Influence of Endurance Training During Childhood on Total Hemoglobin Mass

Abstract

Elite endurance athletes are characterized by markedly increased hemoglobin mass (Hbmass). It has been hypothesized that this adaptation may occur as a response to training at a very young age. Therefore, the aim of this study was to monitor changes in Hbmass in children aged 8–14 years following systematic endurance training. In the first study, Hbmass, VO2max, and lean body mass (LBM) were measured in 17 endurance-trained children (13 boys and 4 girls; aged 9.7 ± 1.3 years; training history 1.5±1.8 years; training volume 3.5 ± 1.6 h) twice a year for up to 3.5 years. The same parameters were measured once in a control group of 18 age-matched untrained children. Hbmass and blood volume (BV) were measured using the optimized CO-rebreathing technique, VO2max by an incremental test on a treadmill, and LBM by skin-fold measurements. In the second pilot study, the same parameters were measured in 9 young soccer athletes (aged 7.8 ± 0.2 years), and results were assessed in relation to soccer performance 2.5 years later. The increase in mean Hbmass during the period of study was 50% which was closely related to changes in LBM (r = 0.959). A significant impact of endurance training on Hbmass was observed in athletes exercising more than 4 h/week [+25.4 g compared to the group with low training volume (<2 h/week)]. The greatest effects were related to LBM (11.4 g·kg−1 LBM) and overlapped with the effects of age. A strong relationship was present between absolute Hbmass and VO2max (r = 0.939), showing that an increase of 1 g hemoglobin increases VO2max by 3.6 ml·min−1. Study 2 showed a positive correlation between Hbmass and soccer performance 2.5 years later at age 10.3 ± 0.3 years (r = 0.627, p = 0.035). In conclusion, children with a weekly training volume of more than 4 h show a 7% higher Hbmass than untrained children. Although this training effect is significant and independent of changes in LBM, the major factor driving the increase in Hbmass is still LBM.

Effect of Endurance Training on Hemoglobin Mass and V˙O2max in Male Adolescent Athletes

“…In contrast to the abovementioned investigations, Prommer et al (17) very recently showed an effect of the activity level in children on the development of Hb mass (7% increase after 2.5 yr with >4 h of training per week) independent of physical growth. However, these findings are, on the one hand, based on young (preadolescent) children and, on the other hand, are equivocal to the training effect, since a longitudinal control group was missing.…”

“…All cardiovascular variables were scaled to LBM to account for general anthropometric growth in the observed age range and to correct for different amounts of body fat (17,28).…”

“…From recent cross-sectional data (5,16–18), it can be concluded that endurance-trained children and adolescent endurance-trained athletes have ~15% to 35% lower Hb mass than adult athletes. There seems to be an increase of body weight-related Hb mass with maturation from 9.6 g·kg −1 in 9.7-yr-old children (17) to 10.6 g·kg −1 in 13.8-yr-old cyclists (19) to 12.0–12.4 g·kg −1 in endurance-trained male adolescents at age 16 yr (5,18). An upregulation of testosterone levels in boys during adolescence is a likely explanation of this training-independent increase, because there exists a close relationship between androgen levels and hemoglobin (Hb) concentration in puberty (20).…”

A 2-year longitudinal follow-up of performance characteristics in Chinese male elite youth athletes from swimming and racket sports

“…The mean values for the [Hb] of the athletes of the three sports groups showed an average yearly increase of 4.4% in the swimmers, and 6.5% in the racket sports players, which was similar to published data for Hbmass, showing a mean value of ~430 g in 11–13-yr-old boys and ~370 g in 12–13-yr-old girls and boys [ 12 ]. Despite the general increase in hemoglobin mass with age, Prommer et al [ 11 ] did not find an independent statistical effect of age on Hbmass because, in their study, the effects fully overlapped with those of lean body mass (LBM) in such way that a 1 kg increase in LBM was associated with a 14.7 g increase in Hbmass. As literature has stressed the close relationship between the circulating testosterone levels and [Hb] [ 55 ], this leads to the hypothesis, that also the increase of [Hb] in young athletes is primarily affected by androgens [ 56 – 58 ].…”

“…Elite endurance athletes as well as elite game sport participants are characterized by a markedly increased O 2 transport capacity, hemoglobin concentration [Hb] and hemoglobin mass (Hbmass) [10,11]. Hbmass and hemoglobin concentration [Hb] belong to the major limiting factors of maximum endurance performance.…”