Cardiovascular adaptations to endurance training and detraining in young and older athletes

International Journal of Cardiology 65 (1998) 149–155

Cardiovascular adaptations to endurance training and detraining in young and older athletes a, b a b b Franco Giada *, Emanuele Bertaglia , Bruno De Piccoli , Maurizio Franceschi , Federico Sartori , Antonio Raviele a , Piero Pascotto b a

Division of Cardiology, O.C. Mestre, via Circonvallazione 50, 30170 Mestre, Venice, Italy b Division of Cardiology, O.C. Mirano, Venice, Italy Received 24 December 1997; accepted 27 March 1998

Abstract In order to evaluate the influence of aging on cardiovascular adaptations to endurance training and detraining, 12 young (range 19–25 years) and 12 older (range 50–65 years) male cyclists were examined during the training and after 2 months of detraining. Twelve young and 12 older healthy sedentary males matched for age and body surface area were used as control groups. Each subject underwent a maximal exercise test using a cycle-ergometer in order to measure maximum oxygen consumption, an M-mode and 2D echocardiography in order to assess left ventricle morphology and systolic function, and a Doppler echocardiography for evaluating the diastolic filling pattern. During the training period both groups of athletes showed higher values of maximum oxygen consumption, left ventricular wall thicknesses, end-diastolic diameter and volume, as well as left ventricular mass, than their control subjects; in the older subjects the adaptation of the heart to aerobic training seems to be obtained mainly through a higher increase in left ventricular diastolic filling. In both groups no significant modifications in the ejection fraction and diastolic function parameters were recorded. After the detraining period the wall thicknesses decreased only in young athletes, while left ventricular mass and end-diastolic diameter and volume reduced only in older athletes. In conclusion, training and detraining induced nearly similar left ventricular morphological modifications in the two age groups, even though greater in the older athletes with respect to the ventricular mass and volume. No relevant differences were observed in the Doppler filling pattern between athletes and sedentary controls.  1998 Elsevier Science Ireland Ltd. Keywords: Physical activity; Aging; Left ventricular function

1. Introduction Many authors analyzed the cardiovascular response to endurance training in both young-adult [1–3] and older [4] athletes and highlighted the advantages which the latter group could also obtain from a training appropriate in terms of length, frequency and intensity [5]. There are few studies regarding the reversibility of such adaptations after a detraining period. In particular, data are scarce concerning *Corresponding author. Tel.: 139 41 2607201; fax: 139 41 2607235.

possible differences in the response to physical training interruption between young and older subjects [1,3,6–8]. M-mode and 2D echocardiography allows a non-invasive and repeatable definition of the ventricular systolic function, and to this aim it was extensively used in the study of ‘athlete’s heart’ [9–11]. With the Doppler method, indices of left ventricular diastolic function became available, such figures being useful in evaluating its relaxation capacity [12,13]. In order to study the influence of age on cardiovascular adaptations to aerobic training and de-

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training, as well as to discover possible alterations in left ventricular relaxation related to myocardial hypertrophy, 12 young and 12 older cyclists were examined at the peak of their athletic preparation and after a detraining period.

The percentage of body weight consisting of adipose tissue (body fat mass) and the fat-free mass (in kg) were estimated by bioelectrical impedance analysis (BIA 109, RJL Akern, Firenze, Italy).

2.3. Measurement of maximum aerobic power 2. Materials and methods

2.1. Subjects and study design Twelve older (age range 50 to 65 years) and 12 young (age range 19 to 25 years) male amateur cyclists were examined at the end of the competitive season (October) and then again 2 months after the suspension of physical activity (December). During detraining, the athletes agreed not to undergo any maintenance program and limited their level of physical exercise to that determined by their working activity (sedentary in all cases). They had all been practising road cycling, consisting mainly of aerobic physical activity, for several years (21612 and 965 years for older and young athletes, respectively). In the previous 6 months, the young cyclists covered 3516162 km / week and the older athletes rode 213689 km / week. The control group consisted of 12 older and 12 young healthy sedentary males matched for age, height, and weight, who were not engaged in any physical training program. After obtaining informed written consent, every subject underwent a general medical examination, an electrocardiogram, and routine blood tests. None of the athletes smoked; only two young control subjects were habitual smokers (10 cigarettes daily). During the entire study no subject was taking any medication.

2.2. General characteristics In order to calculate body surface area the subjects underwent weight and height measurements while wearing only undershorts and no shoes, with an accuracy of 0.1 kg and 0.1 cm, respectively. Arterial blood pressure was measured at rest, in supine position and in a quiet room three times with a Rivarocci sphygmomanometer. The mean of the last two values was registered. Korotoff-V phase was used as diastolic blood pressure.

In order to evaluate the degree of physical conditioning, both during the training and detraining phases, each athlete underwent an assessment of the maximum aerobic power. Maximum oxygen consumption (VO 2 max) was measured during a maximal exercise test using an electrically braked cycleergometer. The work load was increased by 50 W every 3 min. The ECG was continuously monitored on three leads. Pulmonary gas exchange variables were measured every 30 s during the exercise test with an ergospirometer (2900 / C, Sensormedics, Yorba Linda-California, USA). VO 2 max was defined as the maximum VO 2 value obtained during the last work load.

2.4. Echocardiography The echocardiograms were carried out both during the training and detraining phase using an Aloka 870 instrument with a 3.5 and 2.5 MHz phased array transducer complete with color Doppler. The examination was recorded on a VHS video-tape and then reviewed in real time, slow motion and frame by frame. Using the 2D long and short axis parasternal views and observing the recommendation of the American Society of Echocardiography [14], the following parameters, corrected for body surface area, were determined: left ventricular end-diastolic diameter; interventricular septal wall thickness; posterior wall thickness; left atrium size. The left ventricular ejection fraction was determined by calculating the end-diastolic and end-systolic volumes according to Folland [15]. The left ventricular mass was obtained according to Wyatt [16]. Doppler data were used as parameters of left ventricular diastolic function [12,13]. Mitralic flow was measured by pulsed Doppler placing the sample volume at the centre of the mitralic valve plane and simultaneously recording the ECG and the phonocardiogram at a speed of 100 mm / s. In this way the following data were calculated: maximal early flow

F. Giada et al. / International Journal of Cardiology 65 (1998) 149 – 155

151

Table 1 General characteristics

Older Cyclists (n512) Training Detraining Controls (n512) Young Cyclists (n512) Training Detraining Controls (n512)

Age (years)

HR (bpm)

BSA (m 2 )

SBP (mmHg)

DBP (mmHg)

BFM (%)

FFM (kg)

5565

5566 b 6266 69610

1.8660.1 1.8860.1 1.9260.1

139614 144617 146617

8768 d 8369 8368

15.362.9 a,b 16.863.7 20.563.1

63.965.2 63.464.7 62.564.9

4865 b 5167 68612

1.8760.1 a 1.8960.1 1.9160.1

12967 13168 138613

71616 7365 75610

14.663.0 a,b 18.863.7 20.965.6

60.565.8 59.264.6 58.067.4

5866

2466 2362

BSA, body surface area; SBP, systolic blood pressure; DBP, diastolic blood pressure; BFM, body fat mass; FFM, fat free mass; HR, heart rate. a P,0.05 training vs. detraining; b P,0.05 training vs. controls; d P,0.05 older training vs. young controls.

velocity (E), maximal late flow velocity (A), E integral, A integral, E /A ratio and E /A integral ratio. The isovolumetric relaxation time was calculated starting from the second tone on phonocardiogram to the foot of the E wave of the mitralic Doppler curve.

2.5. Statistical analysis All data are expressed as the mean6S.D. The four groups were compared using one-way ANOVA (program P2V, BMDP statistical package) with adjustment according to Bonferroni probabilities; ‘pooled variance’ was selected to evaluate the level of significance [17]. Student’s t-test for paired data was used to compare data obtained during and after training. P values ,0.05 were considered significant.

3. Results

3.1. General characteristics General characteristics are listed in Table 1. During the training phase there were no differences between athletes and controls apart from heart rate and body fat mass which were lower in athletes. Body fat mass increased significantly after detraining in both groups of athletes.

3.2. Echocardiography Table 2 summarizes M-mode and 2D echocardiographic data. During the training phase both athlete groups showed significantly higher levels of left ventricular end-diastolic diameter, posterior wall

Table 2 M-mode and 2D echocardiographic data LVDdI (mm / m 2 )

PWTI (mm / m 2 )

IVSTI (mm / m 2 )

LAI (mm / m 2 )

r / h (%)

LVVdI (ml / m 2 )

LVMI (g / m 2 )

EF (%)

Older Cyclists (n512) Training Detraining Controls (n512)

2963 a,b 2863 2662

6.360.6 b,d 6.160.6 c 5.360.3

6.360.6 b,d 6.260.7 c 5.460.5

2462 b,d 2362 2062

2.260.2 2.260.2 2.360.2

91617 a,b 82613 c 6569

134619 a,b,d 113616 c 93612

6365 6565 6764

Young Cyclists (n512) Training Detraining Controls (n512)

3063 b 3061 c 2762

6.160.5 a,b 5.760.4 c 5.060.4

6.260.7 a,b 5.860.4 c 5.160.4

2163 2162 1863

2.460.2 2.560.2 2.660.2

99615 b 9868 c 77610

124612 b 122620 101617

6367 5966 6466

LVDdI, left ventricular end-diastolic diameter index; PWTI, posterior wall thickness index; IVSTI, interventricular septal wall thickness index; LAI, left atrium size index; r / h, left ventricular radius / thickness ratio; LVVdI, left ventricular end-diastolic volume index; LVMI, left ventricular mass index; EF, ejection fraction. a P,0.05 training vs. detraining; b P,0.05 training vs. controls; c P,0.05 detraining vs. controls; d P,0.05 older training vs. young controls.

F. Giada et al. / International Journal of Cardiology 65 (1998) 149 – 155

152 Table 3 Doppler echocardiographic data E (cm / s)

A (cm / s)

E /A

EI

AI

EI /AI

IRT (ms)

Older Cyclists (n512) Training Controls (n512)

57619 54612 e

54615 f 5767 e

1.060.3 d,f 0.960.2 e

7.262.4 7.161.0

4.261.1 d,f 4.460.8 e

1.760.4 d,f 1.660.5 e

9969 d,f 96611 e

Young Cyclists (n512) Training Controls (n512)

71610 74610

3768 4661.0

1.960.4 1.760.4

8.061.7 7.761.3

2.760.6 3.060.5

3.161.1 2.560.5

85111 7768

E, early diastolic flow peak velocity; A, late diastolic flow peak velocity; EI, integral of early diastolic flow velocity; AI, integral of late diastolic flow velocity; IRT, isovolumetric relaxation time. d P,0.05 older training vs. young controls: e P,0.05 older controls vs. young controls; f P,0.05 older training vs. youug training.

thickness, interventricular septum thickness, left ventricular end-diastolic volume, left ventricular mass. In particular, when compared with their respective sedentary controls, the increment of left ventricular end-diastolic volume and left ventricular mass was proportionally higher in the older than in the young cyclists (131% vs. 122% for end-diastolic volume and 131% vs. 19% for mass, respectively). No difference was observed in left ventricular radius / thickness ratio and ejection fraction, while left atrium size was higher in older cyclists than in controls. After detraining, posterior wall and interventricular septum thicknesses significantly decreased only in young cyclists, while end-diastolic diameter, enddiastolic volume and mass reduced only in the older athletes. Doppler parameters are listed in Table 3. No differences were observed between athletes and their

sedentary controls. Higher values of A, A integral and isovolumetric relaxation time and lower ones of E, E /A ratio and E /A integral ratio were recorded in the older sedentary group than in the young sedentary subjects. In the older athletes, instead, E, A and E integral were not significantly different to those of the young controls.

3.3. Maximal exercise test Data on the maximal exercise test are listed in Table 4. In both athlete groups VO 2 max and maximum work load were significantly higher while heart rate at 100 W was lower than their controls. In older cyclists VO 2 was significantly higher than sedentary young subjects too. After detraining, VO 2 max lowered significantly both in the older and in the young athletes; however, it continued to be higher

Table 4 Physiological variables during maximal exercise Watt max

HR 100W (bpm)

HR (bpm)

SBP (mmHg)

DBP (mmHg)

VO 2 max (ml / min / kg)

Older Cyclists (n512) Training Detraining Controls (n512)

283633 a,b,d,f 258636 c 158629 e

100610 a,b,d 106613 c 121610 e

16764 b,d,f 16969 c 15067 e

234617 d 230618 247624 e

97611 d,f 9469 105612 e

4367 a,b,d,f 3667 c 2363 e

Young Cyclists (n512) Training Detraining Controls (n512)

372631 a,b 359630 c 221626

108620 a,b 114616 c 138617

19069 18969 191615

216613 220614 21468

81610 7767 81610

59610 a,b 4969 c 3566

Watt max, maximum work load; HR 100W , heart rate at 100 W; HR, maximal heart rate; SBP, maximal systolic blood pressure; DBP, maximal diastolic blood pressure; VO 2 , maximal O 2 uptake. a P,0.05 training vs. detraining; b P,0.05 training vs. controls; c P,0.05 detraining vs. controls; d P,0.05 older training vs. young controls; e P,0.05 older controls vs. young controls; f P,0.05 older training vs. young training.

F. Giada et al. / International Journal of Cardiology 65 (1998) 149 – 155

than controls. Maximal heart rate was higher in older athletes than their sedentary controls, while no differences were observed between the young subjects. Maximal systolic and diastolic blood pressure were higher in older than in young subjects.

4. Discussion

4.1. Effects of endurance training In older subjects carrying out continuous endurance training many authors have observed a slowing down in the progressive reduction of VO 2 max which accompanies the aging process [18,19]. The improvement in the older athletes’ physical performance with respect to the sedentary older subjects is connected with both muscular and cardiocirculatory adaptations consisting of an increase in the stroke volume, a retaining of vasodilatatory response and an enhanced inotropic state [4]. Although endurance training does not seem to modify the age-associated decline in response to an adrenergic stimulation [20], the larger stroke volume in master athletes could be due not only to the use of Frank-Starling effect, but also to an enhanced left ventricular systolic function [21]. In this study VO 2 max reached by elderly cyclists is higher not only than their controls but also than sedentary young subjects. In addition the echocardiographic analysis has highlighted how endurance training determines a proportionally greater increase in the ventricular volume in the elderly subjects and in the ventricular thicknesses in the younger ones. No remarkable modification was observed as to ejection fraction, both among elderly cyclists and elderly sedentary subjects. This may indicate that, at least during rest, left ventricular function of the healthy elderly subject is preserved. This is in accordance with recent work by Seals et al. [21], although data in the literature are controversial [9,22,23]. A significant increase of left atrium size was noted only in elderly cyclists, as already observed by other authors [9]: it has not yet been studied whether this may influence the loss of sinus rhythm in older athletes. Age and physical activity influence ventricular filling in healthy subjects [24,25]. Aging affects the duration of isovolumic relaxation and the early and late filling phases of diastole, independently of heart

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rate, systemic arterial blood pressure and calculated left ventricular mass [26]. Despite conspicuous high ventricular hypertrophy, diastolic function indices, determined by M-mode or Doppler echocardiography are normal or increased in both endurance and resistive athletes [27–29]. Voutilainen [24] and Tekamoto [30] have found that the favourable effects in early left ventricular filling of regular physical activity is really most conspicuous in the elderly. In our study, although significant differences between athletes and sedentary subjects were not found, it may be noted that in the trained elderly subjects Doppler curve morphology of ventricular filling seems to resemble that of young people, with an increase in the E wave and a reduction in the A wave.

4.2. Effects of physical deconditioning Athletes who have carried out endurance training for many years maintain a VO 2 max higher than control sedentary subjects even after suspending such activity for more than 2 months [6]. Our data, obtained after 2 months of physical deconditioning, agree with the previous observations. In the past, the fundamental role of preload in cardiocirculatory adaptations of young athletes to endurance training and detraining was already highlighted [6–8]. The reduction of preload seems to be the main cause of the performance drop-off after a period of physical deconditioning lasting between 2 and 12 weeks. Indeed, during detraining it was possible to obtain a recovery of the hemodynamic values recorded during the training phase by influence preload with both blood volume expansion [8] and recumbency [7]. To our knowledge, no study has been undertaken to evaluate the effects of detraining in elderly athletes. Our results, obtained at rest and in a supine position, indicate that after 8 weeks of physical deconditioning the significant reduction in left ventricular mass observed in the elderly cyclists is obtained above all at the expense of the cardiac cavities, while the thicknesses of the free wall and septum remain unchanged. On the contrary, in the young athletes the thicknesses greatly reduce, while ventricular cavities remain unchanged, the final results being a slight and not significant reduction in left ventricular mass. It therefore seems that in the

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elderly subject cardiac adaptation to aerobic training takes place above all thanks to a higher degree of diastolic filling of the left ventricle with a greater utilisation of Starling’s mechanism, which makes up for the reduced chronotropic capacity.

5. Conclusions Our results indicate that training and detraining induced similar modifications in the two age groups, even though such modifications seem, above all, to affect left ventricular mass and volume in the elderly athletes and ventricular thicknesses in the young ones. In the elderly subjects a higher degree of left ventricle diastolic filling is the most important cardiac adaptation to aerobic physical exercise. Finally, endurance training seems to induce a slight improvement in the parameters of diastolic function; in particular in the trained elderly subjects Doppler curve morphology of ventricular filling tends to resemble that of the young ones.

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