Negative tension controls stability and structure of intermediate filament networks

Networks, whose junctions are free to move along the edges, such as two-dimensional soap froths and membrane tubular networks of endoplasmic reticulum are intrinsically unstable. This instability is a result of a positive tension applied to the network elements. A paradigm of networks exhibiting stable polygonal configurations in spite of the junction mobility, are networks formed by bundles of Keratin Intermediate Filaments (KIFs) in live cells. A unique feature of KIF networks is a, hypothetically, negative tension generated in the network bundles due to an exchange of material between the network and an effective reservoir of unbundled filaments. Here we analyze the structure and stability of two-dimensional networks with mobile three-way junctions subject to negative tension. First, we analytically examine a simplified case of hexagonal networks with symmetric junctions and demonstrate that, indeed, a negative tension is mandatory for the network stability. Another factor contributing to the network stability is the junction elastic resistance to deviations from the symmetric state. We derive an equation for the optimal density of such networks resulting from an interplay between the tension and the junction energy. We describe a configurational degeneration of the optimal energy state of the network. Further, we analyze by numerical simulations the energy of randomly generated networks with, generally, asymmetric junctions, and demonstrate that the global minimum of the network energy corresponds to the irregular configurations.

Hamstring Torque, Velocity and Power Elastic Band Measurements during Hip Extension and Knee Flexion

The quantitative dynamic monitoring of the performance of hamstring muscles during rehabilitation and training cannot currently be undertaken using elastic resistance bands. Hip extension with a fully extended knee involves hamstring agonists, while knee flexion involves only the hamstring. The purpose of this study is to provide normative values of torque, velocity and power involving hamstring muscles opposing elastic bands. Twenty amateur athletes aged 25.7 ± 4.9, were studied during two motor tasks—hip extension and knee flexion, both isometric & dynamic—with an elastic resistance band and DINABANG portable instrument. We compared the peak isometric torque in hip extension with agonists (2.93 Nm/kg) and without them (1.21 Nm/kg): the difference is significant. The peak angular limb velocity—starting at 50% of the maximum torque—is smaller in hip extension with agonists (215.96°/s) than in a knee flexion without them (452.56°/s). The combination of peak torque and peak velocity estimates power and there is no difference (p = 0.051) with and without agonists: 452.56°Nm/s.kg without agonists and 542.13°Nm/s.kg with them. This study opens the possibility of monitoring torque–velocity–power profiles for hamstring exercise in open chain.

Treatment of Phalangeal Joint Stiffness Related to Proximal Phalangeal Bone Fractures: Therapeutic Effects on the Range of Motion and Finger Pain

Purpose: Proximal phalangeal bone fractures with displacement are treated using operative procedures. These fractures can cause stiffness of the interphalangeal or metacarpophalangeal joints, which can be relieved using various operative and nonoperative techniques. This study analyzed the range of motion (ROM) and pain after a combination therapy to treat finger stiffness following proximal phalangeal fractures.Methods: Fifty-two patients who underwent operative procedures for proximal phalangeal fractures and showed finger stiffness from March 2015 to January 2021 were included in this retrospective study. The patients in group 1 (n=24) performed elastic resistance exercises, while those in group 2 (n=28) underwent conventional exercise. ROM and pain score were measured at 5, 8, and 12 weeks postoperatively. Furthermore, a patient with a swan-neck deformity and intractable stiffness was treated using partial translocation of the extensor apparatus, and the postoperative outcome is presented.Results: Group 1 showed a larger ROM and less pain than group 2 at 12 weeks postoperatively (p<0.05). Patients in both groups exhibited notable improvements with regard to ROM and pain during the study period (p<0.05). In addition, the swan-neck deformity accompanying hyperextension of the proximal interphalangeal joint was significantly relieved.Conclusion: Proximal phalangeal bone fractures can lead to stiffness of the interphalangeal and metacarpophalangeal joints. Joint stiffness was relieved using an elastic resistance exercise protocol in the early postoperative period. Intractable stiffness showing a fixed joint angle can be treated with thorough tenolysis and corrective surgery.

Effect of different training models on motoric and swimming performance in prepubescent swimmers

Background and Study Aim. The aim of this study was to examine the effects of different training programs on the improvement of motoric and swimming performance prepubescent swimmers. Material and Methods. Forty-five children between the ages of 9 -11 years with at least 2 years of training experiences, participated in the study. Three different [(1) dry-land with elastic resistance band group + swimming (ERB); (2) dry-land without elastic resistance band (DL) + swimming and (3) swimming group (SG) with swimming training alone] training group were formed. And a 12-week training program was implemented thought the study. Biceps, chest, waist, hip, thigh body circumference measurements were taken from all participants. Vertical jump (VJ), flexed-arm strength (FAS), speed, upper body strength (UBS), Standing horizontal jump (SHJ), flexibility, aerobic endurance (AE), balance, and 50 m freestyle swimming (FS) score were tested on the participants. As statistical analysis, normality and homogeneity of variance assumption were checked (Shapiro-Wilk and Levene tests, respectively). A non-normal distribution was found. The values of each variable were expressed as mean ± standard deviation, and median. The training effects within the groups were evaluated using analyses of Friedman for repeated measures and the level of significance was set at p<0.05 for all tests. Results. There was a significant difference in SHJ, UBS, FAS, speed, and FS score among the assessment times 1-3 and 1-4 in both of ERB and DL training groups (p<0.05). ERB and DL training were significantly effective compared to the SG on VJ, FAS, speed, UBS, and freestyle swimming performance (p<0.05). Conclusions: The study findings showed that DL training more effected relatively on motoric performance.

The Effects of Elastic Band Exercises with PNF on Shooting Speed and Accuracy in Ball Hockey Players during the COVID-19 Pandemic

The coronavirus pandemic has affected life and left one of the strongest negative effects on sport. The aim of our study was to evaluate how a simple exercise performed with elastic resistance during the COVID-19 pandemic, when athletes cannot train, affects the basic shooting characteristics of ball hockey players. Extra-league ball hockey players (N = 30, age 19–37 years) were randomly divided into an experimental group, which performed elastic resistance exercises with Proprioceptive Neuromuscular Facilitation (PNF) elements for eight weeks, and a control group, which did not perform any exercises. Before the start of the experiment and after it was completed, the speed and accuracy of shooting were measured. In experimental group, there was no decrease after 8 weeks in the shooting speed, and in the control group, there was a statistically significant decrease. There was a deterioration in the accuracy of shooting in both groups; however, in the experimental group, the deterioration was not significant. The results show that even three simple exercises with elastic resistance according to the PNF concept performed 10 times per day for eight weeks can maintain the level of basic skills of ball hockey players—the speed and accuracy of shooting—even when no other training is performed.

Quantifying Muscle Forces and Joint Loading During Hip Exercises Performed With and Without an Elastic Resistance Band

An increase in hip joint contact forces (HJCFs) is one of the main contributing mechanical causes of hip joint pathologies, such as hip osteoarthritis, and its progression. The strengthening of the surrounding muscles of the joint is a way to increase joint stability, which results in the reduction of HJCF. Most of the exercise recommendations are based on expert opinions instead of evidence-based facts. This study aimed to quantify muscle forces and joint loading during rehabilitative exercises using an elastic resistance band (ERB). Hip exercise movements of 16 healthy volunteers were recorded using a three-dimensional motion capture system and two force plates. All exercises were performed without and with an ERB and two execution velocities. Hip joint kinematics, kinetics, muscle forces, and HJCF were calculated based on the musculoskeletal simulations in OpenSim. Time-normalized waveforms of the different exercise modalities were compared with each other and with reference values found during walking. The results showed that training with an ERB increases both target muscle forces and HJCF. Furthermore, the ERB reduced the hip joint range of motion during the exercises. The type of ERB used (soft vs. stiff ERB) and the execution velocity of the exercise had a minor impact on the peak muscle forces and HJCF. The velocity of exercise execution, however, had an influence on the total required muscle force. Performing hip exercises without an ERB resulted in similar or lower peak HJCF and lower muscle forces than those found during walking. Adding an ERB during hip exercises increased the peak muscle and HJCF but the values remained below those found during walking. Our workflow and findings can be used in conjunction with future studies to support exercise design.