Plasma Malondialdehyde Increases Transiently after Ischemic Forearm Exercise

Exercise and ischemia-reperfusion (I-R) have previously been shown to induce oxidative stress in skeletal muscle. Previous studies have demonstrated conflicting results when exercise-induced oxidative stress has been measured using plasma carbonyls, specifically malondialdehyde (MDA). These conflicting results likely stem from the timing and method utilized to measure plasma carbonyls. PURPOSE: To determine the concentration and timing of aldehyde and ketone generation after ischemic forearm exercise utilizing HPLC analysis. METHODS: Plasma carbonyls, including MDA, 17-beta-estradiol, and lactate, were measured after a forearm ischemic exercise test (FIT) in males and females (in both phases of their menstrual cycle). Blood flow was occluded to the forearm, and six cycles of maximal isometric handgrip exercise were executed using a 9:1, duty:rest cycle, for 60 s. Blood samples were collected pre, immediately post, and 1, 3, and 10 min post-FIT. RESULTS: Plasma MDA increased similarly for both males and females immediately post and 1 min post-FIT (P<0.05) and returned to baseline levels by 3 min post-FIT. Ischemic exercise did not alter plasma concentrations of other measured carbonyls, and gender and menstrual cycle did not influence any measured variable (P>0.05), except for lactate concentrations, which increased more for males (P<0.05). Force was higher for males at all time points (P<0.05); however, there was no effect of gender on percent fatigue. CONCLUSIONS: Future studies must consider sampling times after metabolic stress in order to quantify changes in MDA concentration.