Abstract <p> Purpose This study aimed to investigate the validity and reliability of the break-point angle (BPA) and hip flexion angle at the BPA (HFA-BPA) during Nordic hamstring exercise (NHE), as calculated using the Nordic Angle app. Methods Twenty-three male volunteers performed three NHE trials. To verify the validity and reliability of the BPA and HFA-BPA, two-dimensional motion analysis and the Nordic Angle app were used. The validity of the BPA and HFA-BPA in the Nordic Angle application was examined using the Pearson correlation or Spearman’s correlation test test to assess the consistency with the two-dimensional motion analysis data. Intraclass correlation coefficients (ICC) were calculated to assess the reliability of the three NHE trials. Results In the HFA-BPA, the Pearson correlation between the two-dimensional motion analysis and the Nordic Angle app was nearly perfect (r = 0.93, p &lt; 0.01). Similarly, for BPA also the Spearman’s correlation between the two-dimensional motion analysis and the Nordic Angle app was nearly perfect (rs = 0.91, p &lt; 0.01). ICC for the Nordic Angle app in both HFA-BPA and BPA were 0.91 and 0.96, respectively, indicating nearly perfect agreement. Conclusions The Nordic Angle app provides valid and reliable measurements of BPA and HFA-BPA. </p>

【はじめに、目的】

歩行中の前足部への過剰な足底圧は胼胝や中足骨疲労骨折などの原因になるが，歩行のプッシュオフでは前足部母趾側の足底圧はToe-out歩行で増加，Toe-in歩行で減少することが報告されており (石田ら，2022)，足角を操作することで足底圧分布を調整することができる可能性がある．足角には個人差がある一方で，対象の意識や口頭指示により足角を調整して維持することは容易ではないと考える．筆者らは歩行中の腕振りに着目し，足角を変化させる方法を検討することとした．本研究は，腕振りが歩行中の足角に与える影響を調査することを目的とした．

【方法】

健常成人43名 (男性28名，女性15名，計86足)を対象に，50 m の直線上で3条件の腕振りを伴う歩行動作を行った．腕振り条 件は，自然な腕振り (natural，N条件)，肩関節外旋位の腕振り (external rotation，ER条件)，肩関節内旋位の腕振り (internal rotation，IR条件)とした．両足の足角をスマートシューズ (ORPHE CORE 2.0+，ORPHE)で測定した．統計学的解析として，腕振り3条件で足角を比較するために一元配置分散分析を行い，事後検定としてBonferroniの多重比較検定を行った．有意水準は5%とした．

【結果】

腕振り3条件での足角は，N条件で11.8±5.0°に対して，ER条 件で14.4±5.0°，IR条件で12.3±4.9°であった．解析の結果， N条件と比較してER条件で足角が有意に増加した (p<0.05)．

【考察】

ER条件で足角が増加した要因には，肩関節運動から足部にわたって生じる運動連鎖が考えられる．肩関節外旋により肩甲骨が 内転，体幹が伸展，骨盤が後傾することで，大腿骨外旋・下腿外旋が生じ，足角が増加したと推測した．このような全身の運動連鎖に肩関節外旋が影響していることを今回初めて確認した．本研究により，肩関節外旋位の腕振りをすることで足角を増加させることができることを確認した．一方で，IR条件では足角 が変化しなかった．本研究の対象では，自然な歩行でも腕を内旋方向に振る者が圧倒的に多く，N条件とIR条件で動作に差が生じなかったと考えた．IR条件では，腕振りを意識することでかえって足角が増加することを考えた．

【考察・結論】

肩関節外旋位の腕振りをすることで，足角を増加させることが示された．ウォーキングの姿勢やアライメントの指導を行う機会が多いが，このような身体の運動連鎖に注目し，さらなる提案を続けたいと考える．

【倫理的配慮】

本研究は，広島大学疫学研究倫理審査委員会の承認を得て行った (承認番号：E2023-0141)．

OBJECTIVES: Japanese people are known to get the least amount of sleep in the world, and in particular, the increase in sleep deprived young women is a serious problem. Sleep deprivation is considered to be associated with depression, but the factors involved in this problem are unclear. This study aimed to examine the association between sociodemographic factors, lifestyle choices, sleep-related characteristics and depressive symptoms in young Japanese women. DESIGN: Web-based cross-sectional study. PARTICIPANTS: We distributed an online survey aiming to recruit young Japanese women ages 18 to 29 from 8 November 2022 to 2 February 2023. PRIMARY AND SECONDARY OUTCOME MEASURES: Sociodemographic, lifestyle, health, and sleep characteristics were compared among participants according to the presence or absence of depressive symptoms, as assessed by the Patient Health Questionnaire 2 (Cut-off value: 3 points). RESULTS: Overall, 540 participants aged between 19 and 29 years were enrolled in the study. The overall prevalence of depressive symptoms was 15.6%. The group with depressive symptoms had a higher rate of current smoking status at 38.5% (unadjusted OR 3.716, 95% CI 1.624 to 8.502). Multiple logistic analyses revealed that depressive symptoms were associated with increased sleep onset latency (β=0.282; p=0.048; OR, 1.325; 95% CI, 1.003 to 1.752) and daytime dysfunction (β=0.550; p<0.001; OR, 1.733; 95% CI, 1.281 to 2.343) after adjusting for the effects of smoking habits. CONCLUSIONS: Depressive symptoms were found to be associated with sleep disorders in young Japanese women, and paying attention to sleep onset latency and daytime dysfunction which are one of the strongest related factors to depressive symptoms could be a clue to improving sleep disorders and depressive symptoms.

OBJECTIVES: To investigate the relationship between sleep quality and perimenstrual symptoms among Japanese female students. DESIGN: Observational, cross-sectional, online survey SETTING: We used an online questionnaire to collate responses from Japanese female students on sleep quality and perimenstrual symptoms. PARTICIPANTS: A total of 298 female students aged 18-25 years in Japan were included in this study. PRIMARY AND SECONDARY OUTCOME MEASURES: The Menstrual Distress Questionnaire (MDQ) was used to assess the severity of perimenstrual symptoms for three periods-premenstrual, menstrual and postmenstrual-and the Japanese version of the Pittsburgh Sleep Quality Index was used to assess sleep quality. The MDQ scores were compared between two groups (normal-sleep quality and low-sleep quality) using Mann-Whitney U test. In addition, multiple logistic regression analysis was performed, and the MDQ subscales that showed significant differences between the groups were used as independent variables. The MDQ subscale that was strongly associated with sleep quality was calculated. RESULTS: Of the female students, 160 were classified into the normal-sleep quality group and 138 into the low-sleep quality group. The total MDQ scores were significantly higher in the low-sleep quality group at all phases of the menstrual cycle (respectively p<0.05). Among the MDQ subscales, 'pain' during menstruation and 'concentration' in the premenstrual and postmenstrual stages were associated with sleep quality (respectively p<0.05). CONCLUSIONS: Improving sleep quality was one possible strategy to reduce the severity of perimenstrual symptoms. These results may provide useful information for Japanese female students who suffer from perimenstrual symptoms.

Objective: Female athletes are at high risk for lower body ligament injuries, which are likely related to fluctuations in female hormonal balance. One of the most common cases is an injury to the distal tibiofibular ligament while jump landing. This may be related to fluctuations in tibiofibular ligament length and jump landing sway with each menstrual cycle, however, this is still unclear. The purpose of this study was to determine the variation in tibiofibular ligament laxity and dynamic balance during jump landing at each menstrual cycle and to examine the risk of injury occurrence according to the menstrual cycle.

Methods: The participants were seven women. The width of the tibiofibular clear space (TFCS) and dynamic balance were measured at four phases: during menstruation, follicular, ovulation, and luteal. The menstrual cycle was determined using a basal thermometer and ovulation kits. TFCS was measured at the height of the anterior inferior tibiofibular ligament by ultrasonography, and the measurements were conducted in standing and sitting. The dynamic postural stability index (DPSI) was used to assess dynamic balance stability. Participants were asked to jump forward over a 30 cm hurdle. Kruskal Wallis test and Bonferroni correction were performed to compare the measurements for each menstrual cycle.

Result: The width of the TFCS in the standing position was significantly different depending on each menstrual period (p<0.05), and was longer during the ovulation period than other phases of the cycle. DPSI was maximal during the ovulation phase, and showed statistically significant high postural sway (p<0.05).

Conclusion: The previous study reported that an increase in TFCS of only 1 mm can significantly decrease the contact area of the tibiotalar joint, resulting in significant ankle instability. Changes in the length of the fine ankle ligaments due to hormonal fluctuations during each menstrual cycle may affect the landing motion and lead to injury occurrence. This study suggested the need to propose measures to prevent ankle injuries according to female’s menstrual cycles.

BACKGROUND: The reproducibility of dynamic balance is an essential component of athletic performance and injury prevention, although it is affected by sex differences. This study aimed to confirm the reproducibility of repeated dynamic balance measurements and ultrasonography assessments of the anterior tibiofibular gap that may contribute to changes in dynamic balance for each sex. METHODS: This was a longitudinal study involving 48 feet, with 12 men and 12 women. Measurements for men were obtained four times, approximately once a week, and for women, once during each of the four periods of the menstrual cycle (menstrual, follicular, ovulation, and luteal phases). The measures included dynamic balance in a single-leg jump with forward landing and the anterior tibiofibular gap measurement in standing and sitting positions; rate of change in the anterior tibiofibular gap was calculated from the values in standing and sitting positions. RESULTS: The intraclass correlation coefficient for dynamic balance was excellent for men at 0.936 (0.881-0.969) and good for women at 0.843 (0.708-0.925). Regarding the anterior tibiofibular gap, the intraclass correlation coefficient for standing and sitting were 0.999 (0.997-0.999) and 0.998 (0.996-0.999), respectively, in men; and 0.976 (0.955-0.988) and 0.991 (0.984-0.996), respectively, in women, with excellent values for both sexes. Whereas no significant changes in dynamic balance and rate of change in the anterior tibiofibular gap were observed in the four measurements in men (p > 0.05), there was a significant variation in women (p < 0.05). CONCLUSIONS: While reproducibility of dynamic balance and anterior tibiofibular gap measurements was high overall, it was lower in women than in men. Women exhibited variations in these measurements during each period of the menstrual cycle, peaking during ovulation. Recognizing these fluctuations could inform injury prevention strategies tailored to sex-specific differences in dynamic balance and ligament extensibility.

This study aimed to investigate the effects of wearing virtual reality (VR) with a head-mounted display (HMD) on body sway in younger and older adults. A standing posture with eyes open without an HMD constituted the control condition. Wearing an HMD and viewing a 30°-tilt image and a 60°-tilt image in a resting standing position were the experimental conditions. Measurements were made using a force plate. All conditions were performed three times each and included the X-axis trajectory length (mm), Y-axis trajectory length (mm), total trajectory length (mm), trajectory length per unit time (mm/s), outer peripheral area (mm2), and rectangular area (mm2). The results showed a significant interaction between generation and condition in Y-axis trajectory length (mm) and total trajectory length (mm), with an increased body center-of-gravity sway during the viewing of tilted VR images in older adults than in younger adults in both sexes. The results of this study show that body sway can be induced by visual stimulation alone with VR without movement, suggesting the possibility of providing safe and simple balance training to older adults.

OBJECTIVE: In Tokyo 2020 Paralympic Games, there were the rule and goal size changes at the blind football competition. This study aimed to compare the scoring and head impact characteristics during blind football competition between the Rio 2016 and Tokyo 2020 Paralympic Games using the official videos. DESIGN: Video-based observational study. PARTICIPANTS: In total, 36 blind football (men's football 5-a-side) game videos were obtained from the official International Paralympic Committee. PRIMARY AND SECONDARY OUTCOME MEASURES: Head impact was defined as the sudden contact of any object with the head. Videos were analysed to assess the number of scores and head impacts along with their corresponding details (ie, round, playing phase, scoring situation, impact situation, occurrence area, impact object, head impact site, fall and foul). RESULTS: The total number of goals scored at the Tokyo 2020 Paralympic Games was nearly double that at the Rio 2016 Paralympic Games. Regarding head impacts, a total of 2036 cases (Rio 2016, n=1105; Tokyo 2020, n=931) were evaluated. Significant differences were observed in head impact characteristics between the Rio 2016 and Tokyo 2020 Paralympic Games among seven outcomes (round, scoring situation, impact situation, occurrence area, impact object, site of head impact and fall). CONCLUSIONS: Compared with the Rio 2016 Paralympic Games, the Tokyo 2020 Paralympic Games showed an increase in the number of points scored and different head impact characteristics.

BACKGROUND: In response to the serious lack of physical activity among young adults, recent attempts have been made to encourage young people to exercise through exercise video distribution. However, merely distributing videos does not lead to improved physical activity levels. Metaverse space, which enables web-based interaction through avatars, allows users to watch exercise videos in the same space as other avatars. OBJECTIVE: This study explored whether exercise video distribution using metaverse space is effective in improving physical activity levels, along with mental health and locomotive function, among young people. METHODS: In this parallel-group randomized controlled trial participants were recruited using printed poster displays. A total of 48 young adults aged between 18 and 30 years were assigned to 3 groups of 16 each: the metaverse, YouTube, and control group. To encourage exercise, the metaverse group was given an exercise video each week with a load of around 4-8 metabolic equivalents of tasks (METs) for 8 videos delivered in the metaverse space. The YouTube group was sent a URL on YouTube every week to view exercise videos with the same content as the metaverse group. The control group was given no special instructions. The intervention period was 8 weeks. Pre- and postintervention physical activity, well-being, locomotive syndrome risk tests, and social capital were measured. Although this study was not blinded to the participants, the measurers did not know to which group the participants belonged. Mixed model repeated-measures analyses and a post hoc Wilcoxon signed rank sum test were performed to detect the effects of the intervention in all groups. RESULTS: The results of the mixed model repeated-measures analyses showed a significant interaction between groups and before and after the intervention for total physical activity (metaverse group: pre 737.1, SD 609.5 METs/week, post 1575.4, SD 1071.8 METs/week; YouTube group: pre 661.7, SD 710.7 METs/week, post 911.9, SD 1103.3 METs/week; and control group: pre 930.6, SD 665.1 METs/week, post 844.7, SD 701.8 METs/week; P=.04) but none for the indicators of well-being (P=.40), locomotive function scale (P=.17), and social capital (P=.23). A post hoc test showed a significant increase in physical activity in the metaverse group before and after the intervention (P=.006). CONCLUSIONS: This study is the first to show that delivering exercise videos through metaverse space can increase physical activity in young adults by providing a gathering space for individuals similarly motivated for exercise practice. This way, the sense of isolation during exercise is reduced compared with merely distributing videos on YouTube. The use of metaverse space in health promotion is likely to spread, and this study provides a useful reference for its exploration. TRIAL REGISTRATION: ClinicalTrials.gov NCT06019156; https://ichgcp.net/clinical-trials-registry/NCT06019156.

Head impacts during blind football are common and have high injury rates; however, their characteristics and impact are still underreported. We compared head impact characteristics in blind football players with and without falls on all 18 official blind football match videos from the Tokyo 2020 Paralympic games. The rate of head impacts with falls was significantly higher in the preliminary phase, offense phase, and during dribbling. Significant differences in the region of the head impacted were also observed among the impact subjects/objects. The findings in this study would contribute to the development of injury prevention measures to minimize head injuries from head impact in blind football.

OBJECTIVE: The aim of the study is to evaluate the fall characteristics of wheelchair basketball players by sex and impairment classification using the official videos of the Tokyo 2020 Summer Paralympic Games. DESIGN: This was a video-based observational study. In total, 42 men's and 31 women's wheelchair basketball game videos were obtained from the official International Paralympic Committee. The videos were analyzed to assess the number of falls, playing time of the fall, playing phase, contact, foul judgment, fall location/direction, and the body part that first impacted the floor. RESULTS: A total of 1269 falls (men, n = 944; and women, n = 325) occurred. The analysis of men demonstrated significant differences in rounds, playing phase, location of fall, and body part first impacted. Women demonstrated significant differences in all categories except in rounds. Comparisons by functional impairment showed different trends for men and women. CONCLUSIONS: The detailed observation of videos suggested that men are more likely to have dangerous falls. There is a necessity for discuss the prevention measures based on sex and impairment classification.

BACKGROUND: Those undergoing pelvic floor muscle training (PFMT) often experience difficulty in perception; therefore, an easier PFMT method should be devised. OBJECTIVE: To determine the effectiveness of combining PFMT with either vibration stimulation or visual feedback provided by a branded cushion (not a prototype) in increasing PFM muscle activity. Since PFM does not involve large joint movements, muscle activity was a suitable indicator. METHODS: Twenty healthy adults were included in this study. All participants performed PFMT under three conditions using a branded cushion: vibration stimulation, visual feedback, and a control. All three conditions were provided separately. PFM activity of the midline of the perineum at two points was recorded as the root mean square measured using PFM electromyography, measured twice for each condition. Muscle activity ratio was obtained by calculating maximum voluntary contraction of PFM in pre- and post-PFMT conditions. RESULTS: PFM activity and muscle activity ratio were both significantly higher following PFMT under vibration stimulation and visual feedback conditions (p&lt; 0.01, p&lt; 0.01, respectively). CONCLUSIONS: PFMT accompanied by vibration stimulation or visual feedback could immediately raise PFM muscle activity. We believe this study contributes to improving PFMT efficiency by suggesting more suitable PFMT methods.

BACKGROUND: Intrinsic foot muscle exercises are used in clinical and sports practice to improve performance. Force generation during toe flexion is greater in the standing posture than in the sitting posture; nonetheless, the mechanism underlying the activation of intrinsic foot muscles during force generation and whether there exists a difference between these two postures still remain unclear. RESEARCH QUESTION: Are the activities of intrinsic foot muscles affected by standing and sitting postures during gradual force generation? METHODS: Seventeen men participated in the laboratory based cross-sectional study. Each participant performed a force ramp-up toe flexion task from 0% to 80% of the maximal toe flexor strength (MTFS) in sitting and standing postures. High-density surface electromyography signals obtained during the task were determined by calculating the root mean square (RMS). Additionally, modified entropy and coefficient of variation (CoV) were calculated at 20-80 % MTFS for each 10 % MTFS. RESULTS: The RMS between the two postures indicated an interaction effect (p < 0.01). Post-hoc analyses revealed that intrinsic foot muscle activity during the ramp-up task was significantly higher in the standing posture than in the sitting posture at 60 % MTFS (67.53 ± 15.91 vs 54.64 ± 19.28 % maximal voluntary contraction [MVC], p = 0.03), 70 % MTFS (78.11 ± 12.93 vs 63.28 ± 18.65 % MVC, p = 0.01), and 80 % MTFS (81.78 ± 14.07 vs 66.90 ± 20.32 % MVC, p = 0.02). In the standing posture, the modified entropy at 80 % MTFS was lower than that at 20 % MTFS (p = 0.03), and the CoV at 80 % MTFS was higher than that at 20 % MTFS (p = 0.03). SIGNIFICANCE: These results indicated that posture selection is important for high-intensity exercises of the intrinsic foot muscles, such as resistance training. Thus, improving performance related to toe flexor strength might be more effective when conducted under adequate weight-bearing situations, such as in the standing posture.

Wheelchair rugby is a contact sport in which falls are common and injury rates are high, yet the characteristics of the falls are still under-reported. We investigated the fall characteristics of men's wheelchair rugby players by functional classification, using all 36 official match videos from the Rio 2016 and Tokyo 2020 summer Paralympic Games. The videos were analyzed to evaluate the number of falls, playing time when the fall occurred, playing phase (offense or defense), contact with other players, foul judgement, direction of the fall, and the body part first in contact with the floor. All 182 men's wheelchair rugby players (Rio 2016, 94; Tokyo 2020, 88) were classified as low-point players or high-point players depending on their functional classification. A total of 200 falls were detected, 27 (13.5%) for low-point players and 173 (86.5%) for high-point players. Significant differences were noted between low-point players and high-point players in the direction of the fall and body part first in contact with the floor. High-point players had more falls in the forward and left-right directions, whereas low-point players were characterized by a higher percentage of falls in the left-right and backward directions. Additionally, high-point players landed on the floor with their hands with high frequency, whereas low-point players landed with their elbows and shoulders more often. Our findings suggest the significance of devising measures to prevent falls during men's wheelchair rugby games according to their functional classification.

OBJECTIVES: To identify the fall characteristics of athletes in wheelchair rugby and wheelchair basketball during the Tokyo 2020 Paralympic Games and descriptively compare these with those of the Rio 2016 Paralympic Games. DESIGN: Cross-sectional analysis. PRIMARY AND SECONDARY OUTCOME MEASURES: We obtained video footage from the International Paralympic Committee of the Tokyo 2020 Paralympic Games that included 8 teams from each of the 18 wheelchair rugby and 10 wheelchair basketball games (men and women). The data were analysed to evaluate the number of falls, class difference (low or high pointer), time of play during the fall, phase of play, contact with other athletes, fall direction, fall location and the body part that first contacted the floor during the fall. These data from the Rio 2016 and Tokyo 2020 games were compared. RESULTS: Overall, 430 falls (rugby, 104; men's basketball, 230 and women's basketball, 96) occurred (average per game ±SD: 5.8±3.1, 23.0±5.4 and 9.6±5.0, respectively). Significant differences in class, direction, fall location and body part point of contact between the three sports were observed. In wheelchair rugby, falls occurred mainly in high pointers and tended to be more lateral due to contact. In wheelchair basketball, falls occurred more in female high-pointers and in male low pointers, with more forward falls due to forward contact. Unlike in the Rio 2016 games, no difference between the events based on the presence or absence of contact was observed in the Tokyo 2020 games. CONCLUSIONS: The number of falls increased in Tokyo 2020 compared with Rio 2016, with no significant difference in the characteristics of falls between the Rio 2016 and Tokyo 2020 games. Only in men's wheelchair basketball, the number of falls in low pointers significantly increased in the Tokyo 2020 games when compared with that in the Rio 2016 games.

BACKGROUND: Sedentary behavior, particularly prevalent during the 2019 coronavirus disease (COVID-19), has been shown to lead to depression. In medical students, this could negatively affect the provision of healthcare. Thus, this study aimed to investigate the association between sedentary behavior and depression in Japanese medical students during the COVID-19 pandemic. METHODS: An online cross-sectional survey was conducted from July 30 to August 30, 2021, using anonymous questionnaire system to assess respondents' sociodemographic characteristics, physical activity, sedentary behavior among 1000 Japanese university students. Depression was assessed using the Patient Health Questionnaire-2 (PHQ-2). The data of 484 respondents (48.4%) were included in a stepwise analysis, where we set the difference between medical and non-medical students as Model 1 and that between medical students with and without depression as Model 2. For group comparisons of both models, the chi-square test was used for sociodemographic characteristics, and the Mann-Whitney U-test was used for physical activity and sedentary behavior. In Model 2, factors associated with depression among medical students were analyzed by logistic regression analysis. RESULTS: In Model 1, medical students were less physically active (p < 0.001), had longer sedentary time (p < 0.001), and had higher PHQ-2 scores (p = 0.048) than non-medical students. In Model 2, medical students with depression had longer sedentary time (p = 0.004) and longer leisure screen time than those without depression (p = 0.007). Moreover, logistic regression analysis adjusted for potential confounders showed that sedentary time (OR = 1.001, p = 0.048) and leisure screen time (OR = 1.003, p = 0.003) were significantly associated with depression among medical students. CONCLUSIONS: Based on these results, it is evident that reducing Japanese medical students' sedentary time and leisure screen time can help combat depression during the COVID-19 pandemic; thus, these results can guide the development of appropriate interventions to prevent and treat depression.

Vaccinations may be one of the solutions to end the COVID-19 pandemic. One's psychological state may be strongly related to one's willingness to be vaccinated. This study investigated the relationship between the psychological state of Japanese university students and their willingness to be vaccinated. A self-report questionnaire on COVID-19, its vaccines (vaccination status, and perceived efficacy and safety), and psychological state (anxiety and depressive mood) was administered online, and 560 valid responses were obtained. The unvaccinated group reported significantly lower perceived vaccine effectiveness and importance than the vaccinated group. However, there were no differences in anxiety and depressive mood symptoms between the two groups. Multivariate logistic regression analysis was performed on the unvaccinated participants to identify the factors associated with their unwillingness to be vaccinated; there was a significant association between anxiety and unwillingness to receive the vaccine (p < 0.05). However, there was no significant association between depressive mood and unwillingness to receive the vaccine. The results suggest that timely psychological support for Japanese university students experiencing high levels of anxiety is important in accelerating vaccination programs.

BACKGROUND: The human foot has competent mechanisms for supporting weight and adapting movement to various surfaces; in particular, the toe flexor muscles aid in supporting the foot arches and may be important contributors to postural stability. However, the role of intrinsic foot muscle morphology and structure in the postural control system remains unclear, and the relationship between them is not well known. RESEARCH QUESTION: Are intrinsic foot muscle morphology and toe flexor strength related to static and dynamic postural stability in healthy young men?. METHODS: A total of 27 healthy men aged 19-27 years participated in this study. intrinsic foot muscle morphology included muscle hardness and thickness. Cross-sectional area was measured by ultrasonography at an ankle dorsiflexion angle of 0°. The hardness of the abductor hallucis (AbH), flexor hallucis brevis, and flexor digitorum brevis (FDB) muscles was measured using ultrasound real-time tissue elastography. Static postural stability during single-leg standing on a single force platform with closed eyes was assessed for the right leg. In the assessment of dynamic postural stability, the subjects jumped and landed on single-leg onto a force platform and the dynamic postural stability index (DPSI) was measured. RESULTS: FDB muscle thickness showed a positive correlation with anteroposterior stability index (APSI) (r = 0.398, p = 0.040). AbH muscle hardness was negatively correlated with APSI (r = -0.407, p = 0.035); whereas FDB muscle hardness was positively correlated with DPSI (r = 0.534, p = 0.004), vertical stability index (r = 0.545, p = 0.003), and maximum vertical ground reaction force (r = 0.447, p = 0.020). Multiple regression with forced entry revealed that only DPSI was significantly correlated with FDB muscle hardness (p = 0.003). SIGNIFICANCE: The results indicated that intrinsic foot muscle hardness plays an important role in dynamic postural control among healthy young men, which may enable a more rapid muscular response to changes in condition during jump landing and better performance in balance tasks.

The plantar fascia and intrinsic foot muscles (IFM) modulate foot stiffness. However, it is unclear whether the corresponding ultrasonography findings reflect it. This study aimed to examine the effect of the plantar fascia and IFM morphologies on force attenuation during landing and reactivity when jumping in healthy adults (n = 21; age, 21-27 years). Thickness, cross-sectional area (CSA), and hardness of the plantar fascia, abductor hallucis (AbH), and flexor hallucis brevis (FHB) muscles were measured using ultrasonography. Single-leg drop landing and repetitive rebound jumping tests assessed the ground reaction force (GRF) and reactive jump index (RJI), respectively. The CSA of FHB was negatively correlated with maximum vertical GRF (r = -0.472, p = 0.031) in the single-leg drop landing test. The CSA of AbH was negatively correlated with contact time (r = -0.478, p = 0.028), and the plantar fascia thickness was positively correlated with jump height (r = 0.615, p = 0.003) and RJI (r = 0.645, p = 0.002) in the repetitive bound jump test. In multivariate regression analysis, only the plantar fascia thickness was associated with RJI (β = 0.152, 95% confidence interval: 7.219-38.743, p = 0.007). The CSA of FHB may contribute to force attenuation during landing. The thickness of the plantar fascia and CSA of AbH may facilitate jumping high with minimal contact time.

Urinary incontinence (UI) is a major social problem for older adults and leads to a decline in health-related quality of life (HRQoL), mental health, and physical activity. This study assessed the prevalence and symptoms of UI among older adults discharged from the hospital in Japan and investigated the association of UI symptoms with physical activity, HRQoL, and subjective well-being (SWB). By an international consultation, the Incontinence Questionnaire Short Form (ICIQ-SF) that assesses UI severity, was developed. Self-administered questionnaires were used to assess physical activity, HRQoL, SWB, and social demographic characteristics of the participants. In total, 145 participants (valid response rate, 48%; mean age, 78.6 ± 7.6 years) were included in the analysis. Multivariate logistic regression analysis was performed to identify significant factors associated with the presence of UI. Significant decreases in physical activity, HRQoL, and SWB were observed in patients with UI compared with those without UI (p < 0.05). Multivariate analysis revealed that age, number of reported conditions, and decreased SWB were associated with UI (p < 0.05). UI was associated with less physical activity and decreased mental health status in older adults (especially decreased SWB). Health-promoting measures for older adults with UI are essential for maintaining their well-being and extending healthy life expectancy.