Timing and pattern of postexercise protein ingestion affects whole-body protein balance in healthy children: a randomized trial.

The dose and timing of postexercise protein ingestion can influence whole-body protein balance (WBPB) in adults, although comparable data from children are scarce. This study investigated how protein intake (both amount and distribution) postexercise can affect WBPB in physically active children. Thirty-five children (26 males; 9-13 years old) underwent a 5-day adaptation diet, maintaining a protein intake of 0.95 g·kg-1·day-1. Participants consumed [15N]glycine (2 mg·kg-1) before performing 3 × 20 min of variable-intensity cycling, and whole-body protein kinetics were assessed over 6 and 24 h of recovery. Fifteen grams of protein was distributed across 2 isoenergetic carbohydrate-containing beverages (15 and 240 min postexercise) containing reciprocal amounts of protein (i.e., 0 + 15 g, 5 + 10 g, 10 + 5 g, and 15 + 0 g for Groups A-D, respectively). Over the 6 h that included the exercise bout and consumption of the first beverage at 15 min postexercise, WBPB (i.e., synthesis - breakdown) demonstrated a linear increase of 0.647 g·kg-1·day-1 per 1 g protein intake (P < 0.001). Over 24 h, robust regression revealed that WBPB was best modeled by a parabola (P < 0.05), suggesting that a maximum in WBPB was achieved between groups B and C. In conclusion, despite a dose response early in recovery, a periodized protein intake with multiple smaller doses after physical activity may be more beneficial than a single bolus dose in promoting daily WBPB in healthy active children.

Postexercise Dietary Protein Ingestion Increases Whole-Body Leucine Balance in a Dose-Dependent Manner in Healthy Children.

Background: Protein ingestion is important in enhancing whole-body protein balance in children. The effect of discrete bolus protein ingestion on acute postexercise recovery has yet to be determined.Objective: This study determined the effect of increasing doses of ingested protein on postexercise whole-body leucine balance in healthy, active children.Methods: Thirty-five children (26 boys, 9 girls; age range: 9-13 y; weight mean ± SD: 44.9 ± 10.6 kg) underwent a 5-d adaptation diet (0.95 g protein ⋅ kg-1 ⋅ d-1) before performing 20 min of cycling 3 times with a concurrent, primed, constant infusion of [13C]leucine. After exercise, participants consumed an isoenergetic beverage (140 kcal) containing variable amounts of bovine skim-milk protein and carbohydrates (sucrose) (0, 5, 10, and 15 g protein made up with 35, 30, 25, and 20 g carbohydrates, respectively). Blood and breath samples were taken over the 3 h of recovery to determine non-steady state whole-body leucine oxidation (LeuOX) and net leucine balance (LeuBAL).Results: LeuOX (secondary outcome) peaked 60 min after beverage ingestion and demonstrated a relative dose-response over the 3 h of recovery (15 g = 10 > 5 > 0 g; P < 0.001). LeuBAL (primary outcome) demonstrated a dose-response over the 3 h [15 g (24.2 ± 8.2 mg/kg) > 10 g (11.6 ± 4.3 mg/kg) > 5 g (5.7 ± 1.9 mg/kg) > 0 g (-3.0 ± 1.7 mg/kg); all P < 0.01] with all conditions different from zero (all P < 0.001).Conclusions: Over the 3-h postexercise period, LeuBAL was negative with carbohydrate ingestion alone; however, the co-ingestion of carbohydrates and 5 g high-quality dietary protein was sufficient to promote a positive postexercise whole-body protein balance in healthy, active children. Moreover, LeuBAL increased in a dose-dependent manner within the protein range studied. Children should consider consuming a source of dietary protein after physical activity to enhance whole-body anabolism. This trial was registered at clinicaltrials.gov as NCT01598935.

Exertion Testing in Youth with Mild Traumatic Brain Injury/Concussion.

PURPOSE: The decision regarding return to activity (RTA) after mild traumatic brain injuries/concussion is one of the most difficult and controversial areas in concussion management, particularly for youth. This study investigated how youth with postconcussion syndrome (PCS) are affected by exertion and whether standardized exertion testing using the McMaster All-Out Progressive Continuous Cycling Test can contribute to clinical decision making for safe RTA. METHODS: Fifty-four youth (8.5-18.3 yr) with a previously confirmed concussion participated in the study. Each participant performed exertion testing on a cycle ergometer and completed a Postconcussion Symptom scale at the following time points: before exertion (baseline), 5 and 30 min, and 24 h after exertion. A modified Postconcussion Symptom scale was administered at 2-min intervals during exertion. RESULTS: Participants had a mean ± SD symptom duration of 6.3 ± 6.9 months after the most recent concussive injury, with a median of 4.1 months (range, 0.7-35 months). Sixty-three percent of participants had symptoms during exertion testing. Symptom profile (number and severity) significantly affected perception of exertion at 50% peak mechanical power. During acute assessment of symptoms (30-min after exertion), headache (P = 0.39), nausea (P = 0.63), and dizziness (P = 0.35) did not change. However, both the number and severity of symptoms significantly improved over 24 h, with 56.8% of youth showing improvements. The time from the most recent injury had a significant effect on the symptom score at baseline, 30 min after exertion, and 24 h after exertion. CONCLUSIONS: Exertion testing has an important role in the evaluation of symptoms and readiness to RTA, particularly in youth who are slow to recover. Overall, controlled exertion seemed to lesson symptoms for most youth.

Effects of acute exercise on markers of inflammation in pediatric chronic kidney disease: a pilot study.

BACKGROUND: Children and adolescents with chronic kidney disease (CKD) are chronically exposed to high levels of inflammation, placing them at an increased risk of secondary health complications. Regular exercise may represent an effective therapy to reduce inflammation. The aims of this pilot study were to determine the effects of acute exercise on inflammation and immune cell counts in CKD. METHODS: Nine children and adolescents (4 males) with CKD stages III-V performed a graded exercise test to determine peak oxygen uptake (VO2peak). Following a 10-min break, participants cycled for 20 min at 50 % of VO2peak. Blood samples were collected before and after the exercise period for the determination of complete blood counts, natural killer cells (NK(bright), NK(dim)) and circulating progenitor cell (CPC) counts, as well as interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) concentrations. RESULTS: Complete blood counts and NK(dim) cell and CPC counts were unchanged with exercise. Following exercise, NK(bright) cell counts increased (7.4 ± 4.3 vs. 12.2 ± 8.3 × 10(6) cells/L; p = 0.02), while trends were observed for an increase in IL-6 (2.1 ± 2.2 vs. 2.7 ± 2.6 pg/mL; p = 0.08), decrease in TNF-α (4.5 ± 1.2 vs. 4.2 ± 1.0 pg/mL; p = 0.08) and an increase in the IL-6:TNF-α ratio (0.6 ± 0.7 vs. 0.8 ± 0.8; p = 0.07). CONCLUSIONS: Our findings suggest that acute exercise may create an anti-inflammatory environment in children and adolescents with CKD stages III-V.

Do obese children perceive submaximal and maximal exertion differently?

We examined how obese children perceive a maximal cardiorespiratory fitness test compared with a submaximal cardiorespiratory fitness test. Twenty-one obese children (body mass index ≥95th percentile, ages 10-17 years) completed maximal and submaximal cardiorespiratory fitness tests on 2 separate occasions. Oxygen consumption (VO2) and overall perceived exertion (Borg 15-category scale) were measured in both fitness tests. At comparable workloads, perceived exertion was rated significantly higher (P < 0.001) in the submaximal cardiorespiratory fitness test compared with the maximal cardiorespiratory fitness test. The submaximal cardiorespiratory fitness test was significantly longer than the maximal test (14:21 ± 04:04 seconds vs. 12:48 ± 03:27 seconds, P < 0.001). Our data indicate that at the same relative intensity, obese children report comparable or even higher perceived exertion during submaximal fitness testing than during maximal fitness testing. Perceived exertion in a sample of children and youth with obesity may be influenced by test duration and protocol design.

Using the oxygen uptake efficiency slope as an indicator of cardiorespiratory fitness in the obese pediatric population.

The aim of the current study was to investigate the relationship between the Oxygen Uptake Efficiency Slope (OUES) and traditional measures of cardiorespiratory function in an overweight/obese pediatric sample. Maximal treadmill exercise testing with indirect calorimetry was completed on 56 obese children aged 7-18 years. Maximal OUES, submaximal OUES, VO(2peak), VE(peak), and ventilatory threshold (VT) were determined. In line with comparable research in healthy-weight samples, maximal and submaximal OUES were both correlated with VO(2peak), VE(peak), and VT (r(2)= 0.44-0.91) in the obese pediatric sample. Correlations were also found with anthropometric variables, including height (cm), body surface area (m(2)), body mass (kg), and fat free mass (kg). In comparing our data to a published sample of healthy weight children, maximal and submaximal exercise OUES were both higher in our obese sample. However, when we adjusted for any of body mass (kg), BSA (m(2)), or FFM (kg) the obese children were found to be less efficient. The results of this study suggest the use of OUES to be an appropriate measure of efficiency of ventilation and cardiorespiratory function in obese children, while also showing that our sample of obese children were less efficient on a per kilogram basis when compared with their healthy weight peers.

The HALO submaximal treadmill protocol to measure cardiorespiratory fitness in obese children and youth: a proof of principle study.

Many limitations exist with completing cardiorespiratory fitness testing in obese children. The aim of this study was to determine if the new Healthy Active Living and Obesity Research Group's (HALO's) submaximal cardiorespiratory fitness testing protocol for obese children and youth provides a comparable estimate of peak oxygen uptake to that measured using validated maximal and submaximal, equation-based protocols in the obese pediatric population. A group of obese children (n = 21; all ≥95th body mass index percentile; aged 10-17 years) completed 3 exercise testing protocols. Testing was completed as part of an ongoing cohort study and 2 submaximal cardiorespiratory fitness tests were completed, in randomized order, during a second visit. Significant correlations were found between observed peak oxygen uptake (mL·min(-1)) and predicted peak oxygen uptake for both the HALO (r = 0.75, p = 0.001) and Nemeth (r = 0.66, p = 0.001) submaximal protocols. A similar correlation was found, after accounting for body mass, between measured and predicted HALO peak oxygen uptake (mL·kg(-1)·min(-1)) values (r = 0.54, p = 0.01). HALO predicted peak oxygen uptake values showed a significant correlation when plotted against the measured values (r = 0.99). A Bland-Altman analysis found agreement between the maximal and HALO submaximal protocols (mean bias = -201.75 mL·min(-1)). The significant relationships found between estimates of peak oxygen uptake from the HALO submaximal protocol and measures of peak oxygen uptake during maximal cardiorespiratory testing support the use of the HALO submaximal protocol as a valid measure to estimate maximal cardiorespiratory fitness within the obese pediatric population. Given the proof of principle goal of this study, future research in the obese, pediatric population is encouraged to confirm the generalizability of the protocol.