Article

The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. International Journal of Obesity, 32(4), 684-691

Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
International journal of obesity (2005) (Impact Factor: 5). 04/2008; 32(4):684-91. DOI: 10.1038/sj.ijo.0803781
Source: PubMed

ABSTRACT

To determine the effects of a 15-week high-intensity intermittent exercise (HIIE) program on subcutaneous and trunk fat and insulin resistance of young women.
Subjects were randomly assigned to one of the three groups: HIIE (n=15), steady-state exercise (SSE; n=15) or control (CONT; n=15). HIIE and SSE groups underwent a 15-week exercise intervention.
Forty-five women with a mean BMI of 23.2+/-2.0 kg m(-2) and age of 20.2+/-2.0 years.
Both exercise groups demonstrated a significant improvement (P<0.05) in cardiovascular fitness. However, only the HIIE group had a significant reduction in total body mass (TBM), fat mass (FM), trunk fat and fasting plasma insulin levels. There was significant fat loss (P<0.05) in legs compared to arms in the HIIE group only. Lean compared to overweight women lost less fat after HIIE. Decreases in leptin concentrations were negatively correlated with increases in VO(2peak) (r=-0.57, P<0.05) and positively correlated with decreases in TBM (r=0.47; P<0.0001). There was no significant change in adiponectin levels after training.
HIIE three times per week for 15 weeks compared to the same frequency of SSE exercise was associated with significant reductions in total body fat, subcutaneous leg and trunk fat, and insulin resistance in young women.

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Available from: Ethlyn Gail Trapp
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    • "This finding contradicts the general pattern of findings in the literature, in which HIIT is shown to be more effective for reducing total body mass as well as percentages of android fat (Boutcher 2011). One potential source of this disparity could be the difference in HIIT and ET protocols used this study compared to previous research, as our moderate ET was more intense (~75 % V V O 2max ) than the steady-state exercise protocols previously used (60 % VO 2max ) (Trapp et al. 2008). Another potential factor is altered dietary habits of the participants Although the participants were instructed to maintain their normal diets and none reported any notable dietary changes over the course of the study, diet was self-reported and not controlled directly by the researchers. "
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    ABSTRACT: Purpose: The goal of this study was to compare the effect of work- and duration-matched interval training (HIIT) versus moderate aerobic endurance training (ET) on acute and chronic inflammation, along with changes in the lipid profile, to determine which may be more beneficial for improving cardiovascular health. Methods: Twelve sedentary males (maximal oxygen consumption = 41.6 ± 5.4 mL kg(-1) min(-1)) completed 8 weeks of aerobic interval training or moderate aerobic training, with variables including C-reactive protein (CRP) for chronic inflammation, interleukin-6 (IL-6) response for the acute inflammatory response, plasma concentrations of high-density lipoprotein (HDL), total cholesterol (TC), triglycerides (TRG), and low-density lipoprotein, and body composition measured before and after the training period. Results: HIIT decreased plasma TRG from 92 ± 32 to 61 ± 12 mg dL(-1), which was significantly different from ET, while ET improved the TC:HDL ratio from 4.67 ± 0.85 to 4.07 ± 0.96 and reduced the percentage of android fat from 36.78 ± 9.60 to 34.18 ± 11.39 %. Neither training protocol resulted in an acute IL-6 response on the first nor the last day of exercise, a change in chronic levels of CRP, or a significant increase in HDL, despite previous research finding these changes. Conclusions: It seems that in order to maximize the health outcomes from physical activity, both HIIT and ET should be included. The acute inflammatory response and reductions in chronic inflammation resulting from exercise training may not be as common as the literature suggests.
    Full-text · Article · Dec 2015 · Arbeitsphysiologie
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    • "It is also well known, that resistance training may improve the muscle insulin sensitivity and β-cell function in obese patients (Croymans et al. 2013). HIIE three times per week for 15 weeks compared to the same frequency of steady-state exercise was associated with significant reductions in total body fat, subcutaneous leg and trunk fat, and insulin resistance in young women (Trapp et al. 2008). A 35% rise in glucagon concentration was positively correlated with the exercise intensity increase (Galbo et al. 1975). "
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    ABSTRACT: Obesity management for achieving an effective weight loss includes dietary modification and exercise [resistance (strength), endurance (cardiovascular) or intervals training (high-intensity intermittent exercise)]. Regular exercise acutely increases fat oxidation, which induces loss of fat mass and increases energy expenditure. Moreover, it has a positive effect on the physical (improved insulin sensitivity, lipid profile, etc.) and mental health (mood, cognition, memory, sleep, etc.). Endocrine responses to muscle actions are affected by many factors, including the exercise muscle groups (lower and upper body), load/volume, time-under tension, and rest-period intervals between sets, training status, gender, and age. The aim of this review is to summarize, evaluate, and clarify the literature data focusing on the endocrine responses to different types of exercise, including the frequency, intensity, and type of movement with regard to the fat loss strategies. Many studies have investigated anabolic [growth hormone, insulin-like growth factor-1 (IGF-1), testosterone] and gluco- and appetite- regulatory (insulin, cortisol, ghrelin) hormone responses and adaptations of skeletal muscles to exercise. Muscle tissue is a critical endocrine organ, playing important role in the regulation of several physiological and metabolic events. Moreover, we are also describing the response of some other substances to exercise, such as myokines [irisin, apelin, brain-derived neurotrophic factor (BDNF), myostatin, and fibroblast growth factor 21 (FGF21)]. It is proposed that reducing intra-abdominal fat mass and increasing cardiorespiratory fitness through improving nutritional quality, reducing sedentary behavior, and increase the participation in physical activity/exercise, might be associated with clinical benefits, sometimes even in the absence of weight loss.
    Full-text · Article · Aug 2015 · Endocrine regulations
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    • "Furthermore, we demonstrated that EPOC is significantly greater following 10 min of REHIT compared to 30 min of moderate intensity aerobic exercise. These findings are of importance as several previous studies have observed reductions in fat mass following HIT with some evidence for superior reductions compared with traditional aerobic training (Whyte et al. 2010; Gillen et al. 2013; Heydari et al. 2012; Trapp et al. 2008). Since direct exercise energy expenditure is much lower with HIT compared with aerobic exercise, the (potentially superior) reductions in fat mass following HIT have been hypothesised to be a result of either an increase in energy expenditure through a more prolonged EPOC and/or a reduction in energy intake through suppression of appetite (Boutcher 2011). "
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    ABSTRACT: Purpose We have previously shown that 6 weeks of reduced-exertion high-intensity interval training (REHIT) improves V˙O2max in sedentary men and women and insulin sensitivity in men. Here, we present two studies examining the acute physiological and molecular responses to REHIT. Methods In Study 1, five men and six women (age: 26 ± 7 year, BMI: 23 ± 3 kg m−2, V˙O2max: 51 ± 11 ml kg−1 min−1) performed a single 10-min REHIT cycling session (60 W and two 20-s ‘all-out’ sprints), with vastus lateralis biopsies taken before and 0, 30, and 180 min post-exercise for analysis of glycogen content, phosphorylation of AMPK, p38 MAPK and ACC, and gene expression of PGC1α and GLUT4. In Study 2, eight men (21 ± 2 year; 25 ± 4 kg·m−2; 39 ± 10 ml kg−1 min−1) performed three trials (REHIT, 30-min cycling at 50 % of V˙O2max, and a resting control condition) in a randomised cross-over design. Expired air, venous blood samples, and subjective measures of appetite and fatigue were collected before and 0, 15, 30, and 90 min post-exercise. Results Acutely, REHIT was associated with a decrease in muscle glycogen, increased ACC phosphorylation, and activation of PGC1α. When compared to aerobic exercise, changes in V˙O2, RER, plasma volume, and plasma lactate and ghrelin were significantly more pronounced with REHIT, whereas plasma glucose, NEFAs, PYY, and measures of appetite were unaffected. Conclusions Collectively, these data demonstrate that REHIT is associated with a pronounced disturbance of physiological homeostasis and associated activation of signalling pathways, which together may help explain previously observed adaptations once considered exclusive to aerobic exercise.
    Full-text · Article · Jul 2015 · Arbeitsphysiologie
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