Search

Background: It is well known that vigorous physical activity induces functional changes in cardiac autonomic nervous system (ANS) activity that is sustained several hours after exercise. However, data related to ANS recovery after more extreme endurance events, such as skyrunning marathons, are still lacking. Objective: The aims of this prospective cohort study were firstly, to determine the ANS response to a SkyMarathon, and secondly, to examine correlates of run performance. Methods: Ten male skyrunners aged 37.2 ± 9.2 years were recruited. The race was performed at a mean intensity 85.4 ± 3.7% of heart rate reserve, and lasted for 338 ± 38 min. Morning supine heart rate variability was measured at 10, 2 and 1 days before race, on the race day, at 5 min intervals for 30 min immediately post-race and then at 5 h and 30 h post. High-frequency power (HF, 0.15-0.50 Hz), low-frequency power (LF, 0.05-0.15 Hz), and square root of the mean of the squares of the successive differences (RMSSD) were calculated and transformed by natural logarithm (Ln). Results: Sympathovagal balance (Ln LF/HF) was most likely increased above baseline during the 30 min post-race and returned to baseline by 5 h. Vagal activity (Ln RMSSD and Ln HF) was most likely decreased below baseline during the 30 min post-race and 5 h of post-race, and recovered to baseline by 30 h. Race time correlated with resting heart rate (r = .81), body mass index (r = .73), maximal power output (r = -.70), and maximal oxygen uptake (r = -.61). Conclusions: The SkyMarathon elicited disturbances in ANS activity, with relative sympathetic activity increased up to 5 h post-race and vagal activity recovering by 30 h. Resting heart rate, body mass index, maximal power output, and maximal oxygen uptake were associated with SkyMarathon performance prediction.

Background: A reduction in the inspired oxygen fraction (FiO2) induces a decline in arterial oxygen saturation (SpO2) and changes of heart rate variability (HRV). It has been shown that SpO2 and HRV responses to similar levels of acute normobaric hypoxia are inter-individual variable. Variable response may be influenced by normoxia reached maximal oxygen uptake (VO2max) value. Objective: The primary aim was to assess HRV and the SpO2 response to hypoxia, and examine the association with normoxic VO2max. Methods: Supine HRV and SpO2 were monitored during normobaric hypoxia (FiO2 = 9.6%) for 10 minutes in 28 subjects, aged 23.7 ± 1.7 years. HRV was evaluated by using both spectral and time domain HRV analysis. Low frequency (LF, 0.05-0.15 Hz) and high frequency (HF, 0.15-0.50 Hz) power together with square root of the mean of the squares of the successive differences (rMSSD) were calculated and transformed by natural logarithm (Ln). Based on the SpO2 in hypoxia, subjects were divided into Resistant (RG, SpO2 ≥ 70.9%, n = 14) and Sensitive (SG, SpO2 2max was higher in SG (62.4 ± 7.2 ml ⋅ kg-1 ⋅ min-1) compared with RG (55.5 ± 7.1 ml ⋅ kg-1 ⋅ min-1, p = .017, d = 0.97). A significant relationship (r = -.45, p = .017) between hypoxic-normoxic difference in SpO2 and normoxic VO2max level was found. Vagal activity (Ln rMSSD) was significantly decreased (SG: p 2, accompanied by greater autonomic cardiac disturbances during hypoxia. The SpO2 reduction was associated with perceived hypoxia comfort/discomfort. The hypoxia discomfort state was accompanied by a greater withdrawal in cardiac vagal activity.

Background: In order to optimize training in soccer, knowledge about the specific position fitness demands and characteristics is required. Objective: The aim of the study was to determine whether there are position specific differences in somatic, cardiorespiratory and autonomic cardiac profiles of professional senior Czech soccer players. Methods: All players (N = 120) were divided into six groups according to field positions: goalkeeper (GK; n = 11), external defenders (ED; n = 15), central defenders (CD; n = 18), external midfielders (EM; n = 18), central midfielders (CM; n = 24) and forwards (F; n = 34). Players underwent anthropometrical and heart rate variability (HRV) assessment, and a maximal incremental running test in order to obtain maximal oxygen uptake (VO2max) and heart rate. HRV variables were transformed using the natural logarithm (Ln). Results: GK and CD were significantly (p = .005) heavier than ED, EM, CM, and F; while F were significantly (p = .026) heavier than CM and EM. GK and CD were significantly (p = .008) taller than ED, EM, CM, F; and EM were significantly (p = .041) shorter than CM and F. The only significant (p = .043) difference in percentage of body fat was observed in CD compared with CM. A significantly (p = .021) lower VO2max was observed for GK compared with ED, CD, EM, CM, and F. Supine HRV was significantly (p = .039) lower for Ln LF/HF in GK compared with F. Standing HRV was significantly (p = .03) lower for Ln LF in CD compared with both ED and F, significantly (p = .028) higher for Ln LF/HF in ED compared with CD and EM. Conclusions: In soccer, specific positions are associated with different height, body mass and aerobic capacity. A lower VO2max and vagal activity in GK compared with other playing positions may not be considered as disadvantage for performance in this specific playing position.