The Release of Lipolytic Hormones during Various High-Intensity Interval and Moderate-Intensity Continuous Training Regimens and Their Effects on Fat Loss.

To investigate the release of lipolytic hormones during various high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), and their effects on fat loss. 39 young women categorized as obese (with a body fat percentage (BFP) ≥30%) were randomly allocated to one of the following groups: all-out sprint interval training (SIT, n =10); supramaximal HIIT (HIIT120, 120%V̇O2peak, n = 10); HIIT (HIIT90, 90%V̇O2peak, n = 10), or MICT, (60%V̇O2peak, n = 9) for a twelve-week observation period consisting of 3 to 4 exercise sessions per week. Serum epinephrine (EPI) and growth hormone (GH) were measured during the 1st, 20th, and 44th training sessions. Body weight (BW), body mass index (BMI), whole-body fat mass (FM) and BFP were assessed pre- and post-intervention. Following the 1st and 20th sessions, significant increases in EPI (p < 0.05) were observed post-exercise in HIIT120 and HIIT90, but not in SIT and MICT. In the 44th session, the increased EPI was found in SIT, HIIT120, and HIIT90, but not in MICT (p < 0.05). For the GH, a significant increase was observed post-exercise in all groups in the three sessions. The increased EPI and GH returned to baselines 3 hours post-exercise. After the 12-week intervention, significant reductions in FM and BFP were found in all groups, while reductions in BW and BMI were only found in the SIT and HIIT groups. Greater reductions in FM and BFP, in comparison to MICT, were observed in the SIT and HIIT groups (p < 0.05). 12-week SIT, HIIT120, and HIIT90, in comparison to MICT, were more efficacious in fat reduction in obese women, partly benefiting from the greater release of lipolytic hormones during training sessions.

Effects of High-Intensity Interval Training on the Parameters Related to Physical Fitness and Health of Older Adults: A Systematic Review and Meta-Analysis.

BACKGROUND: As a novel and time-efficient exercise form, high-intensity interval training (HIIT) has shown great potential in improving health-related physical fitness among diverse populations. However, empirical evidence on its efficacy among the elderly has not been well summarized. This systematic review and meta-analysis aimed to determine the effect of HIIT interventions on the parameters related to physical fitness and health of older adults, including resting heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), cardiorespiratory fitness (CRF), body mass index (BMI), body fat percent (BF%), waist circumference (WC), muscular endurance (ME), muscular strength (MS), muscular power (MP), balance and flexibility, compared to non-exercise and other-exercise (e.g., moderate-intensity continuous training, resistance training) conditions. METHODS: Literature published from January 2000 to May 2023 was collected through extensive searches across eight databases and relevant review papers. Randomized controlled trials (RCTs) featuring a minimum 2-week exercise intervention for older adults (≥ 60 years) were included. The pooled effect size of Hedges'g was estimated using random-effects models in R. Meta-regression was performed for both categorical (health status, duration of training programme, and frequency) and continuous moderators (mean age, male rate, and attrition rate). RESULTS: Forty-four eligible RCTs with 1863 participants (52.1% female; 60.5-81.2 years) were included in the quantitative analysis. Compared to non-exercise condition, HIIT significantly improved resting HR (g = -0.36, 95%CI = [-0.67, -0.05], P = 0.032), SBP (g = -0.29, 95%CI = [-0.54, -0.03], P = 0.008), CRF (g = 0.77, 95%CI = [0.51, 1.04], P < 0.001), BF% (g = -0.26, 95%CI = [-0.41, -0.11], P = 0.006), MS (g = 0.47, 95%CI = [0.23, 0.71], P = 0.004), ME (g = 0.65, 95%CI = [0.10, 1.19], P = 0.036), and balance (e.g., timed-up-and-go) (g = -0.79, 95%CI = [-1.19, -0.40], P = 0.035). Compared to other-exercise condition, HIIT significantly improved resting HR (g = -0.11, 95%CI = [-0.21, -0.01], P = 0.029), SBP (g = -0.14, 95%CI = [-0.28, -0.01], P = 0.038), and CRF (g = 0.23, 95%CI = [0.07, 0.38], P = 0.008). No significant difference was found between HIIT and non-exercise condition for DBP, BMI and WC, as well as between HIIT and other-exercise condition for DBP, BMI, BF%, WC, ME, and balance (all P > 0.05). Meta-regression indicated that mean age moderated the HIIT effect on resting HR (b = -0.02, P = 0.014; HIIT vs. other-exercise condition) and SBP (b = 0.03, P = 0.048; HIIT vs. non-exercise), and attrition rate moderated the effect on CRF (b = 0.03, P = 0.007; HIIT vs. non-exercise). CONCLUSION: This study supports the efficacy of HIIT in improving resting HR, SBP, CRF, BF%, MS, ME and balance among older adults. More empirical evidence is needed to determine the efficacy of HIIT for MP and flexibility in this population. TRIAL REGISTRATION: PROSPERO CRD42022316246.

The effects of high-intensity interval training/moderate-intensity continuous training on the inhibition of fat accumulation in rats fed a high-fat diet during training and detraining.

BACKGROUND: Compared with moderate-intensity continuous training (MICT), high-intensity interval training (HIIT) has at least a comparable effect on inhibiting an increase in fat. However, few studies have been conducted to examine the effects of detraining on body fat in rats fed a high-fat diet. The present study aimed to compare the effects of 10 weeks of HIIT or MICT as well as 6 weeks of detraining on body fat in rats fed a high-fat diet. METHODS: After being fed a high-fat diet for 8 weeks, 54 female rats were randomly assigned to six groups: (1) CON-10, sedentary control for 10 weeks; (2) MICT-10, 10 weeks of MICT; (3) HIIT-10, 10 weeks of HIIT; (4) CON-16, sedentary control for 16 weeks; (5) MICT-16, 10 weeks of MICT followed by 6 weeks of training cessation; and (6) HIIT-16, 10 weeks of HIIT followed by 6 weeks of training cessation. The training was performed 5 days/week. The subcutaneous adipose tissue (inguinal; SCAT), visceral adipose tissue (periuterine; VAT) and serum lipid profile were analysed after 10 or 16 weeks. Adipose tissue triglyceride lipase (ATGL) protein expression in VAT was assessed by western blotting. RESULTS: HIIT-10 and MICT-10 prevented the increase in SCAT, VAT and serum lipid levels seen in the CON group. During the 6-week detraining period, HIIT continued to prevent the increase in adipose tissue mass observed in the CON group, whereas MICT at least maintained this inhibition. The inhibition of fat mass increase was mainly the result of preventing adipocyte hypertrophy. The HIIT-10 and HIIT-16 groups showed the highest ATGL protein expression. CONCLUSIONS: HIIT has a comparable effect to MICT on inhibiting fat accumulation in female rats; however, the inhibition of SCAT and VAT increase by HIIT is superior to MICT after short-term training cessation.

High-intensity interval training elicits more enjoyment and positive affective valence than moderate-intensity training over a 12-week intervention in overweight young women.

Background: The purpose of this study was to compare the differences in enjoyment and affect in response to four weight control intervention protocols over 12 weeks. Methods: Sixty overweight young females were randomised into four intervention groups: repeated sprint training (RST, 6-sec all-out sprint interspersed with 9-sec rest), high-intensity interval training (HIIT) with short interval (HIIT120, 1-min effort at 120% V̇O2peak) and long interval (HIIT90, 4-min effort at 90% V̇O2peak), and moderate-intensity continuous training (MICT, 60% V̇O2peak) by cycling over 12 weeks. The total workload in each training session in HIIT120, HIIT90, and MICT was confined to 200 kJ, while it was lower in RST with 57 ± 4 kJ. Enjoyment (Physical Activity Enjoyment Scale, PACES) and affective valence (Feeling Scale, FS) were measured throughout the intervention. Results: The score of the PACES on average over 12 weeks showed a significant between-group effect that was lower in MICT (80.8 ± 11.8) compared with HIIT120 (92.5 ± 11.4) and HIIT90 (96.8 ± 13.9) (p < 0.05). In the 8th week, enjoyment was scored higher in two HIITs compared with MICT. In the 12th week, HIITs and RST were more enjoyable than MICT, where two HIITs were better than RST. The score of FS showed a significant between-group effect that was higher in HIIT90 (1.5 ± 1.4) compared with HIIT120 (0.2 ± 1.2) (p < 0.05), but a non-significant time or group-by-time interaction effect. A significant weight loss occurred in three interval training protocols (p < 0.05), but not in MICT. The V̇O2peak significantly increased in four groups without between-group difference. Conclusion: Interval training, especially the long-interval type, is an enjoyable and pleasant long-term exercise intervention for overweight young women. RST could be an alternative for weight control considering its time efficiency with comparable enjoyment and overall pleasure.

Comparison of visceral fat lipolysis adaptation to high-intensity interval training in obesity-prone and obesity-resistant rats.

BACKGROUND/OBJECTIVES: Visceral obesity is one of the key features of metabolic syndrome. High-intensity interval training (HIIT) could effectively reduce visceral fat, but its effects show strong heterogeneity in populations with different degrees of obesity. The mechanism may be related to the differential adaptation to training between obesity phenotypes, namely obesity prone (OP) and obesity resistant (OR). The aim of the present study was to compare adaptive changes of visceral adipose lipolysis adaptation to HIIT between OP and OR animals and further explore the upstream pathway. METHODS: OP and OR Sprague Dawley rats were established after feeding a high-fat diet for 6 weeks; they were then divided into HIIT (H-OP and H-OR) and control (C-OP and C-OR) groups. After 12 weeks of HIIT or a sedentary lifestyle, animals were fasted for 12 h and then sacrificed for histology as well as gene and protein analysis. Visceral adipocytes were isolated without fasting for catecholamine stimulation and ß3-adrenergic receptor (ß3-AR) blockade in vitro to evaluate the role of upstream pathways. RESULTS: After training, there were no differences in weight loss or food intake between OP and OR rats (P > 0.05). However, the visceral fat mass, adipocyte volume, serum triglycerides and liver lipids of OP rats decreased by more than those of OR rats (P < 0.05). Meanwhile, the cell lipolytic capacity and the increase in the expression of ß3-AR were higher in the OP compared with OR groups (P < 0.05). Although training did not increase sympathetic nervous system activity (P > 0.05), the cell sensitivity to catecholamine increased significantly in the OP compared with OR groups (P < 0.05). Following blocking ß3-AR, the increased sensitivity disappeared. CONCLUSION: With HIIT, OP rats lost more visceral fat than OR rats, which was related to stronger adaptive changes in lipolysis. Increased ß3-AR expression mediated this adaptation.

Assessment of graphene oxide toxicity on the growth and nutrient levels of white clover (Trifolium repens L.).

Carbon nanomaterials (CNMs) are novel engineered nanomaterials and have been used widely. Their toxic effects on terrestrial plants in soil matrix require careful investigation. In this study, white clover (Trifolium repens L.) was grown in a potted soil with graphene oxide (GO) at levels of 0.2%, 0.4% and 0.6% and the effects of GO on the growth and nutrient uptake of white clover were evaluated after 50 and 100 days of exposure. GO exposure showed adverse effects on seedling growth, photosynthetic parameters and nutrient uptake in shoots, and the effect was more significant with increasing concentration and exposure time. Compared with the control, GO at the highest level of 0.6% decreased plant height, leaf and stem dry weights, total chlorophyll content and net photosynthetic rate by 43.7%, 45.7%, 43.4%, 32% and 85.7%, respectively, after 100 d of exposure, and N, K, Cu, Zn, Fe, Mo, B, Si contents decreased by 19.5%, 20.1%, 12.6%, 25.0%, 12.9%, 26.0%, 18.9%, 23.0%, respectively. Furthermore, the electrolyte leakage, lipid peroxidation, reactive oxygen species, antioxidant enzyme activities were all increased by GO, especially at high dose and long exposure. These results indicate that GO can suppress plant growth by oxidative stress, photosynthesis inhibition, and nutrient imbalance.

Effects of descending or ascending stair exercise on body composition, insulin sensitivity, and inflammatory markers in young Chinese women with obesity: A randomized controlled trial.

We examined the effects of descending (DSE) or ascending (ASE) stair exercise on body composition, insulin sensitivity, and inflammatory markers in young Chinese women with obesity. Thirty-six participants were randomly assigned into three groups DSE, ASE and a control group. The DSE and ASE groups performed three sessions of stair walking per week for 12 weeks with a gradual increase in repetitions. Following the exercise interventions, body composition related variables obtained by Dual-energy X-ray absorptiometry scans significantly decreased. Abdominal fat decreased in the DSE group only. Moreover, Insulin sensitivity improved significantly 3.5-fold in the DSE group compared with ASE group (insulin: -33.2% vs. -9.8%, homoeostasis model assessment for insulin resistance: -35.6% vs. -10.8%). Pro-inflammatory factors showed significant decreases in tumour necrosis factor-α (TNF-α) (-39.9% vs. -23.2%) for both intervention groups. The reduction in TNF-α concentrations in the DSE group was significantly different compared to the other two groups. Interleukin-6 significantly decreased in both exercise protocols. Our results show that 12-weeks induced stair walking improved body composition parameters in Chinese females with obesity. The results also demonstrate the superiority of the DSE protocol for improving insulin sensitivity. These findings may be attributable to the decreases observed in TNF- α levels.

Impact of High-intensity Interval Exercise and Moderate-Intensity Continuous Exercise on the Cardiac Troponin T Level at an Early Stage of Training.

An elevation in cardiac troponin T (cTnT), as a highly specific biomarker of cardiomyocyte damage, after moderate-intensity continuous exercise (MCE) has been described. The exercise-induced cTnT response distorts the diagnostic role of the cTnT assay. Although high-intensity interval exercise (HIE) is growing in popularity and concerns remain about its safety, available data related to cTnT release after HIE is limited, which hampers the use of HIE as a health intervention. Here, we present three representative HIE protocols [traditional HIE (repeated 4 min cycling at 90% V̇O2max interspersed with 3 min rest, 200 kJ/session); sprint interval exercise (SIE, repeated 1 min cycling at 120% V̇O2max interspersed with 1.5 min rest, 200 kJ/session); and repeated sprint exercise (RSE, 40 x 6 s all-out sprints interspersed with 9 s rest)] and one representative MCE protocol (continuous cycling exercise at an intensity of 60% V̇O2max, 200 kJ/session). Forty-seven sedentary, overweight young women were randomly assigned to one of four groups (HIE, SIE, RSE, and MCE). Six bouts of respective exercise were performed by every single group, with each being 48 h apart. Meanwhile, for four groups, the duration of the entire testing period was identical, being 10 days. Before and after the first and final exercise bouts, an assessment was conducted of cTnT. The current study provides a frame of reference giving a clear picture of how a specific exercise session affects the circulating cTnT concentration at the early stage of training. The information may assist with clinical interpretations of post-exercise cTnT elevation and guide the prescription of exercise, especially for HIE.

The cTnT response to acute exercise at the onset of an endurance training program: evidence of exercise preconditioning?

PURPOSE: Exercise induces a cardioprotective effect referred to as "preconditioning". Whether the preconditioning impacts upon the cardiac troponin T (cTnT) response to subsequent exercise bouts is unclear. This study investigated the effects of an initial exercise bout, a second exercise bout 48 h later, as well as subsequent exercise every 48 h for 4 days or a single identical exercise bout after 8 days of inactivity gap on cTnT response to acute exercise. METHODS: Twenty-eight sedentary overweight young women were randomly assigned to either six bouts of exercise each separated by 48 h or three bouts of exercise with 48 h between the first two bouts and 8 days between the second and third bouts. All exercise bouts were identical (60% [Formula: see text], 200 kJ) and the total testing period (10 days) was the same for both groups. cTnT was assessed before and after the 1st, 2nd, and final exercise bouts. RESULTS: cTnT increased (129%, P < 0.05) after the first bout of exercise in both groups (peak post-exercise cTnT, median [range], ng l-1: 3.43[< 3.00-27.26]) with no between-group differences in the response. The second exercise bout had no significant (P > 0.05) effect on post-exercise cTnT (< 3.00[< 3.00-21.96]). The final exercise bout resulted in an increase (190%, P < 0.05) in cTnT (4.35[< 3.00-13.05]) in both groups. CONCLUSIONS: A single bout exercise resulted in a temporary blunting of cTnT response to acute exercise 48 h later. The effect of exercise preconditioning was not preserved, regardless of whether followed by repeated exercise every 48 h or a cessation of exercise for 8 days.