Night heart rate variability during overtraining in male endurance athletes

AIM: The purpose of the study was to examine whether an unaccustomed increase in training volume would result in characteristics changes in heart rate variability (HRV), in order to determine if this marker can be used to diagnose overtraining. METHODS: Nine experienced endurance athletes increased their usual amount of training by 100% within 4 weeks. Night ECG was recorded before (baseline) and after (OVER) this period of overload, and after 2 weeks of recovery (REC). RESULTS: We diagnosed overtraining in 6 subjects using both physiological and psychological criteria. No difference was noted in heart rate for night periods (56+/-12, 55+/-10 and 53+/-15 bpm, respectively; p>0.05). We found no significant changes of LF/HF (1.10+/-0.92, 0.96+/-0.57 and 0.59+/-0.43, respectively; p>0.05) or HF expressed in normalized units (54.81+/-20.12, 53.81+/-11.35 and 66.15+/-15.12%, respectively; p>0.05). CONCLUSION: In the conditions of the present study, HRV during sleep does not seem to be a valid marker of overtraining in male endurance athletes. Before concluding to the uselessness of this tool in the monitoring of the syndrome, longitudinal studies with elite or sub-elite athletes are needed to determine if spontaneously developed overtraining results in the same response.     

Physiological and performance responses to overtraining in elite judo athletes

To determine the effect of large and sudden increases in training volume on performance characteristics and the feasibility of using overtraining syndrome symptoms to monitor performance changes, 15 elite judo athletes were examined through 10 wk of training. Athletes performed their regular regimens of resistance (3 d.wk-1), interval (2 d.wk-1), and judo (5 d.wk-1) training in weeks 1-4. Interval and resistance training volumes increased by 50% in weeks 4-8 and returned to baseline in weeks 9-10. Judo training volume was unchanged in weeks 1-8 but increased by 100% in weeks 9-10. Assessments were made in weeks 2, 4, 8, and 10. Isokinetic strength of elbow and knee extensors and flexors increased significantly from weeks 2 to 4 (3-13%), was unchanged from weeks 4 to 8, and decreased significantly (6-12%) from weeks 4 to 10. Total time for 3 x 300 m intervals increased (P less than 0.05) between weeks 2 and 4 and between weeks 4 and 8, while total time for 5 x 50 m sprints decreased (P less than 0.05) from weeks 8 to 10 (less than 2%). Body fat percentage decreased (P less than 0.05) from weeks 2 to 10. Body weight, submaximal and maximal aerobic power, resting (sleeping) systolic and diastolic pressures, resting (sleeping) submaximal and maximal heart rates, exercising blood lactate levels, and vertical jump performance did not change significantly with increases in training volume. These results suggest that 6 wk of overtraining may affect some but not all aspects of performance and that performance may be affected before symptoms of the overtraining syndrome appear.     

320-detector row CT coronary angiography: effects of heart rate and heart rate variability on image quality, diagnostic accuracy and radiation exposure

Objectives

To evaluate the effects of heart rate and heart rate variability on image quality, patient dose and diagnostic accuracy of 320-detector row CT.

Methods

94 patients were prospectively enrolled. Heart rate was defined as the mean value of different intervals elapsing between two consecutive R waves in an electrocardiogram (R–R intervals) and the heart rate variability was calculated as the standard deviation from the average heart rate. The image quality was evaluated by four grades, according to motion artefacts (“step artefacts” and “blurring artefacts”). The diagnostic accuracy was analysed in 43 patients who were scheduled for invasive coronary angiography (ICA). The coeffects of heart rate and heart rate variability on image quality, radiation dose and diagnostic accuracy were evaluated by multivariate regression.

Results

The mean image quality score was 1.2±0.5 and the mean effective dose was 14.8±9.8 mSv. The results showed that heart rate (74.0±11.2 beats per minute) was the single factor influencing image quality (p<0.001) and radiation dose (p<0.001), while heart rate variability (3.7±4.6) had no significant effect on them (p=0.16 and p=0.47, respectively). For 43 patients who underwent ICA, heart rate and heart rate variability showed no influence on the accuracy (p=0.17 and p=0.12, respectively). Overall sensitivity was 97.4% (37/38), specificity was 99.4% (351/353), positive predictive value was 94.9% (37/39) and negative predictive value was 99.7% (351/352).

Conclusion

320-detector row CT, with improved longitudinal coverage of detector, resolves step artefact and high patient dose caused by irregular heart rate. However, it is still recommended to control heart rate to a lower level to eliminate blurring artefact and radiation dose.As the clinical application of 4-detector CT to scan the coronary arteries by a non-invasive procedure, CT coronary angiography has emerged as an attractive, diagnostic modality for detecting coronary artery disease. However, motion artefact by rapid movement throughout the cardiac cycle and blooming artefact caused by calcified plaque represent the major challenges for artefact-free coronary CT angiography. Generally, “step artefacts” and “blurring artefacts” are two kinds of motion artefact influencing the quality of coronary artery image. To improve image quality, CT scanners with higher spatial resolution, temporal resolution and wider detector array were developed.The Discovery™ CT750 HD (GE Healthcare, Waukesha, WI) improves spatial resolution and decreased calcium blooming artefact significantly [1]. Dual-source CT (DSCT), with two X-ray sources and a temporal resolution of 83 ms, has improved blurring artefacts caused by high heart rate (HR) [2-4]. Nevertheless, as the coverage of the detectors is limited, step artefacts caused by heart rate variability (HRv) is still an inverse factor influencing the image quality [2,3]. Just as the improved temporal resolution should resolve the problem of high HR, the longitudinal coverage of the detector should be expanded further to resolve the influence of HRv [5-8]. 320-detector row dynamic volume CT (DVCT) can cover the whole heart within one heartbeat, which enables DVCT to have the potential to resolve the impact of HRv [9].A previous study has shown that DVCT reliably provides high diagnostic accuracy without HR control [9]. The aim of our study was to evaluate the influence of degree of HR and HRv on image quality, radiation dose and diagnostic accuracy in patients undergoing DVCT.     

平均心率、心率波动和心率变异性对双源CT冠状动脉影像质量影响的研究

目的：评价平均心率、心率波动和心率变异性对双源CT冠状动脉影像质量的影响。方法：100例患者进行了双源CT冠状动脉血管成像。原始数据经多期相重建优选出最佳收缩期和舒张期影像,以4分法评定系统进行影像质量评价。利用Pearson相关分析评价平均心率、心率波动和心率变异性对冠状动脉的影像质量的影响,对有相关性者行进一步分析。结果：100例患者,共纳入分析的血管为299支,296支血管可满足影像评价（99％）。平均心率、心率波动和心率变异性对总的冠状动脉影像质量没有影响,仅平均心率对舒张期冠状动脉影像质量有负影响（P〉0．05）,尤其对右冠状动脉的影响更明显,70bpm以上时影像质量即下降,80bpm以上时影像质量甚至难以满足评价。结论：平均心率、心率波动和心率变异性对双源cr冠状动脉总的影像质量没有影响,但平均心率对舒张期冠状动脉的影像质量有负影响,对右冠状动脉的影响更大,当心率大于80bpm时,利用舒张期的数据难以获得RCA满意的影像质量,应该利用最佳收缩期的数据进行影像重组。     

Altitude, heart rate variability and aerobic capacities

We analyzed the relationship between aerobic capacities and changes in heart rate variability (HRV) in Nordic-skiers during living high-training low (Hi-Lo). Eleven skiers trained for 18 days at 1200 m, sleeping at 1200 m (LL, n = 5) or in hypoxic rooms (HL, n = 6, 3 x 6 days at altitudes of 2500 - 3000 - 3500 m, 11 h . day (-1)). Measurements were performed before, during and two weeks after Hi-Lo. VO(2max), peak power output were not improved in HL nor in LL, whereas VO(2) and power at the respiratory compensation point (VO(2RCP) and PRCP) increased by 7.5 % and 5.0 % only in HL. Significant changes in HRV occurred only in LL, in the standing position, including a 30 % (p < 0.05) increase in resting heart rate (HR), a 50 % (p < 0.05) decrease in total spectral power (TP) and a 77 % (p < 0.05) decrease in high frequency activity (HF). When all the subjects were pooled, the changes in HRV in the supine position were correlated to the changes in aerobic capacities, i.e., HF, LF and TP were correlated to VO(2RCP) and HR, HF and TP were correlated to PRCP. This study confirms the relationship between HRV and changes in aerobic capacity, therefore highlighting the potential value of HRV for monitoring altitude training adaptations.     

Physiological and performance adaptations to an in-season soccer camp in the heat: associations with heart rate and heart rate variability

The aim of the present study was to examine the associations between adaptive responses to an in‐season soccer training camp in the heat and changes in submaximal exercising heart rate (HRex, 5‐min run at 9 km/h), postexercise HR recovery (HRR) and HR variability (HRV). Fifteen well‐trained but non‐heat‐acclimatized male adult players performed a training week in Qatar (34.6 ± 1.9°C wet bulb globe temperature). HRex, HRR, HRV (i.e. the standard deviation of instantaneous beat‐to‐beat R–R interval variability measured from Poincaré plots SD1, a vagal‐related index), creatine kinase (CK) activity, plasma volume (PV) changes, and post‐5‐min run rate of perceived exertion (RPE) were collected at six occasions in temperate environmental conditions (22°C). Players also performed the yo‐yo intermittent recovery test level 1 (Yo‐Yo IR1) in the same environmental conditions (22°C), both at the beginning and at the end of the training week. Throughout the intervention, HRex and HRV showed decreasing (P < 0.001) and increasing (P < 0.001) trends, respectively, while HRR remained unaffected (P = 0.84). Changes in HRex [?0.52, 90% confidence limits (?0.64; ?0.38), P < 0.001] and SD1 [0.35 (0.19; 0.49), P < 0.001] were correlated with those in PV. There was no change in RPE (P = 0.92), while CK varied according to training contents (P < 0.001), without association with HR‐derived measures. Yo‐Yo IR1 performance increased by 7 ± 9% (P = 0.009), which was correlated with changes in HRex [?0.64 (?0.84; ?0.28), P = 0.01]. In conclusion, we found that an in‐season soccer training camp in the heat can significantly improve PV and soccer‐specific physical performance; both of which are associated with changes in HRex during a 5‐min submaximal run.     

Heart rate and blood pressure variability during heavy training and overtraining in the female athlete

We investigated heavy training- and overtraining-induced changes in heart rate and blood pressure variability during supine rest and in response to head-up tilt in female endurance athletes. Nine young female experimental athletes (ETG) increased their training volume at the intensity of 70-90% of maximal oxygen uptake (VO2max) by 125% and training volume at the intensity of < 70% of VO2max by 100% during 6-9 weeks. The corresponding increases in 6 female control athletes were 5% and 10%. The VO2max of the ETG and the control athletes did not change, but it decreased from 53.0 +/- 2.2 ml x kg(-1) x min(-1) to 50.2 +/- 2.3 ml x kg(-1) x min(-1) (mean+/-SEM, p < 0.01) in five overtrained experimental athletes. In the ETG, low-frequency power of R-R interval (RRI) variability during supine rest increased from 6 +/- 1 ms2 x 10(2) to 9 +/- 2 ms2 x 10(2) (p < 0.05). The 30/15 index (= RRI(max 30)/RRI(min 15), where RRI(max 30) denotes the longest RRI close to the 30th RRI and RRI(min 15) denotes the shortest RRI close to the 15th RRI after assuming upright position in the head-up tilt test), decreased as a result of training (analysis of variance, p = 0.05). In the ETG, changes in VO2max were related to the changes in total power of RRI variability during standing (r = 0.74, p < 0.05). Heart rate response to prolonged standing after head-up tilt was either accentuated or attenuated in the overtrained athletes as compared to the normal training state. We conclude that heavy training could increase cardiac sympathetic modulation during supine rest and attenuated biphasic baroreflex-mediated response appearing just after shifting to an upright position. Heavy-training-/overtraining-induced decrease in maximal aerobic power was related to decreased heart rate variability during standing. Physiological responses to overtraining were individual.     

雷达作业人员昼夜不同作业班次心率和心率变异性的变化

目的 观察雷达作业人员作业过程中心率和心率变异性的昼夜节律变化.方法 以某雷达部队21名男性雷达作业人员为对象,于昼夜不同作业班次（上午班、下午班、小夜班和大夜班）上班前佩带＂飞行员飞行生理参数记录检测仪＂,检测工作过程中动态心电图、心率等指标,分析有关心率变异性参数的变化.此外,将每一作业班次分为4个时段,比较同一班次不同时段平均心率的变化.结果 雷达作业过程中不同班次的平均心率有统计学差异（F=7.287,P＜0.01）,大夜班的平均心率较上午班、下午班、小夜班均明显降低（P＜0.01）;大夜班的标化低频功率较上午班、下午班明显降低（P＜0.05）,而标化高频功率较上午班、下午班显著增加（P＜0.05）.上午班、下午班和小夜班不同时段的平均心率均有统计学差异（F=5.480、3.150、3.850,P＜0.05或P＜0.01）,而且均呈现随着作业时间延长,平均心率逐渐降低的趋势;但大夜班中各时段间的平均心率无统计学差异.结论 生物节律的变化对雷达作业人员的心率和有关心率变异性指标产生明显影响.     

雷达作业人员昼夜不同作业班次心率和心率变异性的变化

Objective To investigate the circadian changes of heart rate (HR) and heart rate variability (HRV) on radar operators in day and night shifts. Methods Twenty-one military radar operators were selected as subject. Their HR was gotten from continually electrocardiogram recorded by a biomedical monitoring system in four different working shifts (morning, afternoon, early night and late night) and HRV was analyzed. In addition, each shift was divided into four phases and the average HR of different phases in same shift was compared. Results There was significant difference of average HR among four shifts (F=7. 287, P＜0.01). The average HR in late night was significantly lower than that in other three shifts. Comparing with morning and afternoon shifts, high frequency normalized unit (HFNU) in late night shift was significantly increased (P＜0.05). Low frequency normalized unit (LFNU) in late night shift was significantly decreased comparing with those in morning and afternoon shifts (P＜0. 05). The average HR in different phase of a shift showed significant differences among morning, afternoon and early night shifts (F= 5. 480, 3. 150, 3. 850,P＜0. 05 or P＜0. 01), and gradually decreased with working time. However, there was no significant difference of average HR in different working phase of late night shift. Conclusions Circadian change would significantly influence the HR and some HRV indices of military radar operators.     

高气压变化对年轻飞行员心率及短程心率变异性的影响

目的 探讨高气压变化对年轻飞行员心率(HR)及短程心率变异性(HRV)的影响.方法 利用高压舱结合动态心电图对30名年轻飞行员进行临床试验,记录升压前、升压过程中、高压状态、减压过程中及减压后各5 min的平均HR及所有正常R-R间期标准差(SDNN)、相邻正常R-R间期差值均方根(RMSSD)、相邻R-R间期差异大于50 ms的百分数(PNN_(50))3项短程HRV时域指标,并进行统计学处理.结果 气压升高可使HR减慢,升压前76.56±12.33次/min,升压过程中67.25±10.21次/min,高压状态65.06±7.02次/min;随着大气压的恢复,HR逐渐加快,但未恢复到升压前水平;主要反映交感和迷走神经总张力的HRV指标SDNN和主要反映迷走神经张力的RMSSD、PNN_(50)基本上随着环境大气压升高而升高,随着大气压降低而降低.结论 高气压的变化对年轻飞行员的HR和短程HRV有较明显的影响,在飞行员的选拔和训练时应予以重视.     

Effect of immersion, submersion, and scuba diving on heart rate variability

BACKGROUND: Heart rate variability (HRV) describes the cyclic variations in heart rate and offers a non-invasive tool for investigating the modulatory effects of neural mechanisms elicited by the autonomic nervous system on intrinsic heart rate. OBJECTIVE: To introduce the HRV concept to healthy volunteers under control conditions and during scuba diving. In contrast with more established manoeuvres, diving probably activates both the sympathetic and parasympathetic nervous system through various stimuli-for example, through cardiac stretch receptors, respiration pattern, psychological stress, and diving reflex. A further aim of the study was to introduce a measure for determining a candidate's ability to scuba dive by providing (a) standard values for HRV measures (three from the time domain and three from the frequency domain) and (b) physiological responses to a strenuous manoeuvre such as scuba diving. METHODS: Twenty five trained scuba divers were investigated while diving under pool conditions (27 degrees C) after the effects of head out immersion and submersion on HRV had been studied. RESULTS AND CONCLUSIONS: (a) Immersion under pool conditions is a powerful stimulus for both the sympathetic and parasympathetic nervous system. (b) As neither the heart rate nor the HRV changed on going from immersion to submersion, the parasympathetic activation was probably due to haemodynamic alterations. (c) All HRV measures showed an increase in the parasympathetic activity. (d) If a physiological HRV is a mechanism for providing adaptability and flexibility, diving should not provoke circulatory problems in healthy subjects. (e) Either a lower than normal HRV under control conditions or a reduction in HRV induced by diving would be unphysiological, and a scuba diving candidate showing such characteristics should be further investigated.     

64排CT冠状动脉造影:心率及心率变化对图像质量的影响

目的:探讨患者心率、心率变化对64排CT冠脉图像质量的影响。方法:前瞻性分析86例64排CT冠脉造影的患者,在20%～80%R-R间期、间隔5%重组原始数据,分别选择冠状动脉各主干最佳重建时相,评估冠脉各节段的图像质量。计算患者平均心率和扫描过程中心率变化。采用Person相关检验比较平均心率、心率变化与图像质量的相关性。结果:82例患者的平均心率为65.3±12.9,心率变化为3.2±2.1,52(63.4%)例服用β受体阻滞剂患者的平均心率为64.9±13.8,心率变化为2.6±1.4;30(36.6%)例未服用β受体阻滞剂患者的平均心率为65.8±12.3,心率变化为4.6±2.1,二者相比有显著性差异(P<0.05)。82例患者共有1198冠脉节段被评估,1167(97.4%)节段可用于诊断。患者平均心率与冠脉总体及RCA、LM和LAD、LCX图像质量无明显相关性(r=0.22,0.15,0.16,0.24,P=0.05)。扫描期间心率变化与冠脉总体图像质量有显著相关性(r=0.75,P=0.001),与RCA、LCX、LAD和LM图像质量均有相关性(P<0.001),相关程度依次为RCA(r=0.77)、LCX(r=0.69)、LAD和LM(r=0.68)。结论:在心率较快的条件下,64排CT冠脉图像质量明显提高,扫描过程中心率变化可显著影响冠脉图像质量,服用β受体阻滞剂可明显降低心率变化幅度,从而提高冠脉图像质量。     

Effect of aerobic training on orthostatic tolerance, circulatory response, and heart rate dynamics.

BACKGROUND: This study was performed to investigate the effects of aerobic training on orthostatic tolerance and to quantify the post-training changes in cardiovascular response and heart rate variability (HRV). METHODS: Tolerance and circulatory responses to two types of lower body negative pressure (LBNP) were examined and compared in a group of healthy male students before and after 6 mo of aerobic training, and the results were further compared with a group of athletes (runners). Changes in HRV associated with training were analyzed by conventional and time-varying autoregressive spectral analysis, as well as by approximate entropy measurement (ApEn)--a statistic quantifying heart rate "complexity" derived from non-linear dynamics. RESULTS: After aerobic training, there was an initial transient hypotension during the supine -50 mmHg LBNP testing and a significant decrease in tolerance to upright graded LBNP in most of the student-subjects. Moreover, after training, there was a significant decrease in ApEn value of the HRV time series during both supine control and LBNP testing, and the rate of cardiac vagal withdrawal and sympathetic activation during the onset of LBNP was faster than that before training. CONCLUSIONS: The present study has provided further evidence that certain types of aerobic training may affect orthostatic tolerance and may be associated with a loss of complexity of HRV during supine resting and orthostatic stress.     

Effects of exercise on heart rate variability: inferences from meta-analysis

INTRODUCTION: Chronic exercise training produces a resting bradycardia that is thought to be due partly to enhanced vagal modulation. PURPOSE: The aim of the present study was to determine the effects of exercise training on heart rate and measures of heart rate variability associated with vagal cardiac modulation and to quantify the relationship between changes in these measures. METHODS: A random effects model of effect size (d) for change in high frequency (HF) power and RR interval was calculated. Within-group heterogeneity was assessed using the Q statistic. Where heterogenous effects were found, subgroup analyses were performed using the between-group Q statistic. RESULTS: A meta-analysis of 13 studies measuring HF (N=322 cases) produced an overall effect size of d=0.48 (C.I. 0.26-0.70, P=0.00003). Twelve studies (298 cases) reported a change in RR interval with an overall effect size of d=0.75 (C.I. 0.51-0.96, P<0.00001). Effect sizes for RR interval data were significantly heterogenous. Subgroup analysis revealed significantly smaller responses of RR interval to training in older subjects (P<0.1). Effect sizes for change in HF were homogenous, although a trend toward an attenuated response to training was exhibited in older subjects (P>0.10). Linear, quadratic, and cubic fits all revealed weak (P>0.05) relationships between effect sizes for change in HF and RR interval. DISCUSSION: Exercise training results in significant increases in RR interval and HF power. These changes are influenced by study population age. The smaller effect size for HF and weak relationship between HF and RR interval suggest factors additional to increased vagal modulation are responsible for training bradycardia.