The influence of maturation on exercise-induced cardiac remodelling and haematological adaptation

Flow-mediated dilation is modified by exercise training status during childhood and adolescence: preliminary evidence of the youth athlete's artery

Chronic exercise training is associated with an "athlete's artery" phenotype in young adults and an attenuated age-related decline in endothelium-dependent arterial function. Adolescence is associated with an influx of sex-specific hormones that may exert divergent effects on endothelial function, but whether training adaptations interact with biological maturation to produce a "youth athlete's artery" has not been explored. We investigated the influence of exercise-training status on endothelium-dependent arterial function during childhood and adolescence. Brachial artery flow-mediated dilation (FMD) was assessed in n = 102 exercise-trained (males, n = 25; females, n = 29) and untrained (males, n = 23; females, n = 25) youths, characterized as pre (males, n = 25; females, n = 26)- or post (males, n = 23; females, n = 28)-predicted age at peak height velocity (PHV). Baseline brachial artery diameter was larger in post- compared with pre-PHV youths (P ≤ 0.001), males compared with females (P ≤ 0.001), and trained compared with untrained youths (3.26 ± 0.51 vs. 3.11 ± 0.42 mm; P = 0.041). Brachial FMD was similar in pre- and post-PHV youths (P = 0.298), and males and females (P = 0.946). However, exercise-trained youths demonstrated higher FMD when compared with untrained counterparts (5.3 ± 3.3 vs. 3.0 ± 2.6%; P ≤ 0.001). Furthermore, brachial artery diameter (r2 = 0.142; P = 0.007 vs. r2 = 0.004; P = 0.652) and FMD (r2 = 0.138; P = 0.008 vs. r2 = 0.003; P = 0.706) were positively associated with cardiorespiratory fitness in post-, but not pre-PHV youths, respectively. Collectively, our data indicate that exercise training is associated with brachial artery remodeling and enhanced endothelial function during youth. However, arterial remodeling and endothelium-dependent function are only associated with elevated cardiorespiratory fitness during later stages of adolescence.NEW & NOTEWORTHY We report preliminary evidence of the "youth athlete's artery," characterized by training-related arterial remodeling and elevated endothelium-dependent arterial function in children and adolescents. However, training-related adaptations in brachial artery diameter and flow-mediated dilation (FMD) were associated with cardiorespiratory fitness in adolescents, but not in children. Our findings indicate that endothelium-dependent arterial function is modifiable with chronic exercise training during childhood, but the association between FMD and elevated cardiorespiratory fitness is only apparent during later stages of adolescence.

Intensified training augments cardiac function, but not blood volume, in male youth elite ice hockey team players

While it is well-established that a period of interval training performed at near maximal effort, such as speed endurance training (SET), enhances intense exercise performance in well-trained individuals, less is known about its effect on cardiac morphology and function as well as blood volume. To investigate this, we subjected 12 Under-20 Danish national team ice hockey players (age 18 ± 1 years, mean ± SD) to 4 weeks of SET, consisting of 6-10 × 20 s skating bouts at maximal effort interspersed by 2 min of recovery conducted three times weekly. This was followed by 4 weeks of regular training (follow-up). We assessed resting cardiac function and dimensions using transthoracic echocardiography and quantified total blood volume with the carbon monoxide rebreathing technique at three time points: before SET, after SET and after the follow-up period. After SET, stroke volume had increased by 10 (2-18) mL (mean (95% CI)), left atrial end-diastolic volume by 10 (3-17) mL, and circumferential strain improved by 0.9%-points (1.7-0.1) (all P < 0.05). At follow-up, circumferential strain and left atrial end-diastolic volume were reverted to baseline levels, while stroke volume remained elevated. Blood volume and morphological parameters for the left ventricle, including mass and end-diastolic volume, did not change during the study. In conclusion, our findings demonstrate that a brief period of SET elicits beneficial central cardiac adaptations in elite ice hockey players independent of changes in blood volume.

Neuromuscular Adaptations in Endurance-Trained Male Adolescents Versus Untrained Peers: A 9-Month Longitudinal Study

BACKGROUND

Neuromuscular function is considered as a determinant factor of endurance performance during adulthood. However, whether endurance training triggers further neuromuscular adaptations exceeding those of growth and maturation alone over the rapid adolescent growth period is yet to be determined.

OBJECTIVE

The present study investigated the concurrent role of growth, maturation, and endurance training on neuromuscular function through a 9-month training period in adolescent triathletes.

METHODS

Thirty-eight 13- to 15-year-old males (23 triathletes [~6 h/week endurance training] and 15 untrained [<2 h/week endurance activity]) were evaluated before and after a 9-month triathlon training season. Maximal oxygen uptake (V̇O2max) and power at V̇O2max were assessed during incremental cycling. Knee extensor maximal voluntary isometric contraction torque (MVCISO) was measured and the voluntary activation level (VAL) was determined using the twitch interpolation technique. Knee extensor doublet peak torque (T100Hz) and normalized vastus lateralis (VL) electromyographic activity (EMG/M-wave) were also determined. VL and rectus femoris (RF) muscle architecture was assessed using ultrasonography.

RESULTS

Absolute V̇O2max increased similarly in both groups but power at V̇O2max only significantly increased in triathletes (+13.8%). MVCISO (+14.4%), VL (+4.4%), and RF (+15.8%) muscle thicknesses and RF pennation angle (+22.1%) increased over the 9-month period in both groups similarly (p < 0.01), although no changes were observed in T100Hz, VAL, or VL EMG/M-wave. No changes were detected in any neuromuscular variables, except for coactivation.

CONCLUSION

Endurance training did not induce detectible, additional neuromuscular adaptations. However, the training-specific cycling power improvement in triathletes may reflect continued skill enhancement over the training period.

Adaptation of Left Ventricular Twist Mechanics in Exercise-Trained Children Is Only Evident after the Adolescent Growth Spurt

BACKGROUND

The extent of structural cardiac remodeling in response to endurance training is maturity dependent. In adults, this structural adaptation is often associated with the adaptation of left ventricular (LV) twist mechanics. For example, an increase in LV twist often follows an expansion in end-diastolic volume, whereas a reduction in twist may follow a thickening of the LV walls. While structural cardiac remodeling has been shown to be more prominent post-peak height velocity (PHV), it remains to be determined how this maturation-dependent structural remodeling influences LV twist. Therefore, we aimed to (1) compare LV twist mechanics between trained and untrained children pre- and post-PHV and (2) investigate how LV structural variables relate to LV twist mechanics pre- and post-PHV.

METHODS

Left ventricular function and morphology were assessed (echocardiography) in endurance-trained and untrained boys (n = 38 and n = 28, respectively) and girls (n = 39 and n = 34, respectively). Participants were categorized as either pre- or post-PHV using maturity offset to estimate somatic maturation.

RESULTS

Pre-PHV, there were no differences in LV twist or torsion between trained and untrained boys (twist: P = .630; torsion: P = .382) or girls (twist: P = .502; torsion: P = .316), and LV twist mechanics were not related with any LV structural variables (P > .05). Post-PHV, LV twist was lower in trained versus untrained boys (P = .004), with torsion lower in trained groups, irrespective of sex (boys: P < .001; girls: P = .017). Moreover, LV torsion was inversely related to LV mass (boys: r = -0.55, P = .001; girls: r = -0.46, P = .003) and end-diastolic volume (boys: r = -0.64, P < .001; girls: r = -0.36, P = .025) in both sexes.

CONCLUSIONS

A difference in LV twist mechanics between endurance-trained and untrained cohorts is only apparent post-PHV, where structural and functional remodeling were related.

The influence of maturation and sex on intracranial blood velocities during exercise in children

Cerebral blood velocity (CBv) increases in response to moderate exercise in humans, but the magnitude of change is smaller in children compared with postpubertal adolescents and adults. Whether sex differences exist in the anterior or posterior CBv response to exercise across pubertal development remains to be determined. We assessed middle cerebral artery (MCAv) and posterior cerebral artery (PCAv) blood velocity via transcranial Doppler in 38 prepubertal (18 males) and 48 postpubertal (23 males) with cerebrovascular and cardiorespiratory measures compared at baseline and ventilatory threshold. At baseline, MCAv was higher in both sexes pre- versus postpuberty. Females demonstrated a greater MCAv (P < 0.001) than their male counterparts (prepubertal females; 78 ± 11 cm·s-1 vs. prepubertal males; 72 ± 8 cm·s-1, and postpubertal females; 68 ± 10 cm·s-1 vs. postpubertal males; 62 ± 7 cm·s-1). During exercise, MCAv remained higher in postpubertal females versus males (81 ± 15 cm·s-1 vs. 73 ± 11 cm·s-1), but there were no differences in prepuberty. The relative increase in PCAv was greater in post- versus prepubertal females (51 ± 9 cm·s-1 vs. 45 ± 11 cm·s-1; P = 0.032) but was similar in males and females. Our findings suggest that biological sex alters anterior cerebral blood velocities at rest in both pre- and postpubertal youth, but the response to submaximal exercise is only influenced by sex postpuberty.NEW & NOTEWORTHY Cerebral blood velocity (CBv) in the anterior circulation was higher in females compared with males irrespective of maturational stage, but not in the posterior circulation. In response to exercise, females demonstrated a greater CBv compared with males, especially post-peak height velocity (post-PHV) where the CBv response to exercise was more pronounced. Our findings suggest that both CBv at rest and in response to acute submaximal exercise are altered by biological sex in a maturity-dependent manner.

The effect of long-term soccer training on left ventricular structure and function in elite male youth soccer players

AIMS

Cardiac adaptations in elite, male adolescent youth soccer players have been demonstrated in relation to training status. The time course of these adaptations and the delineation of the influence of volatile growth phases from the training effect on these adaptations remain unclear. Consequently, the aims of the study were to evaluate the impact of 3 years of elite-level soccer training on changes in left ventricular (LV) structure and function in a group of highly trained elite youth male soccer players (SP) as they transitioned through the pre-to-adolescent phase of their growth.

METHODS

Twenty-two male youth SP from the highest Level of English Premier League Academy U-12 teams were evaluated once a year for three soccer seasons as the players progressed from the U-12 to U-14 teams. Fifteen recreationally active control participants (CON) were also evaluated over the same 3-year period. Two-dimensional transthoracic echocardiography was used to quantify LV structure and function.

RESULTS

After adjusting for the influence of growth and maturation, training-induced increases in Years 2 and 3 were noted for: LV end diastolic volume (LVEDV; p = 0.02) and LV end systolic volume (LVESV; p = 0.02) in the SP compared to CON. Training-induced decrements were noted for LV ejection fraction (LVEF; p = 0.006) and TDI-S' (p < 0.001).

CONCLUSIONS

An increase in training volume (Years 2 and 3) were aligned with LV volumetric adaptations and decrements in systolic function in the SP that were independent from the influence of rapid somatic growth. Decrements in systolic function were suggestive of a functional reserve for exercise.

Cerebral blood flow and cerebrovascular reactivity are modified by maturational stage and exercise training status during youth

NEW FINDINGS

What is the central question of this study? Gonadal hormones modulate cerebrovascular function while insulin-like growth factor 1 (IGF-1) facilitates exercise-mediated cerebral angiogenesis; puberty is a critical period of neurodevelopment alongside elevated gonadal hormone and IGF-1 activity: but whether exercise training across puberty enhances cerebrovascular function is unkown. What is the main finding and its importance? Cerebral blood flow is elevated in endurance trained adolescent males when compared to untrained counterparts. However, cerebrovascular reactivity to hypercapnia is faster in trained vs. untrained children, but not adolescents. Exercise-induced improvements in cerebrovascular function are attainable as early as the first decade of life.

ABSTRACT

Global cerebral blood flow (gCBF) and cerebrovascular reactivity to hypercapnia (CV R C O 2 ${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) are modulated by gonadal hormone activity, while insulin-like growth factor 1 facilitates exercise-mediated cerebral angiogenesis in adults. Whether critical periods of heightened hormonal and neural development during puberty represent an opportunity to further enhance gCBF andCV R C O 2 ${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ is currently unknown. Therefore, we used duplex ultrasound to assess gCBF andCV R C O 2 ${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ in n = 128 adolescents characterised as endurance-exercise trained (males: n = 30, females: n = 36) or untrained (males: n = 29, females: n = 33). Participants were further categorised as pre- (males: n = 35, females: n = 33) or post- (males: n = 24, females: n = 36) peak height velocity (PHV) to determine pubertal or 'maturity' status. Three-factor ANOVA was used to identify main and interaction effects of maturity status, biological sex and training status on gCBF andCV R C O 2 ${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Data are reported as group means (SD). Pre-PHV youth demonstrated elevated gCBF and slowerCV R C O 2 ${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ mean response times than post-PHV counterparts (both: P ≤ 0.001). gCBF was only elevated in post-PHV trained males when compared to untrained counterparts (634 (43) vs. 578 (46) ml min-1 ; P = 0.007). However,CV R C O 2 ${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ mean response time was faster in pre- (72 (20) vs. 95 (29) s; P ≤ 0.001), but not post-PHV (P = 0.721) trained youth when compared to untrained counterparts. Cardiorespiratory fitness was associated with gCBF in post-PHV youth (r2  = 0.19; P ≤ 0.001) andCV R C O 2 ${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ mean response time in pre-PHV youth (r2  = 0.13; P = 0.014). Higher cardiorespiratory fitness during adolescence can elevate gCBF while exercise training during childhood primes the development of cerebrovascular function, highlighting the importance of exercise training during the early stages of life in shaping the cerebrovascular phenotype.

Neurovascular coupling and cerebrovascular hemodynamics are modified by exercise training status at different stages of maturation during youth

Neurovascular coupling (NVC) is mediated via nitric oxide signaling, which is independently influenced by sex hormones and exercise training. Whether exercise training differentially modifies NVC pre- versus postpuberty, where levels of circulating sex hormones will differ greatly within and between sexes, remains to be determined. Therefore, we investigated the influence of exercise training status on resting intracranial hemodynamics and NVC at different stages of maturation. Posterior and middle cerebral artery velocities (PCAv and MCAv) and pulsatility index (PCAPI and MCAPI) were assessed via transcranial Doppler ultrasound at rest and during visual NVC stimuli. N = 121 exercise-trained (males, n = 32; females, n = 32) and untrained (males, n = 28; females, n = 29) participants were characterized as pre (males, n = 33; females, n = 29)- or post (males, n = 27; females, n = 32)-peak height velocity (PHV). Exercise-trained youth demonstrated higher resting MCAv (P = 0.010). Maturity and training status did not affect the ΔPCAv and ΔMCAv during NVC. However, pre-PHV untrained males (19.4 ± 13.5 vs. 6.8 ± 6.0%; P ≤ 0.001) and females (19.3 ± 10.8 vs. 6.4 ± 7.1%; P ≤ 0.001) had a higher ΔPCAPI during NVC than post-PHV untrained counterparts, whereas the ΔPCAPI was similar in pre- and post-PHV trained youth. Pre-PHV untrained males (19.4 ± 13.5 vs. 7.9 ± 6.0%; P ≤ 0.001) and females (19.3 ± 10.8 vs. 11.1 ± 7.3%; P = 0.016) also had a larger ΔPCAPI than their pre-PHV trained counterparts during NVC, but the ΔPCAPI was similar in trained and untrained post-PHV youth. Collectively, our data indicate that exercise training elevates regional cerebral blood velocities during youth, but training-mediated adaptations in NVC are only attainable during early stages of adolescence. Therefore, childhood provides a unique opportunity for exercise-mediated adaptations in NVC.NEW & NOTEWORTHY We report that the change in cerebral blood velocity during a neurovascular coupling task (NVC) is similar in pre- and postpubertal youth, regardless of exercise-training status. However, prepubertal untrained youth demonstrated a greater increase in cerebral blood pulsatility during the NVC task when compared with their trained counterparts. Our findings highlight that childhood represents a unique opportunity for exercise-mediated adaptations in cerebrovascular hemodynamics during NVC, which may confer long-term benefits in cerebrovascular function.

Gradistics: An underappreciated dimension in evolutionary space

The growth of complexity is an unsolved and underappreciated problem. We consider possible causes of this growth, hypotheses testing, molecular mechanisms, complexity measures, cases of simplification, and significance for biomedicine. We focus on a general ability of regulation, which is based on the growing information storage and processing capacities, as the main proxy of complexity. Natural selection is indifferent to complexity. However, complexification can be inferred from the same first principle, on which natural selection is founded. Natural selection depends on potentially unlimited reproduction under limited environmental conditions. Because of the demographic pressure, the simple ecological niches become fulfilled and diversified (due to species splitting and divergence). Diversification increases complexity of biocenoses. After the filling and diversification of simple niches, the more complex niches can arise. This is the 'atomic orbitals' (AO) model. Complexity has many shortcomings but it has an advantage. This advantage is ability to regulatory adaptation, including behavioral, formed in the evolution by means of genetic adaptation. Regulatory adaptation is much faster than genetic one because it is based on the information previously accumulated via genetic adaptation and learning. Regulatory adaptation further increases complexity of biocenoses. This is the 'regulatory advantage' (RA) model. The comparison of both models allows testable predictions. We focus on the animal evolution because of the appearance of higher regulatory level (nervous system), which is absent in other lineages, and relevance to humans (including biomedical aspects).

Electrical Remodelling in Cardiac Disease

The human heart responds to various diseases with structural, mechanical, and electrical remodelling processes [...].

Young athlete's growing heart: sex differences in cardiac adaptation to exercise training during adolescence

BACKGROUND

Athlete's heart is a condition of exercise-induced cardiac remodelling. Adult male endurance athletes more often remodel beyond reference values. The impact of sex on remodelling through adolescence remains unclear. Paediatric reference values do not account for patient sex or exercise history. We aimed to study the effect of sex on cardiac remodelling throughout adolescence.

METHODS

We recruited 76 male (M) and female (F) 12-year-old cross-country skiers in a longitudinal cohort study. Echocardiography was performed and analysed according to guidelines at age 12 (48 M, 28 F), 15 (34 M, 14 F) and 18 (23 M, 11 F). Repeated echocardiographic measurements were analysed by linear mixed model regression.

RESULTS

Males displayed greater indexed left ventricular end-diastolic volumes (LV EDVi) from age 12 (M 81±7 vs F 76±7, mL/m², p≤0.01), and progressed further until follow-up at age 18 (M 2.3±9.7 vs F -3.9±4.5 ΔmL/m², p≤0.01). LV EDVi remained above adult upper reference values in both groups. Males increased LV Mass Index from age 12 to 18 (M 33±27 vs F 4±19, Δg/m², p≤0.01). Males displayed LV mass above paediatric reference values at ages 15 and 18. A subset of males (35%) and females (25%) displayed wall thickness above paediatric reference values at age 12. Cardiac function was normal. There was no sex difference in exercise hours.

CONCLUSION

Sex-related differences in athlete's heart were evident from age 12, and progressed throughout adolescence. Remodelling beyond reference values was more frequent than previously reported, particularly affecting males. Age, sex and exercise history may assist clinicians in distinguishing exercise-induced remodelling from pathology in adolescents.

Effects of Sex, Training, and Maturity Status on the Cardiopulmonary and Muscle Deoxygenation Responses during Incremental Ramp Exercise

Whilst participation in regular exercise and sport has generally increased over recent decades globally, fundamental questions remain regarding the influence of growth, maturation, and sex on the magnitude of training response throughout adolescence. Trained (108 participants, 43 girls; age: 14.3 ± 1.8 years) and untrained (108 participants, 43 girls; age: 14.7 ± 1.7 years) adolescents completed an incremental ramp test to exhaustion during which breath by gas exchange, beat-by-beat heart rate (HR), stroke volume (SV) and cardiac output (Q·) and muscle deoxygenation were assessed. Device-based physical activity was also assessed over seven consecutive days. Boys, irrespective of training status, had a significantly higher absolute (2.65 ± 0.70 L min−1 vs. 2.01 ± 0.45 L min−1, p < 0.01) and allometrically scaled (183.8 ± 31.4 mL·kg−b min−1 vs. 146.5 ± 28.5 mL·kg−b min−1, p < 0.01) peak oxygen uptake (V·O2) than girls. There were no sex differences in peak HR, SV or Q· but boys had a higher muscle deoxygenation plateau when expressed against absolute work rate and V·O2 (p < 0.05). Muscle deoxygenation appears to be more important in determining the sex differences in peak V·O2 in youth. Future research should examine the effects of sex on the response to different training methodologies in youth.

JA, Duque L, Chaves-Gomez S, Cristancho-Mejía E, Schmidt WFJ. Hemoglobin Mass, Blood Volume and VO2max of Trained and Untrained Children and Adolescents Living at Different Altitudes

Introduction: To a considerable extent, the magnitude of blood volume (BV) and hemoglobin mass (Hbmass) contribute to the maximum O2-uptake (VO2max), especially in endurance-trained athletes. However, the development of Hbmass and BV and their relationships with VO2max during childhood are unknown. The aim of the present cross-sectional study was to investigate Hbmass and BV and their relationships with VO2max in children and adolescents. In addition, the possible influence of endurance training and chronic hypoxia was evaluated.

Methods: A total of 475 differently trained children and adolescents (girls n = 217, boys n = 258; untrained n = 171, endurance trained n = 304) living at two different altitudes (∼1,000 m, n = 204, ∼2,600 m, n = 271) and 9–18 years old participated in the study. The stage of puberty was determined according to Tanner; Hbmass and BV were determined by CO rebreathing; and VO2max was determined by cycle ergometry and for runners on the treadmill.

Results: Before puberty, there was no association between training status and Hbmass or BV. During and after puberty, we found 7–10% higher values in the trained groups. Living at a moderate altitude had a uniformly positive effect of ∼7% on Hbmass in all groups and no effect on BV. The VO2max before, during and after puberty was strongly associated with training (pre/early puberty: boys +27%, girls +26%; mid puberty: +42% and +45%; late puberty: +43% and +47%) but not with altitude. The associated effects of training in the pre/early pubertal groups were independent of Hbmass and BV, while in the mid- and late pubertal groups, 25% of the training effect could be attributed to the elevated Hbmass.

Conclusions: The associated effects of training on Hbmass and BV, resulting in increased VO2max, can only be observed after the onset of puberty.