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J Appl Physiol (1985). 2014 Aug 1;117(3):214-22. doi: 10.1152/japplphysiol.00191.2014. Epub 2014 Jun 12.

Maximal exercise limitation in functionally overreached triathletes: role of cardiac adrenergic stimulation.

Author information

1
Laboratory of Sport, Expertise and Performance, Research Department, French National Institute of Sport, Expertise and Performance, (INSEP) Paris, France; yann.le-meur@insep.fr.
2
Laboratory of Sport, Expertise and Performance, Research Department, French National Institute of Sport, Expertise and Performance, (INSEP) Paris, France;
3
Medical Department, French National Institute of Sport, Expertise and Performance, Paris, France;
4
Laboratory of Functional and Cellular Responses to Hypoxia, University Paris 13 North, Sorbonne Paris City, Bobigny, France;
5
Laboratory of Sport, Expertise and Performance, Research Department, French National Institute of Sport, Expertise and Performance, (INSEP) Paris, France; Sports Performance Laboratory, Sports Medicine Program, University of California, Davis, Sacramento, California;
6
Department of Nuclear Medicine, Centre Hospitalier Universitaire Bordeaux, Bordeaux, France;
7
Department of Cardiology, Pitié-Salpêtrière Hospital, Assistance Publique-Hôpitaux de Paris, Faculté de Médecine Pierre et Marie Curie, Paris, France; and University Paris 6, Paris, France; Institute of Cardiometabolism and Nutrition (ICAN), Paris, France.

Abstract

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.

KEYWORDS:

cardiac response; endurance training; fatigue; overreaching; overtraining

PMID:
24925979
DOI:
10.1152/japplphysiol.00191.2014
[Indexed for MEDLINE]
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