Comparisons between dual-energy X-ray absorptiometry and bioimpedance devices for appendicular lean mass and muscle quality in Hispanic adults.

The purpose of this study was to compare single- and multi-frequency bioimpedance (BIA) devices against dual-energy X-ray absorptiometry (DXA) for appendicular lean mass (ALM) and muscle quality index (MQI) metrics in Hispanic adults. One hundred thirty-one Hispanic adults (18-55 years) participated in this study. ALM was measured with single-frequency bioimpedance analysis (SFBIA), multi-frequency bioimpedance analysis (MFBIA) and DXA. ALMTOTAL (left arm + right arm + left leg + right leg) and ALMARMS (left arm + right arm) were computed for all three devices. Handgrip strength (HGS) was measured using a dynamometer. The average HGS was used for all MQI models (highest left hand + highest right hand)/2. MQIARMS was defined as the ratio between HGS and ALMARMS. MQITOTAL was established as the ratio between HGS and ALMTOTAL. SFBIA and MFBIA had strong correlations with DXA for all ALM and MQI metrics (Lin's concordance correlation coefficient values ranged from 0·86 (MQIMFBIA-ARMS) to 0·97 (Arms LMSFBIA); all P < 0·001). Equivalence testing varied between methods (e.g. SFBIA v. DXA) when examining the different metrics (i.e. ALMTOTAL, ALMARMS, MQITOTAL and MQIARMS). MQIARMS was the only metric that did not differ from the line of identity and had no proportional bias when comparing all the devices against each other. The current study findings demonstrate good overall agreement between SFBIA, MFBIA and DXA for ALMTOTAL and ALMARMS in a Hispanic population. However, SFBIA and MFBIA have better agreement with DXA when used to compute MQIARMS than MQITOTAL.

Longitudinal Associations Between Enjoyment of Physical Education, Cardiorespiratory Fitness, and Muscular Fitness Among Finnish Adolescents.

INTRODUCTION: Students' experiences in physical education (PE) can shape future physical activity (PA) behaviors. PE enjoyment is associated with PA; however, the relationship between PE enjoyment and fitness has not been extensively investigated. The aim of this study was to examine if changes in PE enjoyment were associated with changes in cardiorespiratory fitness (CRF) and muscular fitness (MF) among Finnish adolescents. METHODS: Study participants were students (n = 1147; 11.27 [±0.32] years at baseline) attending public schools in Finland. Data were collected yearly (2017-2021). The 20 m shuttle run assessed CRF, curl-up/push-up tests assessed MF, and the enjoyment subscale of the Sport Commitment Questionnaire-2 measured PE enjoyment. The random intercept cross-lagged panel model, including repeated measures (within-level) and latent levels (between-level) of PE enjoyment, CRF and MF, was tested. Sex, body mass index, moderate to vigorous PA, and peak height velocity were included as covariates in the analysis. RESULTS: Over 5 years, PE enjoyment decreased, CRF increased until Timepoint 3, and MF remained stable. Positive associations between PE enjoyment and fitness were observed, indicating the greater the PE enjoyment, the higher the fitness. For PE enjoyment, CRF and MF repeated measures were positively associated with measurement of the next year. PE enjoyment was positively related to CRF and MF the years thereafter. CONCLUSION: Our findings highlight the importance of quality PE experiences for enjoyment and fitness gains during the transition from primary to secondary school. These findings are important given youth fitness levels are associated with future health status.

Moderating role of 1-minute abdominal test in the relationship between cardiometabolic risk factors and adiponectin concentration in adolescents.

BACKGROUND: Adiponectin is an anti-inflammatory cytokine secreted by adipose tissue, has been associated with adiposity and cardiometabolic risk, and has controversial results with muscular fitness. The aim of this study was to analyze the interaction of 1-minute abdominal test in the relationship between adiposity, body composition, cardiometabolic risk and adiponectin concentration in adolescents. METHODS: This is a cross-sectional study conducted with 62 adolescents of both sexes, aged 11 to 16 years, approved by the Ethics Committee of Research in Humans (CAEE: 62963916.0.0000.5223). Body mass, height, abdominal circumference (AC), waist circumference (WC), fat mass (FM), fat-free mass (FFM), high density lipoprotein (HDL-c), low density lipoprotein (LDL-c), triglycerides (TG), adiponectin, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean blood pressure (MBP), 1-minute abdominal test (ABD) were measured. Body mass index (BMI), z-score BMI (BMI-z), triponderal mass index (TMI), and waist-to-height ratio (WHtR) were calculated. The macro PROCESS for SPSS v.24.0 was used for moderation analyses, with linear regression models. RESULTS: Inverse interactions were found for adiposity (BMI, BMI-z, TMI, AC, WC, WHtR), body composition (FM, FFM) and CMRF (SBP, DBP, MBP, TG) versus 1-minute abdominal test with adiponectin concentration, demonstrating that abdominal test is a moderator in these relationships. CONCLUSION: We conclude that 1-minute abdominal test may play an important role in the relationship between obesity and cardiometabolic risk. We found that muscular fitness can confer a protective effect on adolescents with high levels of abdominal test.

The impact of reduced muscular fitness on cardiometabolic risk factors in children aged 9-11 years.

AIM: To analyse the relationships between muscular fitness (MF), fat mass (FM), fat-free mass (FFM) and its combined ratio with cardiometabolic risk (CMR) and whether the relationship between MF and CMR is mediated by body composition in schoolchildren. METHODS: A cross-sectional study was conducted on schoolchildren from Cuenca, Spain, between September and November 2017. FM and FFM were estimated using bioimpedance analysis. The CMR index was calculated from triglycerides-HDL-c ratio, arterial pressure and fasting insulin. The MF index was assessed using handgrip and standing long jump tests. Analysis of covariance models assessed CMR index differences across the MF index and the FM/FFM ratio categories. Mediation analysis examined whether the MF index and the CMR index association were mediated by FM, FFM or FM/FFM ratio. RESULTS: The analyses involved 485 schoolchildren aged 9-11 years (55.4% girls). Children with a higher MF index had a lower CMR index (p < 0.05). This association did not persist after controlling for FM/FFM. FM, FFM and FM/FFM ratio mediated the relationship between the MF index and the CMR index. CONCLUSION: Better levels of MF are associated with better cardiometabolic profile, but a healthy body composition is determinant to improve future health.

Integrating Resistance Training Into Secondary School Physical Education Lessons: Effects of a 6-Week Intervention on Athletic Motor Skill Competencies.

PURPOSE: The purpose of this study was to examine the effects of resistance training (RT) in physical education lessons on athletic motor skill competencies in secondary school children. METHOD: Seventy-eight males were randomized into experimental year groups or a control group. Experimental groups participated in RT during physical education lessons for a 6-week half-term. The control group continued with their games-based curriculum. Countermovement jump (CMJ) height, seated medicine ball throw (SMBT) distance, and RT skills battery scores were measured preintervention and postintervention. RESULTS: All experimental groups significantly improved SMBT distance and RT skills quotient (P < .05). All intervention year groups also significantly improved CMJ height (P < .05), except for year 9. Although the control group did not show improvements in CMJ height and RT skills quotient, there was a significant improvement in SMBT distance (P < .05). The year 7 and 8 males exhibited greater improvements in CMJ height and SMBT distance (d = 0.21-0.79) than in year 9 (d = 0.00-0.40). CONCLUSION: Results of the study indicated that a 6-week half-term RT intervention in physical education lessons can improve athletic motor skill competencies (P < .05, d = 0.21-2.51) in male youths.

The Impact of Personalized versus Standardized Cardiorespiratory and Muscular Training on Health-Related Outcomes and Rate of Responders.

Recent research has shown more favorable training adaptations for inactive adults when cardiorespiratory fitness (CRF) exercise is prescribed with the use of ventilatory thresholds compared to percentages of heart rate reserve (HRR). However, there is limited research on changes in health-related outcomes with the use of these CRF methods in combination with muscular fitness exercises. The objective of this study was to compare the effectiveness of two training programs for improving CRF, muscular fitness, and cardiometabolic risk factors. Inactive men and women (n=109, aged 49.3±15.5 years) were randomized to a non-exercise control group or one of two exercise training groups. The exercise training groups consisted of 13 weeks of structured exercise with progression using either CRF exercise prescribed with the use of ventilatory thresholds and functional training for muscular fitness (THRESH group) or HRR and traditional muscular fitness training (STND group). After the 13-week protocol, there were significant differences in body weight, body composition, systolic blood pressure, high-density lipoprotein cholesterol (HDL-c), VO2max, 5-repetition maximum (RM) bench press, and 5-RM leg press for both treatment groups compared to the control group after controlling for baseline values. However, the THRESH group had significantly more desirable outcomes for VO2max, 5-RM bench press, 5-RM leg press, body composition, and HDL-c when compared to both the STND and control group. Additionally, the proportion of individuals estimated as likely to respond above 3.5 mL·kg-1·min-1 in VO2max (i.e., the minimal clinically important difference) was 76.4%, 20.8%, and 0.13% for the THRESH, STND, and control groups, respectively. While both exercise programs elicited favorable health-related adaptations after 13 weeks, these results suggest that a personalized program with exercise prescribed based on ventilatory threshold and with the use of functional muscular fitness training may yield greater training adaptations.

Relationship between health-related quality of life and physical fitness in Norwegian adolescents.

AIMS: This cross-sectional study investigated the association between health-related quality of life (HRQoL), cardiorespiratory fitness (CRF) and muscular fitness in 14-year-old adolescents. METHODS: Norwegian adolescents (N = 1985) carried out a 10-min running test to assess cardiorespiratory fitness and three different muscular fitness tests (handgrip, sit-ups, and standing broad jump) and answered the KIDSCREEN-27 questionnaire to provide HRQoL data. Linear-mixed effect models were applied to detect relationships among the variables. RESULTS: Running-test results were positively associated with higher scores in the following KIDSCREEN domains: physical well-being, psychological well-being, autonomy and parent relationships, and school environment (ß = 0.01-0.04; p < .01 for all). Performance in sit-ups test was positively associated with higher scores in three out of five KIDSCREEN domains: physical well-being (ß = 0.31; p < .001), social support and peers (ß = 0.16; p = .023), and school environment scores (ß = 0.19; p = .006). An inverse association was found between the handgrip test results and the score on psychological well-being domain (ß = - 0.10; p = .013). CONCLUSIONS: The associations between HRQoL and physical fitness were trivial (abdominal strength and handgrip strength) to small (CRF) but confirmed that earlier findings from children also are applied to adolescents. Explosive strength in the lower body showed no association with HRQoL. Further research should investigate the direction of causality. TRIAL REGISTRATION: Clinicaltrials.gov ID nr: NCT03817047. Registered 01/25/2019 'retrospectively registered'.

Short-Term Muscle Power Is Related to Lower Limb Muscle Volume in Young Children.

PURPOSE: Muscle power is a component of muscular fitness and is proportional to its volume. Reduced muscular fitness in children is linked to negative health outcomes. Associations between muscle volume (MV) and power have not been examined in young children and could reveal important insights into early neuromuscular development. METHOD: Forty-four children (2-8 y) completed 3 tests of short-term muscular power: repeated anaerobic sprint test, vertical jump, and horizontal jump. MV was assessed using 3D ultrasound for 3 lower limb muscles (rectus femoris, medial gastrocnemius, and tibialis anterior) and summed for across legs. Associations between muscular power and summed MV were assessed using Pearson correlation (r). Sex-based differences in muscular power and MV were assessed using 1-way analysis of covariance. RESULTS: Moderate-strong associations (r = .57 - .87) were found between muscular power and summed MV. No differences were found between boys and girls for height, weight, MV, or muscular power. CONCLUSIONS: Young children who have larger lower limb muscles perform better at tasks dependent on short-term muscular power, such as running and jumping, compared with children with smaller muscles. Sex-based differences in short-term muscular power do not exist in young children and reflect similar anthropometry, including lower limb MV.

Acute and chronic functional and traditional resistance training improve muscular fitness in young males via the AMPK/PGC-1α/irisin signaling pathway.

BACKGROUND: In this study, we aimed to investigate the effects of acute and chronic resistance training of varying intensities on molecular responses and their association with muscular fitness in a cohort of young males who participated in this intervention study. METHODS: Young males (19-28 years) with no prior training experience underwent a six-week program consisting of two distinct modalities of resistance training. The participants were randomly divided into a functional resistance training group (FRT; n = 9; participants performed 4-5 sets of 20 repetitions maximum (RM) at 40% 1RM) or a traditional resistance training group (TRT; n = 9; participants performed 4-5 sets of 12 RM at 70% 1RM). Both protocols entailed training three days per week for six weeks. Blood samples were obtained before, immediately after an acute bout of training, and after the six-week training program to determine alterations in molecular responses. Muscular fitness analysis and anthropometric measurements were conducted before and after the six-week training program. RESULTS: After the six-week training program, the lean body mass of participants in both TRT and FRT groups was significantly increased (p < 0.05), whereas body fat percentage and fat mass were significantly decreased solely in the FRT group (p < 0.05). All muscular fitness variables were significantly increased in both groups (p < 0.01), with no difference between the two groups. Additionally, in the TRT group, serum levels of AMP-activated protein kinase (AMPK) were significantly increased following acute training and six weeks of resistance training, whereas in the FRT group, no significant increase in serum levels of AMPK was observed. In both groups, serum levels of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), irisin, and insulin-like growth factor-1 were significantly increased. Moreover, myostatin was significantly decreased following acute training and six weeks of resistance training (p < 0.05), with no difference between the two groups. Furthermore, a significant correlation was observed between barbell back squat and certain molecular variables. CONCLUSIONS: Overall, our study indicates that acute and chronic resistance training of varying intensities are effective changing molecular responses, the chronic FRT and TRT improve muscular fitness in young males through the AMPK/PGC-1α/irisin signaling pathway. TRIAL REGISTRATION: Chinese Clinical Trial Registry: ChiCTR2200059775 (11/05/2022).

Is adherence to the Mediterranean diet associated with healthy habits and physical fitness? A systematic review and meta-analysis including 565 421 youths.

The relationship between adherence to the Mediterranean diet (MD), physical activity (PA), sedentary behaviour and physical fitness levels has been analysed in several studies; however, there is mixed evidence among youth. Thus, this study aimed to meta-analyse the associations between adherence to the MD, PA, sedentary behaviour and physical fitness among children and adolescents. Three databases were systematically searched, including cross-sectional and prospective designs with a sample of healthy youth aged 3-18 years. Random effects inverse-variance model with the Hartung-Knapp-Sidik-Jonkman adjustment was used to estimate the pooled effect size (correlation coefficient (r)). Thirty-nine studies were included in the meta-analysis, yielding a total of 565 421 youth (mean age, 12·4 years). Overall, the MD had a weak-to-moderate positive relationship with PA (r 0·14; 95 % CI 0·11, 0·17), cardiorespiratory fitness (r 0·22; 95 % CI 0·13, 0·31) and muscular fitness (r 0·11; 95 % CI 0·03, 0·18), and a small-to-moderate negative relationship with sedentary behaviour (r -0·15; 95 % CI -0·20, -0·10) and speed-agility (r -0·06; 95 % CI -0·12, -0·01). There was a high level of heterogeneity in all of the models (I2 ≥ 75 %). Overall, results did not remain significant after controlling for sex and age (children or adolescents) except for PA. Improving dietary habits towards those of the MD could be associated with higher physical fitness and PA in youth, lower sedentary behaviours and better health in general.

Relationship between physical activity and depressive symptoms in older Korean adults: moderation analysis of muscular strength.

BACKGROUND: This population-based cross-sectional study examined the associations between physical activity (PA) and lower body muscle strength (LBMS) with late-life depression in a representative sample of older Korean adults aged 65 years and older. METHODS: The data used in the current study (n = 10,097/60% women) were extracted from the 2020 Korea Longitudinal Study on Aging, which is a nationwide population-based survey conducted in Korea. Depressive symptoms were assessed with the Geriatric Depression Scale Short-Form. PA and LBMS were evaluated with a self-reported questionnaire and the 5 times sit-to-stand test, respectively. Covariates include age, gender, body mass index, education level, smoking status, alcohol intake, and comorbidity. RESULTS: Insufficient PA had higher odds of depression (odds ratio [OR] = 1.201, 95% confidence interval [CI] = 1.035-1.393, p = 0.016), even after adjustments for all covariates, compared to sufficient PA. Poor LBMS had higher odds of depression (OR = 2.173, 95% CI = 1.821-2.593, p < 0.001), even after adjustments for all covariates, compared to good LBMS. Particularly, a significant moderation effect of LBMS on the relationship between PA and depressive symptoms was observed (ß = 0.3514 and 95% CI = 0.1294 ~ 0.5733, p < 0.001). Individuals with poor LBMS had a greater odd of depression associated with physical inactivity compared to their counterparts with good LBMS. CONCLUSIONS: The results of this study support the importance of promoting muscular strength through regular exercise as a preventive strategy against late-life depression in Korean adults.

Underweight children are agile but lack power.

Given the knowledge gap in literature on the impact of undernutrition on muscular power and agility in school-aged children, the aim of this study was to compare physical fitness in such underweight- and normal weight children. In this cross-sectional study, 853 children were included (459 boys; mean age: 9.2 (1.8) years). The children were grouped according to their BMI-for-age-and-sex: normal weight (- 1 ≤ z-score < 2) and underweight (z-score < - 1). Within the underweight group, three thinness subgroups were composed: grade 1 (- 2 ≤ z-score < - 1), grade 2 (- 3 ≤ z-score < - 2) and grade 3 (z-score < - 3). Their agility, muscular endurance and power were assessed with the Performance and Fitness test battery (PERF-FIT). Regardless the country they lived in, the underweight children showed better agility (p = 0.012) and muscular endurance (p = 0.004) than those with normal weight. They presented with lower muscular power than the normal weight group, shown by significantly shorter overhead throwing distances (p = 0.017) and less standing long jump peak power (p < 0.001). The standing long jump peak power decreased further with increasing thinness grade (p = 0.027).Conclusion: Underweight children are more agile, but have lower muscular power compared to their normal weight peers. Its relationship with motor competence and physical activity, necessitates attention for tackling muscular strength deficiencies in these children, enabling them to meet the basic requirements for a healthy lifestyle later in life.

Effects of aerobic exercise combined with resistance training on health-related physical fitness in adolescents: A randomized controlled trial.

Background: /Objective: This study aimed to compare the effects of two combined training methods on health-related physical fitness components in adolescents. Methods: Seventy-six adolescents (16.1 ± 1.1 years, n = 44 female) were randomized into groups of moderate-intensity continuous training combined with resistance training (MICT + RT), high-intensity interval training combined with resistance training (HIIT + RT), or Control. The training sessions were performed twice weekly for 12 weeks. The health-related physical fitness components evaluated were: body composition, muscular and cardiorespiratory fitness. Results: The intervention groups had a significant reduction in body fat percentage and improvement in abdominal repetitions and VO2peak after 12 weeks of combined exercise program (p < 0.001). Intervention effects were found to significantly reduce body fat percentage for the MICT + RT and HIIT + RT groups compared to the control group (mean difference: -3.8; 95% CI: -6.2; -1 0.3; mean difference: -4.7; 95%CI: -7.1; -2.3, respectively). For muscle fitness, significant effects of the intervention were found in increasing the number of abdominal repetitions favoring the MICT + RT group compared to the control group (mean difference: 9.5; 95% CI: 4.4; 14.7) and HIIT + RT compared to the control group (mean difference: 14.1; 95% CI 9; 19.3). For cardiorespiratory fitness, significant effects of the intervention on improving VO2peak were found in the experimental groups (MICT + RT vs Control group: mean difference: 4.4; 95% CI: 2.2; 6.6; and HIIT + RT vs. Control group: mean difference: 5.5, 95% CI: 3.3; 7.7). Conclusion: The results suggest that 12 weeks of training using MCIT + RT or HIIT + RT showed a similar effect for health-related physical fitness components in adolescents.

Cortical hemodynamics as a function of handgrip strength and cognitive performance: a cross-sectional fNIRS study in younger adults.

BACKGROUND: There is growing evidence for a positive correlation between measures of muscular strength and cognitive abilities. However, the neurophysiological correlates of this relationship are not well understood so far. The aim of this study was to investigate cortical hemodynamics [i.e., changes in concentrations of oxygenated (oxyHb) and deoxygenated hemoglobin (deoxyHb)] as a possible link between measures of muscular strength and cognitive performance. METHODS: In a cohort of younger adults (n = 39, 18-30 years), we assessed (i) handgrip strength by a handhold dynamometer, (ii) short-term working memory performance by using error rates and reaction times in the Sternberg task, and (iii) cortical hemodynamics of the prefrontal cortex (PFC) via functional near-infrared spectroscopy (fNIRS). RESULTS: We observed low to moderate negative correlations (rp = ~ - 0.38 to - 0.51; p < 0.05) between reaction time and levels of oxyHb in specific parts of the PFC. Furthermore, we noticed low to moderate positive correlations (rp = ~ 0.34 to 0.45; p < 0.05) between reaction times and levels of deoxyHb in distinct parts of the PFC. Additionally, higher levels of oxyHb (rp (35) = 0.401; p = 0.014) and lower levels of deoxyHb (rp (34) = - 0.338; p = 0.043) in specific parts of the PFC were linked to higher percentage of correct answers. We also found low to moderate correlations (p < 0.05) between measures of handgrip strength and levels of oxyHb (rp = ~ 0.35; p < 0.05) and levels of deoxyHb (rp = ~ - 0.25 to - 0.49; p < 0.05) in specific parts of the PFC. However, there was neither a correlation between cognitive performance and handgrip strength nor did cortical hemodynamics in the PFC mediate the relationship between handgrip strength and cognitive performance (p > 0.05). CONCLUSION: The present study provides evidence for a positive neurobehavioral relationship between cortical hemodynamics and cognitive performance. Our findings further imply that in younger adults higher levels of handgrip strength positively influence cortical hemodynamics although the latter did not necessarily culminate in better cognitive performance. Future research should examine whether the present findings can be generalized to other cohorts (e.g., older adults).

Evaluating the reach, effectiveness, adoption, implementation and maintenance of the Resistance Training for Teens program.

BACKGROUND: Physical activity guidelines recommend young people engage in regular muscle-strengthening activities (e.g., resistance training [RT]). However, few school-based physical activity interventions have been delivered at-scale or promoted RT. The aim of this study was to evaluate the reach, effectiveness, adoption, implementation and maintenance of the Resistance Training for Teens (RT for Teens) program. METHODS: Data were collected between August 2015 and October 2020. RE-AIM was operationalized as: (i) Reach: number and characteristics of students estimated to be exposed to the program; (ii) Effectiveness: impact of the program on student-level outcomes measured in a subsample of 750 students from 17 schools; (iii) Adoption: number and representativeness of schools with one or more teachers trained to deliver the program; (iv) Implementation: extent to which the program was delivered as intended; and (v) Maintenance: extent to which the program was sustained in schools. RESULTS: The estimated program reach was ~ 10,000 students, out of a total student population of ~ 200,000 (~ 5%). Students were from diverse socioeconomic and ethnic backgrounds. Improvements in muscular fitness, RT self-efficacy, perceived cardiorespiratory fitness and flexibility, and participation in muscle-strengthening physical activities were documented. A total of 30 workshops were delivered, involving 468 teachers from 249 schools from diverse geographical regions. Implementation varied considerably, with teachers adapting the program to suit the context of their school and student cohorts. However, RT skill development and the promotion of muscular fitness were the session components delivered most during sessions. Teachers' adherence to the SAAFE (Supportive, Active, Autonomous, Fair and Enjoyable) teaching principles was high. Approximately 30% of teachers (144/476) registered to use the RT for Teens app. At the school-level, 37% (93/249) of schools had at least one registered user (teacher and/or student). A total of 2,336 workouts and 3,116 fitness tests were completed by registered users. Of the 249 schools represented, 51 (20.5%) sent an additional (previously untrained) teacher to a second workshop. CONCLUSIONS: The RT for Teens program had broad reach and adoption. However, intervention delivery varied considerably across schools and additional support strategies are required to optimize intervention implementation and maintain program delivery over time. Future studies will benefit from the utilization of accepted frameworks, recommendations and guidelines for implementation research. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ACTRN12621000352808), retrospectively registered 1st February 2021.

Handgrip strength cut-off points for early detection of cardiometabolic risk in Chilean children.

The aim of this study was to determine whether handgrip strength is associated with cardiometabolic risk in children. The secondary aim was to establish sex-specific handgrip strength cut-off points for early detection of cardiometabolic risk. A total sample of 452 Chilean children (267 girls and 185 boys) aged 7-9 years old was analyzed. Muscle fitness was measured by an adjustable dynamometer and normalized by body mass (i.e., handgrip strength/body mass). Sex-specific cardiometabolic risk scores were computed as the sum of the waist-to-height ratio (Equation 1) or waist circumference (Equation 2) and insulin, triglycerides, high-density lipoproteins, and glycemia levels. Receiver operating curve (ROC) analyses were performed to identify those with cardiometabolic risk scores > 1 standard deviation above the mean. ROC analyses showed a significant discriminating accuracy of normalized handgrip strength in identifying cardiometabolic risk in boys (≤ 0.33) and girls (≤ 0.40) using both equations. The highest sensitivity was offered by Equation 2 for boys [46%; 95% CI (32-59%)] and for girls [71%; 95% CI (60-80)]. The greatest specificity was also offered by Equation 2 for boys [82%; 95% CI (74-88)] and girls [63%; 95% CI (55-70)]. Since the values obtained by ROC analyses are low (especially in boys), caution is warranted regarding the strength of the existing evidence base.Conclusion: These specific cut-off points according to sex for possible cardiometabolic risk could be used by Chilean health professionals and school staff as an initial assessment in the field setting. What is known • There is strong evidence for the importance of muscular fitness during childhood and adolescence for cardiometabolic risk. • There has been no research to establish minimum handgrip strength capacity levels to predict cardiometabolic risk among Chilean children. What is new • Cut-off points for handgrip strength relative to body mass to identify cardiometabolic risk in Chilean children are 0.33 in boys and 0.40 in girls. • The early use of these cut-off points and its appropriate identification could have benefits of preventive and diagnostic therapeutic intervention and as a starting point to define adequate levels of handgrip strength.

Child's body mass index and mother's obesity: the moderating role of physical fitness.

The aim of this study was to verify the association between children's body mass index and their mother's obesity, considering children's physical fitness as a possible moderator. Cross-sectional study developed with 1842 children and adolescents, aged seven to 17 years, from Santa Cruz do Sul-RS, Brazil. Body weight and height were assessed to determine body mass index. Cardiorespiratory fitness was determined by the 6-min walk/run test and muscular strength through the lower limb strength test. Mother's perception of obesity was self-assessed. Moderation was tested through a SPSS program extension. Results indicated that higher children's body mass index (p < 0.001) and lower levels of cardiorespiratory fitness (p = 0.001) and muscular strength (p = 0.035) were associated with mother's obesity. Likewise, higher body mass index (p < 0.001) and lower cardiorespiratory fitness (p < 0.001) in adolescents were associated with maternal obesity. Moreover, physical fitness moderates the relationship between body mass index and mother's obesity in children (cardiorespiratory fitness: ß = - 0.006; 95% CI = (- 0.010, - 0.001); muscular strength: ß = - 8.415; 95% CI = (- 12.526, - 4.304)) and in adolescents (cardiorespiratory fitness: ß = - 0.004; 95% CI = (- 0.008, - 0.0008); muscular strength: ß - 2.958; 95% CI = (- 5.615, - 0.030)).Conclusion: increasing physical fitness is an important strategy to protect youths from high body mass index, when their mothers are obese. What is Known: • Mother's obesity is associated with their children's body mass index. • Parents' obesity is associated with their children's physical fitness What is New: • Cardiorespiratory fitness and muscular strength are moderators in the relationship between mother's obesity and BMI of their children. • Children and adolescents with high cardiorespiratory fitness and muscular strength levels are protected against elevated body mass index, considering mother's obesity.

Physical fitness development in relation to changes in body composition and physical activity in adolescence.

The decline in adolescents' physical fitness (PF) in recent decades has raised concerns about current population's possible future challenges with health and physical functional capacity. This study explored the associations between body composition, physical activity, maturation, and PF development in adolescents. Furthermore, PF development of adolescents with low initial PF was assessed. A 2-year observational study was conducted between spring 2013 and 2015. Nine comprehensive schools and their 10- to 13-year-old students were invited to participate in the study (1778), and a total of 971 students (54.6%) agreed. Cardiorespiratory fitness (20-meter shuttle run), muscular fitness (push-ups), fundamental movement skills (5-leaps test), body composition (bioelectrical impedance analysis), moderate-to-vigorous physical activity (accelerometer), and pubertal status (self-assessment questionnaire) were measured at 1-year intervals. Latent growth curve modeling (LGM) was used to study PF development over time. Change in fat mass had the strongest and most coherent associations with PF development during adolescence. Fat-free mass, moderate-to-vigorous physical activity, and pubertal status were associated with PF development, although not systematically. Subgroup analyses showed that PF development in the low fitness group followed a similar pattern as the whole population. However, their PF remained significantly lower throughout the 2-year period. The findings suggest that fat accumulation is an essential detrimental factor for PF development during adolescence. Actions to prevent excessive fat accumulation might help to prevent future declines in functional capacity. Indications that low fitness levels sustain during adolescence highlight the relevance of detecting these individuals and providing interventions already before adolescence.

Predictive value of physical fitness on self-rated health: A longitudinal study.

BACKGROUND: The self-rated health of adolescents and young adults is important for estimating future morbidities and mortality. Little is known about how physical fitness in younger populations predicts self-rated health. This longitudinal study (2003-2017) aims to explore the effects of physical fitness on self-rated health on the basis of the German population-based study KiGGS and its in-depth study, MoMo. METHODS: Self-rated health was assessed using a one-item scale, and physical fitness was measured with seven test items covering the dimensions of coordination, muscular fitness, and cardiorespiratory fitness. Longitudinal analyses were conducted using the structural equation modeling approach in Mplus 8.0 using the maximum likelihood estimator. RESULTS: The longitudinal samples of the KiGGS/MoMo study (T1, n = 2376; T2, n = 2821; and T3, n = 2047) had a mean age of 8.5, 14.8, and 20.0 years at T1, T2, and T3, respectively. All measurement and structural models had excellent model fits. While the results of the latent regression analysis indicated moderate-to-high stability for the coordination and muscular fitness dimensions, only low-to-moderate stability coefficients were found for cardiorespiratory fitness and self-rated health. Furthermore, small significant cross-lagged regression coefficients revealed that coordination and muscular fitness predicted self-rated health at later measurement points. CONCLUSION: To the best of our knowledge, this is the first longitudinal study to demonstrate the positive predictive value of two dimensions of physical fitness, coordination and muscular fitness, on self-rated health at a later stage. The public health implications are highlighted.

A cross-sectional association of physical fitness with positive and negative affect in children and adolescents: the up & down study.

BACKGROUND: Affect and physical fitness play an important role in psychological and physical health; however, the association between those variables in youth remains unknown. The aim of the present study was to examine the influence of physical fitness on positive and negative affect in Spanish children and adolescents. METHOD: Healthy young Spanish people (n = 1,490) were recruited for the present study: 542 children (n = 272 girls; mean age 9.6 years) and 948 adolescents (n = 454 girls; mean age 14.1 years) with complete baseline data on health-related fitness tests (20 m shuttle run test, 4 × 10 m test, muscular fitness index, and physical fitness index), and positive and negative affect (Positive and Negative Affect Schedule). RESULTS: Higher performance on physical fitness components was associated with positive affect (ß = -0.176-0.118, all P < 0.05). There was no association between all physical fitness components and negative affect (ß = -0.100-0.15, all P > 0.05). There were differences on positive affect between the lowest and the highest quartile of the physical fitness index in boys (P = 0.037, Cohen's d 0.60) and girls (P = 0.004, Cohen's d = 0.69), and between the lowest and the highest quartile of muscular fitness index in girls (P < 0.001, Cohen's d = 0.76). CONCLUSIONS: Promoting physical activity during the school years, including strength exercises to increase muscular fitness, could improve positive affect levels and thus psychological health.