Temporal tracking of cysteine 34 oxidation of plasma albumin as a biomarker of muscle damage following a bout of eccentric exercise.

PURPOSE: Exercise-induced muscle damage (EIMD) results in the generation of reactive oxygen species (ROS), but little is known about the temporal profile of change in ROS post-EIMD and how ROS levels relate to the onset of and recovery from EIMD. Our primary aim was to examine the effect of EIMD on the pattern of change in the blood level of thiol-oxidised albumin, a marker of oxidative stress. METHODS: Seven male participants were subjected on separate days to eccentric muscle contraction to cause EIMD or a no-exercise condition. After each session, the participants collected daily dried blood spots to measure thiol-oxidised albumin and returned to the laboratory every 2 days for the assessment of indirect markers of EIMD, namely maximal voluntary contraction (MVC), delayed onset muscle soreness (DOMS), creatine kinase (CK), and myoglobin. RESULTS: Eccentric exercise resulted in a significant decrease in MVC and increase in DOMS, CK, myoglobin, and thiol-oxidised albumin with the latter reaching above baseline level within 24-48 h post-exercise. All the markers of EIMD returned to baseline level within 6 days post-exercise, but not the level of thiol-oxidised albumin which remained elevated for 10 days after exercise. There was a moderate correlation between changes in thiol-oxidised albumin and DOMS, but no significant relationship between any other markers of muscle damage. CONCLUSION: The levels of thiol-oxidised albumin increase in response to EIMD and remain elevated for several days post-exercise. The temporal pattern of change in the level of thiol-oxidised albumin suggests that this may be a useful biomarker of muscle repair post-EIMD.

Effects of Simulated High Altitude on Blood Glucose Levels During Exercise in Individuals With Type 1 Diabetes.

CONTEXT: Current exercise guidelines for individuals with type 1 diabetes (T1D) do not consider the impact that high altitude may have on blood glucose levels (BGL) during exercise. OBJECTIVE: To investigate the effect of acute hypoxia (simulated high altitude) on BGL and carbohydrate oxidation rates during moderate intensity exercise in individuals with T1D. METHODS: Using a counterbalanced, repeated measures study design, 7 individuals with T1D completed 2 exercise sessions; normoxia and hypoxia (~4200 m simulated altitude). Participants cycled for 60 min on an ergometer at 45% of their sea-level V̇O2peak, and then recovered for 60 min. Before, during, and after exercise, blood samples were taken to measure glucose, lactate, and insulin levels. Respiratory gases were collected to measure carbohydrate oxidation rates. RESULTS: Early during exercise (<30 min), there was no fall in BGL in either condition. After 1 h of exercise and during recovery, BGL were significantly lower under the hypoxic condition compared to both pre-exercise levels (P = 0.008) and the normoxic condition (P = 0.027). Exercise in both conditions resulted in a significant rise in carbohydrate oxidation rates, which returned to baseline levels postexercise. Before, during, and after exercise, carbohydrate oxidation rates were higher under the hypoxic compared with the normoxic condition (P < 0.001). CONCLUSIONS: The greater decline in BGL during and after exercise performed under acute hypoxia suggests that exercise during acute exposure to high altitude may increase the risk of hypoglycemia in individuals with T1D. Future guidelines may have to consider the impact altitude has on exercise-mediated hypoglycemia.