Tadashi Suga

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.

Superior sprint performance is associated with greater activation of the lower-limb muscles, particularly the thigh muscles, during sprinting. T2-weighted magnetic resonance imaging (MRI) is an ideal method for assessing spatial patterns of thigh muscle activation in response to dynamic whole-body movements. In this T2-weighted MRI study, we examined the intermuscular and intramuscular distributions of sprint-induced activation across 13 thigh muscles in male sprinters using a low-volume sprint protocol designed to preserve maximal performance while minimizing fatigue. Specifically, we evaluated intermuscular activation patterns and intramuscular regional differences in thigh muscle activation. Thirty-two well-trained male collegiate sprinters (100-m seasonal best time: 11.02 ± 0.28 s) completed the low-volume sprint protocol consisting of three maximal 60-m sprints with 2-min recovery intervals on an indoor track. T2-weighted MRI scans were acquired before and after the sprint protocol. Intermuscular activation patterns were assessed by comparing the percentage change in T2 across 13 thigh muscles. Intramuscular regional differences were assessed by comparing T2 changes among regions within each muscle. During the low-volume sprint protocol, 60-m sprint times did not differ significantly among the three maximal sprints ( P = 0.349). Despite this minimized approach, significant T2 increase were observed across 12 of the 13 thigh muscles (3.1–19.1%, all P < 0.05), with the greatest increase in the semitendinosus. In particular, T2 changes in the hamstrings and adductors were markedly greater than those in the quadriceps femoris. Furthermore, significant regional differences in T2 changes were identified in six of the 11 muscles analyzed (all P < 0.05). Notably, the T2 change in the proximal region of the biceps femoris long head was significantly greater than those in the middle and distal regions (both P < 0.05), which may be relevant to the regional susceptibility to hamstring strain injury. These findings suggest that maximal sprint performance in male sprinters involves complex muscle recruitment mechanisms characterized by intermuscular and intramuscular distributions of thigh muscle activation. A better understanding of these features may contribute to the development of novel sprint strategies to enhance sprint performance and prevent sprint-related sports injuries in sprinters.

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.

This study aimed to examine differences in the intestinal microbiota diversity in individuals with and without a history of a lateral ankle sprain (LAS). Fifty male college student athletes with (n=32) and without (n=18) a LAS history participated in this study. Faecal samples were collected in the morning after awakening during an off-season, and faecal microbiota were characterized via bacteria 16S rRNA amplicon sequencing. Alpha-diversity metrics and ß-diversity indices were calculated to assess the gut microbiota diversity. The LAS-history group significantly had lower Chao1 (p=0.020) and abundance-based coverage estimators (p=0.035) indices compared to the control group. Gut microbiota composition was not significantly different between athletes with a LAS history and controls (R² =0.01, p 0.414). Athletes with a history of LASs had significantly higher proportions of Bacteroides Fragilis (p=0.024) and Ruminococcus Gnavus (p=0.021) compared with controls. The gut microbiota of athletes with a LAS history had less richness compared to controls, indicating potential associations between a LAS and the gut microbiota. This study highlights the potential link of a LAS to global health. This study may help raise awareness of strategies to prevent long-term health-related negative consequences in people suffering from LASs.

Resistance exercise (RE) with blood flow restriction (BFR) is recognized as a beneficial strategy in increasing skeletal muscle mass and strength. However, the effects of BFR on changes in perceptual parameters, particularly those related to exercise adherence, induced by RE are not completely understood. In this study, we examined the exercise adherence-related perceptual responses to low-load BFR-RE. Sixteen young males performed both BFR and non-BFR (NBFR) sessions in a crossover design. The bilateral knee extensor low-load RE was performed with a standard BFR-RE protocol, consisting of four sets (total 75 repetitions), using 20% of one-repetition maximum. BFR-RE was performed with 200 mmHg pressure cuffs placed around the proximal region of the thighs. NBFR-RE was performed without pressure cuffs. The ratings of perceived exertion and leg discomfort measured using the Borg's Scales were higher for BFR-RE session than for NBFR-RE session (both p < 0.001 for interaction effect). The Feeling Scale-measured affect and Task Motivation Scale-measured task motivation were lower for BFR-RE session than for NBFR-RE session (both p < 0.05 for interaction effect); by contrast, the Numerical Rating Scale-measured perceived pain was higher for BFR-RE session than for NBFR-RE session (p < 0.001 for interaction effect). The Physical Activity Enjoyment Scale-measured enjoyment immediately after RE was lower with BFR than with NBFR (p < 0.001). These findings suggest that BFR exacerbates the exercise adherence-related perceptual responses to low-load RE in young males. Therefore, further studies are needed to develop effective strategies that minimize the BFR-RE-induced negative effects on perceptual responses.

This study examined the relationship between body segment mass and running performance in endurance runners. The total (muscle, fat, and bone masses), lean (muscle mass), and fat masses of the leg, arm, and trunk segments in 37 well-trained endurance runners were measured using dual-energy X-ray absorptiometer. The relative segment mass was calculated by normalizing the absolute mass to body mass. There were no significant correlations between absolute total, lean, and fat masses of all 3 segments and personal best 5000-m race time. No significant correlations were also observed between all 3 relative masses of the arm segment and personal best 5000-m race time. In contrast, medium positive correlations were observed between the relative total and lean masses of the leg segment and personal best 5000-m race time (r = .387 and .335, respectively, bothP ≤ .031). Furthermore, large negative correlations were observed between the relative total and lean masses of the trunk segment and personal best 5000-m race time (r = −.500 and −.548, respectively, bothP ≤ .002). These findings suggest that a mass distribution with smaller leg mass and greater trunk mass may be advantageous for achieving better running performance in endurance runners.

The length of rest interval between sets (i.e., inter-set rest interval) is an important variable for resistance exercise program. However, the impact of the inter-set rest interval on improvements in cognitive function following resistance exercise remains unknown. In this study, we compared the effect of short rest interval (SRI) vs. long rest interval (LRI) protocols on post-exercise cognitive inhibitory control (IC) improvements induced by low-intensity resistance exercise. Twenty healthy, young males completed both SRI and LRI sessions in a crossover design. The bilateral knee extensor low-intensity resistance exercise was programed for six sets with 10 repetitions per set using 40% of one-repetition maximum. The inter-set rest interval lengths for SRI and LRI protocols were set for 1 and 3min, respectively. The color-word Stroop task (CWST) was administrated at six time points: baseline, pre-exercise, immediate post-exercise, and every 10min during the 30-min post-exercise recovery period. The levels of blood lactate, which may be an important determinant for improving IC, throughout the 30-min post-exercise recovery period were significantly higher following SRI protocol than following LRI protocol (p=0.002 for interaction effect). In line with this result, large-sized decreases in the reverse-Stroop interference score, which represent improved IC, were observed immediately after SRI protocol (d=0.94 and 0.82, respectively, vs. baseline and pre-exercise) as opposed to the moderate-sized decreases immediately after LRI protocol (d=0.62 and 0.66, respectively, vs. baseline and pre-exercise). Moreover, significant decreases in the reverse-Stroop interference score were observed from 10 to 30min after SRI protocol (all psp=0.046 for interaction effect). We suggest that the SRI protocol is more useful in improving post-exercise IC, potentially via greater circulating lactate levels, compared to the LRI protocol. Therefore, the inter-set rest interval length may be an important variable for determining the degree of cognitive function improvements following resistance exercise in healthy young males.

Purpose: We previously reported that the cross-sectional area of the quadriceps femoris is correlated with the sprint performance of preadolescent sprinters. This finding suggests a close relationship between knee extensor torque-enhancing morphology and sprint performance in this young population. To further clarify this issue, in this study, we examined the relationships of the quadriceps femoris muscle volume (MV) and knee extensor moment arm (MA) with sprint performance in preadolescent sprinters. Methods: The quadriceps femoris MV and knee extensor MA in 15 sprint-trained preadolescent boys were measured using magnetic resonance imaging. Sprint performance was evaluated using a personal best 100-m sprint time and the higher 50-m sprint velocity of two 50-m sprint tests. Results: The quadriceps femoris MV and knee extensor MA were significantly correlated with personal best 100-m sprint time (r = −0.810 and −0.752, P ≤ 0.001 for both) and 50-m sprint velocity (r = 0.814 and 0.702, P < .01 for both). Furthermore, the relative quadriceps femoris MV normalized to body mass was significantly correlated with both the personal best 100-m sprint time (r = −0.620, P = .014) and 50-m sprint velocity (r = 0.686, P = .005). In contrast, no significant correlations were observed between the relative knee extensor MA normalized to body height and both sprint performance parameters. Conclusions: These findings suggest that the quadriceps femoris size, rather than the knee extensor MA dimension, is a more important morphological factor for achieving superior sprint performance in preadolescent sprinters.

The plantar flexor torque plays an important role in achieving superior sprint performance in sprinters. Because of the close relationship between joint torque and muscle size, a simple assumption can be made that greater plantar flexor muscles (i.e., triceps surae muscles) are related to better sprint performance. However, previous studies have reported the absence of these relationships. Furthermore, to examine these relationships, only a few studies have calculated the muscle volume (MV) of the plantar flexors. In this study, we hypothesized that the plantar flexor MVs may not be important morphological factors for sprint performance. To test our hypothesis, we examined the relationships between plantar flexor MVs and sprint performance in sprinters. Fifty-two male sprinters and 26 body size-matched male non-sprinters participated in this study. On the basis of the personal best 100 m sprint times [range, 10.21–11.90 (mean ± SD, 11.13 ± 0.42) s] in sprinters, a K-means cluster analysis was applied to divide them into four sprint performance level groups (n = 8, 8, 19, and 17 for each group), which was the optimal number of clusters determined by the silhouette coefficient. The MVs of the gastrocnemius lateralis (GL), gastrocnemius medialis (GM), and soleus (SOL) in participants were measured using magnetic resonance imaging. In addition to absolute MVs, the relative MVs normalized to body mass were used for the analyses. The absolute and relative MVs of the total and individual plantar flexors were significantly greater in sprinters than in non-sprinters (all p < 0.01, d = 0.64–1.39). In contrast, all the plantar flexor MV variables did not differ significantly among the four groups of sprinters (all p > 0.05, η² = 0.02–0.07). Furthermore, all plantar flexor MV variables did not correlate significantly with personal best 100 m sprint time in sprinters (r = −0.253–0.002, all p > 0.05). These findings suggest that although the plantar flexor muscles are specifically developed in sprinters compared to untrained non-sprinters, the greater plantar flexor MVs in the sprinters may not be important morphological factors for their sprint performance.