A randomized controlled trial effect of forest hiking on tensor muscle function, erythrocyte factors, and leukocytes’ subsets in older adults: a pilot study

This study examined the process of forest hiking (FH) through skeletal muscle oxygen saturation (SmO₂) and investigated subsequent changes in muscle function, erythrocytes, and immunocytes. A total of 60 participants who their ages, heights, and weights of 73.05±3.23 years, 1.63±0.06 m, and 67.75±9.22 kg. They resided in two living communities, and were assigned to the control (CON, n=30) group, whereas those from the other were allocated to the FH (n=30) group. The intervention consisted of a hiking program performed for 120 min per day, twice per week, over a 4-week period. The degree of oxygen utilization in muscles during the hiking was monitored by measuring SmO₂ in the vastus lateralis (VL). During hiking, SmO₂ levels in the FH group progressively declined, reaching a nadir between 60 and 90 min, followed by partial recovery. After the intervention, the FH group showed pronounced improvements in contraction time in the VL than in the biceps femoris (BF), while maximum displacement improved in both the VL and BF (<i>P</i><0.05). Among erythrocytes parameters, significant interaction effects were observed for hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin concentration (<i>P</i><0.05). In addition, significant interaction effects were found in immunocytes (<i>P</i><0.01). This study demonstrated that SmO₂ can be effectively measured during FH and confirmed that a 4-week hiking induced marked improvements not only in muscle function but also in erythrocytes and immunocytes in older adults.