Beyond activity patterns: The complex process of activity management among individuals with chronic musculoskeletal pain after an orthopaedic trauma.

CONTEXT: Individuals must change the way they perform activities in response to chronic pain. In the literature, three activity patterns are commonly described: avoidance, pacing, and persistence. Many studies have explored these activity patterns. However, little research has delved into the factors that lead people to adopt a particular activity behaviour. This study aimed to explore the relationship that people with chronic musculoskeletal pain have with activity and highlight the factors underlying their practices. METHODS: The qualitative study was conducted by researchers in the social sciences, physiotherapy, psychology, and rehabilitation medicine. Observations of vocational workshops and semi-structured interviews were conducted with 33 persons undergoing rehabilitation for chronic musculoskeletal pain after an accident. RESULTS: Patients' declarations and actions show that any one patient will alternate between activity patterns: the same person may adopt a strategy of avoidance, pacing or persistence depending on the context, the importance of the activity, personal objectives, and representations of self, pain, and activity. The decision to engage in a particular behaviour is based on a process of self-negotiation weighted by the circumstances, the nature of the activity, the importance attached to it, and the individual's perceived ability. CONCLUSION: Our study emphasized the complexity of physical, social, and contextual factors that intervene in the relationship toward activity. Rather than favouring pacing, the therapist's role in rehabilitation might be to reinforce the reflexive process and the patient's adaptability in approaching the activity, to foster the capacity to find flexible solutions. SIGNIFICANCE: Patients choose an activity pattern (avoidance, pacing, persistence) according to the challenges they face in their daily lives. Context, representations of self and activity, as well as goals sought influence these choices. Some patients report having learned to adapt their activity management strategies. Therefore, therapeutic approaches in the rehabilitation context could focus on these adaptive capacities to offer patients optimal pain and activity management and develop their ability to use different strategies according to the circumstance.

The concept of the mobilized domain: how it can explain and predict the forces exerted by a cohesive granular avalanche on an obstacle.

ABSTRACT: The calculation of the impact pressure on obstacles in granular flows is a fundamental issue of practical relevance, e.g. for snow avalanches impacting obstacles. Previous research shows that the load on the obstacle builds up, due to the formation of force chains originating from the obstacle and extending into the granular material. This leads to the formation of a mobilized domain, wherein the flow is influenced by the presence of the obstacle. To identify the link between the physical mobilized domain properties and the pressure exerted on obstacles, we simulate subcritical cohesionless and cohesive avalanches of soft particles past obstacles with circular, rectangular or triangular cross-section using the Discrete Element Method. Our results show that the impact pressure decreases non-linearly with increasing obstacle width, regardless of the obstacle's cross-section. While the mobilized domain size is proportional to the obstacle width, the pressure decrease with increasing width originates from the jammed material inside the mobilized domain. We provide evidence that the compression inside the mobilized domain governs the pressure build-up for cohesionless subcritical granular flows. In the cohesive case, the stress transmission in the compressed mobilized domain is further enhanced, causing a pressure increase compared with the cohesionless case. Considering a kinetic and a gravitational contribution, we are able to calculate the impact pressure based on the properties of the mobilized domain. The equations used for the pressure calculation in this article may be useful in future predictive pressure calculations based on mobilized domain properties. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10035-021-01196-1.

Underlying Asymmetry within Particle Size Segregation.

We experimentally study particle scale dynamics during segregation of a bidisperse mixture under oscillatory shear. Large and small particles show an underlying asymmetry that is dependent on the local particle concentration, with small particles segregating faster in regions of many large particles and large particles segregating slower in regions of many small particles. We quantify the asymmetry on bulk and particle scales, and capture it theoretically. This gives new physical insight into segregation and reveals a similarity with sedimentation, traffic flow, and particle diffusion.

Interleukine-6 (IL-6) synthesis and gp130 expression by human pericardium.

Growing evidence shows that cytokines of the IL-6 family play an important regulatory role in heart physiology such as inducing cardiomyocyte hypertrophy. The purpose of this study was to see if IL-6 and its soluble receptors (sIL-6R and sgp130) could be detected in pericardial fluids, and to see if they are produced by the pericardium. We report that human pericardial fluid from patients with coronary pathologies contained IL-6, sIL-6R, and sgp130. However, the levels present in sera and pericardial fluid did not correlate, which suggests local production. This observation was confirmed by in vitro studies demonstrating massive IL-6 production by cultured pericardial samples, which could be strongly inhibited by methylprednisolone. RT-PCR studies revealed that IL-6 was weakly expressed in fresh tissues and strongly induced after culture. In situ hybridisation and immunohistochemical analysis showed that IL-6 and gp130 were mainly present in mesothelial cells. sIL-6R and sgp130 were also produced by pericardium in vitro, and their synthesis was upregulated by methylprednisolone. Taken together, these results demonstrate that IL-6 is present in pericardial fluid and that its presence could be due to synthesis by pericardial tissue. In vitro studies suggest that IL-6 production by this tissue could be strongly induced and regulated. A potential paracrine role of these factors in cardiomyocyte functions in normal or pathological conditions is discussed.

Frictional-collisional regime for granular suspension flows down an inclined channel

Here granular suspensions refer to very concentrated suspensions of particles within a Newtonian fluid. Under certain conditions given in the paper, the bulk stresses mainly result from the combination of frictional and collisional interactions at the particle scale. The corresponding flow regime is called the frictional-collisional regime. The constitutive equation adapted to this regime is not well known. We propose a constitutive model based on the balance between frictional and collisional interactions. We have applied this model to granular flow down an inclined channel. It is shown that the mass flow rate is proportional to the flow depth.

Alpha-adrenoceptor stimulation induces hypertrophy and increases L-type calcium current density in neonatal rat ventricular cardiomyocytes in culture.

Effects of chronic alpha-adrenoceptor stimulation on hypertrophy and L-type calcium current (I(Ca-L) ) were investigated in neonatal rat ventricular cardiomyocytes in culture using whole-cell patch-clamp technique and measurement of protein- and RNA-to-DNA ratios. Chronic exposure to norepinephrine (2 microM) plus propranolol (2 microM) of cardiomyocytes during 1 and 3 days in culture increased cell membrane capacitance, protein- and RNA-to DNA ratios and was accompanied by an increase in I(Ca-L) density. These effects were not observed in the presence of prazosin (2 microM) suggesting that they could be due to alpha(1) -adrenoceptor stimulation. They were also prevented by cycloheximide (5 microM) and actinomycin D (1 microM). These effects were not observed in 1 and 3 day-cultured cells pre-treated for only 1 hour with norepinephrine. They were potentiated when calcium concentration was increased in the culture medium and, in contrast they were abolished in the presence of the L-type calcium current inhibitor, nifedipine (2 microM). The present study demonstrates that hypertrophy induced by long-term stimulation of alpha(1) -adrenoceptors is accompanied by an increase in the expression of functional calcium channels in neonatal rat cardiomyocytes. These results reveal the existence of a novel alpha(1) -mediated positive regulation of L-type calcium current different from that due to acute stimulation of alpha(1) -adrenoceptors in neonatal ventricular cardiomyocytes.