PURPOSE: To compare the age and sex differences in the kinetic response of muscle PCr during high-intensity exercise in children and adults. METHODS: Eleven adults (6 men 25 ± 5 y and 5 women 23 ± 3 y) and 11 children (6 boys 13 ± 0.2 y and 5 girls 13 ±1.3 y) exercised using their right leg on a quadriceps ergometer within a 1.5 Tesla MR scanner. Following habituation, each participant completed an incremental test to exhaustion. After a minimum 48 hours recovery, participants completed two to four constant work rate bouts on separate days. Exercise bouts consisted of 2 min rest and 7 min exercise, at an intensity equivalent to 20% of the difference between the workload at the intracellular Pi/PCr threshold and the maximal workload. 31P spectra were collected every 6 s using a 6 cm surface coil positioned beneath the right quadriceps muscle. The breakdown of muscle PCr at the onset of exercise was modelled using a single-exponential function until the onset of the PCr slow component (SC). This point was identified using an iterative fitting window - where the time constant diverged from a plateau, a PCr SC was deemed to emerge. Data are reported as mean ± standard deviation and 95% confidence intervals (CI) are presented. A two by two factorial ANOVA was utilised to determine group differences. RESULTS: No significant interaction effect was found for the fundamental time constant (boys: 31 ± 10, CI 5; girls: 31 ± 10, CI 6; men: 44 ± 20, CI 6; women: 29 ± 14 s, CI 6 s; P=0.26), or the fundamental amplitude (boys: -39 ± 10; girls: -42 ± 9; men: -36 ± 9; women: -48 ± 9%; P=0.23), or the SC PCr (as a % of the difference between the fundamental amplitude and end exercise PCr) which was similar across groups (boys: 6 ± 1; girls: 13 ± 8; men: 8 ± 5; women: 8 ± 6% P=0.15). The end-exercise PCr revealed a significant sex difference (P=0.03) but no significant age or interaction effect (boys: 55 ± 10; girls: 46 ± 14; men: 56 ± 11; women: 44 ± 8%). There was no significant difference between age (P=0.22) or sex (P=0.13) for the PCr cost of contraction at end-exercise (boys: 1.7 ± 0.5; girls: 1.3 ± 0.5; men: 1.4 ± 0.4; women: 1.2 ± 0.2 mM·W-1P=0.13). CONCLUSION: The kinetics of muscle PCr during high intensity exercise are similar in 13 y old children and adults, suggesting the phosphate-linked control of oxidative metabolism, at least during high-intensity exercise, is adult like by this age.
Background: Distance running is one of the most popular sports around the world. The epidemiology of running-related injury (RRI) has been investigated in adults, but few studies have focused on adolescent distance runners. Objectives: (1) To provide descriptive epidemiology of RRI (risks, rates, body regions/areas, and severity) and examine the training practices (frequency, volume, and intensity) of competitive adolescent distance runners (13–18 years) in England, and (2) to describe potential risk factors of RRI. Methods: A cross-sectional study design was used. Adolescent distance runners ( n = 113) were recruited from England Athletics affiliated clubs. Participants voluntarily completed an online questionnaire between April and December 2018. At the time of completion, responses were based on the participant's previous 12-months of distance running participation. Incidence proportions (IP) and incidence rates (IR) were calculated. Results: The IP for “all RRI” was 68% (95% CI: 60–77), while the IR was 6.3/1,000 participation hours (95% CI: 5.3–7.4). The most commonly injured body areas were the knee, foot/toes, and lower leg; primarily caused by overuse. The number of training sessions per week (i.e., frequency) significantly increased with chronological age, while a large proportion of participants (58%) self-reported a high level of specialisation. Conclusions: RRI is common in competitive adolescent distance runners. These descriptive data provide guidance for the development of RRI prevention measures. However, analytical epidemiology is required to provide better insight into potential RRI risk factors in this specific population.
Purpose: This study had 2 objectives: (1) to examine whether the validity of the supramaximal verification test for maximal oxygen uptake ( V˙O2max ) differs in children and adolescents when stratified for sex, body mass, and cardiorespiratory fitness and (2) to assess sensitivity and specificity of primary and secondary objective criteria from the incremental test to verify V˙O2max . Methods: In total, 128 children and adolescents (76 male and 52 females; age: 9.3-17.4 y) performed a ramp-incremental test to exhaustion on a cycle ergometer followed by a supramaximal test to verify V˙O2max . Results: Supramaximal tests verified V˙O2max in 88% of participants. Group incremental test peak V˙O2 was greater than the supramaximal test (2.27 [0.65] L·min-1 and 2.17 [0.63] L·min-1; P < .001), although both were correlated (r = .94; P < .001). No differences were found in V˙O2 plateau attainment or supramaximal test verification between sex, body mass, or cardiorespiratory fitness groups (all Ps > .18). Supramaximal test time to exhaustion predicted supramaximal test V˙O2max verification (P = .04). Primary and secondary objective criteria had insufficient sensitivity (7.1%-24.1%) and specificity (50%-100%) to verify V˙O2max . Conclusion: The utility of supramaximal testing to verify V˙O2max is not affected by sex, body mass, or cardiorespiratory fitness status. Supramaximal testing should replace secondary objective criteria to verify V˙O2max .
Abstract Background Regular participation in physical activity by people with cystic fibrosis (CF) promotes positive clinical and health outcomes including reduced rate of decline in lung function, fewer hospitalizations and greater wellbeing. However adherence to exercise and activity programs is low, in part due to the substantial daily therapy burden for young people with CF. Strict infection control requirements limit the role of group exercise programs that are commonly used in other clinical groups. Investigation of methods to promote physical activity in this group has been limited. The Active Online Physical Activity in Cystic fibrosis Trial (ActionPACT) is an assessor-blinded, multi-centre, randomized controlled trial designed to compare the efficacy of a novel web-based program (ActivOnline) compared to usual care in promoting physical activity participation in adolescents and young adults with CF. Methods Adolescents and young adults with CF will be recruited on discharge from hospital for a respiratory exacerbation. Participants randomized to the intervention group will have access to a web-based physical activity platform for the 12-week intervention period. ActivOnline allows users to track their physical activity, set goals, and self-monitor progress. All participants in both groups will be provided with standardised information regarding general physical activity recommendations for adolescents and young adults. Outcomes will be assessed by a blinded assessor at baseline, after completion of the intervention, and at 3-months followup. Healthcare utilization will be assessed at 12 months from intervention completion. The primary outcome is change in moderate-to-vigorous physical activity participation measured objectively by accelerometry. Secondary outcomes include aerobic fitness, health-related quality of life, anxiety and depression and sleep quality. Discussion This trial will establish whether a web-based application can improve physical activity participation more effectively than usual care in the period following hospitalization for a respiratory exacerbation. The web-based application under investigation can be made readily and widely available to all individuals with CF, to support physical activity and exercise participation at a time and location of the user’s choosing, regardless of microbiological status. Trial registration Clinical trial registered on July 13, 2017 with the Australian and New Zealand Clinical Trials Register at ( ACTRN12617001009303 ).
PURPOSE: To compare the kinetic response of PCr and deoxyhemoglobin (HHb) during high-intensity exercise in boys and men. METHODS: Seven men (25 ± 5 y) and six boys (13 ± 1 y) exercised using the right leg on a quadriceps ergometer within a 1.5 T MR scanner. Following habituation sessions each participant completed an incremental test to exhaustion. After a minimum 48 hours recovery, participants completed two to four constant work rate bouts on separate days. Exercise bouts consisted of 2 min rest and 7 min exercise, at an intensity equivalent to 20% of the difference between the workload at the intracellular Pi/PCr threshold and the maximal workload. Changes in HHb were determined every 1 s using a NIRS probe which was secured over the vastus lateralis muscle. 31P spectra were collected every 6 s using a 6 cm surface coil positioned beneath the right quadriceps muscle. The breakdown of PCr at the onset of exercise was modelled using a single-exponential function until the onset of the PCr slow component (SC). This point was identified using an iterative fitting window - where the time constant diverged from a plateau, a PCr SC was deemed to emerge. HHb profiles for participants were modelled as above, although a delay term was included in the model to account for the transient decrease in HHb at the onset of exercise. Data are reported as mean ± standard deviation and 95 % confidence intervals (CI) are presented. PCr and HHb data from two boys and HHb data from one adult were excluded from the analysis. RESULTS: The fundamental time constant (boys: 31 ± 11 s, CI 5 s; men: 45 ± 19 s, CI 6 s; P = 0.23), fundamental amplitude (boys: 43 ± 10%; men: 36 ± 8%, P = 0.24), and the SC amplitude (boys: 6 ± 1%; men: 12 ± 12%, P = 0.33) for PCr were similar in both groups. The net change in PCr was similar (men: 52 ± 16%; boys: 51 ± 9%, P = 0.93), as was the time constant for HHb increase in boys and men (19 ± 2 s and 22 ± 2 s, P = 0.55) respectively, with a delay of 5 ± 2 s. Responses over the last three minutes of exercise for HHB showed considerable inter-individual variation. CONCLUSIONS: Results from this study showed no differences in the breakdown of PCr or in the balance between the delivery and utilisation of O2 at the onset of highintensity exercise between boys and men. However, a trend of an age-related slowing of the breakdown of PCr at the onset of exercise warrants further investigation.
This study aimed to document the matching of muscle O2 delivery to O2 use in young patients with cystic fibrosis (CF) from muscle deoxygenation (HHb) dynamics during ramp exercise.Ten patients with stable, mild-to-moderate CF (12.7 ± 2.8 yr) and 10 healthy controls (CON, 12.8 ± 2.8 yr) completed a combined ramp and supramaximal cycling test to determine maximal O2 uptake (V˙O2max). Changes in gas exchange and ventilation, HR, and m. vastus lateralis HHb (near-infrared spectroscopy) were assessed. Δ[HHb]-work rate and Δ[HHb]-V˙O2 profiles were normalized and fit using a sigmoid function.Aerobic function was impaired in CF, indicated by very likely reduced fat-free mass-normalized V˙O2max (mean difference, ±90% confidence interval: -7.9 mL·kg·min, ±6.1), very likely lower V˙O2 gain (-1.44 mL·min·W, ±1.12), and a likely slower V˙O2 mean response time (11 s, ±13). An unclear effect was found upon the absolute and relative work rate (-14 W, ±44, and -0.7% peak power output, ±12.0, respectively) and the absolute and percentage (-0.10 L·min, ±0.43, and 3.3% V˙O2max, ±6.0) V˙O2 corresponding to 50% Δ[HHb] amplitude, respectively, between groups. However, arterial oxygen saturation (SpO2) was very likely lower in CF (-1%, ±1) and demonstrated moderate-to-very large relations with parameters of aerobic function.Young patients with mild-to-moderate CF present with impaired aerobic function during ramp incremental cycling exercise. Because the rate of fractional O2 extraction during ramp cycling exercise was not altered by CF, yet SpO2 was lower, the present findings support the notion of centrally mediated oxygen delivery to principally limit the aerobic function of pediatric patients with CF during ramp incremental cycling exercise.
Abstract Background Despite a growing body of research investigating high-intensity interval training (HIIT) in schools, there are limited process evaluations investigating their implementation. This is concerning because process evaluations are important for appropriately interpreting outcome findings and augmenting intervention design. This manuscript presents a process evaluation of Making a HIIT , a school-based HIIT intervention. Methods The Making a HIIT intervention spanned 8 weeks and was completed at three schools in Greater Brisbane, Australia. Ten classes (intervention group) completed 10-min teacher-led HIIT workouts at the beginning of health and physical education (HPE) lessons, and five classes (control group) continued with regular HPE lessons. The mixed methods evaluation was guided by the Framework for Effective Implementation by Durlak and DuPre. Results Program reach : Ten schools were contacted to successfully recruit three schools, from which 79% of eligible students ( n = 308, $$\overline{{\text{x}} }$$ x¯ age: 13.0 ± 0.6 years, 148 girls) provided consent. Dosage : The average number of HIIT workouts provided was 10 ± 3 and the average number attended by students was 6 ± 2. Fidelity : During HIIT workouts, the percentage of time students spent at ≥ 80% of maximum heart rate (HR max ) was 55% (interquartile range (IQR): 29%—76%). Monitoring of the control group : During lessons, the intervention and control groups spent 32% (IQR: 12%—54%) and 28% (IQR: 13%—46%) of their HPE lesson at ≥ 80% of HR max , respectively. Responsiveness : On average, students rated their enjoyment of HIIT workouts as 3.3 ± 1.1 (neutral) on a 5-point scale. Quality : Teachers found the HIIT workouts simple to implement but provided insights into the time implications of integrating them into their lessons; elements that helped facilitate their implementation; and their use within the classroom. Differentiation : Making a HIIT involved students and teachers in the co-design of HIIT workouts. Adaption : Workouts were modified due to location and weather, the complexity of exercises, and time constraints. Conclusion The comprehensive evaluation of Making a HIIT provides important insights into the implementation of school-based HIIT, including encouragings findings for student enjoyment and fidelity and recommendations for improving dosage that should be considered when developing future interventions. Trial Registration ACTRN, ACTRN12622000534785 , Registered 5 April 2022 – Retrospectively registered.
Abstract Among 1038 participants with pulmonary Mycobacterium avium complex and 120 with Mycobacterium abscessus enrolled in the US Bronchiectasis and NTM Research Registry, less than half received antibiotic therapy in the 24 months before registry enrollment, of which less than half were guideline based. Adverse effects occurred in 21% of therapy recipients, of whom 33% discontinued therapy.
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