PURPOSE: To evaluate and compare salivary and plasmatic creatine kinase (CK) and lactate dehydrogenase (LDH) levels following high-intensity continuous exercise (HICE) protocol applied to qualified athletes, as well as to determine a correlation between the analyzed biomarkers in blood serum and oral fluid before and immediately after exercise.
METHODS: 13 first-class rowers at the age of 17.1 ± 0.6 years participated in the study. Athletes performed the HICE protocol consisted of 2000 m distance at 80-90% of VO2max using a rowing ergometer. Blood and saliva samples were taken before (pre-exercise) and immediately after exercise (post-exercise). Salivary and plasmatic CK and LDH activities were measured using a biochemical analyzer. To determine any significant differences among pre-exercise and post-exercise conditions, Wilcoxon signed-rank test was applied. Correlation analysis was performed using Spearman's correlation coefficient (rs).
RESULTS: Plasmatic CK activity significantly increased post-exercise (p = 0.0002) with HICE protocol compared to pre-exercise. In relation to salivary CK levels, there was also a significant (p = 0.001) increase at post-exercise compared to pre-exercise. Regarding plasmatic LDH activity, a significant (p = 0.002) increase was observed in the HICE protocol at post-exercise compared to pre-exercise. Interestingly, LDH activity in saliva samples showed similar results to that in plasma, with a significant (p = 0.001) increase in salivary LDH levels at post-exercise compared to pre-exercise. At pre-exercise, a strong positive correlation of CK activity was observed between the saliva and plasma (rs = 0.78, p = 0.002). At post-exercise was also verified to have correlations in plasmatic and salivary CK levels (rs = 0.86, p = 0.0001). Moreover, a strong positive correlation between plasmatic and salivary LDH activity was observed both before and immediately after exercise (rs = 0.73, p = 0.005, and rs = 0.85, p = 0.0002, respectively).
CONCLUSIONS: The HICE performed at 80-90% of VO2max increases salivary and plasmatic CK and LDH activities. Thus, salivary CK and LDH levels can be used as biomarkers of muscle damage around athletes who have performed HICE protocols.
Supported by the Competitiveness Enhancement Program of Lobachevsky University (N-439-99_2020-2021).