Martin Sénéchal

Introduction: Individuals with type 2 diabetes (T2D) display reduced cardiorespiratory fitness, a strong predictor of premature mortality and T2D-related complications. Aerobic training (AT) enhances cardiorespiratory fitness and is a cornerstone in T2D management. Emerging data suggest that AT combined with blood flow restriction (AT+BFR) may elicit greater improvements in cardiorespiratory fitness than typical AT in healthy individuals. However, the feasibility and effects of AT+BFR in individuals with T2D remain unclear. Objectives: This protocol describes the BOOST-HEALTH trial, which aims to 1) evaluate the feasibility of a 6-week AT+BFR intervention in adults with T2D, and 2) estimate preliminary effect sizes for changes in cardiorespiratory fitness, glycemic outcomes, and quality of life compared with standard care AT (AT- stdCare). Methods: BOOST-HEALTH (NCT07196371) is a single-blinded, multisite, randomized clinical pilot trial with two parallel treatment arms. Sixty adults with T2D (n = 30 female) will be randomized to 6 weeks of AT+BFR or AT-stdCare. Both groups will complete supervised treadmill walking three times per week (96 min/week) at 40–50% heart rate reserve. The AT+BFR group will exercise with BFR cuffs inflated to 60–80% of limb arterial occlusion pressure, whereas the AT-stdCare group will exercise without BFR. Primary outcomes will assess feasibility, including recruitment, enrollment, adherence, and retention. Secondary outcomes will estimate effect sizes for changes in cardiorespiratory fitness (VO _2max ) and continuous glucose monitoring metrics to inform outcome selection and sample size calculations for future definitive trials. Outcomes will be assessed at baseline and post-intervention. Discussion: Results of this study could establish BFR training as a novel therapeutic modality to augment the effects of exercise in individuals with T2D. Findings will inform whether a larger, definitive efficacy trial is warranted and will guide exercise professionals on the potential integration of AT+BFR as an alternative strategy to enhance the benefits of exercise in this population.

Introduction: Exercise is a cornerstone of type 2 diabetes (T2DM) management, yet individuals exhibit vast inter-individual variability in glycemic response to interventions. Gut microbial diversity and exercise intensity may be factors influencing this response variability. However, the interplay between exercise intensity, microbial adaptations, and glycemic outcomes in individuals living with T2DM remains unclear. Objectives: The purpose of this protocol is to describe the GUTFIT study, which aims to test whether performing vigorous-intensity combined aerobic and resistance training produces greater changes in glycemia and gut microbial diversity than moderate-intensity training in individuals living with T2DM. A secondary objective is to explore whether decreases in glycemia after exercise are associated with alterations in gut microbial community architecture and diversity. Methods: The GUTFIT Study (NCT06268743) is a parallel-group, single-blinded, randomized trial involving 40 adult participants (n = 20 female) living with T2DM. Participants will be randomized to 16 weeks of: 1) vigorous-intensity exercise (aerobic training at 70–80% heart rate reserve and resistance training at 8–10 repetitions of 75–80% maximal strength) or 2) moderate-intensity exercise (aerobic training at 45–55% heart rate reserve and resistance training at 12–15 repetitions of 65–70% maximal strength). Glycemia will be measured via glycated hemoglobin (HbA1c), and gut microbial composition will be determined in participant fecal samples using next-generation sequencing (Illumina MiSeq) of 16S ribosomal DNA genes. All outcome measures will be tested pre- and post-intervention. Discussion: Results of this study will provide further insight into the role of exercise intensity in changes in glycemia and the gut microbiome, and whether there is an intensity-dependent association between exercise-induced changes in glycemia and gut microbial diversity in individuals living with T2DM.

Data suggest that skeletal muscles have an internal clock that dictates training‐related adaptations, which could generate different health benefits in response to exercise timing. However, limited data exist on the impact of blood flow restriction (BFR) training timing on health outcomes. To investigate the impact of 6 weeks of BFR training performed at different times of day on body composition, performance measures, and irisin and PGC1‐α4 expression. Participants ( n = 31; aged 19–30) who performed 6 weeks of BFR resistance training were categorized into morning ( n = 16; 05:00–11:00) or afternoon ( n = 15; 11:00–17:00) groups. A sub‐analysis of responders and non‐responders (top and bottom 25% of muscle strength or lean mass change) was performed. Primary outcomes were changes in body composition, muscle strength, isokinetic measures, and irisin and PGC1‐α4 expression. Time effects were observed for changes in lean mass ( p < 0.001), relative lean mass ( p < 0.001), body fat percentage ( p = 0.02), and all performance measures ( p s ≤ 0.015). A negative correlation was observed between lean mass change and irisin change ( r = −0.18; p = 0.57). No group or time × group interactions were reported for any outcomes. Six weeks of BFR training provided improvements in body composition and performance outcomes and no changes in irisin and PGC1‐α4 irrespective of timing.

The primary objective was to test the influence of age on lean body mass (LBM), muscle strength, and isokinetic performance adaptation following a 6-week blood-flow restriction training (BFRT) intervention. A total of 38 young adults (23.5±3.1) and 34 older adults (72.7±5.5) completed a 6-week BFRT program. Exercises were performed three times per week at 30% of 1-repetition maximums (1-RMs) and 60% of each limb’s arterial occlusion pressure. Body composition was assessed using dual-energy X-ray absorptiometry, muscle strength was measured using 1-RMs, and muscular performance was measured using an isokinetic dynamometer. A significant increase in LBM was observed in young adults (0.9±1.5kg; p0.05) following the intervention. Both age groups significantly improved 1-RMs for knee extension, knee flexion, and chest press, with the young group displaying greater improvements (all ps<0.001). A significant increase in knee flexion torque and power was observed in young adults (all ps<0.001) but not in older adults, while a significant difference between groups was observed (p<0.05). The results from our study suggest that young adults improve LBM and muscle performance following 6-weeks of BFRT, while older adults enhance performance, despite a lack of improvement in LBM. Clinicaltrials.gov ID: NCT05615831.

Blood flow restriction training (BFRT) has been previously studied as an alternative form of resistance training to gain lean mass and improve performance outcomes. However, in all exercise studies of BFRT, the proportion of female participants represents only 17–29% of all research participants. This highlights a strong underrepresentation of females and the need for more knowledge on the impact of BFRT and sex differences. The primary objective was to compare the impact of 6-week BFRT on lean mass, strength, and performance outcomes between males and females. A total of 38 adults [age, 25.3 ± 3.1 years; female, n = 19 (50%)] performed whole-body resistance training program with blood flow restriction three times per week. Exercises were performed at 30% of 1-repetition maximum (1-RM) and blood flow restriction cuffs were set to 60% of each individual’s limb occlusion pressure. Body composition was assessed via dual-energy x-ray absorptiometry and strength was measured using 1-RM. A significant increase in lean mass was observed in males (p = 0.009) and females (p = 0.023) with no difference in the change between groups (p = 0.279). Both males and females increased 1-RM for upper- and lower-body exercises, with significant interaction effects (time x sex) for chest press (p = 0.003), seated row (p = 0.038), knee flexion (p = 0.043), and knee extension (p = 0.035), suggesting males increased 1-RM more for these exercises. Furthermore, peak power was improved in males (p < 0.001) and females (p = 0.002) during a vertical squat jump, but a significant interaction (time x sex) effect was observed (p = 0.039), suggesting males increased to a greater extent. Males and females significantly increased lean body mass, to a similar degree, following six weeks of resistance training in combination with blood flow restriction. Likewise, both males and females improved muscle strength following 6-week BFRT, however males may improve strength to a greater extent than females.

Irisin, an adipo-myokine, is positively associated with cardiorespiratory fitness and negatively associated with type 2 diabetes mellitus (T2DM). However, it is unclear if individuals with longer or shorter durations of T2DM express the same irisin levels following exercise. The objective of this study is to investigate the impact of 28 weeks of moderate-to-vigorous intensity aerobic exercise on irisin levels in individuals with short- and long-duration T2DM. This secondary analysis included participants ( n = 34) aged ≥ 19 years old with T2DM who completed 28 weeks of aerobic exercise training for 150 min per week at a moderate-to-vigorous intensity—16 weeks at a moderate intensity (4.5 metabolic equivalents of tasks (METs)) and then randomized to 12 weeks of maintained-intensity (4.5 METs) or increased-intensity (6.0 METs) aerobic exercise. Participants were categorized into two groups: (1) short-duration T2DM ( 0.05) in the maintained-intensity groups of short and long duration. The results of this analysis suggest that 28 weeks of moderate-to-vigorous intensity aerobic exercise differently impacted plasma irisin in individuals with short- or long-duration T2DM. The Improving Individual Glycemic Response with Exercise Intensity (INTENSITY) study was registered at clinicaltrials.gov (NCT03787836).

Objectives: To investigate the impact of a supervised blood-flow restriction (BFR) training program performed at different times of the morning on body composition and muscle performance in older, inactive adults. Methods: A single-arm intervention of supervised BFR resistance training was performed three times per week for six weeks. Participants (n=24; aged 65+ years) were categorized into early morning (n=13; 05:00–08:59) or late morning (n=11; 09:00–12:00) groups. Primary outcomes were changes in body composition, total work, average peak power, average peak torque, muscle strength, and physical function. Results: Mixed model analysis of variance revealed a significant within-subject effect of time for all strength measures (p ranging from 0.017 to <0.001) and some physical function measures including the 30 s chair stand test, 30 s bicep curl test, and grip strength (p ranging from 0.015 to <0.001). No between-group or time by group interaction effect was observed for all outcomes. Conclusions: This study showed that only six weeks of BFR training, performed at different time of the morning, did not enhance muscle mass and performance, but provided similar changes in muscle strength and some physical function tests in older adults.

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-overweight/obese (non-OW/OB) (BMI: 22.2 ± 1.5 kg/m²) and 26 overweight/obese (OW/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. OW/OB displayed a significantly lower level of circulating irisin and protein expression compared to non-OW/OB ( p < 0.01). Insulin sensitivity was positively correlated with irisin release during MICT and HIIT in non-OW/OB (all p < 0.05), but not in OW/OB. Regarding irisin expression, non-OW/OB with high Si had a 2.03-fold ( p < 0.05) increase during HIIT, while OW/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. OW/OB individuals have a blunted irisin response to acute exercise and lower baseline irisin concentrations compared to non-OW/OB individuals. Although exercise stimulates irisin release in non-OW/OB individuals, only a greater exercise intensity stimulates irisin release in OW/OB individuals. These findings are clinically relevant, as irisin is associated with greater insulin sensitivity. This trial was registered at clinicaltrials.gov (NCT03514238).

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.