Period Of High-intensity Interval Training Research Articles

Comparison of Water-Based and Land-Based High-Intensity Interval Training Effects on Aerobic Capacity and Spinal Stabilization

The purpose of the study is to examine the effects of a two-week period of high-intensity interval training (HIIT) in water and land-based running on aerobic capacity and spinal stabilization. Forty-one healthy young participants were divided into water-based exercise, land-based exercise, and control groups. Aerobic capacity was measured with 20-m Shuttle Run Test, and spinal stabilization was tested with 60° Flexion test and Sorensen test. Water and land-based exercise groups performed six sessions of HIIT program for two weeks. A significant improvement in aerobic capacity and spinal stabilization was found between the baseline and after two-week evaluations in both the water and land based HIIT exercise groups (p

Investigation of an Increase in the Expression of the Mir146a Gene in The Hippocampus and a Decrease in the Levels of Blood Sugar, Insulin, and Insulin Resistance in Elderly Diabetic Rats after a Period of High-Intensity Interval Training

Introduction: MicroRNAs have been reported as potentially valuable biomarkers for various ‎diseases, including diabetes, heart diseases, neurological diseases, and age-related diseases. The ‎present study aimed to investigate the effect of 8 weeks of intense intermittent exercise on the ‎expression of mir146a, blood sugar, insulin, and insulin resistance in the hippocampus of aged diabetic male rats. Method: This study was performed on 40 male Wistar rats aged 18-21 months with an average weight of ‎‎280±20 g. After becoming diabetic through streptozotocin solution, they were ‎randomly divided into 4 groups, including 1) healthy high-intensity interval training (HIIT) exercise, 2) healthy control, 3) diabetic HIIT exercise, and 4) diabetic control. It should be mentioned that each group included 10 rats. The exercise groups exercised 5 days a week ‎according to the HIIT programs for 8 weeks. The collected data were analyzed using GraphPad Prism software (version 8) at a significance level of P<0.05. Results: The results showed that 8 weeks of HIIT exercise increased the ‎expression of mir146a in both of the exercise groups, compared to the diabetic control ‎group (P<0.001). Moreover, the blood sugar, insulin, and insulin resistance levels significantly decreased in the diabetic exercise, healthy HIIT exercise, ‎‎and healthy control ‎groups, compared to the diabetic control group (P<0.001).‎ Conclusion: It can be concluded that 8 weeks of HIIT training, which increased the expression of mir146a, can reduce neuronal destruction in the hippocampus region. Moreover, it can be used as a suitable non-therapeutic mechanism for diabetics to prevent or reduce damage in this brain region that is related to cognitive abilities

Does Becoming Fit Mean Feeling (f)it? A Comparison of Physiological and Experiential Fitness Data From the iReAct Study.

Regular exercise fosters fitness-enhancing benefits. We assume that exercise interventions become successful and sustainable if physiological benefits of exercise are also subjectively perceivable. The goal of this study was to examine how young inactive adults physiologically respond to an exercise intervention and how those responses are subjectively experienced. Furthermore, we aimed to assess whether the sequence of two distinct endurance-based exercise modes has an impact on physiological and subjectively experienced physical fitness. Thirty-one young inactive adults were assessed for this substudy of the larger iReAct study. Participants were randomly assigned to a high-intensity interval training (HIIT) or a moderate-intensity continuous training (MICT) group for 6 weeks and subsequently switched groups for a second training period. Physiological fitness data was collected at baseline, follow-up I, and follow-up II using a graded cardiopulmonary exercise test. Subjectively reconstructed (i.e., retrospective constructions) experiences relating to physical fitness were assessed at follow-up II using a biographical mapping method. A repeated-measures one-way ANOVA on each training group was performed to see whether physiological and subjectively experienced fitness differed across training periods. The rate of change between all variables was calculated for the first and the second training period in order to compare the agreement between physiological and subjective fitness improvements. Participants increased their fitness across the intervention period both physiologically and subjectively. However, the rate of change depended on the sequence of the two training modes. While VO2max increased significantly in both training periods in the MICT-HIIT sequence, a significant increase in VO2max in the HIIT-MICT sequence was only observed in the HIIT period. Participants similarly perceived those increases subjectively in their exercise-related physical fitness, although they experienced a significant decrease in the second period of the HIIT-MICT sequence. For subjectively perceived physical fitness relating to everyday activities, significant increases were only observed for the first period of the MICT-HIIT sequence. Young inactive adults can improve both their physiological and their subjectively perceived fitness through regular exercise. However, exercise modes and their sequence can make a substantial difference regarding measured and perceived physical fitness. Additionally, despite a favorable tendency toward HIIT over MICT, inter- and intra-individual variability, particularly in the subjective experiences of fitness, reiterates the necessity of individualized approaches to exercise.

The Effect of Hydroethanolic Extract of Pomegranate Peels and High-intense Interval Training on C-reactive Protein, Catalase and Superoxide Dismutase in Rats

Aims: Heavy exercise can damage the immune system by oxidative stress. The role of herbal supplements during and after strenuous exercise is unknown. Therefore, the present study aimed to determine hydroethanolic extract of pomegranate peels and a period of high-intensity interval training on the C-reactive protein and antioxidant enzyme activity in rats. Methods & Materials: This research was an experimental study. The statistical population was rats, of which 36 Wistar rats were randomly selected and were divided into 4 groups (control, hydroethanolic extract of pomegranate peels, high-intensity interval training, and hydroethanolic extract of pomegranate peels + high-intensity interval training). After 8 weeks of interval training and supplementation, blood samples were taken from the rats. Then, the C-reactive protein and the activity of the antioxidant enzymes of superoxide dismutase and catalase were assessed by 1-way analysis of variance. Findings: The results showed that in the group of hydroethanolic extract of pomegranate peels + high-intensity interval training, the superoxide dismutase (P=0.000) and catalase (P=0.003) significantly increased, and the C-reactive protein (P=0.002) decreased. Tukey’s test confirmed the significance of these changes in the hydroethanolic extract of pomegranate peels+high-intensity interval training compared to the control group. Conclusion: The combination of high-intensity interval training and hydroethanolic extract of pomegranate peels could strengthen the immune system, potentially enhances athletic performance, and accelerates recovery after exercises. The hydroethanolic extract of pomegranate peels and high-interval training synergistically boost the immune system and increase physical endurance.

Reproducible improvement in endothelial function following two separate periods of high-intensity interval training in young men.

High-intensity interval training (HIIT) can improve vascular function, as assessed by brachial artery flow-mediated dilation (FMD). However, when separated by a period of detraining, the reproducibility of FMD responses to repeated periods of HIIT is unknown. The purpose of this study was to determine the group mean and intraindividual reproducibility of FMD responses to two 4-wk periods of HIIT, separated by 3 mo of detraining. Thirteen healthy, recreationally active men (21 ± 2 yr) completed the study. Each 4-wk HIIT period included 40 min of treadmill training four times/week. Each training session included four 7-min intervals: 4 min at 90%-95% heart rate maximum (HRmax) and 3 min at 70%-75% HRmax. Vascular (FMD) and cardiorespiratory fitness (maximal oxygen consumption [V̇o2max]) assessments were conducted before and following each 4-wk training period. Training resulted in significant improvements in V̇o2max (P < 0.001). Training also improved FMD (P < 0.001), with no differences between periods (P = 0.394), even after controlling for changes in baseline diameter and the shear rate stimulus. There was a significant, moderate relationship between the change in FMD in HIIT period 1 versus period 2 [R2 = 0.493, P = 0.011, intraclass correlation coefficient: 0.600, coefficient of variation: 17.3%]. Consecutive periods of HIIT separated by detraining resulted in similar improvements in FMD at the group level, and individual FMD changes in period 1 of HIIT predicted FMD changes in response to period 2. Considered alongside substantial between-participant variability in magnitude of FMD improvement, this suggests that there are reproducible, interindividual differences in the potential to improve vascular function with HIIT.NEW & NOTEWORTHY This is the first study examining endothelial function [flow-mediated dilation (FMD)] following repeated periods of high-intensity interval training (HIIT). Two periods of HIIT separated by detraining resulted in reproducible group-level improvements in FMD. Despite considerable between-subject variability in FMD adaptation, individual FMD changes with the first HIIT period predicted FMD changes in the second period. This indicates the existence of reproducible between-subject differences in susceptibility to FMD improvement with HIIT.

The Effect of Detraining High Intensity Interval Training on the Expression of AKT1 and mTORc1 Genes in the Left Ventricle of Diabetic Rats

Objective: The aim of this study was to investigate the effect of 6 weeks of detraining after 12 weeks of high intensity interval training (HIIT) on the expression of AKT1 and mTORc1 genes in the left ventricle of wistar diabetic rats. Materials and Methods: Twenty-eight wistar male rats were selected as the study sample and were divided in four groups of healthy control, diabetic control, diabetic HIIT and diabetic HIIT + detraining. The HIIT period was 12 weeks and the detraining period was 6 weeks. Each session consisted of 30 minutes, which included running on a treadmill with one-minute repetitions and a two-minute active recovery between them. To measure AKT1 mRNA and mTORc1 mRNA by RT-Real time PCR, a single-step single step SYBR TAKARA kits from Takara Company was used according to the company's instruction. Results: HIIT caused a significant increase in AKT1 gene expression (P-value= 0.001). AKT1 decreased with detraining that was not significant (P-value= 0.34) but it was still significantly higher than before training (P-value= 0.017). HIIT caused a significant increase in mTORc1 gene expression (P-value= 0.001) and although it decreased with detraining (P-value= 0.15) and it was no significantly higher than before training (P-value= 0.19). Conclusion: HIIT led to increased expression of AKT1 and mTORc1 genes in type 2 diabetic rats, while also producing favorable changes in the cardiac structure of these rats. Also, 6 weeks of detraining did somewhat reduce these favorable changes.

The effects of human sera conditioned by high-intensity exercise sessions and training on the tumorigenic potential of cancer cells.

There is growing evidence of an association between physical activity and a reduced risk of cancer and cancer recurrence. The aim of this study was to assess the effects of exercise-conditioned human serum (HS) effects on the proliferative and tumorigenic potential of triple-negative breast cancer (TNBC) and prostate cancer (PC) cells. Moreover, modulated mechanisms and several physiological factors that can predict exercise effects were investigated. Thirty healthy sedentary subjects were recruited for the study. The subjects performed two high-intensity endurance cycling (HIEC) sessions before and after a nine-week period of high-intensity interval training (HIIT). Cell tumorigenic capacity affected by HS collected before (t0), immediately after (t1), 4h (t2), and 24h (t3) after the HIEC sessions was evaluated by in vitro three-dimensional colony formation. The modulation of molecular pathways was analyzed by western blotting and qPCR in TNBC and PC cells, and in TNBC xenografts in exercised mice. All of the HIEC-conditioned HS (t1, t2, and t3) markedly impacted the proliferative and the microtumor-forming capacity of both TNBC and PC cell lines, while the HS collected from the subjects at rest did not. Modulation of the Hippo and Wnt/β-catenin pathways by HIEC-conditioned HS before and after the period of HIIT was shown. Multiple linear regression analysis showed relationships between the effects of HIEC-conditioned HS in PC cells, lactate threshold and VO2max. These results highlight the potential of HIEC bouts in tumor progression control and the importance of optimizing an approach to identify physiological predictors of the effects of acute exercise in tertiary cancer prevention.

Analysis of a Submaximal Cycle Test to Monitor Adaptations to Training: Implications for Optimizing Training Prescription.

Capostagno, B, Lambert, MI, and Lamberts, RP. Analysis of a submaximal cycle test to monitor adaptations to training: Implications for optimizing training prescription. J Strength Cond Res 35(4): 924-930, 2021-The Lamberts and Lambert Submaximal Cycle Test (LSCT) was developed to monitor training adaptation to optimize the training prescription of cyclists. However, it is not known which of the variables within the LSCT are most closely associated with changes in training status. The aim of this study was to retrospectively analyze the LSCT data of cyclists (n = 15) who completed a 2-week high-intensity interval training intervention. The cyclists were retrospectively allocated to 1 of 2 groups based on the change in their 40-km time trial (40-km TT) performance. The "adapters" (n = 7) improved their 40-km TT performance, while the "nonadapters" (n = 8) failed to improve their 40-km TT performance. The variables measured in the LSCT were analyzed to determine which measures tracked the improvements in 40-km TT performance the best. Heart rate recovery increased significantly during the training period in the "adapters" group, but decreased in the "nonadapters" group. Mean power output in stage 2 of the LSCT tended to increase during the high-intensity interval training period in the "adapters" group and was unchanged in the "nonadapters" group. The findings of this study suggest that heart rate recovery and mean power output during stage 2 are the most sensitive markers to track changes in training status within the LSCT.

The Use of Autonomic Modulation Device to Control Training Performance after High-Intensity Interval Training Program.

The aim of the present research was to analyze the autonomic response in a group of trained swimmers before and after conducting a 4-week period of high-intensity interval training (HIT). Heart rate variability was analyzed in 14 swimmers (16.2 ± 2.6years, 169.1 ± 10.2cm and 61.3 ± 9.9kg) in basal condition and during a HIT session before and after completing a training period. The HIT session that was evaluated consisted of: 16 × 25 m maximum speed, resting 30s between sets. Participants combined aerobic training with tethered swimming and HIT sessions three times per week in a period of 4weeks. Results showed a significantly decrease (p < 0.05) of the standard deviation of the NN intervals (SDNN), the standard deviation of differences between adjacent NN intervals (SDSD), the number of successive difference of intervals which differ by more than 50ms (NN50), after the training period. Results showed a higher parasympathetic activation besides improvements in autonomic adaptation after HIT training period.

Effect of Melatonin Supplementation on Antioxidant Status and DNA Damage in High Intensity Trained Athletes.

The aim of the study was to evaluate the effect of melatonin supplementation on antioxidant capacity and DNA damage in high intensity interval training (HIIT) athletes. A 2-week randomised, double-blinded, placebo-controlled trial with two groups was conducted. Placebo (PG) and melatonin (MG) (20 mg/d) athletes were monitored over a two-week period of HIIT and strength training. The total antioxidant capacity (TAC) and the glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were analysed in blood samples. DNA damage was measured in isolated lymphocytes by comet assay prior to and immediately after exercise. The supplementation increased plasma melatonin levels in the melatonin-treated group (p<0.05) after two weeks of intervention. Analysis of antioxidant status indicated higher (p<0.05) TAC and GPx in MG than PG post-intervention. No differences were found in SOD enzyme activity. DNA damage was diminished in MG (p<0.05) compared to PG in post-training conditions. Antioxidant status was associated with DNA damage (r=-0.679; p=0.047) in the melatonin-treated athletes. The present study suggest that melatonin supplementation improves antioxidant status and may prove to have beneficial effects preventing DNA damage induced by high intensity training.

The Mucosal Immune Function Is Not Compromised during a Period of High-Intensity Interval Training. Is It Time to Reconsider an Old Assumption?

Purpose: The aim of the study was to evaluate the mucosal immune function and circadian variation of salivary cortisol, Immunoglobin-A (sIgA) secretion rate and mood during a period of high-intensity interval training (HIIT) compared to long-slow distance training (LSD).Methods: Recreational male runners (n = 28) completed nine sessions of either HIIT or LSD within 3 weeks. The HIIT involved 4 × 4 min of running at 90–95% of maximum heart rate interspersed with 3 min of active recovery while the LSD comprised of continuous running at 70–75% of maximum heart rate for 60–80 min. The psycho-immunological stress-response was investigated with a full daily profile of salivary cortisol and immunoglobin-A (sIgA) secretion rate along with the mood state on a baseline day, the first and last day of training and at follow-up 4 days after the last day of training. Before and after the training period, each athlete's running performance and peak oxygen uptake (V·O2peak) was determined with an incremental exercise test.Results: The HIIT resulted in a longer time-to-exhaustion (P = 0.02) and increased V·O2peak compared to LSD (P = 0.01). The circadian variation of sIgA secretion rate showed highest values in the morning immediately after waking up followed by a decrease throughout the day in both groups (P < 0.05). With HIIT, the wake-up response of sIgA secretion rate was higher on the last day of training (P < 0.01) as well as the area under the curve (AUCG) higher on the first and last day of training and follow-up compared to the LSD (P = 0.01). Also the AUCG for the sIgA secretion rate correlated with the increase in V·O2peak and running performance. The AUCG for cortisol remained unaffected on the first and last day of training but increased on the follow-up day with both, HIIT and LSD (P < 0.01).Conclusion: The increased sIgA secretion rate with the HIIT indicates no compromised mucosal immune function compared to LSD and shows the functional adaptation of the mucosal immune system in response to the increased stress and training load of nine sessions of HIIT.

A High Intensity Interval Training (HIIT)-Based Running Plan Improves Athletic Performance by Improving Muscle Power.

García-Pinillos, F, Cámara-Pérez, JC, Soto-Hermoso, VM, and Latorre-Román, PÁ. A High Intensity Interval Training (HIIT)-based running plan improves athletic performance by improving muscle power. J Strength Cond Res 31(1): 146-153, 2017-This study aimed to examine the effect of a 5-week high-intensity intermittent training (HIIT)-based running plan on athletic performance and to compare the physiological and neuromuscular responses during a sprint-distance triathlon before and after the HIIT period. Thirteen triathletes were matched into 2 groups: the experimental group (EG) and the control group (CG). The CG was asked to maintain their normal training routines, whereas the EG maintained only their swimming and cycling routines and modified their running routine. Participants completed a sprint-distance triathlon before (pretest) and after (posttest) the intervention period. In both pretest and posttest, the participants performed 4 jumping tests: before the race (baseline), postswim, postcycling, and postrun. Additionally, heart rate was monitored (HRmean), whereas rate of perceived exertion (RPE) and blood lactate accumulation (BLa) were registered after the race. No significant differences (p ≥ 0.05) between groups were found before HIIT intervention (at pretest). Significant group-by-training interactions were found in vertical jumping ability and athletic performance: the EG improved jumping performance (∼6-9%, p ≤ 0.05, effect size (ES) > 0.7), swimming performance (p = 0.013, ES = 0.438), and running time (p = 0.001, ES = 0.667) during the competition, whereas the CG remained unchanged (p ≥ 0.05, ES < 0.4). No changes (p ≥ 0.05, ES < 0.4) were observed in RPE, HRmean, and BLa. A linear regression analysis showed that ΔCMJ predicted both the ΔRu_time (R = 0.559; p = 0.008) and the ΔOverall_time (R = 0.391; p = 0.048). This low-volume, HIIT-based running plan combined with the high training volumes of these triathletes in swimming and cycling improved athletic performance during a sprint-distance triathlon. This improvement may be due to improved neuromuscular characteristics that were transferred into improved muscle power and work economy.

The Durational Effects of High Intensity Interval Training on Physiological Variables in Recreationally Active Individuals

PURPOSE: The purpose was to compare the effects high intensity interval training (HIIT) and steady-state aerobic exercise (AER) had on VO2max and visceral fat and to quantify the effects of a two week detraining period. METHODS: 27 college-aged participants (17 males, 10 females), who met minimal ACSM aerobic guidelines for aerobic exercise, were randomly assigned to a HIIT or AER training group. Each group underwent 30 minutes of treadmill-based exercise during their respective session. Both HIIT and AER sessions included a five minute warm-up, a 20 minute training period, and a five minute cool-down. The HIIT period consisted of 10 intermittent bouts of one minute high intensity exercise (90-95% HRmax) followed by one minute of moderate intensity exercise (60-65% HRmax). The AER group maintained a pace at 60-65% HRmax for 20 minutes. Participants completed two sessions per week over a three week period. Following training participants engaged in a two week detraining period. Values for dependent variables were assessed pre-training (PreT), post-training (PT), and post-detraining (PDT). RESULTS: A significant main effect for time was determined for visceral fat (p < .05) with post hoc testing showing a decrease in visceral fat occurred from PreT to PT in the AER group. Combined as a whole, there was significant decrease (p < .05) in visceral fat from PreT (50.24 ± 23.07) to PT (47.05 ± 21.67), and significant increase from PT (47.05 ± 21.67) to PDT (49.22 ± 22.93). No significant change in VO2max (p > .05) in either group over time was noted.Table: No title available.CONCLUSION: A three week, six-session HIIT and AER program elicit significant reductions in visceral fat mass. HIIT is a viable, time efficient method to improve measures of fitness among college-age individuals.

A short period of high-intensity interval training improves skeletal muscle mitochondrial function and pulmonary oxygen uptake kinetics.

The aim of the present study was to examine whether improvements in pulmonary oxygen uptake (V̇o2) kinetics following a short period of high-intensity training (HIT) would be associated with improved skeletal muscle mitochondrial function. Ten untrained male volunteers (age 26 ± 2 yr; mean ± SD) performed six HIT sessions (8-12 × 60 s at incremental test peak power; 271 ± 52 W) over a 2-wk period. Before and after the HIT period, V̇o2 kinetics was modeled during moderate-intensity cycling (110 ± 19 W). Mitochondrial function was assessed with high-resolution respirometry (HRR), and maximal activities of oxidative enzymes citrate synthase (CS) and cytochrome c oxidase (COX) were accordingly determined. In response to HIT, V̇o2 kinetics became faster (τ: 20.4 ± 4.4 vs. 28.9 ± 6.1 s; P < 0.01) and fatty acid oxidation (ETFP) and leak respiration (LN) both became elevated (P < 0.05). Activity of CS and COX did not increase in response to training. Both before and after the HIT period, fast V̇o2 kinetics (low τ values) was associated with large values for ETFP, electron transport system capacity (ETS), and electron flow specific to complex II (CIIP) (P < 0.05). Collectively, these findings support that selected measures of mitochondrial function obtained with HRR are important for fast V̇o2 kinetics and better markers than maximal oxidative enzyme activity in describing the speed of the V̇o2 response during moderate-intensity exercise.

Repeated transient mRNA bursts precede increases in transcriptional and mitochondrial proteins during training in human skeletal muscle

Exercise training induces mitochondrial biogenesis, but the time course of molecular sequelae that accompany repetitive training stimuli remains to be determined in human skeletal muscle. Therefore, throughout a seven-session, high-intensity interval training period that increased (12%), we examined the time course of responses of (a) mitochondrial biogenesis and fusion and fission proteins, and (b) selected transcriptional and mitochondrial mRNAs and proteins in human muscle. Muscle biopsies were obtained 4 and 24 h after the 1st, 3rd, 5th and 7th training session. PGC-1α mRNA was increased >10-fold 4 h after the 1st session and returned to control within 24 h. This 'saw-tooth' pattern continued until the 7th bout, with smaller increases after each bout. In contrast, PGC-1α protein was increased 24 h after the 1st bout (23%) and plateaued at +30-40% between the 3rd and 7th bout. Increases in PGC-1β mRNA and protein were more delayed and smaller, and did not persist. Distinct patterns of increases were observed in peroxisome proliferator-activated receptor (PPAR) α and γ protein (1 session), PPAR β/δ mRNA and protein (5 sessions) and nuclear respiratory factor-2 protein (3 sessions) while no changes occurred in mitochondrial transcription factor A protein. Citrate synthase (CS) and β-HAD mRNA were rapidly increased (1 session), followed 2 sessions later (session 3) by increases in CS and β-HAD activities, and mitochondrial DNA. Changes in COX-IV mRNA (session 3) and protein (session 5) were more delayed. Training also increased mitochondrial fission proteins (fission protein-1, >2-fold; dynamin-related protein-1, 47%) and the fusion protein mitofusin-1 (35%) but not mitofusin-2. This study has provided the following novel information: (a) the training-induced increases in transcriptional and mitochondrial proteins appear to result from the cumulative effects of transient bursts in their mRNAs, (b) training-induced mitochondrial biogenesis appears to involve re-modelling in addition to increased mitochondrial content, and (c) the 'transcriptional capacity' of human muscle is extremely sensitive, being activated by one training bout.

Improvements in insulin sensitivity and whole-body fat oxidation after a period of high-intensity interval training

Physically trained individuals exhibit high rates of whole-body fat oxidation and elevated insulin sensitivity. High-intensity interval training (HIT) has been suggested to induce similar metabolic adaptations in a more time efficient manner than traditional endurance training. To widen this claim the authors aimed to investigate whether 6 weeks of HIT improves whole-body fat oxidation and insulin sensitivity in young sedentary males. Eight participants (23±2 years; body mass index 24.5±1.5 kg/m2; VO2peak 43.0±1.5 ml/min/kg) with normal glucose tolerance undertook 6 weeks of HIT consisting of between four and six 30-s Wingate tests separated by 4.5 min rest, performed three times per week. Insulin sensitivity (oral glucose tolerance test (OGTT)) and substrate metabolism during a 60-min steady state cycling trial (∼65% pretraining VO2peak) was assessed before and after HIT. Dual energyx-ray absorptiometry was also used to measure changes in body composition in response to training. VO2peak increased 18% (pre 43.0±1.5 ml/min/kg2, post 50.8±1.8 ml/min/kg2; p&lt;0.05). A 5% reduction in relative fat content in the body was observed (pre 19.6±2.2%, post 18.8±2.1%, p&lt;0.05), which was attributed to a 6% decrease in relative fat content in the legs. Absolute carbohydrate oxidation was reduced after HIT (pre 1.75±0.11 g/min, post 1.49±0.11 g/min; p=0.04), while relative fat oxidation showed a tendency to increase (pre 35.2±5.7%, post 43.3±3.6%; p=0.078). Plasma glucose and insulin area under the curve in response to the OGTT was reduced by 17% and 31% (p&lt;0.05) posttraining, respectively, which corresponded with a 27% improvement in the Matsuda index of insulin sensitivity (pre 4.0±0.5, post 5.1±0.6, p=0.066). The results obtained for the first time provide evidence to suggest that HIT is also a time-efficient method to improve whole-body fat oxidation, body composition and insulin sensitivity in young, sedentary males.

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

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), VO2peak and rate of maximal lactate accumulation (Lacmax). 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). Lacmax increased following HIIT (P < 0.01; effect size = 0.43) and decreased after HVT (P < 0.01; effect size = 0.51). VO2peak increased following both interventions (P < 0.05; effect sizes = 0.46–0.57). The increases in competition performance, T 2,000 m, Lacmax and VO2peak following HIIT were achieved in significantly less training time (~2 h/week).

The Effects of High-Intensity Interval Training in Well-Trained Rowers

Several recent studies have reported substantial performance and physiological gains in well-trained endurance runners, swimmers, and cyclists following a period of high-intensity interval training (HIT). The aim of the current study was to compare traditional rowing training (CT) to HIT in well-trained rowers. Subjects included 5 male and 5 female rowers (mean +/- SD; age = 19 +/- 2 y; height = 176 +/- 8 cm; mass = 73.7 +/- 9.8 kg; Vo2peak = 4.37 +/- 1.08 L.min-1). Baseline testing included a 2000-m time trial and a maximal exercise test to determine Vo2peak, 4-min all-out power, and 4 mmol.L-1 blood lactate threshold. Following baseline testing, rowers were randomly allocated to HIT or CT, which they performed seven times over a 4-wk period. The HIT involved 8 x 2.5-min intervals at 90% of the velocity maintained at Vo2peak, with individual recoveries returning to 70% of the subjects' maximal heart rate between intervals. The CT intensity consisted of workloads corresponding to 2 and 3 mmol.L-1 blood lactate concentrations. On completion of HIT or CT, rowers repeated the testing performed at baseline and were then allocated to the alternative training program and completed a crossover trial. HIT produced greater improvements in 2000-m time (1.9 +/- 0.9%; mean +/- SD), 2000-m power (5.8 +/- 3.0%), and relative Vo2peak (7.0 +/- 6.4%) than CT. Four weeks of HIT improves 2000-m time-trial performance and relative Vo2peak in competitive rowers, more than a traditional approach.