Tadao Isaka

Previous investigations have identified the effectiveness of breathwork on both psychological and physical health for individuals under a resting state. However, there was no study investigating the effects of breathwork under a mentally‐fatigued state. The purpose of this study was to examine the acute effects of breathwork administered after the induction of mental fatigue by a cognitive tasks on primary self‐reported outcomes including positive and negative affect and self‐reported stress indices, as well as on secondary physiological outcomes including diaphragm function and stress‐related physiological responses. This study was employed with a randomized cross‐over study design. Twenty healthy university students voluntarily participated in this study. Each of them performed a 20‐min breathwork and control (quiet bed rest) condition following the Colour‐Word Stroop Task (CWST) in a randomized sequence over two days separated at least by a week. Participants completed self‐reported questionnaires for positive and negative affect and stress indices and underwent ultrasonographic assessments of the diaphragm function, saliva collection for cortisol and IgA, and heart rate variability assessments at baseline, pre‐CWST, post‐CWST, and post‐intervention. The breathwork condition demonstrated significantly higher positive affect at post‐intervention compared to the control condition ( p = 0.021). Right hemidiaphragm excursion and left hemidiaphragm thickness at end‐inspiration significantly increased from post‐CWST to post‐intervention in the breathwork condition. The breathwork condition appeared to improve positive affect and diaphragm function even under a mentally‐fatigued state, compared to the control condition. These findings indicate that breathwork may serve as a simple, accessible, and practical strategy to enhance subjective well‐being in a stressful environment and diaphragm function regardless of mental fatigue.

This study aimed to investigate whole-body joint torque and power during underwater undulatory swimming (UUS) using computational fluid dynamics and inverse dynamics. Coordinate data from the UUS and digital models of nine male swimmers were collected. Buoyancy and fluid force were determined using equations incorporating specific gravity and segment mass and using computational fluid dynamics, respectively. The joint torques of the swimmers’ bodies were determined using inverse dynamics. The powers of the corresponding joints were also determined. The hip and knee joints generated joint torque and positive power that were more than twice as large as those of the ankle, trunk, and shoulder joints for both downward and upward kicks. The knee joint produced negative power to avoid increasing the knee flexion angle related to deceleration during the first half of the downward kick. The ankle joint also produced negative power to prevent excessive plantar flexion during the corresponding phase. The hip, trunk, and shoulder joints produce negative power to prevent the oscillation of the upper body by absorbing mechanical energy from the lower limbs during the last half of the downward kick. This study showed that swimmers primarily generate torque and positive power using their hip and knee joints to perform UUS, whereas negative power is produced at the knee and ankle joints during the first half of the downward kick and at the trunk and shoulder joints during the last half of the corresponding kick.

Sport-related concussion has been associated with adverse psychological outcomes such as anxiety and depression. However, little is known about how concuss

Alterations in knee joint biomechanics have been observed in individuals with recurrent lateral ankle sprain, potentially affecting knee joint health. However, it remains unclear whether femoral cartilage morphology and composition are associated with recurrent lateral ankle sprain. We aimed to compare femoral cartilage cross-sectional area and T2 relaxation times using magnetic resonance imaging between individuals with and without recurrent lateral ankle sprains. In this single-blinded, case-control study conducted at a university imaging laboratory, 15 male participants with recurrent lateral ankle sprains (age = 21.3 ± 1.8 years, height = 177.2 ± 5.1 cm, body mass = 68.7 ± 5.8 kg) and 15 healthy controls (age = 21.3 ± 1.9 years, height = 173.7 ± 6.6 cm, body mass = 64.6 ± 5.7 kg) were included. Bilateral femoral articular cartilage images were acquired using T2 mapping compositional magnetic resonance scans of the tibiofemoral joint. A single reader manually segmented the medial cartilage on a sagittal image slice to evaluate the cross-sectional area and T2 relaxation time. A two-way repeated measures analysis of variance with Bonferroni post hoc analyses was used to analyze the magnetic resonance variables. Hedge g effect sizes using the pooled standard deviations were calculated, along with 95% confidence intervals (CIs) for each pairwise comparison. There were no differences in anthropometric characteristics between individuals with and without recurrent lateral ankle sprain ( P > .05). Participants with recurrent lateral ankle sprains exhibited a significantly greater femoral cartilage cross-sectional area than healthy controls, regardless of limb dominance ( P = .03, η ² = 0.16). In addition, T2 relaxation times were significantly longer in the dominant limb of participants with recurrent lateral ankle sprains than in healthy controls ( P = .02, Hedge g = 0.88, 95% CIs: 0.14–1.61) and in their nondominant limb ( P = .03, Hedge g = 0.72, 95% CIs: 0.16–1.25). No significant differences were observed between the dominant and nondominant limbs in the control groups ( P = .23, Hedge g = ‐0.26, 95% CIs: −0.74 to 0.24) or between the recurrent lateral ankle sprain and control groups in the nondominant limb ( P = .74, Hedge g = −0.12, 95% CIs: −0.82 to 0.61). These findings indicate altered femoral articular cartilage morphology and composition in participants with recurrent lateral ankle sprains. The findings of this study support the need for monitoring knee joint function and symptoms during rehabilitation in patients with recurrent lateral ankle sprains. A prospective longitudinal study with a larger and more diverse sample is needed to investigate these associations further.

Context : Female athletes frequently experience lateral ankle sprains (LAS) during unilateral jump-landing activities and face a significant risk of recurrent ankle injury. LAS has been associated with reduced diaphragm contractility and altered breathing mechanics. The diaphragm and breathing mechanics are crucial for mitigating landing impact, which is typically impaired in individuals with LAS. Given this connection, innovative rehabilitation approaches that address dysfunctional breathing mechanics may be warranted. To date, no research has investigated associations between breathing mechanics and landing kinetics in adolescent female athletes with LAS. This study aimed to compare ground reaction force (GRF) and dynamic stability during a single-leg stabilization task between female athletes with a history of LAS who exhibited diaphragmatic breathing patterns and those who had dysfunctional breathing patterns. Design : Case–control study. Methods : Two hundred eighty-three competitive female athletes with a previous history of LAS were recruited from middle school, high school, and Division I college teams. The Hi-Lo test was utilized to categorize participants as dysfunctional breathers or diaphragmatic breathers according to their breathing patterns. Each participant completed 3 trials of a single-leg drop-landing task. Normalized peak vertical and posterior GRF data were extracted, and the average loading rate was calculated from the normalized vertical GRF. The norm of the horizontal component of the GRF was used to calculate time to stabilization. Results : Forty female athletes with LAS history (14.1%) were classified as diaphragmatic breathers, and 243 (85.9%) were classified as dysfunctional breathers. Female athletes with LAS history who exhibited dysfunctional breathing patterns demonstrated a greater peak posterior GRF ( P = .01) and longer time to stabilization ( P = .04) compared with those who had diaphragmatic breathing patterns. Conclusions : Dysfunctional breathing patterns may contribute to decreased dynamic stability and force attenuation capabilities during single-leg landing tasks following LAS. Assessing the biomechanical dimension of breathing patterns may help clinicians identify patient-specific impairments in individuals with LAS, particularly those with deficits in dynamic postural stability and force attenuation.

Purpose : The aim of our study was to investigate age-related differences in childhood and adolescent boys’ performance, including initial reaction time and electromyographic (EMG) latencies of leg muscles during sprint start. Methods : Forty-six Japanese boys, aged 5–19 years, participated in this study. The participants performed 5 consecutive 2-m sprints, starting with the boys’ preferred split-stance starting posture. Ground reaction force data of the front and rear feet and surface EMG data of the rectus femoris, biceps femoris, and gastrocnemius muscles in both legs of all participants were measured using a wireless EMG system. Results : As chronological age increased, the initial reaction time was largely shortened until the breakpoint age of 8.6 years and was moderately shortened thereafter. The EMG latencies of the posterior thigh and shank muscles of the rear leg were also shortened largely long before reaching the adolescence; in contrast, those of the front leg muscles were largely shortened until adolescence. Conclusions : Reaction behavior with complex whole-body motion may develop long before the onset of adolescence. In particular, adjusting the rear leg motion may contribute to the rapid development of whole-body reaction maturation.

Dynamic stretching (DS) is a conditioning technique commonly used in sports. However, its effects on contralateral joint flexibility and elastic properties of the targeted muscle over several weeks remain unclear. Similarly, its impact on muscle functions, such as force or power exertion, is poorly understood. This study aimed to examine the effects of a 12-week DS program targeting the ankle plantar flexors on the joint flexibility, muscle strength, and elastic properties of the plantar flexors in stretched and contralateral legs. Eighteen healthy young adults (12 males and six females, aged 18-24 years) participated in this study. DS was performed on one leg of the ankle plantar flexors for 12 weeks (3 days weekly), while the other leg served as a non-intervention. Dorsiflexion range of motion (DFROM), muscle stiffness, and ankle plantar flexion strength (rate of torque development and isokinetic muscle strength) were assessed before and after the intervention. The muscle stiffness was measured using shear wave elastography on the gastrocnemius. DFROM significantly increased in both conditions (p < 0.05), whereas gastrocnemius stiffness significantly decreased only in the DS condition (p < 0.05). No significant changes were observed in the non-intervention condition. The ankle plantar flexion rates of torque development and isokinetic strength did not change in either condition. These findings suggest that 12 weeks of DS can reduce muscle stiffness and improve joint flexibility without affecting muscle strength while enhancing contralateral joint flexibility without altering muscle stiffness or strength.

We investigated the effects of acute exercise at different intensities and durations on the immune response to salivary antimicrobial peptides in young healthy men. Levels of four salivary antimicrobial peptides increased after exercise dependently or independently of exercise intensity and duration, whereas some salivary antimicrobial peptides did not change after exercise. These findings suggest that the secretory responses to acute exercise with different intensities and durations differ among salivary antimicrobial peptides.