This study aimed to evaluate a musculoskeletal screening method for elementary school students using ultrasound and lower limb flexibility assessments, with the goal of early detection of Osgood-Schlatter disease during the growth period. A total of 143 boys in the fourth to sixth grades of elementary school from a single prefecture underwent musculoskeletal screening between November 2021 and February 2023. Using a diagnostic ultrasound device, the tibial tuberosity was observed, and its developmental stage was classified based on Ehrenborg’s four-stage classification (Ehrenborg G and Lagergren C. 1961. Acta Chir Scand 121: 315–327). The presence of Osgood-Schlatter disease was determined based on the presence of irregularities in the ultrasound image. Lower limb flexibility was assessed quantitatively using finger-floor distance (FFD) and heel-hip distance (HHD). The cartilaginous stage (C stage) was the most common developmental stage observed. Osgood-Schlatter disease was identified in eight children (5.6%) and was found only in the epiphyseal (E) and bony (B) stages (p = 0.004, φ = 0.308). HHD was significantly greater in the Osgood-Schlatter group (p = 0.040, r = 0.680). In some children without knee pain or tenderness, irregularities in the tibial tuberosity were detected on ultrasound imaging, suggesting that ultrasound imaging may be useful for the early detection of asymptomatic lesions. This screening approach, which combines ultrasound examination and flexibility assessment, is expected to serve as a novel method for the early detection and prevention of musculoskeletal disorders in children during their growth period. Further large-scale studies and continued investigation into methods for assessing flexibility in growing children are warranted.

While mortality due to spinal cord injuries (SCI) and urinary tract infections has markedly decreased, the incidence of malignant tumors and lifestyle-related diseases is increasing among people with physical disabilities. However, regular assessment of body weight and composition remains challenging in this population. This cross-sectional study aimed to clarify the relationship between waist circumference, trunk fat percentage, and visceral fat level, with a particular focus on waist circumference as an easily measurable indicator. A total of 151 individuals participated, including 42 with SCI, 42 with cerebrovascular disease (CVD), and 67 without disabilities. Waist circumference, trunk fat percentage, and visceral fat level were measured in sitting and supine positions for all participants, and in the standing position for those without disabilities. Position-related differences were analyzed, with statistical significance set at 5%. Waist circumference varied by measurement position, with the highest values observed in the sitting position. For participants with SCI, the average waist circumference was 90.9 ± 13.1 cm in the sitting position and 81.6 ± 10.9 cm in the supine position. In participants with CVD, the respective values were 93.4 ± 9.8 cm and 86.5 ± 8.5 cm. Waist circumference showed significant positive correlations with both trunk fat percentage and visceral fat level. Standard screening values may underestimate adiposity in people with physical disabilities. These findings suggest the necessity of adopting specific reference values and support the utility of waist circumference measurements taken in the sitting and supine positions in this population.

More research is needed to understand how exercise time and physical fitness relate to body size. In particular, there are no studies that have examined the relationship between physical activity and physical fitness, taking into account both overweight/obesity and thinness, using national samples. This study aimed to analyze exercise time by body size and physical fitness using a Japanese national sample of Japanese children and adolescents. The survey included 19,471 primary and 10,596 secondary schools in Japan. After excluding participants with missing data, the analysis included 878,348 Year 5 primary school students and 757,358 Year 8 secondary school students. Body mass index (BMI) was calculated based on participants’ height and weight, and they were subsequently categorized into four BMI groups: underweight, normal weight, overweight, and obese. Physical fitness was classified as high or low based on the total score from eight physical fitness tests. Exercise time was assessed via a questionnaire and compared between the high- and low-fitness groups within each BMI category. Among the boys and girls in primary and secondary schools, exercise time was greater in the high-fitness group compared to the low-fitness group across all four BMI categories (underweight, normal weight, overweight and obesity). In conclusion, this study suggested that exercise time is positively associated with higher physical fitness regardless of whether an individual is obese, overweight, normal weight or underweight. These results may indicate the importance of promoting exercise time among all children, and further longitudinal studies are needed.

The dorsolateral prefrontal cortex (DLPFC) is a brain region responsible for executive function. Recent studies have reported that low-intensity physical activity (LPA) can activate this region and improve executive function. Carbohydrate mouth rinse (CMR), an ergogenic conditioning method in sports science, has been shown to activate the DLPFC. This study hypothesized that LPA-induced improved executive function could be synergistically enhanced by CMR. We investigated the impact of combining LPA with CMR to improve executive function. Seventeen healthy university students (eight male, nine female) participated. For LPA, instead of commonly-used exercise modalities, such as bicycle ergometers or treadmills, a seated dual-task exercise (DE) was employed that involved performing cognitive tasks and physical activity simultaneously, which is considered effective for cognitive function. Four trials were conducted using a crossover design: trial 1 control (CON), trial 2 (CON+CMR), trial 3 (DE), and trial 4 (DE+CMR). The Trail Making Test Type B (TMT-B, Japanese version) and Stroop Test (ST, Japanese version) assessed cognitive function, and CMR was administered with a 6% glucose solution four times during CON and DE. The results indicated a significant interaction in Interference Rate I of the ST, showing improved performance due to DE. An interaction was also observed in Interference Rate II, highlighting enhanced performance when DE was combined with CMR. Although no interaction was found in TMT-B, a pre-post comparison revealed improved performance in the DE+CMR trial. These findings suggest the potential for further improvement in executive function when DE is combined with CMR.

The coronavirus disease 2019 (COVID-19) pandemic has hampered group exercise. We aimed to determine the relationship between group-exercise implementation status in 2018 and 2020 and the incidence of frailty in 2020, including the COVID-19 pandemic among older adults in Japan. This longitudinal study included older adults belonging to senior clubs, divided into four groups based on the continuity of group-exercise participation. Frailty was assessed using the Kihon Checklist, in which total scores of ≥8 points indicated frailty status. The relationship between group-exercise implementation status and the incidence of frailty was evaluated using Poisson regression with robust variance. Exercise time at the individual level in each group was analyzed using Wilcoxon signed-rank tests. Overall, 1,241 participants were included, in which 249 individuals (20.1%) developed frailty. Compared to older adults who continued group exercise, those who discontinued group exercise (adjusted relative risk: 1.70, 95% confidence interval: 1.26–2.30) were more likely to become frail. Regarding the median exercise time (interquartile range), older adults who discontinued group exercise showed a significant decrease, from 25.7 (12.9–51.7) min/day to 17.1 (6.4–30.0) min/day; but those who started group exercise showed a significant increase from 19.3 (6.4–41.4) min/day to 20.0 (6.4–47.6) min/day. Group exercise implementation status in 2018 and 2020 was associated with incidence of frailty in 2020, including the COVID-19 pandemic. It was concluded that supporting group exercise is important for the prevention of frailty, even under social restrictions owing to infectious diseases.

High-intensity exercise induces the accumulation of hydrogen ions, resulting in a decrease in plasma and muscle pH (i.e., metabolic acidosis), a key mechanism contributing to fatigue. Alleviating metabolic acidosis is crucial for improving high-intensity exercise performance. Voluntary hyperventilation increases carbon dioxide (CO₂) elimination, reduces arterial CO₂ partial pressure (hypocapnia), and an increase in plasma pH (i.e., respiratory alkalosis). Pre-exercise voluntary hypocapnic hyperventilation is a potentially effective intervention for alleviating metabolic acidosis and has been proposed to enhance exercise performance during cycling and resistance exercise. Furthermore, this technique may reduce aerobic metabolism while increasing anaerobic metabolism by decreasing active skeletal muscle blood flow and inhibiting oxidative phosphorylation during subsequent exercise. According to the overload principle, stimulating the anaerobic energy system during each high-intensity training session can improve its capacity, ultimately enhancing high-intensity exercise performance. High-intensity exercise performed under hypoxic conditions such as using hypoxic chambers or hypoxic gas inhalation, has traditionally been employed to stimulate anaerobic metabolism more effectively than normoxic environments. However, such hypoxic interventions are often inaccessible to many athletes due to logistical constraints. This short review highlights recent findings on the acute effects of pre-exercise voluntary hypocapnic hyperventilation on exercise performance and metabolic responses during high-intensity exercise.

Efficient energy production is essential for endurance performance, and thus it is important to promote mitochondrial ATP production. Nicotinamide mononucleotide (NMN) is converted to the coenzyme nicotinamide adenine dinucleotide (NAD⁺), which contributes to mitochondrial ATP production. Meanwhile, paprika xanthophyll (PX), an oil-based extract from ripe red paprika, improves the oxygen-delivery capacity of red blood cells by increasing their membrane flexibility. This study was a randomized, placebo-controlled, double-blind, parallel-group trial that investigated the effects of intake of NMN (500 mg/day), PX (9 mg/day), or their combination for 8 weeks on endurance performance. The participants were male collegiate track-and-field athletes aged 18 years or older. As endurance performance, running velocity at lactate threshold, running velocity at the onset of blood lactate accumulation, and heart rate were evaluated using the lactate curve test. The results showed that NMN did not effectively improve endurance performance after intake for 8 weeks, which was the primary endpoint of this study. However, the results after intake for 4 weeks, as well as stratified analyses by blood NAD⁺ levels before intake, suggested that the combination of NMN and PX might improve endurance performance. Thus, both the increase in NAD⁺ induced by NMN intake and sufficient oxygen delivery induced by PX intake may be beneficial for promoting mitochondrial ATP production, thereby leading to improved endurance performance.

This study sought to determine the concurrent validity and reliability of 6-s peak power test (6PT) on an air and magnetically braked cycle ergometer (Wattbike). Firstly, 17 physically active male and female adults performed 6PT and force-velocity test (FVT), consisting of 3 short all-out cycle sprints against 3 different loads on an electromagnetically braked cycle ergometer (Power Max), on the same day in part 1 of the study (i.e., concurrent validity). Subsequently, 11 out of those participants performed the respective tests on three different days (a total of 6 measurements for each participant) in part 2 of the study (i.e., inter-day reliability). The order of the tests was counterbalanced in both parts of the study, and maximal power output (MPO) and peak power output (6PP) derived from FVT and 6PT, respectively, were retained for the subsequent analyses. A high correlation between MPO and 6PP (r = 0.97, [95% CI: 0.90-0.99], p < 0.01) was observed with the standard error of the estimate of 59.7 W in part 1 of the study. Moreover, excellent inter-day reliability was confirmed for both tests in part 2 of the study (coefficient of variation: MPO = 2.08 [95% CI: 1.56-3.28%], 6PP = 2.81 [95% CI: 2.11-4.43%]; intraclass correlation coefficient: MPO = 0.987 [95%CI: 0.959-0.996], 6PP = 0.965 [95%CI: 0.899-0.990]). This study showed that a valid and reliable value is obtained from a single short all-out cycle test (i.e., 6PT), which would enable a frequent follow-up of power production capacity of individuals.

Lactate administration has been suggested to affect energy metabolism by acting as an energy fuel and/or exhibiting various physiological responses. Although some previous studies have found that the intravenous infusion of lactate might increase energy expenditure, the effect of oral supplementation is unknown. In this study, we investigated the effects of acute oral lactate supplementation on energy metabolism during rest and exercise. Twelve healthy subjects (ten men and two women, average age 21.2 ± 0.8 years) participated in this single-blind, placebo-controlled, randomized crossover study. All subjects received two different supplements: supplements containing 1115 mg of lactate (LAC) and placebo supplements consisting of the same mass of glucose as the supplements in LAC (PLA). 1 hour after ingesting the supplements, they performed cycling exercise (unloaded, 70 rpm, 30 min). Measurements taken included oxygen consumption, blood lactate and glucose concentrations, heart rate, rating of perceived exertion, and gastric discomfort level. The results showed that the area under the curve for oxygen consumption during rest was significantly higher with LAC than with PLA treatment (LAC: 41.3 ± 3.7 ml/kg vs. PLA: 37.2 ± 5.5 ml/kg, p < 0.01). By contrast, no significant differences were observed between LAC and PLA treatments in any of the measurements during exercise. In conclusion, acute oral lactate supplementation increased oxygen consumption during rest.

American football (AF) has a high incidence of sports-related concussions (SRC), raising concerns about the long-term effects on neuromuscular function. This study aimed to compare the cortical silent period (cSP) and the strength of the cervical muscles to investigate neuromuscular function in patients with SRC. All 38 participants were males, including 12 AF players with a history of SRC, 9 AF players without a history of SRC, and 17 normal healthy males with no experience in contact sports. Cervical muscle strength was measured with a hand-held dynamometer. cSP was measured using transcranial magnetic stimulation. Electromyography was obtained from the upper trapezius muscle. AF players demonstrated stronger cervical muscle strength than the control group. No significant differences were observed in corticospinal excitability among the groups. AF players with a history of SRC demonstrated a significantly longer cSP than the control group (80.5 ± 27.8 ms vs. 113.1 ± 35.1 ms) (F (2, 32) = 3.66, p < .05). These results suggest that cortical inhibition of the cervical muscle is enhanced in AF players with a history of SRC. This could lead to neuromuscular dysfunction of the cervical muscles and should be considered an important factor in preventing recurrent SRC.

We aimed to examine the relationship between marathon time and running distance during 8 months before a race for runners who live in cold, snowy regions and those who do not. A questionnaire was conducted for male runners who participated in the 2018 Hokkaido Marathon held at the end of August. The subjects were divided into runners from Hokkaido (Hokkaido runners), which is a cold and snowy region, and runners from other regions (non-Hokkaido runners). In addition, Hokkaido and non-Hokkaido runners were divided into two groups, high-volume and low-volume runners, based on their average running distance over an 8-month period. Regardless of high-volume or low-volume, Hokkaido runners’ monthly running distances significantly increased from March compared to January, but non-Hokkaido runners showed no change in their monthly running distances. For non-Hokkaido runners, a significant correlation was found between cumulative monthly running distance and marathon time starting from 8 months prior to the marathon. On the other hand, among Hokkaido runners, no correlation was found between cumulative monthly running distance and marathon time for low-volume runners from January to April, or for high-volume runners from January to February or January to March. These results suggest that marathon times for runners from cold, snowy regions are more closely linked to seasonal changes in running distance than for other runners.

Strengthening of the hip external rotator muscles may improve pelvic floor muscle function. In this study, we examined the relationship between hip external rotator strength and pelvic floor muscle function in nulliparous women. This cross-sectional study included 59 women aged ≥18 years who had never given birth. Pelvic floor muscle function was measured using transabdominal ultrasound. Muscle strength during hip flexion, abduction, and external rotation, and handgrip strength were also measured. Multiple regression analysis was performed to examine the association between pelvic floor muscle function and hip external rotator strength. Fifty-five participants (average age: 20.3 years) were included in the final analysis. A single correlation was observed between pelvic floor muscle and hip flexor strength (r = 0.334, p = 0.013), hip abductors (r = 0.203, p = 0.038), and hip external rotators (r = 0.413, p < 0.001). Conversely, no relationship was observed between pelvic floor muscle function and handgrip strength (r = −0.124, p = 0.369). Multiple regression analysis revealed an independent association between pelvic floor muscle and hip external rotator muscle strength (β = 0.605, p = 0.032). However, no association was observed between pelvic floor muscle function and hip flexor (β = 0.086, p = 0.545), abductor (β = −0.052, p = 0.902), and handgrip strength (β = −0.012, p = 0.101). Hip external rotator muscle strength was associated with pelvic floor muscle function independently of hip flexor and abductor, and handgrip strength in nulliparous women. The findings suggest that hip external rotator strength may be related to pelvic floor muscle function in nulliparous women.

This study aimed to determine the effect of running step frequency (SF) on oxygen consumption during running on spot (ROS) exercises and low-speed running in adult male and female participants. Twenty Japanese participants (22 ± 1.2 years) were included. ROS exercises and running speeds of 4 km h^-1 and 5 km h^-1 were measured at SFs of 140, 160, 180 and 200 steps min^-1. Oxygen consumption, heart rate (HR), and rate of perceived exertion (RPE) were measured during exercise, and oxygen consumption were expressed as metabolic equivalents (METs). In the participants, ROS and 4 km h^-1 running showed no significant difference in SFs (140 steps min^-1 and 160 steps min^-1, respectively) and had significantly higher SFs of 200 steps min^-1 than the other SFs. Moreover, 5 km h^-1 running showed no significant difference between SFs of 140 steps min^-1, 160 steps min^-1 and 180 steps min^-1, and was significantly higher at an SF of 200 steps min^-1 than other SFs. Individual differences in METs at an SF of 180 steps min^-1 were similar at running speeds of 4 km h^-1 and 5 km h^-1. No difference was noted in oxygen consumption between SF of 140 steps min^-1 and 160 steps min^-1 during ROS exercise and 4 km h^-1 and 5 km h^-1 running. Oxygen consumption tended to increase depending on SF above 160 steps min^-1 during ROS, 4 km h^-1, and 5 km h^-1 running exercises. These results suggest that SF should be considered for low-speed running instruction.

Knee injuries in rugby union have higher incidence and severity than other injury types. However, the underlying mechanisms and trauma remain unclear. This study aimed to identify knee injury trends and clarify the associated mechanisms in male university rugby players using longitudinal injury surveillance and video analysis. An observational study with longitudinal injury surveillance included 198 university male rugby players who played at least one season over a six-season period (2017–2022). The mean incidence, severity, and burden of injuries were calculated by position and injury type. Video data of knee injuries in matches were analyzed by three analysts, who independently assessed variables, including mechanism/play, movement/posture, and external factors. Injury mechanisms were classified as direct, indirect, and non-contact. The incidence of knee injuries was 8.3/1000 h, with 29 videos analyzed. Indirect contact injury was the most frequent, with an incidence of 3.7/1000 h and a burden of 380 days/1000 h. A significant association was found between injury severity and movement direction, with being tackled from downwards and sideways directions showing a significant difference compared to other directions (Cramer’s V = 0.44). Most knee injuries were caused by being tackled, a heel strike, and an upright body position. Indirect injuries, the most frequent knee injury mechanism, imposed the highest burden. Movement direction may further affect injury severity. Despite their lower incidences, these injuries cause greater burden and severity than those observed in professional rugby, emphasizing the need for specialized prevention programs.

Walking for transportation (using your feet to travel to a destination) is influenced by multiple determinants, including psychological perceptions and environmental factors. Acceptable walking time indicates the maximum time (in minutes) a person would walk to reach a destination, and is a psychological factor whose association with walking behavior remains insufficiently examined. Therefore, this study clarified the relationship between acceptable walking time and actual walking behavior in the Japanese working-age population, hypothesizing a positive linear association. A cross-sectional online survey of 881 persons (males, n = 310; females, n = 571; age: 20–59 years) in Japan was conducted to analyze acceptable walking time. Participants indicated “What distance (in minutes) would you walk to a destination?” with responses categorized into six groups (≤2 to ≥21 min). Weekly walking time was measured using the International Physical Activity Questionnaire - Short Form (IPAQ-SF). Linear and quadratic trends were assessed using regression analysis with orthogonal polynomial contrast, adjusted for age and stratified by sex and residential location (Greater Tokyo vs rural Okinawa). Weekly walking duration showed significant positive linear associations with acceptable walking time across all four demographic groups, with some evidence of quadratic components in males after adjusting for age. These consistent positive associations were observed across both residential locations for both sexes, with predominantly linear patterns. This study confirmed a positive association between acceptable walking time and actual walking behavior in the Japanese working-age population, with consistent patterns across sex and locations. Acceptable walking time may serve as a useful psychological indicator of walking behavior.