PURPOSE: This study aimed to investigate whether PM2.5 exposure further increases mitochondrial dysfunction and structural damage in skeletal muscle under type 2 diabetes.METHODS: Type 2 diabetic mice (DM) were generated by feeding a high-fat diet to a polygenic diabetic mouse model (NSY x C57BL/6). Mice were divided into four groups: Wild-type mice exposed to filtered air (WT-CON), WT mice exposed to PM2.5 (WTPM2.5), DM exposed to filtered air (DM-CON), and DM exposed to PM2.5 (DM-PM2.5). PM2.5 (52.7±8.9 μg/m3) was administered for 2 h/day for 5 days a week, followed by a 4-week recovery period. Skeletal muscle samples were analyzed for glucose metabolism, mitochondrial biogenesis protein expression, and mitochondrial morphology by ttechnical error of measurement (TEM).RESULTS: PM2.5 exposure significantly increased GLUT-4 expression in DM, whereas glycolytic enzymes (HXK-2, PFK-1, and LDH) remained unchanged. PGC-1α–Tfam signaling was partially activated, accompanied by elevated COX-1 expression, suggesting compensatory mitochondrial biogenesis. However, concurrent upregulation of PINK1, Parkin, Bax, and Bcl-2 revealed sustained mitochondrial stress and incomplete recovery. TEM analysis confirmed severe mitochondrial morphological damage, including cristae disruption and matrix swelling, in the DM+PM2.5 group.CONCLUSIONS: PM2.5 exposure further exacerbates the imbalance in energy metabolism and mitochondrial damage in skeletal muscle under type 2 diabetes conditions.
Background Stroke is a disease influenced by various risk factors, including genetic factors determined by single nucleotide polymorphisms (SNPs). Polygenic risk score (PRS) calculated from multiple SNPs can reflect the varying genetic risk of stroke. Physical activity is a critical factor that influences the incidence of stroke by improving other risk factors. Therefore, we investigated the effects of physical activity on the reduction of stroke incidence across different PRS levels. Methods This study utilized epidemiological and genetic data from Korean Genome and Epidemiology Study. Through genome wide-associated study (GWAS) analysis, SNPs with high frequency in stroke patients were classified. The presence and amount of physical activity was assessed based on the weekly average exercise reported in the epidemiological survey data. All participants were classified into three groups based on PRS levels. Results Through GWAS (p < 1×10-5), 28 SNPs were identified in the stroke patients for calculating PRS. The physical activity significantly reduced stroke incidence with high (p < 0.0001) and middle PRS levels (p < 0.0001). Notably, the amount of physical activity showed a difference in stroke incidence with high (p < 0.0001) and middle PRS levels (p = 0.0002). Conclusions This study investigates differences in stroke incidence due to physical activity across PRS levels calculated from stroke-related SNPs in GWAS. The reduction in stroke incidence influenced with the physical activity varied depending on PRS levels. Our findings suggest that the stroke prevention effect of physical activity may differ across PRS levels.
PURPOSE Resistance arteries rely on tightly coordinated signaling between vascular smooth muscle cells (SMCs) and endothelial cells (ECs) to regulate vascular tone and ensure appropriate tissue perfusion. Myoendothelial feedback via gap junctions is crucial in limiting excessive vasoconstriction triggered by myogenic and sympathetic stimuli. This review synthesizes current knowledge on second messenger-dependent SMC-to-EC communication and explores how exercise training modulates these heterocellular signaling pathways to influence myoendothelial feedback. METHODS Relevant literature was systematically retrieved from major scientific databases (e.g., PubMed and Web of Science), with a primary focus on studies examining vascular myoendothelial feedback regulation and the effect of exercise training on SMC-EC heterocellular communication. RESULTS SMC activation by adrenergic or purinergic stimuli generates intracellular Ca2+ and IP3 signals that are transmitted to adjacent ECs via myoendothelial gap junctions. These signals elicit localized endothelial Ca2+ events, stimulate nitric oxide production, activate endothelial IKCa and SKCa channels, and induce endothelium-dependent hyperpolarization, collectively suppressing SMC contraction. Ca2+ diffusion and IP3 transfer contribute to this negative feedback, with growing evidence supporting C2+/IP3-dependent signaling as a dominant mechanism during physiological sympathetic activation. Exercise training enhances endothelial C2+ signaling capacity, improves gap junctional communication, and augments downstream vasodilatory responses. CONCLUSIONS Myoendothelial feedback represents a critical protective mechanism against excessive vasoconstriction in resistance arteries. Exercise training reinforces this negative feedback by strengthening endothelial signaling and heterocellular communication, thereby promoting vascular homeostasis during physiological stress.
PURPOSE This study aimed to compare the effects of intermittent fasting (IF) and swimming exercise (SE) on metabolic markers and white adipose tissue (WAT) browning in high-fat diet (HFD)-induced obese mice. METHODS Forty male C57BL/6J mice (six weeks old) were randomly assigned to four groups: normal chow diet (CON), high-fat diet (HFD), HFD with intermittent fasting (HFD+IF), and HFD with swimming exercise (HFD+SE). The IF protocol consisted of a 48-h feeding and 24-h fasting cycle, while SE was performed for 90 minutes per day, five days per week, at 32±1°C for eight weeks. Body weight, glucose, triglycerides, serum insulin, and HOMA-IR were analyzed. The protein expression of AMPK, PGC-1α, and UCP1 in skeletal muscle and subcutaneous WAT was evaluated using Western blotting. RESULTS After eight weeks, the HFD group showed significant increases in body weight, triglycerides, and HOMA-IR compared with the CON group (p<.05). Both IF and SE interventions partially ameliorated these metabolic impairments. IF significantly increased AMPK expression in the gastrocnemius muscle and UCP1 in subcutaneous WAT, whereas SE significantly elevated PGC-1α expression in skeletal muscle. CONCLUSIONS These findings suggest that IF improves metabolic health primarily through activation of the AMPK–UCP1 signaling pathway, while SE promotes mitochondrial biogenesis via PGC-1α upregulation. Both interventions exert anti-obesity effects through distinct molecular mechanisms, and their combination may offer a synergistic strategy for preventing obesity-related metabolic disorders.
PURPOSE This study aimed to examine the associations among forward head posture (FHP), physical activity (PA) level, and neck function indicators in undergraduate and graduate students. METHODS A total of 102 undergraduate and graduate students were included. PA level was assessed using the International Physical Activity Questionnaire-Short Form. Cervical sagittal alignment was evaluated using the craniovertebral angle (CVA), and neck function indicators included cervical range of motion (ROM), joint position error (JPE), neck muscle strength, and neck muscle endurance. RESULTS Between-group comparisons indicated that the PA-sufficient group exhibited significantly greater CVA, neck flexor strength (NFS), neck extensor strength (NES), and neck flexor endurance (NFE) than the PA-insufficient group. Correlation analysis showed that CVA was significantly associated with PA level, cervical ROM, and JPE. Stepwise regression analysis indicated that cervical flexion and extension ROM, as well as JPE during extension and left and right rotation, were significantly associated with CVA. CONCLUSIONS These findings suggest that physical activity level may be associated with cervical alignment and neck muscle function in this population. In addition, cervical range of motion and joint position error may represent relevant functional characteristics related to forward head posture and should be considered in its evaluation.
PURPOSE This study aimed to investigate whether PM2.5 exposure further increases mitochondrial dysfunction and structural damage in skeletal muscle under type 2 diabetes. METHODS Type 2 diabetic mice (DM) were generated by feeding a high-fat diet to a polygenic diabetic mouse model (NSY× C57BL/6). Mice were divided into four groups: Wild-type mice exposed to filtered air (WT-CON), WT mice exposed to PM2.5 (WT-PM2.5), DM exposed to filtered air (DM-CON), and DM exposed to PM2.5 (DM-PM2.5). PM2.5 (52.7±8.9 μg/m³) was administered for 2 h/day for 5 days a week, followed by a 4-week recovery period. Skeletal muscle samples were analyzed for glucose metabolism, mitochondrial biogenesis protein expression, and mitochondrial morphology by ttechnical error of measurement (TEM). RESULTS PM2.5 exposure significantly increased GLUT-4 expression in DM, whereas glycolytic enzymes (HXK-2, PFK-1, and LDH) remained unchanged. PGC-1α–Tfam signaling was partially activated, accompanied by elevated COX-1 expression, suggesting compensatory mitochondrial biogenesis. However, concurrent upregulation of PINK1, Parkin, Bax, and Bcl-2 revealed sustained mitochondrial stress and incomplete recovery. TEM analysis confirmed severe mitochondrial morphological damage, including cristae disruption and matrix swelling, in the DM+PM2.5 group. CONCLUSIONS PM2.5 exposure further exacerbates the imbalance in energy metabolism and mitochondrial damage in skeletal muscle under type 2 diabetes conditions.
PURPOSE Pooled reference data for Korean adults are limited, and Western norms may not be applicable because of ethnic differences. This study aimed to describe sex- and age-specific distributions of knee isokinetic peak torque normalized to body weight in healthy Korean adults. METHODS Following PRISMA guidelines, PubMed, Web of Science, Google Scholar, RISS, and KISS were searched for articles published between 1990 and 2023 using combinations of the terms “isokinetic,” “muscle strength,” “muscle function,” and “Korean.” Studies were eligible if they assessed knee isokinetic strength in healthy Korean adults using Cybex or HUMAC NORM. Weighted means and 95% confidence intervals (CI) for peak torque at 60˚/s (% body weight [BW]) were calculated based on sample size. RESULTS Thirteen studies (n=426; 245 men, 181 women) were included. In men, left knee extensor peak torque decreased from 267.5 %BW (95% CI 260.7–274.3) in those aged 20–29 years to 143.3 %BW (130.6–155.9) in those aged >60 years. In women, left knee extensor peak torque declined from 227.3 %BW (211.6–242.9) in adults aged 20–29 years to 86.7 %BW (78.7–94.6) in those aged >60 years. Flexor strength showed similar age-related declines, and men consistently exhibited higher peak torque than women. CONCLUSIONS This study provides the first combined descriptive estimates for knee isokinetic strength in Korean adults. These values may serve as preliminary reference information for clinical assessment and exercise prescription. Results should be interpreted with caution owing to limited sample sizes in some subgroups. Large, standardized, population-based studies are needed to refine these reference standards.
PURPOSE This study aimed to compare the effects of six weeks of Repeated Sprint Training (RST) and Speed Endurance Training (SET) on physical fitness and match performance in university soccer players during the competitive season. METHODS Sixteen male university soccer players were randomly assigned to either the RST (n=8) or SET group (n=8) based on their match playing time prior to the intervention. Both groups completed two training sessions per week for six weeks with an identical distance per session (160 m). Physical fitness assessments included the 40-meter sprint test, Repeated Sprint Ability (RSA) test, Yo-Yo Intermittent Recovery Test Level 2 (YYIRT-L2), and Wingate anaerobic test. Match performance variables, such as total distance, high-intensity running, sprint distance, and acceleration/deceleration metrics, were evaluated using GPS tracking data over three consecutive official matches before and after the intervention. RESULTS Both the RST and SET groups showed significant improvements in YYIRT-L2 total distance (p<.001). The SET group demonstrated a significant improvement in anaerobic performance with enhanced peak and average power outputs in the Wingate test and faster 20-meter sprint times. However, match performance analysis revealed that high-intensity running distance (Zone 4) per minute significantly decreased in the SET group (p<.05) but was maintained in the RST group. No significant changes were observed in total distance per minute or maximal sprint speed in either group. CONCLUSIONS Both RST and SET interventions effectively improved aerobic and anaerobic fitness during the season. Given the small sample size and lack of significant interaction effects, these preliminary findings suggest that RST may help preserve high-intensity running performance during matches, whereas SET was associated with greater improvements of anaerobic performance and RSA. Further research with larger samples is needed to confirm these trends.
PURPOSE This study examines whether handgrip strength (absolute handgrip strength [AHGS] or relative to body weight handgrip strength [RHGS]) and total and lower-body fat-free mass (FFM) are associated with the prevalence of diabetes mellitus (DM) and compares the relative explanatory value of these indices overall and by sex. METHODS We analyzed 4,767 adults (men: 2,319; women: 2,448) from the 2022-2023 Korea National Health and Nutrition Examination Survey. AHGS was the maximum value from four trials; RHGS was AHGS divided by body weight. Total and lower-body FFM were obtained via bioelectrical impedance analysis (InBody 970). DM was defined as fasting glucose ≥126 mg/dL, HbA1c ≥6.5%, or physician diagnosis/treatment. Each exposure was categorized into sex-specific tertiles. Logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS Model 1 was adjusted for sex, age, height, education, income, marital status, and occupation; Model 2 was additionally adjusted for smoking status, alcohol consumption, and weekly physical activity. Compared with the lowest RHGS tertile (T1: ≤42.66%), the highest tertile (T3: ≥53.27%) showed 61% lower odds of DM (95% CI: 0.28-0.53). For lower-body FFM, T3 (≥15.32 kg) versus T1 (≤12.10 kg) was associated with 43% lower odds (95% CI: 0.33-0.99). Among men, participants in the highest RHGS tertile (T3: ≥59.63%) had 58% lower odds of DM compared with those in the lowest tertile (T1: ≤50.77%) (95% CI: 0.30-0.59). Among women, the highest RHGS tertile (T3: ≥45.65%) was associated with 45% lower odds compared with the lowest tertile (T1: ≤38.34%) (95% CI: 0.37-0.82), and the highest lower-body FFM tertile (T3: ≥12.30 kg) was associated with 64% lower odds compared with the lowest tertile (T1: ≤10.87 kg) (95% CI: 0.18-0.70). CONCLUSIONS RHGS and lower-body FFM showed more consistent associations with lower odds of DM than AHGS and total FFM.
Regular physical exercise promotes beneficial adaptations across multiple organ systems. However, when training loads chronically exceed recovery capacity (here defined as overtraining) the same molecular pathways mediating these adaptations become systemically dysregulated. This minireview adopts an integrative perspective to synthesize evidence on inter-organ communication disrupted by overtraining, focusing on three interconnected axes: muscle–brain, gut–microbiota–brain, and muscle–liver. Along the muscle–brain axis, systemic inflammation can compromise blood-brain barrier integrity and favors kynurenine accumulation in the central nervous system, generating oxidative stress and excitotoxicity. Muscle-derived mitochondrial vesicles also disrupt hippocampal mitochondrial dynamics, impairing synaptic energy metabolism. Along the gut–microbiota–brain axis, splanchnic hypoperfusion and dysbiosis can compromise intestinal barrier integrity, promoting endotoxemia and neuroinflammation, while converging on the kynurenine pathway overactivation. Along the muscle–liver axis, lactate-driven extracellular vesicles induce hepatocyte apoptosis and activate stellate cells, promoting liver fibrosis. Collectively, overtraining is characterized by recurrent molecular signatures, including systemic inflammation, lactate-driven signaling, and kynurenine pathway dysregulation, with the hippocampus emerging as a particularly vulnerable target. Integrative multi-omic approaches will be essential for developing reliable diagnostic tools and evidence-based training guidelines.
PURPOSE Asymmetrical fencing movements demand exceptional dynamic balance and lower limb strength. This study investigated whether a 12-week supplementary Pilates program could enhance these key performance determinants in elite fencers by testing its efficacy as a targeted intervention for specific biomechanical needs. METHODS Twenty-five elite male fencers were randomly assigned to 2 groups for 12 weeks: fencing-only training (FT [n=12]); or fencing–Pilates (FPT [n=13]). Dynamic balance (Y-Balance Test) and lower limb isometric strength were measured (handheld dynamometry) pre- and post-intervention to assess changes. RESULTS After the intervention, the FPT group exhibited significant improvements (p<.05) in all 3 directions of dynamic balance and in the strength of all measured lower limb muscles; the FT group exhibited no significant changes in dynamic balance. Furthermore, quadriceps femoris strength gains were significantly correlated (p<.05) with dynamic balance improvements, indicating a strong mechanistic link. CONCLUSIONS The 12-week Pilates intervention effectively improved both dynamic balance and lower limb strength in elite fencers. Findings revealed that strength gains, particularly in the quadriceps, were a key mechanism driving enhanced dynamic stability. Therefore, Pilates serves as a targeted, evidence-based training modality to optimize fencing performance by addressing the specific functional and biomechanical demands of the sport.
PURPOSE To investigate the effects of integrating diaphragmatic breathing (DB) with dynamic neuromuscular stabilization (DNS) exercises on respiratory function, gait parameters, and physical self-esteem in middle-age women with abdominal obesity. METHODS Using a single-blind design, 36 middle-age women ≥50 years of age with abdominal obesity were randomly assigned to db and ndb group. Both groups participated in a six-week DNS exercise program conducted in one-on-one sessions twice per week, each lasting 50 min. Respiratory function (peak expiratory flow [PEF], forced vial capacity [FVC], forced expiratory volume [FEV1]), and gait parameters, and body self-esteem were measured before and after the intervention to analyze changes. Statistical analyses were performed using IBM SPSS Statistics version 29.0 (IBM Corp., Armonk, NY, USA), using descriptive statistics and nonparametric tests at a significance level of 0.05. RESULTS The experimental group exhibited significantly greater improvements in all respiratory function indicators (i.e., PEF, FVC, and FEV1) and physical self-esteem than those the control group. They also exhibited significantly greater reductions in forward head posture and trunk leaning angles during gait, indicating improved postural alignment. While both groups exhibited significant reductions in horizontal center-of-gravity movement and step width, the intergroup differences were not significant. Stride length was significantly increased in the experimental group but remained unchanged in the control group. The increase in the left-stride length was significantly greater in the experimental group than that of the control group, although right-stride length exhibited no significant intergroup differences. CONCLUSIONS The study results emphasize the effectiveness of focusing on breathing stabilization during exercise. Applying DNS diaphragmatic breathing feedback to DNS exercises demonstrated synergistic effects on respiratory function, gait parameters, and selfesteem in middle-aged women with abdominal problems.
Resistance exercise (RE) is a potent hypertrophic stimulus for skeletal muscle but simultaneously imposes mechanical strain that induces focal microdamage within the sarcomeric force-transmission network. This review synthesizes evidence describing how early, damage-driven cytoskeletal repair responses establish the structural basis for effective hypertrophic remodeling in repeatedly RE-stimulated human skeletal muscle. We integrate literature at the intersection of muscle damage, proteostatic regulation, and human adaptation to RE, highlighting molecular damage control as a central yet underappreciated component of resistance training adaptation. Particular emphasis is placed on chaperone-assisted selective autophagy (CASA) and the small heat shock protein αB-crystallin (CRYAB), key regulators of proteostasis in mechanically stressed muscle. We outline mechanisms governing muscle anabolism and catabolism, the structural localization of RE-induced microdamage, and acute mechanoprotective programs involving CASA and small heat shock proteins. We propose that microlesions function as focal signaling hubs linking mechanical strain to transcriptional control via a CRYAB– SMAD4 axis. Following intense or unfamiliar RE, rapid CRYAB phosphorylation stabilizes strained cytoskeletal proteins and supports BAG3-dependent turnover, while spatial mTORC1 modulation enables localized autophagy alongside preserved protein synthesis. With repeated training, cytoskeletal reinforcement reduces lesion burden and shifts remodeling toward net myofibrillar accretion, informing mechanistically grounded RE program design.
PURPOSE This study aimed to analyze the associations among insulin resistance (IR), type 2 diabetes mellitus (T2DM), physical activity, and knee osteoarthritis (KOA) in older women. METHODS A total of 2,217 women aged ≥65 years who participated in the Korea National Health and Nutrition Examination Survey (2009–2013) were included. IR was assessed using the triglyceride-glucose body mass index, and participants were classified as normal or abnormal based on cutoffs. T2DM was defined as having a fasting glucose level >126 mg/dL, a physician-diagnosed diabetes history, or current treatment for diabetes. Physical activity was assessed using the International Physical Activity Questionnaire and categorized by whether participants engaged in ≥150 min/week of light-intensity physical activity (LPA) or moderate-to-vigorous physical activity (MVPA). KOA was defined as Kellgren-Lawrence (KL) grade ≥2, and categorized as follows: KL 0–1=normal, KL 2=light KOA, KL 3–4=moderate-to-severe KOA. RESULTS Logistic regression showed significantly higher KOA risk in the abnormal IR group (OR=1.768, 95% CI=1.486–2.105) and T2DM group (OR=1.311, 95% CI=1.054–1.631) compared to the normal group. Participants with <150 min/week of LPA had higher KOA risk (OR=1.378, 95% CI=1.158–1.639) than those with ≥150 min/week. In the IR and T2DM groups, participants engaging in <150 min/week of LPA had significantly higher odds of moderate-to-severe KOA compared to those with ≥150 min/week. CONCLUSIONS Engaging in >150 min/week of LPA may be a practical and effective strategy for the prevention of KOA in older women with impaired glucose metabolism.
PURPOSE Metabolic syndrome (MS) is a major precursor to type 2 diabetes and cardiovascular disease. Conventional glycemic markers such as fasting glucose and HbA1c do not capture dynamic glucose fluctuations. This review examines the metabolic risks associated with glycemic variability (GV) in adults with MS and explores the potential of breaking up prolonged sitting and the soleus push-up (SPU). METHODS A narrative review was conducted using Web of Science, PubMed, and Google Scholar for literature published from January 2000 and August 2025. Search terms included “glycemic variability,” “metabolic syndrome,” “breaking up prolonged sitting,” “continuous glucose monitoring (CGM),” and “SPU.” Evidence regarding GV was limited to studies involving MS, while studies in broader populations included to contextualize mechanisms of sedentary interruption strategies. RESULTS GV is independently linked to oxidative stress, endothelial dysfunction, and inflammation, contributing to elevated diabetes and cardiovascular risks in MS. CGM studies generally report higher GV indices in MS than in metabolically healthy adults, although findings for coefficient of variation and mean amplitude of glucose excursions are inconsistent. Prolonged sedentary behavior worsens postprandial glycemia, whereas interrupting sitting with light walking or standing consistently improves postprandial glucose and, in some trials, lowers mean glucose or iAUC without uniform changes in GV metrics. Emerging evidence suggests that SPU, utilizing the high oxidative capacity of the soleus muscle, reduces postprandial glucose and hyperinsulinemia with minimal fatigue, with additional potential benefits for lipid metabolism. CONCLUSIONS Breaking up prolonged sitting is a practical strategy to attenuate postprandial dysglycemia, and SPU represents a promising sedentary-interruption modality. However, evidence on its direct effects on GV in MS is limited, underscoring the need for large-scale randomized trials.
PURPOSE Sand walking, a type of marine healing program, has been adopted as a sports training and rehabilitation method because it lowers the risk for injury by reducing muscle and joint loads through shock relief. This study performed a three-dimensional (3D) biomechanical analysis to compare walking on firm versus sandy surfaces in healthy adults in a laboratory environment that closely replicated real beach sand. METHODS The 3D joint range of motion (ROM), stance time and muscle activity of the lower extremities were analyzed while 34 healthy adults walked on firm versus sandy surfaces using a constructed sand track (7.2×0.9×0.2 cm). RESULTS Sagittal ROMs of the hip and knee joints were significantly greater on the sandy surface than those on the firm surface, whereas the horizontal ROM of the knee joint was significantly lower on the sandy surface than that on the firm surface. Ankle ROMs were significantly greater across all planes. Significantly longer stance times were observed for the sandy surface versus the firm surface. The gastrocnemius and gluteus medius muscles exhibited significantly higher activity on the sandy surface versus the firm surface during the loading and terminal stance phases. CONCLUSIONS This study revealed 3D biomechanical changes in the lower extremities during sand walking, increasing joint ROM and muscle activity while extending stance time, suggesting that beach sand is a suitable resource for gait rehabilitation and marine healing programs.
