Effects Of High-intensity Intermittent Exercise Research Articles

Effects of High-Intensity Intermittent Training on Metabolic Parameters and Irisin Levels in High-Fat-Fed Rats

Objective: To investigate the effects of high-intensity intermittent training (HIIT) on preventing significant weight gain and provide scientific theoretical support and practical guidance for reducing the occurrence of obesity. Methods: Twenty-four Sprague-Dawley rats were randomly divided into four groups: the control sedentary group (CS), the high-fat sedentary group (HS), the high-fat continuous exercise group (HE), and the high-fat intermittent exercise group (HI). The HE and HI groups underwent five days of continuous low-intensity exercise and eight weeks of high-intensity intermittent exercise. Weekly monitoring included measurements of food intake and body weight. An automatic biochemical analyzer was used to assess blood lipid and glucose levels, while ELISA kits measured serum insulin and irisin content. H&E staining was used to observe adipocyte size. Results: In the HS group, body weight, blood lipid levels, blood glucose levels, and adipocyte size significantly increased, while the QUICKI index decreased. In the HI group, body weight, blood lipid levels, blood glucose levels, and adipocyte size decreased, and the QUICKI index increased. The effects of high-intensity intermittent exercise were superior to those of continuous low-intensity exercise. In the HI group, serum irisin levels did not change significantly after exercise, while in the HE group, there was a slight upward trend in irisin levels. Conclusion: A high-fat diet induced abnormal metabolism in rats. HIIT effectively prevents metabolic abnormalities induced by a high-fat diet, and its effects are more pronounced than those of low-intensity exercise. HIIT stimulates the secretion of blood irisin, affecting secretion levels, and may represent a novel mechanism for maintaining metabolic homeostasis. This has important implications for controlling significant weight gain.

High-intensity intermittent exercise increases serum levels of chitinase 3-like protein-1 and matrix metalloproteinase-9 in persons with multiple sclerosis

The study aimed to evaluate the effect of high-intensity intermittent exercise (HIIE) on serum levels of MMP-9 and CHI3L1 in multiple sclerosis. Study group received HIIE twice a week for 12 weeks, while control group received no treatment. In intra-group comparison, study group showed a significant increase in MMP-9 and CHI3L1 levels, while control group showed no significant difference. In intergroup comparison, a significant difference was found only in CHI3L1 levels after treatment. The increase in MMP-9 and CH3L-1 concentrations in study group suggests that these biomarkers may play a role in regulating specific skeletal muscle adaptations due to HIIE.

Effects of high-intensity intermittent exercise versus moderate-intensity continuous exercise on renal hemodynamics assessed by ultrasound echo.

High-intensity intermittent exercise (HIIE) has become attractive for presenting a variety of exercise conditions. However, the effects of HIIE on renal function and hemodynamics remain unclear. This study aimed to compare the effects of HIIE and moderate-intensity continuous exercise (MICE) on renal hemodynamics, renal function, and kidney injury biomarkers. Ten adult males participated in this study. We allowed the participants to perform HIIE or MICE to consider the impact of exercise on renal hemodynamics under both conditions. Renal hemodynamic assessment and blood sampling were conducted before the exercise (pre) and immediately (post 0), 30 min (post 30), and 60 min (post 60) after the exercise. Urine sampling was conducted in the pre, post 0, and post 60 phases. There was no condition-by-time interaction (p = 0.614), condition (p = 0.422), or time effect (p = 0.114) regarding renal blood flow. Creatinine-corrected urinary neutrophil gelatinase-associated lipocalin concentrations increased at post 60 (p = 0.017), but none exceeded the cut-off values for defining kidney injury. Moreover, there were no significant changes in other kidney injury biomarkers at any point. These findings suggest that high-intensity exercise can be performed without decreased RBF or increased kidney injury risk when conducted intermittently for short periods.

540-P: Meta-analysis of Blood Glucose Response to High Intensity Exercise in Adults with Type 1 Diabetes

Background: High intensity exercise-induced hyperglycemia is recognized in T1D clinical guidelines, but its occurrence after high intensity intermittent exercise (HIIE) in acute studies is inconsistent. This meta-analysis aimed to examine the available evidence of BG responses to HIIE in adults with T1D. The secondary aim was to assess the role of prandial status (fasted/fed) , sex (by percentage of female participants ≤ 50, or > 50) , mean age, fitness (VO2peak) , interval duration, and total exercise duration on BG outcomes. We hypothesized that there would be no consistent effect on BG from HIIE, unless examined in the context of participant prandial status. Methods: We conducted a literature search using keywords related to T1D and HIIE. Studies were required to have a minimum of 6 participants with T1D aged ≥17 years, involving a HIIE intervention, and a pre- and post-exercise measure of BG to be included. Analyses were performed using a general inverse variance statistical method with a random effects model on RevMan5® statistical software and a weighted multiple regression on STATA17® statistical software. Results: Seventeen interventions from 13 studies were included in the final analysis. A mean overall BG change of -1.4 mmol/L (-3.0, 0.2) was found during exercise albeit with high heterogeneity (I2= 92%) . Fasted exercise increased BG by +1.7 mmol/L (-0.2, 3.6) , while fed exercise decreased BG by -2.6 mmol/L (3.7, -1.5) , with a statistically significant difference between groups (p<0.001) . There were no significant effects from sex (p=0.74) , fitness (p=0.46) , age (p=0.89) , interval duration (p=0.25) or exercise duration (p=0.38) . Conclusions: The effect of HIIE on BG is inconsistent, but partially explained by prandial status. Disclosure R.Mcclure: None. E.Weseen: None. F.Alcántara cordero: None. M.Maldaner: None. S.Hart: None. N.G.Boulé: None. J.E.Yardley: Research Support; Abbott, Dexcom, Inc., LifeScan, Speaker's Bureau; Abbott Diabetes.

Effects of high-intensity intermittent exercise on the contractile properties of human type I and type II skeletal muscle fibers.

In vitro studies have shown that alterations in redox state can cause a range of opposing effects on the properties of the contractile apparatus in skeletal muscle fibers. To test whether and how redox changes occurring in vivo affect the contractile properties, vastus lateralis muscle fibers from seven healthy young adults were examined at rest (PRE) and following (POST) high-intensity intermittent cycling exercise. Individual mechanically skinned muscle fibers were exposed to heavily buffered solutions at progressively higher free [Ca2+] to determine their force-Ca2+ relationship. Following acute exercise, Ca2+ sensitivity was significantly decreased in type I fibers (by 0.06 pCa unit) but not in type II fibers (0.01 pCa unit). Specific force decreased after the exercise in type II fibers (-18%) but was unchanged in type I fibers. Treatment with the reducing agent dithiothreitol (DTT) caused a small decrease in Ca2+-sensitivity in type II fibers at PRE (by ∼0.014 pCa units) and a significantly larger decrease at POST (∼0.035 pCa units), indicating that the exercise had increased S-glutathionylation of fast troponin I. DTT treatment also increased specific force (by ∼4%), but only at POST. In contrast, DTT treatment had no effect on either parameter in type I fibers at either PRE or POST. In type I fibers, the decreased Ca2+ sensitivity was not due to reversible oxidative changes and may have contributed to a decrease in power production during vigorous exercises. In type II fibers, exercise-induced redox changes help counter the decline in Ca2+-sensitivity while causing a small decline in maximum force.NEW & NOTEWORTHY This study identified important cellular changes occurring in human skeletal muscle fibers following high-intensity intermittent exercise: 1) a decrease in contractile apparatus Ca2+ sensitivity in type I but not type II fibers, 2) a decrease in specific force only in type II muscle fibers, and 3) a redox-dependent increase in Ca2+ sensitivity occurring only in type II fibers, which would help maintain muscle performance by countering the normal metabolite-induced decline in Ca2+ sensitivity.

Short-Time β-Alanine Supplementation on the Acute Strength Performance after High-Intensity Intermittent Exercise in Recreationally Trained Men.

(1) Background: We investigated the effects of 28 days of beta-alanine (β-alanine) supplementation on the acute interference effect of high-intensity intermittent exercise (HIIE) on lower-body resistance exercise performance, body composition, and strength when combined with a resistance training program. (2) Methods: Twenty-two males were randomized into: β-alanine supplementation (6.4 g/day) or placebo (6.4 g/day maltodextrin) during 28 days. Total body water, intracellular and extracellular water, fat-free mass (FFM), and fat mass were assessed using bioelectrical impedance. Participants performed 5000-m HIIE (1:1 effort and rest ratio) followed by resistance exercise (four sets of 80% at 45° leg press until muscular failure) at baseline and after 28 days. The resistance training program consisted of three sets of 10 to 12 RM with 90 s of rest, four days per week. (3) Results: For the post-HIIE leg press volume, higher values were observed post-training than pre-training, but no group x time interaction was observed. There was a non-significant trend for an interaction in the FFM change (β-alanine = 2.8% versus placebo = 1.0%, p = 0.072). (4) Conclusion: Twenty-eight days of β-alanine supplementation did not prevent acute strength loss during resistance exercise after high-intensity interval exercise, nor increase strength or hypertrophic adaptations associated with resistance training.

Effect of high-intensity intermittent exercise on high-fat diet-induced hepatic fat deposition in C57BL/6 mice

40只5周龄C57BL/6雄性小鼠随机分为正常对照组（C，n = 10）及高脂饮食组，6周后对高脂饮食喂养小鼠进行随机分为高强度间歇运动组（HIIT，n = 10）、等时间的中等强度持续运动组（MICT，n = 10)和高脂饮食安静组（HF，n = 10）。 结果： 显示HIIT较MICT在治疗NAFLD方面更具优势，其中可能的机制是HIIT较MICT能够更加有效地减低肝脏脂肪酸的从头合成，增加肝细胞线粒体功能从而改善肝脏脂质沉积。.

The Effect of High-Intensity Intermittent Exercise on Chronic Stress and Potential Biomarkers: a Pilot Study

Persons employed in highly stressful occupations are at a heightened risk for developing chronic stress-related disorders. These disorders are associated with immunosuppression, disease progression and psychological illness. Exercise has previously been used to combat depression; however, police personnel are already moderately active yet still stressed. Therefore, this pilot study aims to determine if high-intensity intermittent training (HIIT) could be a potential stress-reducing strategy in already trained persons, and which biological markers could be measured in a larger study. Using three single case studies, this study employed a 10-week HIIT intervention and measured markers of stress via Perceived Stress Scale (PSS) scores, cortisol levels and associated inflammation blood markers at baseline and post-intervention. The PSS scores reduced after HIIT (36–40%). Cortisol secretion pre-intervention indicated a flat profile during daytime hours; post-intervention showed increased levels in the morning and an overall normal daytime profile. Of the inflammation blood markers, eosinophil cell counts were halved post-intervention. HIIT, therefore, is a potential stress-reducing strategy in already trained individuals. The decreased psychological stress was associated with normalization of cortisol hormone function and reduced systemic inflammation via lower eosinophil counts, which highlighted the specific physiological markers as indicators of chronic stress.

High-intensity intermittent exercise increases adenosine hydrolysis in platelets and lymphocytes and promotes platelet aggregation in futsal athletes

Acute bouts of high-intensity intermittent exercise (HIIE) or sports are associated with changes in lymphocytes and platelet functions and we hypothesized that the purinergic system is involved with these alterations. We investigated the activity of ectonucleotidases in platelets and lymphocytes as well as the platelet aggregation of futsal players in response to an acute protocol of HIIE. Thus, 19 male semi-professional futsal players were submitted to 40 min of HIIE on a treadmill. Blood samples were collected three-time points: before exercise, immediately after, and 30 min after the end of the session. Platelet-rich plasma (PRP) and lymphocytes were isolated. ATP, ADP, AMP, and adenosine hydrolysis, NTPDase1 (CD39) expression as well as platelet aggregation were measured. Our results showed HIIE induced a decrease in ATP and ADP hydrolysis in platelets, an increase in adenosine hydrolysis and an increase in platelet aggregation immediately after exercise. After 30 min of recovery, enzymatic activity and platelet aggregation returned to baseline levels. In lymphocytes, adenosine hydrolysis was augmented immediately after exercise and remained increased even after 30 min of recovery. In conclusion, acute HIIE triggers a transient proaggregant status that is reverted after a 30 min of recovery. The effects of HIIE in lymphocytes remained after 30 min of recovery, indicating a pro-inflammatory response. This work elucidated some of the mechanisms by which purinergic system regulates lymphocytes and platelets activities related to HIIE, suggesting that the type of exercise may influence an increase in platelet aggregation even in trained individuals.

Metabolic and IL-6-Induced Inflammatory Responses in High-Intensity Intermittent Exercise among Type 2 Diabetes Patients with Sarcopenia

Objective: The aim of this study was to examine the effects of high-intensity intermittent exercise (HIIE) on features of immunometabolism by comparing elderly female sarcopenia and non-sarcopenia in elderly female patients with type 2 diabetes (T2MD). Differences in metabolism and inflammatory responses between the two groups were compared. Methods: 6 elderly female sarcopenia patients with T2MD served as sarcopenia group, and 7 elderly female non-sarcopenia patients with T2MD served as control subjects. Using dual energy X-ray absorptiometry (DXA) to the subjects’ body fat compositions was measured. All subjects underwent three high-intensity Wingate tests at 5-minute intervals, and peak and average power during each Wingate trial were recorded. Blood samples were collected immediately after the test was completed. Peripheral blood levels of the inflammatory cytokine IL-6, which is related to mitosis, were measured in both groups before and after HIIE by ELISA. Results: The non-sarcopenia group had a higher metabolic rate than the sarcopenia group. Sarcopenia had no significant effect on the differences in the IL-6 inflammatory response (p = 0.430). Conclusion: The metabolic energy and rate during HIIE differed between the two groups. Non-sarcopenia group exhibited higher metabolic levels. No significant difference between groups was observed in the IL-6 inflammatory response during HIIE.

Exercise intensity and hypertension: what's new?

One bout of aerobic exercise and regular participation in aerobic exercise has been shown to result in a lowering of office and ambulatory blood pressure of hypertensive individuals. Higher-intensity aerobic exercise, up to 70% of maximal oxygen consumption, does not produce a greater hypotensive effect, compared with moderate-intensity aerobic exercise. Intermittent aerobic and anaerobic exercise, however, performed at an intensity >70% of maximal oxygen uptake has been shown to significantly reduce office and ambulatory blood pressure of hypertensive individuals. Thus, faster, more intense forms of exercise can also bring about blood pressure reduction in the hypertensive population. Compared with continuous moderate-intensity aerobic exercise, high-intensity intermittent exercise typically results in a greater aerobic fitness increase in less time and produces greater changes in arterial stiffness, endothelial function, insulin resistance and mitochondrial biogenesis. One of the characteristics of high-intensity intermittent training is that it typically involves markedly lower training volume compared with traditional aerobic and resistance exercise programmes making it a time-efficient strategy to accrue adaptations and blood pressure benefits. This review briefly summarizes the results of studies that have examined the effects of single and repeated bouts of aerobic and resistance exercise on office and ambulatory blood pressure of hypertensive individuals. Then a more detailed summary of studies examining the effect of high-intensity intermittent exercise and training on hypertension is provided.

High-Intensity Intermittent Exercise: Effect on Young People's Cardiometabolic Health and Cognition.

With only a quarter of young people currently meeting physical activity guidelines, two key areas of concern are the effects of exercise on cardiometabolic health and cognition. Despite the fact that physical activity in young people is typically high intensity and intermittent in nature, much of the literature examines traditional endurance-type exercise. This review provides an update on the effects of high-intensity intermittent exercise on young people's cardiometabolic health and cognition. High-intensity intermittent exercise has acute beneficial effects on endothelial function and postprandial lipemia and chronic positive effects on weight management. In addition, there is emerging evidence regarding chronic benefits on the blood lipid profile, blood pressure, and proinflammatory and anti-inflammatory cytokines. Furthermore, emerging evidence suggests beneficial acute and chronic effects of high-intensity intermittent exercise on cognition. However, further research is required in both cardiometabolic health and cognition, particularly regarding the impact of school-based interventions in adolescents.

Effect Of High-intensity Intermittent Exercise On Abdominal Fat Mass In Type 2 Diabetes Postmenopausal Women.

Effect Of High-intensity Intermittent Exercise On Abdominal Fat Mass In Type 2 Diabetes Postmenopausal Women.

Effect of High-Intensity Intermittent Exercise on Postprandial Plasma Triacylglycerol in Sedentary Young Women

High-intensity intermittent exercise (HIIE) such as the 30-s Wingate test attenuates postprandial triacylglycerol (TG), however, the ability of shorter versions of HIIE to reduce postprandial TG is undetermined. Thus, the effect of 8-s sprinting bouts of HIIE on blood TG levels of 12 females after consumption of a high-fat meal (HFM) was examined. Twelve young, sedentary women (BMI 25.1 ± 2.3 kg/m²; age 21.3 ± 2.1 years) completed a maximal oxygen uptake test and then on different days underwent either an exercise or a no-exercise postprandial TG condition. Both conditions involved consuming a HFM after a 12-hr fast. The HFM, in milkshake form provided 4170 kJ (993 Kcal) of energy and 98 g fat. Order was counter-balanced. In the exercise condition participants completed 20-min of HIIE cycling consisting of repeated bouts of 8 s sprint cycling (100-115 rpm) and 12 s of active rest (easy pedaling) 14 hr before consuming the HFM. Blood samples were collected hourly after the HFM for 4 hr. Total postprandial TG was 13% lower, p = .004, in the exercise (5.84 ± 1.08 mmol L⁻¹ 4 h⁻¹) compared with the no-exercise condition (6.71 ± 1.63 mmol L⁻¹ 4 h⁻¹). In conclusion, HIIE significantly attenuated postprandial TG in sedentary young women.

High-intensity intermittent exercise attenuates ad-libitum energy intake

To examine the acute effects of high-intensity intermittent exercise (HIIE) on energy intake, perceptions of appetite and appetite-related hormones in sedentary, overweight men. Seventeen overweight men (body mass index: 27.7±1.6 kg m(-2); body mass: 89.8±10.1 kg; body fat: 30.0±4.3%; VO(2peak): 39.2±4.8 ml kg(-1) min(-1)) completed four 30-min experimental conditions using a randomised counterbalanced design. CON: resting control, MC: continuous moderate-intensity exercise (60% VO(2peak)), HI: high-intensity intermittent exercise (alternating 60 s at 100% VO(2peak) and 240 s at 50% VO(2peak)), VHI: very-high-intensity intermittent exercise (alternating 15 s at 170% VO(2peak) and 60 s at 32% VO(2peak)). Participants consumed a standard caloric meal following exercise/CON and an ad-libitum meal 70 min later. Capillary blood was sampled and perceived appetite assessed at regular time intervals throughout the session. Free-living energy intake and physical activity levels for the experimental day and the day after were also assessed. Ad-libitum energy intake was lower after HI and VHI compared with CON (P=0.038 and P=0.004, respectively), and VHI was also lower than MC (P=0.028). Free-living energy intake in the subsequent 38 h remained less after VHI compared with CON and MC (P≤0.050). These observations were associated with lower active ghrelin (P≤0.050), higher blood lactate (P≤0.014) and higher blood glucose (P≤0.020) after VHI compared with all other trials. Despite higher heart rate and ratings of perceived exertion (RPE) during HI and VHI compared with MC (P≤0.004), ratings of physical activity enjoyment were similar between all the exercise trials (P=0.593). No differences were found in perceived appetite between trials. High-intensity intermittent exercise suppresses subsequent ad-libitum energy intake in overweight inactive men. This format of exercise was found to be well tolerated in an overweight population.

The Effects of High-Intensity Intermittent Exercise Compared With Continuous Exercise on Voluntary Water Ingestion

Water intake occurs following a period of high-intensity intermittent exercise (HIIE) due to sensations of thirst yet this does not always appear to be caused by body water losses. Thu.s, the aim was to assess voluntary water intake following HIIE. Ten healthy males (22 ± 2 y, 75.6 ± 6.9 kg, VO2(peak) 57.3 ± 11.4 m · kg(-1) · min(-1); mean ± SD) completed two trials (7-14 d apart). Subjects sat for 30 min then completed an exercise period involving 2 min of rest followed by 1 min at 100% VO2(peak repeated for 60 min (HIIE) or 60 min continuously at 33% VO2(peak) (LO). Subjects then sat for 60 min and were allowed ad libitum water intake. Body )mass was measured at start and end of trials. Serum osmolality, blood lactate, and sodium concentrations, sensations of thirst and mouth dryness were measured at baseline, postexercise and after 5, 15, 30, and 60 min of recovery. Vasopressin concentration was measured at baseline, postexercise, 5 min, and 30 min. Body mass loss over the whole trial was similar (HIIE: 0.77 ± 0.50; LO: 0.85 ± 0.55%; p = .124). Sweat lost during exercise (0.78 ± 0.22 vs. 0.66 ± 0.26 L) and voluntary water intake during recovery (0.416 ± 0.299 vs. 0.294 ± 0.295 L; p < .05) were greater in HIIE. Serum osmolality (297 ± 3 vs. 288 ± 4 mOsmol · kg(-1)), blood lactate (8.5 ± 2.7 vs. 0.7 ± 0.4 mmol · L(-1)), serum sodium (146 ± 1 vs. 143 ± 1 mmol · L(-1)) and vasopressin (9.91 ± 3.36 vs. 4.43 ± 0.86 pg · ml(-1)) concentrations were higher after HIIE (p < .05) and thirst (84 ± 7 vs. 60 ± 21) and mouth dryness (87 ± 7 vs. 64 ± 23) also tended to be higher (p = .060). Greater voluntary water intake after HIIE was mainly caused by increased sweat loss and the consequences of increased serum osmolality mainly resulting from higher blood lactate concentrations.

High-intensity exercise attenuates postprandial lipaemia and markers of oxidative stress

Regular exercise can reduce the risk of CVD (cardiovascular disease). Although moderate-intensity exercise can attenuate postprandial TAG (triacylglycerol), high-intensity intermittent exercise might be a more effective method to improve health. We compared the effects of high-intensity intermittent exercise and 30min of brisk walking on postprandial TAG, soluble adhesion molecules and markers of oxidative stress. Nine men each completed three 2-day trials. On day 1, subjects rested (control), walked briskly for 30min (walking) or performed 5×30s maximal sprints (high-intensity). On day 2, subjects consumed a high-fat meal for breakfast and 3h later for lunch. Blood samples were taken at various times and analysed for TAG, glucose, insulin, ICAM-1 (intracellular adhesion molecule-1), VCAM-1 (vascular adhesion molecule-1), TBARS (thiobarbituric acid- reactive substances), protein carbonyls and β-hydroxybutyrate. On day 2 of the high-intensity trial, there was a lower (P<0.05) incremental TAG AUC (area under the curve; 6.42±2.24mmol/l per 7h) compared with the control trial (9.68±4.77mmol/l per 7h) with no differences during day 2 of the walking trial (8.98±2.84mmol/l per 7h). A trend (P=0.056) for a reduced total TAG AUC was also seen during the high-intensity trial (14.13±2.83mmol/l per 7h) compared with control (17.18±3.92mmol/l per 7h), walking showed no difference (16.33±3.51mmol/l per 7h). On day 2 of the high-intensity trial plasma TBARS and protein carbonyls were also reduced (P<0.05) when compared with the control and walking trials. In conclusion, high-intensity intermittent exercise attenuates postprandial TAG and markers of oxidative stress after the consumption of a high-fat meal.

The Effect of High-Intensity Intermittent Exercise on Body Composition of Overweight Young Males

To determine the effect of a 12-week high intensity intermittent exercise (HIIE) intervention on total body, abdominal, trunk, visceral fat mass, and fat free mass of young overweight males. Participants were randomly assigned to either exercise or control group. The intervention group received HIIE three times per week, 20 min per session, for 12 weeks. Aerobic power improved significantly (P < 0.001) by 15% for the exercising group. Exercisers compared to controls experienced significant weight loss of 1.5 kg (P < 0.005) and a significant reduction in total fat mass of 2 kg (P < 0.001). Abdominal and trunk adiposity was also significantly reduced in the exercising group by 0.1 kg (P < 0.05) and 1.5 kg (P < 0.001). Also the exercise group had a significant (P < 0.01) 17% reduction in visceral fat after 12 weeks of HIIE, whereas waist circumference was significantly decreased by week six (P < 0.001). Fat free mass was significantly increased (P < 0.05) in the exercising group by 0.4 kg for the leg and 0.7 kg for the trunk. No significant change (P > 0.05) occurred in levels of insulin, HOMA-IR, and blood lipids. Twelve weeks of HIIE resulted in significant reductions in total, abdominal, trunk, and visceral fat and significant increases in fat free mass and aerobic power.

The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women

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.

Effect of High-Intensity Intermittent Exercise on Secretory IgA Response and Salivary Flow Rate

2187 Athletes are susceptible to upper respiratory tract infection (URTI) during intense training and after major competition. Previous studies have shown that concentration and flow rate of secretary immunoglobulin A (s-IgA), the major of effector of host defence to URTI, decrease after intense exercise. These effects can be observed several hours after exercise, and the resulting transient immunosupression is postulated to be responsible for increased URTI episodes. PURPOSE: The purpose of this study was to examine the salivary IgA response during and after repeated bouts of brief, intermittent, maximal exercise. METHODS: Ten non-smoking, adult male rugby and hockey players (age = 24.4 years ± 3.41; body mass = 84.95 kg ± 9.42; stature = 186.3 cm ± 8.83) volunteered to participate in this study. The exercise intervention consisted of three consecutive, all-out 30-second Wingate (WAnT) leg cycle tests (0.098 kg. kgBW−1 kgBW) separated by 6 minutes of recovery. Unstimulated whole saliva was collected before, during and 1 and 24 hrs post exercise. Subjects also provided a saliva sample prior to the day of testing. Absolute salivary IgA concentrations were measured by ELISA and flow rates calculated. RESULTS: Salivary flow rates decreased significantly (P < 0.05) by 26%, 30% and 39% after each WAnT, before returning to resting levels 1 hr post-exercise. Salivary IgA secretion rates were significantly reduced (P < 0.05) after each WAnT (20%, 32% and 42% respectively), but did not return to base-line levels until 24 hrs post-exercise. No significant differences (P > 0.05) were observed for absolute IgA concentrations. CONCLUSIONS: These data suggest that salivary IgA flow rate decreases with bouts of maximal exercise, and that this is due, at least partially, to the reduction in salivary output. Further, there appears to be a specific effect of intense exercise on s-IgA concentration which is greater than that due to decreased saliva flow rate alone. Mucosal immunosupression was transient with s-IgA concentrations returning to base-line levels 24 hrs post-exercise. The results of this study suggest that reductions in s-IgA output after repeated bouts of maximal exercise may be one mechanism contributing to the higher incidence of URTI among athletes.