The Effects of Fatigue on Biomechanics of Soccer Shooting

Soccer is reputedly the most popular sport in the world with over 40 million registered players. Because soccer is a sport that is played mainly with the use of lower extremity, it is important to know about the fatigue in lower extremity and how muscle fatigue affects to the performance such as kicking, shooting, and passing. The purpose of this study was to examine the effects of fatigue on the kinematic changes in the lower extremity in soccer shooting. Six competitive collegiate male soccer players (n = 6) participated in this study (height: 1.76 ± 0.06 m; weight: 71.38 ± 9.55 kg; age: 21.50 ± 3.15 years old). Five joint reflective markers were placed on the right side of the participant at the (sagittal plane) greater tubercle of humerus, greater trochanter of femur, lateral epicondyle of the femur, medial malleolus, and base of fifth metatarsal. Each participant completed a fatigue protocol that was taken 90 seconds. Participants were asked to complete five shooting trials prior to the fatigue protocol as the baseline (Time 0) and then five more times after completion of each fatigue protocol (Time 1-5). A standard two-dimensional kinematic analysis was conducted with a high-speed video camera to capture the kinematic movement in the sagittal view at 120 Hz during soccer shooting performance. The statistical significance of the differences between pre and post fatigue protocol data was conducted with a one-way repeated measure ANOVA (α = 0.05) and followed by t-test with Bonferroni adjustment. Analysis of variance with repeated measures indicated significant decreases (p \u3c 0.05) in ball velocity after time 2 (p = 0.38), time 4 (p = 0.40), and time 5 (p = 0.30). No significant difference was showed on the angular displacement, velocity, and acceleration of the lower extremities. The results of this study showed that fatigue caused ball’s shooting velocity to be significantly lower. Therefore, this study provides a crucial understanding about how exercise-induced fatigue can affect soccer shooting performance. Practitioners can utilize this information and prescribe proper strength and conditioning program to players to maximize their performance. Additionally, soccer coaches can use this information to determine the appropriate timing for player substitution during a game

TILDE-Q: A Transformation Invariant Loss Function for Time-Series Forecasting

Time-series forecasting has caught increasing attention in the AI research field due to its importance in solving real-world problems across different domains, such as energy, weather, traffic, and economy. As shown in various types of data, it has been a must-see issue to deal with drastic changes, temporal patterns, and shapes in sequential data that previous models are weak in prediction. This is because most cases in time-series forecasting aim to minimize $L_p$ norm distances as loss functions, such as mean absolute error (MAE) or mean square error (MSE). These loss functions are vulnerable to not only considering temporal dynamics modeling but also capturing the shape of signals. In addition, these functions often make models misbehave and return uncorrelated results to the original time-series. To become an effective loss function, it has to be invariant to the set of distortions between two time-series data instead of just comparing exact values. In this paper, we propose a novel loss function, called TILDE-Q (Transformation Invariant Loss function with Distance EQuilibrium), that not only considers the distortions in amplitude and phase but also allows models to capture the shape of time-series sequences. In addition, TILDE-Q supports modeling periodic and non-periodic temporal dynamics at the same time. We evaluate the effectiveness of TILDE-Q by conducting extensive experiments with respect to periodic and non-periodic conditions of data, from naive models to state-of-the-art models. The experiment results indicate that the models trained with TILDE-Q outperform those trained with other training metrics (e.g., MSE, dynamic time warping (DTW), temporal distortion index (TDI), and longest common subsequence (LCSS)).Comment: 9 pages paper, 2 pages references, and 7 pages appendix. Submitted as conference paper to ICLR 202

The Effects of Chronic Pain Levels on Lower Extremity Energetics During Jump Landing/Cutting in Chronic Ankle Instability Patients

Up to 75% of patients with lateral ankle sprains develop chronic ankle instability (CAI). A majority of CAI patients report chronic pain and show altered jump landing/cutting patterns. Calculating joint energetics affected by chronic pain provides insight into understanding the effects of chronic pain levels on lower limbs in CAI patients. PURPOSE: To identify the effects of chronic pain levels on lower limb energetics during jump landing/cutting in CAI patients. METHODS: This study was a cross-sectional study. Fifteen CAI patients with high pain (High pain) (6males, 9females; age=22.1±2.1year; height=1.74±0.09m; mass=71.3±10.6kg, pain=66.9±9.4), matched 15 CAI patients with low pain (Low pain) (6males, 9females; age=22.3±2.1year; height=1.74±0.08m; mass=70.1±10.7kg, pain=89.3±2.6), and matched 15 healthy controls (Control) (6males, 9females; age=21.3±1.7year; height=1.73±0.08m; mass=70±10.3kg, pain=100±0). We followed the International Ankle Consortium and utilized the Foot and Ankle Outcome Scores for CAI and chronic pain levels. Ground reaction forces were collected during the jump landing/cutting, while joint power was defined by angular velocity and joint moment data. We calculated ankle, knee, and hip joint energy via the integration of negative (dissipation) or positive (generation) power curve areas. The loading phase was defined by the time from initial contact to 150 ms following, while the cutting phase extended from maximal knee flexion to 150 ms following. The Wilcoxon signed-rank test was used to assess joint energetics data. RESULTS: The high pain showed less energy dissipation and generation in the ankle during the loading and cutting phase than the low pain (p=.013 and p=.002) and control (p=.018 and p=.028). The high pain exhibited more energy generation in the hip during the cutting phase than the low pain (p=.038) and control (p=.013). CONCLUSION: The high pain showed lower energy dissipation and generation in the ankle during the loading and cutting phase than the low pain and control, possibly reflecting an effort to reduce the burden on the ankle joint. The high pain reported more energy generation in the hip during the cutting phase than the low pain and control, suggesting a proximal compensatory strategy. Therefore, chronic pain may impact motor outcomes

Chronic Ankle Instability Subjects Demonstrate Lower Rate of Torque Development in Ankle Eversion, Hip Abduction Muscles Compared to Healthy, Coper Groups

Chronic ankle instability (CAI) is a pathological condition characterized by repeated lateral ankle sprains. Many ankle sprains are not a singular occurrence and can lead to perpetual disability, with some patients reporting repeated episodes of the ankle “giving way” during activity. CAI is multifactorial in nature, with contributors such as ligamentous laxity, strength deficit, and proprioceptive impairment (1). Each of these contributors negatively affects the muscles of the ankle complex. Rate of torque development (RTD) is a metric demonstrating explosive muscle capability, and is related to measurement of maximal voluntary isometric contraction (MVIC). RTD is a more accurate reflection of functional strength than MVIC because peak torque generally occurs 300ms or more after the onset of torque generation (2) while the time available for torque production in a functional daily movement context is generally between 50-250ms (3). RTD is generally measured within the first 200ms of the trial and therefore better captures the muscle’s ability to generate strength for daily activities. Understanding the relationship between RTD of the ankle evertor/invertor muscles and hip abductor muscles in individuals with CAI against healthy controls will better inform rehabilitation strategies and provide a benchmark of improvement for individuals recovering from CAI. PURPOSE: The purpose of this study was to better understand how CAI affects the force production capabilities of the ankle evertors/invertors, as well as the hip abductors. We hypothesized that individuals with CAI would demonstrate lower RTD in all three muscle groups in comparison to healthy and coper controls. METHODS: A total of 58 males and females participated in this study, and participants were divided into three cohorts. The first was a CAI patient group, a “coper” group, defined as individuals who can return to pre-injury levels of performance after LAS, and a healthy control group. CAI individuals and LAS copers were identified using the guidelines provided by the International Ankle Consortium (4). Subject exclusion criteria included previous history of lower extremity surgery, fracture, neurological disease affecting the lower extremity, or any injury to the lower extremity in the 3 months leading up to the study. Before data was obtained participants were familiarized with experimental procedures and protocols. Signed consent was obtained from each subject prior to data collection. The study was approved by the university institutional review board (Approval number: F2019-338). The study design required two visits from the subjects. The first visit was to familiarize subjects with the ankle eversion, inversion, and hip abduction movements they would be required to perform. On this day patients were also made familiar with the Biodex dynamometer (System Pro 4, Biodex Medical Systems, Inc., Shirley, NY; sampling rate: 100 Hz). On the second day subjects were seated on the dynamometer and performed 3 maximal voluntary isometric contractions (MVIC) of each movement. Patients were instructed to perform the movements as quickly as possible and to hold each trial for 5 seconds. Three trials were collected for each movement, with a minute separating each trial. Subjects were encouraged to give maximal effort through verbal cues. RTD and MVIC were calculated from each torque-time curve using custom code written in MatLab (MathWorks 2021a, Natick, MA). RTD was defined as the rate of change of the first 200ms of each trial; MVIC was defined as the peak value of each trial. RTD and MVIC values were averaged for each subject. RESULTS: No statistically significant differences in sex, age, height, or mass were detected among subjects (Table 1). Table 2 shows mean RTD for each group for the ankle eversion, inversion, and hip abduction movements. Notable results from Table 2 include the finding that CAI patients demonstrated significantly lower RTD than healthy controls (p = .02) and lower RTD than LAS copers (p = .03). Furthermore, CAI patients showed lower hip abductor RTD than healthy controls (p = .04). Table 3 shows MVIC data for each group for each movement and demonstrates that CAI patients showed significantly lower MVIC of the ankle eversion muscles than healthy controls (p = .02). No statistically significant differences in any strength metrics were detected between LAS copers and healthy controls, nor were there differences detected between groups in the ankle inversion movement. DISCUSSION: The primary finding from this study was that CAI ankle eversion RTD was significantly lower than RTD in healthy controls. This is significant because it provides insight on the adverse effects of repeated LAS on the muscles of the ankle complex. One of the factors determining RTD is the force transmission capabilities of the tendinous structures (10), and it is possible that the stretching of the ankle ligaments during LAS negatively affects its ability to efficiently transmit force generated from the muscle. Given the correlation between CAI patients and decreased RTD of ankle eversion muscles, it is possible that focusing on improvement in RTD of this muscle group could improve CAI symptoms. Numerous studies have focused on modalities targeted at improving RTD of the leg extensors muscle groups with generally positive results (5, 9), the majority of which include protocols that would be easily modifiable to the ankle eversion muscle group. Another notable finding from this study was that RTD of the hip abductors in the CAI group was significantly less than that of the healthy group. Although studies exist that have measured maximal hip abduction isometric strength in CAI groups, to our knowledge this is the first study analyzing the RTD of hip abduction. Our findings of deficits in hip abduction strength coincide with those of previous studies (6-8). Whether deficits in hip abduction strength increase potential for LAS or arise as a result of CAI is unclear, but it is becoming evident that the two factors are related. This is a promising area of CAI research and further study is required to fully elucidate the relationship between CAI and hip abductor strength. CONCLUSION: RTD of the ankle evertors in individuals with CAI is significantly lower than in LAS copers and healthy controls. Additionally, CAI patients demonstrated significantly lower RTD in hip abduction than healthy controls. While the need for exploring muscle force production capabilities in individuals with CAI persists, we suggest exploring modalities targeted at improving ankle eversion and hip abduction strength in patients with CAI. It is possible that improving strength in these areas will help return CAI patients to pre-injury levels of function and further our understanding of CAI

Socioeconomic Costs of Overactive Bladder and Stress Urinary Incontinence in Korea

Purpose We quantified and described the economic burden of overactive bladder and stress urinary incontinence in Korea. We calculated direct costs by identifying public and private data sources that contain population-based data on resource utilization by patients with stress urinary incontinence and overactive bladder. Methods For estimating indirect costs (productivity loss), the human capital approach was applied. Data were collected from several institutes, including the Health Insurance Review Agency. Results The estimated total economic cost in treating overactive bladder was 117 billion Korean Won (KRW, the currency of South Koea) in 2006 and 145 billion KRW in 2007. The estimated total cost in treating stress urinary incontinence was 122 billion KRW in 2006 and 59 billion KRW in 2007. Conclusions By quantifying the total economic costs of overactive bladder and stress urinary incontinence, this study provides an important perspective in Korea. Because the average age of the Korean population is rapidly increasing, this study provides important information on the direct and indirect costs of overactive bladder and stress urinary incontinence for an aging society

Effects of Anticipation on Energy Dissipation Patterns among Chronic Ankle Instability Patients

Ankle inversion injuries often lead to chronic ankle instability (CAI). CAI patients use altered energy dissipation patterns during jump-landing, but most studies have been limited to tasks performed under anticipated conditions. It is unclear how the anticipatory condition affects joint energetics in CAI patients. PURPOSE: To identify the effects of anticipation on energy dissipation during jump-landing among CAI, coper, and control subjects. METHODS: 60 subjects were categorized according to the Foot and Ankle Ability Measure and Ankle Instability Index. 20 CAI patients (10males, 10females, 1.74±0.1m, 69.1±10.2kg), 20 Copers (10males, 10females, 1.76±0.1m, 70.9±11.1kg), and 20 Controls (10males, 10females, 1.74±0.1m, 66.0±10.7kg) participated. Participants completed 3 trials of maximal jump-landing tasks (via arrows shown on a screen) performed under anticipated/unanticipated conditions. Energy dissipation by the ankle, knee, and hip joints was calculated by integrating regions of the joint power curve during the task. Lower extremity joint energy dissipation was calculated for the hip, knee, and ankle in the sagittal plane during 50, 100, 150, and 200 ms after initial contact with the force plate. Two-way repeated measures ANOVAs (group × condition) were used to examine the differences between condition (Anticipated, Unanticipated) and group (CAI, coper, control). RESULTS: In the unanticipated condition, copers displayed reduced ankle/hip energy dissipation and increased knee energy dissipation compared to the anticipated condition, while the CAI and Control groups demonstrated no change in energy dissipation between the two conditions. CONCLUSION: CAI patients were unable to change energy dissipation patterns between the two conditions. This finding may represent an apprehension for extra ankle strain compared to the copers. In the earliest stages of jump-landing, copers displayed the most altered energy dissipation patterns, shifting from heavily favoring the ankle during anticipated movement to dissipating much more energy into the knee while reducing the load on the ankle. These energy patterns may indicate a coping mechanism and increased knee energy dissipation in copers may be an effort to attenuate load during landing as a strategy to lessen the load absorbed by the ankle

The Effects of Chronic Pain Levels on Lower Extremity Muscle Activation During Jump Landing/Cutting in Individuals with Chronic Ankle Instability

Lateral ankle sprains (LASs) are the most common injury in sports. Up to 74% of individuals with an initial LAS develop chronic ankle instability (CAI) with chronic ankle pain being one of the residual symptoms. PURPOSE: To Identify the effects of chronic pain levels on lower extremity muscle activation during a maximal jump landing/cutting in CAI individuals. METHODS: This study was a cross-sectional study. Twenty CAI individuals with high pain (High pain) (9M, 11F; age=22±2year; height= 1.74±0.10m; mass=79.4±14.6kg, pain=67.4±7.7), 20 CAI individuals with low pain (Low pain) (9M, 11F; age=21±3year; height=1.73±0.08m; mass=74.2±12.7kg, pain=91.7±3.9), and 20 healthy controls (Control) (9M, 11F; age=22±1year; height=1.74±0.09m; mass=68.2±10.2kg, pain=100±0). We followed the International Ankle Consortium and Foot and Ankle Outcome Scores for classification of CAI and chronic pain. Electromyography (EMG) data were collected using wireless surface electrodes (2,000 Hz) during 5 trials of maximal jump landing/cutting from initial contact to toe-off (0-100% of stance). Reference EMG data were collected standing position for 3 seconds. EMG data were normalized to the reference EMG data. The electrodes were placed over the tibialis anterior (TA), peroneus longus (PL), medial gastrocnemius (MG), vastus lateralis (VL), gluteus medius (Gmed), and gluteus maximus (Gmax). Functional analyses of variance were used to evaluate between-group differences for kinematics outcomes. RESULTS: The high pain showed 3.3%, 16%, and 14% less activation in TA, PL, and MG, and 16% and 14% more activation in the VL and Gmed than the low pain. The high pain displayed 26%, 11.1%, 15%, 8.2%, 25.4%, and 11.5% less activation in the TA, PL, MG, VL, Gmed, and Gmax than the control. The low pain showed 14.9%, 18.7%, and 11.2% less activation in the TA, VL, and Gmed, and 8.7% more activation in the PL during the landing/cutting than the control. CONCLUSION: Chronic pain levels appear to impact muscle activation in CAI individuals. Both the high and low pain demonstrate altered muscle activation patterns in distal and proximal joints. The high pain prompts a hip-dominant strategy, compensating for deactivated distal muscles. The lower the level of chronic pain, the more active the PL muscles that contribute to ankle stability

Examining the Acute Effects of Virtual Reality on the Star Excursion Balance Test in Chronic Ankle Instability

Chronic ankle instability (CAI) patients display mechanical and functional restrictions, along with neurocognitive dysfunction after lateral ankle sprains. Athletes need to divide their attention to effectively multitask during sports activities. Recent studies have utilized virtual reality (VR) to simulate dynamic sporting environments, aiming to enhance cognitive and postural control. However, little is known about the acute effects of VR on dynamic postural control in CAI patients. PURPOSE: To identify the acute effects of VR gear on dynamic postural control in CAI patients. METHODS: This study was a cross-over study. Twenty CAI patients (11males, 9females; age=21±3year; height=1.63±0.28m; mass=74±13.1kg). We used the Foot and Ankle Ability Measures and Ankle Instability Instrument questionnaires for CAI. VR training included 3 trials of single-leg stance; double and single-leg drop landings; and 5 trials of jump landing/cutting. Before and after VR training, participants performed 3 trials each in 3 directions: anterior (ANT), posteromedial (PM), and posterolateral (PL). The average reach distance was normalized by an individual’s leg length from the anterior superior iliac spine to the distal end of the medial malleolus. Matched paired t-tests were used to evaluate the acute effect (posttest-pretest difference) of VR training. The significance level for all analyses was set at a priori of p≤0.05. RESULTS: Acute effects were not observed in both ANT and PM directions (60.2±7.2 vs. 60.9±6.9, p=0.15 and 103.3±10.4 vs. 104.6±11.2, p=0.31). CAI patients showed an acute effect, improving PL reach distance (98.3±11.2 vs. 102.1±13.3, p=0.006) during the star excursion balance test after VR training. CONCLUSION: VR resulted in no difference in ANT direction, which is related to the dorsiflexion range of motion, suggesting that VR training had no improvement in mechanical restriction. After VR training, PL reach distance was increased, suggesting improvement in functional restriction in CAI patients. Therefore, VR training may affect functional restriction, by potentially increasing eversion strength and improving mediolateral static postural control. More data are needed to determine if VR may reduce the risk of recurrent ankle sprains in CAI patients

The Effects of Chronic Pain Levels on Joint Angle During Jump Landing/Cutting in Individuals with Chronic Ankle Instability

About 60% of chronic ankle instability (CAI) individuals report ankle pain persisting for longer than 3 months. They have the risk of recurrent ankle sprains while performing multiplanar tasks such as jumping with landing/cutting. However, little is known about the effects of chronic pain levels on joint kinematics differences and how chronic pain levels contribute to motor outcomes when performing multiplanar motions. PURPOSE: To identify the effects of pain levels on kinematics during jump landing/cutting in CAI individuals. METHODS: This study was a cross-sectional study. Twenty CAI patients with high pain (high pain) (9 males, 11 females; age=22±2year; height=1.74±0.10m; mass=79.4±14.6kg, pain=67.4±7.7), 20 CAI patients with low pain (low pain) (9 males, 11 females; age=21±3year; height=1.73±0.08m; mass=74.2±12.7kg, pain=91.7±3.9), and 20 healthy controls (9 males, 11 females; age=22±1year; height=1.74±0.09m; mass=68.2±10.2kg, pain=100±0). We followed the International Ankle Consortium criteria for classifying CAI and utilized the Foot and Ankle Outcome Scores for chronic pain levels. We used 44 reflective markers to calculate joint angles collected during the jump landing/cutting task from initial contact to toe-off (0-100% of stance). Functional analyses of variance were used to evaluate between-group differences for kinematics outcomes. RESULTS: The high pain showed 4.8° less plantarflexion from 0-12% than the low pain from 0-8% and 4.9° less plantarflexion than the healthy control. The high pain exhibited 1.4° less inversion from 8-12% than the low pain. The knee joint presented 1.5° less flexion from 0-5% and then 4.4° more flexion at 10-24% than healthy controls, showing a greater knee joint angle variability. The high pain showed 5.3°, 3.6°, and 3.5° higher hip flexion from 2-24%, 50-61%, and 75-82%, respectively than the healthy control. CONCLUSION: The high pain demonstrated less plantarflexion and inversion in the ankle while exhibiting more kinematics variance in the knee joint and hip during multiplanar tasks. These findings may result in a stiffer landing in the ankle and proximal landing strategy during jump landing/cutting tasks. Thus, chronic pain levels affect joint kinematics during multiplanar tasks