Fibre-Specific Responses to Endurance and Low Volume High Intensity Interval Training: Striking Similarities in Acute and Chronic Adaptation

The current study involved the completion of two distinct experiments. Experiment 1 compared fibre specific and whole muscle responses to acute bouts of either low-volume high-intensity interval training (LV-HIT) or moderate-intensity continuous endurance exercise (END) in a randomized crossover design. Experiment 2 examined the impact of a six-week training intervention (END or LV-HIT; 4 days/week), on whole body and skeletal muscle fibre specific markers of aerobic and anaerobic capacity. Six recreationally active men (Age: 20.7±3.8 yrs; VO2peak: 51.9±5.1 mL/kg/min) reported to the lab on two separate occasions for experiment 1. Following a muscle biopsy taken in a fasted state, participants completed an acute bout of each exercise protocol (LV-HIT: 8, 20-second intervals at ∼170% of VO2peak separated by 10 seconds of rest; END: 30 minutes at ∼65% of VO2peak), immediately followed by a muscle biopsy. Glycogen content of type I and IIA fibres was significantly (p<0.05) reduced, while p-ACC was significantly increased (p<0.05) following both protocols. Nineteen recreationally active males (n = 16) and females (n = 3) were VO2peak-matched and assigned to either the LV-HIT (n = 10; 21±2 yrs) or END (n = 9; 20.7±3.8 yrs) group for experiment 2. After 6 weeks, both training protocols induced comparable increases in aerobic capacity (END: Pre: 48.3±6.0, Mid: 51.8±6.0, Post: 55.0±6.3 mL/kg/min LV-HIT: Pre: 47.9±8.1, Mid: 50.4±7.4, Post: 54.7±7.6 mL/kg/min), fibre-type specific oxidative and glycolytic capacity, glycogen and IMTG stores, and whole-muscle capillary density. Interestingly, only LV-HIT induced greater improvements in anaerobic performance and estimated whole-muscle glycolytic capacity. These results suggest that 30 minutes of END exercise at ∼65% VO2peak or 4 minutes of LV-HIT at ∼170% VO2peak induce comparable changes in the intra-myocellular environment (glycogen content and signaling activation); correspondingly, training-induced adaptations resulting for these protocols, and other HIT and END protocols are strikingly similar

A systematic upregulation of nuclear and mitochondrial genes is not present in the initial post-exercise recovery period in human skeletal muscle

The purpose of the current investigation was to determine if an exercise-mediated upregulation of nuclear and mitochondrial-encoded genes targeted by the transcriptional co-activator peroxisome-proliferator-activated receptor gamma co-activator-1 alpha (PGC-1α) occurs in a systematic manner following different exercise intensities in humans. Ten recreationally active males (Age: 23 ±3 yrs; VO2peak: 41.8 ±6.6 mL/kg/min) completed two acute bouts of work-matched interval exercise at ~73% (LO) and ~100% (HI) of work rate at VO2peak in a randomized cross-over design. Muscle biopsies were taken before (Pre), immediately after (Post), and 3 hours into recovery (3hr) following each exercise bout. A main effect of time (pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Acute upregulation of PGC-1α mRNA correlates with training-induced increases in SDH activity in human skeletal muscle

The purpose of the present study was to determine if acute responses in pgc-1α, vegfa, sdha, and gpd1/2 mRNA expression predict their associated chronic skeletal muscle molecular (SDH/GPD activity and substrate storage) and morphological (fibre type composition and capillary density) adaptations following training. Skeletal muscle biopsies were collected from fourteen recreationally active men (age: 22.0 ± 2.4 years) before (PRE) and 3 hours after (3HR) the completion of an acute bout of SIT (eight, 20-second intervals at ~170% VO2peak work rate separated by 10 seconds of recovery). Participants then completed 6 weeks of SIT 4 times per week with additional biopsies after 2 (MID) and 6 (POST) weeks of training. Acute increases in pgc-1α mRNA strongly predicted increases in SDH activity (a marker of oxidative capacity) from PRE and MID to POST (PRE-POST: r = 0.81, r2 = 0.65, pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

An examination of resveratrol's mechanisms of action in human tissue: impact of a single dose in vivo and dose responses in skeletal muscle ex vivo.

The current study tested the hypothesis that a single, moderate dose of RSV would activate the AMPK/SIRT1 axis in human skeletal muscle and adipose tissue. Additionally, the effects of RSV on mitochondrial respiration in PmFBs were examined. Eight sedentary men (23.8±2.4 yrs; BMI: 32.7±7.1) reported to the lab on two occasions where they were provided a meal supplemented with 300 mg of RSV or a placebo. Blood samples, and a muscle biopsy were obtained in the fasted state and again, with the addition of an adipose tissue biopsy, two hours post-prandial. The effect of RSV on mitochondrial respiration was examined in PmFBs taken from muscle biopsies from an additional eight men (23.4±5.4 yrs; BMI: 24.4±2.8). No effect of RSV was observed on nuclear SIRT1 activity, acetylation of p53, or phosphorylation of AMPK, ACC or PKA in either skeletal muscle or adipose tissue. A decrease in post absorptive insulin levels was accompanied by elevated skeletal muscle phosphorylation of p38 MAPK, but no change in either skeletal muscle or adipose tissue insulin signalling. Mitochondrial respiration in PmFBs was rapidly inhibited by RSV at 100-300 uM depending on the substrate examined. These results question the efficacy of a single dose of RSV at altering skeletal muscle and adipose tissue AMPK/SIRT1 activity in humans and suggest that RSV mechanisms of action in humans may be associated with altered cellular energetics resulting from impaired mitochondrial ATP production

An examination of resveratrol's mechanisms of action in human tissue: impact of a single dose in vivo and dose responses in skeletal muscle ex vivo.

The current study tested the hypothesis that a single, moderate dose of RSV would activate the AMPK/SIRT1 axis in human skeletal muscle and adipose tissue. Additionally, the effects of RSV on mitochondrial respiration in PmFBs were examined. Eight sedentary men (23.8±2.4 yrs; BMI: 32.7±7.1) reported to the lab on two occasions where they were provided a meal supplemented with 300 mg of RSV or a placebo. Blood samples, and a muscle biopsy were obtained in the fasted state and again, with the addition of an adipose tissue biopsy, two hours post-prandial. The effect of RSV on mitochondrial respiration was examined in PmFBs taken from muscle biopsies from an additional eight men (23.4±5.4 yrs; BMI: 24.4±2.8). No effect of RSV was observed on nuclear SIRT1 activity, acetylation of p53, or phosphorylation of AMPK, ACC or PKA in either skeletal muscle or adipose tissue. A decrease in post absorptive insulin levels was accompanied by elevated skeletal muscle phosphorylation of p38 MAPK, but no change in either skeletal muscle or adipose tissue insulin signalling. Mitochondrial respiration in PmFBs was rapidly inhibited by RSV at 100-300 uM depending on the substrate examined. These results question the efficacy of a single dose of RSV at altering skeletal muscle and adipose tissue AMPK/SIRT1 activity in humans and suggest that RSV mechanisms of action in humans may be associated with altered cellular energetics resulting from impaired mitochondrial ATP production

The impact of a 48-hour fast on SIRT1 and GCN5 in human skeletal muscle

The present study examined the impact of a 48 hour fast on the expression and activation status of SIRT1 and GCN5, and the relationship between SIRT1/GCN5 and the gene expression of PGC-1α, and the PGC-1α target PDK4, in the skeletal muscle of ten lean healthy men (age, 22.0 ± 1.5 years; VO2peak, 47.2 ± 6.7 mL/min/kg). Muscle biopsies and blood samples were collected 1 hour postprandial (Fed) and following 48 hours of fasting (Fasted). Plasma insulin (Fed, 80.8 ± 47.9 pmol/L; Fasted, not detected) and glucose (Fed, 4.36 ± 0.86; Fasted, 3.74 ± 0.25 mmol/L, p = 0.08) decreased, confirming participant adherence to fasting. Gene expression of PGC-1α decreased (pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The impact of work-matched interval training on VO2peak and VO2 kinetics: diminishing returns with increasing intensity

High intensity interval training (HIIT) improves VO2peak and VO2 kinetics, however, it is unknown whether an optimal intensity of HIIT exists for eliciting improvements in these measures of whole body oxidative metabolism. The purpose of this study was to: 1) investigate the effect of interval intensity on training-induced adaptations in VO2peak and VO2 kinetics, and 2) examine the impact of interval intensity on the frequency of non-responders in VO2peak. 36 healthy men and women completed 3 weeks of cycle ergometer HIIT, consisting of intervals targeting 80% (LO), 115% (MID) or 150% (HI) of peak aerobic power. Total work performed per training session was matched across groups. A main effect of training (pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Resveratrol inhibits mitochondrial respiration in permeabilized muscle fibre bundles.

<p>The effect of resveratrol or vehicle (DMSO) on substrate-specific respiration was determined by titrating resveratrol following the induction of state 3 respiration with either 10 mM glutamate (A), 10 mM succinate (B), 10 mM pyruvate (C) or 40 µM palmitoyl carnitine (D) with 5 mM malate in all protocols. Changes in mitochondrial respiration are expressed relative to maximal state 3 respiration determined immediately prior to the resveratrol titration. * Significantly different (<i>P</i><0.05) from vehicle treatment.</p

Impact of interval intensity on the expression of PGC-1α regulators.

<p>Impact of interval intensity on the expression of (A) SIRT1, (B) GCN5, and (C) RIP140. The change in mRNA expression from baseline to post-exercise for interval intensities of 73% (open bars), 100% (grey bars) and 133% (dark bars) is shown (A). Values presented as Mean ± SEM. * Significant (<i>p</i><0.05) main effect of time.</p

Descriptive statistics for individual interval protocols.

<p>Values presented as mean ± SD.</p>*<p>Significantly (p<0.05) different from 73%.</p>†<p>Significantly (p<0.05) different from both 73% and 100%.</p