Journal of Physical Fitness and Sports Medicine
Official journal of the Japanese Society Physical Fitness and Sports Medicine
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The Journal of Physical Fitness and Sports Medicine (JPFSM)
[Volume 15, Number 1 January 25, 2026]
Regular Article
- Received: March 21, 2024 / Accepted: October 9, 2024
Abstract
Purpose: The aims of the present study were to determine whether short maximal pedaling at optimal load (Lopt) improved maximal anaerobic power (MAnP) with changes in force and/or velocity, and if a difference in training volume influenced training outcomes in physically active male students. This study also attempted to establish better measurements for evaluating adaptations to short sprints at Lopt. Methods: Fourteen students were randomly divided into either a one-set training (OST) group or a higher volume training (HT) group. The OST group performed a single 8-s sprint. The HT group repeated 8-s pedaling until a peak power was under 90% of that in the previous set twice. To determine MAnP, participants pedal as rapidly as possible for 8-s at three different loads before, in the middle of and after the 4-week training intervention. Results: A 2-way ANOVA revealed that MAnP similarly increased after 2 to 4 weeks of training for both groups. Optimal cadence (velocity factor) and Lopt (force factor) increased during the first and last 2 weeks of training, respectively. The extent of increase in peak power was significantly lower in the Wingate anaerobic test (6.5 ± 1.4 %) than in the 8-s maximal effort pedaling test at near-Lopt (11.5 ± 1.3 %). Conclusion: Four weeks of a single 8-s maximal effort pedaling at Lopt on a cycle ergometer increased MAnP as well as high volume training. The increase resulted from an improvement in the velocity factor in the first half and force factor in the latter half of training. Furthermore, a non-specific test to training load and duration may underestimate the extent of training-induced increase in power compared to a specific test that more closely resemble a training protocol.
Regular Article
- Received: July 8, 2024 / Accepted: November 14, 2024
Abstract
Despite the known health impacts of rapid weight loss (RWL) in athletes, effective mitigation strategies, especially nutritional ones, remain underexplored. This study aimed to investigate the effects of Lactiplantibacillus pentosus ONRICb0240-containing food (b240) intake on salivary secretory immunoglobulin A (SIgA) secretion in judo athletes undergoing RWL. Therefore, 17 male competitive college judo athletes were categorized into two groups: the b240 intake (active group; n = 9) and no b240 intake (control group; n = 8). Both groups engaged in 4 weeks of regular training followed by 1 week of RWL. The active group consumed b240 daily, every evening before dinner, throughout the 5-week experiment. Participants documented upper-respiratory symptoms (URS) and abdominal conditions during the study. Saliva samples were collected, and physical fitness tests were performed on each participant at 0 weeks (before intervention), 4 weeks (before weight loss), and 5 weeks (after weight loss). Results showed that salivary SIgA secretion was significantly decreased in the control group after weight loss compared to before the intervention (0 weeks, p < 0.05), while no significant changes were observed in the active group. Compared to the control group, URS decreased, and the percentage of days participants reported their abdominal condition as “good” increased in the active group (p < 0.05). These findings suggest that regular intake of b240 may be beneficial for reducing the frequency of URS among judo athletes, potentially due to better maintenance of salivary SIgA secretion during training and RWL.
Regular Article
- Received: August 21, 2024 / Accepted: December 10, 2024
Abstract
Heavy exercise training may negatively affect the gastrointestinal status of athletes, often leading to poor athletic performance and physical condition. The gut microbiome plays aa important role in the pathogenesis of gastrointestinal disorders. However, the relationship between the gut environment and conditions in athletes remains to be investigated. In this study, we aimed to determine the relationship between the gut microbiome, stool pattern, and the physical condition of elite athletes. A total of 92 elite athletes participated in this study, and their gut microbiomes, stool patterns, and physical conditions were evaluated. The gut microbiome was analyzed using 16S rRNA sequencing. The stool patterns and subjective physical conditions were evaluated using questionnaires. The participants were divided into better and poorer physical condition groups based on the median value of the physical condition score. The prevalence of abnormal stool patterns was significantly higher in the poorer condition group than that in the better condition group. The abundance of Faecalibacterium was significantly higher and that of Bifidobacterium was significantly lower in the better condition group than those in the poorer condition group. Principal component analysis revealed that the stool pattern could be explained by the Faecalibacterium abundance and the physical condition scores. Together, these findings suggest that the gut microbiome, especially the Faecalibacterium and Bifidobacterium abundance, affects the stool patterns and physical conditions of elite athletes, indicating that the gut microbiome may play a role in controlling the gastrointestinal environment affected by physiological stress such as intense exercise.
[Volume 15, Number 2 March 25, 2026]
Regular Article
- Received: June 18, 2024 / Accepted: December 24, 2024
Abstract
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 males, nine females) participated. For LPA, instead of commonly-used exercise modalities, such as bicycle ergometers or treadmills, we employed a seated dual-task exercise (DE) 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 the 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.
Regular Article
- Received: September 20, 2024 / Accepted: January 6, 2025
Abstract
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; 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; 249 individuals (20.1%) newly developed frailty. Compared with older adults who continued group exercise, those who discontinued group exercise (adjusted relative risk: 1.70, 95% confidence interval: 1.26–2.30) was 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; 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 the incidence of frailty in 2020, including the COVID-19 pandemic. Supporting group exercise is important for the prevention of frailty, even under social restrictions owing to infectious diseases.
[Volume 15, Number 3 May 25, 2026]
Short Review
- Received: November 1, 2024 / Accepted: March 19, 2025
Abstract
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.
Regular Article
- Received: January 10, 2025 / Accepted: April 14, 2025
Abstract
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 of 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.
Regular Article
- Received: December 17, 2024 / Accepted: April 22, 2025
Abstract
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.
[Volume 15, Number 4 July 25, 2026]
Regular Article
- Received: February 27, 2025 / Accepted: June 3, 2025
Abstract
Objectives: 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. Methods: 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. Results: 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). Conclusions: 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.
Regular Article
- Received: February 20, 2025 / Accepted: June 10, 2025
Abstract
We aimed to examine the relationship between marathon time and running distance in the 8 months before the 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 accumulative 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 in cold, snowy regions are more closely linked to seasonal changes in running distance than for other runners.
Regular Article
- Received: May 27, 2025 / Accepted: July 18, 2025
Abstract
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 with other directions (Phi and Cramer's V=0.62, 0.44, p =0.025). 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.
[Volume 15, Number 5 September 25, 2026]
Regular Article
- Received: January 23, 2025 / Accepted: July 22, 2025
Abstract
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.
Regular Article
- Received: April 15, 2025 / Accepted: July 28, 2025
Abstract
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 ±1.2years) 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.
Regular Article
- Received: May 31, 2025 / Accepted: August 12, 2025
Abstract
Walking for transportation is influenced by multiple determinants including psychological perceptions and environmental determinants. Acceptable walking time is an indicator that evaluates the maximum time (in minutes) one would walk to reach a destination and is a psychological factor whose association with walking behavior has not been sufficiently examined. Therefore, this study aimed to clarify 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 (minutes) would you walk to a destination?” with responses categorized into six groups (≤2 to ≥21 minutes). Weekly walking time was measured using the International Physical Activity Questionnaire-short form. 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 versus 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 male groups 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.
[Volume 16, Number 1 January 25, 2027]
Regular Article
- Received: April 10, 2025 / Accepted: August 18, 2025
Abstract
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.
Regular Article
- Received: May 14, 2025 / Accepted: August 19, 2025
Abstract
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.
Regular Article
- Received: July 9, 2025 / Accepted: August 27, 2025
Abstract
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 with the low-fitness group across all four BMI categories (Underweight, normal-weight, overweight and obesity). In conclusions, this study suggested that exercise time is positively associated with higher physical fitness regardless of whether an individual is obese, underweight, or normal weight. These results may indicate the importance of promoting exercise time among all children, and further longitudinal studies are needed.
[Volume 16, Number 2 March 25, 2027]
Regular Article
- Received: July 24, 2025 / Accepted: September 10, 2025
Abstract
Lateral ankle sprains (LAS) account for a substantial proportion of ankle injuries in rugby union and are associated with a high recurrence rate. A history of LAS is known to increase future injury risk, yet few studies have quantitatively examined this relationship. This study aimed to investigate the epidemiological characteristics of LAS among male collegiate rugby players based on the presence or absence of prior injury history. A total of 146 players were prospectively followed over seven seasons and divided into two groups according to their LAS history. Group-specific exposure time was used to calculate injury incidence, severity, and mechanism-specific burden. A total of 131 LAS cases were recorded. The History group showed a significantly higher incidence rate (1.22/1,000 PHs) than the No History group (0.72/1,000 PHs), while no significant difference in severity was observed. Contact-related mechanisms, including other player collisions and lineout landings, were more frequent and burdensome in the History group. These findings suggest that injury history is not merely a contextual factor, but a key determinant of future injury risk and characteristics. Prevention and rehabilitation strategies should be tailored accordingly. Mechanism-specific training and history-informed return-to-play protocols are essential to reduce the burden of LAS in athletes with prior injuries.
Regular Article
- Received: February 22, 2025 / Accepted: September 10, 2025
Abstract
This study aimed to develop and conduct a preliminary validation of the hitoe system, a novel smartphone application and wearable device designed to tailor exercise loads to individual exercise tolerance, with the goal of supporting personalized cardiac rehabilitation. A preliminary validation study was conducted involving 28 healthy adults (26 males, mean age 42.3 ± 11.2 years). Participants used the hitoe system to perform 13 activities, including sedentary tasks, household chores, walking, and cycle ergometer. Exercise intensity was measured in metabolic equivalents (METs) and compared with values obtained using a standard gas analyzer. Statistical analyses, including intraclass correlation coefficients (ICCs) and Bland-Altman analyses, were applied to assess the accuracy and reliability of the device. The hitoe system demonstrated satisfactory agreement with gas analyzer measurements across most activities. Bland-Altman analyses revealed that the majority of data points fell within ±2.0 METs, indicating limits of agreement. High ICCs were observed for activities such as cycle ergometer (ICC = 0.797), vacuuming the floor (ICC = 0.693), and lifting a 5 kg weight (ICC = 0.614), reflecting strong reliability. In contrast, sedentary activities such as sitting (ICC = 0.033) and desk work (ICC = 0.144) showed lower ICCs, although the absolute differences between the two methods remained within approximately 1 MET. The preliminary findings suggest that the hitoe system may be useful for assessing physical activity intensity, particularly during higher-intensity activities. The system may offer a promising tool for real-time feedback and tailored exercise prescription in cardiac rehabilitation. Further studies involving patients with cardiovascular diseases are warranted to validate these preliminary results and enhance the system’s precision in clinical settings.
Regular Article
- Received: June 20, 2025 / Accepted: September 22, 2025
Abstract
This longitudinal study aimed to determine the performance-related knee injury risk factors in male university rugby union players. Baseline performance measurements were taken in the pre-season and included: (1) strength tests–maximal isometric voluntary contraction (MVC) and single-limb hop test; (2) balance tests–Balance Error Scoring System and Y Balance Test–Lower Quarter; and (3) movement quality–Landing Error Scoring System. The Limb Symmetry Index (LSI) was calculated using strength tests. Knee injury surveillance data, including incidence, severity, and burden, were tracked and analyzed over 1 year. Of the 79 candidate players, 64 completed the test set, and 58 were included in the analysis. We observed 15 knee injuries in 13 players. The injury incidence was 0.4 injuries/1000 player-hours (1000 h) (95% confidence interval [CI], 0.2–0.5); severity was 51 days (95% CI, 0–104); and the burden was 19 days/1000 h (95% CI, 11–31). High LSI of hip internal rotation (odds ratio [OR], 1.09; 95% CI, 1.02–1.16) and MVC of hip extension (OR, 1.10; 95% CI, 1.00–1.20) were identified as significant factors associated with the occurrence of knee injury. In conclusion, the present study suggests that knee injuries are associated with the LSI of hip internal rotation and MVC of hip extension. Players with high performance levels are more exposed to higher injury risks during matches. Given that performance test results may predict knee injury incidence, regular monitoring of such tests may help prevent knee injuries.
[Volume 16, Number 3 May 25, 2027]
Regular Article
- Received: July 7, 2025 / Accepted: September 29, 2025
Abstract
In Japan, research on how specific types of sedentary behavior are associated with academic performance among school-aged children remains limited. This cross-sectional study investigated the relationship between various sedentary behaviors and academic performance among Japanese children and adolescents. Data were collected in 2023 from 342 primary and 456 junior high school students in Unnan City, Shimane Prefecture. Academic performance was categorized as high or low based on median scores in Japanese and mathematics. Sedentary behaviors were assessed using a questionnaire—including time spent on reading books and newspapers and total recreational screen time, which was calculated from the time spent playing TV games, watching videos or using social networking services (SNS), and using educational tablets at home. Multiple linear regression analyses were conducted, adjusting for factors, such as gender, grade, breakfast habits, sleep duration, sports club participation, and cram school attendance. Spending < 2 hours on TV, games, watching videos, or SNS use was significantly associated with higher academic performance across school levels. Conversely, spending < 2 hours on total recreational screen time and using educational tablets at home was linked to higher scores among primary students. Reading books was positively associated with Japanese language scores in both groups. Thus, the type of sedentary activity plays a crucial role in the academic outcomes. A shorter duration of recreational screen time and educational and literacy-related behaviors were associated with higher academic performance. This study highlights the need for further longitudinal research considering household socioeconomic factors to better understand these associations.
Regular Article
- Received: May 27, 2025 / Accepted: October 2, 2025
Abstract
We aimed to develop regression models for estimating oxygen consumption (VO₂, ml·kg⁻¹·min⁻¹) during treadmill walking based on accelerations of the upper and lower limbs and walking velocity, quantitatively assess the contribution of each sensor location, and validate the accuracy and practicality of a simplified model. Eighteen healthy adults with regular exercise habits (nine men, nine women) participated in treadmill walking trials at varying speeds (3–6 km·h⁻¹; up to 5.5 km·h⁻¹ for women). Vector magnitude (VM) from triaxial accelerometers attached to both wrists and both ankles was recorded simultaneously with VO₂ measurements from a portable breath-by-breath gas analyzer. Multiple regression models were constructed using FootVM (ankle VM), HandVM (wrist VM), and walking velocity as predictors. FootVM alone showed a moderate correlation with VO₂ (R² = 0.464), but adding walking velocity substantially improved the model’s accuracy (Model 2: R² = 0.810, standard error of estimate = 1.25 ml·kg⁻¹·min⁻¹). Incorporating HandVM yielded only a minimal, non-significant model fit improvement (R² = 0.815, ΔAIC = +18.4, βstd = −0.06), with no meaningful statistical contribution. Bland–Altman analysis indicated 95% limits of agreement for estimation error within ±2.46 ml·kg⁻¹·min⁻¹, corresponding to < 1 MET (3.5 ml·kg⁻¹·min⁻¹). These findings support the rational selection of a simplified model using only FootVM and walking velocity, which achieved a balance between high accuracy and practicality. The ability to estimate VO₂ precisely using only ankle-mounted accelerometers highlights its potential for use in clinical and home-based physical activity assessment.
Regular Article
- Received: July 2, 2025 / Accepted: October 8, 2025
Abstract
For busy individuals seeking to establish an exercise habit, weight-bearing exercise-based high-intensity interval training (HIIT) is a time-efficient option. Although single sessions have been shown to improve postprandial blood glucose, whether unsupervised HIIT supports long-term adherence remains unclear. Therefore, this study compared the effects of eight weeks of supervised HIIT and moderate-intensity continuous training (MICT) on adherence and blood glucose indicators. We recruited 46 healthy young adults with no exercise habits, and low to moderate physical activity. After a two-week pre-measurement period, participants were randomly assigned to a HIIT group that performed weight-bearing exercise-based HIIT three times a week for eight weeks without supervision, an MICT group that performed running three times a week for eight weeks without supervision, or a control group that did not change their lifestyle. The intervention period was followed by a two-week post-measurement period for between-group and pre- and post-intervention comparisons. The primary outcome was exercise adherence, assessed based on a self-report and supplemented with a tri-axial accelerometer and glycemic index. Adherence was significantly higher in the HIIT group (60.6 ± 25.7%) than in the MICT group (27.9 ± 22.3%). No significant differences in glycemic index were observed either pre- to post-intervention or between groups. Overall, unsupervised HIIT produced greater adherence than comparable running but did not alter blood glucose levels in healthy young adults.