We investigated the influence of sport modalities in resting bradycardia and its mechanisms of control in highly trained athletes. In addition, the relationships between bradycardia mechanisms and cardiac structural adaptations were tested. Professional male athletes (13 runners, 11 cyclists) were evaluated. Heart rate (HR) was recorded at rest on beat-to-beat basis (ECG). Selective pharmacological blockade was performed with atropine and esmolol. Vagal effect, intrinsic heart rate (IHR), parasympathetic (n) and sympathetic (m) modulations, autonomic influence (AI) and autonomic balance (Abal) were calculated. Plasmatic norepinephrine (high-pressure liquid chromatography) and cardiac structural adaptations (echocardiography) were evaluated. Runners presented lower resting HR, higher vagal effect, parasympathetic modulation (n), AI and IHR than cyclists (P<0.05). Abal, sympathetic modulation (m) and norepinephrine level were similar within athletes regardless of modality. The cardiac chambers were also similar between runners and cyclists (P=0.30). However, cyclists displayed higher septum and posterior wall thickness than runners (P=0.04). Further analysis showed a trend towards inverse correlation between IHR with septum wall thickness and posterior wall thickness (P=0.056). Type of sport influences the resting bradycardia level and its mechanisms of control in professional athletes. Resting bradycardia in runners is mainly dependent on an autonomic mechanism. In contrast, a cyclist's resting bradycardia relies on a non-autonomic mechanism probably associated with combined eccentric and concentric hypertrophy.

Exercise intensity is a key parameter for exercise prescription but the optimal range for individuals with high cardiorespiratory fitness is unknown. The aims of this study were (1) to determine optimal heart rate ranges for men with high cardiorespiratory fitness based on percentages of maximal oxygen consumption (%VO(2max)) and reserve oxygen consumption (%VO(2reserve)) corresponding to the ventilatory threshold and respiratory compensation point, and (2) to verify the effect of advancing age on the exercise intensities. Maximal cardiorespiratory testing was performed on 210 trained men. Linear regression equations were calculated using paired data points between percentage of maximal heart rate (%HR(max)) and %VO(2max) and between percentage of heart rate reserve (%HRR) and %VO(2reserve) attained at each minute during the test. Values of %VO(2max) and %VO(2reserve) at the ventilatory threshold and respiratory compensation point were used to calculate the corresponding values of %HR(max) and %HRR, respectively. The ranges of exercise intensity in relation to the ventilatory threshold and respiratory compensation point were achieved at 78-93% of HR(max) and 70-93% of HRR, respectively. Although absolute heart rate decreased with advancing age, there were no age-related differences in %HR(max) and %HRR at the ventilatory thresholds. Thus, in men with high cardiorespiratory fitness, the ranges of exercise intensity based on %HR(max) and %HRR regarding ventilatory threshold were 78-93% and 70-93% respectively, and were not influenced by advancing age.

Introduction. The widely known electrocardiographic criteria for diagnosing left ventricular hypertrophy (LVH) use QRS complex voltages to define whether there is left ventricle enlargement or not. Mild myocardial hypertrophy is detected in many professional athletes and this is a consequence of their daily intensity of training. Thus it is not unusual that athlete’s ECGs show large QRS voltages with normal hearts. Objective. To evaluate the applicability of the usual electrocardiographic criteria for LVH - Sokolow-Lyon, Romhilt-Estes, Cornell and Gubner - in a population of professional athletes. Methods. The four LVH criteria for diagnosing LVH were applied to analyse ECGs of 107 professional athletes (71% soccer players, 29% marathonists, all male, age 25± 10 years, training for 9± 8 years) by the same observer unaware of echocardiographic results. ECG was considered to be indicative of LVH if: Sokolow-Lyon ≥35mm (V 1or 2 S wave+V 5or 6 R wave); Romhilt-Estes score ≥5 points (frontal plane: R or S waves ≥ 20mm, horizontal plane: R or S waves ≥ 30mm, Morris indices, V 5or 6 strain pattern, left axis deviation ≥ − 30°, intrinsecoid deflection ≥ 0.04s, QRS duration ≥ 0.10s) ; Cornell ≥ 28mm (aV L R wave + V 3 S wave); Gubner ≥ 22mm (D I R wave + D III S wave). Hypertrophy was considered whenever: LV diastolic diameter ≥ 60mm and/or septum ≥ 13mm and/or LV posterior wall ≥ 13mm. Kruskal-Wallis was used to statistically analyse quantitative variables, corrected chi-square test for categorical variables. Significance level: p ≤ 0.05. Results. Romhilt-Estes showed the best results (75% sensitivity, 84% specificity, 16 false-positives, 1 false-negative), and was the only criteria with statistical significance (p = 0.047). Sokolow-Lyon showed 100% sensitivity, 15% specificity, p = 0.545, 88% false-positives, 0% false-negative. Cornell and Gubner showed 25% and 0% sensitivity, 95% and 99% specificity, p=0.205 and p = 0.449, respectively. Conclusion. In this male population of professional athletes, Romhilt-Estes score proved to be the best criterion for identifying left ventricular hypertrophy, while Sokolow-Lyon criterion did not discriminate normal from abnormal hearts. Cornell and Gubner criteria should not be used in this population because of their low sensitivity.