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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., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Physical activity trackers (PATs) such as apps and wearable devices (eg, sports watches, heart rate monitors) are increasingly being used by young adolescents. Despite the potential of PATs to help monitor and improve moderate-to-vigorous physical activity (MVPA) behaviors, there is a lack of research that confirms an association between PAT ownership or use and physical activity behaviors at the population level., Objective: The purpose of this study was to examine the ownership and use of PATs in youth and their associations with physical activity behaviors, including daily MVPA, sports club membership, and active travel, in 2 nationally representative samples of young adolescent males and females in Finland and Ireland., Methods: Comparable data were gathered in the 2018 Finnish School-aged Physical Activity (F-SPA 2018, n=3311) and the 2018 Irish Children's Sport Participation and Physical Activity (CSPPA 2018, n=4797) studies. A cluster analysis was performed to obtain the patterns of PAT ownership and usage by adolescents (age, 11-15 years). Four similar clusters were identified across Finnish and Irish adolescents: (1) no PATs, (2) PAT owners, (3) app users, and (4) wearable device users. Adjusted binary logistic regression analyses were used to evaluate how PAT clusters were associated with physical activity behaviors, including daily MVPA, membership of sports clubs, and active travel, after stratification by gender., Results: The proportion of app ownership among Finnish adolescents (2038/3311, 61.6%) was almost double that of their Irish counterparts (1738/4797, 36.2%). Despite these differences, the clustering patterns of PATs were similar between the 2 countries. App users were more likely to take part in daily MVPA (males, odds ratio [OR] 1.27, 95% CI 1.04-1.55; females, OR 1.49, 95% CI 1.20-1.85) and be members of sports clubs (males, OR 1.37, 95% CI 1.15-1.62; females, OR 1.25, 95% CI 1.07-1.50) compared to the no PATs cluster, after adjusting for country, age, family affluence, and disabilities. These associations, after the same adjustments, were even stronger for wearable device users to participate in daily MVPA (males, OR 1.83, 95% CI 1.49-2.23; females, OR 2.25, 95% CI 1.80-2.82) and be members of sports clubs (males, OR 1.88, 95% CI 1.55-2.88; females, OR 2.07, 95% CI 1.71-2.52). Significant associations were observed between male users of wearable devices and taking part in active travel behavior (OR 1.39, 95% CI 1.04-1.86)., Conclusions: Although Finnish adolescents report more ownership of PATs than Irish adolescents, the patterns of use and ownership remain similar among the cohorts. The findings of our study show that physical activity behaviors were positively associated with wearable device users and app users. These findings were similar between males and females. Given the cross-sectional nature of this data, the relationship between using apps or wearable devices and enhancing physical activity behaviors requires further investigation., (©Kwok Ng, Sami Kokko, Tuija Tammelin, Jouni Kallio, Sarahjane Belton, Wesley O'Brien, Marie Murphy, Cormac Powell, Catherine Woods. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 01.09.2020.)

Objectives: The objective of this study was to determine the gender-specific and time-segmented changes in accelerometer measured physical activity (PA) and sedentary time (ST) during adolescence., Methods: The study population (N = 970) consisted of children from nine schools throughout Finland. At the baseline, the children were in grades 4-7 (ages 10-13). Five times during the two-year follow-up period, hip-worn accelerometers (ActiGraph GT3X+) were deployed for seven consecutive days in order to monitor the pupils' PA. The daily time spent in vigorous (VPA), moderate to vigorous (MVPA), and light physical activity(LPA), as well as sedentary time(ST), were assessed., Results: Significant gender differences were observed in terms of the changes in MVPA and ST during the follow-up period. The total MVPA declined significantly in boys (by 2.2min/day/year from 60 min/d at baseline) but not in girls (49 min/d at baseline). The total ST increased both in boys (by 20.7%-points/y) and in girls (by 16.1%-points/y, P < .001). However, when we compared the results during the weekdays and weekend days separately, we observed that the declines in MVPA and increases in ST were greater in boys than in girls during the weekend days., Conclusion: A greater decrease in PA and a greater increase in ST during adolescence were observed among boys than among girls, especially during weekend days. In order to diminish these unfavorable behavioral changes during adolescence, we encourage the separate tailoring of interventions for boys and girls and for weekdays and weekends., (© 2020 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

Objectives: This study aimed to investigate cross-lagged associations of leaping skill and throwing-catching skills with objectively measured moderate-to-vigorous physical activity (MVPA) and sedentary time (ST) during school transition from upper primary (Grade 6) to lower secondary school (Grade 7)., Design: This study is a one-year prospective follow-up study within Finnish school settings. Students' MVPA, ST, leaping skill and throwing-catching skills were measured at Grade 6 and subsequently at Grade 7., Methods: A sample of 336 students (163 girls, 173 boys; M age=12.0 years, SD=0.4 at Grade 6 participated in the study. Students' MVPA and ST were measured objectively by hip-worn accelerometers. Leaping skill was measured by 5-leaps test. Throwing and catching skills were measured by throwing-catching combination test. Cross-lagged structural equation modeling was conducted to evaluate the associations between MVPA, ST, leaping skill, and throwing-catching skills at Grade 6 and Grade 7., Results: Results demonstrated three significant cross-lagged associations among girls: (1) leaping skill measured at Grade 6 was negatively associated with ST at Grade 7; (2) objectively measured MVPA at Grade 6 associated positively with leaping skill at Grade 7; and (3) throwing-catching skills measured at Grade 6 associated positively with leaping skill measured at Grade 7. There were no statistically significant cross-lagged associations between the study variables for the sample of boys., Conclusions: The results of this study indicated that supporting opportunities for girls' engagement in both MVPA and leaping skill development activities during their primary school education is strongly recommended., (Copyright © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

The aim of this study was to examine and quantify the cross-sectional associations of body composition (BC), physical activity (PA) and sedentary time (ST) with physical fitness (PF) in children and adolescents. A sample of 594 Finnish students (56% girls), aged 9-15 (12.4 ± 1.3 years) were selected for a study performed in 2013. The measurements of the Move! monitoring system for physical functional capacity were used to measure cardiorespiratory and musculoskeletal fitness and fundamental movement skills. Moderate-to-vigorous PA (MVPA) and ST were measured objectively with an accelerometer and BC by a bioelectrical impedance analysis. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated to represent height-adjusted BC. Associations were explored with a linear regression model. In general, FMI had statistically significant negative associations, while FFMI and MVPA had positive associations with PF. No statistically significant associations were observed between ST and PF. In general, FMI had the strongest association with PF, although some variation occurred with sex and PF component. However, associations were practically relevant only in 20-m shuttle run, push-up, curl-up and 5-leaps test. For example, approximately 5 kg increase in fat mass in 155 cm tall children was estimated to correspond to  8 laps in 20-m shuttle run. Similar increase in fat-free mass corresponded to +4 and +6 laps, and 10 min increase in daily MVPA +3 and +2 laps in 20-m shuttle run, in boys and girls, respectively. Understanding these associations is necessary when interpreting children's PF and designing interventions.

Background: This study investigated the associations of subjectively and objectively measured physical activity (PA) and sedentary behavior with academic achievement. We further examined whether aerobic fitness, obesity, and bedtime mediate these associations., Methods: This study included 970 children aged 9-15 years (52.3% girls) from 9 schools throughout Finland. Register-based academic achievement [grade point average (GPA)] as well as self-reported and accelerometer-measured PA/sedentary behavior were assessed during spring 2013. Aerobic fitness (assessed via a maximal shuttle run test), body composition (assessed via bioimpedance analysis), and self-reported bedtime were collected. Structural equation modeling was applied to examine the associations. Standardized regression coefficients are presented., Results: Self-reported PA had a direct positive [β = 0.084; 95% confidence interval (CI), 0.023 to 0.145] and an indirect positive association with GPA through higher aerobic fitness (β = 0.061; 95% CI, 0.033 to -0.087). Accelerometer-based PA was not associated with GPA. Self-reported screen time had an indirect negative association with GPA through later bedtime (β = -0.071; 95% CI, -0.096 to -0.035) and lower aerobic fitness (β = -0.039; 95% CI, -0.059 to 0.019). Nonscreen sedentary time had a direct positive (β = 0.193; 95% CI, 0.101 to -0.289) and an indirect negative association with GPA through lower aerobic fitness (β = -0.040; 95% CI, -0.063 to -0.016)., Conclusions: Participating in PA, avoiding excessive screen time, and going to bed earlier may benefit academic achievement.

Background: Finland's 2016 Report Card on Physical Activity for Children and Youth gathers and translates research results and assesses the status and promotion of physical activity (PA) among Finnish children and youth less than 18 years of age. This article summarizes the results and provides grades for 9 indicators., Methods: The working group evaluated the evidence and assigned grades of A (highest, 81% to 100%), B, C, D, or F (lowest, 0% to 20%) for 9 PA indicators using the Active Healthy Kids Canada Report Card development process., Results: The grades varied in Finland as follows: 1) Overall PA/fulfillment of recommendations = D, 2) Organized Sport Participation = C, 3) Active Play = C, 4) Active Transportation = B, 5) Sedentary Behaviors = D, 6) Family and Peers = C, 7) School = B, 8) Community and the Built Environment = B, 9) Government = B., Conclusions: Despite good policies and programs to promote PA in Finland, children and youth overall PA levels are low, whereas their time spent sedentary is high. More effective interventions, operation models, concrete tools as well as environmental solutions are needed to support the work toward more physically active childhood and youth.

Introduction/purpose: Recovery of force and stretch reflex from exhaustive stretch-shortening cycle (SSC) exercise is usually bimodal, characterized as immediate exercise-induced performance reduction, with its quick recovery followed by a longer-lasting reduction in performance. A clear parallel exists between the respective changes in performance, neural activation, and metabolic or structural exercise-induced changes. This implies the existence of potential coupling between muscle failure and the induced neural adjustments that take place along its recovery. The present study was designed to explore the evidence of this coupling more thoroughly., Methods: H- and stretch reflexes were measured before and periodically after exhaustive SSC exercise in human subjects. Several markers of muscle damage and inflammation were also measured during the 8-d postexercise follow-up period., Results: The results indicate that acute changes of H- and stretch reflex patterns and maximal isometric force are associated with significant increases in lactate, interleukin 6, and prostaglandin E2 concentrations. The delayed changes in reflexes and isometric force occurred concomitantly with increases in muscle thickness, C reactive protein, and substance P concentrations and also in serum creatine kinase activity., Conclusion: The immediate postexercise decreases in H- and stretch reflexes are probably partially caused by activation of group III and IV afferent fibers by high lactate concentration in combination with possible increases in potassium outflow. Both of these parameters recovered quickly (i.e., 2 h after exercise). The events after the 2-h postexercise point are very likely to be related to muscle damage and associated inflammation. Group III and IV afferent fibers are probably reactivated during this period by mechanical factors.

The leucine 7 to proline 7 (Leu7Pro) polymorphism in the signal peptide of NPY is associated with high blood lipid concentrations and accelerated rate of atherosclerosis as well as diabetic retinopathy. Also, healthy subjects with this polymorphism have increased NPY secretion during sympathetic stimulation. Because NPY may regulate GH release and ghrelin may regulate NPY formation, we studied the effects of the Leu7/Pro7 genotype on GH, ghrelin, and IGF-I secretion during standardized cycle-ergometer exercise. Furthermore, we studied the effect of the Leu7/Pro7 genotype on diurnal GH secretion in rest in a separate study. The subjects with Leu7/Pro7 genotype had 54% higher maximal increases in the plasma GH concentrations than the controls during exercise. There were no significant differences in the ghrelin or IGF-I concentrations during exercise among the groups. Furthermore, there were no differences in diurnal GH secretion between the genotypes. The results indicate that the prepro-NPY genotype has an influence on GH response during exercise in humans. The clinical significance of this finding is not known, and further studies are needed to evaluate whether the observed change in GH secretion during exercise could play a role in promoting diseases.

This study focused on the architectural changes in the muscle-tendon complex during the immediate and secondary (delayed) reductions of performance (bimodal recovery) caused by an exhaustive rebound type stretch-shortening cycle (SSC) exercise. The isometric plantar flexor torque during maximum voluntary contraction (MVC) was measured together with recording of electromyography (EMG) and ultrasonography from the soleus muscle before (BEF), after (AFT), 2 h (2H), 2 and 8 days (2D, 8D) after the SSC exercise (n=8). The performance variables (MVC torque and EMG activation) followed the bimodal recovery patterns. This was not the case in the changes of the fascicle length and muscle thickness. The relative torque changes in MVC correlated positively (R=0.78, P=0.02) to the corresponding averaged EMG changes between BEF and 2H (BEF-->2H); the significance disappeared in the comparison between 2H and 2D (2H-->2D), during which period MVC showed a secondary reduction. The relative torque changes in MVC showed no correlation with the changes in muscle thickness between BEF-2H. However, this correlation between 2H-2D was negative (R=-0.85, P<0.01). The fascicle shortening/average EMG ratio in MVC increased at 2H, and then decreased more at 2D than 2H (P<0.05). Thus, the secondary performance decline was not related to the corresponding EMG reduction but to the increased muscle thickness, which peaked at 2D. The results suggest clearly that the secondary decline in MVC could be related to the increase in muscle volume. [ABSTRACT FROM AUTHOR]