Morphological differences of elite Croatian track-and-field athletes

In this study we present the morphological characteristics of 54 Croatian national level track-and-field athletes. 21 anthropometric body measures were taken on a sample of 15 sprinters (S), 16 endurance sprinters (S4), 10 middle-distance runners (MD) and 13 long-distance runners (LD). Body fat percentage, body mass index and somatotype were also calculated. Canonical discriminative analysis showed significant difference between the athletes of various running events, in the measures of body volume and body fat, while no significant difference was found in the variables of longitudinal and transversal dimensions of the skeleton. ANOVA and Student t-test for independent samples showed statistically significantly higher thigh and lower leg circumference in sprinters, as well as greater upper arm skinfold in middle-distance runners. The mesomorphic component is a dominant characteristic of somatotype of the runners in all events, whereas the ectomorphic component is the least marked.     

Ventilatory and heart rate chemosensitivity in track-and-field athletes

Fifty-four male track-and-field athletes and 18 male non-athletes were examined by isocapnic progressive hypoxia and CO2 rebreathing tests. Ventilatory and heart rate (HR) responses to hypoxia were analysed by a hyperbolic relationship and the ventilatory response to hypercapnia by a linear regression. The results showed that ventilatory sensitivity during hypoxia was significantly attenuated in the long-distance runners and sprinters compared to the non-athletes. Although heart rate sensitivity during hypoxia in none of the athletes showed a significant difference compared to that of the non-athletes, baseline HR in the long-distance runners was significantly lower than that of the non-athletes. None of the athletes showed significant differences in ventilatory sensitivity during hypercapnia compared to the non-athletes.     

Heart rate variability in weightlifters

On the basis of the literature and original data, heart rate variability (HRV) in weightlifters has been studied. The results showed that the distribution mode (a parameter of mathematical analysis that is equal to the most frequent length of RR intervals) indicates the intensity of physical exercise. Specific changes in the autonomic balance in athletes as dependent on their degree of training and sports qualification are important characteristics of adaptations to physical loads. For example, the degree of training of weightlifters is reflected by the level of the respiratory component as an index of the activity of the parasympathetic nervous system. Adaptation to physical exercise leads to an increase in the power of the spectrum of neurohumoral modulation and to changes in the ratio between the levels of the total spectral power of HRV.     

Heart rate variability analysis

The expansion of heart rate variability analysis has been facilitated by the remarkable development of computer sciences and digital signal processing during the last thirty years. The beat-to-beat fluctuation of the heart rate originates from the momentary summing of sympathetic and parasympathetic influences on the sinus node. According to the extensive associations of the autonomic nervous system, several factors affect heart rate and its variability such as posture, respiration frequency, age, gender, physical or mental load, pain, numerous disease conditions, and different drugs. Heart rate variability can be quantitatively measured by time domain and frequency domain methods that are detailed in the paper. Non-linear methods have not spread in the clinical practice yet. Various cardiovascular and other pathologies as well as different forms of mental and physical load are associated with altered heart rate variability offering the possibility of predicting disease outcome and assessing stress.     

Heart rate variability and sports

This article presents a review of the literature and some author’s data on the problem of using heart rate variability in sports and sports medicine practice.     

Heart rate variability analysis in general medicine

Autonomic nervous system plays an integral role in homeostasis. Autonomic modulation can frequently be altered in patients with cardiac disorders as well as in patients with other critical illnesses or injuries. Assessment of heart rate variability is based on analysis of consecutive normal R-R intervals and may provide quantitative information on the modulation of cardiac vagal and sympathetic nerve input. The hypothesis that depressed heart rate variability may occur over a broad range of illness and injury, and may inversely correlated with disease severity and outcome has been tested in various clinical settings over the last decade. This article reviews recent literature concerning the potential clinical implications and limitations of heart rate variability assessment in general medicine.     

Heart rate variability in normal and complicated pregnancies

The sympathetic division (SD) of the autonomic nervous system (ANS) was assessed by 23 tachometric parameters in 176 pregnant women using a Valenta medical diagnostic system. The activity of the ANS SD was shown to increase in the first trimester of pregnancy, progressively rise during the second and third trimesters, and decrease immediately before delivery. This is considered as a mechanism of adaptation to pregnancy. The activity of the ANS SD in pregnant women remained unchanged in mild gestosis; increased in moderate gestosis; and decreased in chronic hypertension, hypertensive circulatory disorders, and threatened preterm delivery. The role of the activity of the ANS SD in normal pregnancy and in obstetric complications is discussed.     

Jumping height in former elite athletes

To evaluate lower-limb explosive strength with respect to lifetime athletic activity, we measured vertical jumping height on a contact mat in former male runners (n = 28). soccer players (n = 31), weightlifters (n = 29) and shooters (n = 29) (age range 45 68 years). There were no statistically significant age-adjusted sport-group differences in jumping height, but differences by sport were evident among the subgroup of athletes without hip or knee osteoarthritis (n = 65) (P < 0.05). Thus, sports that increased jumping height also predisposed to lower-limb osteoarthritis. After adjustment for age and sport, the subjects without osteoarthritis jumped higher than those with osteoarthritis (n = 33) (P < 0.01). In a multiple linear regression analysis, age, reported hip and knee disability, and knee pain reduced jumping height. Hours spent in team-training during the past 12 months and the hours spent during their lifetime in power training were associated with improved vertical jumping height and together explained 41% of the difference among the subjects. The ability to jump even among athletes with hip or knee osteoarthritis would suggest that former elite athletes possess advanced lower limb muscle function.     

Heart rate variability in subjects with different respiratory rates

The variability of the cardiac rhythm was studied in males with different initial respiratory rates. At rest and during voluntarily controlled breathing, subjects with medium respiratory rates were found to have a less variable heart rate than their counterparts with low or high respiratory rates.     

Heart rate variability in healthy humans during night sleep

Polysomnography has been performed and heart rate variability has been studied during night sleep in healthy young subjects of both sexes. It has been shown that, on average, a shift in autonomic support towards parasympathicotonia occurs during sleep, with a maximum at stages III and IV of NREM sleep. At stage II of NREM sleep and during REM sleep, a short-term activation of the sympathetic nervous system comparable to wakefulness is observed.     

Heart rate variability and methylphenidate in children with ADHD

Although an extensive number of studies support the efficacy and tolerability of stimulants in the treatment of attention deficit/hyperactivity disorder (ADHD), in recent years, increasing concerns have been raised about their cardiovascular safety. We investigated whether a time domain analysis of heart rate variability (HRV) recordings in 24-h ECG under medication with stimulants yielded new information about therapy control in ADHD. We analysed the HRV parameter standard deviation of all normal sinus RR intervals over 24 h (SDNN), percentage of successive normal sinus RR intervals > 50 ms (pNN50) and root-mean-square of the successive normal sinus RR interval difference (rMSSD) from 23 children diagnosed by ADHD (19 boys and 4 girls), aged 10.5 ± 2.2 years, who were consecutively referred to our outpatient clinic for paediatric cardiology. Eleven children received medication with methylphenidate (MPH), while twelve children were initially examined without medication. Of these, eight probands were re-examined after therapy with MPH was established. Controls comprised 19 children (10 boys, 9 girls) from our Holter ECG data base without any cardiac or circulatory disease. Compared to healthy controls, the ADHD children with and without MPH treatment showed significantly higher mean heart rates (ADHD without MPH: 94.3 ± 2.2; ADHD with MPH: 90.5 ± 1.8, controls: 84.7 ± 1.8). pNN50 (ADHD without MPH: 6.5 ± 2.7; ADHD with MPH: 14.2 ± 6.9, controls: 21.5 ± 9.0) and rMSSD (ADHD without MPH: 26.1 ± 4.1; ADHD with MPH: 36.7 ± 8.3, controls: 44.5 ± 10.1) were lowest in ADHD children without MPH, middle in ADHD children with MPH and highest in controls. SDNN values were not significantly different. The hourly analysis shows highly significant reduced pNN50 and rMSSD values in untreated ADHD children between 5:00 pm and 6:00 am while the pattern approaches to levels of controls during MPH treatment. Data of this pilot study indicate a decreased vagal tone with significantly diminished HRV and higher heart rates in unmedicated ADHD children. These parameters of autonomic activation are ameliorated by MPH treatment. No evidence for negative impact of MPH on HRV was detected. Further studies will clarify a potential cardio-protective effect of MPH in ADHD.     

Changes in heart rate variability of athletes during a training camp.

Heart rate variability (HRV) reflects regulatory processes of the cardiovascular system and reveals fractal characteristics. In this paper we investigated standard HRV parameters and scaling characteristics in ten athletes before, during, and after a 2-week training camp to assess the effects of short-term overtraining on cardiovascular control. High-resolution ECGs were recorded over 30 min under resting conditions 1 week before the training camp, after 1 week of training in the camp, and after 3-4 days of recovery. Standard HRV analysis was performed according to Task Force recommendations. Scaling characteristics were assessed, applying detrended fluctuation analysis (DFA). Standard HRV analysis showed significant changes in meanNN and rmssd during the training camp. DFA revealed three distinct regions of scale-invariance and significant alterations during the training camp. In conclusion, HRV might be used to monitor the training state in athletes.     

Heart rate variability during long truck driving work

We recorded ambulatory electrocardiograms of 6 long distance truck drivers during their work period in order to observe the affect of autonomic nervous function and symptoms while doing their work. We also recorded their work patterns every minute. The RR50 value and the LFP/HFP ratio were calculated every two minutes based on R-R interval data. RR50 was significantly higher during taking naps than during other periods of work shifts, while, the LFP/HFP ratio showed significantly lower during taking naps than during other periods of work shifts. RR50 in the morning was significantly higher than that in the afternoon. On the contrary, the LFP/HFP ratio showed opposite tendency. Only on the times of driving, RR50 was significantly higher in the morning than that in the afternoon. On the other hand, the LFP/HFP ratio showed an opposite tendency. These results show that the parasympathetic nervous activities were more dominant than sympathetic nervous activities in the morning during the subjects were doing long distance truck driving including midnight work. Driving while in high parasympathetic nervous activity levels may add to cardiovascular stress and lead to drowsiness. And this may result in disrupted attention. It is necessary to decrease work time and improve working conditions of truck drivers working long-hour shifts.     

Increased p wave dispersion in elite athletes

Background

Few studies have been performed on P wave indices in athletes. The aim of this study was to determine the behaviour of maximum P wave duration (Pmax), minimum P wave duration (Pmin) and P wave dispersion (PWD) in young high performance athletes, as well as the relationship of PWD with training history, heart rate (HR) and echocardiographic parameters.

Methods

We performed a cross-sectional observational study in 38 athletes of high performance in sports: water polo, distance running and weight lifting compared with 34 sedentary controls.

Results

The average age in both groups was 20.6 years. Note that PWD was increased in athletes (57 ± 14 ms vs. 40 ± 12 ms, p <0.001) while Pmin was significantly lower (57 ± 13 ms vs. 72 ± 13 ms, p <0.001), and there was no difference when comparing Pmax (114 ± 9 ms vs. 117 ± 14 ms, p> 0.05). The correlation between the duration of training (r = 0.511) and resting HR (r = 0.461) with PWD was significant (p <0.01).

Conclusions

PWD is increased in young athletes of high performance and was positively correlated with duration of training and baseline HR. The increase in PWD was secondary to a significant decrease in Pmin.     

Central hemodynamic and heart rate variability parameters in athletes during different training programs

Central hemodynamic and heart rate variability (HRV) parameters were assessed in highly qualified athletes differing in the types of their training programs at relative rest. During endurance (the endurance group, n = 27) and strength (the strength group, n = 17) trainings, the total peripheral resistance (TPR) was decreased by 15% (p = 0.003) in the endurance group and by 16% (p = 0.011) in the strength group, and the stroke volume increased by 31% (p < 0.0001) in the endurance group and by 19% (p = 0.024) in the strength group. In the strength group, the cardiac output (Q) was higher (p = 0.012) and the temporal and spectral parameters of HRV (RMSSD, pNN ₅₀, and HF) were lower (p < 0.05) than those in the control group (n = 56). Some of these differences can be explained by an increased body mass index (p = 0.005) in the strength group. In the endurance group, the HRV parameters (RMSSD, pNN₅₀, HF, VLF, and TP) were higher (p ≤ 0.02), and the mean blood pressure was lower (p < 0.003) than those in the control group, with no significant differences in the Q from the control group. Our findings suggest that, in the strength-training athletes, resting hemodynamics were characterized by a greater Q level and a greater tension of mechanisms regulating cardiac activity. In the endurance-training athletes, a low Q level was associated with a lower tension of the mechanisms regulating cardiac activity (an increased vagal tone).