Comparison of physical fitness in youth with post-COVID-19: A study of individuals with and without symptoms

In type 1 diabetes, telomere length (TL) may predict complications and could be influenced by glycaemic control and physical activity, but its relationship with physical fitness in youths remains unexplored. The aim of the study was to assess the association between physical fitness and TL in youth with type 1 diabetes, both at baseline and one year later. Eighty-three children and adolescents (aged 6-18 years; 44.6% girls) with type 1 diabetes from the Diactive-1 Cohort Study were involved in this study. Physical fitness was assessed using spirometry on a cycloergometer (i.e., peak oxygen consumption), dynamometry, and maximal isometric strength (one-repetition maximum [1RM]), and muscle power. Leucocyte TL was assessed using multiplex monochrome real-time quantitative polymerase chain reaction. Positive cross-sectional associations were identified between 1RM (unstandardized beta coefficient [B]= 0.042, 95% bias corrected and accelerated [BCa] confidence interval [CI] 0.012-0.069), muscle power (B = 0.056, 95% BCa CI 0.02-0.250), and overall physical fitness (B = 0.043, 95% BCa CI 0.015-0.071) with TL independent of maturation, glycated haemoglobin, and diabetes duration. However, no associations were observed one year later. Higher levels of fitness, particularly musclestrength, may play a role in telomere dynamics in youth with type 1 diabetes, suggesting that strength training exercise could be beneficial. This is the first study to examine cross-sectional and longitudinal perspectives on the correlation among muscle strength, peak oxygen consumption [VO2peak] and telomere length in youths with type 1 diabetes. Higher physicalfitness levels, as assessed by measures such as one-repetition maximum, muscle power, and overall physical fitness, are positively associated with telomere length in youths with type 1 diabetes. Understanding this link could improve management strategies, prioritizing muscle strength training for better long-term health in type 1 diabetes.

Short term secular change in body size and physical fitness of Polish youth 7-15 years of age resident in an industrial region of Lower Silesia in southwestern Poland was considered across two surveys, 2001-2002 and 2010-2011. Subjects were students in the same schools in both surveys 1892 boys and 1992 girls in the first and 1237 boys and 1236 girls in the second. In addition to height and weight, performances in six fitness tests were measured in each survey. Height, weight and BMI increased significantly across surveys. Statistically controlling for secular gains in height and weight, only static strength (hand grip) and running speed - agility (shuttle run) improved significantly between surveys in three age groups (7-9, 10-12, 13-15 years), while explosive power (standing long jump) showed negligible changes except in girls 13-15 years among whom performances declined significantly. Speed of upper limb movement (plate tapping), flexibility (sit and reach) and trunk strength (sit-ups) declined between surveys, except for trunk strength in boys 13-15 years which did not change. In conclusion, after statistically controlling for secular gains in body size, physical fitness items changed variably over the decade.

ObjectivesDespite the health importance of identifying correlates of physical fitness in youth, no investigation to date has explored the influence of behavioral, health-related, and contextual correlates simultaneously. We investigated the hierarchical relationship of multiple modifiable correlates favoring or diminishing cardiorespiratory and muscular fitness in youth. DesignCross-sectional investigation. MethodsIn a sample of 5174 children and adolescents, 31 correlates were hierarchized according to their impact on cardiorespiratory and muscular fitness assessed using the FITESCOLA® fitness battery. A Chi-squared Automatic Interaction Detection approach was employed and measures of correlation and association were used to investigate the relationship between physical fitness and correlates. ResultsIn children, body mass index was the most relevant factor to discriminate between high and low cardiorespiratory and muscular fitness of the upper, middle, and lower body. While body mass index was more important than any other correlate to differentiate levels of upper and lower body muscular fitness during adolescence, specific characteristics of sports participation emerged as key factors to discriminate between high and low cardiorespiratory fitness and middle body muscular fitness. Other correlates, including the self-report of active recess time, active commuting to school, favorable neighborhood conditions, and limited time on screens and cellphones, were demonstrative of favorable physical fitness levels. ConclusionsBoth body composition and sports-related characteristics emerged as the two most relevant factors of physical fitness in youth. Additional health benefits may be obtained from building supportive environments for sports and healthy exercise habits within the household and at different school education levels.

Physical activity (PA) and sedentary behaviors have been associated with various health outcomes in youth, including overweight/obesity and physical fitness. Limited information, however, is available on the independent association between TV time and physical fitness in children and adolescents. A total of 3,293 (55.1% male) youth between 6 and 14 years of age were randomly selected from 29 Austrian schools. Body weight and height were measured according to standard procedures and BMI percentiles were determined based on German reference values. Physical fitness was assessed with the German Motor test (DMT6-18), which evaluates cardiorespiratory endurance, muscular strength, power, strength endurance, agility, speed and flexibility. Information on daily TV time and participation in club sports was obtained via standardized questionnaires. Participants were 9.8±2.3 years of age and almost half of them (48.5%) reported a TV time >2 hours/d. TV time increased significantly with age. High TV consumption was associated with significantly lower physical fitness and these results remained after adjusting for body weight. Youth exceeding current TV time recommendations had a 60% higher risk of having poor or very poor fitness compared to those with a TV time <2 hours/day. High TV time is associated with poor physical fitness in youth. Accordingly, intervention strategies need to target a meaningful utilization of TV and other screen-based activities in addition to the promotion of PA in order to ensure sufficient physical fitness in youth.

ABSTRACTThe aims of the present study were: i) to examine the associations of total accelerometer-based sedentary time (ST) and specific-domain self-reported ST (i.e., screen-based, educational-based, social-based, and other-based ST) with adiposity and physical fitness in youth; and ii) to analyse the mediation effect of physical activity (PA) on associations.This study was conducted with 415 children (9.1 ± 0.4 years) and 853 adolescents (13.6 ± 1.6 years) in Spain during 2011–2012. Total ST and PA were assessed by accelerometry. Leisure-time spent in twelve sedentary behaviours was self-reported. Adiposity and physical fitness was measured following the ALPHA battery for youth.Total accelerometer-based ST was positively associated with global adiposity score in children, and negatively associated with global physical fitness score in children and adolescents; but relationships were not independent of PA. PA mediated all associations of accelerometer-based and self-reported ST with adiposity or physical fitness in children. Conversely, screen-, educational-, social-, and other-based ST were negatively related to physical fitness in adolescents, independently of PA.These findings give an impetus to developing effective strategies for specifically promoting PA in children and for increasing PA while reducing ST in adolescents in order to produce improvements on adiposity and physical fitness.

It is unknown whether a concentrated period of small-sided games and high intensity training is an effective training approach in youth soccer players. The aim of the study was to examine the effect of a concentrated period of soccer specific training on physical fitness in youth players. Nineteen male soccer players, from two teams, participated (mean age: 16.2±0.8 years; body mass: 58.2±7.6 kg; height: 170.8±7.7 cm). One team performed 5 days of small-sided games and high intensity training (SSG & HIT; N.=12) and the other team regular soccer training with 1 day of SSG and HIT (REG; N.=7) weekly for 4 weeks. The 30-15 intermittent fitness test (30-15 IFT), countermovement jump (CMJ) and change of direction (COD) performance were measured pre and post intervention. Heart rate (HR) and rating of perceived exertion (RPE) were recorded and session load calculated (RPE x minutes). Average percentage of maximum HR and session load were 83% and 344 AU for the SSG & HIT versus 73% and 253 AU for the REG (P<0.05). 30-15 IFT improved for the SSG & HIT (from 17.0±1.1 to 18.4±0.8 km/h; P<0.05; ES=0.57) with no difference for the REG group (Pre: 17.9±1.3, Post: 18.2±1.6 km/h, ES=0.10). CMJ and COD were unchanged in both groups and no injuries were reported. A 4-week concentrated period of daily SSG & HIT is effective for improving endurance performance in youth soccer players. This was without injuries and without negating performance in power and change of direction.

[This corrects the article DOI: 10.1371/journal.pone.0205525.].

IntroductionTo date, several meta-analyses clearly demonstrated that resistance and plyometric training are effective to improve physical fitness in children and adolescents. However, a methodological limitation of meta-analyses is that they synthesize results from different studies and hence ignore important differences across studies (i.e., mixing apples and oranges). Therefore, we aimed at examining comparative intervention studies that assessed the effects of age, sex, maturation, and resistance or plyometric training descriptors (e.g., training intensity, volume etc.) on measures of physical fitness while holding other variables constant.MethodsTo identify relevant studies, we systematically searched multiple electronic databases (e.g., PubMed) from inception to March 2018. We included resistance and plyometric training studies in healthy young athletes and non-athletes aged 6 to 18 years that investigated the effects of moderator variables (e.g., age, maturity, sex, etc.) on components of physical fitness (i.e., muscle strength and power).ResultsOur systematic literature search revealed a total of 75 eligible resistance and plyometric training studies, including 5,138 participants. Mean duration of resistance and plyometric training programs amounted to 8.9 ± 3.6 weeks and 7.1±1.4 weeks, respectively. Our findings showed that maturation affects plyometric and resistance training outcomes differently, with the former eliciting greater adaptations pre-peak height velocity (PHV) and the latter around- and post-PHV. Sex has no major impact on resistance training related outcomes (e.g., maximal strength, 10 repetition maximum). In terms of plyometric training, around-PHV boys appear to respond with larger performance improvements (e.g., jump height, jump distance) compared with girls. Different types of resistance training (e.g., body weight, free weights) are effective in improving measures of muscle strength (e.g., maximum voluntary contraction) in untrained children and adolescents. Effects of plyometric training in untrained youth primarily follow the principle of training specificity. Despite the fact that only 6 out of 75 comparative studies investigated resistance or plyometric training in trained individuals, positive effects were reported in all 6 studies (e.g., maximum strength and vertical jump height, respectively).ConclusionsThe present review article identified research gaps (e.g., training descriptors, modern alternative training modalities) that should be addressed in future comparative studies.

ABSTRACTThis study examined the associations between socioeconomic status (SES) and musculoskeletal (MSF) and cardiorespiratory fitness (CRF) in youth. The sample consisted of boys and girls between 3-15 years. SES was categorized utilizing family-income-to-poverty ratio (FIPR). All analyses were standardized for age and sex. For each test of physical fitness, SES was used to estimate mean fitness test percentile and 95% confidence intervals, controlling for race/ethnicity and physical activity. Odds ratios were calculated for the likelihood of having low fitness by SES category. In general, the high SES group had a better composite MSF, body composition, and CRF profiles than low and moderate SES groups. Statistically significant differences were identified for relative grip strength, plank, body mass index, and cardiovascular endurance time (all p < 0.05). Additionally, the odds of low/poor MSF fitness were 1.7 and 1.6 times higher in the low and moderate SES groups (respectively) compared to the children from high SES families. The moderate SES group had an odds of poor CRF 1.6 times higher than the high SES group as well. Children and adolescents from high SES families tend to have higher mean fitness and were less likely to have low/poor fitness.

Various models and methods have been proposed to address the worldwide decline in children's and youth's physical fitness, and the social-ecological model has shown some promise. Yet, the impact of the policy intervention, 1 component of that model, has not been evaluated carefully. Using limited data from policy documents, the impact of policy related to children and youth fitness in China was examined, and it was found that the policy alone did not seem to work. Possible reasons are explored, and a call for more policy evaluation research is made.

BackgroundEarlier studies have shown that balance training (BT) has the potential to induce performance enhancements in selected components of physical fitness (i.e., balance, muscle strength, power, speed). While there is ample evidence on the long-term effects of BT on components of physical fitness in youth, less is known on the short-term or acute effects of single BT sessions on selected measures of physical fitness.ObjectiveTo examine the acute effects of different balance exercise types on balance, change-of-direction (CoD) speed, and jump performance in youth female volleyball players.MethodsEleven female players aged 14 years participated in this study. Three types of balance exercises (i.e., anterior, posterolateral, rotational type) were conducted in randomized order. For each exercise, 3 sets including 5 repetitions were performed. Before and after the performance of the balance exercises, participants were tested for their static balance (center of pressure surface area [CoP SA] and velocity [CoP V]) on foam and firm surfaces, CoD speed (T-Half test), and vertical jump height (countermovement jump [CMJ] height). A 3 (condition: anterior, mediolateral, rotational balance exercise type) × 2 (time: pre, post) analysis of variance was computed with repeated measures on time.ResultsFindings showed no significant condition × time interactions for all outcome measures (p > 0.05). However, there were small main effects of time for CoP SA on firm and foam surfaces (both d = 0.38; all p < 0.05) with no effect for CoP V on both surface conditions (p > 0.05). For CoD speed, findings showed a large main effect of time (d = 0.91; p < 0.001). However, for CMJ height, no main effect of time was observed (p > 0.05).ConclusionsOverall, our results indicated small-to-large changes in balance and CoD speed performances but not in CMJ height in youth female volleyball players, regardless of the balance exercise type. Accordingly, it is recommended to regularly integrate balance exercises before the performance of sport-specific training to optimize performance development in youth female volleyball players.Trial registrationThis study does not report results related to health care interventions using human participants and therefore it was not prospectively registered.

BackgroundStrong evidence indicates that moderate-vigorous physical activity (MVPA) is positively associated with fitness in youth, independent of total sedentary-time. Sedentary-time appears negatively associated with fitness only when it replaces MVPA. However, whether different sedentary-patterns affect health-related fitness is unknown.MethodsThe associations between MVPA and sedentary-patterns with physical fitness were examined in 2698 youths (1262 boys) aged 13.4 ± 2.28 years. Sedentary-time (counts · minute−1 < 100) and PA were objectively measured by accelerometry. Each break (≥100 counts · min−1 < 2295) in sedentary-time and the frequency of daily bouts in non-prolonged (<30 min) and prolonged (≥30 min) sedentary-time were determined. The FITNESSGRAM® test battery was used to assess fitness. A standardized fitness composite-score (z-score) was calculated by summing the individual z-scores of the five tests adjusted to age and sex.ResultsPositive associations between MVPA and fitness were observed in both boys (β = 0.013, 95% CI: 0.005; 0.021) and girls (β = 0.014, 95% CI: 0.006; 0.022), independent of sedentary-patterns. Modest associations were found for the breaks in sedentary-time with fitness (β = 0.026, 95% CI: 0.009; 0.042), independent of total sedentary-time and MVPA in boys. In girls, non-prolonged sedentary bouts were positively associated with fitness (β = 0.014, 95% CI: 0.003; 0.024), independent of total sedentary-time and MVPA.ConclusionsThese results reinforce that, independent of the time and patterns of sedentary behavior, MVPA is consistently associated with fitness in youth. Modest and inconsistent associations were found for sedentary behaviors. Breaking-up sedentary-time in boys and non-prolonged sedentary bouts in girls were positively associated with fitness, independent of total sedentary-time and MVPA. In order to enhance youth’s fitness, public health recommendations should primarily target MVPA, still, suggestion to reduce and break-up sedentary-time may also be considered.

In this issue, Sacheck and Hall discussed the key findings from the Final Report “Fitness Measures and Health Outcomes in Youth” developed by an expert committee appointed by the Institute of Medicine in 2011 and published in 2012. The findings from this report are more valuable when interpreted together with those from the EU-funded ALPHA project (conducted from 2007 to 2010). The ALPHA project aimed to provide an evidence-based set of valid, reliable, feasible, and safe field-based fitness tests for the assessment of health-related physical fitness in youth to be used in public health monitoring in a comparable way within the European Union and around the globe. The ALPHA team conducted 4 reviews (3 of them systematic reviews) and 11 methodological studies, tested the battery in the school setting, and had several meetings with an international expert board to further discuss the development of the work. The evidence-based ALPHA fitness test battery was finally published in 2011. Several important methodological issues related to fitness assessment and its clinical value mainly derived from this project are discussed in the present article: the ALPHA-fitness test battery; Slaughter’s equations and normalization of fat indicators by height; absolute versus relative muscular strength; physical fitness reference data; health-related fitness cut-points; Self-reported fitness assessment: The International FItness Scale-IFIS; and fitness assessment in preschoolers: The PREFIT project.

Developmental perspectives on motor competence and physical fitness in youth.

Introduction: Monitoring of physical fitness in youth is important because physical fitness is a summative indicator of health. From a developmental and preventive perspective, physical fitness levels are relatively stable from childhood to early adulthood. Thus, it is important to monitor physical fitness on a population based level being able to intervene at early stages (1). In order to reliably assess and evaluate the physical fitness of youth, a reliable system of standard values based on representative data is required. The aim of this analysis is to report sex- and age-specific physical fitness percentile curves from childhood to early adulthood in a nationwide sample in Germany.Methods: We use data from the nationwide representative Motorik Modul (MoMo) Study in Germany (data collection wave 1: 2009–2012; age: 4–23 years; n = 3,742; 50.1% female). Physical fitness was assessed by means of the MoMo test profile covering four dimensions of physical fitness (strength, endurance, coordination, and flexibility) and including eight physical fitness items. Percentile curves were fitted using the LMS transformation method of Cole and Green.Results: Standardized age- and sex-specific physical fitness percentiles were calculated for eight items: ergometric endurance testing, standing long jump, push-ups, sit-ups, jumping side-ways, balancing backwards, static stand, and stand and reach test. The physical fitness curves differ according to gender and the fitness dimension. Physical fitness improvements with age are linear (e.g., max. strength) or curvilinear (e.g., coordination) and have their stagnation points at different times over the course of adolescence.Discussion: Our results provide for the first time sex- and age-specific physical fitness percentile curves for Germany from 4 to 17 years. Differences in curve-shapes indicating a timed and capacity-specific physical fitness development. Nationwide German physical fitness percentiles can be useful in comparing different populations (e.g., cross-country), reporting secular trends, comparing special groups, and to evaluate physical fitness interventions.