Heart rate deflection point as a strategy to defend stroke volume during incremental exercise

• Published in: Journal of applied physiology (1985) 2005-05, Vol.98 (5), p.1660-1665
• Main Authors: Lepretre, Pierre-Marie, Foster, Carl, Koralsztein, Jean-Pierre, Billat, Veronique L
• Format: Article
• Language: English
• Subjects: Adult; Athletes; Bicycling; Biological and medical sciences; Blood Gas Analysis - methods; Blood pressure; Cardiology; Exercise; Exercise Test - methods; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Humans; Male; Physical Exertion - physiology; Stroke Volume - physiology; Time Factors
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00837.2004

1 Laboratoire d'Etude de la Physiologie de l'Exercice, Department of Sciences and Technology in Sports and Physical Activities, University of Evry Val d'Essonne, Evry, France 2 University of Wisconsin-La Crosse, La Crosse, Wisconsin; and 3 Sport Medicine Center of the Caisse Centrale d'Activités Sociales, Paris, France Submitted 4 August 2004 ; accepted in final form 29 November 2004 The purpose of this study was to examine whether the heart rate (HR) deflection point (HRDP) in the HR-power relationship is concomitant with the maximal stroke volume (SV max ) value achievement in endurance-trained subjects. Twenty-two international male cyclists (30.3 ± 7.3 yr, 179.7 ± 7.2 cm, 71.3 ± 5.5 kg) undertook a graded cycling exercise (50 W every 3 min) in the upright position. Thoracic impedance was used to measure continuously the HR and stroke volume (SV) values. The HRDP was estimated by the third-order curvilinear regression method. As a result, 72.7% of the subjects (HRDP group, n = 16) presented a break point in their HR-work rate curve at 89.9 ± 2.8% of their maximal HR value. The SV value increased until 78.0 ± 9.3% of the power associated with maximal O 2 uptake ( O 2 max ) in the HRDP group, whereas it increased until 94.4 ± 8.6% of the power associated with O 2 max in six other subjects (no-HRDP group, P = 0.004). Neither SV max (ml/beat or ml·beat –1 ·m –2 ) nor O 2 max (ml/min or ml·kg –1 ·min –1 ) were different between both groups. However, SV significantly decreased before exhaustion in the HRDP group (153 ± 44 vs. 144 ± 40 ml/beat, P = 0.005). In the HRDP group, 62% of the variance in the power associated with the SV max could also be predicted by the power output at which HRDP appeared. In conclusion, in well-trained subjects, the power associated with the SV max -HRDP relationship supposed that the HR deflection coincided with the optimal cardiac work for which SV max was attained. physical work curve break point; left ventricular ejection fraction; cycling graded test Address for reprint requests and other correspondence: Pierre-Marie LEPRETRE, LEPHE, Dept. of STAPS, Univ. of Evry Val d'Essonne, Sport Medicine Center of the CCAS, 2 Ave. Richerand, Paris F-75010, France (E-mail: lepretre.pierre-marie{at}wanadoo.fr )