Hydrotherapy is widely used for the treatment and rehabilitation of patients, but it can also be applied to prevent diseases in healthy people. This review investigates the health effects of water immersion, a form of hydrotherapy, and the mechanisms by which the properties of water elicit such an effect. We searched PubMed, EMBASE, Cochrane Library, and CINAHL to identify relevant articles, of which 13 met the inclusion criteria. Various factors of water immersion were investigated in the 13 selected articles, including water temperature, immersion height, and application area. With respect to health effects, warm and cold water immersion affects the cardiovascular and neuromuscular systems, respectively. Nine articles focused on the effects of warm water immersion, explaining its thermal effect in relation to changes in disease-related serum substance levels and hemodynamic changes. While the sample population in most studies comprised young adults, two articles applied partial water immersion to the legs of elderly subjects to assess its effect on sleep. Because the water immersion protocols applied in the 13 articles were inconsistent, the health benefits could not be clearly explained. However, we expect the present findings to be beneficial for providing research guidelines for studies on the application of water immersion.

With an increase in the obese population, the prevalence of metabolic syndrome is increasing in Korea. This study aimed to identify sex- and age-specific risk factors for metabolic syndrome. A secondary data analysis was performed using the Korean National Health and Nutritional Examination Survey. Participants comprised 6144 adults aged 20–79 years. The prevalence of metabolic syndrome was high in the middle- and old-aged men (31.9% and 34.5%, respectively) and in old-aged women (39.1%). Risk factors for metabolic syndrome showed different patterns for men and women. In men, alcohol drinking was identified as the main risk factor for hypertension (odds ratio (OR); young = 3.3 vs. middle age = 2.0), high triglycerides (young = 2.4 vs. middle age = 2.2), and high fasting blood sugar (middle age = 1.6). In women, the main risk factors were household income and education level, showing different patterns in different age groups. In conclusion, the vulnerable groups at high risk of metabolic syndrome are those of middle-aged men and women. The pattern of risk factors is sex-specific.

Forest therapy involves visiting forests or conducting forest-based treatment activities to improve one’s health. Studies have investigated the health benefits of forests, but consensus has not been reached. This study comprised a systematic review and meta-analysis to determine how forest therapy affects the physiological and psychological health of adults. The Cumulative Index to Nursing and Allied Health Literature, Embase, and Medline databases were searched on 31 August 2021. Systematic review and meta-analysis, risk evaluation, GRADE evaluation, and advertisement effect evaluation were performed for each article. The effect size was calculated by dividing blood pressure as a physiological indicator and depression as a psychological indicator. Of the 16,980 retrieved studies, 17 were selected based on the inclusion criteria. Of these, eight studies were included in the meta-analysis. The effect size of forest therapy on improving systolic and diastolic blood pressure was not significant; however, it significantly reduced depression. While the results have limited generalizability due to the inclusion of few studies, the effects of forest therapy on reducing depression have been confirmed. Since the application of forest therapy was heterogeneous in these studies, a moderator effect analysis or subgroup analysis in meta-analysis should be performed in the future.

Adverse social behavior (ASB) by colleagues or superiors in the workplace is considered highly stressful for workers in South Korea. The authors investigate the mechanism by which ASB reduces productivity (measured in terms of sickness presenteeism (SP)), by examining the potential mediating role of musculoskeletal disorders (MSDs). All data are derived from the fourth Korean Working Conditions Survey, which investigated a representative sample of the working population. The authors analyze their general characteristics (age, gender, income, and education), work-related factors (job type, occupational ergonomic risk, job resource, employment contract, work schedule, working hour, and job demand), and health-related factors (self-rated health and MSDs). The authors use a two-step regression analysis to estimate the direct effect of ASB on SP and the indirect effect of SP via MSDs. The authors find that MSDs mediate 16.7% of the total effect of ASB on SP. When employment type and job conditions are considered, the role of the mediating variable in the group with a permanent contract, no shift or night work, and high working time is greater than the counterpart of each variable. Various strategies are needed to address MSDs according to the working environment, which might help limit the negative impact of ASB on SP.

This study aimed to comprehensively investigate the thermal comfort and physiological and psychological effects according to tree density in forest environments during rest and during and after physical activities in the summer. Participants consisted of 18 male university students (average age: 24.0 ± 1.6 years old), and a within-subjects experimental design was used. Participants sat on a chair for 5 min to rest, performed a step-box exercise for 8 min, and then sat on the chair again, and rested for 10 min in a forest with high tree density (85.6%) and one with low tree density (12.2% as a control). Thermal comfort (predicted mean vote; PMV and percentage of dissatisfied; PPD) and physiological and psychological responses were measured. We investigated and analyzed the changes in “rest”, “during exercise”, and “after exercise”. As a result, a forest with high tree density showed a statistically significant decrease in PMV and PPD values; an increase in parasympathetic nervous activity; a decrease in respiratory rate, systolic blood pressure, and pulse rate; an improvement in mood state; an increase in comfortable, relaxed, and natural feelings; and more of an increase in personal thermal sensation during the recovery period after physical activities than in a forest with low tree density. In conclusion, a forest with high tree density during recovery after physical activities in the summer has higher thermal comfort and physiological and psychological relaxation effects on humans, as compared to one with low tree density.

This study aimed to verify the effects of prescribed personalized forest walking by considering individuals’ characteristics. To prescribe individualized exercise programs, we developed an algorithm to calculate exercise intensity based on each participant’s age, regular exercise, fatigue level, and chronic disease type, if any. To investigate the effects of forest walking on physical and mental health based on exercise prescription, we recruited 59 participants (average age: 39.1 ± 19.0 years old) aged 18 years or older. Physiological and psychological responses were compared before and after walking in the forest. Systolic blood pressure, diastolic blood pressure, percent body fat, negative affect, and emotional exhaustion significantly decreased, while the pulse rate significantly increased following the forest walking. Additionally, we investigated the effects of exercise relative to successfully maintaining one’s target heart rate and found that these effects were even greater when success score of maintaining the target heart rate while walking improved. Comparison of the groups relative to successfully achieving the target heart rate indicated that the high-achievement group had significant reductions in systolic and diastolic blood pressure, body fat mass, percent body fat, negative affect, and emotional exhaustion, and a significant increase in pulse rate. However, the low-achievement group only showed a significant reduction in emotional exhaustion. This study showed that prescribed forest walking has a positive impact on human health and is expected to have a positive effect on the motivation to start and continue exercising.