Acute effects of foam rolling on passive stiffness,stretch sensation and fascial sliding: A randomized controlled trial

PurposeFoam Rolling (FR), aims to mimic the effects of manual therapy and tackle dysfunctions of the skeletal muscle and connective tissue. It has been shown to induce improvements in flexibility, but the underlying mechanisms are poorly understood. The aim of the present study was to further elucidate the acute, systemic and tissue-specific responses evoked by FR.MethodsIn a crossover study, 16 (34 ± 6y, 6f) participants received all of the following interventions in a random order: a) 2 × 60 seconds of FR at the anterior thigh, b) 2 × 60 seconds of passive static stretching of the anterior thigh (SS), and c) no intervention (CON). Maximal active and passive knee flexion range of motion (ROM), passive stiffness, sliding of fascial layers, as well as knee flexion angle of first subjectively perceived stretch sensation (FSS) were evaluated before and directly after each intervention.ResultsFlexibility increased only after, FR (active (+1.8 ± 1.9%) and passive ROM (+3.4 ± 2.7%), p = .006, respectively) and SS (passive ROM (+3.2 ± 3.5%), p = .002). Angle of FSS was altered following FR (+4.3° (95% CI: 1.4°–7.2°)) and SS (+6.7° (3.7°–9.6°)), while tissue stiffness remained unchanged after any intervention compared to baseline. Movement of the deepest layer (−5.7 mm (−11.3 mm to −0.1 mm)) as well as intrafascial sliding between deep and superficial layer (−4.9 mm (−9.mm to −0.7 mm)) decreased only after FR.ConclusionFR improved knee flexion ROM without altering passive stiffness, but modified the perception of stretch as well as the mobility of the deep layer of the fascia lata. The mechanisms leading to altered fascial sliding merit further investigation.     

A Study of Friendship Choices in College in Relation to Church Affiliation,in-Church Preferences,Family Size,and Length of Enrollment in College

Summary

The purpose of the present study was to compare the body-buffer zones of 15 violent and 15 nonviolent male colored prisoners in South Africa, both between and within each group, and to make cross-cultural comparisons between the present and previous data. The mean age of the Ss in the violent group was 33.0 years, and 32.4 years in the nonviolent group. The body-buffer zone was measured by means of a behavioral task, and the results supported previous findings in that the violent Ss had significantly larger mean zones than the violent ones (p < .01). However, the zones for the present Ss were considerably larger than those of Ss used in previous studies, a fact that may be ascribed to cultural differences.     

Body configuration as a predictor of centre of mass displacement in a forward reactive step

In balance perturbations that elicit backwards reactive steps, body configuration at stepping contact is related to likelihood of balance recovery. However, less is known about the relationship between body configuration (at stepping contact) and underlying centre of mass (COM) dynamics during dynamic perturbations requiring a forward reactive step. Accordingly, the primary objective of this study was to characterize the potential relationships between body configuration and COM displacement during simulated trips. Towards determining the robustness of these relationships, trips were simulated in both baseline and increased passive joint stiffness conditions. Sixteen healthy adults participated in this study. Trips were simulated using a tether release paradigm where participants were suddenly released, necessitating a forward step (onto a force plate) to recover their balance. Trials were performed in a baseline unconstrained condition, and in a ‘corset’ condition to increase passive stiffness of the trunk and hips. In all trials, whole body kinematics and kinetics were collected. Multiple linear regression models were run to assess the relationship of body angles to COM displacement in both the anteroposterior (AP) and mediolateral (ML) planes. Regression models showed a significant association of sagittal plane body configuration to both COM displacement at stepping contact and maximum COM displacement in the AP plane. Across models, the strongest predictor was the trail leg angle. Associations were stronger in the increased passive stiffness condition (average R² = 0.366) compared to the baseline condition (average R² = 0.266). Poor association of body configuration to COM displacement was found in the ML plane. The significant associations observed between body configuration and COM dynamics in simulated trips supports the potential downstream application of these models in identifying individuals with impaired balance control and increased fall risk.     

Passive leadership,role stressors,and affective organizational commitment: A time-lagged study among health care employees

IntroductionThis study examines the relationships of passive leadership and role stressors to affective organizational commitment among hospital employees.ObjectiveThis study's objective was to understand the mediating effect of role stressors (conflict, overload, and ambiguity) in the relation between passive leadership and affective organizational commitment.MethodWe used a structural equation modeling approach on a sample of 185 hospital employees and a time-lagged design in which predictor and mediators were assessed at Time 1 and affective organizational commitment was obtained 3 years later.ResultsFindings revealed that passive leadership was positively related to all three role stressors and that role ambiguity fully mediated a negative relationship between passive leadership and affective organizational commitment. Moreover, the relationship between passive leadership and role conflict was stronger when role overload was high.ConclusionThis study suggests organizations should strive to limit the emergence of passive leadership behaviors among supervisors due to their detrimental effects on the long-term development of affective commitment via role ambiguity.     

Dynamic angular stiffness about the metatarsophalangeal joint increases with running speed

Altering the longitudinal bending stiffness of footwear has the potential to affect mechanics of the metatarsophalangeal (MTP) joint. Recent efforts have been put forth to identify an optimal bending stiffness of footwear to improve running performance. However, little is known about how this optimal bending stiffness may change with running speed. The purpose of this study was to investigate how dynamic angular stiffness about the MTP joint changes across running speeds. Eighteen participants ran at five speeds from 3.89 to 6.11 m/s. Metatarsophalangeal joint angles, moments, and stiffness were estimated for each speed. Two MTPJ load-displacement metrics were defined, active and critical stiffness. Instantaneous stiffness of the MTP joint was also quantified. There was a significant main effect of speed on critical stiffness (p < .001), maximum MTP moment (p < .001), MTP moment at maximum dorsiflexion (p < .001), and MTP range of motion (p = .013). There was no effect of speed on active stiffness (p = .094). These results support the notion that involvement of the MTP joint increases with running speed. Individual contributions of the foot and shoe to the MTP joint moment and stiffness suggest that the foot appears to dominate the stiffness of the foot-shoe complex and torque generation about the MTP joint. Instantaneous stiffness fluctuated throughout stance phase, suggesting that foot-shoe complex stiffness is time dependent. The ratio by which critical stiffness and MTP joint range of motion increase with running speed may provide insight for how to guide construction of performance footwear. These results suggest that when utilizing MTP joint mechanics for insights into designing a shoe for performance purposes, the effect of speed should be taken into consideration.     

Does social support predict smoking abstinence in dual-smoker couples? Evidence from a dyadic approach

Background and Objectives: Romantic partners have a significant influence on their health behaviors. Evidence for the effectiveness of social support for smoking abstinence, however, is mixed and the role of social support for smoking abstinence in dual-smoker couples is understudied.

Design: 77 dual-smoker couples were assessed 30 days after a joint quit attempt using a dyadic approach.

Methods: Received and provided support, self-reported and objectively measured smoking abstinence were assessed from both partners. Actor and partner effects of received and provided support on self-reported and objectively measured smoking abstinence and their difference for men and women were investigated with the Actor–Partner Interdependence Model using multilevel modeling.

Results: A significant actor effect emerged: Higher reports of received emotional support were related to an increased likelihood of objective smoking abstinence for men and women alike. For men only, partner effects of women’s received emotional and instrumental support emerged (p?<?.10): Higher reports of women’s support receipt were associated with an increased likelihood of men’s self-reported abstinence.

Conclusion: Received emotional support seems to play a key role in dual-smoker couple’s abstinence, whereas provided support does not seem to make a difference in successful quitting in dual-smoker couples.     

Arch structure is associated with unique joint work,relative joint contributions and stiffness during landing

To examine lower extremity joint contributions to a landing task in high-(HA) and low-arched (LA) female athletes by quantifying vertical stiffness, joint work and relative joint contributions to landing.MethodsTwenty healthy female recreational athletes (10 HA and 10 LA) performed five barefoot drop landings from a height of 30 cm. Three-dimensional kinematics (240 Hz) and ground reaction forces (960 Hz) were recorded simultaneously. Vertical stiffness, joint work values and relative joint work values were calculated using Visual 3D and MatLab.ResultsHA athletes had significantly greater vertical stiffness compared to LA athletes (p = 0.013). Though no differences in ankle joint work were observed (p = 0.252), HA athletes had smaller magnitudes of knee (p = 0.046), hip (p = 0.019) and total lower extremity joint work values (p = 0.016) compared to LA athletes. HA athletes had greater relative contributions of the ankle (p = 0.032) and smaller relative contributions of the hip (p = 0.049) compared to LA athletes. No differences in relative contributions of the knee were observed (p = 0.255).ConclusionsThese findings demonstrate that aberrant foot structure is associated with unique contributions of lower extremity joints to load attenuation during landing. These data may provide insight into the unique injury mechanisms associated with arch height in female athletes.     

Ankle Intrinsic Stiffness in Subcortical Poststroke Subjects

The authors' purpose was to evaluate bilateral ankle intrinsic stiffness in subcortical poststroke subjects. Ten subcortical poststroke subjects and 10 healthy controls participated in this study. The ankle passive stiffness at 3 different speeds and the electromyographic activity of the soleus, the gastrocnemius, and the tibialis anterior muscles of poststroke contralesional (CONTRA) and ipsilesional (IPSI) limbs and of one limb of healthy subjects were assessed. Ankle electromyographic activity was collected to ensure that reflexive or voluntary muscle activity was not being elicited during the passive movements. A significant interaction was observed between the effects of the limb (IPSI vs. CONTRA vs. control) and ankle position, F(4, 28) = 3.285, p = .025, and between the effects of the limb and the velocity of stretch, F(2, 14) = 4.209, p = .037. While increased intrinsic stiffness was observed in the CONTRA limb of poststroke subjects at ankle neutral position when the passive stretch was applied with a velocity of 1°/s (p = .021), the IPSI limb of poststroke subjects presented increased stiffness at 20º of plantar flexion when the stretch was applied with a velocity of 5°/s (p = .009) when compared to healthy group. Subcortical poststroke subjects present increased intrinsic stiffness in both the CONTRA and IPSI limbs in specific ankle amplitudes.     

Differential hemodynamic effects during the provision of active and passive support in the laboratory

Objective: Recent research has pointed to the cardiovascular benefits of providing social support to others in times of stress; however, little is known about what factors influence such benefits.

Design and measures: In a between-groups design, we investigated the possible interaction between intimacy (friend vs. stranger) and support type (active vs. passive) in determining the cardiovascular responses of support providers. Eighty participants had their blood pressure and heart rate monitored while providing either active or passive social support to a friend or a stranger who completed a stress task.

Results: Although there was no interaction effect, a significant main effect showed that those who provided passive support showed larger decreases relative to those in the active support condition. There was no effect of intimacy. Further, these effects withstood adjustment for a number of potential confounds (e.g. sex and body mass index).

Conclusion: It appears that the greatest physiological benefit for social support providers may come from providing passive, rather than active support, regardless of whether the support receiver is a friend or a stranger.     

Self-consciousness impairments in schizophrenia with and without first rank symptoms using the moving rubber hand illusion

IntroductionThe moving rubber hand illusion allows the evaluation both the sense of body ownership and agency using visuo-motor stimulations.MethodsWe used the moving rubber hand illusion in anatomic congruence with explicit measures to compare active asynchronous and passive synchronous movements in patients diagnosed with schizophrenia with first rank symptoms (FRS) (n = 31) versus without FRS (n = 25).ResultsPatients with FRS are characterized by a lack of agency in active asynchronous condition. The two groups had no sense of ownership in synchronous passive condition. Using a multivariate regression model, we found an association between agency and body ownership measures in the active asynchronous condition in two groups (OR: 1.825, p < 0.001). In the passive condition, this association was only present in the group with first rank symptoms (OR: 2.04, p < 0.001).ConclusionTemporal proximity and sensorimotor information are essential in the understanding of self-consciousness disorders in schizophrenia.     

Psychological and autonomic effects of art making in college-aged students

Background and objectives: Anxiety disorders comprise the most common category of mental illness among US young adults. Art making might be one method to help reduce anxiety, but the few studies investigating this have used only subjective measures of anxiety. Design: This study employed both subjective (self-reported state anxiety from the State-Trait Anxiety Inventory) and objective (heart rate variability) measures to assess whether 30-minute periods of art making reduced anxiety in 47 first-year college students prior to their final examinations. Methods: Students participated in free-form painting, mandala coloring, clay modeling, and control sessions. Results: Repeated-measures ANOVA with post hoc analysis revealed significantly greater pre- to post-session reductions in anxiety for all three types of art-making sessions than for the control session, as measured objectively. Measured subjectively, only free-form painting yielded a significant decrease in anxiety compared to the control session. Conclusions: Given the health benefits of anxiety reduction, further study is warranted to determine the duration of art making's anxiety-reducing effect.     

Positive relationship between passive muscle stiffness and rapid force production

We aimed to examine the relationship among the muscle shear modulus at rest, maximal joint torque, and rate of torque development (RTD). Twenty-seven participants (28 ± 5 years, 13 women) were recruited in the study. The cross-sectional area (CSA) of the medial gastrocnemius (MG) muscle belly and shear modulus at an ankle joint angle of 0° were calculated using magnetic resonance imaging and ultrasound shear wave elastography, respectively. Subsequently, participants performed maximal isometric plantar flexion at 0° ankle joint angle [maximal voluntary contraction (MVC) test] as fast and hard as possible (RTD test). RTD was calculated from the time–torque curve over time intervals of 0–30, 0–50, 0–100, 0–150, and 0–200 ms from the onset of plantar flexion during the RTD test and was normalized by MVC torque to exclude muscle strength. MG CSA correlated significantly with MVC torque (r = 0.572), whereas MG shear modulus did not. In contrast, MG shear modulus correlated significantly with normalized RTD at all time intervals (r = 0.460–0.496). These results suggest that passive muscle stiffness is not associated with muscle force; however, higher passive muscle stiffness at a given joint angle may contribute to rapid force production.     

Instruction Modes for Motor Control Skills Acquisition: A Randomized Controlled Trial

Abstract

The objective was to compare two different instruction modes used to teach patients with nonspecific chronic low back pain (CLBP) to perform a lumbar motor control task. The three intervention instruction modes used were: common verbal explanation of a motor task based on a motor control therapeutic exercise (MCTE-control group), MTCE instructed using motor imagery (MI) and MCTE instructed using tactile feedback (TF). The main outcome measure was lumbar motor control of the neutral position test. Forty-eight patients with CLBP were randomly allocated into three groups of 16 patients per group. The MI strategy was the most effective mode for developing the motor control task in an accurate and controlled manner, obtaining better outcomes than TF or verbal instruction.     

Extreme damping in compliant composites with a negative-stiffness phase

Compliant composite unit cells were made with negative stiffness constituents. Flexible silicone rubber tubes were incorporated in a post-buckled condition to achieve negative stiffness. Large peaks in the mechanical damping tan delta were observed in these systems. Maximum damping was orders of magnitude in excess of the material damping of the silicone rubber.     

Muscular contribution to low-back loading and stiffness during standard and suspended push-ups

Push-up exercises are normally performed to challenge muscles that span upper extremity joints. However, it is also recognized that push-ups provide an effective abdominal muscle challenge, especially when the hands are in contact with a labile support surface. The purpose of this study was to compare trunk muscle activation levels and resultant intervertebral joint (IVJ) loading when standard and suspended push-ups were performed, and to quantify and compare the contribution of trunk muscles to IVJ rotational stiffness in both exercises. Eleven recreationally trained male volunteers performed sets of standard and suspended push-ups. Upper body kinematic, kinetic, and EMG data were collected and input into a 3D biomechanical model of the lumbar torso to quantify lumbar IVJ loading and the contributions of trunk muscles to IVJ rotational stiffness. When performing suspended push-ups, muscles of the abdominal wall and the latissimus dorsi were activated to levels that were significantly greater than those elicited when performing standard push-ups (p<.05). As a direct result of these increased activation levels, model-predicted muscle forces increased and consequently led to significantly greater mean (p=.0008) and peak (p=.0012) lumbar IVJ compressive forces when performing suspended push-ups. Also directly resulting from the increased activation levels of the abdominal muscles and the latissimus dorsi during suspended push-ups was increased muscular contribution to lumbar IVJ rotational stiffness (p<.05). In comparison to the standard version of the exercise, suspended push-ups appear to provide a superior abdominal muscle challenge. However, for individuals unable to tolerate high lumbar IVJ compressive loads, potential benefits gained by incorporating suspended push-ups into their resistance training regimen may be outweighed by the risk of overloading low-back tissues.     

Increased visual bias in children with developmental coordination disorder: Evidence from a visual-tactile temporal order judgment task

BackgroundPrevious studies have suggested that children with developmental coordination disorder (DCD) rely heavily on vision to perform movements, which may contribute to their clumsy movements. However, few studies have objectively and quantitatively investigated the perceptual biases of children with DCD.MethodsA visual-tactile temporal order judgment (TOJ) task was used to measure and compare the perceptual biases of 19 children with DCD and 19 age- and sex-matched typically developing children. The point of subjective equality, which demonstrates when “visual first” and “tactile first” judgment probabilities are equal (50%), obtained by analyzing the results of the visual-tactile TOJ task, was used as an indicator of perceptual biases. Further, variables (age and manual dexterity in all participants; motor function, autism spectrum disorder and attention-deficit hyperactivity disorder traits, and depressive symptoms in children with DCD) associated with perceptual biases were examined with correlation analysis.ResultsChildren with DCD had significantly stronger visual bias than typically developing children. Overall correlation analysis showed that increased visual bias was significantly correlated with poor manual dexterity.ConclusionChildren with DCD had a strong visual bias, which was associated with poor manual dexterity.     

Hopping skill in individuals with Down syndrome: A qualitative and quantitative assessment

IntroductionIndividuals with Down syndrome (DS) show a delayed acquisition of gross motor skills. Among gross motor skills, hopping is a particular form of jumping that can be performed using one leg. Despite its large use during play and physical activity, this skill in adults with DS has not received much attention so far. Here, we aim at investigating hopping skill in adults with DS both from a quantitative and qualitative point of view.MethodsCenter of mass and dominant leg kinematics during hopping over distance were recorded from 24 adult individuals with DS and from 21 typically developed adults (TD) using two inertial measurement units positioned on the posterior aspect of the lower back and on the lateral malleolus of the hopping leg. From linear acceleration and angular velocity signals, hopping frequency (HF), cycle, stance and flight duration (CD, SD, FD), vertical stiffness (K_V) and peak to peak linear acceleration and angular velocities about the cranio-caudal, antero-posterior and medio-lateral axes were extracted. A qualitative process assessment of the hopping skill was carried out using the performance criteria of the test for gross motor development (TGMD-3). The extracted parameters were submitted to analysis of covariance, with stature as a covariate to rule-out possible confounding effects.ResultsThe qualitative assessment highlighted a poorer hopping performance in the DS group compared to the TD group. DS participants showed higher HF and K_V, shorter CD, SD, FD and lower angular velocity about the cranio-caudal axis compared to the TD group. Significant correlations between the temporal parameters of the quantitative assessment and the results of the qualitative assessment were observed.DiscussionThe poorer motor competence in hopping in individuals with DS compared to TD peers may be related to the shorter flight time and higher vertical stiffness observed in TD peers. The adopted instrumental approach, overcoming the limitations of subjective evaluations, represents a promising opportunity to quantify motor competence in hopping.     

Calculations of the minimal perimeter for N deformable cells of equal area confined in a circle

Candidates to the least perimeter partition of a disk into N?planar connected regions are calculated for N?≤?43. A Voronoi construction is used to randomly create the candidates and then the perimeter of each is found with the Surface Evolver. Formulae for the perimeter and number of peripheral regions are given, and the candidates classified according to their topology. The simulation technique also provides improved candidates to the unconstrained problem of finding the least perimeter arrangement of N planar regions.     

Exploring the geometric and mechanical characteristics of the spine musculature to provide rotational stiffness to two spine joints in the neutral posture

Joint stiffness is inherently linked to both performance and injury. Muscular activation is the predominant provider of stiffness to the lumbar spine, and is essential to ensure optimal spine performance. The purpose of the current paper was to examine the potential of the trunk muscles to provide rotational joint stiffness at two spine joints in the neutral posture, and to demonstrate the sensitivity of this stiffening potential to various muscle orientation and stiffness assumptions. Two separate anatomical models were utilized to analyze the muscular contributions to the 3-dimensional rotational stiffness about each of the L1-L2 and L4-L5 spine joints. Total muscular stiffening potentials, for both joints in each anatomical model, were found to be highest about the global lateral bend axis, and lowest about the global axial twist axis. The stiffening potential was found to depend highly on both the assumed muscle stiffness coefficient (q value) and the moment arm of the muscle about the joint in question. Analyses of spine stiffness were found to be greatly affected by both the anatomical representation of the surrounding musculature and the selection of the q value in the determination of muscular stiffness. Inappropriate choices of either of these factors could lead to errors in stiffness and subsequently stability estimates, and in the interpretation and possible clinical recommendations stemming from such estimates.     

The asymptotic distribution of commonality components

Commonality components have been defined as a method of partitioning squared multiple correlations. In this paper, the asymptotic joint distribution of all 2 ^k – 1 squared multiple correlations is derived. The asymptotic joint distribution of linear combinations of squared multiple correlations is obtained as a corollary. In particular, the asymptotic joint distribution of commonality components are derived as a special case. Simultaneous and nonsimultaneous asymptotic confidence intervals for commonality components can be obtained from this distribution.This work was supported in part by the Spencer Foundation and the National Science Foundation.The authors are grateful to Bryna Siegel-Gorlick for her help in obtaining the data used in Example 4.3, and to the referees for their comments and suggestions.