Joint Stiffness Characteristics Research Articles

Effect of moxibustion on knee joint stiffness characteristics in recreational athletes pre- and post-fatigue

ObjectiveJoint stiffness results from the coupling of the nervous system and joint mechanics, and thus stiffness is a comprehensive representation of joint stability. It has been reported that moxibustion can alleviate general weakness and fatigue symptoms and subsequently may influence joint stiffness. This study investigated whether moxibustion could enhance knee joint stiffness in recreational athletes pre- and post-fatigue. MethodsEighteen participants were randomized into intervention (5 males: 20.6 ± 1.5 yr; 4 females: 20.8 ± 1.5 yr) and control groups (5 males: 19.4 ± 0.9 yr; 4 females: 20.5 ± 0.6 yr). The intervention group received indirect moxibustion applied to acupoints ST36 (bilateral) and CV4 for 30 min every other day for 4 consecutive weeks. The control group maintained regular exercise without moxibustion. Peak torque (PT) of right knee extensor, relaxed and contracted muscle stiffness (MS) of vastus lateralis, and knee extensor musculoarticular stiffness (MAS) was assessed with an isokinetic dynamometer (IsoMed 2000), myometer, and free oscillation technique, respectively. Measurements were taken at three time points: pre-intervention, post-intervention/pre-fatigue, and post-fatigue. ResultsMAS (P = 0.006) and PT (P = 0.007) in the intervention group increased more from pre-to post-intervention compared with the control group. Post-fatigue MAS (P = 0.016) and PT (P = 0.031) increased more in the intervention group than in the control group. ConclusionMoxibustion enhanced PT and knee MAS, suggesting that this intervention could be used in injury prevention and benefit fatigue resistance in young recreational athletes.

Effect Of Moxibustion On Knee Joint Stiffness Characteristics In Recreational Athletes Pre And Post Fatigue

Stiffness is the coupling of nervous system and joint mechanics, and thus the comprehensive representative of joint stability. It has been reported that moxibustion can improve weakness and alleviate fatigue symptoms. PURPOSE: To investigate whether moxibustion could enhance knee joint stiffness characteristics in recreational athletes pre and post fatigue. METHODS: Twenty-four participants were partially randomized into intervention (9 males: 20.2 ± 1.5 yr; 6 females: 20.7 ± 1.2 yr) and control group (5 males: 19.4 ± 0.9 yr; 4 females: 20.5 ± 0.6 yr). Intervention group: Acupoints ST36 (bilateral) and CV4 for indirect moxibustion 30 min every other day for 4 consecutive weeks; control group: no moxibustion intervention. Peak torque (PT) of right knee extensors, relaxed and contracted muscle stiffness (MS) of vastus lateralis, knee extensors musculoarticular stiffness (MAS) were assessed by isokinetic dynamometer IsoMed 2000, Myometer and free oscillation technique respectively, at three time points: pre-intervention (time-point 1), post-intervention (time-point 2), and after a treadmill fatigue protocol (time-point 3). RESULTS: Two-way repeated measures ANOVA found a significant interaction between time and group in MAS (p = 0.001) and normalized PT (p = 0.004). Post-hoc tests with the Bonferroni-adjusted α were conducted and identified that MAS in intervention group (time-point 1: 521.8±201.3 N/m, time-point 2: 637.7±181.2 N/m) increased more from pre to post intervention when compared to the control group (time-point 1: 615.4±196.6 N/m, time-point 2: 597.1±190.4 N/m) (p = 0.022). There was a tendency that after fatigue MAS increased more in intervention group (time-point 2: 637.7±181.2 N/m, time-point 3: 712.1±156.9 N/m) than in control group (time-point 2: 597.1±190.4 N/m, time-point 3: 629.8±172.7 N/m) (p = 0.202); and the tendency that normalized PT (PT/body mass) increased in intervention group (time-point 2: 1.49 ± 0.20 Nm/kg, time-point 3: 1.53 ± 0.17 Nm/kg) whilst it decreased in control group (time-point 2: 1.41 ± 0.21 Nm/kg, time-point 3: 1.34 ± 0.21 Nm/kg) (p = 0.033). CONCLUSION: Moxibustion enhanced the knee MAS, may benefit the ability of fatigue resistance in young recreational athletes, and thus could be utilized in injury prevention. Supported by Jiangsu Education Department

Stiffness Simulation of Joints of Large Manipulators based on Cam Torsion Spring Mechanisms

There is elasticity in the joint of large manipulators, and the transfer torque is related to the relative rotation angle between input and output terminal. In order to simulate this stiffness characteristic in the test experiment, a cam torsion spring mechanism and its design method are proposed in this paper. The mechanism can simulate arbitrary angle-torque curve by directional design. After the necessary analysis and design, the actual characteristics of the mechanism are tested by experiments, which proves that the mechanism can simulate the stiffness characteristics of joints of large manipulator arm very well.

Stiffness characteristics of joints and influence on the stability of single-layer latticed domes

In this paper, the theoretical and practical formulas of initial stiffness of welded hollow spherical joints were presented, and the elastic and elastoplastic critical displacements and rotations were obtained respectively. A mechanical model considering the stiffness characteristics of joints was proposed, the criterion of eccentric states and bearing stages was established to analyse the influence on the stability of single-layer latticed domes. Results indicate that the practical initial stiffness formulas proposed fit well with the theoretical solutions. The mechanical model can accurately simulate the stiffness characteristics and bearing stages of joints in the failure process of structure. Compared with the experimental results, the average error of mechanical model for the initial slope of load-rotation curve is 8%, and the average error for the ultimate bearing capacity is 7%. The stiffness degeneration of the joints in the plastic stage may cause a significant reduction in stability capacity of the structure. The stability reduction factors of K6 and Geodesic domes are between 0.7 and 1.0, and the stability reduction factors of K8-lamella domes are between 0.65 and 1.0.

Acute exposure to foot orthoses affects joint stiffness characteristics in recreational male runners

Commercially available foot orthoses are advocated for the treatment of chronic running injuries, such as patellofemoral pain, yet the mechanisms behind their effects are not well understood. This study aimed to examine the limb and joint stiffness characteristics when running with and without orthotics. Twelve recreational runners ran at 4.0 m/s. Limb stiffness was obtained using a spring-mass model of running by dividing the peak vertical ground reaction force (GRF) by the amount of limb compression. Knee and ankle joint stiffness’s were calculated by dividing the peak sagittal plane joint moment by the joint angular excursion. Differences between orthotic and non-orthotic running conditions were contrasted using paired samples t-tests. The results indicate that both peak knee extensor moment (orthotic = 2.74±0.57 and no-orthotic = 3.12±0.62 Nm/kg) and knee stiffness (orthotic = 5.56±1.08 and no-orthotic = 6.47±1.40 Nm/kg rad) were significantly larger when running without orthotics. This study may give further insight into the mechanical effects of commercially available foot orthoses. The current investigation provides some evidence to suggest that orthoses may be able to improve patellofemoral pathologies in recreational runners although further investigation is required.

Influence of barefoot and shod running on limb and joint stiffness characteristics during running

Influence of barefoot and shod running on limb and joint stiffness characteristics during running Jonathan Sinclair, Stephen Atkins & Paul John Taylor a University of Central Lancashire, Centre for Applied Sport and Exercise Science, Preston, United Kingdom b University of Central Lancashire, Centre for Applied Sport and Exercise Science, Preston, United Kingdom c University of Central Lancashire, School of Psychology, Preston, United Kingdom Published online: 18 Jun 2015.

The Effects of Barefoot and Shod Running on Limb and Joint Stiffness Characteristics in Recreational Runners

ABSTRACTThe authors aimed to determine the effects of barefoot (BF) and several commercially available barefoot-inspired (BFIS) footwear models on limb and joint stiffness characteristics compared with conventional footwear (CF). Fifteen male participants ran over a force platform at 4.0 m.s−1, in BF, BFIS, and CF conditions. Measures of limb and joint stiffness were calculated for each footwear. The results indicate that limb and knee stiffness were greater in BF and minimalist BFIS than in CF. CF and more structured BFIS were associated with a greater ankle stiffness compared with BF and minimalist BFIS. These findings serve to provide further insight into the susceptibility of runners to different injury mechanisms as a function of footwear.

Gender Differences in Limb and Joint Stiffness during the Fencing Lunge

The aim of the current investigation was to examine gender differences in limb and joint stiffness characteristics during the fencing lunge. Ten male and ten female fencers completed simulated lunge movements. Lower limb kinematics were collected using an eight camera optoelectric motion capture system which operated at 250 Hz. Measures of limb and joint stiffness were calculated as a function of limb length and joint moments divided by the extent of limb and joint excursion. Gender differences in limb joint stiffness parameters were examined statistically using independent samples t-tests. The results showed firstly that both limb (male = 64.22 ±19.12, female = 75.09 ±22.15 N.kg.m) and hip stiffness (male = 10.50 ±6.00, female = 25.89 ±15.01 Nm.kg.rad) were significantly greater in female fencers. In addition it was also demonstrated that knee moment (male = 1.64 ±0.23, female = 2.00 ±0.75 Nm.kg) was significantly larger in females. On the basis of these observations, the findings from the current investigation may provide further insight into the aetiology of the distinct injury patterns observed between genders in relation to fencing.

Sex differences in limb and joint stiffness in recreational runners

PurposeFemale runners are known to be at greater risk from chronic running injuries than age-matched males, although the exact mechanisms are often poorly understood. The aim of the current investigation was to determine if female recreational runners exhibit distinct limb and joint stiffness characteristics in relation to their male counterparts.MethodsFourteen male and fourteen female runners ran over a force platform at 4.0 m • s<sup>-1</sup>. Lower limb kinematics were collected using an eight-camera optoelectric motion capture system operating at 250 Hz. Measures of limb and joint stiffness were calculated as a function of limb length and joint moments divided by the extent of limb and joint excursion. All stiffness and joint moment parameters were normalized to body mass. Sex differences in normalized limb and knee and ankle joint stiffness were examined statistically using independent samples t tests.ResultsThe results indicate that normalized limb (male = 0.18 ± 0.07, female = 0.37 ± 0.10 kN • kg • m<sup>-1</sup>) and knee stiffness (male = 5.59 ± 2.02, female = 7.34 ± 1.78 Nm • kg • rad<sup>-1</sup>) were significantly greater in female runners.ConclusionsOn the basis that normalized knee and limb stiffness were shown to be significantly greater in female runners, the findings from the current investigation may provide further insight into the aetiology of the distinct injury patterns observed between sexes.

EFFECTIVE DYNAMIC STIFFNESS MODEL AND ITS EFFECTS ON ROBOT SAFETY AND PERFORMANCE

Due to the limited control bandwidth of pneumatic artificial muscles, joint stiffness characteristics and their effects on safety and performance of human-friendly robots should be considered in the frequency domain. This paper introduces the concept of effective dynamic stiffness and validates its model with the Stanford Safety Robot. Experimental results show that the dynamic stiffness demonstrates limited effects on the impact acceleration given the same impact velocity and controller gain, whereas it significantly affects control performance of position tracking due to pressure-induced non-linearities. A stiffness optimization strategy for safety and performance is discussed as a design guideline of human-friendly robots.

Lower extremity joint stiffness characteristics during running with different footfall patterns

The purpose of this study was to examine the knee and ankle joint stiffness and negative joint work during running when participants utilised their preferred and non-preferred footfall pattern. A total of 40 healthy, young runners (20 habitual forefoot (FF) and 20 habitual rearfoot (RF) runners) served as participants in this study. Three-dimensional data were obtained using a motion capture system and a force platform. The participants completed over-ground trials in each of two conditions: 1. their natural footfall pattern; and 2. their non-preferred footfall pattern. Joint stiffness was calculated by the ratio of the change in joint moment and the change in joint angle during the energy absorption phase of support. Negative joint work was calculated as the integral of the joint power-time curve during the same time interval. It was observed that joint stiffness was different between the footfall patterns but similar for both groups within a footfall pattern. A stiffer knee and a more compliant ankle were found in the FF pattern and the opposite in the RF pattern. Negative work was greater in the ankle and less in the knee in the FF pattern and the reverse in the RF pattern. We conclude that runners, in the short term, can alter their footfall pattern. However, there is a re-organisation of the control strategy of the joint when changing from a FF to a RF pattern. This re-organisation suggests that there is a possible difference in the types of injuries that may be sustained between the FF and the RF footfall patterns.

Analysis of No. 50 Taper Joint Stiffness Under Axial and Radial Loading

This paper is concerned with the joint stiffness characteristics of the standard 7/24 taper interface. Experimental identification of joint stiffness parameters is performed on No. 50 tapers, using a special test setup, by implementing a frequency response function (FRF) based method for joint parameter identification, in conjunction with finite element modeling of the substructure. The effects of axial and radial loading as well as taper wear on the taper joint stiffness are examined. It is shown that taper joint stiffness nonuniformly increases with axial preloading and decreases with radial loading. Validation of the identified stiffness values is given by comparing the predicted natural frequencies of the taper assembly with experimentally measured values.

Strength and rotational response of moment connections to tubular columns using flowdrill connectors

Using the flowdrill process it is possible to form threaded holes in steel tubes even with wall thicknesses less than 12 mm. Ordinary bolts may then be used to secure endplate beam connections to tubular columns. A series of tests was conducted to investigate the strength and rotational stiffness characteristics of joints made in this way. The results of the tests described on both thick flush endplates and extended endplates show that strengths approaching the plastic capacity of the supported beam and large rotational capacities can be obtained. Deformation of the tube face gives excellent ductility but the joints have relatively low stiffness for a nominally rigid joint. Connections of this type are ideally suited for use in semi-rigid design methods.