Showing papers on "Interval training published in 2010"

A practical model of low‐volume high‐intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms

Abstract: High-intensity interval training (HIT) induces skeletal muscle metabolic and performance adaptations that resemble traditional endurance training despite a low total exercise volume. Most HIT studies have employed ‘all out’, variable-load exercise interventions (e.g. repeated Wingate tests) that may not be safe, practical and/or well tolerated by certain individuals. Our purpose was to determine the performance, metabolic and molecular adaptations to a more practical model of low-volume HIT. Seven men (21 ± 0.4 years, ml kg−1 min−1) performed six training sessions over 2 weeks. Each session consisted of 8–12 × 60 s intervals at ∼100% of peak power output elicited during a ramp peak test (355 ± 10 W) separated by 75 s of recovery. Training increased exercise capacity, as assessed by significant improvements on both 50 kJ and 750 kJ cycling time trials (P < 0.05 for both). Skeletal muscle (vastus lateralis) biopsy samples obtained before and after training revealed increased maximal activity of citrate synthase (CS) and cytochrome c oxidase (COX) as well as total protein content of CS, COX subunits II and IV, and the mitochondrial transcription factor A (Tfam) (P < 0.05 for all). Nuclear abundance of peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α) was ∼25% higher after training (P < 0.05), but total PGC-1α protein content remained unchanged. Total SIRT1 content, a proposed activator of PGC-1α and mitochondrial biogenesis, was increased by ∼56% following training (P < 0.05). Training also increased resting muscle glycogen and total GLUT4 protein content (both P < 0.05). This study demonstrates that a practical model of low volume HIT is a potent stimulus for increasing skeletal muscle mitochondrial capacity and improving exercise performance. The results also suggest that increases in SIRT1, nuclear PGC-1α, and Tfam may be involved in coordinating mitochondrial adaptations in response to HIT in human skeletal muscle.

Effect of 2 weeks of sprint interval training on health-related outcomes in sedentary overweight/obese men.

Abstract: The aim of this study was to investigate the effects of very high intensity sprint interval training (SIT) on metabolic and vascular risk factors in overweight/obese sedentary men. Ten men (age, 32.1 ± 8.7 years; body mass index, 31.0 ± 3.7 kg m −2 ) participated. After baseline metabolic, anthropometric, and fitness measurements, participants completed a 2-week SIT intervention, comprising 6 sessions of 4 to 6 repeats of 30-second Wingate anaerobic sprints on an electromagnetically braked cycle ergometer, with 4.5-minute recovery between each repetition. Metabolic, anthropometric, and fitness assessments were repeated post-intervention. Both maximal oxygen uptake (2.98 ± 0.15 vs 3.23 ± 0.14 L min −1 , P = .013) and mean Wingate power (579 ± 24 vs 600 ± 19 W, P = .040) significantly increased after 2 weeks of SIT. Insulin sensitivity index (5.35 ± 0.72 vs 4.34 ± 0.72, P = .027) and resting fat oxidation rate in the fasted state (0.13 ± 0.01 vs 0.11 ± 0.01 g min −1 , P = .019) were significantly higher and systolic blood pressure (121 ± 3 vs 127 ± 3 mm Hg, P = .020) and resting carbohydrate oxidation in the fasted state (0.03 ± 0.01 vs 0.08 ± 0.02 g min −1 , P = .037) were significantly lower 24 hours post-intervention compared with baseline, but these changes were no longer significant 72 hours post-intervention. Significant decreases in waist (98.9 ± 3.1 vs 101.3 ± 2.7 cm, P = .004) and hip (109.8 ± 2.2 vs 110.9 ± 2.2 cm, P = .017) circumferences compared with baseline were also observed after the intervention. Thus, 2 weeks of SIT substantially improved a number of metabolic and vascular risk factors in overweight/obese sedentary men, highlighting the potential for this to provide an alternative exercise model for the improvement of vascular and metabolic health in this population.

What is best practice for training intensity and duration distribution in endurance athletes

Abstract: Successful endurance training involves the manipulation of training intensity, duration, and frequency, with the implicit goals of maximizing performance, minimizing risk of negative training outcomes, and timing peak fitness and performances to be achieved when they matter most. Numerous descriptive studies of the training characteristics of nationally or internationally competitive endurance athletes training 10 to 13 times per week seem to converge on a typical intensity distribution in which about 80% of training sessions are performed at low intensity (2 mM blood lactate), with about 20% dominated by periods of high-intensity work, such as interval training at approx. 90% VO2max. Endurance athletes appear to self-organize toward a high-volume training approach with careful application of high-intensity training incorporated throughout the training cycle. Training intensification studies performed on already well-trained athletes do not provide any convincing evidence that a greater emphasis on high-intensity interval training in this highly trained athlete population gives long-term performance gains. The predominance of low-intensity, long-duration training, in combination with fewer, highly intensive bouts may be complementary in terms of optimizing adaptive signaling and technical mastery at an acceptable level of stress.

High-intensity training versus traditional exercise interventions for promoting health.

Abstract: NYBO, L., E. SUNDSTRUP, M. D. JAKOBSEN, M. MOHR, T. HORNSTRUP, L. SIMONSEN, J. BULOW, M. B. RANDERS, J. J. NIELSEN, P. AAGAARD, and P. KRUSTRUP. High-Intensity Training versus Traditional Exercise Interventions for Pro- moting Health. Med. Sci. Sports Exerc., Vol. 42, No. 10, pp. 1951-1958, 2010. Purpose: The purpose of this study was to deter- mine the effectiveness of brief intense interval training as exercise intervention for promoting health and to evaluate potential benefits about common interventions, that is, prolonged exercise and strength training. Methods: Thirty-six untrained men were divided into groups that completed 12 wk of intense interval running (INT; total training time 40 minIwk j1 ), prolonged running (E150 minIwk j1 ), and strength training (E150 minIwk j1 ) or continued their habitual lifestyle without participation in physical training. Results: The improvement in cardiorespiratory fitness was superior in the INT (14% T 2% increase in VO2max) compared with the other two exercise interventions (7% T 2% and 3% T 2% increases). The blood glucose concentration 2 h after oral ingestion of 75 g of glucose was lowered to a similar extent after training in the INT (from 6.1 T 0.6 to 5.1 T 0.4 mM, P G 0.05) and the prolonged running group (from 5.6 T 1.5 to 4.9 T 1.1 mM, P G 0.05). In contrast, INT was less efficient than prolonged running for lowering the subjects' resting HR, fat percentage, and reducing the ratio between total and HDL plasma cholesterol. Furthermore, total bone mass and lean body mass remained unchanged in the INT group, whereas both these parameters were increased by the strength-training intervention. Conclusions: INT for 12 wk is an effective training stimulus for improvement of cardiorespiratory fitness and glucose tolerance, but in relation to the treatment of hyperlipidemia and obesity, it is less effective than prolonged training. Furthermore and in contrast

Training for intense exercise performance: high-intensity or high-volume training?

Abstract: Performance in intense exercise events, such as Olympic rowing, swimming, kayak, track running and track cycling events, involves energy contribution from aerobic and anaerobic sources. As aerobic energy supply dominates the total energy requirements after 75 s of near maximal effort, and has the greatest potential for improvement with training, the majority of training for these events is generally aimed at increasing aerobic metabolic capacity. A shortterm period (six to eight sessions over 2–4 weeks) of highintensity interval training (consisting of repeated exercise bouts performed close to or well above the maximal oxygen uptake intensity, interspersed with low-intensity exercise or complete rest) can elicit increases in intense exercise performance of 2–4% in well-trained athletes. The influence of high-volume training is less discussed, but its importance should not be downplayed, as high-volume training also induces important metabolic adaptations. While the metabolic adaptations that occur with high-volume training and high-intensity training show considerable overlap, the molecular events that signal for these adaptations may be different. A polarized approach to training, whereby 75% of total training volume is performed at low intensities, and 10–15% is performed at very high intensities, has been suggested as an optimal training intensity distribution for elite athletes who perform intense exercise events.

Recreational football as a health promoting activity: a topical review.

Abstract: The present review addresses the physiological demands during recreational football training and the effects on central health variables that influence the risk of life-style diseases of young and middle-aged men. Recent studies have established that recreational football, carried out as small-sided games can be characterized as having a high aerobic component with mean heart rates of 80-85% of maximum heart rate, which is similar to values observed for elite football players. In addition, the training includes multiple high-speed runs, sprints, turns, jumps and tackles, which provide a high impact on muscles and bones. Recreational football training in untrained men results in marked improvements in maximum aerobic power, blood pressure, muscle capillarization and intermittent exercise performance, and those effects are similar to interval training and more pronounced than moderate-intensity continuous running and strength training. Further, recreational football training enhances fat oxidation during exercise and results in a higher fat loss than interval training and strength training, and results in marked muscle hypertrophy and elevates bone mass, more than interval and continuous running. Taken together, recreational football appears to effectively stimulate musculoskeletal, metabolic and cardiovascular adaptations of importance for health and thereby reduces the risk of developing life-style diseases.

10 or 30-s sprint interval training bouts enhance both aerobic and anaerobic performance.

Abstract: We assessed whether 10-s sprint interval training (SIT) bouts with 2 or 4 min recovery periods can improve aerobic and anaerobic performance. Subjects (n = 48) were assigned to one of four groups [exercise time (s):recovery time (min)]: (1) 30:4, (2) 10:4, (3) 10:2 or (4) control (no training). Training was cycling 3 week(-1) for 2 weeks (starting with 4 bouts session(-1), increasing 1 bout every 2 sessions, 6 total). Pre- and post-training measures included: VO(2max), 5-km time trial (TT), and a 30-s Wingate test. All groups were similar pre-training and the control group did not change over time. The 10-s groups trained at a higher intensity demonstrated by greater (P < 0.05) reproducibility of peak (10:4 = 96%; 10:2 = 95% vs. 30:4 = 89%), average (10:4 = 84%; 10:2 = 82% vs. 30:4 = 58%), and minimum power (10:4 = 73%; 10:2 = 69%; vs. 30:4 = 40%) within each session while the 30:4 group performed ~2X (P < 0.05) the total work session(-1) (83-124 kJ, 4-6 bouts) versus 10:4 (38-58 kJ); 10:2 (39-59 kJ). Training increased TT performance (P < 0.05) in the 30:4 (5.2%), 10:4 (3.5%), and 10:2 (3.0%) groups. VO(2max) increased in the 30:4 (9.3%) and 10:4 (9.2%), but not the 10:2 group. Wingate peak power kg(-1) increased (P < 0.05) in the 30:4 (9.5%), 10:4 (8.5%), and 10:2 (4.2%). Average Wingate power kg(-1) increased (P < 0.05) in the 30:4 (12.1%) and 10:4 (6.5%) groups. These data indicate that 10-s (with either 2 or 4 min recovery) and 30-s SIT bouts are effective for increasing anaerobic and aerobic performance.

Short‐term sprint interval training increases insulin sensitivity in healthy adults but does not affect the thermogenic response to β‐adrenergic stimulation

Abstract: Sprint interval training (SIT) and traditional endurance training elicit similar physiological adaptations. From the perspective of metabolic function, superior glucose regulation is a common characteristic of endurance-trained adults. Accordingly, we have investigated the hypothesis that short-term SIT will increase insulin sensitivity in sedentary/recreationally active humans. Thirty one healthy adults were randomly assigned to one of three conditions: (1) SIT (n= 12): six sessions of repeated (4–7) 30 s bouts of very high-intensity cycle ergometer exercise over 14 days; (2) sedentary control (n= 10); (3) single-bout SIT (n= 9): one session of 4 × 30 s cycle ergometer sprints. Insulin sensitivity was determined (hyperinsulinaemic euglycaemic clamp) prior to and 72 h following each intervention. Compared with baseline, and sedentary and single-bout controls, SIT increased insulin sensitivity (glucose infusion rate: 6.3 ± 0.6 vs. 8.0 ± 0.8 mg kg−1 min−1; mean ±s.e.m.; P= 0.04). In a separate study, we investigated the effect of SIT on the thermogenic response to beta-adrenergic receptor (β-AR) stimulation, an important determinant of energy balance. Compared with baseline, and sedentary and single-bout control groups, SIT did not affect resting energy expenditure (EE: ventilated hood technique; 6274 ± 226 vs. 6079 ± 297 kJ day−1; P= 0.51) or the thermogenic response to isoproterenol (6, 12 and 24 ng (kg fat-free mass)−1 min−1: %ΔEE 11 ± 2, 14 ± 3, 23 ± 2 vs. 11 ± 1, 16 ± 2, 25 ± 3; P= 0.79). Combined data from both studies revealed no effect of SIT on fasted circulating concentrations of glucose, insulin, adiponectin, pigment epithelial-derived factor, non-esterified fatty acids or noradrenaline (all P > 0.05). Sixteen minutes of high-intensity exercise over 14 days augments insulin sensitivity but does not affect the thermogenic response to β-AR stimulation.

Effects of high-intensity aerobic interval training vs. moderate exercise on hemodynamic, metabolic and neuro-humoral abnormalities of young normotensive women at high familial risk for hypertension

Abstract: Exercise training has an important role in the prevention and treatment of hypertension, but its effects on the early metabolic and hemodynamic abnormalities observed in normotensive offspring of hypertensive parents (FH+) have not been studied We compared high-intensity interval (aerobic interval training, AIT) and moderate-intensity continuous exercise training (CMT) with regard to hemodynamic, metabolic and hormonal variables in FH+ subjects Forty-four healthy FH+ women (250+/-44 years) randomized to control (ConFH+) or to a three times per week equal-volume AIT (80-90% of VO(2MAX)) or CMT (50-60% of VO(2MAX)) regimen, and 15 healthy women with normotensive parents (ConFH-; 253+/-31 years) had their hemodynamic, metabolic and hormonal variables analyzed at baseline and after 16 weeks of follow-up Ambulatorial blood pressure (ABP), glucose and cholesterol levels were similar among all groups, but the FH+ groups showed higher insulin, insulin sensitivity, carotid-femoral pulse wave velocity (PWV), norepinephrine and endothelin-1 (ET-1) levels and lower nitrite/nitrate (NOx) levels than ConFH- subjects AIT and CMT were equally effective in improving ABP (P<005), insulin and insulin sensitivity (P<0001); however, AIT was superior in improving cardiorespiratory fitness (15 vs 8%; P<005), PWV (P<001), and BP, norepinephrine, ET-1 and NOx response to exercise (P<005) Exercise intensity was an important factor in improving cardiorespiratory fitness and reversing hemodynamic, metabolic and hormonal alterations involved in the pathophysiology of hypertension These findings may have important implications for the exercise training programs used for the prevention of inherited hypertensive disorder

Strength training versus aerobic interval training to modify risk factors of metabolic syndrome

Abstract: Metabolic syndrome is characterized by central obesity, elevated blood pressure, high fasting glucose and triglyceride levels, and low HDL levels. Regular physical activity can improve the metaboli...

Interval versus continuous training in individuals with chronic obstructive pulmonary disease- a systematic review

Abstract: Background In patients with chronic obstructive pulmonary disease (COPD), interval exercise has gained recent attention as a possible means of achieving greater physiological training effects compared with continuous exercise. The primary aim of this systematic review was to compare the effects of interval versus continuous training on peak oxygen uptake, peak power, 6 minute walk test (6MWT) distance and health-related quality of life in individuals with COPD. Methods Randomised controlled trials comparing the effects of interval versus continuous training in patients with COPD were identified after searches of six databases and reference lists of appropriate studies in May 2009. Two reviewers independently assessed study quality. Weighted mean differences (WMD) with 95% CIs were calculated using a random effects model for measures of exercise capacity and health-related quality of life. Results: Eight randomised controlled trials, with a total of 388 patients with COPD, met the inclusion criteria. No significant differences were found for peak power (WMD 1 W, 95% CI −1 to 3) or peak oxygen uptake (WMD −0.04 l/min, 95% CI −0.13 to 0.05) between interval and continuous training. The WMD for the Chronic Respiratory Questionnaire dyspnoea score was −0.2 units (95% CI −0.5 to 0.0). There was no difference in 6MWT distance between groups (WMD 4 m, 95% CI −15 to 23). Conclusions Interval and continuous training modalities did not differ in their effect on measures of exercise capacity or health-related quality of life. Interval training may be considered as an alternative to continuous training in patients with varying degrees of COPD severity.

Training with low muscle glycogen enhances fat metabolism in well-trained cyclists.

Abstract: Purpose: To determine the effects of training with low muscle glycogen on exercise performance, substrate metabolism, and skeletal muscle adaptation. Methods: Fourteen well-trained cyclists were pair-matched and randomly assigned to HIGH- or LOW-glycogen training groups. Subjects performed nine aerobic training (AT; 90 min at 70% V?O ) and nine high-intensity interval training sessions (HIT; 8 × 5-min efforts, 1-min recovery) during a 3-wk period. HIGH trained once daily, alternating between AT on day 1 and HIT the following day, whereas LOW trained twice every second day, first performing AT and then, 1 h later, performing HIT. Pretraining and posttraining measures were a resting muscle biopsy, metabolic measures during steady-state cycling, and a time trial. Results: Power output during HIT was 297 ± 8 W in LOW compared with 323 ± 9 W in HIGH ( < 0.05); however, time trial performance improved by ~10% in both groups ( < 0.05). Fat oxidation during steady-state cycling increased after training in LOW (from 26 ± 2 to 34 ± 2 µmol·kg ·min , < 0.01). Plasma free fatty acid oxidation was similar before and after training in both groups, but muscle-derived triacylglycerol oxidation increased after training in LOW (from 16 ± 1 to 23 ± 1 µmol·kg ·min , < 0.05). Training with low muscle glycogen also increased s-hydroxyacyl-CoA-dehydrogenase protein content ( < 0.01). Conclusions: Training with low muscle glycogen reduced training intensity and, in performance, was no more effective than training with high muscle glycogen. However, fat oxidation was increased after training with low muscle glycogen, which may have been due to the enhanced metabolic adaptations in skeletal muscle.

Effect of preseason concurrent muscular strength and high-intensity interval training in professional soccer players.

Abstract: This study examined the effect of concurrent muscular strength and high-intensity running interval training on professional soccer players' explosive performances and aerobic endurance. Thirty-nine players participated in the study, where both the experimental group (EG, n = 20) and control group (CG, n = 19) participated in 8 weeks of regular soccer training, with the EG receiving additional muscular strength and high-intensity interval training twice per week throughout. Muscular strength training consisted of 4 sets of 6RM (repetition maximum) of high-pull, jump squat, bench press, back half squat, and chin-up exercises. The high-intensity interval training consisted of 16 intervals each of 15-second sprints at 120% of individual maximal aerobic speed interspersed with 15 seconds of rest. EG significantly increased (p < or = 0.05) 1RM back half squat and bench press but showed no changes in body mass. Within-subject improvement was significantly higher (p < or = 0.01) in the EG compared with the CG for vertical jump height, 10-m and 30-m sprint times, distances covered in the Yo-Yo Intermittent Recovery Test and maximal aerobic speed test, and maximal aerobic speed. High-intensity interval running can be concurrently performed with high load muscular strength training to enhance soccer players' explosive performances and aerobic endurance.

Improving Acceleration and Repeated Sprint Ability in Well-Trained Adolescent Handball Players: Speed Versus Sprint Interval Training

Abstract: Purpose: The aim of the current study was to compare the effects of speed/agility (S/A) training with sprint interval training (SIT) on acceleration and repeated sprint ability (RSA) in well-trained male handball players. Methods: In addition to their normal training program, players performed either S/A (n = 7) or SIT (n = 7) training for 4 wk. Speed/agility sessions consisted of 3 to 4 series of 4 to 6 exercises (eg, agility drills, standing start and very short sprints, all of <5 s duration); each repetition and series was interspersed with 30 s and 3 min of passive recovery, respectively. Sprint interval training consisted of 3 to 5 repetitions of 30-s all-out shuttle sprints over 40 m, interspersed with 2 min of passive recovery. Pre- and posttests included a countermovement jump (CMJ), 10-m sprint (10m), RSA test and a graded intermittent aerobic test (30-15 Intermittent Fitness Test, V IFT ). Results: S/A training produced a very likely greater improvement in 10-m sprint (+4.6%, 90% CL 1.2 to 7.8), best (+2.7%, 90% CL 0.1 to 5.2) and mean (+2.2%, 90% CL –0.2 to 4.5) RSA times than SIT (all effect sizes [ES] greater than 0.79). In contrast, SIT resulted in an almost certain greater improvement in V IFT compared with S/A (+5.2%, 90% CL 3.5 to 6.9, with ES = –0.83). Conclusion: In well-trained handball players, 4 wk of SIT is likely to have a moderate impact on intermittent endurance capacity only, whereas S/A training is likely to improve acceleration and repeated sprint performance.

High-intensity interval training increases SIRT1 activity in human skeletal muscle

Abstract: The effects of training on silent mating-type information regulator 2 homolog 1 (SIRT1) activity and protein in relationship to peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) and mitochondrial content were determined in human skeletal muscle. Six weeks of high-intensity interval training ( approximately 1 h of 10 x 4 min intervals at 90% peak oxygen consumption separated by 2 min rest, 3 days per week) increased maximal activities of mitochondrial enzymes in skeletal muscle by 28% to 36% (citrate synthase, beta-hydroxyacyl-coenzyme A dehydrogenase, and cytochrome c oxidase subunit IV) and PGC-1alpha protein (16%) when measured 4 days after training. Interestingly, total muscle SIRT1 activity (31%) and activity per SIRT1 protein (58%) increased despite decreased SIRT1 protein (20%). The present data demonstrate that exercise-induced mitochondrial biogenesis is accompanied by elevated SIRT1 activity in human skeletal muscle.

Acute signalling responses to intense endurance training commenced with low or normal muscle glycogen.

Abstract: We have previously demonstrated that well-trained subjects who completed a 3 week training programme in which selected high-intensity interval training (HIT) sessions were commenced with low muscle glycogen content increased the maximal activities of several oxidative enzymes that promote endurance adaptations to a greater extent than subjects who began all training sessions with normal glycogen levels. The aim of the present study was to investigate acute skeletal muscle signalling responses to a single bout of HIT commenced with low or normal muscle glycogen stores in an attempt to elucidate potential mechanism(s) that might underlie our previous observations. Six endurance-trained cyclists/triathletes performed a 100 min ride at approximately 70% peak O(2) uptake (AT) on day 1 and HIT (8 x 5 min work bouts at maximal self-selected effort with 1 min rest) 24 h later (HIGH). Another six subjects, matched for fitness and training history, performed AT on day 1 then 1-2 h later, HIT (LOW). Muscle biopsies were taken before and after HIT. Muscle glycogen concentration was higher in HIGH versus LOW before the HIT (390 +/- 28 versus 256 +/- 67 micromol (g dry wt)(1)). After HIT, glycogen levels were reduced in both groups (P < 0.05) but HIGH was elevated compared with LOW (229 +/- 29 versus 124 +/- 41 micromol (g dry wt)(1); P < 0.05). Phosphorylation of 5 AMP-activated protein kinase (AMPK) increased after HIT, but the magnitude of increase was greater in LOW (P < 0.05). Despite the augmented AMPK response in LOW after HIT, selected downstream AMPK substrates were similar between groups. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) was unchanged for both groups before and after the HIT training sessions. We conclude that despite a greater activation AMPK phosphorylation when HIT was commenced with low compared with normal muscle glycogen availability, the localization and phosphorylation state of selected downstream targets of AMPK were similar in response to the two interventions.

Effect of high- and low-intensity exercise and metabolic acidosis on levels of GH, IGF-I, IGFBP-3 and cortisol.

Abstract: Objective The purpose of the present study was to examine the acute hormonal response of a short term high-intensity training (HIT) versus a high volume endurance training (HVT) and to determine the contribution of the metabolic acidosis as a stimulus for possibly different reactions of circulating hGH, IGF-1, IGFBP-3 and cortisol. Design Eleven subjects participated in three experimental trials separated by one week. Two times subjects performed four 30s maximal effort exercise bouts on a cycle ergometer separated by 5min rest each. Before the exercise subjects either received (single-blinded) bicarbonate (HIT (B)) or a placebo (HIT (P)). The third exercise trail consisted of a constant load exercise for 1h at 50% VO 2 max (HVT). Venous blood samples were taken under resting conditions, 10min, 60min and 240min after each exercise condition to determine hGH, IGF-1, IGFBP-3 and cortisol serum concentrations. Capillary blood samples were taken to determine lactate concentrations and blood gas parameters. Results Power output, mean lactate concentrations and mean pH values were significantly higher during HIT (B) compared to HIT (P). Serum cortisol and hGH concentrations were significantly increased 10min post exercise in both HIT interventions. IGFBP-3 was only significantly increased after HIT (P), whereas IGF-1 was not affected by any of the interventions. HVT showed no significant effects on cortisol, hGH, IGF-1 and IGFBP-3 levels. Additionally it was shown that the diminished acidosis during HIT (B) attenuates the cortisol and hGH response. Conclusions The present study suggests that HIT/acidosis is a stimulus for exercise-induced cortisol/hGH secretion, but not for IGF-1 and IGFBP-3 under these experimental conditions. These findings might be relevant for arrangements of interval training, due to the fact that active or passive recovery during rest periods influence the acid base status and may therefore influence the hormonal response.

High-intensity interval training improves VO2peak, maximal lactate accumulation, time trial and competition performance in 9–11-year-old swimmers

Abstract: Training volume in swimming is usually very high when compared to the relatively short competition time. High-intensity interval training (HIIT) has been demonstrated to improve performance in a relatively short training period. The main purpose of the present study was to examine the effects of a 5-week HIIT versus high-volume training (HVT) in 9-11-year-old swimmers on competition performance, 100 and 2,000 m time (T(100 m) and T(2,000 m)), VO(2peak) and rate of maximal lactate accumulation (Lac(max)). In a 5-week crossover study, 26 competitive swimmers with a mean (SD) age of 11.5 ± 1.4 years performed a training period of HIIT and HVT. Competition (P < 0.01; effect size = 0.48) and T(2,000 m) (P = 0.04; effect size = 0.21) performance increased following HIIT. No changes were found in T(100 m) (P = 0.20). Lac(max) increased following HIIT (P < 0.01; effect size = 0.43) and decreased after HVT (P < 0.01; effect size = 0.51). VO(2peak) increased following both interventions (P < 0.05; effect sizes = 0.46-0.57). The increases in competition performance, T(2,000 m), Lac(max) and VO(2peak) following HIIT were achieved in significantly less training time (~2 h/week).

Impaired cardiac function among obese adolescents: effect of aerobic interval training.

Abstract: Objectives To measure cardiac function before and after 3 months of aerobic interval training in obese adolescents and to compare the findings with those in lean counterparts. Design Exercise intervention study. Cardiac function was assessed by echocardiography and maximal oxygen uptake by ergospirometry. Setting The obese adolescents were referred from general practice to the St Olav University Hospital, Trondheim, Norway, and the control group was recruited from 2 schools. Participants Ten obese adolescents (mean [SD] age, 14.8 [1.2] years; mean [SD] body mass index {BMI; calculated as weight in kilograms divided by height in meters squared}, 33.5 [4.3]) and 10 lean counterparts (mean [SD] age, 14.9 [1.3] years; mean [SD] BMI, 20.4 [3.0]) participated. Intervention Aerobic interval training (4 × 4 minutes at 90% of maximal heart rate, 40 minutes of training in total) was performed twice per week for 13 weeks among the obese adolescents, whereas the lean counterparts only performed the tests. Main Outcome Measures Left ventricular end-diastolic volume, stroke volume, and maximal oxygen uptake. Results Maximal oxygen uptake was 41.4% lower among the obese adolescents compared with the lean counterparts, but the maximal oxygen uptake increased by 8.6% (P = .008) after intervention. Obese adolescents initially had 7.8% and 14.5% lower left ventricular end-diastolic and stroke volumes, 21.3% reduced global strain rate and 16.3% global strain, reduced mitral annulus excursion and systolic/diastolic tissue velocity, longer isovolumic relaxation time, and longer deceleration time compared with the lean counterparts. No group difference was observed after the intervention. Aerobic interval training increased the ejection fraction but was lower compared with the lean counterparts. Aerobic interval training reduced fat content by 2.0% (P = .005) among the obese adolescents. Conclusions Aerobic interval training almost restored an impaired systolic and diastolic cardiac function among obese adolescents when compared with lean counterparts. These results may have implications for future treatment programs for obese adolescents. Trial Registration clinicaltrials.gov Identifier:NCT00184236

The effects of theaflavin-enriched black tea extract on muscle soreness, oxidative stress, inflammation, and endocrine responses to acute anaerobic interval training: a randomized, double-blind, crossover study.

Abstract: Muscle soreness and decreased performance often follow a bout of high-intensity exercise. By reducing these effects, an athlete can train more frequently and increase long-term performance. The purpose of this study is to examine whether a high-potency, black tea extract (BTE) alters the delayed onset muscle soreness (DOMS), oxidative stress, inflammation, and cortisol (CORT) responses to high-intensity anaerobic exercise. College-age males (N = 18) with 1+ yrs of weight training experience completed a double-blind, placebo-controlled, crossover study. Subjects consumed the BTE (1,760 mg BTE·d-1) or placebo (PLA) for 9 days. Each subject completed two testing sessions (T1 & T2), which occurred on day 7 of the intervention. T1 & T2 consisted of a 30 s Wingate Test plus eight 10 s intervals. Blood samples were obtained before, 0, 30 & 60 min following the interval sessions and were used to analyze the total to oxidized glutathione ratio (GSH:GSSG), 8-isoprostane (8-iso), CORT, and interleukin 6 (IL-6) secretion. DOMS was recorded at 24 & 48 h post-test using a visual analog scale while BTE or PLA continued to be administered. Significance was set at P < 0.05. Compared to PLA, BTE produced significantly higher average peak power (P = 0.013) and higher average mean power (P = 0.067) across nine WAnT intervals. BTE produced significantly lower DOMS compared to PLA at 24 h post test (P < 0.001) and 48 h post test (P < 0.001). Compared to PLA, BTE had a slightly higher GSH:GSSG ratio at baseline which became significantly higher at 30 and 60 min post test (P < 0.002). AUC analysis revealed BTE to elicit significantly lower GSSG secretion (P = 0.009), significantly higher GSH:GSSG ratio (P = 0.001), and lower CORT secretion (P = 0.078) than PLA. AUC analysis did not reveal a significant difference in total IL-6 response (P = 0.145) between conditions. Consumption of theaflavin-enriched black tea extract led to improved recovery and a reduction in oxidative stress and DOMS responses to acute anaerobic intervals. An improved rate of recovery can benefit all individuals engaging in high intensity, anaerobic exercise as it facilitates increased frequency of exercise.

Effectiveness of Interval Exercise Training in Patients with COPD.

Abstract: Physical training is beneficial and should be included in the comprehensive management of all patients with COPD independently of disease severity. Different rehabilitative strategies and training modalities have been proposed to optimize exercise tolerance. Interval exercise training has been used as an effective alternative modality to continuous exercise in patients with moderate and severe COPD.Although in healthy elderly individuals and patients with chronic heart failure there is evidence that this training modality is superior to continuous exercise in terms of physiological training effects, in patients with COPD, there is not such evidence. Nevertheless, in patients with COPD application of interval training has been shown to be equally effective to continuous exercise as it induces equivalent physiological training effects but with less symptoms of dyspnea and leg discomfort during training.The main purpose of this review is to summarize previous studies of the effectiveness of interval training in COPD and also to provide arguments in support of the application of interval training to overcome the respiratory and peripheral muscle limiting factors of exercise capacity. To this end we make recommendations on how best to implement interval training in the COPD population in the rehabilitation setting so as to maximize training effects.

The effects of a pre-workout supplement containing caffeine, creatine, and amino acids during three weeks of high-intensity exercise on aerobic and anaerobic performance

Abstract: A randomized, single-blinded, placebo-controlled, parallel design study was used to examine the effects of a pre-workout supplement combined with three weeks of high-intensity interval training (HIIT) on aerobic and anaerobic running performance, training volume, and body composition. Twenty-four moderately-trained recreational athletes (mean ± SD age = 21.1 ± 1.9 yrs; stature = 172.2 ± 8.7 cm; body mass = 66.2 ± 11.8 kg, VO2max = 3.21 ± 0.85 l·min-1, percent body fat = 19.0 ± 7.1%) were assigned to either the active supplement (GT, n = 13) or placebo (PL, n = 11) group. The active supplement (Game Time®, Corr-Jensen Laboratories Inc., Aurora, CO) was 18 g of powder, 40 kcals, and consisted of a proprietary blend including whey protein, cordyceps sinensis, creatine, citrulline, ginseng, and caffeine. The PL was also 18 g of powder, 40 kcals, and consisted of only maltodextrin, natural and artificial flavors and colors. Thirty minutes prior to all testing and training sessions, participants consumed their respective supplements mixed with 8-10 oz of water. Both groups participated in a three-week HIIT program three days per week, and testing was conducted before and after the training. Cardiovascular fitness (VO2max) was assessed using open circuit spirometry (Parvo-Medics TrueOne® 2400 Metabolic Measurement System, Sandy, UT) during graded exercise tests on a treadmill (Woodway, Pro Series, Waukesha, WI). Also, four high-speed runs to exhaustion were conducted at 110, 105, 100, and 90% of the treadmill velocity recorded during VO2max, and the distances achieved were plotted over the times-to-exhaustion. Linear regression was used to determine the slopes (critical velocity, CV) and y-intercepts (anaerobic running capacity, ARC) of these relationships to assess aerobic and anaerobic performances, respectively. Training volumes were tracked by summing the distances achieved during each training session for each subject. Percent body fat (%BF) and lean body mass (LBM) were assessed with air-displacement plethysmography (BOD POD®, Life Measurement, Inc., Concord, CA). Both GT and PL groups demonstrated a significant (p = 0.028) increase in VO2max from pre- to post-training resulting in a 10.3% and 2.9% improvement, respectively. CV increased (p = 0.036) for the GT group by 2.9%, while the PL group did not change (p = 0.256; 1.7% increase). ARC increased for the PL group by 22.9% and for the GT group by 10.6%. Training volume was 11.6% higher for the GT versus PL group (p = 0.041). %BF decreased from 19.3% to 16.1% for the GT group and decreased from 18.0% to 16.8% in the PL group (p = 0.178). LBM increased from 54.2 kg to 55.4 kg (p = 0.035) for the GT group and decreased from 52.9 kg to 52.4 kg in the PL group (p = 0.694). These results demonstrated improvements in VO2max, CV, and LBM when GT is combined with HIIT. Three weeks of HIIT alone also augmented anaerobic running performance, VO2max and body composition.

Mitochondrial gene expression in elite cyclists: effects of high-intensity interval exercise.

Abstract: Little is known about the effect of training on genetic markers for mitochondrial biogenesis in elite athletes. We tested the hypothesis that low-volume sprint interval exercise (SIE) would be as effective as high-volume interval exercise (IE). Ten male cyclists competing on national elite level (W (max) 403 ± 13 W, VO(2peak) 68 ± 1 mL kg(-1) min(-1)) performed two interval exercise protocols: 7 × 30-s "all-out" bouts (SIE) and 3 × 20-min bouts at ~87% of VO(2peak) (IE). During IE, the work was eightfold larger (1,095 ± 43 vs. 135 ± 5 kJ) and the exercise duration 17 times longer (60 vs. 3.5 min) than during SIE. Muscle samples were taken before and 3 h after exercise. The mRNA of upstream markers of mitochondrial biogenesis [peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1α), PGC-1α-related coactivator (PRC) and peroxisome proliferator-activated receptor δ (PPARδ)] increased to the same extent after SIE and IE (6-, 1.5- and 1.5-fold increase, respectively). Of the downstream targets of PGC-1α, mitochondrial transcription factor A (Tfam) increased only after SIE and was significantly different from that after IE (P < 0.05), whereas others increased to the same extent (pyruvate dehydrogenase kinase, PDK4) or was unchanged (nuclear respiratory factor 2, NRF2). We conclude that upstream genetic markers of mitochondrial biogenesis increase in a similar way in elite athletes after one exercise session of SIE and IE. However, since the volume and duration of work was considerably lower during SIE and since Tfam, the downstream target of PGC-1α, increased only after SIE, we conclude that SIE might be a time-efficient training strategy for highly trained individuals.

Experiencing flow in different types of physical activity intervention programs: three randomized studies.

Abstract: This study explores whether inactive individuals can experience flow, a rewarding, psychological state, during an exercise intervention and if there are differences according to the type of intervention they perform. Furthermore, the study investigates if experiencing flow is connected to physiological improvements attained during the exercise intervention. The 12- to 16-week interventions included six randomized intervention groups, two female and four male groups performing continuous running, football, interval running and strength training. The results indicate that all six randomized exercise intervention groups experience rather high levels of flow regardless of whether the intervention is a team or individual sport. Differences in experiencing flow, worry and exertion as well as physiological improvements could be found for the different types of sports and the two genders, with the male football group having the highest score for physiological improvement and the lowest score for worry. A connection between experiencing flow and physiological improvement could not be found. Future research should investigate the influence that the participant's gender and also the type of sport have on experiencing flow, worry and perceived exertion. Furthermore, it should be investigated whether experiencing flow is linked to the long-term compliance of regular physical activity.

Six Weeks of High-intensity Interval Training With and Without β-alanine Supplementation for Improving Cardiovascular Fitness in Women

Abstract: Walter, AA, Smith, AE, Kendall, KL, Stout, JR, and Cramer, JT. Six weeks of high-intensity interval training with and without β-alanine supplementation for improving cardiovascular fitness in women. J Strength Cond Res 24(5): 1199-1207, 2010-The purpose of the present study was to evaluate t

Just HIT it! A time-efficient exercise strategy to improve muscle insulin sensitivity

Abstract: Muscle insulin resistance plays a major pathophysiological role in type 2 diabetes and is associated with major public health problems, including obesity and coronary artery disease. Given the dire consequences associated with sedentary living (in terms of individual disease risk and the economic burden on health care systems), the promotion of an active lifestyle is an international priority. Public health guidelines generally recommend that adults perform at least 150 min week−1 of ‘moderate-intensity’ aerobic physical activity (typically defined as 40–60% of maximal aerobic power ()) or a minimum of 60 min week−1 of ‘vigorous-intensity’ exercise (>60%) to promote health. These recommendations are based on robust evidence that suggests endurance training reduces the risk for chronic disease through the same general mechanisms that lead to improved athletic performance; for example, exercise-induced increases in muscle oxidative and glucose transport capacities have been linked to improved insulin sensitivity and glycaemic control. Unfortunately, most people fail to meet even the minimum physical activity guidelines, citing ‘lack of time’ as the major barrier to regular exercise participation. Innovations in exercise prescription that show benefits despite a minimal time commitment therefore represent a valuable strategy to encourage physical activity participation and reduce the risk of chronic diseases. A growing body of evidence suggests that high-intensity interval training (HIT) induces numerous physiological adaptations that are similar to traditional endurance training despite a lower total exercise volume and training time commitment (Gibala & McGee, 2008). Low-volume HIT is characterized by brief repeated ‘bursts’ of vigorous exercise interspersed with periods of rest or low-intensity exercise for recovery. A common model employed in many HIT studies is the Wingate test, which consists of a 30 s ‘all-out’ cycling effort against a standardized resistance. In a typical training session, subjects complete four to six Wingate tests interspersed with 4 min of rest, for a total of only 2 to 3 min of maximal exercise spread over a ∼15–30 min period. As little as six sessions of this low-volume HIT protocol over 2 weeks is a potent stimulus to increase muscle oxidative and glucose transport capacities (Gibala & McGee, 2008), but little is known about the effect of this type of training on common health status markers linked to disease risk. In a recent issue of The Journal of Physiology, Richards et al. (2010) report that a Wingate-based HIT protocol consisting of only 16 min of all-out cycling over 14 days improved insulin sensitivity in previously sedentary or recreationally active young adults. Babraj and colleagues (2009) previously provided indirect evidence of improved insulin sensitivity based on oral glucose tolerance tests (OGTT) performed before and several days after an identical HIT protocol. However, the data from Richards et al. (2010) are more compelling, since insulin sensitivity was determined using the hyperinsulinaemic euglycaemic clamp technique, which is widely accepted as the reference standard for direct measurement in humans. Short-term HIT would not be expected to influence body composition and Richards et al. (2010) reported no change in several circulatory markers linked to insulin action, providing support for their conclusion that skeletal muscle adaptations probably contributed to the improved insulin sensitivity. As recognized by the authors, an important question pertinent to studies of this sort is whether the change in insulin sensitivity is due to training per se, or to the preceding exercise bout. While acute exercise effects are detectable for up to 48 h, the rigorous study design by Richards et al. (2010) suggests that the improved insulin sensitivity after HIT was a training-induced effect. Post-training measurements were made 72 h after the final training session, and no change in insulin sensitivity was observed in a control group that performed a single bout of Wingate-based exercise. However, the results are in contrast to a recent study (Whyte et al. 2010) that reported improved insulin sensitivity based on OGTT results 24 but not 72 h following a similar HIT training protocol in overweight and obese men. It has been suggested that the insulin-sensitizing effects of this type of exercise may be attenuated in obese and/or insulin-resistant adults and additional work is needed to clarify the effectiveness of HIT in different populations. Wingate tests require a specialized cycle ergometer and the ‘all-out’ maximal effort necessitates an extremely high level of subject motivation. Therefore, it may not be safe or practical to implement this form of training in the general population. A recent study (Little et al. 2010) evaluated whether a more practical model of low-volume HIT could elicit metabolic and performance adaptations similar to Wingate-based HIT studies. The modified protocol involved eight to twelve 1 min intervals at an intensity that corresponded to ∼100% with 75 s of rest in between. While still a demanding form of exercise, the absolute work intensity corresponded to less than half of that achieved during an all-out Wingate test. The protocol was also time efficient in that only ∼10 min of exercise was performed over a 15–25 min period during each training session. Similar to Wingate-based HIT, six sessions of this modified HIT protocol over 2 weeks was a sufficient stimulus to increase skeletal muscle oxidative capacity and GLUT4 protein content. Unpublished work from our laboratory shows this HIT model is well tolerated and reduces hyperglycaemia in people with type 2 diabetes. Additional studies are needed to resolve whether low-volume HIT is a realistic, time-efficient exercise alternative to reduce the risk of metabolic disease in various populations.