The validity and reliability of a Japanese version of the web-based hamstring outcome score.

This study aimed to translate a web-based hamstring outcome score (HaOS) questionnaire to the Japanese context. First, the validity and reliability of the translated questionnaires were examined among Japanese athletes. Second, the association between the previous history of hamstring strain and HaOS was examined. The translation was performed according to internationally recognized methodologies. A total of 233 athletes were asked to complete the HaOS questionnaire, and four questions were added to examine the content validity of the questionnaire. Intraclass correlation coefficient (ICC) was calculated to evaluate the test-retest reliability. Internal consistency was determined by calculating Cronbach's alpha values. The translated questionnaires had high acceptance and compliance rates, with a response rate of 84.4%. The ICC for each scale ranged from 0.80 to 0.93, and Cronbach's α from 0.72 to 0.96, confirming good reliability and high internal consistency. HaOS of the previous injury group (93.4 [78.9, 100]) was significantly lower than that of the healthy group (86.2 [68.1, 100]) (p < 0.05). The translated HaOS questionnaires were valid, reliable, and acceptable for monitoring hamstring conditions in Japanese athletes.

The acute effect of throwing training with virtual reality on boccia competitive performance in healthy adults.

[Purpose] This study aimed to investigate the differences in the acute effects of virtual and actual throwing training on throwing performance. [Participants and Methods] Twenty healthy men and six women with no boccia experience were randomly divided into the virtual and non-virtual groups. The task involved throwing boccia balls at target sets of 2 (short), 5 (middle), and 9 m (long). Both the groups were trained in three rows for each condition. The distance from the ball to the target was calculated as throwing accuracy for both pre- and post-training. Confidence in throwing was measured using a visual analog scale pre-and immediately post-training. A two-way analysis of variance with a post-hoc Bonferroni test or t-test was conducted for throwing accuracy and confidence. [Results] For throwing accuracy, the post hoc test results showed that both groups improved after training, but only in the middle-distance throw. Throwing confidence improved after training in both groups. [Conclusion] Boccia-throwing training using virtual reality may have an acute training effect comparable to that of actual training.

Characteristics of physical activity and sedentary behavior in patients undergoing outpatient cardiac rehabilitation.

Cardiac rehabilitation is crucial for the secondary prevention of cardiovascular disease, the leading cause of death worldwide. In Japan, as hospitalization periods have been shortened due to advances in medical technology and government policies, outpatient rehabilitation focused on lifestyle and physical activity (PA) is becoming increasingly important as hospital stays shorten. This study was aimed to identify patient characteristics that define the different types of PA and sedentary behaviors, and patient factors in 92 Japanese outpatients by using accelerometers. The patients were found to spend considerable time being sedentary (663.7 ± 118.1 min/day) and very little time engaging in moderate-to-vigorous PA (MVPA, 25.6 (10.6-43.4) min/day). Regression analysis revealed that the daily duration of sedentary behavior was 64 min longer in men than in women (ß = 64.2, 95% CI[12.9, 115], p = 0.015); furthermore, men engaged in 22% less light PA (ß = -0.245, 95% CI[-0.388, -0.102], p = 0.001). Additionally, MVPA increased by 43% for every 1 metabolic equivalent (MET) task increase in the anaerobic threshold (AT) (ß = 0.367, 95% CI[0.035, 0.698], p = 0.031) but decreased by 3% per year of age(ß = -0.035, 95% CI[-0.056, -0.015], p < 0.001). The study also found that body mass index (BMI) was negatively correlated with walking time (ß = -0.039, 95% CI[-0.075, -0.003], p = 0.036), while AT was positively correlated with MVPA (ß = 0.367, 95% CI[0.035, 0.698], p = 0.031) but negatively correlated with time above the AT (ß = -2.06, 95% CI[-2.53, -1.59], p < 0.001). These results emphasize the importance of customizing rehabilitation programs according to sex, age, BMI, and AT differences. Furthermore, monitoring home activities and providing individualized prescriptions may enhance the effectiveness of rehabilitation programs.

Effect of ball positions on trunk, hip, knee, and ankle joint kinematics and kinetics during a spike jump in volleyball.

BACKGROUND: Anterior cruciate ligament injuries are serious conditions encountered in volleyball players and occur frequently during spike jump landings. During spike jumps, the lower limb kinematics and kinetics during landing may be altered in relation to the ball position. RESEARCH QUESTION: Does the ball position have an effect on lower-limb kinematics and kinetics during spike jumps? METHODS: We measured the lower limb kinematics and kinetics of 20 healthy female college volleyball athletes during a spike jump using a three-dimensional motion analysis system. The ball positions were set to normal, dominant, and non-dominant positions. A repeated analysis of variance was used to compare the lower limb kinematics and kinetics at the initial contact and the maximum knee flexion during jump landing. Additionally, statistical parametric mapping analysis was used to analyze changes over time during the spike jumps. RESULTS: At the initial contact of the spike jump landing, the knee valgus angle, trunk lateral bending angle, and maximum knee valgus moment when the ball was set at the non-dominant position increased compared to those at the dominant position. Statistical parametric mapping analysis showed no significant change in knee valgus angle and moment of jump landing. CONCLUSION: Knee valgus angle, trunk lateral bending angle, and maximum knee valgus moment increased with the non-dominant position; furthermore, the risk of ACL injury may also be increased. SIGNIFICANCE: The posture at ball impact may influence the landing kinematics and kinetics. Therefore, it is necessary to pay close attention to movements during and prior to landing.

Immediate effect of local vibration on motor unit firing behavior and muscle strength in healthy young adult males.

PURPOSE: The aim of this study was to examine the effect of vibration on motor unit (MU) firing behavior and physical performance of antagonist muscles in healthy young adult males. METHODS: Fourteen males (age = 24.3 ± 3.6 years) were included in this study. There were two conditions, one in which participants received 80 Hz vibration in the distal tendon of the hamstring for 30 s and the control condition (no vibration). High-density surface electromyography (HD-SEMG) signals and maximal voluntary contraction (MVC) of knee extensor muscles were evaluated before and after the respective conditions and recorded from the vastus lateralis muscle during submaximal ramp-up and sustained contractions at 30% MVC. Convolution blind source separation was used to decompose the HD-SEMG signals into individual MU firing behaviors. RESULTS: In total, 739 MUs were detected (control; 360 MUs and vibration; 379 MUs), and a total of 312 matched MUs were identified across both submaximal contraction conditions (control: 150 MUs; vibration: 162 MUs). Vibration significantly increased the discharge rate (p = 0.047) and decreased the recruitment threshold before and after intervention (p = 0.001) but not in the control condition. Furthermore, the recruitment threshold is a factor that influences discharge rate. Significant correlations were observed between the recruitment threshold and both the ∆ discharge rate and the ∆ recruitment threshold under the vibration condition (p < 0.001). CONCLUSION: Vibration increased in the discharge rate and decreased the recruitment threshold of the antagonist muscle. These findings suggested that vibration contributes to immediate changes in the neural control of antagonist muscles.

The vertical mobility of the first tarsometatarsal joint during demi-plié with forced turnout in ballet dancers.

The forced turnout has a perceived risk of development of hallux valgus (HV) in ballet dancers. We determined how the forced turnout affects the sagittal mobility of the first tarsometatarsal (TMT) joint, which is one of the pathogenic factors of HV development. Seventeen female ballet dancers (body mass index: 18.2 ± 1.8 kg/m2) were included and performed demi-plié in control, functional turnout, and forced turnout conditions. Ultrasound imaging synchronized with a three-dimensional motion analysis system was used for measuring the vertical locations of the first metatarsal and medial cuneiform (MC) to evaluate the first TMT joint mobility. Plantar displacement of MC and the first TMT joint mobility in the forced turnout were the greatest among the 3 conditions. Multiple regression analysis indicated that the greater extent of the forcing angle might increase the displacement of MC and the first TMT joint mobility. Evaluating the sagittal mobility of the first TMT joint in the forced turnout can assist in understanding the association between inappropriate techniques including the forced turnout and HV development in ballet dancers. Since the excessive mobility of the first TMT joint is a factor in HV development, the acquirement of adequate active turnout may have the potential to prevent HV development in ballet dancers.

Adaptation of Postural Sway in a Standing Position during Tilted Video Viewing Using Virtual Reality: A Comparison between Younger and Older Adults.

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.

Influence of stimulation frequency on brain-derived neurotrophic factor and cathepsin-B production in healthy young adults.

Electrical muscle stimulation (EMS) has been shown to stimulate the production of myokines (i.e., brain-derived neurotrophic factor (BDNF)), but the most effective EMS parameters for myokine production have not been fully elucidated. The purpose of this study was to quantify the optimal EMS frequency for stimulating myokine production. This study included sixteen young adults (male, n = 13, age = 27.3 ± 5.5 years). Participants underwent four EMS interventions (20 min each) with the following conditions: (1) 4 Hz, (2) 20 Hz, (3) 80 Hz, and (4) control (no intervention). Blood samples were obtained before and immediately after EMS. For the control condition, blood samples were taken before and after 20 min of quiet sitting. BDNF and cathepsin-B levels were analyzed in serum. Compared to preintervention levels, stimulation at 20 Hz resulted in significantly greater postintervention cathepsin-B and BDNF levels (p < 0.01). On the other hand, the control condition did not result in a significant change between pre- and posttreatment. Furthermore, stimulation at 20 Hz caused significantly larger increases in cathepsin-B and BDNF levels than stimulation at 4-80 Hz or the control condition (p < 0.05). In conclusion, stimulation at 20 Hz effectively causes a robust cathepsin-B and BDNF response. Based on these results, we suggest a new strategy for rehabilitation of people with neurological disorders.

Selective Strength Training Changes the Morphology and Ankle Strength of the Peroneus Longus and the Peroneus Brevis.

This study aimed to investigate the 8-week selective training effect of the peroneus longus (PL) and the peroneus brevis (PB) on muscle morphology, echogenicity, and ankle strength and to examine post-intervention detraining effects. Twenty healthy participants without orthopedic disease in the lower extremities were assigned to either the PL intervention group (training consisted of pushing the Thera-Band® out from the ball of the foot to emphasize ankle eversion) or the PB intervention group (training consisted of pulling the Thera-Band® from the base of the fifth metatarsal to enhance ankle valgus and external rotation). Each intervention was performed three times per week for 8 weeks. The cross-sectional area (CSA), thickness, echogenicity, and ankle strength of the PL and the PB were measured before week 1 and after each training session. Detraining effects were evaluated after the 8-week intervention. The results revealed a significant interaction between within-group (week) and between-group (type of intervention) variables on CSA and ankle strength of both the PL and the PB. Over the 8-week training period, the CSA and ankle strength of the PL significantly increased in the PL intervention group, as did the CSA and ankle strength of the PB in the PB intervention group (p < 0.05). The residual effect of muscle hypertrophy was observed during the detraining period. In conclusion, 8-week selective PL and PB training interventions can increase the CSA and ankle strength of these muscles over time. Long-term selective intervention is required to improve peroneus muscle morphology and function, with separate assessments of the CSA and ankle strength of the PL and the PB.

Head impact differences in blind football between Rio 2016 and Tokyo 2020 Paralympic Games: video-based observational study.

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.

First tarsometatarsal joint mobility in hallux valgus during gait: A synchronized ultrasound and three-dimensional motion capture analysis.

PURPOSE: To quantify the vertical translation between the first metatarsal and medial cuneiform during the stance phase of gait in young individuals with and without hallux valgus. DESIGN: This cross-sectional observational study included 34 young adults (male, n = 4; female, n = 30) who were divided into three groups according to the hallux valgus angle: control (< 20°, n = 13), mild hallux valgus (≥ 20° to < 30°, n = 12), and moderate hallux valgus (≥ 30°, n = 9). The mobility of the first tarsometatarsal joint was evaluated during the stance phase using B-mode ultrasound synchronized with a motion analysis system. RESULTS: The medial cuneiform shifted more plantar during the early phase in mild hallux valgus and during the middle and terminal phases in moderate hallux valgus than in control. The severity of the hallux valgus was correlated with a trend toward plantar shift of the medial cuneiform. The first metatarsal was located more dorsal than the medial cuneiform; however, there was no significant variation. No significant differences in the peak ankle plantarflexion angle and moment were noted between the groups. CONCLUSION: The hypermobility of the first tarsometatarsal joint, especially plantar displacement of the medial cuneiform in the sagittal plane, was found in young individuals with hallux valgus during the stance phase of gait, and the mobility increased with the severity of hallux valgus. Our findings suggest the significance of preventing hallux valgus deformity early in life.

Sex differences in laterality of motor unit firing behavior of the first dorsal interosseous muscle in strength-matched healthy young males and females.

PURPOSE: The purpose of this study was to compare laterality in motor unit firing behavior between females and males. METHODS: Twenty-seven subjects (14 females) were recruited for this study. The participants performed ramp up and hold isometric index finger abduction at 10, 30, and 60% of their maximum voluntary contraction (MVC). High-density surface electromyography (HD-sEMG) signals were recorded in the first dorsal interosseous (FDI) muscle and decomposed into individual motor unit (MU) firing behavior using a convolution blind source separation method. RESULTS: In total, 769 MUs were detected (females, n = 318 and males, n = 451). Females had a significantly higher discharge rate than males at each relative torque level (10%: male dominant hand, 13.4 ± 2.7 pps vs. female dominant hand, 16.3 ± 3.4 pps; 30%: male dominant hand, 16.1 ± 3.9 pps vs. female dominant hand, 20.0 ± 5.0 pps; and 60%: male dominant hand, 19.3 ± 3.8 vs. female dominant hand, 25.3 ± 4.8 pps; p < 0.0001). The recruitment threshold was also significantly higher in females than in males at 30 and 60% MVC. Furthermore, males exhibited asymmetrical discharge rates at 30 and 60% MVC and recruitment thresholds at 30 and 60% MVC, whereas no asymmetry was observed in females. CONCLUSION: In the FDI muscle, compared to males, females exhibited different neuromuscular strategies with higher discharge rates and recruitment thresholds and no asymmetrical MU firing behavior. Notably, the findings that sex differences in neuromuscular activity also occur in healthy individuals provide important information for understanding the pathogenesis of various diseases.

A quantitative assessment of the anterior tibiofibular gap with and without weight-bearing in healthy adults: An ultrasound-based study.

BACKGROUND: Difficulties in the accurate evaluation of tibiofibular clear space in plain radiographs are diagnostic problems in the clinical setting of syndesmosis injury. This study aimed to quantify the anterior tibiofibular gap (ATFG) with weight-bearing using ultrasonography. METHODS: In total, 32 healthy adults (16 men and 16 women) with 64 feet participated in this cross-sectional study. The ATFG was measured along the anterior inferior tibiofibular ligament for a US assessment conducted in both sitting and standing postures. The ankle joint was set on the tilt table at four different angles as follows: plantar flexion, 20° (P20); neutral position (N); dorsiflexion, 20° (D20); and dorsiflexion, 20°+ external rotation, 30° (D20ER30). The ankle joint position, sex, and side-to-side values were compared with and without weight-bearing. RESULTS: Under all ankle angle conditions, the ATFG was wider in the standing posture than in the sitting posture (p < 0.001). In both sitting and standing postures, the ATFG widened with increasing dorsiflexion angle, eventually reaching a maximum at D20ER30. The widening ratio (D20ER30/N) in the standing posture was higher in women than in men (p < 0.05). No statistical differences were identified side-to-side differences in the ATFG. CONCLUSIONS: Ultrasound measurements for identifying unphysiological increases in ATFG with weight bearing, especially given the side-to-side differences, may provide a means for quantitatively assessing syndesmosis injury in a clinical setting. Further research is warranted to clarify direct attribution as a clinical diagnostic utility of the ATFG measurements for syndesmosis injuries.

Effectiveness of Metaverse Space-Based Exercise Video Distribution in Young Adults: Randomized Controlled Trial.

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.

Relationship between foot morphologic characteristic and postural control after jump-landing in youth competitive athletes.

BACKGROUND: Foot arch dynamics play an important role in dynamic postural control. Association between foot arch dynamics and postural control among adolescent athletes remains poorly explored. OBJECTIVE: To examine the relationship between foot arch dynamics, intrinsic foot muscle (IFM) morphology, and toe flexor strength and dynamic postural stability after jump landing and repetitive rebound jump performance in competitive adolescent athletes. METHODS: Based on foot arch dynamics, evaluated from relative change in the foot arch height in sitting and standing positions, 50 adolescent athletes were classified as stiff, normal, or flexible. IFM morphology was evaluated by ultrasonography. Dynamic postural stability index (DPSI) was measured as participants jumped and landed with the right leg onto a force plate, whereas repetitive rebound jumping performance was assessed using the jump height and reactive jump index. RESULTS: The stiff group had a significantly worse DPSI and vertical stability index than the normal group (p= 0.26, p= 0.44, respectively), and worse anteroposterior stability index (APSI) values than the flexible group (p= 0.005). Multivariate regression models of the relationship between the APSI and foot arch dynamics showed adequate power (probability of error = 0.912). CONCLUSIONS: Increased foot arch stiffness negatively affects dynamic balance during jump-landing, which may deteriorate their performance.

Relationship of Chronic Ankle Instability With Foot Alignment and Dynamic Postural Stability in Adolescent Competitive Athletes.

Background: Competitive adolescent athletes should be aware of the early signs of chronic ankle instability (CAI) and the connection between the condition and performance. Purpose: To investigate whether CAI is related to foot alignment and morphology as well as dynamic postural stability after a jump landing among adolescent competitive athletes with and without a history of a lateral ankle sprain and CAI. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Between July 2020 and August 2021, adolescent competitive athletes (N = 85; n = 49 boys; n = 36 girls) were classified into 3 groups using Cumberland Ankle Instability Tool (CAIT) scores: healthy athletes (n = 55), coper athletes (n = 19), and athletes with CAI (n = 11). Results of foot alignment assessments involving the leg-heel angle (LHA) and navicular height, intrinsic foot muscle morphology, dynamic postural stability index (DPSI), and other parameters were compared among the 3 groups. The relationship between the CAIT score and the LHA and dynamic postural stability and instability were examined using multiple linear regression. Results: Compared with the healthy group, the CAI group had a significantly greater LHA (8.73°± 3.22° vs 6.09°± 3.26°; P < .05), higher DPSI (0.336 ± 0.046 vs 0.298 ± 0.035), and higher vertical stability index (0.303 ± 0.048 vs 0.264 ± 0.037; P < .05 for all). Multiple regression analysis showed that the LHA (ß = -0.228; P = .033) and DPSI (ß = -0.240; P = .025) were significantly associated with the CAIT score . Conclusion: Valgus rearfoot alignment and poorer dynamic postural control were associated with CAI among adolescent athletes.

Acute Effects of Selective Strength Exercise on the Peroneus Longus and Brevis.

The peroneus muscles are muscles that mainly act in ankle eversion and can be divided into PL and PB, which have different but important roles in foot and ankle functions. Therefore, PL and PB dysfunction can lead to foot and ankle issues, making. selective strength exercise necessary. This study aimed to identify the effect of two different exercise techniques on PL and PB morphologies. Two interventions were performed on separate days: the PL intervention, in which a Thera-Band® was placed on the ball of the foot and pushed out from the contact point, and the PB intervention, in which the Thera-Band® was pulled from the base of the fifth metatarsal. Cross-sectional area (CSA) and thickness of the peroneus muscles at 25% (showing the PL morphology) and 75% (showing the PB morphology) proximal to the line connecting the fibular head and lateral malleolus, as well as ankle strength was measured before and immediately after the interventions and at 10, 20, and 30 min later. A repeated-measures two-way analysis of variance was conducted to identify differences in the effects of the interventions on the PL and PB. Main and interaction effects on CSA, thickness, and ankle strength, with a significant increase in CSA and thickness in the proximal 25% in the PL intervention and the distal 75% in the PB intervention immediately after implementation, were observed (p < 0.05). The transient increase in muscle volume due to edema immediately after exercise indicates the acute effect of exercise. The CSA and thickness of the proximal 25% in the PL intervention and the distal 75% in the PB intervention increased immediately after the intervention, indicating that these interventions can be used to selectively exercise the PL and PB.

The Features of Foot Morphology and Intrinsic Foot Muscle Property in Adolescent Swimmers: An Ultrasound-Based Study.

This cross-sectional study aimed to investigate the relationship between foot shape and intrinsic foot muscles (IFMs) in adolescent swimmers compared with other athletes. Foot morphology of swimmers was compared with other athletes of comparable age and a competition level (n = 32 [64 feet]; a total of 64 feet; 128 feet in two groups). Foot morphology and variables of IFMs were measured using a three-dimensional foot scanner and an ultrasound imaging system, respectively. Multiple linear regression analysis with forced entry was performed to clarify the association of the thickness and the cross-sectional area (CSA) of IMFs with the navicular height in both sitting and standing positions. Navicular height in a standing position, the thickness of the abductor hallucis (AbH) and the flexor digitorum brevis (FDB), as well as the CSA were significantly lower in swimmers compared with other athletes (p < 0.05). A larger CSA for the flexor hallucis brevis (FHB) was observed in swimmers than in other athletes (p < 0.01). The navicular height of swimmers in sitting and standing positions was positively correlated with the thickness and the CSA of the FHB and the FDB (p < 0.05). Multiple regression analysis showed that navicular height was associated with the CSA of the FDB in both sitting and standing positions (ß = 0.395; p < 0.002, ß = 0.201; p < 0.018). This study showed that the navicular height of elite adolescent swimmers was lower than that of other athletes. Furthermore, the swimmers' high navicular height was associated with the CSA of the FDB, suggesting that the FDB might be more involved in the formation of the medial longitudinal arch than the AbH.

Effects of Rearfoot Eversion on Foot Plantar Pressure and Spatiotemporal Gait Parameters in Adolescent Athletes.

BACKGROUND: Foot malalignment can augment the risk of lower-extremity injuries and lead to musculoskeletal disorders. This study aimed to clarify the contribution of rearfoot alignment to plantar pressure distribution and spatiotemporal parameters during gait in healthy adolescent athletes. METHODS: This retrospective study included 39 adolescent athletes who were divided into the rearfoot eversion and control groups according to a leg heel angle of 7°. A total of 78 legs were analyzed (45 and 33 legs in the rearfoot eversion [women, 53.3%] and control groups [women, 48.5%], respectively). Gait was assessed using an in-shoe plantar pressure measuring system and a wearable inertial sensor. RESULTS: The foot plantar pressure distribution in the hallux was higher in the rearfoot eversion group than that in the control group (p = 0.034). Spatiotemporal parameters showed that the foot pitch angle at heel strike was significantly larger in the rearfoot eversion group than that in the control group (24.5° vs. 21.7°; p = 0.015). Total sagittal range of motion of the ankle during the stance phase of gait was significantly larger in the rearfoot eversion group than that in the control group (102.5 ± 7.1° vs. 95.6 ± 15.8°; p = 0.020). Logistic regression analysis revealed that plantar pressure at the hallux and medial heel and foot pitch angle at heel strike were significantly associated with rearfoot eversion. CONCLUSIONS: Our findings suggest that rearfoot eversion affects the gait patterns of adolescent athletes. Notably, leg heel angle assessment, which is a simple and quick procedure, should be considered as an alternative screening tool for estimating plantar pressure and spatiotemporal gait parameters to prevent sports-related and overuse injuries in adolescent athletes.

Differences in Center of Pressure Displacement and Lower Limb Muscle Activity During Relevé Descending Phase Comparing Flat Shoes and Pointe Shoes.

AIMS: In classical ballet, dancers may wear flat shoes and pointe shoes. To consider the kinematic changes between flat shoes and pointe shoes to prevent injuries, it is essential to focus on the fundamental ballet movement of standing on pointe. This study aimed to clarify the differences in the center of pressure (COP) displacement and lower limb muscle activity during the descending phase of a relevé when wearing pointe shoes versus flat shoes. METHODS: Ten amateur ballet dancers volunteered for this study and performed a reléve wearing flat shoes and pointe shoes. We measured the COP displacement by using a footplate and electromyographies of the tibialis anterior, soleus, lateral gastrocnemius, and peroneus longus muscles during the relevé descending phase. These data were compared using a paired t-test or Wilcoxon signed-rank sum test. RESULTS: The COP significantly shifted to the lateral side when dancers were wearing pointe shoes compared to wearing flat shoes (p<0.05). The muscle activity of the tibialis anterior and soleus muscles was significantly higher by 5.7% and 5.3%, respectively, when ballet dancers were wearing pointe shoes compared to flat shoes (p<0.05). However, there were no differences in both lateral gastrocnemius and peroneus longus. CONCLUSION: Greater muscle activities in the tibialis anterior and soleus muscles when wearing pointe shoes than when wearing flat shoes were associated with a larger lateral displacement of the COP. To control the COP displacement during the descending phase of a relevé, the muscle activity of the peroneus longus, which is antagonist of tibialis anterior muscle, and soleus muscles should be increased.