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Purpose: To assess the training load, energy expenditure, dietary intake, and sleep quality and quantity of junior tennis players during a tennis training camp. Methods: Ten junior academy tennis players (14 [1] y) completed a 6-day camp with daily morning and afternoon training. Players wore accelerometer watches to measure activity energy expenditure and sleep. Global positioning system units were worn to monitor external training load (distance covered, maximum velocity, and PlayerLoad^™). Dietary intake was obtained from a food diary and supplementary food photography. Results: Players covered significantly more distance and had higher PlayerLoad^™ during morning sessions than afternoon sessions (5370 [505] m vs 4726 [697] m, P < .005, d = 3.2; 725 [109] a.u. vs 588 [96] a.u., P < .005, d = 4.0). Players also ran further (5624 [897] m vs 4933 [343] m, P < .05, d = 1.0) and reached higher maximum velocities (5.17 [0.44] m·s⁻¹ vs 4.94 [0.39] m·s⁻¹, P < .05, d = 0.3) during simulated match play compared with drill sessions. Mean daily energy expenditure was 3959 (630) kcal. Mean energy intake was 2526 (183) kcal, resulting in mean energy deficits of 1433 (683) kcal. Players obtained an average of 6.9 (0.8) hours of sleep and recorded 28 (7) nightly awakenings. Conclusions: Junior academy tennis players failed to achieve energy balance and recorded suboptimal sleep quantity and quality throughout the training camp.

Purpose: The purpose of this study was to examine the psychological responses to intermittent activities of varying intensities and types among children with and without asthma. Methods: A total of 37 children and adolescents (51% male, aged 8–16 y, 54% nonwhite, and 54% without asthma) participated in this study. Participants completed 5 exercises in the same order: self-paced walking, resistance activities, dance video, gamified obstacle course, and step test. In-task mood was assessed using the Feeling Scale, in-task perceived exertion was assessed via the ratings of perceived exertion scale, and postactivity enjoyment was assessed using the Physical Activity Enjoyment Scale. Results: There was a significant main effect of exercise type on mood (P < .001), ratings of perceived exertion (P < .001), and enjoyment (P < .002). There was not a significant main effect of asthma status on mood, ratings of perceived exertion, or enjoyment (Ps > .05). Children with asthma reported significantly lower in-task mood during the step exercise (P < .037) and reported significantly lower postactivity enjoyment after the walk and obstacle course exercises (Ps < .03). Conclusions: Regardless of differences by asthma status for in-task mood during the obstacle course and for postactivity enjoyment during the walk and step exercises, both children with and without asthma reported high in-task mood and postactivity enjoyment during all 5 exercises.

Objective: To compare the acute perceptive responses of different combined training methods in adolescents. Materials and Methods: The sample consisted of 50 adolescents, insufficiently active, aged between 14 and 18 years (58% female). The adolescents performed 2 sessions in a randomized order: moderate-intensity continuous training + resistance training (MICT + RT) and high-intensity interval training + resistance training (HIIT + RT). The rating of perceived exertion, affect, and satisfaction were measured by self-report in 5 moments during the combined training (HIIT or MICT—moments 1, 2, and 3; RT—moments 4 and 5) and 10 minutes after the end of the session. Results: During HIIT, adolescents reported higher values of rating of perceived exertion compared to the MICT session at moments 2 and 3 in both sexes (P < .05). In addition, at moments 2 and 3 of the HIIT session, female participants were reported to have a higher value of satisfaction compared to MICT (F = 3.953; P = .005; η ² = .067). Conclusion: During the execution of both HIIT + RT and MICT + RT protocols, adolescents showed an increase in the values of pleasure and satisfaction, regardless of sex.

Physical activities involving impact loading are important for improving bone strength and mineral density in children. There is little research quantifying impact loads associated with various high-impact activities. Purpose: Examine the magnitude of peak ground reaction forces (pGRF) across different jumping activities in children. Methods: Eight children between 8 and 12 years (9.63 [1.49] y; 1.42 [0.08] m; 33.69 [4.81] kg), performed 5 trials of a broad jump, countermovement jump, jumping jack, leap jump, and drop jump on a force plate. The pGRF were determined during the landing phase of each activity and expressed in units of body weight (BW). A repeated-measures analysis of variance was employed to assess differences in pGRF across activities. Results: Drop jump exhibited the greatest pGRF (3.09 [0.46] BW) in comparison with the vertical jumping jack (2.56 [0.21] BW; P < .001) and countermovement jump (2.45 [0.22] BW; P = .001), as well as the horizontal broad jump (2.25 [0.2] BW; P = .003), and leap jump (2.01 [0.1] BW; P = .002). Conclusion: Peak loads between 2 and 3.1 BW were exhibited across each jump activity, which is moderate compared with magnitudes in most jump interventions seeking to improve bone health. All conditions except drop jump exhibited loading <3 BW, suggesting these activities may not produce sufficient loads to improve bone outcomes.

Purpose: To identify the smallest change in handgrip strength (HGS) in children that can be considered of practical significance. Method: A total of 290 male and female children, aged 6–13 years, performed a HGS testing protocol 3 times within a 7-day period. The typical error of measurement (TE), coefficient of variation, and smallest worthwhile change (SWC) were calculated for each sex and age group (grade). Results: The TE for the combined group of grade 1 to 7 children was 1.3 kg. Changes in HGS associated with a small change were 1.3 kg, making it difficult for the HGS test to detect these changes. The TE was less than the medium (3.3 kg) and large (5.3 kg) changes in HGS for all the grades and sexes, making changes of these magnitudes more interpretable as they exceed the “noise” (TE) of the measurement. Conclusion: Changes in HGS greater than the TE and SWC can be considered real changes of practical significance. This provides researchers with an extra level of analysis when trying to determine the practical relevance of the observed changes.

Purpose: The authors examined associations between preschoolers’ daily glycemic variability, parents’ report of hypoglycemia fear, and preschoolers’ daily moderate to vigorous physical activity (MVPA) and sedentary behavior (SB) in 25 families of preschoolers with type 1 diabetes. Methods: Parents completed a valid measure of hypoglycemia fear, and their child wore an accelerometer for up to 7 days. Parents provided glucose data from their child’s devices. The authors used multiple regression and multilevel modeling to analyze their data. Results: Preschoolers (mean age 4.2 [1.7] y; 50% boys) engaged in a mean of 154.5 (59.6) and 339.2 (85.1) minutes of MVPA and SB per day, respectively, and parents reported relatively low levels of hypoglycemia worry and avoidance behaviors. Preschoolers’ SB (r = .19, P = .02) and MVPA (r = −.20, P = .01) levels were significantly correlated with parental hypoglycemia worry scores but not with parents’ hypoglycemia behavior scores (P = .15 and P = .92, respectively). While multilevel models did not show an association between MVPA and preschoolers’ glycemic variability, preschoolers who engaged in more daily SB experienced higher glycemic variability (P = .04). Conclusions: Research exploring MVPA, SB, and parental hypoglycemia fear in preschoolers with type 1 diabetes could have important clinical implications because it may reveal modifiable treatment targets that can impact preschoolers’ health and activity patterns.

Purpose: To assess the short-term reliability of measurement instruments to quantify the acute psychophysiological response to load in adolescent soccer players in relation to biological maturity. Methods : Data were collected from 108 U12 to U17 soccer players on 2 consecutive weeks (pre, n = 32; at, n = 34; and post, n = 42 estimated peak height velocity). Measurements consisted of the Short Recovery and Stress Scale, a countermovement jump, assessment of leg stiffness, and a submaximal run to assess exercise heart rate and heart rate recovery. Test–retest reliability was assessed with the coefficient of variation (CV) and intraclass correlation coefficient (ICC). Results : Items of the Short Recovery and Stress Scale showed poor reliability across maturity groups (CV = 7.0%–53.5%; ICC = .28 to .79). Only few countermovement jump variables (jump height, concentric impulse, and concentric velocity) possessed good reliability. For most variables of the countermovement jump, reliability was better for the post peak height velocity group followed by at-peak height velocity and prepeak height velocity. Very high levels of reliability across maturity groups were observed for exercise heart rate (CV < 1.8%; ICC > .94), while heart rate recovery was more variable (CV < 16.5%; ICC > .48). Conclusion : Results suggest that the majority of investigated variables have poor reliability, questioning their ability to detect small, yet meaningful changes in acute responses to load in adolescent soccer players.

Purpose: The aim of this study was 2-fold: (1) to assess and compare the external and internal load of elite young soccer players during competitive microcycles and (2) to describe the training/match ratios (TMr) in elite male youth soccer players. Method: Twenty-one youth soccer players were monitored using a 10-Hz global positioning system. Total distance covered, running distance (RD), high-speed RD, sprint distance, number of accelerations and decelerations, player load, and rated perceived exertion were recorded during training sessions and matches. The TMr was calculated for each load measure. All variables were also normalized dividing the load per minute of activity. Results: The RD, high-speed running, and sprint distance were higher 3 days before the match and 2 days before match compared with the rest of the training sessions. However, accelerations, decelerations, and player load were higher 4 days before match than other sessions. Besides this, the TMr of RD, high-speed running, and sprint distance were associated with lower values than the TMr of total distance covered, accelerations, decelerations, and player load. The match constituted the highest load during competitive microcycle. Conclusions: The present data support the idea that youth soccer coaches and practitioners must consider relative training load according to match demands to better manage and evaluate player periodization.