Exploring How Older Adult's Gender Role is Associated with Studied Outcomes Following an Outdoor Exercise Structure Program.

This study aimed to describe the gender roles of people interested in an exercise program done on outdoor exercise structures and test if gender roles were associated with studied outcomes. Older adults aged 65+ who were not currently performing resistance training were invited to participate. Gender roles were quantified using the Bem Sex Role Inventory 30-item questionnaire (-60 [feminine] to +60 [masculine]). Outcomes included completing the 6-week intervention (Y/N) and changes in physical function (one leg stance, 30-s chair stand), strength (predicted maximal chest press and leg press, grip strength), power (knee extensor power), and overall health via the SF-36 questionnaire. Twenty-nine adults (65.5% female; median 72 years old) participated in the study, and 17 completed the intervention (58.6%). The median (interquartile) gender role score was -13.0 (-19.5 to -8.5), with no gender role difference (p = .62) between completers and non-completers. These results suggest that older adults interested in such a program portray themselves as more feminine. No association was found between gender role scores and changes in any study outcomes. In this setting, gender roles did not seem to impact the study outcomes and therefore may not need to be considered when designing an outdoor exercise structure program.

An Examination of Exercise Intensity and its Impact on the Acute Release of Irisin Across Obesity Status: A Randomized Controlled Crossover Trial.

Limited data exist regarding the impact of exercise intensity on irisin release and its association with insulin sensitivity in individuals of differing obesity status. The objective of this study was to investigate the impact of exercise intensity on the acute release of irisin in healthy weight individuals and individuals with obesity, and whether irisin release during acute exercise was associated with greater insulin sensitivity across obesity status. A randomized controlled crossover study was conducted on 26 non-obese (NOB) (BMI: 22.2±1.5 kg/m2) and 26 OB (BMI: 33.9±6.5 kg/m2) adults who performed an acute bout of moderate-intensity continuous training (MICT), high-intensity interval training (HIIT), and rest. Irisin was quantified via ELISA and western blotting, and insulin sensitivity (Si) was estimated using the Matsuda index. OB displayed a significantly lower level of circulating irisin and protein expression compared to NOB (p<0.01). Insulin sensitivity was positively correlated with irisin release during MICT and HIIT in NOB (all p<0.05), but not in OB. Regarding irisin expression, NOB with high-Si had a 2.03-fold (p<0.05) increase during HIIT, while OB with high-Si had only a 1.54-fold increase (p<0.05). These results suggest that irisin is released differently according to obesity status and varying exercise intensities. OB individuals have a blunted irisin response to acute exercise and lower baseline irisin concentrations compared to NOB individuals. Although exercise stimulates irisin release in NOB individuals, only a greater exercise intensity stimulates irisin release in OB individuals. These findings are clinically relevant, as irisin is associated with greater insulin sensitivity.

Impact of Outdoor Play Structures on Moderate to Vigorous Physical Activity in Children during Recess: A Comparative Study.

BACKGROUND/OBJECTIVES: It is believed that outdoor play structures lead to more physical activity for kids during school recess. However, the intensity of this activity remains unknown. This study explored whether access to outdoor play structures during recess interferes with children's physical activity levels. METHODS: Forty-one children (8-10 years old) accessed play structures during the afternoon recess but not in the morning for one entire week. To control for temperature differences, the same number of participants from another school who did not access playground structures were invited to participate. Moderate to Vigorous Physical Activity (MVPA) was determined using heart rate reserve. Heart rate was recorded using the Fitbit Inspire 2 (San Francisco, CA, USA) for at least three full school days. Wilcoxon signed-rank and Mann-Whitney U tests analyzed within- and between-group differences. RESULTS: The findings show no difference in MVPA when accessing or not accessing outdoor play structures, both within groups [(n = 37) median (25th-75th) 16 min (7-30) vs. 14 min (5-22)] and between groups [(n = 22) 16 min (7-26)]. The weekly MVPA for all participants (n = 59) [172 min (117-282)] was the strongest variable associated with MVPA during recess [t(df) = 5.40 (38), 95% CI 0.04-0.09, p < 0.001]. CONCLUSION: accessibility to outdoor play structures does not increase MVPA during recess in children aged 8 to 10. Therefore, schools may need various options for children to play during recess, allowing them to accumulate MVPA.

Synchronous Group-Based Online Exercise Programs for Older Adults Living in the Community: A Scoping Review.

Older adults are the least physically active group with specific barriers to regular exercise, and online exercise programs could overcome some of those barriers. This scoping review aimed to describe the characteristics of supervised group-based synchronous online exercise programs for older adults living in the community, their feasibility, acceptability, and potential benefits. MEDLINE (Ovid), Embase, SPORTDiscus, and the Cumulative Index to Nursing and Allied Health Literature were searched until November 2022. The included studies met the following criteria: participants aged 50 years and above, a minimum of a 6-week group-based supervised and synchronous intervention, and original articles available in English. Eighteen articles were included, with 1,178 participants (67% female, average age of 71 [57-93] years), most (83%) published in the past 3 years. From the limited reported studies, delivering supervised, synchronous online exercise programs (one to three times/week, between 8 and 32 weeks) for older adults living in the community seems feasible, accepted, and can improve physical function.

Does type 2 diabetes duration influence the effectiveness of an aerobic exercise intervention: Results from the INTENSITY study.

BACKGROUND: Studies suggest that longer durations of T2DM increase the risk of T2DM complications and premature mortality. However, whether T2DM duration impacts the efficacy of an aerobic exercise intervention is unclear. OBJECTIVE: The purpose of this study was: 1) to compare changes in body composition, cardiorespiratory fitness, and glycemia between individuals with short- and long-duration T2DM after aerobic exercise and 2) to determine whether these changes were associated with changes in glycemia by T2DM duration. METHODS: A secondary analysis of the INTENSITY study (NCT03787836), including thirty-four adults (≥19 years) with T2DM who participated in 28 weeks of aerobic exercise training for 150 minutes per week at a moderate-to-vigorous intensity (4.5 to 6.0 metabolic equivalents (METs)). Using pre-established cut-points, participants were categorized into two groups 1) short-duration T2DM (<5 years) or 2) long-duration T2DM (≥5 years). Glycemia was measured by glycated hemoglobin (HbA1c), body composition by BodPod, and cardiorespiratory fitness by a measure of peak oxygen consumption (VO2peak). All measurements were performed at baseline, 16 weeks, and 28 weeks. RESULTS: Participants in the short-duration T2DM group experienced decreases in fat mass (kg) (p = 0.03), HbA1c (p = 0.05), and an increased relative VO2peak (p = 0.01). Those with long-duration T2DM experienced decreases in fat mass (kg) (p = 0.02) and HbA1c (p <0.001) and increased fat-free mass (p = 0.02). No significant differences were observed between groups in any outcomes. Changes in fat mass (r = 0.54, p = 0.02), and body fat percentage (r = 0.50, p = 0.02) were significantly associated with the change in HbA1c in those with a long-duration T2DM only. CONCLUSION: Our results suggest T2DM duration did not differently impact the efficacy of a 28-week aerobic exercise intervention. However, changes in body composition were associated with better glycemia in individuals with longer T2DM duration only.

Association between physical fitness and executive functions in cognitively healthy female older adults: a cross-sectional study.

Cardiovascular endurance and muscular fitness seem to impact specific cognitive components in older females. However, it remains uncertain whether these relate to executive functions or if these correlations are limited to specific physical fitness indicators. This study aimed to determine the association between specific physical fitness components and executive functions in community-dwelling older females. Thirty-five cognitively healthy community-dwelling older females (71.5 ± 5.7 years) underwent a series of physical fitness tests. These included the handgrip strength test (HGT), the 6-min walk test (6MWT), the 8-foot up-and-go test (8FUGT), and the chair stand test (CST). Participants also completed trail A and trail B of the cognitive trail making test. Results showed that trail B reaction time had a negative association with both HGT (r = - 0.502; p = 0.002) and 6MWT (r = - 0.543; p < 0.001). Together, the HGT and 6MWT results explained 39% of the variation in trail B reaction times: HGT accounted for 18% and 6MWT for 21%. Better scores on the 6MWT and HGT-but not on the 8FUGT and CST-correlated with enhanced executive function in cognitively healthy community-dwelling older females. The results of this study underscore the importance of specific physical assessments, like the 6MWT and HGT, as potential indicators of executive function, offering targeted strategies for maintaining cognitive health in aging females.

Association between changes in habitual stepping activity and cognition in older adults.

Advancing age is associated with declines in cognitive function. Although physical activity is thought to protect against this decline, it is unclear how a short-term uptake in daily steps or a decline in day-to-day step variability may contribute to cognition among older adults. We tested associations between changes in step counts, day-to-day step variability and executive cognitive functions among older adults taking part in a physical activity intervention. Thirty-seven older adults (33 females; 71.4 ± 6.3 years) completed a 10-week personalized physical activity intervention. Participants wore a Fitbit to measure daily step counts throughout the study. They also completed a computerized Stroop task before and after the intervention. Average step counts and step count variability via average-real-variability (ARV) were determined. Compared to pre-intervention, step counts increased (p < 0.001) and step variability decreased post-intervention (p = 0.04). Models describing the changes in step counts and ARV over the 10-weeks were cubic (both, p < 0.04). Reaction times during the simple (p = 0.002) and switching (p = 0.04) conditions were faster post-intervention. Change in step variability was positively associated with the change in reaction time for the switching condition (ß = 0.029, p = 0.002). On average, a reduction in day-to-day step variability was associated with improvements in cognitive flexibility.

Increasing aerobic exercise intensity fails to consistently improve the glycemic response in people living with prediabetes or type 2 diabetes mellitus: the INTENSITY trial.

Some individuals with prediabetes or type 2 diabetes mellitus (T2DM) who engage in exercise will not experience the anticipated improvements in glycemic control, referred to as non-responders. Increasing exercise intensity may improve the proportion of individuals who become responders. The objectives were to (i) identify responders and non-responders based on changes in glycated hemoglobin (HbA1c) in individuals with prediabetes or T2DM following 16 weeks of aerobic exercise; (ii) investigate if increasing exercise intensity enhances the responders' status for individuals not previously responding favourably to the intervention. Participants (n = 40; age = 58.0 years (52.0-66.0); HbA1c = 7.0% (6.0-7.2)) engaged in a two-phase, randomized study design. During phase one, participants performed 16 weeks of treadmill-based, supervised, aerobic exercise at 4.5 metabolic equivalents (METs) for 150 min per week. Thereafter, participants were categorized as responders, non-responders, or unclear based on the 90% confidence interval above, below, or crossing a 0.3% reduction in HbA1c. For phase two, participants were randomized to a maintained intensity (4.5 METs) or increased intensity (6.0 METs) group for 12 weeks. Following phase one, two (4.1%) participants were categorized as responders, four (8.2%) as non-responders, and 43 (87.7%) as unclear. Following phase two, two from the increased intensity group and one from the maintained intensity group experienced an improvement in response categorization. There were no significant between or within group (maintained vs. increased) differences in HbA1c. For most people with prediabetes or T2DM, increasing exercise intensity by 1.5 METs does not improve response categorization.

Resistance Training on an Outdoor Exercise Structure Improves Lower-Body Relative Strength in Older Adults.

Improving relative strength is important for maintaining functionality with age, and outdoor exercise structures could be useful to facilitate this. A total of 29 adults aged 65+ participated in a non-randomized crossover study with a 6-week control followed by a 6-week resistance training intervention on an outdoor exercise structure (3x/week). Relative strength (predicted maximal leg press/lower body lean mass [Dual-energy X-ray Absorptiometry]) and physical function variables were measured at baseline, post-control, and post-intervention. Represented as median (25th-75th), lower body relative strength improved from 7.91 (7.01-9.35) post-control to 8.50 (7.99-9.72) post-intervention (p = .002) in study completers (n = 17). Maximum leg press (p = .002), 30-second chair stand (p < .001), one-leg stance (p = .011), and maximum chest press (p = .009) also improved significantly during the intervention. There were no significant changes in aerobic activity, grip strength, lean mass, or muscle power. This study demonstrates that there could be potential relative strength benefits associated with the use of outdoor exercise structures in older adults.

Comparing Online and In-Person Delivery of a Fall Prevention Exercise Program for Older Adults.

Exercise is the single most effective strategy to reduce the risk of falls. Online classes have grown in popularity, but the benefits of online classes remain unknown. Zoomers on the Go is a peer-led 12-week exercise program offered twice weekly to adults 50+ years old. The main outcome was lower body strength measured by the 30-s chair stand test. Other outcomes included dropout, attendance, balance, cardiorespiratory fitness, and perceived health. A total of 74 participants (age 66.3 ± 7.1 years) in the online group and 84 participants in the in-person group (age 67.3 ± 7.2 years) completed the program, with attendance for the online group. Both groups significantly improved their 30-s chair stand, cardiorespiratory fitness, and balance (p < .001) with no difference in functional benefits between groups. The in-person group improved their perceived health and significantly reduced levels of stress and depression, while no such changes were observed in the online group.

Frailty is associated with worse executive function and higher cerebral blood velocity in cognitively healthy older adults: a cross-sectional study.

Frailty is characterized by an increased vulnerability to adverse health events. Executive function impairment is an early sign of progression towards cognitive impairments. Whether frailty is associated with executive function and the associated mechanisms are unclear. We test the hypothesis that higher frailty is associated with worse executive function (Trail Making Test) and if aerobic fitness, prefrontal cortex oxygenation (ΔO2Hb), or middle-cerebral artery velocity (MCAv) impact this association. Forty-one (38 females) cognitively health older adults (70.1 ± 6.3 years) completed a Trail task and 6-min walk test. Prefrontal cortex oxygenation was measured during the Trail task (via functional near-infrared spectroscopy) and MCAv in a sub-sample (n=26, via transcranial Doppler). A 35-item frailty index was used. Frailty was independently, non-linearly related to trail B performance (Frailty2: ß=1927 [95% CI: 321-3533], p = 0.02), with the model explaining 22% of the variance of trail B time (p = 0.02). Aerobic fitness was an independent predictor of trail B (ß=-0.05 [95% CI: -0.10-0.004], p = 0.04), but age and ΔO2Hb were not (both, p > 0.78). Frailty was positively associated with the difference between trails B and A (ß=105 [95% CI: 24-186], p = 0.01). Frailty was also associated with a higher peak MCAv (ρ = 0.40, p = 0.04), but lower ΔO2Hb-peakMCAv ratio (ρ = -0.44, p = 0.02). Higher frailty levels are associated to worse Trail times after controlling for age, aerobic fitness, and prefrontal oxygenation. High frailty level may disproportionately predispose older adults to challenges performing executive function tasks that may manifest early as a compensatory higher MCAv despite worse executive function, and indicate a greater risk of progressing to cognitive impairment.

Online exercise program for men living with obesity: Experiences, barriers, and enablers.

The prevalence of obesity is increasing among men, and this population remains under-represented in lifestyle and weight management interventions. The current study aims to explore the experiences of men living with obesity (body fat ≥25 %) toward a 12-week supervised online exercise platform. Ten men were interviewed for this qualitative study. Semi-structured, open-ended phone interviews were conducted, and the transcripts were thematically coded using the qualitative data analysis Nvivo QSR software package. The research findings are illustrated using quotes from participants. The results were organized into two main themes: those that removed barriers to exercise and those that improved the enablers of exercise. Eliminating barriers included not purchasing specialized equipment or travelling to a gym facility. The enablers to their success with the program included the structured format of the circuit program and having supervised sessions. By removing barriers and enhancing enablers, the 12-week online exercise circuit program increased compliance to and success of the exercise program for men living with obesity. Future research should explore the long-term effects of an online program for men living with obesity and its appeal beyond COVID-19.

Online Circuit Training Increases Adherence to Physical Activity: A Randomized Controlled Trial of Men with Obesity.

PURPOSE: This study aimed to examine adherence to the weekly physical activity guidelines (≥150 min of aerobic activities at moderate-to-vigorous intensity and two or more sessions of strength training (yes or no)) and health outcomes during the COVID-19 pandemic for men living with obesity, 46 wk after being offered an online muscle-strengthening circuit program for 12 wk. METHODS: Sixty men (age ≥19 yr) living with obesity (body fat percentage ≥25%) were randomly assigned to the intervention group ( n = 30) or the control condition ( n = 30) for 12 wk. The intervention group was offered an online circuit training, three sessions per week, whereas the control group received a website helping them to reach the physical activity guidelines. Adherence to the weekly physical activity guidelines was evaluated 46 wk after enrolling in the program using a heart rate tracker (Fitbit Charge 3) and an exercise log. Health outcomes (e.g., anthropometrics, body composition) were measured at baseline and after 12, 24, and 46 wk. RESULTS: The intervention group had higher adherence to physical activity guidelines at 46 wk (36.8%) than the control group (5.3%; P = 0.02). However, no difference in health outcomes was observed between participants in the intervention group compared with the control group after 12, 24, and 46 wk. CONCLUSIONS: Increasing adherence to exercise in men living with obesity is challenging. The proposed program increased adherence to the physical activity guidelines after about a year for men living with obesity; however, more studies are needed to understand how to improve health outcomes when following an online delivery exercise program in this population.

The Effect of a Standing Intervention on Falls in Long Term Care: a Secondary Analysis of a Randomized Controlled Trial.

Background: Older adults in long term care (LTC) spend over 90% of their day engaging in sedentary behaviour. Sedentary behaviour may exacerbate functional decline and frailty, increasing the risk for falls. The purpose of this study is to explore the impact of a 22-week standing intervention on falls among LTC residents at 12-month follow-up. Methods: This was a planned secondary analysis of the Stand if You Can randomized controlled trial. The original trial randomized 95 participants (n = 47 control; n = 48 intervention) to either a sitting control or a supervised standing intervention group (100 minutes/week) for 22 weeks. Falls data were available to be collected over 12 months post-intervention for 89 participants. The primary outcome was a hazard of fall (Yes/No) during the 12-month follow-up period. Results: A total of 89 participants (average age 86 years ± 8.05; 71.9% female) were followed for 12-months post-intervention. Participants in the intervention group (n=44) had a significantly greater hazard ratio of falls (2.01; 95% CI = 1.11 to 3.63) than the control group (n=45) when accounting for the history of falls, frailty status, cognition level, and sex. Conclusion: Participants who received a standing intervention over 22 weeks were twice as likely to fall 12 months after the intervention compared with the control group. However, the prevalence of falls did not surpass what would be typically observed in LTC facilities. It is imperative that future studies describe in detail the context in which falls happen and collect more characteristics of participants in the follow-up period to truly understand the association between standing more and the risk of falls.

The impact of sprint interval training with or without weight loss on substrate oxidation in adults: A secondary analysis of the i-FLEX study.

Endurance exercise training and weight loss (WL) have been associated with changes in fat oxidation. However, there is limited evidence investigating the impact of sprint interval training (SIT)-induced WL on fat oxidation in adults. To investigate the impact of SIT with or without WL on fat oxidation, 34 adults aged 19-60 years (males, n = 15) took part in 4-week SIT. SIT consisted of 30-s Wingates starting with two intervals and working up to four interspersed with 4 min of active recovery. Fat oxidation was estimated via indirect calorimetry using a metabolic cart during submaximal cycling. Following the intervention, participants were classified into a WL group (weight change >0 kg) or a non-WL group (weight change ≤0 kg). No difference in resting fat oxidation (p = 0.642) and respiratory exchange ratio (RER) (p = 0.646) were observed between the groups. There was a significant interaction for the WL group with increased submaximal fat oxidation usage (p = 0.005) and decreased submaximal RER over the duration of the study (p = 0.017). When adjusted for baseline weight and sex, submaximal fat oxidation usage remained significant (p < 0.05), while RER did not (p = 0.081). The WL group had higher work volume, relative peak power, and mean power than the non-WL group (p < 0.05). Short-term SIT elicited significant improvements in submaximal RER and fat oxidation (FOx) in adults that lost weight, which may be explained by an increase in work volume throughout SIT training.

Long-term care residents' acceptance of a standing intervention: A qualitative intrinsic case study.

Older adults in long-term care are sedentary. Standing is recommended to reduce sedentary time, but there is limited research on long-term care residents' acceptability of standing interventions. The acceptability of the Stand If You Can (SIYC) randomized clinical trial among long-term care residents was explored using a single intrinsic qualitative case study design. The five month intervention consisted of supervised 100 min standing sessions per week. Participants completed post-intervention interviews, which were analyzed using the Thematic Framework Analysis through the lens of an acceptability framework. The 10 participants (7 female), age 73 to 102 years, stood a median of 53% of the intervention offered time (range 20%-94%). The participants reported acceptability in many aspects of the Theoretical Framework of Acceptability. Standing is a simple intervention to decrease sedentary time and seems to be accepted among long-term care residents when burden is not perceived as too high.

Fear of Falls Following an Online Exercise Program for Aging Adults.

Individuals who participate in regular exercise tend to report a lower fear of falling; however, it is unknown if this fear can be reduced following an online fall prevention exercise program. The main purpose of this study was to test if offering a peer-led fall prevention exercise program online reduced the fear of falling and if this potential improvement was greater than when the program was offered in person. The secondary objectives were to describe participants' characteristics when participating online, the rate of falls and the context in which falls occur. A total of 85 adults aged 69.0 ± 7.8 years participated in the program offered online (n = 44) and in-person (n = 41). No significant differences in fear of falling before and after participation in the program were reported for either group: online (20.7 ± 5.1-21.8 ± 5.5) and in-person (20.6 ± 5.1-21.2 ± 5.3). Online participants reported a greater proportion of falls (n = 9; 20.5% vs. n = 4; 9.8%; p = .14), mostly occurring outdoors (n = 7) (77.8). A properly designed study is needed to test if the rate of falls is greater when an exercise program is offered online.

Examining the role of sex on the benefits of muscle-strengthening activities for people living with obesity: A cross-sectional study.

Aims: To investigate the correlations between meeting the muscle-strengthening activities guideline, body fat %, and mortality for individuals living with obesity and to explore if these correlations are moderated by sex. Methods: Data from 3915 adults (51.9% women; 48.1% men ) living with obesity (body fat % ≥25 for men and ≥35 for women) from two cycles of the National Health and Nutrition Examination Survey (NHANES 2003-04/2005-06) were analyzed. Muscle-strengthening activities were self-reported via a questionnaire, body fat % was measured via Dual Energy X-ray, and mortality was obtained via administrative data for an average of 10 years. Results: 18.7% of men and 15.2% of women living with obesity met the muscle-strengthening activities guideline (p = 0.021) . Sex was correlated with body fat %; (ß (SE)= 11.34 (0.18); p ≤ 0.001) and risk of mortality (hazard ratio (95% confidence interval) = 0.36 (0.24-0.54); p ≤ 0.001), once adjusted for confounders (weekly aerobic activities, ethnicity, education, household income, smoking, and the sum of chronic conditions). The interaction between sex and meeting the muscle-strengthening activities guideline was not significantly correlated with the studied outcomes. Conclusion: Performing muscle-strengthening activities a minimum of two times per week does not impact body fat % or risk of mortality (over 10 years) differently in men or women living with obesity.

Extracellular Vesicles as Predictors of Individual Response to Exercise Training in Youth Living with Obesity.

BACKGROUND: Exercise is associated with health benefits, including the prevention and management of obesity. However, heterogeneity in the adaptive response to exercise training exists. Our objective was to evaluate if changes in extracellular vesicles (EVs) after acute aerobic exercise were associated with the responder phenotype following 6-weeks of resistance training (RT). METHODS: This is a secondary analysis of plasma samples from the EXIT trial (clinical trial#02204670). Eleven sedentary youth with obesity (15.7 ± 0.5 yrs, BMI ≥95th percentile) underwent acute exercise (60% HRR, 45 min). Blood was collected at baseline [AT0 min], during [AT15-45 min], and 75 min post-recovery [AT120], and EVs purified using size exclusion chromatography from extracted plasma. Afterward, youth participated in 6-weeks RT and were categorized into responders or non-responders based on changes in insulin sensitivity. RESULTS: We assessed EV biophysical profile (size, zeta potential, protein yield, and EV subtype protein expression) in a single-blind fashion. Overall, there was a general increase in EV production in both groups. Average EV size was larger in responders (~147 nm) vs. non-responders (~124 nm; p < 0.05). EV size was positively associated with absolute change in Matsuda index (insulin sensitivity) following RT (r = 0.44, p = 0.08). EV size distribution revealed responders predominantly expressed EVs sized 150-300 nm, whereas non-responders expressed EVs sized 50-150 nm (p < 0.05). At baseline, responders had ~25% lower TSG101, ~85% higher MMP2 levels. EV protein yield was higher in responders than non-responders at AT15 (p < 0.05). CONCLUSIONS: Our data suggest that youth with obesity that respond to RT produce larger EVs that are TSG101+ and CD63+, with increased EV protein yield during acute exercise.

Irisin response to acute moderate intensity exercise and high intensity interval training in youth of different obesity statuses: A randomized crossover trial.

Limited data exist regarding the impact of an acute bout of exercise with varying intensities on irisin levels in the youth of different obesity statuses. The objectives were to (1) compare an acute bout of moderate continuous intensity (MCI) exercise and an acute bout of high-intensity interval training (HIIT) on irisin response in youth with different obesity statuses and, (2) investigate whether changes in irisin levels are correlated with exploratory outcomes. A randomized crossover design study was conducted on 25 youth aged 12-18 years old. Participants were classified as either healthy weight (BMI percentile <85; n = 14) or overweight/obese (BMI percentile ≥85; n = 11). Participants performed an MCI exercise session at 50% of heart rate reserve for 35 min and a HIIT exercise session for 35 min, with intervals every 5 min increasing from 50% heart rate reserve to 85-90% for 2 min. Irisin was measured using an enzyme-linked immunoabsorbent assay from plasma sampling obtained throughout the exercise (at times 0, 7, 14, 21, 28, and 35 min). A time effect was observed throughout the HIIT session [F(1,5) = 6.478, p < 0.001]. Bonferonni post-hoc analysis revealed significant differences in irisin levels post-exercise (35 min) compared to times 7, 14, 21, and 28 min. Irisin increased during HIIT (81.0% ± 71.3; p = 0.012) in youth with a healthy weight. No differences were observed for youth living as overweight or with obesity. Overall, HIIT elicits a higher peak irisin response compared to MCI exercise training in youth.