(1) The purpose of this study was to investigate the effect of whey protein supplementation under dietary control on improvements in muscle mass and function following resistance exercise training. (2) Thirty-two men were randomly assigned to a whey protein supplementation group taking whey protein isolate (PSG, n = 17) and a placebo group (CON, n = 15). Participants were provided with three meals per day corresponding to the estimated individual daily energy intake. The supervised resistance exercise program was conducted 60 min per day, six days per week, for four weeks. (3) Post-intervention, there was a significant interaction between groups in terms of muscle mass increase (p = 0.033, η² = 0.14), with a greater increase in the PSG. There were also significant interactions between the groups and increases in peak torque of the dominant knee flexors (p = 0.048, η² = 0.12), dominant shoulder extensors, and non-dominant shoulder extensors (p = 0.028, η² = 0.15; p = 0.015, η² = 0.18), and the total work of the dominant knee and shoulder extensors (p = 0.012, η² = 0.19; p = 0.013, η² = 0.19), with greater increases in the PSG. (4) These results suggest that whey protein supplementation enhances resistance exercise-induced increase in muscle mass and overall muscular strength and endurance, independent of dietary influence.

Exercise and diet have positive effects on hepatic fat reduction, and protein supplementation is known to lower hepatic fat accumulation. However, the effect of a combination of exercise and whey protein supplementation (WPS) on hepatic fat content (HFC) is unknown. We investigated the effect of WPS on HFC during resistance exercise and diet control intervention for four weeks. A total of 34 sedentary males participated and were randomly assigned to two groups: a protein supplement group (PSG, n = 18) and a control group (CG, n = 16). The PSG took 60 g of WPS per day, and the CG took 60 g of an isocaloric placebo per day. All participants were fed a calorie-controlled diet throughout the study period, with their daily caloric intake determined by their resting metabolic rate and physical activity level. Both groups performed resistance exercises supervised by experts at 60-70% of their maximum efforts for 60 min/day, 6 days/week for 4 weeks. HFC was assessed using the controlled attenuation parameter (CAP) after an 8 h fast, at pre-, mid-, and post-intervention. Liver enzymes and lipid profile were also analyzed after an 8 h fast and pre- and post-intervention. The CAP was significantly reduced after 4 weeks of intervention in both groups (PSG, p < .001; CG, p = .002). However, there was no significant interaction between the group and changes in CAP. Interestingly, when comparing the pre- and mid-tests, both groups also had significantly reduced CAP (PSG, p = .027; CG, p = .028), but there was a significant difference in the amount of change in CAP between the two groups (PSG, -47.2 ± 25.4 dB/m; CG, -19.5 ± 15.1 dB/m; p = .042). For liver enzymes, there was a significant interaction between the two groups and a change in aspartate transaminase (AST) (p = .038). However, alanine aminotransferase (ALT) levels were significantly decreased only in the PSG group (p = .002). In lipids, both groups showed significantly decreased total cholesterol (p < .001) and low-density lipoprotein cholesterol (p < .001) after the intervention. Our data showed that WPS may not enhance the overall effects of resistance exercise on HFC and lipid profiles. However, in part, WPS may have a beneficial effect on liver enzymatic changes and rapid response to resistance exercise-induced HFC reduction.

Objective: This study addresses declining physical fitness among Korean firefighters due to a low exercise participation rate caused by the absence of exercise instructors. The research explores Virtual Mate (VM), a Kinect-based mixed reality device, as a potential solution, but its capacity to replace training instructors in enhancing physical fitness remains uncertain. Methods: Twenty Korean male firefighters were divided into two groups: the exercise group received an 8-week intervention using VM, while the control group maintained regular physical activity. Cardiopulmonary function and muscle function were measured. Results: After 8 weeks, the exercise group demonstrated a significant improvement in VO_2peak. Furthermore, there were notable enhancements in the strength and endurance of most knee, shoulder, and trunk flexors and extensors. Conclusions: Integrating VM into an exercise program can effectively improve cardiorespiratory and muscular function in Korean firefighters.

Background/Objectives: Metabolic dysfunction-associated steatotic liver disease (MASLD) often requires caloric restriction (CR) to reduce hepatic fat, but CR can compromise muscle mass and function. Resistance training and whey protein are anabolic stimuli, yet their independent and combined effects under substantial CR are unclear. Methods: In a 4-week randomized, double-blind trial, adults with MASLD (n = 45) under ~30% CR were allocated to four groups: resistance training with whey protein supplementation (E-PRO), resistance training with placebo (E-PLA), whey protein supplementation only (PRO), or placebo only (PLA). PRO groups consumed 1.5 g·kg⁻¹·day⁻¹ protein, while PLA groups consumed 0.8 g·kg⁻¹·day⁻¹. Exercise groups performed supervised exercise 5 days/week. Outcomes included body composition and isokinetic muscle function. Results: Across ~30% CR, all groups reduced body weight and fat mass without skeletal muscle mass loss; no between-group differences in body composition changes were observed. For peak torque, E-PRO improved across all regions except trunk, E-PLA improved except non-dominant shoulder flexors and trunk flexors, PRO improved non-dominant knee flexors and shoulder extensors, and PLA showed no change. For total work, E-PRO and E-PLA increased across all regions PRO improved dominant knee extensors/flexors and shoulder extensors; PLA increased only non-dominant knee extensors. E-PRO and E-PLA exceeded PLA for multiple knee/shoulder/trunk outcomes. Conclusions: In individuals with MASLD undergoing severe CR, ≥0.8 g·kg⁻¹·day⁻¹ of protein preserves skeletal muscle mass. However, the anabolic synergy of resistance training and protein for functional adaptation appears to be blunted by the substantial energy deficit.

OBJECTIVES The purpose of this study is to analyze whether the association between physical activity and perceived stress differs across urbanicity levels among Korean adolescents.METHODS This study utilized data from the Korea Youth Risk Behavior Survey (KYRBS), collected between 2018 and 2023. Physical activity was dichotomized based on engaging in ≥60 minutes of activity per day for seven consecutive days. Perceived stress was categorized into high and low levels based on survey responses. Urbanicity was classified into metropolitan, mid-sized city, or rural. Complex-sample logistic regression analyses were performed to assess the association between physical activity and perceived stress by urbanicity level, adjusting for age, sex, economic status, academic performance, school type, height, and weight.RESULTS A total of 322,978 adolescents were included in the analysis. The association between physical activity and perceived stress differed by urbanicity level. Adolescents in mid-sized cities who engaged in physical activity for seven consecutive days were more likely to report lower perceived stress (OR = 1.087, 95% CI = 1.035-1.142). However, no significant associations were observed among adolescents residing in metropolitan areas (OR = 1.048, 95% CI = 0.996-1.103) or rural areas (OR = 1.079, 95% CI = 0.950-1.225).CONCLUSIONS This study confirmed that the association between physical activity and perceived stress among adolescents varies by urbanicity level. Significant associations were observed only in mid-sized cities, suggesting that the stress-reducing benefits of physical activity may be influenced by contextual environmental factors. These findings highlight the need for region-specific physical activity promotion strategies to support adolescent mental health.

Objective: The Candidate Physical Capability Test (CPAT) has been used in many countries to assess the fitness levels of firefighters, but it requires a special facility with a space of at least 900 square m² and expensive equipment. Because it can be difficult to have both money and space at smaller gas stations, we have developed the Korean Firefighter Performance Battery (KFPB). Methods: To verify the validity and reliability of the developed KFPB, this study consists of three parts, a validation test, reliability test, and evaluation criterion. Results: As a result of the analysis, the KFPB met all of the criteria as a valid evaluation. Furthermore, the KFPB seems to compensate for the shortcomings of CPAT. Conclusions: In locations where the CPAT is difficult to administer, the KFPB is expected to be used as a firefighting job–related physical fitness evaluation.