The cardiovascular impact of intense eccentric isokinetic exercise versus aerobic treadmill running

BACKGROUND: Regular physical activity is an important health factor, but intense physical stress can increase the risk of heart disease.
OBJECTIVE: Our aim was to determine the potential cardiac repercussions of, and the oxidative stress resulting from a maximal eccentric isokinetic exercise and a 1-hour treadmill run at 75% ˙V O2 max (maximal exercise done 6 weeks before).
METHODS: Twelve young sedentary healthy subjects randomly performed two tests separated by 6 weeks: 1) 3 sets of 30 maximal eccentric isokinetic contractions of the quadriceps; 2) a 1-hour running on treadmill at 75% ˙V O2 max. We drew blood samples just before each exercise (T1), and just after (T2), 3 hours after (T3), and 24 hours after (T4) the end of each exercise to measure cardiac and oxidative stress biomarkers.
RESULTS: In the running group, we observed significant differences for myoglobin (T3: 145 ± 80 μg/L), creatinine kinase (T4: 593 ± 350 mg/L), oxidized glutathione (T2: 22 ± 15.6 μmol/L), and highly sensitive cardiac troponin T, (T3: 0.051 ± 0.038 ng/mL). In the isokinetic group, we observed significant differences for myoglobin (T3:1419 ± 2533 mg/L), creatine kinase (3303 ± 7159 mg/L), and oxidized glutathione (T4:24 ± 14 μmol/L). Between isokinetic exercise and running, we observed significant differences for uric acid (p < 0.05, running > eccentric), myoglobin (p < 0.05, ditto), NT-proBNP (p < 0.05, ditto), hsTnT (p < 0.01, ditto), and oxidized glutathione (p < 0.05).
CONCLUSIONS: As cardiac biomarkers appear practically unmodified after the isokinetic exercise, despite the considerable oxidative stress, we suggest that the application of intense maximal eccentric isokinetic exercise, when indicated, should be safe for most patients including those whose cardiac status is unknown. On the other hand, the increase in cardiac biomarkers observed after running, could reflect leakage of these biomarkers from the cytosolic pool of cardiac cells, linked to membrane damage, rather than the result of a major injury and hence running is supposed to be a safe practice. However, since sudden death during running has been previously described, assesment of the cardiac biomarkers and a follow-up by a sport doctor is important especially if there is a cardiac family history.