Heavy load endurance training leading to functional overreaching transiently impaired cardiac response to exhaustive exercise, with lower cardiac output and reduced epinephrine excretion.
Cohort (n=35)
Does a heavy load endurance training program inducing functional overreaching impair cardiac response and epinephrine excretion during exhaustive exercise in experienced male triathletes?
Functional overreaching in endurance athletes transiently impairs the cardiac response to exhaustive exercise, likely driven by reduced epinephrine excretion.
Functional overreaching (F-OR) induced by heavy load endurance training programs has been associated with reduced heart rate values both at rest and during exercise. Because this phenomenon may reflect an impairment of cardiac response, this research was conducted to test this hypothesis. Thirty-five experienced male triathletes were tested (11 control and 24 overload subjects) before overloading (Pre), immediately after overloading (Mid), and after a 2-wk taper period (Post). Physiological responses were assessed during an incremental cycling protocol to volitional exhaustion, including catecholamines release, oxygen uptake (V̇o2), arteriovenous O2 difference, cardiac output (Q̇), and systolic (SBP) and diastolic blood pressure (DBP). Twelve subjects of the overload group developed signs of F-OR at Mid (decreased performance with concomitant high perceived fatigue), while 12 others did not acute fatigue group (AF). V̇o2max was reduced only in F-OR subjects at Mid. Lower Q̇ and SBP values with greater arteriovenous O2 difference were reported in F-OR subjects at all exercising intensities, while no significant change was observed in the control and AF groups. A concomitant decrease in epinephrine excretion was reported only in the F-OR group. All values returned to baseline at Post. Following an overload endurance training program leading to F-OR, the cardiac response to exhaustive exercise is transiently impaired, possibly due to reduced epinephrine excretion. This finding is likely to explain the complex process of underperformance syndrome experienced by F-OR endurance athletes during heavy load programs.
Meur et al. (Fri,) conducted a cohort in Functional overreaching (n=35). Heavy load endurance training program vs. Control group was evaluated on Physiological responses during an incremental cycling protocol to volitional exhaustion. Heavy load endurance training leading to functional overreaching transiently impaired cardiac response to exhaustive exercise, with lower cardiac output and reduced epinephrine excretion.
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