sports Article Adolescent Finswimmers: Early Myocardial Adaptations in Different Swimming Styles Vasileios Stavrou 1,2,* ID , Konstantinos Tsarouhas 3, Eleni Karetsi 1, Panagiotis Michos 1, Zoe Daniil 1 and Konstantinos I. Gourgoulianis 1 1 Laboratory of Cardio-Pulmonary Testing, Department of Respiratory Medicine, University of Thessaly, 41110 Larissa, Greece; [email protected] (E.K.); [email protected] (P.M.); [email protected] (Z.D.); [email protected] (K.I.G.) 2 School of Physical Education and Sports Science, University of Thessaly, Karyes, 42100 Trikala, Greece 3 Cardiological Department, General University Hospital of Larissa, 41222 Larissa, Greece; [email protected] * Correspondence: [email protected] Received: 12 June 2018; Accepted: 6 August 2018; Published: 10 August 2018 Abstract: Background: The purpose of our study was to investigate early differences in the adolescent female finswimmers’ echocardiography parameters, possibly associated with different swimming-style training and different training equipment (monofin (MF) versus bifin (BF)). Method: Forty-three female finswimmers participated in our study (age: 15.6 ± 2.1 years, body mass index: 20.4 ± 2.2 kg/m2, body surface area: 1.56 ± 0.04 m2, body fat: 11.2 ± 0.6%) and were divided into two groups, according to the swimming style practiced (MF vs BF). Anthropometric characteristics, echocardiography and arterial pressure were measured. The independent t-test was used for statistical comparisons between groups. Stepwise multivariate regression analysis was applied to investigate associations between various variables. Results: The two groups used training equipment with different weights (p < 0.001). Female adolescent finswimmers presented signs of myocardial hypertrophy depicted by the increased left ventricle myocardial mass indexed to body surface area (101.34 ± 23.65). Different patterns of myocardial hypertrophy were observed for the two groups; MF swimmers presented concentric hypertrophy, while BF swimmers presented eccentric hypertrophy (relative wall thickness MF = 0.46 ± 0.08 vs BF = 0.39 ± 0.06 cm, p < 0.05). MF swimmers had also higher left ventricular posterior wall diameters (p < 0.05), lower stroke volume values (p < 0.05) and lower ejection fraction (p < 0.05) compared to BF athletes. Conclusion: Adolescent female finswimmers presented different patterns of myocardial hypertrophy possibly related to different training protocols and modes of exercise. Keywords: monofin; bifin; adolescent; myocardial hypertrophy 1. Introduction Finswimming is a speed competition sport practiced at the surface or underwater with different monofins (MFs) or bifins (BFs) of variable rigidity. In MF, swimmers’ lower limbs are used for propulsion purposes (vertical displacement of the body) and in BF swimming athletes crawl with snorkel and fins. Echocardiography is a noninvasive technique to evaluate the cardiac adaptations associated with training in people practicing sports [1]. According to Grazioli et al. [1], the hemodynamic changes caused by physical exercise alter the loading conditions of the heart and predispose one to cardiac adaptations in order to normalize the said loading stress. Myocardial wall thickness, stroke volume and both left ventricular (LV) and right ventricular (RV) end-diastolic diameters Sports 2018, 6, 78; doi:10.3390/sports6030078 www.mdpi.com/journal/sports Sports 2018, 6, 78 2 of 9 Sports 2018, 6, x FOR PEER REVIEW 2 of 9 werein long-distance greater in long-distance swimmers compared swimmers to comparedshort-distance to short-distance swimmers. Moreover, swimmers. the Moreover,short-distance the short-distanceswimmers presented swimmers higher presented heart rate higher and systolic heart rate blood and pressure systolic values blood at pressure rest compared values to at long- rest compareddistance swimmers to long-distance [2]. Cardiovascular swimmers [2]. adaptations Cardiovascular are related adaptations to type are and related frequency to type of and exercise frequency and ofthe exercise kind of and sport the kind practiced of sport [3]. practiced Exercise [3 ].durati Exerciseon relates duration to relates the morphological to the morphological changes changes of the ofmyocardial the myocardial left ventricle left ventricle (LV) (LV)including including an increase an increase in wall in wall thickness thickness [4], [and4], and usually usually affects affects both both the theinterventricular interventricular septum septum (IVS) (IVS) and and left left ventricular ventricular posterior posterior wall wall (LVPW) (LVPW) [5]. [5]. LV wallwall thicknessthickness increaseincrease was was observed observed in swimmersin swimmers after after aerobic aerobic exercise exercise without without any significant any significant change inchange LV diastolic in LV diameterdiastolic [diameter3]. Furthermore, [3]. Furthermore, regarding regarding the physiology the physiology of finswimming, of finswimming, during training, during periods training, of apneaperiods may of beapnea used may to cover be used short to distances cover short underwater, distances a practiceunderwater, that coulda practice be characterized that could asbe dynamiccharacterized apnea, as adynamic phenomenon apnea, thatina phenomenon turn could thatin induce turn specific could induce responses, specific that responses, is, hypoxia that and is, hypercapniahypoxia and [ 6hypercapnia]. [6]. TheThe purpose purpose of of the the current current study study was was to to investigate investigate the the effect effect of swimmingof swimming style style and and possibly possibly the differentthe different training training of the of two the adolescenttwo adolescent groups groups on echocardiography on echocardiography parameters, parameters, and to and evaluate to evaluate early signsearly ofsigns myocardial of myocardial adaptation adaptation to exercise. to exercise. The two The groups two groups used different used different equipment equipment (monofin (monofin (MF): −1 −1 fin(MF): with fin approximate with approximate weight weight 3.5 kg 3.5; and kg−1 bifins; and bifins (BFs): (BFs): two fins two with fins approximate with approximate weight weight 1.1 kg 1.1 (Figurekg−1 (Figure1)). 1)). a b FigureFigure 1. 1.Athletes’ Athletes’ equipment: equipment: (a) monofin(a) monofin and (band) bifin. (b) Monofinbifin. Monofin was made was from made rubber from and rubber fiberglass, and andfiberglass, maximum and weight maximum is approximately weight is 3.5approximatel kg. Bifinswerey 3.5 made kg. fromBifinswere rubber, made and maximum from rubber, weight and is approximatelymaximum weight 1.1 kg.is approximately 1.1 kg. 2.2. MethodMethod 2.1.2.1. ParticipantsParticipants Forty-threeForty-three Caucasian Caucasian young young women women from from Greek Greek finswimming finswimming sports sports clubs clubs were were included included in the in studythe study on a on voluntary a voluntary basis basis (Table (Table1) and 1) divided and divided into two into groups two groups (MF group (MF: ngroup= 26: nvs = 26 BF groupvs BF: groupn =:17). n = Inclusion17). Inclusion criteria criteria include include athletes athletes involved involved in 50, 100in 50, and 100 200 and m events200 m withevents MF with on theMF surface on the andsurface BF, trainingand BF, fortraining at least for 3 at years, least 10-h3 years, training 10-h pertraining week per and week no medical and no history.medical Allhistory. participants All participants trained aftertrained school after between school between 14:30 to 16:30,14:30 5to to 16:30, 6 days 5 to per 6 days week, per and week, used and equipment used equipment in accordance in accordance with the Worldwith the Underwater World Underwater Federation Federation rules (CMAS) rules [7 ].(CMAS) Swimmers [7]. Swimmers with medical with history, medical as wellhistory, as swimmers as well as involvedswimmers in involved classical swimmingin classical trainingswimming and/or training other and/or sports other for moresports than for more one year, than were one year, excluded were fromexcluded the study from population. the study Thepopulation. study period The wasstudy 1 month.period Thewas study1 month. was conductedThe study accordingwas conducted to the Helsinkiaccording declaration to the Helsinki for use indeclaration human subjects for use (No. in ofhuman Ethical subjects Committee: (No. 2-5/2.2.2011, of Ethical Committee: University of2- Thessaly).5/2.2.2011, All University participants’ of Thessaly). parents submittedAll participants’ a written parents consent. submitted a written consent. Sports 2018, 6, 78 3 of 9 Table 1. Athletes’characteristics, training frequency and performance. Continuous variables are presented as mean ± standard deviation. Characteristics Total (n = 43) MFgroup (n = 26) BFgroup (n = 17) p-Value Age, years 15.6 ± 2.1 15.9 ± 2.1 15.1 ± 2.1 NS Body mass index, kg/m2 20.4 ± 2.2 20.7 ± 2.2 19.8 ± 2.1 NS Body surface area, m2 1.5 ± 0.04 1.6 ± 0.04 1.5 ± 0.03 NS Body fat, % 11.2 ± 0.6 11.4 ± 0.6 10.9 ± 0.7 NS Tanner score 4.1 ± 0.7 4.0 ± 0.7 4.3 ± 0.8 NS Training age, years 4.1 ± 1.5 4.5 ± 1.8 3.4 ± 0.5 0.017 Training, day/h 2.1 ± 0.2 2.1 ± 0.2 2.0 ± 0.1 NS Training, week/h 13.0 ± 1.0 13.1 ± 3.1 13.2 ± 2.9 NS Gym, week/h 3.0 ± 1.1 3.2 ± 0.9 2.8 ± 1.3 NS Best trial 50-m, second 23.4 ± 2.6 22.0 ± 1.8 26.5 ± 1.1 <0.001 100-m, second 55.7 ± 5.7 51.5 ± 2.4 59.4 ± 5.1 0.003 200-m, second 113.4 ± 10.1 106.6 ± 4.5 124.6 ± 3.6 0.001 Note: NS: not significant. 2.2. Data Collection Anthropometric characteristics as body height, body mass (Seca 700), body mass index 2 1 (BMI = kg/m ), body surface area (BSA = (height (cm) × weight (kg))/3600 ⁄2)[8], percentage of body fat (7-point measurement, Harpenden),stages of biological maturation [9] and pulmonary function parameters (FEV1: forced expiratory volume in 1st second, FVC: forced vital capacity, PEF: peak expiratory force; MasterScreen-CPX, VIASYS HealthCare, Hochberg, Germany) [10] were recorded prior to echocardiography. Echocardiographic studies were performed in the morning hours and all participants did not compete or train for at least 12 h before the study.