Eccentric Control Research Articles

The influence of smoothness and speed of stand-to-sit movement on joint kinematics, kinetics, and muscle activation patterns.

Stand-to-sit (StandTS) is an important daily activity widely used in rehabilitation settings to improve strength, postural stability, and mobility. Modifications in movement smoothness and speed significantly influence the kinematics, kinetics, and muscle activation patterns of the movement. Understanding the impact of StandTS speed and smoothness on movement control can provide valuable insights for designing effective and personalized rehabilitation training programs. How do the smoothness and speed of StandTS movement affect joint kinematics, kinetics, muscle activation patterns, and postural stability during StandTS? Twelve healthy younger adults participated in this study. There were two StandTS conditions. In the reference condition, participants stood in an upright position with their feet positioned shoulder-width apart on the force plate. Upon receiving a visual cue, participants performed StandTS at their preferred speed. In the smooth condition, participants were instructed to perform StandTS as smoothly as possible, aiming to minimize contact pressure on the seat. Lower leg kinetics, kinematics, and coordination patterns of muscle activation during StandTS were measured: (1) angular displacement of the trunk, knee, and hip flexion; (2) knee and hip extensor eccentric work; (3) muscle synergy pattern derived from electromyography (EMG) activity of the leg muscles; and (4) postural sway in the anterior-posterior (A-P), medio-lateral (M-L), and vertical directions. Compared to the reference condition, the smooth condition demonstrated greater eccentric knee extensor flexion and increased joint work in both the knee and hip joints. Analysis of specific muscle synergy from EMG activity revealed a significant increase in the relative contribution of hip joint muscles during the smooth condition. Additionally, a negative correlation was observed between knee extensor and vertical postural sway, as well as hip extensor work and M-L postural sway. Smooth StandTS facilitates enhanced knee eccentric control and increased joint work at both the hip and knee joints, along with increased involvement of hip joint muscles to effectively manage falling momentum during StandTS. Furthermore, the increased contributions of knee and hip joint work reduced postural sway in the vertical and M-L directions, respectively. These findings provide valuable insights for the development of targeted StandTS rehabilitation training.

Effects of Eccentric Versus Concentric Strengthening in Patients With Subacromial Pain Syndrome: A Randomized Controlled Trial.

Subacromial pain syndrome (SPS) is the most common cause of shoulder pain. Therapeutic exercise is the first-line treatment for SPS; however, the ideal exercise type remains unclear. Here, we compared the effects of eccentric and concentric strengthening in patients with SPS. Adding isolated eccentric strengthening to a multimodal physiotherapy program (MPP) would lead to greater improvements in outcomes compared with either MPP alone or adding isolated concentric strengthening to the MPP. Randomized controlled trial. Level 2. A total of 45 patients were randomized to eccentric strengthening (ESG), concentric strengthening (CSG), and control (CG) groups; all groups received the MPP. The strengthening groups also performed group-specific strengthening. Shoulder pain, abduction and external rotation (ER) strength, joint position sense (JPS), the Constant-Murley Score (CMS), and the Disabilities of the Arm, Shoulder and Hand score were collected at baseline, after 12 weeks of treatment, and at week 24. For CMS, ESG exhibited a greater, but not clinically meaningful, improvement than CSG and CG (P < 0.05). Eccentric abduction strength increased in ESG compared with CG. From baseline to follow-up, abduction strength increased in ESG compared with CSG and CG. Eccentric abduction strength increased in CSG compared with CG. JPS at abduction improved in the ESG compared with CG. Other between-group comparisons were not significant (P > 0.05). In SPS, eccentric strengthening provided added benefits, improving shoulder abduction strength and JPS at abduction, and was superior to concentric strengthening for improving shoulder abduction strength. Neither strengthening approach had an additional effect on shoulder function, pain, ER strength, or rotational JPS. Clinicians could implement eccentric strengthening as a motor control retraining for strength and proprioception gain rather than for pain relief and reducing disability.

Age-related differences in lower limb muscle activation patterns and balance control strategies while walking over a compliant surface

Substantial evidence demonstrates that falls in older adults are leading causes of fatal and non-fatal injuries and lead to negative impacts on the quality of life in the aging population. Most falls in older fallers result from unrecoverable limb collapse during falling momentum control in the single limb support (SLS) phase. To understand why older adults are more likely to fall than younger adults, we investigated age-related differences in knee extensor eccentric control, lower limb muscle activation patterns, and their relation to balance control. Ten older and ten younger healthy adults were compared during balance control while walking on a compliant surface. There was a positive correlation between knee extensor eccentric work in the perturbed leg and the swinging leg’s speed and margin of stability. In comparison to younger adults, older adults demonstrated (1) less eccentric work, reduced eccentric electromyography burst duration in the perturbed leg, (2) higher postural sway during SLS, and (3) impaired swinging leg balance control. The group-specific muscle synergy showed that older adults had a prominent ankle muscle activation, while younger adults exhibited a more prominent hip muscle activation. These findings provide insight into targeted balance rehabilitation directions to improve postural stability and reduce falls in older adults.

The Accuracy of Ankle Eccentric Torque Control Explains Dynamic Postural Control During the Y-Balance Test.

The Y-Balance Test (YBT), especially the posteromedial (PM) reach direction (PM-YBT), is able to identify dynamic postural control deficits in those who have ankle instability. However, there still exists a need to understand how sensorimotor function at the ankle explains the performance during the PM-YBT. The purpose of this study was to determine whether the ability to accurately control eccentric ankle torque explained PM-YBT performance. It was hypothesized that eccentric dorsiflexion/plantarflexion torque control would be positively related to the maximum reach distance (MRD) of PM-YBT. Cross-sectional study. Twelve healthy subjects performed the PM-YBT, maximum voluntary isometric contractions (MVIC) for both dorsiflexion and plantarflexion muscle strength, and then the torque control testing of the ankle. The torque control testing provided a target torque level on a screen in front of the subject and passive rotations of the ankle joint in the sagittal plane at 10 deg/sec between plantarflexion to dorsiflexion. Subjects were then instructed to eccentrically contract the dorsiflexors and plantar flexors to generate torque while the ankle joint rotated. The accuracy of torque control during eccentric dorsiflexion and plantarflexion by calculating absolute errors, the area between the target torque and the produced torque were evaluated. Tibialis anterior and soleus muscle activities were simultaneously recorded during testing. A step-wise linear regression model was used to determine the best model predicted the MRD of the PM-YBT (PM-MRD). A step-wise linear regression developed a model explaining only eccentric dorsiflexion torque control predicted higher PM-MRD score (R2 = 44%, F1,10 = 7.94, β = -0.67, p = 0.02). The accuracy of torque control during eccentric dorsiflexion predicts better performance in the PM-YBT. 3b.

Seismic performance analysis of adjacent eccentric structures based on PSO algorithm

Adjacent structures connected by dampers can effectively prevent collisions and attenuate the response of these structures. An early simplified model was investigated using a two-dimensional model. However, this model disregarded the effect of torsional response due to eccentricity. The eccentric arrangement of dampers owing to the non-parallel centroid between adjacent structures has not been considered in existing research. Here, the vibration equation of adjacent structures connected to a Kelvin damper was derived to study the torsional response under earthquake excitation. Furthermore, a PSO (Particle Swarm Optimization) algorithm was adopted to conduct a parametric study. Additionally, the damping effects of adjacent structures were compared using various damper layout schemes. The results show that the structural displacement was reduced by 50% by connecting dampers between adjacent structures. Placing dampers in the middle of a structure has a greater damping control effect than placing them on the side columns. However, the optimal damper layout must be chosen based on the diverse eccentric combinations and control goals of the adjacent structures. A damper can be arranged eccentrically to increase its damping control effect on an adjacent structures by 50% to 75%. The weakening of the edge effect on the damping effect should be considered when choosing the control objective for damper optimization. This weakening impact can reduce the damping effects by 50% and lead to greater deformation of the side column. The response of adjacent structures can be controlled macroscopically by utilizing the translation–torsional energy ratio as the control goal. However, a high fundamental frequency ratio of adjacent structures should be avoided.

Contribution of Lower Limb Eccentric Control to Balance Recovery From Surface Drop Perturbations

<h3>Research Objectives</h3> To investigate age-related differences in eccentric neuromuscular control of the knee and its relationship to postural stability during balance recovery following unexpected surface drop perturbations. <h3>Design</h3> Cross sectional, comparative study. <h3>Setting</h3> General community. <h3>Participants</h3> Healthy, community dwelling, and ambulatory older (n=10, age=75.3±5.6) and younger (n=10, age=25.7±2.0) adults. <h3>Interventions</h3> N/A. <h3>Main Outcome Measures</h3> 1) Eccentric knee extension work (J/kg); 2) EMG burst duration (s) in the perturbed leg during the single limb support phase of compensatory stepping; 3) postural sway (standard deviation of center of mass acceleration, m/s2) in the anterior-posterior (A-P), medio-lateral (M-L), vertical directions; 4) margin of stability (MoS) of first compensatory step touchdown after perturbations. <h3>Results</h3> Following an 8 cm surface drop perturbation at gait initiation, older adults (OA) compared to younger adults (YA), demonstrated reduced eccentric knee extensor work (OA: 0.013±0.005 J/kg, YA: 0.020±0.007 J/kg, p=0.034), rectus femoris EMG burst duration (OA: 0.35±0.07s, YA: 0.47±0.08s, p< 0.01), MoS (OA: 68.41±14.30%, YA: 82.88±13.24%, p=0.04), and increased postural sway in all directions (A-P: OA: 2.29±1.38m/s2, YA: 1.03±0.54 m/s2, p=0.02, M-L: OA: 1.42±0.71 m/s2,YA: 0.72±0.41m/s2, p=0.02, Vertical: OA: 4.17±1.01m/s2, YA: 1.74±0.86m/s2, p< 0.01). There was a negative correlation between eccentric work and postural sway in the M-L direction (r = -0.54, p=0.012) and a positive correlation between eccentric work and MoS (r = +0.55, p=0.009). <h3>Conclusions</h3> This study is the first to demonstrate that age-related differences in eccentric control of the perturbed leg are associated with maintaining postural stability and improving compensatory stepping balance response following unexpected surface drop perturbations. Older adults demonstrated deficits in eccentric knee extensor control and this contributed to greater postural sway and unstable compensatory stepping during balance recovery. This finding provides insight into mechanisms of fall recovery and directions for lower limb strengthening exercises for aging populations. Future investigations of these mechanisms in aging populations with a disability due to neurological or musculoskeletal impairments such as Parkinson's disease, stroke, and osteoarthritis are warranted. <h3>Author(s) Disclosures</h3> The contents of this abstract were developed under a grant from NIDILRR (90AR5028).

Age-related differences in stepping stability following a sudden gait perturbation are associated with lower limb eccentric control of the perturbed limb.

Falls are a leading cause of severe injuries and a major threat to quality of life in older adults. Elderly fallers demonstrate insufficient eccentric quadriceps control during the weight acceptance phase of initial single limb stance. However, the functional role of eccentric control of the perturbed (leading) leg during walking balance recovery and its age-related differences have not yet been studied; thus we investigated age-related differences in eccentric control at the knee of the perturbed leg and its influence on the postural sway and stability of the trailing leg during balance recovery following unexpected surface drop perturbations. Ten younger and ten older healthy adults were compared during balance recovery following an 8cm unexpected surface drop perturbation at gait initiation. Outcomes related to perturbed leg included 1) eccentric knee extensor work; 2) electromyography (EMG) peak amplitude, peak latency, and eccentric EMG burst duration of the rectus femoris (RF); and 3) knee flexion angle during the single limb support. Outcomes related to stability of the trailing leg included 4) margin of stability (MoS) at first compensatory step touchdown after the perturbation. 5) Postural sway (standard deviation of center of mass acceleration) was measured in the anterior-posterior (A-P), medio-lateral (M-L), vertical directions during the single limb support. Compared to younger adults, older adults demonstrated lower eccentric knee extensor work (p=0.034), shorter RF EMG burst duration (p<0.01), delayed RF EMG peak latency (p=0.01), smaller knee flexion angle (p=0.01) and MoS (p=0.04), and higher postural sway (M-L (p=0.02), vertical (p<0.01)). There was a positive correlation between eccentric work and MoS (p=0.03) and a negative correlation between M-L postural sway and 1) RF eccentric EMG burst duration (p=0.04), and 2) eccentric work (p=0.01). Older adults demonstrated deficits in eccentric knee extensor control in the perturbed leg during single limb support, which contributed to reduced stability of the trailing leg compensatory step and greater postural sway during balance recovery. This finding provides insight into mechanisms of fall recovery from an unexpected unilateral postural perturbation and directions for lower limb strengthening exercises for aging populations.

Functional progressive resistance exercise versus eccentric muscle control in children with hemiplegia: a randomized controlled trial

BackgroundHistorically, strength exercise in children with CP is not recommended, because it may develop spasticity, which results in difficulty with walking. But, recently increasing studies and systemic reviews have reported that strength exercise can promote muscle strength in children with CP with no negative impact on spasticity. The study is aiming to compare the effect of functional resistance exercise and functional eccentric training on dynamic balance and functional ability in children with hemiplegia. For this purpose, forty participating children diagnosed with spastic hemiplegia were included and their ages ranged from 6 to 13 years. They were randomly allocated into two groups: functional resistance exercise (group I) or eccentric muscle control exercise (group II). The training was conducted three times a week for 6 weeks for both groups. Each group received one of the interventions in addition to designed physical therapy programs. Functional ability and dynamic balance were measured before and after 6 weeks of the intervention by gross motor function measure and functional reach test.ResultsComparison between the two groups before treatment revealed no significant difference in all values of functional ability and dynamic balance. But comparison after treatment in values showed significant improvement in both groups with greater improvements in favor of group I (p < 0.01).ConclusionAdding both functional resistance exercise and eccentric muscle control exercise is beneficial for improving functional ability and dynamic balance with more recommendation for adding functional resistance exercise that showed more significant improvement than eccentric muscle control in children with hemiplegia.

Susceptibility to movement-evoked pain following resistance exercise.

ObjectiveTo investigate the: (1) role of basic muscle pain sensitivity and psychological factors in the prediction of movement-evoked pain (MEP) following delayed onset muscle soreness (DOMS), and (2) association of MEP with changes in systemic muscle pain sensitivity following DOMS induction.MethodsFifty-one participants were assigned to either eccentric resistance exercise or control groups. They completed questionnaires evaluating psychological distress and underwent muscle pain sensitivity evaluation by the pressure pain threshold (PPT) test at the exercised and remote muscles, before and 24 hours following the intervention. MEP intensity was determined in response to lifting a 3kg canister using a visual analogue scale (VAS).ResultsThe exercise group demonstrated MEP intensity of 5/10 on VAS and reduced PPTs at the main exercised muscle (p<0.001). A regression tree analyses revealed that the level of anxiety trait predicted a higher MEP intensity. A secondary analysis showed that 53% participants who were DOMS responders (MEP > mild intensity; ≥ 3/10 VAS) exhibited decreased PPTs in the exercised (p<0.001) and remote (p = 0.027) muscles following eccentric exercise. Characterization of DOMS responders revealed that, at baseline, they had lower PPTs in the exercised (p = 0.004) and remote (p = 0.001) muscles and reported higher psychological distress i.e., anxiety trait and depression symptoms (p<0.05), compared to non-responders. A regression analysis revealed that lower PPT or high levels of anxiety trait increased the probability to become a responder (p = 0.001).ConclusionsSusceptibility to MEP following DOMS is determined by muscle pain hypersensitivity and high levels of anxiety trait. MEP at the early stage of DOMS is linked with an increase in systemic muscle pain sensitivity suggestive of central mechanisms. This knowledge is valuable in translating science into clinical musculoskeletal pain management.

Eccentric Exercise Causes Specific Adjustment in Pyruvate Oxidation by Mitochondria.

The impact of eccentric exercise on mitochondrial function has only been poorly investigated and remains unclear. This study aimed to identify the changes in skeletal muscle mitochondrial respiration, specifically triggered by a single bout of eccentric treadmill exercise. Male adult mice were randomly divided into eccentric (ECC; downhill running), concentric (CON; uphill running), and unexercised control groups ( n = 5/group). Running groups performed 18 bouts of 5 min at 20 cm·s -1 on an inclined treadmill (±15° to 20°). Mice were sacrificed 48 h after exercise for blood and quadriceps muscles collection. Deep proximal (red) and superficial distal (white) muscle portions were used for high-resolution respirometric measurements. Plasma creatine kinase activity was significantly higher in the ECC compared with CON group, reflecting exercise-induced muscle damage ( P < 0.01). The ECC exercise induced a significant decrease in oxidative phosphorylation capacity in both quadriceps femoris parts ( P = 0.032 in proximal portion, P = 0.010 in distal portion) in comparison with the CON group. This observation was only made for the nicotinamide adenine dinucleotide (NADH) pathway using pyruvate + malate as substrates. When expressed as a flux control ratio, indicating a change related to mitochondrial quality rather than quantity, this change seemed more prominent in distal compared with proximal portion of quadriceps muscle. No significant difference between groups was found for the NADH pathway with glutamate or glutamate + malate as substrates, for the succinate pathway or for fatty acid oxidation. Our data suggest that ECC exercise specifically affects pyruvate mitochondrial transport and/or oxidation 48 h after exercise, and this alteration mainly concerns the distal white muscle portion. This study provides new perspectives to improve our understanding of the mitochondrial adaptation associated with ECC exercise.

The Eccentric Phase in Unilateral Resistance Training Enhances and Preserves the Contralateral Knee Extensors Strength Gains After Detraining in Women: A Randomized Controlled Trial.

The current randomized controlled study investigated whether or not the inclusion of the eccentric phase in resistance training favors the contralateral strength gains after different unilateral protocols, and whether such gains are retained after detraining. Sixty healthy women were randomly assigned to a unilateral concentric-only (CONC), eccentric-only (ECC), concentric–eccentric (TRAD) volume-equated knee extension training or control group (CON). The participants trained 2 days/week for 8 weeks and then did not train for further 8 weeks. Knee extensors isokinetic concentric, eccentric, and isometric peak torque and vastus lateralis muscle thickness were assessed in the contralateral limb at baseline, post-training, and post-detraining. At post-training, concentric peak torque increased in CONC [+9.2%, 95%CI (+6.2/+12.3), p < 0.001, ES: 0.70, 95%CI (0.01/1.39)], ECC [+11.0% (+7.7/+14.2), p < 0.001: ES: 0.66(0.09/1.23)] and TRAD [+8.5%(+5.7/+11.6), p < 0.001, ES: 0.50(0.02/0.98)]. Eccentric peak torque increased in ECC in ECC [+15.0%(+11.4/+20.7), p < 0.001, ES: 0.91(0.14/1.63)] and TRAD [+5.5%(+0.3/10.7), p = 0.013, ES: 0.50(0.05/0.95)]. Isometric peak torque increased in ECC [+11.3(+5.8/16.8), p < 0.001, ES: 0.52(0.10/0.94)] and TRAD [+8.6%(+3.4/+13.7), p < 0.001, ES: 0.55(0.14/0.96)]. No change in eccentric and isometric peak torque occurred in CONC (p > 0.05). Muscle thickness did not change in any group (p > 0.05). At post-detraining, all groups preserved the contralateral strength gains observed at post-training (p < 0.05). The findings showed that ECC and TRAD increased contralateral knee extensors strength in concentric, eccentric, and isometric modality, while CONC only increased concentric strength. The eccentric phase appears to amplify the cross-education effect, permitting a transfer in strength gaining toward multiple testing modalities. Both eccentric-based and traditional eccentric–concentric resistance protocols are recommended to increase the contralateral retention in strength gains after a detraining period.

Power Efficient Active Vibration Control Via Twin Rotor Damper in the Presence of Gravity

Abstract The twin rotor damper (TRD) is a device which primarily utilizes centrifugal forces for active vibration control. In its basic form, the TRD consists of two eccentric control masses rotating about two parallel axes. In a preferred mode of operation, the continuous rotation mode (CRM), the control masses rotate in opposite directions with a constant and equal angular velocity. This rotational motion results in a harmonic control force. In previous research, it has been shown that, in the CRM, the TRD can effectively damp vibrations while requiring little to no power from its actuators. However, this holds only for lateral vibrations, vibration perpendicular to gravitational forces, ergo gravity has no influence on the motion of the control masses. In this paper, the influence of gravity on the CRM is investigated analytically for the first time. It is shown that the TRD requires substantially greater power in the CRM to periodically lift the control masses against gravity. Subsequently, the CRM is augmented with an auxiliary function in the form of a Fourier series. This function is optimized such that the increase in power due to gravity is minimized while maintaining the damping performance of the TRD. The effects of augmenting the CRM are investigated, and a control algorithm is developed for the operation in the augmented CRM. In a numerical design example, it is shown that, with the augmented CRM, the power efficiency of the TRD can be regained at the cost of moderately reducing its damping performance.

Intrinsic foot muscle size and quality in a single leg weight bearing position across foot posture types in individuals with Patellofemoral Pain compared to healthy

ObjectiveTo identify if any differences exist in IFM size and quality in single leg weight bearing position between healthy and PFP participants based on foot posture. DesignCross-sectional, matched case-comparison study SettingUniversity Laboratory Setting Participants35 PFP (age:20.46 ± 3.79yrs, mass:73.28 ± 26.58 kg, height:170.80 ± 11.91 cm) and 35 healthy (age:20.40 ± 3.16yrs, mass:64.76 ± 11.52 kg, height:169.55 ± 9.10 cm) participants MethodsAfter measuring Foot Posture Index (FPI), ultrasound images (USI) of Abductor Hallucis (AH), Flexor Digitorum Brevis (FDB) and Quadratus Plantae (QP) were taken in a single limb weight bearing position. Cross-sectional area (CSA) and echogenicity were measured on the USI. ResultsFPI was not different between groups (PFP:2.34 ± 3.76, Healthy:2.34 ± 3.10, 9 pronated and 26 non-pronated in both groups). AH CSA was smaller in PFP than healthy group (PFP:0.030 ± 0.01 cm2/kg, Healthy:0.042 ± 0.01 cm2/kg, P < 0.001) with a large effect (d = −1.20(-1.71, −0.69). There were no other significant group main effects or group-by-FP interactions in AH/FDB/QP CSA or echogenicity. ConclusionAH CSA was smaller in PFP than healthy controls, but no difference in CSA or echogenicity of FDB/QP exist, as well as no difference in foot posture between groups. While single limb weight bearing, the PFP group presented with a smaller IFM which provides eccentric control of medial longitudinal arch, which may have implications up the chain during weight bearing functional tasks.

Comparison of Muscle Energy Technique versus Eccentric Training on Hamstrings Extensibility among Adolescent Girls

Background: Hamstrings extensibility is affected as a result of lack of physical activity causing alimitation of extension motion of the knee joint, increases posterior pelvic tilting and reducing lumbarlordosis that can result in nonspecific low back pain.Aim: To compare the effects of muscle energy technique versus eccentric training on hamstringsextensibility among adolescent girls.Methods: Based on Inclusion and Exclusion criteria, 60 adolescent girls of age group 15-24 years wereassessed &amp; selected using Active Knee Extension Test for a lag in extension of around 20 degreesduring performance of the test. The subjects were divided into three groups of 20 each. Group A(Control Group) was given Conventional treatment as Hot Pack as warm up over the Hamstringsmuscle for both the lower limbs &amp; Static Stretching. Thereafter, Group B (Experimental Group 1) wasgiven Muscle Energy Technique &amp; Conventional treatment and Group C (Experimental Group 2) wasgiven Eccentric Training &amp; Conventional treatment for total 6 sessions as 3 sessions a week for 2 weeksrespectively.Results: Data was meaningfully assorted through calculation of Mean and Standard Deviation.Thereafter, T test was applied for comparison between the MET group and Eccentric Training groupand Control Group. The level of significance was fixed at p&lt;0.05. There was significant differencewithin and between the MET group and Eccentric Training group for both the limbs.Conclusion: The study concluded that MET was better than Eccentric Training in improving Hamstringsextensibility among Adolescent Girls.

Effect of eccentric and concentric squat exercise on quadriceps thickness and lower extremity performance in healthy young males

Background: In clinical practice, resistance training, which includes concentric and eccentric dynamic muscle movements, is widely used by physiotherapists to strengthen the quadriceps muscle. However, although eccentric training is assumed to induce greater hypertrophy compared to concentric contractions, there are also studies reporting that similar increases in muscle thickness can be seen in both eccentric and concentric training.Objective: This study aims to assess the effect of the eccentric and concentric squat exercise on quadriceps thickness, and lower extremity performance during jumping and walking in healthy young sedentary males. Methods: Participants were randomly divided into three groups: concentric exercise group (CE; n = 19), eccentric exercise group (EE; n = 13) and control group (CG; n = 16). Both exercises were performed seven days a week, for eight weeks with a gradual strength increase. The CG was not given any exercise. Ultrasound assessment of quadriceps muscle thickness, performance in Six-Minute Walk Test and vertical jump was measured. Results: Thickness of dominant side of rectus femoris (p = .008) and vastus lateralis (p = .021) differed significantly among the three groups; post hoc analysis revealed the thickness of rectus femoris in CG was significantly lower than in the CE (p = .046) and EE (p = .006) and the thickness of vastus lateralis in the EE was significantly higher than in the CG (p = .018). Six-Minute Walk Test score in the EE was significantly higher than in the CG (p = .025) and the vertical jump score in the CG significantly lower than in the EE (p = .002) and CE (p &lt; .001). Conclusions: Eccentric and concentric training both benefits muscle hypertrophy and lower extremity functional performance. However, eccentric training also appears to offer a small advantage over concentric training.

Noise Reduction Design of Steam Control Valve

The internal steam fluid pressure pulse force is the excitation source of control valve. Based on the Lighthill equation and the orifice injection shunt noise reduction theory, the flow noise and air noise calculations of throttling devices are carried out for the eccentric rotary control valve and the cage sleeve control valve, and the design improvements are presented for noise control of the valves. When there is no noise reduction internals, the air noise caused by the steam control valve with a pressure of 4.5MPa in front of the valve is greater than 95dB. The preset orifice plate reduces the pressure in the control valve to 50% of that before the valve, then the small hole Shunt method for noise reduction can be employed. When the two-stage orifice plate is installed and the number of second-stage holes is greater than 100, the air noise of the eccentric rotary steam control valve is lower than 80dB, and the first-stage orifice plate is installed. The air noise of the bored sleeve type steam control valve with preset orifice plate is also lower than 80dB, but it is easier to meet the low noise design requirements of the steam control valve than the improving method used in above sleeve type steam control valve.

Active Vibration Control of a Multi-Degree-of-Freedom System via Twin Rotor Damper

Abstract The twin rotor damper (TRD), an active mass damping device, is used for the vibration control of a multi-degree-of-freedom (MDOF) system of oscillators. A single TRD unit consists of two eccentric control masses rotating about two parallel axes. In its principle mode of operation, the continuous rotation mode (CRM), the control masses rotate with a constant angular velocity in opposite directions; producing a monofrequent harmonic control force in an energy and power efficient manner. Extensive research has shown the effectiveness of the TRD in the CRM for systems with a single dominate mode of vibration. In this paper, the application of a single and multiple TRD units operating in the CRM is investigated for the control of a MDOF system of oscillators. The influence of the monofrequent control force produced by the TRD on the MDOF system of oscillators is investigated analytically. Subsequently, the analysis is inverted and the influence of the MDOF system of oscillators on the TRD is studied, in particular its power efficiency and damping performance. Finally, the power efficiency and damping performance of the TRD for the control of a system with two modes of vibration is analytically compared with that of a conventional active mass damping (CAMD) device. It is shown that in most cases, the TRD achieves greater damping performance in a more power efficient manner than a conventional active mass damper of similar size and mass.

Trunk kinematics and muscle activation patterns during stand-to-sit movement and the relationship with postural stability in aging

BackgroundStand-to-sit (StandTS) movement is an important functional activity that can be challenging for older adults due to age-related changes in neuromotor control. Although trunk flexion, eccentric contraction of the rectus femoris (RF), and coordination of RF and biceps femoris (BF) muscles are important to the StandTS task, the effects of aging on these and related outcomes are not well studied. Research questionWhat are the age-related differences in trunk flexion, lower extremity muscle activation patterns, and postural stability during a StandTS task and what is the relationship between these variables? MethodsTen younger and ten older healthy adults performed three StandTS trials at self-selected speeds. Outcomes included peak amplitude, peak timing, burst duration, and onset latency of electromyography (EMG) activity of the RF and BF muscles, trunk flexion angle and angular velocity, whole body center of mass (CoM) displacement, center of pressure (CoP) velocity, and ground reaction force (GRF). ResultsThere were no age-related differences in weight-bearing symmetry, StandTS and trunk flexion angular velocity, or BF activity. In both groups, EMG peak timing of RF was preceded by BF. Compared to younger adults, older adults demonstrated shorter RF EMG burst duration, reduced trunk flexion, and reduced stability as indicated by the longer duration in which CoM was maintained beyond the posterior limit of base of support (BoS), greater mean anterior-posterior CoP velocity and larger standard deviation of CoM vertical acceleration during StandTS with smaller vertical GRF immediately prior to StandTS termination. Trunk flexion angle and RF EMG burst duration correlated with stability as measured by the duration in which the CoM stayed within the BoS. SignificanceDecreased trunk flexion and impaired eccentric control of the RF are associated with StandTS instability in aging and suggest the importance of including StandTS training as a part of a comprehensive balance intervention.

Effect of Different Types of Lower-Limb Exercise on Blood Pressure in Hypertensive People: A Randomized, Double-blind Controlled Clinical Trial

Objectives: The current study aimed at determining the immediate and long-lasting effects of eccentric and concentric exercises on hypertension in individuals with high blood pressure. Methods: A total of 45 hypertensive volunteers were randomly assigned to three intervention groups as eccentric exercise (n = 15), concentric exercise (n = 15), and control (n = 15) groups. All the volunteers underwent exercise interventions for four weeks, three sessions per week (12 sessions in total) as treadmill walking with +10% gradient (concentric group), -10% gradient (eccentric group), or neutral gradient. Before the intervention, immediately after the first session of the intervention, after the end of the intervention, and 48 hours after the end of the intervention, systolic and diastolic blood pressure, heart rate, and maximum oxygen consumption were measured and compared between the groups. Results: The positive gradient group had higher diastolic blood pressure 48 h after the intervention than the negative and neutral gradient groups (P &lt; 0.05). There was no significant difference in the other study variables between eccentric and concentric exercise groups (P &gt; 0.05). Statistical analysis showed that eccentric exercises immediately reduced systolic and diastolic blood pressure (P &lt; 0.05). Eccentric and constrictive exercises reduced systolic and diastolic blood pressure for the long term (P &lt; 0.05). Exonerative and constrictive exercises improved the heart rate, maximum oxygen consumption, and systolic blood and diastolic blood pressure in the short and long term (P &lt; 0.05). Conclusions: Eccentric and concentric exercises with immediate and long-lasting effects improved systolic and diastolic blood pressure, as well as heart rate and maximum oxygen consumption. No significant difference was found between the two types of exercises in terms of the variables studied.

Fatigue-Induced Hip-Abductor Weakness and Changes in Biomechanical Risk Factors for Running-Related Injuries.

Despite overlap between hip-abductor (HABD) weakness and fatigue-induced changes in running, the interaction of these theorized contributors to running injuries has been underevaluated. To assess the effects of a fatiguing run on HABD torque and evaluate the correlation between HABD torque and previously identified running-related injury pathomechanics while participants were rested or fatigued. Crossover study. Laboratory. A total of 38 healthy, physically active males (age = 21.61 ± 4.02 years, height = 1.78 ± 0.08 m, body mass = 76.00 ± 12.39 kg). Data collection consisted of rested-state collection, a fatiguing treadmill-run protocol, and fatigued-state collection. For the HABD measures, side-lying handheld-dynamometer isometric tests were performed and converted to torque using femur length. For the gait analysis, kinematic (240 Hz) and kinetic (960 Hz) running (4.0 m/s) data were collected for 3 trials. The fatigue protocol involved a graded exercise test and 80% o2max run to exhaustion. Immediately after the run, fatigued-state measures were obtained. Variables of interest were HABD torque and peak angles, velocities, and moments for hip and knee adduction and internal rotation. Differences between conditions were compared using paired t tests. Pearson correlation coefficients were calculated to evaluate relationships between HABD torque and biomechanical variables. Fatigue decreased HABD torque and increased hip-adduction angle, knee-adduction velocity, and hip and knee internal-rotation velocities and moments (all P values < .05). In the rested state, HABD torque was correlated with hip-adduction velocity (r = -0.322, P = .049). In the fatigued state, HABD torque was correlated with hip-adduction velocity (r = -0.393, P = .015), hip internal-rotation velocity (r = -0.410, P = .01), and knee-adduction angle (r = 0.385, P = .017) and velocity (r = -0.378, P = .019). Changes in joint velocities due to fatigue and correlations between HABD torque and hip- and knee-joint velocities highlight the need to consider not only the quantity of HABD strength but also the rate of eccentric control of HABDs.