Was it a HIIT? A process evaluation of a school-based high-intensity interval training intervention

This is the final version. Available on on open access from BMC via the DOI in this recordAvailability of data and materials: Data are available from the corresponding author on reasonable request.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, 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 (HRmax) 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 HRmax, 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 encouraging findings for student enjoyment and fidelity and recommendations for improving dosage that should be considered when developing future interventions.QUEX Institute for Global ExcellenceSports Medicine Australi

Sex modifies the relationship between age and neurovascular coupling in healthy adults

This is the final version. Available on open access from SAGE Publications via the DOI in this recordNeurovascular coupling (NVC) is the matching between local neuronal activity and regional cerebral blood flow (CBF), but little is known about the effects of age and sex on NVC. This study aimed to investigate the relationships and interaction between age and sex on NVC. Sixty-four healthy adults (18-85 years, N = 34 female) completed a visual stimulus evoked NVC assessment to a flashing checkerboard. NVC responses were measured in the posterior cerebral artery (PCAv) using transcranial Doppler ultrasound. A hierarchical multiple regression was used to determine the relationships between age, sex, and the age by sex interaction on NVC. There was a significant age by sex interaction for baseline (P = 0.001) and peak PCAv (P = 0.01), with a negative relationship with age in females (P < 0.005), and no relationship in males (P ≥ 0.17). NVC responses as a percent increase from baseline showed a significant age by sex interaction (P = 0.014), with a positive relationship with age in females (P = 0.04) and no relationship in males (P = 0.17), even after adjusting for baseline PCAv. These data highlight important sex differences, with an association between age and NVC only apparent in females but not males, and thus a need to account for sex dependent effects of ageing when investigating cerebrovascular regulation.QUEX Institut

The reliability of a breath‐hold protocol to determine cerebrovascular reactivity in adolescents

This is the published version. Available on open access from Wiley via the DOI in this recordPurpose Cerebrovascular reactivity (CVR) is impaired in adolescents with cardiovascular disease risk factors. A breath‐hold test is a noninvasive method of assessing CVR, yet there are no reliability data of this outcome in youth. This study aimed to assess the reliability of a breath‐hold protocol to measure CVR in adolescents. Methods Twenty‐one 13 to 15 year old adolescents visited the laboratory on two separate occasions, to assess the within‐test, within‐day and between‐day reliability of a breath‐hold protocol, consisting of three breath‐hold attempts. CVR was defined as the relative increase from baseline in middle cerebral artery mean blood velocity following a maximal breath‐hold of up to 30 seconds, quantified via transcranial Doppler ultrasonography. Results Mean breath‐hold duration and CVR were never significantly correlated (r  .08). The within‐test coefficient of variation for CVR was 15.2%, with no significant differences across breath‐holds (P = .88), so the three breath‐hold attempts were averaged for subsequent analyses. The within‐ and between‐day coefficients of variation for CVR were 10.8% and 15.3%, respectively. Conclusions CVR assessed via a three breath‐hold protocol can be reliably measured in adolescents, yielding similar within‐ and between‐day reliability. Analyses revealed that breath‐hold length and CVR were unrelated, indicating the commonly reported normalization of CVR to breath‐hold duration (breath‐hold index) may be unnecessary in youth

The acute and postprandial effects of sugar moiety on vascular and metabolic health outcomes in adolescents

This is the author accepted manuscript. The final version is available from Canadian Science Publishing via the DOI in this recordThis study explored the cardiometabolic responses to sugar moieties acutely, and following a subsequent mixed meal tolerance test (MMTT). Twenty-one healthy adolescents (N=10 female, 14.3±0.4 years) completed three experimental and one control condition, in a counterbalanced order. These consisted of different drinks to compare the effect of 300 mL of water (control), or 300 mL of water mixed with 60 g of glucose, fructose or sucrose, on vascular function (flow-mediated dilation; FMD, microvascular reactivity (total hyperaemic response; TRH); and cerebrovascular reactivity; CVR), and blood samples for [uric acid], [glucose], [triglycerides] and [lactate]. FMD increased 1 hour after glucose and sucrose (P<0.001, ES≥0.92) but was unchanged following fructose and water (P>0.19, ES>0.09). CVR and TRH were unchanged 1 hour following all conditions (P>0.57, ES>0.02). Following the MMTT, FMD was impaired in all conditions (P0.40) with no differences between conditions (P>0.13, ES<0.39). Microvascular TRH was increased in all conditions (P=0.001, ES=0.88), and CVR was preserved in all conditions post MMTT (P=0.87, ES=0.02). Blood [uric acid] was elevated following fructose consumption and the MMTT (P0.40). Consumption of a sugar sweetened beverage did not result in vascular dysfunction in healthy adolescents, however the vascular and metabolic responses were dependent on sugar moiety

Effect of preoperative thoracic duct drainage on canine kidney transplantation

Chronic drainage of the thoracic duct to the esophagus was developed in dogs, and its efficacy in immunomodulation was tested using kidney transplantation. Compared to 9.7 days in the control, the mean animal survival was prolonged to 9.9 days, 17.8 days, and 18.5 days when TDD was applied preoperatively for 3 weeks, 6 weeks, and 9 weeks, respectively. Prolongation was significant after 6 weeks. Patency of the fistula was 93.5, 80.4, and 76.1% at respective weeks. Number of peripheral T-lymphocytes determined by a new monoclonal antibody diminished after 3 weeks. All animals were in normal health, requiring no special care for fluid, electrolyte, or protein replacement

The acute effect of exercise intensity on peripheral and cerebral vascular function in healthy adults

This is the author accepted manuscript. The final version is available from the American Physiological Society via the DOI in this recordThe acute effect of exercise intensity on cerebrovascular reactivity, and whether this mirrors changes in peripheral vascular function, has not been investigated. The aim of this study was to explore the acute effect of exercise intensity on cerebrovascular reactivity (CVR) and peripheral vascular function in healthy young adults (n=10, 6 females, 22.7 ± 3.5 years). Participants completed four experimental conditions on separate days: high intensity interval exercise (HIIE) with intervals performed at 75% maximal oxygen uptake (V̇O2max; HIIE1), HIIE with intervals performed at 90% V̇O2max (HIIE2), continuous moderate intensity exercise (MIE) at 60% V̇O2max and a sedentary control condition (CON). All exercise conditions were completed on a cycle ergometer and matched for time (30 min) and average intensity (60% V̇O2max). Brachial artery flow-mediated dilation (FMD) and CVR of the middle cerebral artery were measured before exercise, and one- and three hours post-exercise. CVR was assessed using transcranial Doppler ultrasonography to both hypercapnia (6% carbon dioxide breathing) and hypocapnia (hyperventilation). FMD was significantly elevated above baseline one and three hours following both HIIE conditions (P0.33). CVR to both hypercapnia and hypocapnia, and when expressed across the end-tidal CO2 range, was unchanged in all conditions, at all time points (all P>0.14). In conclusion, these novel findings show that the acute increases in peripheral vascular function following HIIE, compared to MIE, were not mirrored by changes in cerebrovascular reactivity, which was unaltered following all exercise conditions in healthy young adults.Physiological Societ

The within and between-day reliability of cerebrovascular reactivity using traditional and novel analytical approaches

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordData Availability Statement: All data supporting the results of this paper is reported in the manuscript (Table 1, Table 2, Table 3 and Table 4). Data not included in this manuscript can be found on the online repository as supporting informationCerebrovascular reactivity of the middle cerebral artery velocity (CVR MCAv) to carbon dioxide (CO2) is a common method to assess cerebrovascular function. Yet, the approaches used to calculate CVR outcomes vary. The aim of this study was to explore the within and between-day reliability of traditional CVR outcomes. The second aim was to explore the reliability of novel kinetic-based analyses. Healthy adults (n=10, 22.3±3.4 years) completed assessments of CVR over four minutes using a fixed fraction of inspired CO2 (6%). This was repeated across four separate visits (between-day), and on one visit measures were repeated 2.5 hours later (within-day). No mean biases were present between assessments for traditional CVR metrics, expressed as absolute (cm/s/mmHg) or relative (%/mmHg) outcomes (minute-3, minute-4, peak 1 second, peak 30 second) (between-day: P>0.14, ηp20.22, d>0.27). Absolute, rather than relative CVR, yielded the most reproducible parameters (coefficient of variation: 8.1-13.2% versus 14-83% respectively). There were significant differences between CVR outcomes (P0.89) dependent on the time point used to determine CVR, as a steady state MCAv response was rarely observed. Furthermore, the MCAv response was not reproducible within an individual (kappa=0.15, P=0.09). No mean differences were present for novel kinetic outcomes (amplitude, time-delay, time constant) (between-day: P>0.05, d0.38, d<0.25). The results support the need for standardisation and indicate CVR should be defined as a dynamic peak, rather than a set time point for increased reliability. For novel kinetic outcomes variability was greater (CV: 8.7-120.9%) due to the nature of time-based metrics.QUEX InstitutePhysiological Societ

The relationships between age, sex and cerebrovascular reactivity to hypercapnia using traditional and kinetic-based analyses in healthy adults

This is the author accepted manuscript. The final version is available from the American Physiological Society via the DOI in this recordThe effect of age and sex on intracranial and extracranial cerebrovascular function is poorly understood. We investigated the relationships between age, sex and cerebrovascular reactivity (CVR) to hypercapnia in 73 healthy adults (18-80 years, N=39 female). CVR to hypercapnia was assessed in the middle cerebral artery (MCA) using transcranial Doppler ultrasound and at the internal carotid artery (ICA) using duplex ultrasound. MCA CVR was characterised by peak MCA velocity (MCAv) response per mmHg increase in end-tidal CO2, and by using a mono-exponential model to characterize the kinetics (time-constant) of the MCAv response. ICA reactivity was assessed as the relative peak increase in artery diameter. Hierarchical multiple regression determined the relationships between age, sex, and the age by sex interaction on all baseline and CVR outcomes. There was no relationship between ICA reactivity (%) with age (P=0.07), sex (P=0.56) or a moderator effect of sex on the age effect (P=0.24). MCAv CVR showed no relationship with age (P=0.59), sex (P=0.09), or an age by sex moderator effect (P=0.90). We observed a positive relationship of MCAv CVR time-constant with age (P=0.013), such that the speed of the MCA response was slower with advancing age. The present study provides comprehensive data on age and sex specific relationships with intracranial and extracranial cerebrovascular responses to hypercapnia. Despite similar MCAv CVR and ICA reactivity between sexes, kinetic responses of the MCA revealed a slower rate of adjustment with advancing age.QUEX Institut