Acute Bout Of High-intensity Interval Training Research Articles

Autophagy response to acute high-intensity interval training and moderate-intensity continuous training is dissimilar in skeletal muscle and peripheral blood mononuclear cells and is influenced by sex

Abstract Autophagy is an evolutionary conserved cellular degradation system that underlies the positive effects of exercise. Currently, few human data exist investigating the autophagic response to exercise including the response to high-intensity interval training (HIIT), response in divergent tissues, and if sex differences exist. The purpose of this study was to investigate the autophagy response in skeletal muscle and peripheral blood mononuclear cells (PBMCs) following an acute bout of HIIT and moderate-intensity continuous training (MICT) with treadmill running in males and females. Using a crossover design, ten recreationally-active males (n = 5; 25.2 ± 1.1 yrs) and females (n = 5; 21.6 ± 3.6 yrs) performed a bout of MICT (60 min at 55% of max velocity [Vmax]]) and HIIT (12 bouts of 1 min at 100% Vmax and 1 min at 3 miles per hour) in a fasted state separated by ≥ 72 h. Muscle biopsy samples from the vastus lateralis and PBMCs were collected pre- and 3 h post-exercise and analyzed for differences in protein expression of LC3I, LC3II, and p62 via western blot analysis. Expression of LC3II:LC3I was significantly different from pre-exercise 3 h post-exercise in MICT in skeletal muscle (64.3 ± 47.3%; p = 0.024). A significant time effect was found for p62 3 h post-exercise compared to pre-exercise (135.23 ± 84.6%; p = 0.043) in skeletal muscle. No differences in markers of autophagy were observed in PBMCs. When sexes were analyzed separately there was a condition x time x sex interaction in LC3II (p = 0.007) and LC3II:LC3I (p = 0.043) in PBMCs. Post hoc analyses revealed a difference in LC3II pre vs. 3 h post exercise in males, but not females, in both HIIT (144.2 ± 89.7%; p = 0.024) and MICT (61.8 ± 36.1%; p = 0.043). Our findings show that HIIT results in changes in markers of autophagy and that the exercise-induced autophagy response varies in tissues and between sexes.

High-Intensity Interval Training vs. Superset Training

High-intensity interval training (HIIT) is used as an alternative to traditional endurance training to increase cardiorespiratory fitness and energy expenditure, however, much less in known about HIIT resistance training (RT). In contrast, superset (SUPER) RT programs, consisting of performing two consecutive exercises on opposing muscle groups while limiting the rest duration between exercises, are common for both hypertrophy and energy expenditure. PURPOSE: To compare the energy expenditure between an acute bout of HIIT and SUPER RT. METHODS: Twelve males (23.91±3.58 y) with at least six months of RT experience completed one-repetition maximum testing and an acute bout of both HIIT and SUPER RT. To ensure volume load (VL) was not different for both protocols, HIIT was always performed first so that VL could be calculated and the number of repetitions for each exercise in the SUPER session could be determined. At least 72 hours rest was taken between the HIIT and SUPER RT protocols. Oxygen consumption (VO2), respiratory exchange ratio (RER), rate of perceived exertion (RPE), total kcal (aerobic), and heart rate (HR) were each collected at rest and after every set throughout each exercise session including between the paired sets in SUPER. Whole blood lactate measures were taken during both sessions at baseline and two-minutes post-exercise. RESULTS: Significant differences were seen between HIIT and SUPER RT: Total overall energy expenditure (346±47.4 vs. 295.5±45.65 kcal, p=0.005), aerobic (132.1±13.03 vs. 157.2±15.98 kcal, p<0.0001), anaerobic (214.3±42.33 vs. 142.8±43.08 kcal, p=0.0002), RER (1.29±0.17 vs. 1.18±0.17, p=<0.0001), post-exercise lactate (15.56±2.49 vs. 10.83±2.42 mmol, p<0.0001), and RPE (14.81±3.41 vs. 12.73±3.81, p=0.001), respectfully, when comparing protocols. There were no significant differences in VO2 or HR. CONCLUSION: HIIT elicited higher total energy expenditure than SUPER despite an overall shorter duration (13:16±00:02 vs. 14:45±00:51, p<0.0001) and a lower one-repetition maximum percentage for each exercise.

Exercise-induced lactate accumulation regulates intramuscular triglyceride metabolism via transforming growth factor-β1 mediated pathways

The mechanism regulating the utilization of intramuscular triacylglycerol (IMTG) during high-intensity interval training (HIIT) and post-exercise recovery period remains elusive. In this study, the acute and long-term effects of HIIT on transforming growth factor beta 1 (TGF-β1) abundance in rat skeletal muscle and role of lactate and TGF-β1 in IMTG lipolysis during post-exercise recovery period were examined. TGF-β1 and Adipose triacylglycerol lipase (ATGL) abundance as well as total lipase activity in the gastrocnemius muscle significantly increased to a maximum value 10 h after acute bout of HIIT. Inhibition of TGF-β1 signaling by intramuscular injection of SB431542 30 min prior to the acute exercise attenuated ATGL abundance and total lipase activity in the gastrocnemius muscle in response to acute exercise. Intramuscular acute injection of lactate increased TGF-β1 and ATGL abundance in the gastrocnemius muscle and there were a significant increase in Muscle TGF-β1 and ATGL abundance after 5 weeks of HIIT/lactate treatment. These results indicate that exercise-induced lactate accumulation regulates intramuscular triglyceride metabolism via transforming growth factor-β1 mediated pathways during post-exercise recovery from strenuous exercise.

High-intensity interval training-induced metabolic adaptation coupled with an increase in Hif-1α and glycolytic protein expression.

It is known that repeated bouts of high-intensity interval training (HIIT) lead to enhanced levels of glycolysis, glycogenesis, and lactate transport proteins in skeletal muscle; however, little is known about the molecular mechanisms underlying these adaptations. To decipher the mechanism leading to improvement of skeletal muscle glycolytic capacity associated with HIIT, we examined the role of hypoxia-inducible factor-1α (Hif-1α), the major transcription factor regulating the expression of genes related to anaerobic metabolism, in the adaptation to HIIT. First, we induced Hif-1α accumulation using ethyl 3,4-dihydroxybenzoate (EDHB) to assess the potential role of Hif-1α in skeletal muscle. Treatment with EDHB significantly increased the protein levels of Hif-1α in gastrocnemius muscles, accompanied by elevated expression of genes related to glycolysis, glycogenesis, and lactate transport. Daily administration of EDHB for 1 wk resulted in elevated glycolytic enzyme activity in gastrocnemius muscles. Second, we examined whether a single bout of HIIT could induce Hif-1α protein accumulation and subsequent increase in the expression of genes related to anaerobic metabolism in skeletal muscle. We observed that the protein levels of Hif-1α and expression of the target genes were elevated 3 h after an acute bout of HIIT in gastrocnemius muscles. Last, we examined the effects of long-term HIIT. We found that long-term HIIT increased the basal levels of Hif-1α as well as the glycolytic capacity in gastrocnemius muscles. Our results suggest that Hif-1α is a key regulator in the metabolic adaptation to high-intensity training.