Effects Of High-intensity Interval Exercise And Moderate-intensity Continuous Exercise On Serum Troponin Levels In Different Phases Of The Menstrual Cycle

Background:Cardiac troponin T?cTnT?is a highly specific biomarker of myocardial injury,which is mainly used to diagnose acute myocardial infarction.However,there is increasing evidence that exercise can increase blood cTnT and can exceed clinical cut-off values,which is of concern to the clinical and sports medicine community.Considering that acute exercise itself,especially high-intensity strenuous exercise,can transiently increase the risk of cardiac events in susceptible people,it is necessary to explore the regularity and characteristics of exercise-induced cTnT elevation.Previous studies have focused on looking at men,and it remains unclear whether menstrual cycle phase in women affects cTnT levels after acute exercise.In addition,high-intensity interval exercise?HIE?is becoming increasingly popular,and it remains unclear whether cTnT release after such exercise differs in women from that after traditional moderate-intensity continuous exercise?MCE?.The availability of this information will help clinicians accurately interpret the clinical significance of cTnT after exercise in women exercisers as well as guide the development of an exercise prescription.Objective:To observe the level of serum cardiac troponin before and after HIE and MCE at different menstrual cycle stages.Methods:Eighteen young women completed four exercise sessions,including follicular phase HIE,follicular phase MCE,luteal phase HIE,and luteal phase MCE,at different menstrual cycle phases?confirmed by blood estrogen levels?in random order.The HIE protocol was a continuous exercise with 90%V?O_2max exercise intensity and repeated exercise for 4 min with intermittent rest for 3 min cycles until the output work reached 300KJ,while the MCE protocol was a continuous exercise with 60%V?O_2max exercise intensity with equal output work.Blood samples and high-sensitivity immunoassays were used to measure serum cTnT before,immediately,1,3,and 4 hours after each exercise session.Heart rate,blood pressure,and subjective sensation of movement?RPE?were measured during and/or before and after each exercise session.Results:All four exercises resulted in a significant increase in cTnT?P<0.05?with an increase of 33¹28%.There was no significant difference in cTnT between the follicular phase and luteal phase at all observation points before and after exercise?P>0.05?.In the follicular phase,cTnT levels were significantly higher after HIE exercise than at the corresponding observation point of MCE?P<0.05?,but there was no significant difference in cTnT levels between the two exercises in the luteal phase?P>0.05?.There was no significant difference in exercise center rate and RPE between follicular and luteal phases?P>0.05?,but this two indexes of HIE were significantly higher than those of MCE?P<0.05?.Both exercises resulted in a significant increase in systolic blood pressure immediately after exercise compared to before exercise followed by a significant decrease?p<0.05?and unaffected by menstrual cycle phase,but systolic blood pressure immediately after HIE was significantly higher than MCE?p<0.05?.Conclusions:Both HIE or MCE lead to cTnT elevation in young women.Menstrual cycle phase had no effect on cTnT levels after HIE or MCE,but follicular phase HIE resulted in higher post-exercise cTnT levels than MCE.The degree of exercise stress reflected by heart rate,RPE and blood pressure may partially explain the above findings.