Flexibility of Brazilian children and adolescents: a systematic review of the literature / Flexibilidade de crianças e adolescentes brasileiros: uma revisão sistemática da literatura

abstract Flexibility is related to specific tissue properties of the body, which aim to determine the maximum range of motion of the joints without injury. This study aimed to identify and summarize the evidence on prevalence of adequate levels of flexibility in Brazilian children and adolescents (6 to 19 years old). We performed a systematic search of studies published from 2009 to 2019 in six databases (MEDLINE/PubMed; Scopus; SportDiscus; LILACS; Web of Science; SCIELO). Fourteen studies that compiled data from 11,666 participants in seven different Brazilian states were included. All studies conducted sit and reach tests to assess flexibility. Among all the children and adolescents in the analyzed studies, 58.9% of the total (62.0% of boys and 50.9% of girls) had adequate flexibility. We conclude that more than half of Brazilian children and adolescents have adequate flexibility for health.

resumo A flexibilidade está relacionada com propriedades específicas teciduais que permitem a amplitude máxima de movimento articular sem a presença de lesão. O presente estudo teve como objetivo identificar e sintetizar as evidências sobre a prevalência de níveis adequados de flexibilidade em crianças e adolescentes brasileiros (6 a 19 anos). Foi realizada uma busca sistematizada de estudos publicados de 2009 a 2019 em seis bases de dados (MEDLINE/PubMed; Scopus; SportDiscus; LILACS; Web of Science; SCIELO). Foram incluídos 14 estudos que compilaram dados de 11.666 participantes em sete estados brasileiros diferentes. Todos os estudos realizaram teste de sentar e alcançar para avaliar a flexibilidade. Dentre todas as crianças e adolescentes dos estudos analisados, 58,9% do total (62,0% dos meninos e 50,9% das meninas) apresentaram flexibilidade adequada. Concluímos que mais da metade das crianças e adolescentes brasileiros possuem flexibilidade adequada para a saúde.

Load-matched acute and chronic exercise induce changes in mitochondrial biogenesis and metabolic markers.

We investigated the effects of acute and chronic exercise, prescribed in different intensity zones, but with total load-matched on mitochondrial markers (cytochrome C oxidase subunit IV (COX-IV), mitochondrial transcription factor A (Tfam), and citrate synthase (CS) activity in skeletal muscles, heart, and liver), glycogen stores, aerobic capacity, and anaerobic index in swimming rats. For this, 2 experimental designs were performed (acute and chronic efforts). Load-matched exercises were prescribed below, above, and on the anaerobic threshold (AnT), determined by the lactate minimum test. In chronic programs, 2 training prescription strategies were assessed (monotonous and linear periodized model). Results show changes in glycogen stores but no modification in the COX-IV and Tfam contents after acute exercises. In the chronic protocols, COX-IV and Tfam proteins and CS adaptations were intensity- and tissue-dependent. Monotonous training promoted better adaptations than the periodized model. Training at 80% of the AnT improved both performance variables, emphasizing the anaerobic index, concomitant to CS and COX-IV improvement (soleus muscle). The aerobic capacity and CS activity (gastrocnemius) were increased after 120% AnT training. In conclusion, acute exercise protocol did not promote responses in mitochondrial target proteins. An intensity and tissue dependence were reported in the chronic protocols, highlighting training at 80 and 120% of the AnT. Novelty: Load-matched acute exercise did not enhance COX-IV and Tfam contents in skeletal muscles, heart, and liver. In chronic exercise, COX-IV, Tfam, and CS activity adaptations were intensity- and tissue-dependent. Monotonous training was more efficient than the periodized linear model in adaptations of target proteins and enzymatic activity.

Aerobic and Anaerobic Swimming Force Evaluation in One Single Test Session for Young Swimmers.

This study aims to propose and validate the tethered swimming lactate minimum test (TSLacmin) estimating aerobic and anaerobic capacity in one single test session, using force as measurement parameter. 6 male and 6 female young swimmers (age=15.7±1.1 years; height=173.3±9.5 cm; weight=66.1±9.5 kg) performed 4 sessions comprising i) an all-out 30 s test and incremental test (TSLacmin); ii) 30 min of tethered swimming at constant intensity (2 sessions); iii) free-swimming time trials used to calculate critical velocity. Tethered swimming sessions used an acquisition system enabling maximum (Fmax) and mean (Fmean) force measurement and intensity variation. The tethered all-out test lasting 30 s resulted in hyperlactatemia of 7.9±2.0 mmol·l-1. TSLacmin presented a 100% success applicability rate, which is equivalent to aerobic capacity in 75% of cases. TSLacmin intensity was 37.7±7.3 N, while maximum force in the all-out test was 105±27 N. Aerobic and anaerobic TSLacmin parameters were significantly related to free-swimming performance (r=-0.67 for 100 m and r=-0.80 for 200 m) and critical velocity (r=0.80). TSLacmin estimates aerobic capacity in most cases, and both aerobic and anaerobic force parameters are well related to critical velocity and free swimming performance.

Lactate minimum underestimates the maximal lactate steady-state in swimming mice.

The intensity of lactate minimum (LM) has presented a good estimate of the intensity of maximal lactate steady-state (MLSS); however, this relationship has not yet been verified in the mouse model. We proposed validating the LM protocol for swimming mice by investigating the relationship among intensities of LM and MLSS as well as differences between sexes, in terms of aerobic capacity. Nineteen mice (male: 10, female: 9) were submitted to the evaluation protocols for LM and MLSS. The LM protocol consisted of hyperlactatemia induction (30 s exercise (13% body mass (bm)), 30 s resting pause and exhaustive exercise (13% bm), 9 min resting pause and incremental test). The LM underestimated MLSS (mice: 17.6%; male: 13.5%; female: 21.6%). Pearson's analysis showed a strong correlation among intensities of MLSS and LM (male (r = 0.67, p = 0.033); female (r = 0.86, p = 0.003)), but without agreement between protocols. The Bland-Altman analysis showed that bias was higher for females (1.5 (0.98) % bm; mean (MLSS and LM): 4.4%-6.4% bm) as compared with males (0.84 (1.24) % bm; mean (MLSS and LM): 4.5%-7.5% bm). The error associated with the estimated of intensity for males was lower when compared with the range of means for MLSS and LM. Therefore, the LM test could be used to determine individual aerobic intensity for males (considering the bias) but not females. Furthermore, the females supported higher intensities than the males. The differences in body mass between sexes could not explain the higher intensities supported by the females.