title: Endurance performance and nocturnal HRV indices.
abstract: The effects of endurance training on endurance performance characteristics and cardiac autonomic modulation during night sleep were investigated. Twenty-four sedentary subjects trained over four weeks two hours per week at an average running intensity of 76+/-4% of their heart rate reserve. The R to R ECG-intervals were recorded and heart rate variability indices including high frequency power (HFP) were calculated for the nights following the training days every week. The subjects were divided into responders and non-responders according to the improvements in the maximal velocity of the incremental treadmill test (v(max)). The responders improved their v(max) by 10.9+/-46 % (p < 0.001) while no changes were observed in the non-responders (1.6+/-3.0%), although there were no differences in any training load variables between the groups. In the responders nocturnal HFP was significantly higher during the fourth training week compared to the first training week (p=0.036). Furthermore, a significant correlation was observed between the change in v(max) and the change in nocturnal HFP (r=0.482, p=0.042). It was concluded that after similar training, an increase in cardiac vagal modulation was related to improved v(max) in the sedentary subjects.
authors.affiliation: KIHU-Research Institute for Olympic Sports, Physiology, Jyväskylä, Finland. ari.nummela@kihu.fi
authors.forename: A
authors.initials: A
authors.lastname: Nummela
authors.forename: E
authors.initials: E
authors.lastname: Hynynen
authors.forename: P
authors.initials: P
authors.lastname: Kaikkonen
authors.forename: H
authors.initials: H
authors.lastname: Rusko
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D000704:Analysis of Variance; D001341:Autonomic Nervous System; D015992:Body Mass Index; D002940:Circadian Rhythm; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D012885:Skinfold Thickness; D013223:Statistics as Topic; D011795:Surveys and Questionnaires; D013997:Time Factors