Changes in phosphocreatin concentration of skeletal muscle during intensive intermitted exercise in children and adults

Introduction It was shown that children possess a higher resistance to fatigue and a quicker recovery during high-intensive intermittent exercise compared to adults, which is mainly explained by lower blood lactate concentrations and a more stable blood pH (Falk & Dotan, 2006; Ratel et al., 2006). The aim of the present study was to investigate if this can also be explained by the amount and speed of phosphocreatine (PCr) breakdown and resynthesis during and after intensive short-term anaerobic interval work. Methods 16 untrained children (C; 8 girls, 8 boys: 9.2±0.3 yrs; 139±6 cm; 35.8±7.7 kg body mass; 16.6±2.8 kg muscle mass) and 16 untrained adults (A; 8 women, 8 men: 26.1±0.3 yrs, 175±8 cm, 69.1±9.4 kg body mass, 40.1±8.2 kg muscle mass) participated in the study. All subjects completed an intermittent protocol of dynamic plantar flexion followed by 10 min of passive recovery. The protocol consisted of 10 bouts of 30s exercise (24 concentric and eccentric movements) intermitted by 20s recovery. The individual load corresponded to the 28 repetition maximum. We recorded the absolute and relative changes of PCr during exercise and during post exercise recovery by means of non invasive 31P-magnetic resonance spectroscopy as well as the mean force production. Results The results (mean±SD) were calculated using a multi factor ANOVA (main factors were age, sex and measurement time). No significant differences between the age groups were found for the initial PCr concentrations. Average relative PCr break down during each exercise period was significantly lower (p<0.05) in C (-71.4±5.4%) compared to A (-85.8±4.9%). Time constant to reach 63% of initial PCr during post exercise recovery was significantly shorter in children (C: 47±31s, A: 74±33s, p<0.05). Force production relative to maximum values did not differ significantly between C and A. Discussion The results give further explanations for the intermittent exercise performance of children. Our data suggest that children require more aerobic and less anaerobic pathways for ATP production than adults. The lower PCr-breakdown during exercise and the accelerated PCr-resynthesis during recovery point to a better oxygen transport or utilization in the working muscles. This can possibly be attributed to an improved muscle flow after maximum contraction and a greater oxidative mitochondria capacity related to skeletal muscle mass. Coaches should be encouraged to include more short term intensive intermittent work in children´s work out. References Falk B, Dothan R. (2006). Exerc Sport Sci Rev, 34, 107-12. Ratel S, Duché P, Williams CA. (2006). Sports Med, 36, 1031-1065

Screening for sickle cell disease in newborns: a systematic review

Background!#!Sickle cell disease (SCD) is an inherited autosomal recessive disorder caused by the replacement of normal haemoglobin (HbA) by mutant Hb (sickle Hb, HbS). The sickle-shaped red blood cells lead to haemolysis and vaso-occlusion. Especially in the first years of life, patients with SCD are at high risk of life-threatening complications. SCD prevalence shows large regional variations; the disease predominantly occurs in sub-Saharan Africa. We aimed to systematically assess the evidence on the benefit of newborn screening for SCD followed by an earlier treatment start.!##!Methods!#!We systematically searched bibliographic databases (MEDLINE, EMBASE, Cochrane Databases, and the Health Technology Assessment Database), trial registries, and other sources to identify systematic reviews and randomised controlled trials (RCTs) or non-randomised trials on newborn screening for SCD. The last search was in 07/2020. Two reviewers independently reviewed abstracts and full-text articles and assessed the risk of bias of the studies included. Data were extracted by one person and checked by another. As meta-analyses were not possible, a qualitative summary of results was performed.!##!Results!#!We identified 1 eligible study with direct evidence: a Jamaican retrospective study evaluating newborn screening for SCD followed by preventive measures (prevention of infections and education of parents). The study included 500 patients with SCD (intervention group, 395; historical control group, 105). Although the results showed a high risk of bias, the difference between the intervention and the control group was very large: mortality in children decreased by a factor of about 10 in the first 5 years of life (0.02% in the intervention group vs. 0.19% in the control group, odds ratio 0.09; 95% confidence interval [0.04; 0.22], p &amp;lt; 0.001).!##!Conclusion!#!The results are based on a single retrospective study including historical controls. However, the decrease of mortality by a factor of 10 is unlikely to be explained by bias alone. Therefore, in terms of mortality, data from this single retrospective study included in our systematic review suggest a benefit of newborn screening for SCD (followed by preventive measures) versus no newborn screening for SCD (weak certainty of conclusions)