Associations between Borg's rating of perceived exertion and changes in urinary organic acid metabolites after outdoor weight-bearing hiking.

BACKGROUND: Developing methods to monitor exercise load and evaluate body fatigue and muscle injury over time in hiking training remains a key problem to be solved. A widely used psycho-physical tool to assess the subjective perception of effort during exercise is Borg's rating of perceived exertion (BRPE) scale. Data on the relationships and validity of the BRPE compared to objectively assessed metabolic criteria are still lacking, especially urinary organic acid concentrations. AIM: To verify whether the BRPE scale could be used in the prescription of outdoor hiking with weight-bearing and reveal the relationship between the BRPE scale and urinary physiological measures. METHODS: Eighty-nine healthy men (average age: 22 years) were enrolled in a 40 km (6 h) hiking training exercise with a 20 kg load. After training, the BRPE scale (6-20) was completed. All participants were divided into three groups according to the rating of the BRPE scale. Urine samples were collected before and after training. Urinary myoglobin levels were measured immediately using the fluorescent immunoassay method. The remaining urine was subpacked and frozen for the subsequent detection of urinary organic acids using gas chromatography and mass spectrometry. RESULTS: The contents of organic acids and myoglobin in urine were significantly increased after participants hiked 40 km (6 h) with a 20 kg load. Only orthogonal partial least-squares discrimination analysis performed well in separating the group with a BRPE score of 6-12 from the group with a BRPE score of 13-20. Significant differences in the urine levels of several organic acids were observed between the two groups, and the heatmap also presented different metabolic profiles based on BRPE. According to the standard of a variable importance in the projection > 1, fold change > 1.5 and P < 0.05, 19 different metabolites of urinary organic acids were screened and enriched in pathways mainly including the citrate cycle (tricarboxylic acid cycle) and alanine, aspartate and glucose metabolism. CONCLUSION: The BRPE scale identified significantly different urinary organic acid profiles between the higher and lower BRPE value groups, and, thus, could be used to monitor body fatigue in individuals participating in long-distance outdoor hiking with weight bearing.

[Expression of iNOS in the testis of Fmr1 knockout mice in different developmental stages].

OBJECTIVE: To analyze the expression of inducible nitric oxide synthase (iNOS) in the testis tissues of Fmr1 (fragile X mental retardation 1) knockout and wild-type male mice in different developmental stages, and provide background information for researches on fragile X syndrome. METHODS: This study included 4, 6, 8 and 10 weeks old Fmr1 knockout and wild-type male mice, 6 in each age group. We identified the genotype of the mice by PCR, and detected and compared the expression of iNOS in the testis tissues of the Fmr1 knockout and wild-type mice by immunohistochemistry. RESULTS: The iNOS expression was weakly positive in the Leydig cells of the 4-week-old mice, moderately positive in the 6-week-old ones, and strongly positive in 8- and 10-week-old ones, significantly weaker in the Fmr1 knockout than in the wild-type ones. CONCLUSION: The expression of iNOS significantly decreases in the testis of Fmr1 knockout mice, suggesting that iNOS may be involved in the pathogenesis of fragile X syndrome.