Cardiovascular  modifications  in  long-distance athletes  from  Villa  Clara  during  the  2018-2019 macro-training cycle

Abstract

A descriptive longitudinal section study was carried out with the objective of describing the  electrocardiographic  and  echocardiographic  cardiovascular  modifications  in different stages of the preparation of a macro-training cycle, in the seven long distance runners  of  the  Villa  Clara  school  category.  It  is  concluded  that  training  produces cardiac  morphological  and  functional  adaptations  that  are  manifested  through electrocardiographic findings such as bradycardia and sinus arrhythmia; in addition to modifications  of  echocardiographic  variables  such  as  the  thickness  of  the interventricular septum and the posterior wall of the left ventricle that show values close to the upper limit of normality and diastolic diameter of the left ventricle with low mean values during all training stages, which contributes at a high h / r ratio in most athletes. The ejection volume and the ejection volume index maintain values lower than those considered normal during the training stages, which leads to the suggestion that there is an increase in work intensities throughout the macrocycle and a marked deficit of aerobic capacity. This suggests not having made adjustments to training loads and neglecting basic aerobic work during the preparatory period.

Keywords: cardiovascular modifications, macrocycle, training, background

Introduction

Since the XIX century, it has been proposed that both prolonged and intense physical exercise  and  systematic  sports  training  can  produce  acute  changes  (responses)  and chronic changes (adaptations) of the cardiovascular system, directly related to the type, duration and intensity of training and to the years of sports practice (Semsarian, 2015). Its clinical expression depends on genetic, metabolic, humoral factors and to a great extent  on  the  type  of  training;  which  has  been  a  source  of  interest  for  coaches, physiologists and doctors, both in the search to know its impact on health, as well as on the performance of athletes (Thompson, 2016).

Myocardial electrical and structural changes with a moderately increased mass and high work capacity caused by repeated cardiac overload induced by regular exercise and which does not present any valvular abnormality or other serious disorder in addition to being determined by various factors, come to configure an entity of its own: the heart of the athlete, according to several authors, including (Velarde, 2016).

The training typical of sports with a predominance of dynamic and resistance exercise induces morphological and functional cardiovascular adaptations: decrease in heart rate, increase in the volume of the cavities, the thickness of the wall thicknesses, increase in the stroke volume and the capacity to dilation of the heart (Yáñez, 2016).

In Cuba there are investigations in various sports in which the structural and functional findings of the heart are related to the stages of sports preparation, where the different functional  directions  of  the  loads  are  taken  into  account  and  knowledge  of  the modifications of the electrocardiographic variables is achieved. and echocardiography that express the cardiovascular adaptations that occur during the progression of training in the different stages of the preparatory period in the sports studied (Rabassa, 2009). (Silva, Portela, Pujadas and Medina, 2017). (Berovides, 2016).

In the province of Villa Clara, with the intention of supporting the control of sports training, studies have been carried out in several sports in recent years, where other echocardiographic variables that appear less frequently in the reviewed literature but with  high  and  novel  criteria  are  also  exposed.  Among  these  diagnoses  are:  left ventricular concentric hypertrophy indices, asymmetric septal hypertrophy, h / r index, ejection  volume  index,  cardiac  output  index  and  myocardial  mass  index  (Rabassa, 2009). (Rabassa, 2011).

All of the above, together with the background of the scarce cardiovascular profile investigations in long-distance athletics in the early initiation stage, named in Cuba as a school  category,  are  elements  that  have  been  taken  into  account  to  study  the characteristics of the heart in long-distance runners. of these ages in the province of Villa Clara, using highly reliable measurements to know the state of the cardiovascular system of athletes so young in this sport and provide information for teachers, doctors and  athletes  in  order  to  achieve  adequate  control  biomedical  training,  disease prevention, quality of life improvements and sports performance.

The objective of the work is to describe the electrocardiographic and echocardiographic cardiovascular modifications in different stages of the preparation of a macro-training cycle, in the long-distance athletes of the Villa Clara school category.

Methodology

A descriptive study of longitudinal section was carried out on the entire population of athletes, of both sexes, from the school category endurance team of the “Héctor Ruiz” Sports Initiation School (SIS) in Villa Clara. Of the seven athletes, four are male and three female, with an average chronological age of 12.7 years and a sporting age of 3.1 years respectively.

An exhaustive cardiovascular physical examination, weight and height were carried out to calculate the body surface; as well as the electrocardiogram and echocardiogram at rest  in  the  three  moments  of  sports  preparation:  beginning  and  end  of  general preparation (GPS, GPE) and end of special preparation (SPE) always in the morning, without having trained that day nor having received heavy training loads the day before. The  general  variables  studied  were  chronological  age  and  sports  age; Electrocardiographic:  the  electrocardiograms  were  reviewed  according  to  the established methodology for their interpretation and the findings found were described as variables and finally the echocardiographic variables, those considered fundamental for the echocardiographic control of the influence of physical loads were used with the premise  of  the  existence  of  normal  systolic  and  diastolic  functions:  interventricular septum  in  diastole  (ISd),  posterior  wall  of  the  left  ventricle  in  diastole(LVPWd), diastolic diameter of the left ventricle (DDLV), ejection volume or stroke volume (EV), h / r index (I h / r), stroke volume or stroke volume index (SVI).

Operational definition of the last echocardiographic variables studied and that are not commonly described when echocardiograms are performed:

1. h / r index: It is calculated through the formula:

h / r index=ISd + LVPWd

DDLV  

Where “h” is equal to the sum of the thickness of the interventricular septum and the posterior wall of the left ventricle, both measured in diastole; the “r” is the diastolic diameter of the left ventricle.

Measurement indicators: The values accepted as normal or balanced in young adult athletes and that are an expression of a metabolically balanced work (aerobic-anaerobic) is between 0.32 and 0.40 (ideal between 0.34 and 0.36) ( Rabassa, 2009). (Berovides, 2016).

2. Volume of ejection index (VEI)

VEI = VE / SC 

Where VE: stroke volume or stroke volume.

 VEI: ≥ 50 ml / beat / m2, it is considered an indicator of good aerobic capacity.

For the statistical processing of the information, the spreadsheet in  Microsoft Excel 2010 was used, which allowed to summarize and process the collected data and reflect them in tables for their adequate interpretation.

Results and Discussion

Table 1. Heart Rate in the training stages.

Training Stages  

 Heart rate  GPS  GPE  SPE

Nro. %  Nro. %  Nro. %

Source: Clinical history.BGP: beginning of general preparation,,EGP: end of general preparation,,ESP: end of special preparation

42.8% of the athletes had a sinus rhythm that is normal, 57.2% presented modifications in the heart rhythm because 4 of 7 athletes maintained some type of change in any of the 3 stages of training, the respiratory-type sinus arrhythmia, sinus bradycardia and sinus tachyarrhythmia were found.

Table 2. Values of the electrocardiographic variables: Heart rate and PR interval. Heart rate(I/mto)  IntervalPR(seg)

Variables  Stages   Stages

Source: Clinical history. l / mto: beats per minute, sec: seconds.

In Table 2, when analyzing the heart rate, it is observed that 4 athletes (57.2%) of the population presented values that ranged between 61 and 79 l / m in all stages and 2 cases (28.6%) showed heart rate between 57 and 60 l / mt, expected values in athletes with a mean sporting age of 3.1 years (between low normal and sinus bradycardia). Finally, one athlete (14.3%) in the three stages showed heart rate values above 100 l / mt.  In  the  case  of  the  PR  interval,  the  mean  value  of  this  variable  in  the  studied population agrees in the three moments with values considered normal, except for one athlete who represented 14.3% presented lengthening in its duration corresponding to atrioventricular block first grade.

Table 3. Values of the electrocardiographic variables: QRS complex and QTc interval. ComplexQRS(seg)  IntervalQTc (mseg)

Variables  Stages

Stages

Source:  Clinical  history.  msec:  milliseconds,  GPS:  general  preparation  start,GPE:  general  preparation  end,SPE: special preparation end.

In Table 3, it can be seen that the seven athletes studied maintained values within the normal range for the QRS Complex and QTc variables during the three stages analyzed with means during the macrocycle of 0.06 sec and 365 msec, respectively.

Table 4. Ventricular repolarization in the training stages. Training Stages

Ventricular Repolarization

GPS  GPE  SPE

Source: Clinical history.

Table 4 describes the presence or absence of ventricular repolarization disorders, it was observed that 4 of the 7 athletes presented ventricular repolarization disorders in the three  stages  evaluated,  which  represented  57.1%  of  the  total  sample  in  study;  the inverted T wave and the flattened T wave were the alterations found considered minor disorders of ventricular repolarization.

Table  5.  Values  of  the  echocardiographic  variables:  interventricular  septum,  posterior  wall,  diastolic diameter and h / r index.

Variables  IVSd(mm)  PWLVd(mm)  DDLV (mm)  Índex h/r

Athletes  Stages  Stages  Stages  Stages

GPS  GPE  SPE  GPS  GPE  SPE  GPS  GPE  SPE  GPS  GPE  SPE

IVSd: Interventricular septum in diastole. PWLVd: posterior wall of the left ventricle in diastole, DDLV: diastolic diameter of the left ventricle, EV: ejection volume or stroke volume. mm: millimeters

Table 5 shows echocardiographic variables and it is observed that the mean of the equipment for the three stages, regarding the values of the interventricular septum and the posterior wall of the left ventricle, showed a slight tendency to the upper limit, especially in the values of the interventricular septum; an athlete 14.3% of the sample presented in the measurements of the interventricular septum in most of the moments evaluated figures above those considered normal for athletes of these ages.

Regarding the diastolic diameter of the left ventricle, 3 athletes (42.8%) presented in the three  stages,  values  lower  than  those  considered  normal,  there  was  a  collective inclination of the team to low measurements during all moments, evident in the mean of the macrocycle for this variable.

This trend towards high values of the interventricular septum and the posterior wall of the left ventricle and low values of the diastolic diameter of the left ventricle contributed to a high h / r index where 71.4% of all athletes exceeded the maximum values.

Table 6. Values of the echocardiographic variables: Ejection volume and ejection volume index.

             EV (ml/latido)  EVI (ml/latido/m2) Variables  

Stages  Stages

Athletes  GPS  GPE  SPE  GPS

Average  58  62.1  59.6  43.2 Average Macrocycle

59,9  43,5

Ml: milliliters, m2: square meter

When analyzing table 6, related to the ejection volume, it is shown that the team showed an average of 59.9 ml / beat, lower than what was established and expected for each stage, with 4 athletes from the study population 57.2 % who showed values lower than normal (65-80ml / beat). Regarding the ejection volume index, in a similar way, 5 athletes 71.4% of the total presented figures lower than desired in each preparation stage.

Table 1 shows that 4 athletes (57.2%) presented some type of heart rhythm disorder from the beginning of the general preparation, with the same results at the end of the special  preparation,  and  the  respiratory-type  sinus  arrhythmia  is  specified.  Sinus

bradycardia  and  sinus  tachyarrhythmia  such  as  those  detected,  elements  that  are common at this age, of which sinus bradycardia is an adaptation of endurance sports and is only detected in a male athlete with 5 years in the practice of this sport, being present from the beginning of the general preparation. These findings do not coincide with those described by Corrado (2012), who in his studies describe such significant values of  sinus  bradycardia  for  heart  rate  in  long-distance  athletes  of  45-50  beats.  /  mto accompanied by a marked sinus arrhythmia, usually respiratory in nature.

Reflected in table 2, the heart rate values were evaluated in different training stages, not finding the expected decrease in the same as the training progressed, since only 1 athlete (14.3%)  presented  heart  rate  values  below  of  60  beats  per  minute  in  all  stages  of training.  However,  the  authors  themselves  described  in  the  previous  paragraph, observed a decrease in baseline heart rate values in a group of young people after a 12- week training program.

Other studies carried out in the last 40 years with resting electrocardiograms in athletes describe a great variety of alterations attributable to sports training, particularly aerobic ones with increased vagal tone, the most frequent being sinus bradycardia between 50 and  85%  of  cases,  sometimes  with  a  frequency  of  less  than  40  beats  per  minute (Fernández, 2015).

Wasfy et al. (2015) presented the electrocardiographic findings in 330 rowing athletes, of which 94% of them had one or more electrocardiographic patterns related to training, 51% of these were related to sinus bradycardia. Lower percentages were found in the research presented.

Regarding  the  PR  interval  in  this  table,  one  athlete  (14.3%)  developed  first  degree atrioventricular  conduction  disorder,  which  is  similar  to  the  results  of  Zehender Kaplinsky, Yahini, Hanne-Papro and Neufeld (1975) who found an incidence of first- degree atrioventricular block between 10% and 33% in similar studies.

Serra-Grima  (2016)  points  out  that  the  effect  of  training  produces  changes  in  the function  of  the  atrioventricular  node  due  to  increased  vagal  tone,  first  degree atrioventricular block can occur in 33% of athletes, while second degree atrioventricular block degree is less frequent, and usually does not reach 1%. In the same way, the mean values described in this research are similar to those referred by Mathur (2018) who exposes an average of the PR interval of 0.16 seconds plus minus 0.01 seconds in sprinters and 0.18 plus minus 0.02 seconds in long distance runners.

In athletes, it is common to find discrete alterations in the duration and morphology of the QRS, when performing the analysis of the QRS complex described in the study and shown in Table 3, it was observed that the duration of the same in the different training stages was within normal values. When describing the morphology, the presence of incomplete  blockage  of  the  right  bundle  of  the  Hiss  bundle  was  evidenced  in  two athletes, which represents 28.6% of the sample, the latter finding described as frequent in athletes at an early age of life (Uberoi , 2012).

Other investigations show nonspecific intraventricular conduction disorders with dented QRS in V1 (Fernández, 2015). (Wasfy et al., 2015).

Regarding the duration of the QRS complex, he partially agrees with Pérez (2004) who in his study showed a QRS of 0.09 plus minus 0.02 seconds without changes in the complex's  morphology,  in  the  same  way  Hernández  O  (2002)  found  QRS  with  an average duration of 0.06 seconds, not referring to other abnormalities.

In the results reflected in Table 3 of this study, all the athletes presented a normal QTc interval, similar to Peidro (2015) who, in his review article on the athlete's heart, states that the QTc interval is normal in the athlete. In general, the athlete's QTc has values considered in the upper limit of normality. Similar results were found by Carré (2015), when he studied this interval in endurance athletes.

Ventricular repolarization disorders are very frequent findings in athletes, which raise diagnostic doubts between the physiological and the pathological; Table 4 of the current study shows 57.2% of athletes with T wave alterations.

In the research carried out, there are deep negative T waves in V2, V3 and flattened T waves in V4, V5 and V6 and partially agree with those obtained by Hernández O (2002) and Pérez (2004) in their studies where they evidenced 27.6 % of athletes with negative T waves, 5.1% bimodal and 1.2% flattened T waves.

The appearance in Table 5 of values in the upper range of normality of variables such as the thickness of the interventricular septum and the posterior wall of the left ventricle, as well as those of the diastolic diameter of the left ventricle in lower ranges, such as were  detected  in  this  study  during  the  three  stages  studied,  should  be  carefully considered  because  they  can  be  an  indication  of  inadequate  dosage,  planning  or application of training loads, where predominantly anaerobic work is being performed without the corresponding aerobic compensation (Rabassa, 2009).

The  current  research  coincides  with  Géoffroy,  Prohías,  Castro,  Mérida  and  García (2016) where in a study of triathletes they observed a progressive increase in the septal thickness and the posterior wall of the left ventricle, both suffered a gradual rise in their dimensions  that  slightly  exceeded  the  values  considered  normal;  In  this  study,  the diastolic diameter of the left ventricle had an ascending linear increase as the training progressed, the current work differs from these results because as the training stages progressed, an inverse behavior to what was expected was verified.

These modifications suggest that there was an increase in intensity and strength work, also associated with difficulty in planning the work-rest regime; an inadequate planning of loads based on high intensities in addition to a short time of work with basic aerobic functional  direction  after  each  training  session,  what  is  indicated  corresponds  to bibliography such as Álvarez, Mollón, Mónaco and Villa (2015) regarding the subject they present the increase in wall thickness when the predominant work is with high intensity loads regardless of the preparation stage.

On the other hand, Mojena (2016) in his research that included 8 kayak schoolchildren in both sexes, obtained for the h / r index an average during the GPS and SPE of 0.35; its value in the current study does not coincide with those stated by said author.

Fuentes (2016) describes in 5 school long distance runners an average for the Ih / r in the 3 stages of preparation (GPS, PGE and SPE) of 0.42; 0.36 and 0.38 respectively, the present study does not show similarity with the last two stages analyzed.

When the mean of the equipment that was evaluated in the present investigation was analyzed,  it  is  estimated  that  there  was  an  increase  in  work  intensities  during  all preparation stages, given the high value of the h / r index, a variable that is described in several  studies  Rabassa  (2009),  Venckunas  (2008)  increases  when  there  is  a predominance of work with higher intensities and it is indicative of having received high loads.

When analyzing the ejection volume (EV) and the ejection volume index (EVI) of the school long-distance runners in this research, shown in Table 6, it can be seen that there is a predominance of the deficit of aerobic capacity in athletes, reflected in the mean of the EVI variable at all times, which does not exceed 50 ml / beat / m2 of body surface, which indicates neglect of basic aerobic work, an aspect that is taken into account in several investigations, Rabassa (2009) Rabassa ( 2011), where basic aerobic work is valued  during  the  preparation  stages  in  which  high  intensities  of  training  loads predominate.

In this study, lower than expected values  were also  found in  the variables ejection volume and ejection volume index, evident in the equipment mean for both variables, throughout  the  macrocycle,  which  does  not  coincide  with  bibliographies  (Rabassa, 2011) . (Mojena, 2016).

Fuentes (2016) during the study with school runners, in relation to the ejection volume and ejection volume index, obtained a mean of the equipment for each variable and in the three stages, lower than expected, the results of the present study are similar to those obtained in said research. In the present research, values similar to Rea (2017) were obtained in his study with school kayak practitioners in the stage studied (GPS).

When the functional direction of training has a predominance of high intensities with smaller volumes, an increase in wall thicknesses and a decrease or a slight increase in the diastolic diameter and volume of the left ventricle and the ejection volume and its respective volume index are observed, describing in these an increase in the values of the h / r index Rabassa (2009) and Rabassa (2011), which although they must be in the anaerobic  aerobic  equilibrium  range,  their  values  tend  to  be  closer  to  0.40,  which suggests As in the case of the present investigation, no adjustments were made to the training  loads,  in  addition  to  inadvertent  basic  aerobic  work  during  the  preparatory period, as shown by the results obtained in the echocardiographic studies, as part of the cardiovascular control of sports training.

Conclusions

1. The electrocardiographic changes found were: cardiac rhythm disturbances (sinus bradycardia  and  respiratory  sinus  arrhythmia),  first  degree  atrioventricular  block, incomplete right bundle branch block and minor ventricular repolarization disorders.
2. In the echocardiogram, the thickness of the interventricular septum and the posterior wall of the left ventricle showed values close to the upper limit of normality, contrary to the diastolic diameter of the left ventricle, which had a collective inclination in the equipment to low measurements during all the training stages, which contributed to a high h / r ratio in most athletes.
3. The ejection volume and the ejection volume index maintained values lower than those considered normal in the three training stages, which leads to the suggestion that there is an increase in work intensities throughout the macrocycle and a marked deficit of aerobic capacity, this suggests not having made adjustments to training loads and neglecting basic aerobic work during the preparatory period.

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