High-intensity Interval Cycling Exercise Research Articles

Impact of exercise and fasting on mitochondrial regulators in human muscle.

To investigate the impact of acute energetic stress (acute HIIE and fasting) on ERRγ, PPARβ, NR1D1, NR4A1, and TFEB in human skeletal muscle. The current study performed secondary analyses using muscle biopsy samples from two previously published studies: study 1) leg muscle biopsies from nine men and eight women were obtained pre and 3 h following acute high-intensity interval cycling exercise (HIIE); study 2) leg muscle biopsies were obtained from nine men pre-, during, and post-an 8 h fast with or without 2 h of arm ergometer exercise. RT-PCR was performed on samples from each study to determine the mRNA expression of ERRγ, PPARβ, NR1D1, NR4A1, and TFEB. Additionally, we retrieved data from meta-analyzed human muscle gene expression using the publicly available database MetaMex. PGC-1α (p<0.01, d=1.98) and NR4A1 (p<0.01, d=1.36) mRNA expression significantly increased while TFEB (p≤0.05, d=0.70) decreased following HIIE. Significant decreases in NR4A1 and NR1D1 mRNA expression were observed following an 8 h fast. Our MetaMex analyses revealed significant increases (p<0.05) in PGC-1α andNR4A1 expression following aerobic and resistance exercise, and in PPARβ expression following resistance exercise. Our data indicate that acute HIIE stimulates increases in NR4A1 and PGC-1α and decreases in TFEB mRNA expression in human skeletal muscle. Additionally, a short term (8 h) fast reduced the mRNA expression of the transcriptional regulators NR4A1 and NR1D1- potentially as a mechanism ofdecreasing mitochondrial biogenesis to reduce energy expenditure during a period of restricted energy availability.

Ageing attenuates exercise-enhanced motor cortical plasticity.

Cardiorespiratory exercise is known to modulate motor cortical plasticity in young adults, but the influence of ageing on this relationship is unknown. Here, we compared the effects of a single session of cardiorespiratory exercise on motor cortical plasticity in young and older adults. We acquired measures of cortical excitatory and inhibitory activity of the primary motor cortex using transcranial magnetic stimulation (TMS) from 20 young (mean±SD = 25.30 ± 4.00 years, 14 females) and 20 older (mean±SD = 64.10 ± 6.50 years, 11 females) healthy adults. Single- and paired-pulse TMS measurements were collected before and after a 20min bout of high-intensity interval cycling exercise or an equivalent period of rest, and again after intermittent theta burst stimulation (iTBS). In both young (P = 0.027, Cohen's d = 0.87) and older adults (P = 0.006, Cohen's d = 0.85), there was an increase in glutamatergic excitation and a reduction in GABAergic inhibition from pre- to postexercise. However, in contrast to younger adults, older adults showed an attenuated plasticity response to iTBS following exercise (P = 0.011, Cohen's d = 0.85). These results demonstrate an age-dependent decline in cortical plasticity and indicate that a preceding bout of high-intensity interval exercise might be less effective for enhancing primary motor cortex plasticity in older adults. Our findings align with the hypothesis that the capacity for cortical plasticity is altered in older age. KEY POINTS: Exercise enhances motor cortical plasticity in young adults, but how ageing influences this effect is unknown. Here, we compared primary motor cortical plasticity responses in young and older adults before and after a bout of high-intensity interval exercise and again after a plasticity-inducing protocol, intermittent theta burst stimulation. In both young and older adults, exercise led to an increase in glutamatergic excitation and a reduction in GABAergic inhibition. Our key result was that older adults showed an attenuated plasticity response to theta burst stimulation following exercise, relative to younger adults. Our findings demonstrate an age-dependent decline in exercise-enhanced cortical plasticity and indicate that a preceding bout of high-intensity interval exercise might be less effective for enhancing primary motor cortex plasticity in older adults.

D2 receptor blockade eliminates exercise-induced changes in cortical inhibition and excitation

BackgroundAlthough cardiorespiratory exercise is known to affect cortical excitatory and inhibitory activity, the neurochemical mechanisms driving this effect are poorly understood. Animal models of Parkinson's disease identify dopamine D2 receptor expression as a candidate mechanism, but the link between the D2 receptor and exercise-induced changes in cortical activity in humans is unknown. ObjectiveHere, we examined the effect of a selective dopamine D2 receptor antagonist, sulpiride, on exercise-induced changes in cortical activity. MethodsWe acquired measures of excitatory and inhibitory activity of the primary motor cortex using transcranial magnetic stimulation (TMS) from 23 healthy adults, both before and after a 20-min bout of high-intensity interval cycling exercise. We examined the effect of D2 receptor blockade (800 mg sulpiride) on these measures within a randomised, double-blind, placebo-controlled crossover design. ResultsSulpiride abolished exercise-induced modulation of the cortical excitation:inhibition balance relative to placebo (P < 0.001, Cohen's d = 1.76). Sulpiride blocked both the increase in glutamatergic excitation and reduction in gamma-aminobutyric acid (GABA) inhibition that was observed following exercise in the placebo condition. ConclusionOur results provide causal evidence that D2 receptor blockade eliminates exercise-induced changes in excitatory and inhibitory cortical networks, and have implications for how exercise should be prescribed in diseases of dopaminergic dysfunction.

FP.06 Use of an exercise challenge system to define a universal proteomic signature of muscle injury in a diverse set of adults with inherited myopathy

Several inherited myopathies are defined by an enhanced injury response to exercise. However, current understanding of muscle injury depending on the underlying genetic lesion is poorly understood. We used an established exercise intervention along with the SOMAscan 7K platform to characterize serum proteomic signatures of exercise-induced muscle injury in a diverse set of adults with myopathy. Participants included healthy volunteers, Becker muscular dystrophy (BMD), Limb-girdle muscular dystrophies R9 (LGMDR9) and R12 (LGMDR12), and McArdle disease (McA). Muscle injury was induced by an exercise challenge consisting of high-intensity interval cycling exercise followed by a leg strength test, which has been shown to cause injury in BMD and McA. Blood samples were collected before exercise and at intervals of up to 24 hours post-exercise. We identified an indication-independent novel cluster of 27 plasma-based biomarkers that distinguished pre-exercise myopathy individuals from healthy controls. The exercise response of this distinguishing cluster revealed two subsets of proteins, those that further changed after exercise and those that were exercise-independent. Exercise-dependent biomarkers demonstrated a clear time-dependency, with >90% increasing to maximal levels at 2-4 hours post-injury. When comparing indication-specific injury responses, BMD, LGMDR9, and McA revealed a surprising degree of overlap (33 proteins), including 15 proteins that were not increased at baseline in any indication. In comparison, LGMDR12 individuals demonstrated elevated baseline signature markers but no significant injury response. The controls showed no significant biomarker response to the exercise challenge. These data not only provide several new biomarker candidates for distinguishing muscle injury but highlight significant common features between indications, suggesting a common mechanism of muscle injury and breakdown, independent of the underlying pathophysiology.

Comparing the Effects of Immersed Versus Land-Based High-Intensity Interval Cycling on Energy Intake, Appetite Sensations and Perceived Exertion Among Healthy Men.

Immersed exercise has been shown to induce higher energy expenditure and no difference or increase in food intake compared with similar exercise on land. In this study, we compared the effects of acute high-intensity cycling performed on land versus when immersed on subsequent energy intake (EI), appetite sensations and perceived exertion (RPE) in healthy men. Ten participants in a postprandial condition completed three experimental visits in a randomized order: a control condition (CONT); a high-intensity interval cycling exercise performed on land (HIIE-L) and the same exercise while immersed in water (HIIE-A) with a similar targeted heart rate. We observed no difference in energy and macronutrient intake and in area under the curve (AUC) for appetite sensations between sessions. The RPE at the end of HIIE-L was negatively correlated with EI (r=-0.67; p < 0.05), AUC for hunger (r=-0.86, p < 0.01), desire to eat (r=-0.78, p < 0.05) and prospective food consumption (r=-0.86, p < 0.01). Conversely, the RPE at the end of HIIE-L was positively correlated with AUC for fullness (r = 0.76, p < 0.05). No such correlations were observed for HIIE-A. The present study was the first to observe that immersion did not influence EI after HIIE cycling, but immersion blunted the relationship between session RPE and subsequent energy intake and appetite sensations relative to HIIE on land.

The impact of preconditioning exercise on the vascular response to an oral glucose challenge.

Exercise elicits direct benefits to insulin sensitivity but may also indirectly improve glucose uptake by hemodynamic conditioning of the vasculature. The purpose of this study was to examine the modifying effect of 3 different types of exercise on the vascular response to an oral glucose challenge. Twenty healthy adults (9 women, 11 men; aged 23 ± 3 years) completed a standard oral glucose tolerance test (OGTT) at rest, as well as 1.5 hours after moderate continuous cycling exercise (30min; 65% peak oxygen consumption), high-intensity interval cycling exercise (10 × 1 min at 90% peak heart rate), and lower-load higher-repetition resistance exercise (25-35 repetitions/set, 3 sets). Brachial and superficial femoral artery blood flow, conductance, and oscillatory shear index were measured throughout the OGTT. Regardless of rested state or exercise preconditioning, the OGTT induced reductions in brachial artery blood flow and conductance (p< 0.001), and transient increases in brachial and superficial femoral artery oscillatory shear index and retrograde blood flow (p< 0.01). Continuous cycling and resistance exercise were followed with a small degree of protection against prolonged periods of oscillatory flow. Our findings imply transient peripheral vasoconstriction and decreased limb blood flow during a standard OGTT, for which prior exercise was unable to prevent in healthy adults. Novelty: We investigated the impact of continuous, interval, and resistance exercise on the hemodynamic response to an OGTT. Our findings suggest decreased upper-limb blood flow during an OGTT is not prevented by prior exercise in healthy adults.

Acute Exercise at Different Intensities Influences Corticomotor Excitability and Performance of a Ballistic Thumb Training Task

The response to motor training is improved when preceded by a bout of aerobic exercise. However, the effect of exercise at different intensities on motor performance is not well understood. The aim of the current study was therefore to compare the neurophysiological and functional response to training with a ballistic abduction task following a single 30-min bout of low intensity continuous cycling exercise, high-intensity interval cycling exercise, or rest. In 13 healthy young subjects, transcranial magnetic stimulation (TMS) was used to assess changes in the motor evoked potential (MEP), in addition to short-interval intracortical inhibition (SICI), whereas performance was assessed by changes in thumb abduction acceleration performed over two consecutive days. High-intensity exercise resulted in increased MEP amplitude and decreased SICI immediately after exercise. Following training, the increased MEP amplitude that reflects training-dependent plasticity was not different between exercise conditions. In contrast, reductions in SICI following training on day 1 were increased following high-intensity exercise, but decreased following low-intensity exercise, whereas cortical disinhibition was abolished after training on day 2. Finally, low-intensity exercise resulted in improved ballistic motor performance on both days. Our findings provide some evidence to suggest that low-intensity aerobic cycling is beneficial for performance during subsequent ballistic training. Furthermore, the effects of exercise intensity on motor training may depend on the type of task performed.

Circulatory exosomal miRNA following intense exercise is unrelated to muscle and plasma miRNA abundances

MicroRNAs (miRNAs) regulate gene expression via transcript degradation and translational inhibition, and they may also function as long distance signaling molecules. Circulatory miRNAs are either protein-bound or packaged within vesicles (exosomes). Ten young men (24.6 ± 4.0 yr) underwent a single bout of high-intensity interval cycling exercise. Vastus lateralis biopsies and plasma were collected immediately before and after exercise, as well as 4 h following the exercise bout. Twenty-nine miRNAs previously reported to be regulated by acute exercise were assessed within muscle, venous plasma, and enriched circulatory exosomes via qRT-PCR. Of the 29 targeted miRNAs, 11 were altered in muscle, 8 in plasma, and 9 in the exosome fraction. Although changes in muscle and plasma expression were bidirectional, all regulated exosomal miRNAs increased following exercise. Three miRNAs were altered in all three sample pools (miR-1-3p, -16-5p, and -222-3p), three in both muscle and plasma (miR-21-5p, -134-3p, and -107), three in both muscle and exosomes (miR-23a-3p, -208a-3p, and -150-5p), and three in both plasma and exosomes (miR-486-5p, -126-3p, and -378a-5p). There was a marked discrepancy between the observed alterations between sample pools. A subset of exosomal miRNAs increased in abundance following exercise, suggesting an exercise-induced release of exosomes enriched in specific miRNAs. The uniqueness of the exosomal miRNA response suggests its relevance as a sample pool that needs to be further explored in better understanding biological functions.

The Effects of Acute Interval Exercise and Strawberry Intake on Postprandial Lipemia.

Raised postprandial triglycerides (TAG) and related oxidative stresses are strongly associated with increased cardiovascular disease risk. Acute exercise and strawberry ingestion independently ameliorate postprandial lipid excursions and oxidative stress. However, the combined effects of these lifestyle interventions are unknown. We investigated whether acute exercise and strawberry consumption improved postprandial responses to an oral fat tolerance test (OFTT) in overweight/obese males. Overweight/obese adult males underwent four separate OFTT (73 g fat, 33 g carbohydrate) with blood sampled at baseline and hourly for 4 h after OFTT. Two OFTT contained 25 g freeze-dried strawberries and two contained strawberry flavoring (placebo). Participants performed 40 min of submaximal high-intensity interval cycling exercise 16 h before one strawberry and one placebo OFTT and rested before the remaining two OFTT. Serum TAG was analyzed, and TAG area under the curve (AUC) and incremental AUC (iAUC) were calculated. Oxidative stress markers were measured at baseline and 4 h. Differences between conditions (strawberry/placebo and exercise/rest) were assessed using repeated-measures ANOVA. Ten males (age = 31.5, interquartile range = 17.8 yr, body mass index = 29.9 ± 1.8 kg·m) completed the study. TAG AUC was 1.5 mmol per 4 h·L lower for the exercise conditions compared with the rest conditions (95% confidence interval [CI] = -2.3 to -0.8 mmol per 4 h·L, P = 0.001). TAG AUC was not different between strawberry and placebo conditions (95% CI = -1.3 to 0.6 mmol per 4 h·L, P = 0.475). TAG iAUC was 0.5 mmol per 4 h·L greater for the strawberry compared with the placebo conditions (95% CI = 0.1 to 1.0 mmol per 4 h·L, P = 0.021). There were no changes in markers of lipid related oxidative stress (P > 0.05). Acute submaximal high-intensity interval cycling exercise appears effective in reducing postprandial lipemia in overweight/obese adult males. However, strawberry ingestion did not improve postprandial TAG.

High-Intensity Interval Cycling Exercise on Wave Reflection and Pulse Wave Velocity.

Kingsley, JD, Tai, YL, Vaughan, J, and Mayo, X. High-intensity interval cycling exercise on wave reflection and pulse wave velocity. J Strength Cond Res 31(5): 1313-1320, 2017-The purpose of this study was to assess the effects of high-intensity exercise on wave reflection and aortic stiffness. Nine young, healthy men (mean ± SD: age: 22 ± 2 years) participated in the study. The high-intensity interval cycling exercise consisted of 3 sets of Wingate Anaerobic Tests (WATs) with 7.5% of bodyweight as resistance and 2 minutes of rest between each set. Measurements were taken at rest and 1 minute after completion of the WATs. Brachial and aortic blood pressures, as well as wave reflection characteristics, were measured through pulse wave analysis. Aortic stiffness was assessed through carotid-femoral pulse wave velocity (cfPWV). A repeated-measures analysis of variance was used to investigate the effects of the WATs on blood pressure and vascular function across time. There was no change in brachial or aortic systolic pressure from rest to recovery. There was a significant (p ≤ 0.05) decrease in brachial diastolic pressure (rest: 73 ± 6 mm Hg; recovery: 67 ± 9 mm Hg) and aortic diastolic pressure (rest: 75 ± 6 mm Hg; recovery: 70 ± 9 mm Hg) from rest to recovery. In addition, there was no significant change in the augmentation index (rest: 111.4 ± 6.5%; recovery: 109.8 ± 5.8%, p = 0.65) from rest to recovery. However, there was a significant (p ≤ 0.05) increase in the augmentation index normalized at 75 b·min (rest: 3.29 ± 9.82; recovery 21.21 ± 10.87) during recovery compared with rest. There was no change in cfPWV (rest: 5.3 ± 0.8 m·s; recovery: 5.7 ± 0.5m·s; p = 0.09) in response to the WAT. These data demonstrate that high-intensity interval cycling exercise with short rest periods has a nonsignificant effect on vascular function.

Cardiorespiratory fitness modulates the acute flow-mediated dilation response following high-intensity but not moderate-intensity exercise in elderly men.

Impaired endothelial function is observed with aging and in those with low cardiorespiratory fitness (V̇o2peak). Improvements in endothelial function with exercise training are somewhat dependent on the intensity of exercise. While the acute stimulus for this improvement is not completely understood, it may, in part, be due to the flow-mediated dilation (FMD) response to acute exercise. We examined the hypothesis that exercise intensity alters the brachial (systemic) FMD response in elderly men and is modulated by V̇o2peak Forty-seven elderly men were stratified into lower (V̇o2peak = 24.3 ± 2.9 ml·kg-1·min-1; n = 27) and higher fit groups (V̇o2peak = 35.4 ± 5.5 ml·kg-1·min-1; n = 20) after a test of cycling peak power output (PPO). In randomized order, participants undertook moderate-intensity continuous exercise (MICE; 40% PPO) or high-intensity interval cycling exercise (HIIE; 70% PPO) or no-exercise control. Brachial FMD was assessed at rest and 10 and 60 min after exercise. FMD increased after MICE in both groups {increase of 0.86% [95% confidence interval (CI), 0.17-1.56], P = 0.01} and normalized after 60 min. In the lower fit group, FMD was reduced after HIIE [reduction of 0.85% (95% CI, 0.12-1.58), P = 0.02] and remained decreased at 60 min. In the higher fit group, FMD was unchanged immediately after HIIE and increased after 60 min [increase of 1.52% (95% CI, 0.41-2.62), P < 0.01, which was correlated with V̇o2peak, r = 0.41; P < 0.01]. In the no-exercise control, FMD was reduced in both groups after 60 min (P = 0.05). Exercise intensity alters the acute FMD response in elderly men and V̇o2peak modulates the FMD response following HIIE but not MICE. The sustained decrease in FMD in the lower fit group following HIIE may represent a signal for vascular adaptation or endothelial fatigue.NEW & NOTEWORTHY This study is the first to show that moderate-intensity continuous cycling exercise increased flow-mediated dilation (FMD) transiently before normalization of FMD after 1 h, irrespective of cardiorespiratory fitness level in elderly men. Interestingly, we show increased FMD after high-intensity cycling exercise in higher fit men, with a sustained reduction in FMD in lower fit men. The prolonged reduction in FMD after high-intensity cycling exercise may be associated with future vascular adaptation but may also reflect a period of increased cardiovascular risk in lower fit elderly men.

The Influence Of Ribose Ingestion On Recovery And Performance In Healthy Individuals.

PURPOSE: Skeletal muscle adenosine triphosphate (ATP) levels are depleted during and following high intensity exercise. Previous studies have shown that recovery of these lower ATP levels can take days, which ultimately can affect performance. Ribose has been shown to enhance the recovery in ATP; however, how is performance affected with this metabolic recovery? Therefore, we investigated the influence of ingesting 10 g/day of D-ribose (DR) on muscular recovery, performance, and metabolism during and following a multi-day exercise regimen. METHODS: A double blind, crossover study in 18 healthy subjects compared 10 g/day of DR to 10 g/day of dextrose (DEX, control). All subjects completed 2 days of loading with either DR or DEX, followed by 3 days of additional supplemental treatment, as well as undergoing high intensity interval exercise. Exercise assessment protocol consisted of cycling for 60 min (8 min of exercise at 60% and 2 min at 80% VO2max), followed by a 2 min power test evaluation (PO). RESULTS: Mean and peak PO increased from day 1 to day 3 by 2% (p = 0.04) and 6% (p = 0.03), respectively, for DR, but was only maintained with DEX. Rating of Perceived Exertion (RPE) was significantly lower for DR than DEX. Subjects were then further assessed between the low and high VO2max values. The lower VO2max subjects had a significant increase in CK (by 57%), as well as a 4% greater increase in HR, and greater RPE with DEX as compared to DR. Further, in the lower VO2max DR subjects, there was a significantly lower exercising HR and RPE (13.1 +/- 1.7 vs. 13.7 +/- 1.5), and an improvement in PO. No differences in HR, CK, BUN, GLUC, or lactate were found between either supplement. However, there was a 40% increase in the main effect of time for CK elevation regardless of treatment. CONCLUSIONS: DR supplementation led to greater performance changes than DEX during and following high intensity interval cycling exercise. Furthermore, upon sub group analysis between VO2max differences revealed additional benefits with DR. DR supplementation within this lower VO2max group resulted in maintenance in exercise performance, as well as potentially lessening muscular cell damage which can greatly influence cellular recovery and subsequent performance.

PGC-1α transcriptional response and mitochondrial adaptation to acute exercise is maintained in skeletal muscle of sedentary elderly males

The aim of the present study was to examine the effects of ageing and training status on (1) markers of skeletal muscle mitochondrial content and (2) the ability to activate the acute signalling pathways associated with regulating exercise-induced mitochondrial biogenesis. Muscle biopsies were obtained from the vastus lateralis muscle of young untrained (24 ± 4 years, n = 6; YU), young trained (22 ± 3 years, n = 6; YT), old untrained (65 ± 6 years, n = 6; OU) and old trained (64 ± 3 years, n = 6; OT) healthy males before and after (3 h and 3 days post-exercise) completion of high-intensity interval cycling exercise. In resting muscle, lifelong training preserved mtDNA, PGC-1α and COXIV protein content such that muscles from OT individuals were comparable to muscles from both YU and YT individuals, whereas lifelong sedentary behaviour reduced such markers of mitochondrial content. Regardless of age or training status, acute exercise induced comparable increases in p38MAPK phosphorylation immediately post-exercise, PGC-1α and COXIV mRNA expression at 3 h post-exercise and COXIV protein at 3 days post-exercise. Data demonstrate that lifelong endurance training preserves skeletal muscle PGC-1α content and that despite the mitochondrial dysfunction typically observed with sedentary ageing, muscles from sedentary elderly individuals retain the capacity to activate the acute signalling pathways associated with regulating the early processes of mitochondrial biogenesis. We consider our data to have immediate translational potential as they highlight the potential therapeutic effects of exercise to induce skeletal muscle mitochondrial biogenesis persist late in adulthood, even after a lifetime of physical inactivity.