Personalized analysis of cardiac remodeling at the end of the preparatory period in cross-country skiers stratified by movement speed

A.S. Bakhareva1, , D.Z. Shibkova1, , V.B. Yarysheva2, , E.N. Terekhinai, , ¹ South Ural State University, Chelyabinsk, Russia

А.С. Бахарева1, , Д.З. Шибкова1, , В.Б. Ярышева2, , Е.Н. Терехина1, , 1 Южно-Уральский государственный университет, Челябинск, Россия 2 Федеральный центр сердечно-сосудистой хирургии, Челябинск, Россия

Introduction. It is well known that when training loads are adequate, athletes develop neu-rovegetative regulation of the circulatory system that ensures economization of cardiac function. This process is characterized by marked bradycardia and a predominance of parasympathetic heart rate regulation at rest, which reduces myocardial oxygen consumption and increases the diastolic phase of the cardiac cycle [2]. Prolonged endurance training, as the principal mechanism of cardiac adaptation, typically leads to an increase in left ventricular (LV) end-diastolic dimension and a corresponding balanced increase

in LV myocardial mass (eccentric hypertrophy), with normal LV wall thickness [14].

Differences in the formation of an “athlete’s heart” among sports primarily concern the extent and combination of myocardial hypertrophy and cavity dilation [9, 12]. According to previous findings, “athlete’s heart” develops either through an increase in the thickness of the LV posterior wall under predominantly endurance loads or by lengthening myocardial fibers when loads are variable and frequently involve short bursts of maximum intensity [2, 19]. The most significant changes are noted in the earliest years of sports

Table 1

Таблица 1

Morphometric and Qualification Indicators of Cross-Country Skiers Морфометрические и квалификационные показатели лыжников-гонщиков в конце подготовительного периода

Parameter	Leader 1 (n = 1)	Leader 10 (n = 1)	Reserve 1 (n = 1)	Reserve 10 (n = 1)
Age, years	22	21	19	20
Body mass, kg	74.10	72.20	76.80	64.20
Height, cm	181.00	178.00	178.00	176.00
Body Mass Index, a. u.	22.62	22.78	24.24	20.72
Training experience, years	7	10	9	10
Qualification	MS	MS	1st class	CMS
Speed, km/h	19.70	18.64	18.57	16.21

Note: MS – Master of Sport; CMS – Candidate Master of Sport.

Table 2

Таблица 2

Individual Echocardiographic Indicators of Cross-Country Skiers

Индивидуальные показатели параметров эхокардиограммы лыжников-гонщиков в конце подготовительного периода

Parameter	Leader 1	Leader 10	Reserve 1	Reserve 10	Normative Range*
LA size, cm	3.80	3.20	3.40	3.83	3.00–4.00
LA volume, ml	44.00	34.00	47.44	–	18.00–58.00
LV EDD (cm)	5.60	5.90	5.37	5.90	4.20–5.90
LV ESD (cm)	3.50	3.20	2.80	4.05	2.50–3.98
∆ (EDD–ESD), cm	2.10	2.70	2.57	1.85	> 1.86
EF, %	68.00	74.00	78.80	62.90	52.00–72.00
Aortic diameter, cm	3.20	3.40	3.20	3.10	2.20–4.40
Pulmonary artery, cm	2.3	2.5	2.5	2.4	< 2.80
LVMM, g	290.00	225.00	213.02	271.10	88.00–224.00
LVMMI, g/m²	145.20	123.00	119.25	147.20	50.00–102.00
SV, ml	105.00	127.00	109.96	105.70	40.00–123.00
LVPW thickness, cm	0.90	1.00	1.03	1.23	0.60–1.00
IVS thickness, cm	0.90	0.90	1.03	1.23	0.60–1.00
IVS / LVPW	1.0	0.9	1.0	1.0	< 1.00
EDV, ml	54.00	174.00	139.51	167.70	67.00–155.00
ESV, ml	49.00	47.00	29.55	62.00	22.00–58.00
EDV / LVMM	0.53	0.77	0.65	0.61	0.70–1.00

*Normative range for a healthy population [18].

were elevated by 23.0%. The EDV/LVMM ratio was below 0.70, indicating marked myocardial hypertrophy, decreased EF, and an increased end-systolic volume. This athlete requires more frequent medical monitoring.

Discussion. In endurance athletes, moderate eccentric LV hypertrophy commonly reflects adaptive mechanisms. Functional adaptation is primarily associated with an elevated stroke volume during exercise [7], facilitated by greater LV distensibility in diastole and a steeper Frank-Starling relation [13]. In adolescent athletes, average LV end-diastolic dimension is reported at about 5.16 cm (range 4.7–5.8), end-systolic dimension averages 3.25 cm, LV end-diastolic volume 128.17 ml (range 83.6–154 ml), and end-systolic volume 43.08 ml [13]. These results are within normative limits [18].

In qualified male cross-country skiers and biathletes with high training loads, end-diastolic dimension values of 5.1 (4.9–5.5) cm, end-systolic dimension of 3.3 (3.2–3.6) cm, EDV of 124.0 (117.0–147.0) ml, and ESV of 46.0 (40.0–54.0) ml have been reported, alongside LVPW and IVS values of 0.9 (0.8–1.0) cm [6]. The EDV/LVMM ratio is often used to evaluate the effectiveness of cardiac adaptation; it is ideally around 1.0 a.u. [17]. Lower values (< 0.70) suggest dominant plastic changes in the myocardium, consistent with significant hypertrophy [7].

Typically, the LV posterior wall is thicker than the interventricular septum, so IVS/LVPW < 1.0 is considered normal. A ratio > 1.0 is recognized as a key sign of LV hypertrophy [16]. Nevertheless, permissible LV wall thickness for highly trained athletes is sometimes cited up to 1.3–1.5 cm [5]. In some endurance-trained male athletes, LVPW of 1.1 ± 0.02 cm and IVS of 1.02 ± 0.02 cm were described, along with IVS/LVPW = 0.92, EDD = 5.69 ± 0.07 cm, EDV = 160.86 ± 8.73 ml, LVMM = 167.45 ± 9.09 g, and EDV/LVMM =

= 0.96 ± 0.03 [8]. Other research on cross-country skiers reported IVS = 1.34 ± 0.01 cm, LVPW = = 0.89 ± 0.01 cm, LVMMI = 170.51 ± 32.54 g/m², and EF = 44.65 ± 8.3% [20].

Conclusion. Comparisons between our findings and published data show that linear LV dimensions display relatively moderate variability, whereas volumetric parameters differ more noticeably. In highly qualified athletes, IVS/LVPW typically does not exceed the permissible upper limit.

A personalized Echo-CG analysis of crosscountry skiers from both leader and reserve groups at the end of the preparatory period revealed:

– leader 1 requires continuous monitoring due to a high LV myocardial mass (LVMM) that, if further increased, may pose health risks;

– leader 10 predominantly adapts through enhanced diastolic LV function. Although SV and EF are high, this does not guarantee optimal adaptation and could potentially lead to cardiac insufficiency if compensatory mechanisms become exhausted;

– reserve 1 shows stronger reliance on contractile mechanisms, demanding higher oxygen consumption and potentially reflecting a less efficient adaptation process;

– reserve 10 exhibits LV myocardial hypertrophy (LVMM surpassing the norm by 17.4%), with IVS and LVPW thickness 23.0% above the upper limit and a low EDV/LVMM ratio. These factors are associated with reduced EF and higher end-systolic volume, indicating the need for close medical supervision.

Overall, the data highlight substantial individual variability in cardio-hemodynamic remodeling, even within a single sport specialization. These findings underscore the importance of regular medical follow-up and personalized adjustments to optimize training and protect athletes’ cardiovascular health.