allocated 45 participants (21 male, 24 female) demonstrating knee, hip, and trunk frontal plane mechanics associated with elevated anterior cruciate ligament injury risk to one of three groups (control, AS, or EE). Participants mimicked an avatar performing five sets of eight repetitions of exemplary single-leg squats. AS participants were given the added option of choosing the color of their avatar. EE participants received real-time biofeedback in the form of green highlights on the avatar that remained on as long as the participant maintained pre-determined 'safe' frontal plane mechanics. We measured peak frontal plane knee, hip, and trunk angles before (baseline) and immediately following (post) the intervention. The control group demonstrated greater increases in knee abduction angle (Δ = +2.3°) than did the AS (Δ = +0.1°) and EE groups (Δ = -0.4°) (p = .003; η2p = .28). All groups demonstrated increased peak hip adduction (p = .01, ηp2 = .18) (control Δ = +1.5°; AS Δ = +3.2°; EE Δ = +0.7°). Hip adduction worsened in all groups. AS and EE motivation strategies appeared to mitigate maladaptive frontal plane knee mechanics.

Evaluation of trunk muscle coactivation predictions in multi-body models.

Musculoskeletal simulations with muscle optimization aim to minimize muscle effort, hence are considered unable to predict the activation of antagonistic muscles. However, activation of antagonistic muscles might be necessary to satisfy the dynamic equilibrium. This study aims to elucidate under which conditions coactivation can be predicted, to evaluate factors modulating it, and to compare the antagonistic activations predicted by the lumbar spine model with literature data. Simple 2D and 3D models, comprising of 2 or 3 rigid bodies, with simple or multi-joint muscles, were created to study conditions under which muscle coactivity is predicted. An existing musculoskeletal model of the lumbar spine developed in AnyBody was used to investigate the effects of modeling intra-abdominal pressure (IAP), linear/cubic and load/activity-based muscle recruitment criterion on predicted coactivation during forward flexion and lateral bending. The predicted antagonist activations were compared to reported EMG data. Muscle coactivity was predicted with simplified models when multi-joint muscles were present or the model was three-dimensional. During forward flexion and lateral bending, the coactivation ratio predicted by the model showed good agreement with experimental values. Predicted coactivation was negligibly influenced by IAP but substantially reduced with a force-based recruitment criterion. The conditions needed in multi-body models to predict coactivity are: three-dimensionality or multi-joint muscles, unless perfect antagonists. The antagonist activations are required to balance 3D moments but do not reflect other physiological phenomena, which might explain the discrepancies between model predictions and experimental data. Nevertheless, the findings confirm the ability of the multi-body trunk models to predict muscle coactivity and suggest their overall validity.

Increasing cadence with a metronome and running barefoot changes the sagittal kinematics of the lower limbs and trunk.

The purpose was to compare two non-laboratory based running retraining programs on lower limb and trunk kinematics in recreational runners. Seventy recreational runners (30 ± 7.3 years old, 40% female) were randomised to a barefoot running group (BAR), a group wearing a digital metronome with their basal cadence increased by 10% (CAD), and a control group (CON). BAR and CAD groups included intervals from 15 to 40 min over 10 weeks and 3 days/week. 3D sagittal kinematics of the ankle, knee, hip, pelvis, and trunk were measured before and after the retraining program, at comfortable and high speeds. A 3 × 2 mixed ANOVA revealed that BAR and CAD groups increased knee and hip flexion at footstrike, increased peak hip flexion during stance and flight phase, decreased peak hip extension during flight phase, and increased anterior pelvic tilt at both speeds after retraining. In addition, BAR increased ankle plantar flexion at footstrike and increased anterior trunk tilt. Both retraining programs demonstrated significant moderate to large effect size changes in parameters that could reduce the mechanical risks of injury associated with excessive knee stress, which is of interest to coaches, runners and those prescribing rehabilitation and injury prevention programs.

Effects of added trunk load on the in vivo kinematics of talocrural and subtalar joints during landing.

BACKGROUND: Landing from heights is a common movement for active-duty military personnel during training. And the additional load they carry while performing these tasks can affect the kinetics and ankle kinematic of the landing. Traditional motion capture techniques are limited in accurately capturing the in vivo kinematics of the talus. This study aims to investigate the effect of additional trunk load on the kinematics of the talocrural and subtalar joints during landing, using a dual fluoroscopic imaging system (DFIS). METHODS: Fourteen healthy male participants were recruited. Magnetic resonance imaging was performed on the right ankle of each participant to create three-dimensional (3D) models of the talus, tibia, and calcaneus. High-speed DFIS was used to capture the images of participants performing single-leg landing jumps from a height of 40 cm. A weighted vest was used to apply additional load, with a weight of 16 kg. Fluoroscopic images were acquired with or without additional loading condition. Kinematic data were obtained by importing the DFIS data and the 3D models in virtual environment software for 2D-3D registration. The kinematics and kinetics were compared between with or without additional loading conditions. RESULTS: During added trunk loading condition, the medial-lateral translation range of motion (ROM) at the talocrural joint significantly increased (p < 0.05). The subtalar joint showed more extension at 44-56 ms (p < 0.05) after contact. The subtalar joint was more eversion at 40-48 ms (p < 0.05) after contact under the added trunk load condition. The peak vertical ground reaction force (vGRF) significantly increased (p < 0.05). CONCLUSIONS: With the added trunk load, there is a significant increase in peak vGRF during landing. The medial-lateral translation ROM of the talocrural joint increases. And the kinematics of the subtalar joint are affected. The observed biomechanical changes may be associated with the high incidence of stress fractures in training with added load.

Magnification in preclinical procedures: effect on muscle activity and angular deviations of the neck and trunk.

Objectives: This study aimed to assess the effects of different magnification systems on the angular deviations of the neck and trunk and the muscle activities of the upper back and neck during preclinical cavity preparation. Methods: This was an experimental laboratory study, with the angular deviations from the neutral positions of the neck and trunk and the activities of the bilateral upper back (the descending and ascending trapezius) and neck (sternocleidomastoid) muscles as the dependent variables. The independent variables were the different magnification systems used (Simple, Galilean, and Keplerian loupes, with direct vision as the control) and prepared teeth (teeth 16, 26, 36, and 46). A dental mannequin phantom head with artificial resin teeth was used, and Class I cavity preparations for composite resin were performed on teeth 16, 26, 36, and 46 using a 1012 round diamond bur at low speed. To analyze the angular deviations, the postures adopted during the procedure were recorded using a tripod-mounted camera positioned to provide a lateral view of the operator. A trained researcher measured the angular deviations using the software entitled "Software for Postural Assessment"-SAPO (version 0.69). Bilateral muscle activity was assessed using surface electromyography. Descriptive statistical analysis was performed, and after verifying the assumptions of normality and homoscedasticity, two-way analysis of variance and the Tukey and Games-Howell post-hoc tests were used to compare the data (α=0.05). Results: The angular deviation from the neutral position of the neck was found to be significantly higher during cavity preparations performed with the naked eye and the Simple loupe, irrespective of the prepared tooth. With regard to tooth location, the angular deviation of the neck was significantly greater during cavity preparation on teeth 16 and 26, and the angular deviation of the trunk was significantly greater during cavity preparation on tooth 26, regardless of the magnification system used. There were significant differences in right sternocleidomastoid muscle activity between the Simple, Galilean, and Keplerian loupes, with activity being the lowest for the Galilean loupe (p = 0.008). There were no significant differences in left sternocleidomastoid muscle activity between the loupes, regardless of the prepared tooth (p = 0.077). The activities of the bilateral descending trapezius and the right ascending trapezius muscles were significantly lower when the Galilean loupe was used (p < 0.010). Conclusion: These results suggest that the Galilean loupe resulted in lower muscle activity in the neck and back regions and that the Galilean and Keplerian loupes resulted in less angular deviations of the neck and trunk during cavity preparation.

Differential leg and trunk operation during skipping without and with hurdles in bipedal Japanese macaque.

When locomoting bipedally at higher speeds, macaques preferred unilateral skipping (galloping). The same skipping pattern was maintained while hurdling across two low obstacles at the distance of a stride within our experimental track. The present study investigated leg and trunk joint rotations and leg joint moments, with the aim of clarifying the differential leg and trunk operation during skipping in bipedal macaques. Especially at the hip, the range of joint rotation and extension at lift off was larger in the leading than in the trailing leg. The flexing knee absorbed energy and the extending ankle generated work during each step. The trunk showed only minor deviations from symmetry. Hurdling amplified the differences and notably resulted in a quasi-elastic use of the leading knee and in an asymmetric operation of the trunk.

The effect of anthropometric measurements and muscle endurance of the trunk and lower extremities on anatomic body awareness in healthy individuals with different levels of physical activity.

BACKGROUND: The interaction between anthropometric measurements and muscular endurance and how these factors manifest in anatomical body awareness have not yet been fully investigated. It was aimed to examine the relationship between physical activity, body anthropometric measurements and endurance and anatomical body awareness in healthy individuals. MATERIALS AND METHODS: A total of 217 individuals aged 19-40 participated in the study. Participants were categorized into inactive (n = 65), minimally active (n = 80), and sufficiently active (n = 72) groups based on the international physical activity questionnaire (IPAQ). Anthropometric measurements including shoulder, abdomen, waist, and hip circumferences were taken. Participants' trunk muscle endurance and lower extremity endurance was assessed through various tests. Anatomic body awareness was evaluated using the Body Awareness Questionnaire (BAQ) with established validity. RESULTS: While no significant difference in shoulder circumference measurements was found between the inactive and minimally active groups (p > 0.05), the sufficiently active group showed significantly higher shoulder circumference measurements compared to the other groups (p < 0.05). Significant differences were observed among all endurance tests between the groups (p < 0.05). Participants' body endurance increased significantly with higher activity levels. Moreover, anatomic body awareness exhibited significant variation among the three groups (p < 0.05), with the sufficiently active group having the highest level of anatomic body awareness. Positive correlations were found between all endurance tests and anatomic body awareness (p < 0.05), as well as a positive correlation between physical activity levels and anatomic body awareness (p < 0.05). CONCLUSION: It is suggested that physical performance and endurance increase anatomical body awareness when applied with appropriate treatment methods, can be applied for a healthier life and can be an additional application in the clinical environment.

Comparing spinal loads in individuals with unilateral transtibial amputation with and without chronic low back pain: An EMG-informed approach.

Chronic low back pain (cLBP) is highly prevalent after lower limb amputation (LLA), likely due in part to biomechanical factors. Here, three-dimensional full-body kinematics and kinetics during level-ground walking, at a self-selected and three controlled speeds (1.0, 1.3, and 1.6 m/s), were collected from twenty-one persons with unilateral transtibial LLA, with (n = 9) and without cLBP (n = 12). Peak compressive, mediolateral, and anteroposterior L5-S1 spinal loads were estimated from a full-body, transtibial amputation-specific OpenSim model and compared between groups. Predicted lumbar joint torques from muscle activations were compared to inverse dynamics and predicted and measured electromyographic muscle activations were compared for model evaluation and verification. There were no group differences in compressive or anterior shear forces (p > 0.466). During intact stance, peak ipsilateral loads increased with speed to a greater extent in the cLBP group vs. no cLBP group (p=0.023), while during prosthetic stance, peak contralateral loads were larger in the no cLBP group (p=0.047) and increased to a greater extent with walking speed compared to the cLBP group (p=0.008). During intact stance, intact side external obliques had higher activations in the no cLBP group (p=0.039), and internal obliques had higher activations in the cLBP group at faster walking speeds compared to the no cLBP group. Predicted muscle activations demonstrated similar activation patterns to electromyographic-measured activations (r = 0.56-0.96), and error between inverse dynamics and simulated spinal moments was low (0.08 Nm RMS error). Persons with transtibial LLA and cLBP may adopt movement strategies during walking to reduce mediolateral shear forces at the L5-S1 joint, particularly as walking speed increases. However, future work is needed to understand the time course from pain onset to chronification and the cumulative influence of increased spinal loads over time.

Dancers Show More Accurate Trunk-Pelvic Joint Angle Reproduction While Wearing a Jacket Augmented With Elastic Bands.

Purpose: The Backalast® compression jacket is intended to improve posture and proprioception of the trunk and shoulder girdle for dancers and dance students during dance training by way of elastic bands in the rear of the garment (which include bands enclosing the inferior thorax). This study was intended to investigate whether there is evidence to support those objectives. Materials and Methods: Fifteen dance students participated (4 male, mean age 19.9 ± 1.4 years old). The dependent variables of trunk-pelvis angle and proximity of trunk axis to global vertical for each participant were measured using optical motion capture before and after the completion of a series of trunk movements. The Helen Hayes model, which we used to represent the trunk, includes the shoulder girdles as part of the trunk. We compared the effect of the type of garment (Backalast® or control compression shirt) worn upon the 2 dependent variables, within-subject with paired t-tests. The order of whether Backalast® or control compression shirt was worn first was alternated between participants. Results: The pre/posttest difference in trunk proprioception as represented by the construct of ability to reproduce trunk-pelvis angle wearing the Backalast® was 0.8° ± 0.8°, but for the control shirt, the difference was 1.8° ± 1.4°, P = .03. The difference between garments in vertical trunk alignment, measured after the series of trunk movements, was not significant. Conclusion: Our findings suggest that the Backalast® can help enhance trunk proprioception when compared to the control compression shirt, although it did not change the angle at which the participants' held their trunks while standing erect (proximity to global vertical).

Low Back Pain-Induced Dynamic Trunk Muscle Control Impairments Are Associated with Altered Spatial EMG-Torque Relationships.

PURPOSE: We quantified the relationship between high-density surface electromyographic (HDsEMG) oscillations (in both time and frequency domains) and torque steadiness during submaximal concentric/eccentric trunk extension/flexion contractions, in individuals with and without chronic low back pain (CLBP). METHODS: Comparisons were made between regional differences in HDsEMG amplitude and HDsEMG-torque cross-correlation and coherence of the thoracolumbar erector spinae (ES), rectus abdominis (RA), and external oblique (EO) muscles between the two groups. HDsEMG signals were recorded from the thoracolumbar ES with two 64-electrode grids and from the RA and EO muscles with a single 64-electrode grid placed over each muscle. Torque signals were recorded with an isokinetic dynamometer. Coherence (δ band (0-5 Hz)) and cross-correlation analyses were used to examine the relationship between HDsEMG and torque signals. For this purpose, we used principal component analysis to reduce data dimensionality and improve HDsEMG-based torque estimation. RESULTS: We found that people with CLBP had poorer control during both concentric and eccentric trunk flexion and extension. Specifically, during trunk extension, they exhibited a higher HDsEMG-torque coherence in more cranial regions of the thoracolumbar ES and a higher HDsEMG cross-correlation compared with asymptomatic controls. During trunk flexion movements, they demonstrated higher HDsEMG amplitude of the abdominal muscles, with the center of activation being more cranial and a higher contribution of this musculature to the resultant torque (particularly the EO muscle). CONCLUSIONS: Our findings underscore the importance of evaluating torque steadiness in individuals with CLBP. Future research should consider the value of torque steadiness training and HDsEMG-based biofeedback for modifying trunk muscle recruitment strategies and improving torque steadiness performance in individuals with CLBP.

The acute effect of passively assisted trunk stretching on central arterial stiffness and blood pressure in middle-aged to older adults.

PURPOSE: We examined the effects of acute trunk stretching on central arterial stiffness and central and peripheral blood pressure in middle-aged to older adults. METHODS: Twenty-eight middle-aged to older adults (14M/14F, 72 ± 7 years, 28.5 ± 5.3 kg/m2) completed this randomized, controlled, crossover design trial. We measured carotid-femoral pulse wave velocity (cf-PWV) and central and peripheral blood pressures (BP) before and after a single bout of passively assisted trunk stretching (i.e., five rounds of six 30-s stretches) and a time-matched seated control visit (i.e., 30-min). Changes (Δ; post - pre) in cf-PWV and central and peripheral BP were compared between visits and sexes using separate linear mixed-effects models controlling for baseline values. RESULTS: Compared with seated control, central (systolic: - 3 ± 7 mmHg; diastolic: - 2 ± 5 mmHg) and peripheral (systolic: - 2 ± 8 mmHg; diastolic: - 1 ± 4 mmHg) BP were reduced following acute trunk stretching (ps ≤ 0.001). Between-visit differences for ∆cf-PWV (stretch: 0.09 ± 0.61 m/s; control: 0.37 ± 0.68 m/s, p = 0.038) were abolished when controlling for change in mean arterial pressure (∆MAP) (p = 0.687). The main effects of sex were detected for changes in systolic BPs (ps ≤ 0.029); more males (n = 13) saw BP reductions than females (n = 7). CONCLUSION: These findings demonstrate the superiority of acute trunk stretching over passive sitting of equated duration for BP in middle-aged to older adults, with an appreciable effect in males compared to females.

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.