Targeting Low Exercise Capacity: A Probiotic Strategy Using Lactobacillus rhamnosus GKLC1 to Improve Endurance and Metabolism

Probiotics have recently gained attention for their potential to reduce fatigue and enhance exercise performance in athletes. However, evidence regarding their effects in individuals with intrinsically low exercise capacity remains limited. In this study, we evaluated the effects of Lactobacillus rhamnosus GKLC1 on physical performance and metabolic health in mice with intrinsically low aerobic exercise capacity (i-LAEC). Male ICR mice selectively bred for low endurance were subjected to an exhaustive swimming test to confirm low exercise capacity. Mice were then randomly assigned to receive either strain GKLC1 (0.021 g/kg body weight/day) or sterile water (control) for six consecutive weeks (n = 6 per group). Exercise performance was assessed via a treadmill exhaustion test in week 4. Fatigue-associated biomarkers, including serum lactate and blood urea nitrogen (BUN), were analyzed during and after exercise in week 5. Glucose tolerance, body composition, and tissue glycogen content were measured in the final week. Strain GKLC1 supplementation significantly improved endurance performance and promoted more efficient lactate metabolism and post-exercise recovery. Additionally, strain GKLC1 enhanced glucose tolerance, reduced epididymal fat mass, and increased glycogen storage in both liver and muscle tissues. These findings suggest that L. rhamnosus GKLC1 may not only improve exercise capacity but also enhance systemic energy metabolism in subjects with low intrinsic aerobic performance.