Thirty-day experimental diabetes impairs contractility and increases fatigue resistance in rat diaphragm muscle associated with increased anti-oxidative activity.

Diabetes mellitus is a metabolic disorder that can generate tissue damage through several pathways. Alteration and dysfunction of skeletal muscle are reported including respiratory muscles, which may compromise respiratory parameters in diabetic patients. We have aimed to evaluate the diaphragm muscle contractility, tissue remodeling, oxidative stress, and inflammatory parameters from 30 day streptozotocin-treated rats. The diaphragm contractility was assessed using isolated muscle, tissue remodeling using histology and zymography techniques, and tissue oxidative stress and inflammatory parameters by enzyme activity assay. Our data revealed in the diabetes mellitus group an increase in maximum tetanic force (4.82 ± 0.13 versus 4.24 ± 0.18 N/cm2 (p = 0.015)) and fatigue resistance (139.16 ± 10.78 versus 62.25 ± 4.45 s (p < 0.001)), reduction of 35.4% in muscle trophism (p < 0.001), increase of 32.6% of collagen deposition (p = 0.007), reduction of 21.3% in N-acetylglucosaminidase activity (p < 0.001), and increase of 246.7% of catalase activity (p = 0.002) without changes in reactive oxygen species (p = 0.518) and tissue lipid peroxidation (p = 0.664). All observed changes are attributed to the poor glycemic control (471.20 ± 16.91 versus 80.00 ± 3.42 mg/dL (p < 0.001)), which caused defective tissue regeneration and increased catalase activity as a compensatory mechanism.

Validity analysis of one-repetition maximum strength test for determining the hamstrings-to-quadriceps ratio

One of the approaches to evaluate injury prediction is the hamstrings-to-quadriceps peak torque conventional ratio (H:Q ratio). The gold standard for assessment of muscle strength in vivo is by isokinetic dynamometry; however, the one-repetition maximum strength test (1-RM) presents high correlation with isokinetic data. This study aimed to compare measures of H:Q ratio in young adults obtained by dynamometry and 1-RM testing. No significant differences were observed in the H:Q ratio when comparing 1-RM and dynamometry testing. However, there was a significant and strong correlation between the measurements obtained in the two tests. Despite this correlation, data from both tests are not equal as the H:Q ratio obtained from 1-RM test presents a systematic error. Nonetheless, the results can enhance the applicability of 1-RM test in clinical settings