Mihyun Lee

Purpose: Simulating tissue deformation and flow alterations induced by external compression typically requires fluid–structure interaction (FSI) analysis, which is computationally demanding. This study presents a multi-fidelity FSI framework that efficiently captures tissue mechanics and hemodynamic responses to dynamic external pressure and demonstrates its applicability to compression therapy. Methods: We developed an FSI model that couples a one-dimensional deformable blood flow formulation with the three-dimensional (3D) Cauchy equation of motion. Model performance was evaluated by comparing the multi-fidelity and full FSI solutions in simplified cylindrical and subject-specific geometries. As a practical demonstration, the framework was applied to simulate a full-cycle pulsatile intermittent pneumatic compression (IPC) operation. Results: The model efficiently reproduced tissue deformation and hemodynamic changes under external compression, yielding Conclusion: This multi-fidelity FSI framework enables efficient and accurate simulation of tissue deformation and hemodynamic responses under external pressure, providing a tractable platform for large-scale parametric and optimization studies. Its application to IPC highlights potential to enhance therapeutic device design and support broader applications in biomedical modeling and medical device development.

PURPOSE: This study examined the influence of participation in the National Fitness Award (NFA) program on healthcare costs and utilization by analyzing linked data from the NFA database and the National Health Insurance Service (NHIS).METHODS: A total of 721 individuals who participated in the NFA program between 2013 and 2017 and consented to data linkage were included in the study. A control group comprising 1,426 individuals was selected from the NHIS big data through 1:2 propensity score matching based on age, sex, and healthcare utilization in the year before the index date. This study was conducted as part of an official NHIS research project. Changes in healthcare utilization and costs before and after NFA participation were analyzed and compared with the control group to assess the effectiveness of the program.RESULTS: From the year before the intervention to the year following NFA participation, total healthcare costs increased by approximately 70,000 KRW in the participating group and by approximately 470,000 KRW in the control group. After adjusting covariates and applying the difference-in-differences (DiD) methodology, the NFA participants demonstrated the following reductions relative to the control group: 0.1 fewer total number of inpatient visits, approximately 402,000 KRW lower total healthcare costs, 1.9 fewer inpatient visit days, 2.4 fewer inpatient treatment days, and a reduction of approximately 339,000 KRW in inpatient healthcare costs.CONCLUSIONS: The findings suggest that participation in the NFA program was associated with reductions in overall healthcare costs and utilization. These results highlight the effectiveness of fitness programs as a cost-efficient strategy for managing rising healthcare costs.

PURPOSE: This study aimed to assess the validity of a physical activity tracking device by comparing physical activity data from older adults, including the number of steps, energy expenditure, and heart rate (HR), with data obtained from research accelerometers, wearable watches, and mobile apps.METHODS: A total of 24 healthy older adults (aged 65-79 years) wore a wearable tracking device and used a respiratory gas analyzer while walking and running on a treadmill at speeds of 3.8 km/h, 4.8 km/h, 5.6 km/h, 6.4 km/h, and 8.0 km/h, in a randomized order. This study evaluated seven wearable devices: one research accelerometer (ActiGraph GT3X+), five smartwatches/fitness trackers (Samsung Galaxy Watch Active 2, Fitbit Versa 2, Xiaomi Mi Band 4, Garmin Forerunner 945, and Apple Watch Series 2), and one mobile application. Step counts were measured directly, HR was compared using a Polar H7 HR Sensor, and energy expenditure was assessed using a Quarkb2 respiratory gas analyzer.RESULTS: Commercial wearable watches and mobile applications were more accurate than research-grade accelerometers for monitoring steps during walking and running in older adults. HR measurements from wearable watches were more accurate than those from reference devices. Although energy expenditure measurements from mobile applications and wearable watches were less accurate than measurements of steps and HRs their accuracy was comparable to that of research-grade accelerometers.CONCLUSIONS: This study provides insights into the strengths of using wearable devices in healthcare and fitness fields, which seek to monitor and actively manage the physical activity of older adults using wearable trackers.

PURPOSE: The purpose of this study was to develop an estimation equation that predicts energy expenditure (EE) during swimming exercise based on heart rate (HR). And, we also evaluated the validation for field application and compare it with the existing speedbased swimming EE equation.METHODS: A total of 63 healthy adults (ages 19-49 years) who could swim at various speeds were conveniently sampled. The experiment was conducted in an indoor 25 m pool. The protocol (measurement of individual best performance, 0.4, 0.6, 0.8, <1.0 m/s) was performed for 4 minutes each according to the level of the individual. EE was evaluated using a portable respiratory gas analyzer (K4b2, Cosmed, Italy) and a swimming snorkel (Aqua Trainer Snorkel, Cosmed, Italy). HR was measured using a waterproof HR chest strap (Polar Electro Oy, Polar V800, Finland). A dummy control regression analysis was performed with the EE measured by the respiratory gas analyzer as the dependent variables and sex, age, height, weight, and HR during exercise as independent variables.RESULTS: The participants in this study were randomly divided into two groups; the equation development (n=42) and the validation group (n=21). The estimation of EE during swimming exercise is as follows; EEm=-18.197-1.966 (Gender: men=0, women=1)+.027 (Age, year)+.073 (Height, cm)+.008 (Weight, kg)+.092 (HR, bpm) R2=78% (adj. R2=77.2%). The HR-based swimming EE estimation equation (mean=0.7, difference=6.7) verified by the Bland & Altman plot showed the lowest error, followed by Monpetit (mean=1.6, difference=11.6) and Costill (Mean=0.4, difference=16.7).CONCLUSIONS: The EE during swimming was developed using physical characteristics such as sex, age, height, weight and HR in this study. This swimming EE equation might be used for commercial wearable devices.

A well-known functional gastrointestinal disorder called functional dyspepsia (FD) is defined by dyspeptic symptoms without any structural abnormalities. In alternative intervention, electrolyzed alkaline-reduced water (EARW) consumption is regarded as a treatment modality for gastrointestinal symptoms despite its mechanism not yet fully understood. The present clinical study aimed to investigate the effects of EARW on gastrointestinal symptoms of patients with FD. Forty-eight participants with FD were screened, and 42 were enrolled. Participants were randomly allocated to the EARW (n = 21) and purified water (PW) (n = 21) groups. The EARW group ingested EARW (10 mL/kg body weight/day) for 6 weeks. The gastrointestinal symptom rating scale (GSRS), functional dyspepsia-related quality of life (FD-QoL), the Korean version of the Nepean Dyspepsia Index (NDI-K) were used as primary outcome measures at baseline and at 6 weeks, and inflammatory markers were measured as the secondary outcome. Two participants dropped out, and 40 participants (EARW = 20 and PW = 20) completed the trial. Total GSRS score was significantly lower in the EARW group (34.27%, p < 0.01) than in the PW (18.16%) group. In the five subcategories of GSRS, the decreased score between baseline and post-intervention for the EARW and PW groups were 43.59% and 21.33% in abdominal pain score, respectively; 38.98% and 18.92% in reflux syndrome, respectively; 25.42% and 20.90% in diarrhea, respectively; 35.87% and 21.48% in indigestion, respectively; and 32.81% and 10.71% in constipation, respectively, and all the parameters were significantly different in the EARW group compared with those in the PW group. The NDI-K score was also lower in the EARW group (p < 0.01) than in the PW group. FD-QoL score decreased significantly more in the EARW group after intervention than in the PW group (p < 0.05). Additionally, inflammatory cytokines (TNF-α and IFN-γ) levels significantly suppressed in the EARW group after 6 weeks of drinking compared with the levels at the baseline. Our clinical study suggests that long-term drinking of EARW (pH 9.5) may improve FD-related symptoms and the quality of life of FD patients through home-based administration.

PURPOSE: This study aimed to develop age- and sex-specific smoothed percentile curves for fitness items using LMS methods in Koreans aged 13–85 years or older.METHODS: A total of 559,430 individuals aged 13-85 years or older (adolescents: 13-18 years, adults: 19-64 years; older adults: >65 years) participated in the National Fitness Award (NFA) project in 2017, 2018, and 2019 in Korea. In this study, the results of body composition (body fat percent), muscle strength (absolute handgrip strength and relative handgrip strength), and flexibility (sit and reach) tests performed by adolescents, adults, and older adults, were analyzed. Cardiorespiratory fitness (20-m PACER, VO2max) was performed only by adolescents and adults. Percentile curves of fitness items smoothed by age- and sex-specific variables were calculated for fit using the LMS method.RESULTS: Percentile curves for each age- and sex-specific group were presented for each physical fitness component. Percent body fat in men and women increased from the age of 25 and 30 years, respectively. Flexibility showed a tendency to decrease sharply after the age of 65 and 70 years in men and women, respectively. Muscle strength decreased gradually after 40 years, and sharply after 60 years. Cardiorespiratory fitness tended to decrease from the age of 25 years in men and from 19 years in women.CONCLUSIONS: The NFA project dataset provided the opportunity to establish normative values for fitness items in Korean men and women aged 13-85 years or older. The use of the LMS method enabled factoring age in the analysis. Normative reference values of fitness items can be used to interpret individuals’ fitness levels during the everyday practice of fitness and/or in clinical settings.

Regular physical activity confers health benefits and improves the general quality of life. Recently, alkaline-reduced water (ARW) consumption has garnered increasing attention in the field of sports. ARW effectively inhibits the oxidative stress generated in cells during high-intensity exercises; however, whether it exerts similar effects during exhaustive exercises remains unknown. This study was designed as a randomized, controlled, crossover, double-blind clinical trial with a single intervention of ARW intake (pH 9.5, 10 mL/kg body weight) after intense exercise. The participants were divided into two groups, wherein they consumed either purified water (PW group) or ARW (ARW group). Blood samples were collected before exercise, immediately after exercise, and 15 min after drinking water. The serum levels of oxidative stress markers and fatigue markers were determined. The results showed that ROS (p < 0.01) and NO levels (p < 0.001) were significantly decreased after ARW intake, and the reduction was more pronounced than that in the PW group. Interestingly, the increase in GPx and MDA levels was mediated by ARW intake (both p < 0.05) after exercise. The levels of fatigue markers, such as lactate (p < 0.001), lactate dehydrogenase (p < 0.001), and phosphate (p < 0.001), were significantly reduced in both groups, with ARW intervention showing more decreased markers. The correlation analysis results showed that ARW may help maintain homeostatic conditions for ROS, antioxidant systems, and fatigue markers. These findings indicate that ARW consumption is effective in reducing oxidative stress and fatigue following exhaustive exercise and that ARW could be used as an antioxidant and anti-fatigue supplement after exhaustive physical exercise.

PURPOSE: This study examined the accuracy of the heart rate (HR) and energy expenditure (EE) measured by commercially available wearable devices during golf.METHODS: A total of 14 male golfers (24.0±4.06 years) participated in this study. Each participant wore five wearable devices (Apple Watch Series 2, AS; Fitbit Versa, FV; Polar V800, PV; Samsung Galaxy Watch Active, SA; and Suunto Spartan Sport Wrist HR, SWH) on the wrist in the laboratory and/or on a golf course. The criterion measures used to evaluate the accuracy of the HR and EE entailed a wireless heart rate monitor (Polar V800, Polar, Finland) and portable indirect gas analyzer (K4b2, COSMED, Italy). In the laboratory, the participants walked on a treadmill and swung golf clubs using seven iron. On the golf course, the participants played golf in nine holes.RESULTS: In the laboratory, the mean absolute percentage error (MAPE) of the HR in the five wearable devices was within 8% for walking and golf club swinging, excluding FV (12%). The MAPE in EE was within 15% for SA, AS, and PV when walking at a speed of 5.6 km/h on the treadmill, but the MAPE in golf club swinging were within 25%. On the golf courses, the HR in all wearable devices showed the MAPE of <5% but EE showed an error rate of <20%, excluding SWH (73%).CONCLUSIONS: The findings of this study suggest that wearable devices might be used to monitor intensity and amount of exercise during golf.

Electrotherapy is commonly used for myalgia alleviation. Low-frequency stimulation (LFS) is primarily used for controlling acute and chronic pain and is a non-invasive therapy that can be easily performed with electric stimulation applied on the skin. However, little evidence exists regarding the pain alleviation effects of personal low-frequency stimulation device for home use. Moreover, no studies have compared myalgia alleviation effects between personal low-frequency stimulation (PLS) and physical therapy (PT), which are most commonly used for patients with myalgia in hospitals and clinics. Therefore, we aimed to investigate the pain alleviation effects of PLS in patients with myalgia and compare these effects with those of conventional PT (transcutaneous electrical nerve stimulation + ultrasound). In total, 39 patients with myalgia in the neck, shoulder, back, and waist areas were randomly assigned to the personal low-frequency stimulation group (PLSG: n = 20) and physical therapy group (PTG: n = 19). Both groups were treated for 3 weeks (20 min per session and 5 sessions per week). Patients were assessed for pain intensity by surface electromyography (sEMG), visual analogue scale (VAS) and a short-form McGill pain questionnaire (SF-MPQ) before and after the intervention period. Our results showed that PLSG showed a tendency of muscle relaxation with a significant decrease in sEMG in the neck (p = 0.0425), shoulder (p = 0.0425), and back (p = 0.0046) areas compared to the control group. However, there was no significant difference in waist area. Additionally, VAS scores significantly decreased between pre- and post-treatment in both PTG (p = 0.0098), and PLSG (p = 0.0304) groups, but there was no significance difference between the groups. With respect to SF-MPQ, the PLSG showed greater pain alleviation (5.23 ± 0.25) effects than the PTG (6.23 ± 0.25). Accordingly, our results suggest that PLS treatment using a home device might offer positive assistance in pain alleviation for patients with myalgia that is as equally effective as conventional PT treatment. However, further detailed studies are required considering larger samples to fully claim the effectiveness of this device.

Living a healthy lifestyle is the most important need in the world today. However, oxidative stress (OS) is caused by several stress-inducing factors such as smoking, alcohol consumption, chronic diseases, and inflammatory responses, oxygen-free radicals are produced in excess and can damage major organs in the body. This phenomenon has been implicated in the pathogenesis of several gastrointestinal (GI) diseases, including gastritis, constipation, and inflammatory bowel diseases, which include Crohn’s disease, ulcerative colitis, functional dyspepsia, acid reflux, diverticular disease, and irritable bowel syndrome. In this review article, we provide a brief overview of the role of OS in the pathogenesis of GI disorders. Additionally, we discuss the therapeutic role of alkaline-reduced water (ARW) on GI diseases and existing studies on ARW related to GI diseases. Furthermore, we believe that findings from this review article will enhance the knowledge of the readers on the role of ARW on OS and inflammation-based GI diseases.