Intensity Intermittent Exercise Research Articles

The effect of aerobic exercise intensity on attenuation of postprandial lipemia is dependent on apolipoprotein E genotype

ObjectiveTo investigate the effect of aerobic exercise intensity on postprandial lipemia according to allelic variants of the apolipoprotein E gene. MethodsThree groups of 10 healthy men each were formed based genotyping of the APOE gene, rested or performed 500 Kcal tests in a random sequence separated by a minimum 48 h interval, as follows: (a) no exercise (control), (b) intense intermittent exercise, (c) moderate continuous exercise. Each test series was completed 30-min before ingestion of a high-fat meal (1 g fat/kg). Venous blood was collected before and at 1, 2, 3 and 4 h after the high-fat meal. Postprandial lipemia was assessed using the area under the curve approach as well as the kinetic profile of mean lipid variables. Statistical significance was adopted at P ≤ 0.05 level. ResultsThe main results show that, in the moderate continuous exercise, total postprandial cholesterolemia was higher in ɛ4 than in ɛ2 carriers, whereas under intense intermittent exercise, total and LDL cholesterolemia were higher in ɛ4 than in ɛ2 and ɛ3 carriers. There was no difference in the lipemic profile of the subjects across APOE genotypes at baseline. ConclusionModerate and intense exercise were effective in attenuating PPL in both ɛ2 and ɛ3 subjects, with ɛ2 subjects being more susceptible to the lipid lowering effect of moderate training than ɛ3 subjects. Carriers of the ɛ4 allele, however, showed no attenuation of postprandial lipemia.

1337 CARDIAC FUNCTION IMPROVES FOLLOWING HIGH INTENSITY INTERMITTENT EXERCISE THERAPY IN NON-ALCOHOLIC FATTY LIVER DISEASE

associated with a twofold greater risk of developing cardiovascular disease than those without. Recent research has shown that there are alterations in cardiac structure and function in NAFLD in the absence of overt cardiac disease. This study aimed to investigate exercise as a therapeutic tool to decrease cardiac risk in NAFLD. Patients and Methods: Twenty adults with NAFLD were randomised to 12 weeks of high intensity intermittent training or continue standard care. Cardiac structure and function were assessed using high resolution cardiac magnetic resonance imaging and tagging at 3.0T. High energy phosphate metabolism was assessed using 31 P-spectroscopy to measure PCr/ATP ratio. People with a history of discrete cardiac events or potential cardiac symptoms were excluded from the study. Liver fat was assessed using 1 H-magnetic resonance spectroscopy. The intervention group undertook exercise 3 times per week. Results: Exercise improved diastolic function in adults with NAFLD. E/A ratio increased with exercise (1.16±0.47 to 1.49±0.62; p = 0.022) but not in control (1.48± 0.98 to 1.17 ±0.46; p = 0.346) as did the early diastolic filling rate (exercise: 261.2±70.8 to 315.3±93.6 ml/s; p = 0.008, control: 276.2±86.2 to 281.9±75.3 ml/s; p = 0.757). Exercise also decreased peak cardiac torsion (exercise: 7.78±2.49 to 6.34±1.84deg; p = 0.048. control: 5.48±0.96 to 6.50±2.16deg; p = 0.300) but had no effect on cardiac structure, systolic function, or cardiac energetics. Conclusions: A 12-week high intensity intermittent exercise programme improves cardiac diastolic function and torsion in adults with NAFLD. Clinical care teams should consider high intensity intermittent exercise as part of their therapeutic regimen to modify the excess risk of cardiovascular disease associated with NAFLD.

운동강도와 지속시간에 따른 트레드밀 운동이 비만 쥐의 심장근 내 항산화에 미치는 영향

트레드밀 운동이 비만 쥐의 심장근 내 항산화에 어떠한 영향을 주는지 알아보고자 흰쥐에 6주 동안 고지방 식이로 비만을 유발시킨 뒤 운동강도와 적용시간을 달리하여 트레드밀을 3주 동안 적용하였으며, 체중변화, 혈중지질성분, 조직학적 변화, 심장근 내 항산화 효소와 MCP-1(monocyte chemoattractant protein-1) 등의 변화를 연구하였다. 4주령 Sprague Dawley계 수컷 흰쥐 32마리를 사용하여 각각 일반사료를 섭취한 정상군 (normal), 비만 대조군 (control), 비만 쥐에게 고강도 분할운동을 적용한 실험군 I(Experimental I), 비만 쥐에게 중강도 지구력 운동을 적용한 실험군 II (Experimental II)로 나누었다. 실험 결과 첫째, 체중변화는 고강도 분할 운동을 적용한 실험군 I과 중강도 지구력 운동을 적용한 실험군 II는 대조군에 비해 유의한 감소가 있었다 (p<0.001). 특히, 운동을 적용한 1주에서 3주까지 유의한 차이가 있었다. 둘째, 혈중지질성분 수치는 고강도 분할 운동을 적용한 실험군 I과 중강도 지구력 운동을 적용한 실험군 II는 대조군에 비해 총콜레스테롤, 중성지방, 저밀도 지단백질의 유의한 감소, 고밀도 지단백질에서는 유의한 증가가 있었다 (p<0.001). 셋째, 심장근의 조직학적 소견은 심장근에서 아교질 형성과 평활근 섬유의 정렬 상태와 밀집도, 심장근 세포크기가 중강도 지구력 운동 적용한 실험군 II에서 정상군과 비슷한 형태인 근육들이 잘 밀집해 있는 것을 볼 수 있었다. 또한, 섬유아세포, 염증세포들의 침윤 등이 고지방 식이 유발 쥐인 대조군과 고강도 분할 운동을 적용한 실험군 I에서 가장 심하였으며, 중강도 지구력 운동을 적용한 실험군 II는 대조군에 비해 섬유아세포, 염증세포들의 침윤 등이 현저히 감소하였다. 넷째, 심장근의 항산화 효소 SOD(superoxide dismutase), CAT(catalase), GPx(glutathione peroxidase) 수치는 중강도 지구력 운동을 적용한 실험군 II와 고강도 분할 운동을 적용한 실험군 I에서 모두 유의한 증가가 있었다 (p<0.001). 다섯째, 심장근의 항산화 단백질 MCP-1 발현 수치는 고강도 분할 운동을 적용한 실험군 I과 중강도 지구력 운동을 적용한 실험군 II 모두에서 감소가 있었으며 (p<0.01), 특히, 중강도 지구력 운동을 적용한 실험군 II에서는 유의한 감소가 있었다 (p<0.001). 따라서, 중강도 지구력 운동은 고지방 식이로 유발된 비만 쥐의 심장근 내 항산화에 영향을 주어 비만 개선과 산화적 스트레스에 의한 심장근육 손상 감소 등에 효과적인 것으로 나타났다. The aims of this study was to observed an effect of antioxidative in cardiac muscle of high fat diet induced obesity rat by treadmill exercise with intensity and time. Thirty-two Sprauge-Dawley rats which were divided into four group. Normal, Control(high fat diet induced obesity rat), Experimental I(high intensity intermittent exercise in high fat diet induced obesity rat), Experimental II(moderate intensity endurance exercise in high fat diet induced obesity rat). The results of this study were as follows: 1. In change of body weight, the outcome of each group significantly difference compared with control. Also, 1 to 3 weeks significantly different compared with pre valu experimental I and II(p<0.001). 2. In change of lipid profile, the outcome of each group significantly difference compared with control(p<0.001). Difference between experimental I and II is not significantly. 3. In change of antioxidative enzymes(SOD, CAT, GPx) in myocardium, there are significant difference between control and experimental II, and also between control and experimental I(p<0.001). 4. In change of antioxidative protein MCR-1, the outcome of each group significantly difference compared with control(p<0.01). Experimental II was most significantly difference than the other group(p<0.001). The above results suggest that treadmill exercise effectively reduced in fat. It would be considered that moderate intensity endurance exercise has an effects on improved antioxidative enzyme in cardiac muscle of high fat diet induced obesity rat.

Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance

Recent studies have suggested that dietary inorganic nitrate (NO₃(-)) supplementation may improve muscle efficiency and endurance exercise tolerance but possible effects during team sport-specific intense intermittent exercise have not been examined. We hypothesized that NO₃(-) supplementation would enhance high-intensity intermittent exercise performance. Fourteen male recreational team-sport players were assigned in a double-blind, randomized, crossover design to consume 490 mL of concentrated, nitrate-rich beetroot juice (BR) and nitrate-depleted placebo juice (PL) over ~30 h preceding the completion of a Yo-Yo intermittent recovery level 1 test (Yo-Yo IR1). Resting plasma nitrite concentration ([NO₂(-)]) was ~400% greater in BR compared to PL. Plasma [NO₂(-)] declined by 20% in PL (P < 0.05) and by 54 % in BR (P < 0.05) from pre-exercise to end-exercise. Performance in the Yo-Yo IR1 was 4.2% greater (P < 0.05) with BR (1,704 ± 304 m) compared to PL (1,636 ± 288 m). Blood [lactate] was not different between BR and PL, but the mean blood [glucose] was lower (3.8 ± 0.8 vs. 4.2 ± 1.1 mM, P < 0.05) and the rise in plasma [K(+)] tended to be reduced in BR compared to PL (P = 0.08). These findings suggest that NO₃(-) supplementation may promote NO production via the nitrate-nitrite-NO pathway and enhance Yo-Yo IR1 test performance, perhaps by facilitating greater muscle glucose uptake or by better maintaining muscle excitability. Dietary NO₃(-) supplementation improves performance during intense intermittent exercise and may be a useful ergogenic aid for team sports players.

Is it Yet Time to Throw Away the Old Recipe Book and Consider High Intensity Intermittent Exercise in Clinical Populations?

Is it Yet Time to Throw Away the Old Recipe Book and Consider High Intensity Intermittent Exercise in Clinical Populations? The first epidemiological exercise studies in the 1950’s established a cause-effect relationship between levels of physical inactivity and cardiovascular disease. In the interim other longitudinal, crosssectional, retrospective and prospective analyses have confirmed that physical activity is cardio-protective and also an inverse relationship exists between mortality rates and leisure time physical activity intensity.

Intense intermittent exercise provides weak stimulus for vascular endothelial growth factor secretion and capillary growth in skeletal muscle

The effect of acute intense intermittent exercise compared with moderate-intensity exercise on angiogenic factors and the effect of 4 weeks of intense intermittent training on capillary growth were examined in nine healthy young men, preconditioned by moderate-intensity endurance training. The intense training consisted of 24 bouts of 1 min cycling at an initial work rate of 316 ± 19 W (~117% of pretraining maximal oxygen uptake), performed three times per week. Skeletal muscle biopsies and muscle microdialysates were obtained from the vastus lateralis before, during and after acute exercise performed at either moderate or high intensity. Comparison of the response in angiogenic factors to acute moderate- versus high-intensity exercise, performed prior to the intense training intervention, revealed that intense exercise resulted in a markedly lower (~60%; P < 0.05) increase in interstitial vascular endothelial growth factor than did moderate-intensity exercise. Muscle interstitial fluid obtained during moderate-intensity exercise increased endothelial cell proliferation in vitro more than interstitial fluid obtained during intense exercise (sixfold versus 2.5-fold, respectively; P < 0.05). The 4 weeks of high-intensity training did not lead to an increased capillarization in the muscle but abolished the exercise-induced increase in mRNA for several angiogenic factors, increased the protein levels of endothelial nitric oxide synthase, lowered the protein levels of thrombospondin-1 in muscle but increased the interstitial protein levels of thrombospondin-1. We conclude that intense intermittent exercise provides a weak stimulus for vascular endothelial growth factor secretion and endothelial cell proliferation and that intense intermittent training does not induce a sufficient angiogenic stimulus to induce capillary growth in muscle previously conditioned by moderate-intensity exercise.

Effect of Fat and CHO Meals on Intermittent Exercise in Soccer Players

Pre-exercise meals containing carbohydrates (CHO) are recommended to athletes, although there is evidence to suggest that a high fat meal prior to exercise increases utilisation of fats yet may not adversely affect performance. This study investigated the effect of a high fat and high CHO pre-exercise meal prior to high intensity intermittent exercise. Ten male recreational soccer players performed a soccer specific protocol followed by a 1 km time trial 3 ½ h after ingesting one of 2 test meals, high fat meal (HFM) or a high CHO meal (HCM). Blood glucose, fatty acids (FA), glycerol, β-hydroxybutyrate, lactate and insulin were assessed prior to the meal, pre-exercise, half-time, and post-exercise, whilst rates of CHO and fat oxidation were determined at 4 time points during the exercise as well as heart rate (HR) and rating of perceived exertion (RPE). Significant increases in FA, glycerol, β-hydroxybutyrate and fat oxidation after the HFM were observed, while CHO oxidation was significantly higher following the HCM (P<0.05). No performance effect was found for the 1 km time trial (HFM: 228.6+14.4 s; HCM: 229.4+26.5 s) (mean+SD). These findings suggest that the type of meal ingested prior to soccer simulated exercise has an impact on metabolism, but not on the subsequent performance as determined in the present study.

641 Comparison of Carbohydrate and Lipid Oxidation During Moderate Intensity Continous Exercise and High Intensity Intermittent Exercise in Patients With Chronic Heart Failure

BackgroundThe aim of this study was to compare carbohydrate and lipid oxidation during moderate intensity continuous exercise (MICE) and high intensity intermittent exercise (HIIE) in patients with chronic heart failure (CHF).MethodsEighteen males with CHF (60±9 years, LVEF = 26±7%, VO2peak = 17.4±5.5 mL/min/kg) were assigned in random order to a single session of high-intensity interval exercise corresponding to 2×8 min of 30s intervals at 100% of peak power output (PPO) and 30s passive recovery intervals and one week later to a 22 min isocaloric MICE corresponding to 60% of PPO. Gas exchange, ECG and blood pressure were monitored continuously. VO2 uptake and energy expenditure were assessed from gas exchanges and carbohydrate and lipid oxidation using the Frayn equation. Endpoints were carbohydrate and lipid oxidation measured during the last 2 minutes of HIIE blocs and corresponding same exercise time period on MICE.ResultsVO2 uptake and energy expenditure during exercise did not differ (P=0.10) between MICE (VO2=1208 and 1263±289 and 311 mL/min, EE=6.08 and 6.29±1.45 and 1.53 kcal/min) and HIIE (VO2=1048 and 1074±239 and 238 mL/min, EE=5.26 and 5.37±1.21 and 1.28 kcal/min). Carbohydrate (CHO) and lipid oxidation during exercise were similar (P=0.09 and 0.63) between MICE (CHO=1.66 and 1.46±0.48 and 0.37 g/min, lipids=0.05 and 0.10±0.06 and 0.09 g/min) and HIIE (CHO=1.39 and 1.20±0.45 and 0.39 g/min, lipids=0.06 and 0.11±0.05 and 0.06 g/min) in CHF patients.ConclusionThese findings showed that carbohydrate and lipid oxidation during exercise are similar between 2 isoenergetic exercise bouts of different form and intensities in CHF patients.EPIC Foundation, MHIF BackgroundThe aim of this study was to compare carbohydrate and lipid oxidation during moderate intensity continuous exercise (MICE) and high intensity intermittent exercise (HIIE) in patients with chronic heart failure (CHF). The aim of this study was to compare carbohydrate and lipid oxidation during moderate intensity continuous exercise (MICE) and high intensity intermittent exercise (HIIE) in patients with chronic heart failure (CHF). MethodsEighteen males with CHF (60±9 years, LVEF = 26±7%, VO2peak = 17.4±5.5 mL/min/kg) were assigned in random order to a single session of high-intensity interval exercise corresponding to 2×8 min of 30s intervals at 100% of peak power output (PPO) and 30s passive recovery intervals and one week later to a 22 min isocaloric MICE corresponding to 60% of PPO. Gas exchange, ECG and blood pressure were monitored continuously. VO2 uptake and energy expenditure were assessed from gas exchanges and carbohydrate and lipid oxidation using the Frayn equation. Endpoints were carbohydrate and lipid oxidation measured during the last 2 minutes of HIIE blocs and corresponding same exercise time period on MICE. Eighteen males with CHF (60±9 years, LVEF = 26±7%, VO2peak = 17.4±5.5 mL/min/kg) were assigned in random order to a single session of high-intensity interval exercise corresponding to 2×8 min of 30s intervals at 100% of peak power output (PPO) and 30s passive recovery intervals and one week later to a 22 min isocaloric MICE corresponding to 60% of PPO. Gas exchange, ECG and blood pressure were monitored continuously. VO2 uptake and energy expenditure were assessed from gas exchanges and carbohydrate and lipid oxidation using the Frayn equation. Endpoints were carbohydrate and lipid oxidation measured during the last 2 minutes of HIIE blocs and corresponding same exercise time period on MICE. ResultsVO2 uptake and energy expenditure during exercise did not differ (P=0.10) between MICE (VO2=1208 and 1263±289 and 311 mL/min, EE=6.08 and 6.29±1.45 and 1.53 kcal/min) and HIIE (VO2=1048 and 1074±239 and 238 mL/min, EE=5.26 and 5.37±1.21 and 1.28 kcal/min). Carbohydrate (CHO) and lipid oxidation during exercise were similar (P=0.09 and 0.63) between MICE (CHO=1.66 and 1.46±0.48 and 0.37 g/min, lipids=0.05 and 0.10±0.06 and 0.09 g/min) and HIIE (CHO=1.39 and 1.20±0.45 and 0.39 g/min, lipids=0.06 and 0.11±0.05 and 0.06 g/min) in CHF patients. VO2 uptake and energy expenditure during exercise did not differ (P=0.10) between MICE (VO2=1208 and 1263±289 and 311 mL/min, EE=6.08 and 6.29±1.45 and 1.53 kcal/min) and HIIE (VO2=1048 and 1074±239 and 238 mL/min, EE=5.26 and 5.37±1.21 and 1.28 kcal/min). Carbohydrate (CHO) and lipid oxidation during exercise were similar (P=0.09 and 0.63) between MICE (CHO=1.66 and 1.46±0.48 and 0.37 g/min, lipids=0.05 and 0.10±0.06 and 0.09 g/min) and HIIE (CHO=1.39 and 1.20±0.45 and 0.39 g/min, lipids=0.06 and 0.11±0.05 and 0.06 g/min) in CHF patients. ConclusionThese findings showed that carbohydrate and lipid oxidation during exercise are similar between 2 isoenergetic exercise bouts of different form and intensities in CHF patients.EPIC Foundation, MHIF These findings showed that carbohydrate and lipid oxidation during exercise are similar between 2 isoenergetic exercise bouts of different form and intensities in CHF patients.

Effect of repeated oral administration of glucose and leucine immediately after exercise on plasma insulin concentration and glycogen synthesis in horses

To determine whether repeated oral administration of glucose and leucine during the period immediately after intense exercise would increase the release of insulin and thereby enhance glycogen synthesis in horses. 12 Standardbred horses. In a crossover study design, after glycogen-depleting exercise, horses received oral boluses of glucose (1 g/kg at 0, 2, and 4 hours) and leucine (0.1 g/kg at 0 and 4 hours) or boluses of water (10 mL/kg at 0, 2, and 4 hours; control treatment). Blood samples for determination of glucose, insulin, and leucine concentrations were collected prior to and during a 6-hour period immediately after exercise. Biopsy specimens of a gluteus muscle were obtained before and immediately after exercise and at 3, 6, and 24 hours after exercise for measurement of glycogen concentration. When glucose and leucine were administered to the horses, plasma insulin concentration was significantly higher during the 6 hours immediately after exercise than it was when water was administered to the horses. Serum glucose concentration during the 4 hours immediately after exercise was significantly higher when glucose and leucine were administered than the serum glucose concentration when water was administered. Muscle glycogen concentrations did not differ between the 2 treatments during the 24 hours after exercise. Synthesis of muscle glycogen after intense intermittent exercise was not enhanced by oral boluses of glucose and leucine after exercise despite pronounced increases in plasma insulin and serum glucose concentrations.

Exercise and Inflammation in Pediatric Crohn's Disease

We examined inflammatory cells, cytokines and growth factors in response to acute bouts of moderate intensity continuous exercise and high intensity intermittent exercise in youth with Crohn's disease and in healthy matched-controls. 15 patients and 15 controls performed 30 min of cycling at 50% of peak mechanical power (PMP) and 6 bouts of 4×15-s of cycling at 100% PMP. Blood was collected at rest, at the mid-point, at the end of exercise and at 30 and 60 min into recovery. In patients with CD, both types of exercise increased immune cells and GH and decreased IGF-I. Moderate intensity exercise induced a greater increase in leukocytes (p<0.05), neutrophils (p<0.05), lymphocytes (p<0.001), monocytes (p<0.05), IL-6 (p<0.05), IL-17 (p<0.05) and GH (p<0.05) and a similar decrease in IGF-I, compared with high intensity exercise. TNF-α did not change significantly with either exercise. Responses in patients were similar compared with controls; however, in patients monocytes remained elevated significantly longer in response to MICE. Youth with Crohn's disease can engage in distinctly different types of exercise without a significant acute exacerbation of inflammation.

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.

Volitional fatigue occurs with considerable muscle metabolic reserve during intense intermittent forearm exercise

Introduction: This study was completed to investigate the extent of phosphagen system depletion, intramuscular acidosis and their recovery during and between 3 bouts of high intensity forearm wrist flexion exercise.

Effects of active and passive recovery on intense intermittent forearm exercise

Effects of active and passive recovery on intense intermittent forearm exercise

Respiratory and locomotor muscle blood-volume and oxygenation kinetics during intense intermittent exercise

In this study, we examined the time course of changes in the blood volume and oxygenation of accessory respiratory (RM) and locomotor (LM) muscles, and the interrelationships of changes in these parameters during maximal incremental intermittent exercise in 15 non-endurance-trained active men. Blood volume and oxygenation of the serratus anterior and of vastus lateralis were measured simultaneously by near-infrared spectroscopy. The respiratory compensation point, and the breakpoints where abrupt changes were apparent in RM and LM blood volume and oxygenation versus time were identified. During exercise, the decreases in RM and LM oxygenation were accentuated in the vicinity of the respiratory compensation point. This was concomitant with a reduction in LM, but not RM, blood volume. The time at which the respiratory compensation point and the breakpoints in RM and LM blood volume and oxygenation were detected (70.2–75.0% exercise time) did not differ, and were inter-correlated (r=0.56 to 0.95). Moreover, the rate of the accelerated fall of oxygenation in the locomotor muscles was correlated with that of the decline in blood volume in that area (r=0.73), and with that of the accelerated fall of oxygenation in the respiratory muscles (r=0.71). The results suggest that the high ventilatory demand, which occurs naturally during intense intermittent exercise in non-endurance-trained individuals, may precipitate an accelerated fall in RM oxygenation, concomitant with a reduction in LM blood volume and an accentuated decline in LM oxygenation. Such responses are likely to occur above the respiratory compensation point during intermittent exercise.

Caffeine intake improves intense intermittent exercise performance and reduces muscle interstitial potassium accumulation

The effect of oral caffeine ingestion on intense intermittent exercise performance and muscle interstitial ion concentrations was examined. The study consists of two studies (S1 and S2). In S1, 12 subjects completed the Yo-Yo intermittent recovery level 2 (Yo-Yo IR2) test with prior caffeine (6 mg/kg body wt; CAF) or placebo (PLA) intake. In S2, 6 subjects performed one low-intensity (20 W) and three intense (50 W) 3-min (separated by 5 min) one-legged knee-extension exercise bouts with (CAF) and without (CON) prior caffeine supplementation for determination of muscle interstitial K(+) and Na(+) with microdialysis. In S1 Yo-Yo IR2 performance was 16% better (P < 0.05) in CAF compared with PLA. In CAF, plasma K(+) at the end of the Yo-Yo IR2 test was 5.2 ± 0.1 mmol/l with no difference between the trials. Plasma free fatty acids (FFA) were higher (P < 0.05) in CAF than PLA at rest and remained higher (P < 0.05) during exercise. Peak blood glucose (8.0 ± 0.6 vs. 6.2 ± 0.4 mmol/l) and plasma NH(3) (137.2 ± 10.8 vs. 113.4 ± 13.3 μmol/l) were also higher (P < 0.05) in CAF compared with PLA. In S2 interstitial K(+) was 5.5 ± 0.3, 5.7 ± 0.3, 5.8 ± 0.5, and 5.5 ± 0.3 mmol/l at the end of the 20-W and three 50-W periods, respectively, in CAF, which were lower (P < 0.001) than in CON (7.0 ± 0.6, 7.5 ± 0.7, 7.5 ± 0.4, and 7.0 ± 0.6 mmol/l, respectively). No differences in interstitial Na(+) were observed between CAF and CON. In conclusion, caffeine intake enhances fatigue resistance and reduces muscle interstitial K(+) during intense intermittent exercise.

Alterations in peripheral muscle contractile characteristics following high and low intensity bouts of exercise

The aim of this study was to monitor muscle contractile performance in vivo, using an electrical stimulation protocol, immediately following an acute high and low intensity exercise session conducted at the same average intensity performed on a cycle ergometer. Eighteen healthy males (25.1 ± 4.5 years, 81.6 ± 9.8 kg, 1.83 ± 0.06 m; mean ± SD) participated in the study. On two occasions, separated by 1 week, subjects completed a high and low intensity exercise session in a random order on a cycle ergometer, performing equal total work in each. At the end of each test, a muscle performance test using electrical stimulation was performed within 120 s. Post-exercise muscle data were compared to the subjects' rested muscle. We found a reduction in muscle contractile performance following both high and low intensity exercise protocols but a greater reduction in maximal voluntary contraction (MVC) (P < 0.01), rate of torque development (RTD) (P < 0.001), rate of relaxation (RR(½)), (P < 0.001) the 60 s slope of the fatigue protocol (P < 0.01) and torque frequency response (P < 0.05) following the high intensity bout. Importantly muscle performance remained reduced 1 h following high intensity exercise but was recovered following low intensity exercise. Muscle function was significantly reduced following higher intensity intermittent exercise in comparison to lower intensity exercise even when the average overall intensity was the same. This study is the first to demonstrate the sensitivity of muscle contractile characteristics to different exercise intensities and the impact of higher intensity bursts on muscle performance.

Effect of DHEA Supplementation on Changes in Hormone Levels After High Intensity Intermittent Exercise in Young and Middle Aged Men

Effect of DHEA Supplementation on Changes in Hormone Levels After High Intensity Intermittent Exercise in Young and Middle Aged Men

Visceral Fat Mass Of Overweight Males Following 12 Weeks Of High Intensity Intermittent Exercise

The ability of high intensity intermittent exercise (HIIE) to reduce visceral fat mass of overweight males is undetermined. PURPOSE: To examine the effect of a 12-week HIIE intervention on body fat levels of sedentary overweight men. METHODS: Thirty two males aged 24.7±4.2 years, with a BMI of 28.7±3.3 kg/m2, and body mass of 88.6±11.8 kg underwent atest pre- and posttraining. Total body fat was assessed by dual energy x-ray absorptiometry and visceral, hepatic, and spinal fat by computed tomography. Subjects, who were randomly assigned to HIIE (n=17) or control groups (n=15), exercised three times a week for 12 weeks under supervision. The HIIE group completed 20 minutes of exercise (8 s sprint, 12 s recovery) each session, whereas controls performed no structured exercise for 12 weeks. Dietary intake was monitored through food diaries. RESULTS: was significantly improved, P<0.05, by an increase of 13.8% in the HIIE group (33.0±4.3 to 38.3±3.7 ml.kg.min-1) and remained unchanged in the control group. Total fat mass in the HIIE group was significantly reduced (30.3±7.2 to 28.2±7.0 kg) by 7%, whereas in the controls it was unchanged (30.7±8.6 to 30.6±9.2 kg). Visceral fat at L2/L3 in the HIIE group was also significantly reduced (103.5±37.9 to 94.5±37.4 g) by 8.7% compared to that of controls (99.1±44.6 to 96.8±41.9 g). CONCLUSIONS: Twenty minutes of HIIE, three times a week for 12 weeks, led to a significant reduction in visceral and total fat mass in overweight, young males. Hepatic and spinal fat were unchanged.

The Effect Of Green Tea Extract And High Intensity Intermittent Exercise On Fat Oxidation

The effect of green tea extract (GT) and high intensity intermittent exercise (HIIE) upon fat oxidation is undetermined. PURPOSE: To examine the acute effects of GT and HIIE upon resting and post-exercise fat oxidation in young males and females. METHODS: Eleven females (21.72 ± 2.05 years; BMI 24.5 ± 1.51 kg/m2; body mass of 64.81 ± 6.84 kg) and five males (21.6 ±1.8 years; BMI 25.8 ± 4.2 kg/m2; body mass of 76.3 ± 16.0 kg) ingested four capsules containing either GT extract (total of 187.5 mg polyphenols, 125 mg EGCG, 20 mg caffeine) or placebo (500 mg cellulose) within twenty four hours (3 capsules) and 50 min (1 capsule) before each exercise trial. Order was counter-balanced and the study was double-blinded. Subjects were monitored for resting metabolic rate for 30 minutes, then completed a 20-min HIIE cycling protocol consisting of repeated bouts of 8 s sprint cycling (60-65% maximal oxygen uptake at 110-115 revolutions per minute) and 12 s recovery (20-25% maximal oxygen uptake at 40 revolutions per minute), followed by 1 hour of post-exercise recovery monitoring. RESULTS: GT significantly increased fat oxidation (21%) during rest P<0.05. GT also significantly increased fat oxidation (23%) after exercise P<0.05. During rest caloric expenditure, resting heart rate, and oxygen uptake were similar for both conditions, whereas during the post-exercise recovery period oxygen uptake was significantly greater during GT compared to placebo, P<0.05. CONCLUSION: Ingestion of GT significantly elevated fat oxidation during rest and after HIIE for both males and females.

Fat Oxidation at Rest and During Exercise of Responders and Non-Responders Following a Lifestyle Intervention

The inability to oxidize fat is associated with impaired fat loss when undergoing an aerobic exercise intervention. Whether this relationship also applies to a high intensity intermittent exercise (HIIE) lifestyle intervention is undetermined. PURPOSE: The resting respiratory quotient (RQ) and exercise respiratory exchange ratio (RER) of fat loss responders (RES) and non-responders (NRES) to a 12-week lifestyle intervention consisting of HIIE, fish oil (FO) supplementation, and Mediterranean diet (Mediet) were examined. METHODS: Sedentary overweight females (N=34; BMI 27.0 ± 0.5 kg/m2; age 23.5 ± 0.7 yrs) underwent pre- and posttraining testing including a V02peak test, a resting RQ and RER during incremental exercise, a blood draw, and a dual energy x-ray absorptiometry (DEXA) scan to measure body composition. The women (RES; n = 21 and NRES; n = 13) undertook 36 supervised HIIE (8 s:12 s) sessions for a total of 20 minutes. Dietary intake and daily FO (1.7 g of eicosapentaenoic and decosahexaenoic acid) consumption was monitored throughout. The groups were based on body weight loss; RES lost ≥ 1% of their initial body weight while NRES did not. A student's t-tests was used to examine differences pre- and posttraining and between groups. Results are expressed as mean +/- standard error. RESULTS: The RES significantly decreased their fat mass (-2.7 ± 0.4 vs. 0.6 ± 0.4 kg, P<0.001) and overall body weight (-2.8 ± 0.4 vs. 1.2 ± 0.3 kg, P<0.001) compared to NRES. Both groups significantly increased V02peak (0.28 ± 0.03 vs. 0.29 ± 0.03 L/min, P<0.001) and decreased insulin (3.4 ± 1.0 vs. 2.2 ± 0.1 μIU/ml, P<0.05) and interluekin-6 (0.5 ± 0.0 vs. 0.4 ± 0.1 pg/ml, P<0.001) with no significant difference between them. RQ was significantly (P<0.05) higher for NRES (0.93 ± 0.02) than RES (0.87 ± 0.01) and remained unchanged after the intervention. In contrast, RER significantly (P<0.05) decreased during exercise for both groups following the intervention and the reduction was related to fat loss (r=.60, P<0.05). CONCLUSION: Thirty-six bouts of HIIE, FO, and a Mediet led to significant fat loss in most but not all women. The RQ remained unchanged, although significantly different at baseline, whereas the reduction in RER predicted fat loss after the intervention suggesting an increase in fat oxidation during exercise is important for fat loss.