Kristin Behrens

Heart Rate Variability and Blood Pressure during Dynamic and Static Exercise at Similar Heart Rate Levels

Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. Method: 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Results: Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D2 was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting “pure” sympathetic cardiac activity.

Sample Entropy and Traditional Measures of Heart Rate Dynamics Reveal Different Modes of Cardiovascular Control During Low Intensity Exercise

Abstract: Nonlinear parameters of heart rate vari ability (HRV) have proven their prognostic value in clinical settings, but their physiological background is not very well established. We assessed the effects of low intensity isometric (ISO) and dynamic (DYN) exercise of the lower limbs on heart rate matched intensity on traditional and entropy measures of HRV. Due to changes of afferent feedback under DYN and ISO a distinct autonomic response, mirrored by HRV measures, was hypothesized. Five-minute inter-beat interval measurements of 43 healthy males (26.0 ± 3.1 years) were performed during rest, DYN and ISO in a randomized order. Blood pressures and rate pressure product were higher during ISO vs . DYN ( p < 0.001). HRV indicators SDNN as well as low and high frequency power were significantly higher during ISO ( p < 0.001 for all measures). Compared to DYN, sample entropy (SampEn) was lower during ISO ( p < 0.001). Concluding, contraction mode itself is a significant modulator of the autonomic cardiovascular response to exercise. Compared to DYN, ISO evokes a stronger blood pressure response and an enhanced interplay between both autonomic branches. Non-linear HRV measures indicate a more regular behavior under ISO. Results support the view of the reciprocal antagonism being

Cardiac troponin T and echocardiographic dimensions after repeated sprint vs. moderate intensity continuous exercise in healthy young males.

Regular physical exercise can positively influence cardiac function; however, investigations have shown an increase of myocardial damage biomarkers after acute prolonged endurance exercises. We investigated the effect of repeated sprint vs. moderate long duration exercise on markers of myocardial necrosis, as well as cardiac dimensions and functions. Thirteen healthy males performed two different running sessions (randomized, single blinded cross-over design): 60 minutes moderate intensity continuous training (MCT, at 70% of peak heart rate (HRpeak)) and two series of 12 × 30-second sprints with set recovery periods in-between (RST, at 90% HRpeak). Venous blood samples for cardiac troponin T (cTnT), creatine kinase (CK) and MB isoenzyme (CK-MB) were taken 1 and 4 hours after exercise sessions. After each session electrocardiographic (ECG) and transthoracic echocardiographic (TTE) data were recorded. Results showed that all variables - average heart rate, serum lactate concentration during RST, subjective exertion and cTnT after RST - were significantly higher compared to MCT. CK and CK-MB significantly increased regardless of exercise protocol, while ECG and TTE indicated normal cardiac function. Our results provide evidence that RST contributes significantly to cTnT and CK release. This biomarker increase seems to reflect a physiological rather than a pathological phenomenon in healthy, exercising subjects.

Effects of breathing patterns and light exercise on linear and nonlinear heart rate variability

Despite their use in cardiac risk stratification, the physiological meaning of nonlinear heart rate variability (HRV) measures is not well understood. The aim of this study was to elucidate effects of breathing frequency, tidal volume, and light exercise on nonlinear HRV and to determine associations with traditional HRV indices. R-R intervals, blood pressure, minute ventilation, breathing frequency, and respiratory gas concentrations were measured in 24 healthy male volunteers during 7 conditions: voluntary breathing at rest, and metronome guided breathing (0.1, 0.2 and 0.4 Hz) during rest, and cycling, respectively. The effect of physical load was significant for heart rate (HR; p < 0.001) and traditional HRV indices SDNN, RMSSD, lnLFP, and lnHFP (p < 0.01 for all). It approached significance for sample entropy (SampEn) and correlation dimension (D2) (p < 0.1 for both), while HRV detrended fluctuation analysis (DFA) measures DFAα1 and DFAα2 were not affected by load condition. Breathing did not affect HR but affected all traditional HRV measures. D2 was not affected by breathing; DFAα1 was moderately affected by breathing; and DFAα2, approximate entropy (ApEn), and SampEn were strongly affected by breathing. DFAα1 was strongly increased, whereas DFAα2, ApEn, and SampEn were decreased by slow breathing. No interaction effect of load and breathing pattern was evident. Correlations to traditional HRV indices were modest (r from -0.14 to -0.67, p < 0.05 to <0.01). In conclusion, while light exercise does not significantly affect short-time HRV nonlinear indices, respiratory activity has to be considered as a potential contributor at rest and during light dynamic exercise.

Muscular Contraction Mode Differently Affects Autonomic Control During Heart Rate Matched Exercise

The precise contributions of afferent feedback to cardiovascular and respiratory responses to exercise are still unclear. The aim of this crossover study was to assess whether and how autonomic cardiovascular and respiratory control differed in response to dynamic (DYN) and isometric contractions (ISO) at a similar, low heart rate (HR) level. Therefore, 22 healthy males (26.7 ± 3.6 yrs) performed two kinds of voluntary exercises at similar HR: ISO and DYN of the right quadriceps femoris muscle. Although HR was eqivalent (82 ± 8 bpm for DYN and ISO, respectively), rating of exertion, blood pressures, and rate pressure product were higher, whereas breathing frequency, minute ventilation, oxygen uptake and carbon dioxide output were significantly lower during ISO. Tidal volume, end-tidal partial pressures of O2 and CO2, respiratory exchange ratio and capillary blood lactate concentration were comparable between both contraction modes. Heart rate variability (HRV) indicators, SDNN, HF-Power and LF-Power, representing both vagal and sympathetic influences, were significantly higher during ISO. Sample entropy, a non-linear measure of HRV was also significantly affected by contraction mode. It can be concluded that, despite the same net effect on HR, the quality of cardiovascular control during low intensity exercise is significantly different between DYN and ISO. HRV analysis indicated a sympatho-vagal coactivation during ISO. Whether mechanoreceptor feedback alone, a change in central command, or the interaction of both mechanisms is the main contributor of the distinct autonomic responses to the different exercise modes remains to be elucidated.

Relationship between morning heart rate variability and creatine kinase response during intensified training in recreational endurance athletes

Specific physiological responses and their relationship were analyzed in 12 recreational endurance athletes (43.8 ± 7.9 years) during a period of intensified cycling training. Heart rate (HR), HR variability (HRV), serum creatine kinase (S-CK) and haematocrit (Hct) were measured in the mornings before (PRE) and following three consecutive days of intensified training (POST 1–3). Morning HR increased during this period (PRE: 52.2 ± 6.7 bpm, POST 1: 58.8 ± 7.0 bpm, POST 2: 58.5 ± 8.1 bpm, POST 3: 57.9 ± 7.2 bpm; F(3,33) = 11.182, p < 0.001, ηp2 = 0.554). Parasympathetic HRV indices decreased from PRE to POST (F(3,33) ≥ 11.588, p < 0.001, ηp2 ≥ 0.563), no effect was found for sympathetically modulated HRV (F(3,33) = 2.287, p = 0.101, ηp2 = 0.203). Hct decreased (PRE: 49.9 ± 4.0%, POST 1: 46.5 ± 5.1%, POST 2: 45.5 ± 3.8%, POST 3: 43.2 ± 3.4%; F(3,33) = 11.909, p < 0.001, ηp2 = 0.520) and S-CK increased during the training period (PRE: 90.0 ± 32.1 U/L, POST 1: 334.7 ± 487.6 U/L, POST 2: 260.1 ± 303.4 U/L, POST 3: 225.1 ± 258.8 U/L; F(3,33) = 3.996, p = 0.017, ηp2 = 0.285). S-CK release was associated with HR (r = 0.453, p = 0.002, n = 44), RMSSD (r = −0.494, p = 0.001, n = 44) and HF-Power (r = −0.490, p = 0.001, n = 44). A period of intensified training was associated with haemodilution, parasympathetic withdrawal and S-CK-increase. Cardiac autonomic control at morning rest correlated with the S-CK-release; and thus, may serve as a practical mean to complementary monitor and prescribe training load in this population.

Cycling before and after Exhaustion Differently Affects Cardiac Autonomic Control during Heart Rate Matched Exercise

During cycling before (PRE) and after exhaustion (POST) different modes of autonomic cardiac control might occur due to different interoceptive input and altered influences from higher brain centers. We hypothesized that heart rate variability (HRV) is significantly affected by an interaction of the experimental period (PRE vs. POST) and exercise intensity (HIGH vs. LOW; HIGH = HR > HR at the lactate threshold (HRLT), LOW = HR ≤ HRLT) despite identical average HR. Methods: Fifty healthy volunteers completed an incremental cycling test until exhaustion. Workload started with 30 W at a constant pedaling rate (60 revolutions · min−1) and was gradually increased by 30 W · 5 min−1. Five adjacent 60 s inter-beat (R-R) interval segments from the immediate recovery period (POST 1–5 at 30 W and 60 rpm) were each matched with their HR-corresponding 60 s-segments during the cycle test (PRE 1–5). An analysis of covariance was carried out with one repeated-measures factor (PRE vs. POST exhaustion), one between-subject factor (HIGH vs. LOW intensity) and respiration rate as covariate to test for significant effects (p < 0.050) on the natural log-transformed root mean square of successive differences between adjacent R-R intervals (lnRMSSD60s). Results: LnRMSSD60s was significantly affected by the interaction of experimental period × intensity [F(1, 242) = 30.233, p < 0.001, ηp2 = 0.111]. LnRMSSD60s was higher during PRE compared to POST at LOW intensity (1.6 ± 0.6 vs. 1.4 ± 0.6 ms; p < 0.001). In contrast, at HIGH intensity lnRMSSD60s was lower during PRE compared to POST (1.0 ± 0.4 vs. 1.2 ± 0.4 ms; p < 0.001). Conclusion: Identical net HR during cycling can result from distinct autonomic modulation patterns. Results suggest a pronounced sympathetic-parasympathetic coactivation immediately after the cessation of peak workload compared to HR-matched cycling before exhaustion at HIGH intensity. On the opposite, at LOW intensity cycling, a stronger coactivational cardiac autonomic modulation pattern occurs during PRE-exhaustion if compared to POST-exhaustion cycling. The different autonomic modes during these phases might be the result of different afferent and/or central inputs to the cardiovascular control centers in the brainstem.

P-42 Location analysis of healthy sport programs and their reachability – services for the adult public and their health care in rural areas

Background Physical inactivity is an independent risk factor for emergence and progression of chronic diseases. With regard to the negative consequences of physical inactivity, great efforts have been made to increase the physical activity among all age groups. Sport associations and statutory health insurances have therefore established the use of adequate instruments to support the process of “healthy ageing” (Guide of Prevention, §§ 20 und 20a SGB V). In this context, we investigated the healthcare system coverage of primary prevention sport offers (PS) in Westmecklenburg/GER. Methods Using ArcGIs (Fa. ESRI) we analysed several locations in the region of Westmecklenburg/GER and their reachability in detail. We developed cartographic data on the reachability by car and by public transport (ÖPNV) at different times of day. At the time of analysis (2013) a population of 474,005 inhabitants in Westmecklenburg/GER has been taken as a basis. To assess the quality of the public transport, accessibility was evaluated, when people have to leave the house at the latest to reach a sport location by public transport on time. On the way back, the earliest possible arrival time at home was determined when the route starts at the sport location. The travel times reflect the duration of the journey, including walking, waiting and transfer times. In general, for social and medical infrastructure, a maximum travel time of 30 min by public transport is acceptable (BMVI, 2015). For the accessibility by car, a period of 20 min is defined as reasonable travel time (BMVI, 2015). Result The ÖPNV reachability analysis showed difficulty to fairly reach the offered PS in this region. 50,5 % of the population need more than 60 min and 25,4 % need more than 90 min driving time to use a sport offer in the afternoon hours. Using the offered programs in the evening hours is also difficult: 31,1 % of the Westmecklenburg/GER population need more than two hours for the way back home (Figure 1). In case that any sport offers were available, major cities of Westmecklenburg/GER and its immediate surrounding provided an overall good ÖPNV and car reachability (Figure 2). Abstract P-42 Figure 1 Reachability by public transport in the evening, finish of sport service 7 pm: The figure shows the percentage of the population with arrival at home before 8 pm (travel time ≤ 60 min). Abstract P-42 Figure 2 Reachability by car of PS Discussion The results underline the necessity to further extend PS-offers. Both urban as well as rural areas lack a sufficient quantity of PS-offers. For health care in rural areas, it will be necessary in the future, not only to ensure a balanced distribution of physicians, but also the reachability by all health stakeholders. To establish permanent health sport offers, the establishment of regional networks should be promoted. Currently, sports clubs have an underestimated health potential which should be used. Acknowledgment The project was supported by the Federal Institute for Building, Urban Affairs and Spatial Development (BBSR). References Adler G, v.d. Knesebeck J-H. Ärztemangel und Ärztebedarf in Deutschland? Bundesgesundheitsblatt – Gesundheitsforsch – Gesundheitsschutz 2011;54:228–37. Available from: http://dx.doi.org/10.1007/s00103-010-1208-7 Greß S, Stegmüller K. Gesundheitliche Versorgung in Stadt und Land – Ein Zukunftskonzept. Friedrich-Ebert-Stiftung Hessen (Wiesbaden) 2011 Kuhlmey A. Versorgungsforschung zur angemessenen Gesundheitsversorgung im Alter. Bundesgesundheitsblatt – Gesundheitsforsch – Gesundheitsschutz 2011;54:915–21. Cirkel M, Juchelka R. Gesundheit und Mobilität im Alter. Public Health Forum 2007: 24–26. Giesel F, Köhler K, Nowossadeck E. Alt und immobil auf dem Land? Mobilitätseinschränkungen älterer Menschen vor dem Hintergrund einer zunehmend problematischen Gesundheitsversorgung in ländlichen Regionen. Bundesgesundheitsblatt – Gesundheitsforsch – Gesundheitsschutz 2013;56:1418–1424. Bundesministerium für Verkehr und digitale Infrastruktur (BMVI). Kennzahlen in der Daseinsvorsorge. 2015. Available from: http://nbn-resolving.de/urn:nbn:de:101:1-2015042703

P-59 Relationship between autonomic cardiac regulation at rest and indices of training load in recreational cyclists

Although cycling is one of the most popular aerobic exercises in competitive and non-competitive recreational sports, limited data exist regarding the acute physiological responses to a period of intensified training in recreational cyclists. Increases in training load typically occur, however in annual training camps. Thus, the aims of this observational field study were to (i) assess short-term autonomic, haematological and muscular responses to increased training load in recreational active male cyclists; and (ii) to elucidate, whether there is a correlation between autonomic response and indices of training load in this population. It was hypothesised, that an increase of aerobic training volume leads to significant elevations of serum creatine kinase (S-CK), increases in morning heart rate, and alterations of indices of heart rate variability (HRV). Methods: Heart rate (HR) and its variability (HRV), serum creatine kinase (S-CK) and hematocrit (Hct) were measured in the mornings before (PRE) and following three consecutive training days (POST 1-3). Daily cycling distance, altitude difference, maximum temperature of the day differed between the training sessions and were: 105 km, 1800 m, 26°C for training day 1; 122 km, 1700 m, 20°C for training day 2, and 80 km, 1900 m, 20°C for training day 3, respectively. Results: Morning HR significantly increased during the training period (PRE: 52.2±6.7 bpm, POST 1: 58.8±7.0 bpm POST 2: 58.5±8.1 bpm, POST 3: 57.9±7.2 bpm; F(3,33) = 11.182, p < 0.001, partial η2 = 0.554). While the parasympathetically modulated HRV high frequency power (HFP) decreased from PRE to POST 1-3, no significant effect was found for normalised low frequency power (LFP n.u.; PRE: 0.60±0.23, POST 1: 0.74±0.13, POST 2: 0.69±0.20, POST 3: 0.68±0.21; F(3,33) = 2.287, p = 0.101, partial η2 = 0.203), a measure reflecting sympathetic HR modulation. Hct showed a progressive decrease across measurement days (PRE: 49.9±4.0%, POST 1: 46.5±5.1%, POST 2: 45.5±3.8%, POST 3: 43.2±3.4%; F(3,33) = 11.909, p < 0.001, partial η2 = 0.520). Average S-CK increased after the training, with three subjects showing above reference values at POST 1 and 2 (PRE: 90.0±32.1 U/L, POST 2: 334.7±487.6 U/L, POST 3: 260.1±303.4 U/L, POST 3: 225.1±258.8 U/L; (F(3,33) = 3.996, p = 0.017, partial η2 = 0.285). S-CK leakage was significantly associated with HR (r=0.452, p=0.002) and HFP after night rest (r=-0.492, p<0.001). Conclusion: Three days of increased aerobic training volume can be associated with hemodilution, parasympathetic withdrawal and increases in muscular damage seromarkers in recreational cyclists. Despite cycling is thought to be an activity inducing no or only minor elevations in seromarkers of muscular damage (Noakes, 1987), an intensified training period increased S-CK in our sample of recreational cyclists. At POST 2 S-CK value tended to decrease, possibly due to a repeated bout effect (McHugh, 2003). Morning HR and its variability reflected larger alterations in training load in our study. Furthermore, S-CK, a marker of muscular damage and/or training load, was associated with alterations of HR-derived indices of autonomic control, a finding that has been previously reported by only a few investigators (Buchheit et al., 2011).