High-intensity Treadmill Running Research Articles

Exercise Impacts The Global Profile Of MiRNA In Plasma And Skeletal Muscle In Hypertensive Rats

MiRNAs play a role in several physiological processes and in the development of pathologies, such as hypertension. These molecules have also been implicated in the adaptation to exercise, but information is still scarce. Since regular exercise practice is indicated to prevent and help treat hypertension, understanding the molecular mechanisms involved in the adaptation to exercise is crucial. PURPOSE: Our aim was to determine the global profile of miRNA in plasma and skeletal muscle of hypertensive rats by next generation sequencing (NGS). METHODS: Twelve spontaneously hypertensive rats were kept sedentary or subjected to low or high intensity treadmill running (60 and 80% of the Vmax). Rats trained for 20 min 5 days a week for 8 weeks. Aerobic capacity was measured before, during and after training and their arterial blood pressure was measured weekly. MiRNAs were obtained from plasma and gastrocnemius, then sequenced by NGS on Illumina platform. Sequence reads were mapped and counted against miRBase by bowtie and normalized with TMM normalization approach. Differential analysis was performed by edgeR method. RESULTS: While blood pressure increased in sedentary rats, it decreased in exercised animals, particularly in the high intensity group. Eighteen miRNAs were differentially expressed (DEmiRNAs) in plasma and 16 in skeletal muscle, with only 3 in common: miR-192-5p, -27b-3p and -150-5p. While most were increased in plasma, most were decreased in muscle. Among the DEmiRNAs were those enriched in muscle, kidneys, endothelium and adipocytes. MiR-192 has been associated with kidney function, particularly blood pressure regulation, and miR-27b has been linked with hypertension in rats. Here miR-192 was increased in plasma and muscle and miR-27b was decreased in muscle and increased in plasma, suggesting they could be involved in the reduction of blood pressure due to exercise. Few of the DEmiRNAs have been reported in association to exercise, but those that have included miR-133a, -133b, -29a, -26a, -378a and -486. CONCLUSION: This is the first study to obtain a global profile of circulating and muscle miRNAs by NGS in response to exercise in hypertension, thus contributing to a broader view of the possible miRNAs involved in the adaptation to chronic exercise in hypertensive animals. Supported by CNPq, CAPES, UCB

No Effect of Exercise Intensity on Appetite in Highly-Trained Endurance Women.

In endurance-trained men, an acute bout of exercise is shown to suppress post-exercise appetite, yet limited research has examined this response in women. The purpose of this study was to investigate the effect of exercise intensity on appetite and gut hormone responses in endurance-trained women. Highly-trained women (n = 15, 18–40 years, 58.4 ± 6.4 kg, VO2MAX = 55.2 ± 4.3 mL/kg/min) completed isocaloric bouts (500 kcals or 2093 kJ) of moderate-intensity (MIE, 60% VO2MAX) and high-intensity (HIE, 85% VO2MAX) treadmill running at the same time of day, following a similar 48-h diet/exercise period, and at least 1-week apart. Blood was drawn pre-exercise (baseline), immediately post-exercise and every 20-min for the next 60-min. Plasma concentrations of acylated ghrelin, PYY3–36, GLP-1 and subjective appetite ratings via visual analog scale (VAS) were assessed at each time point. Acylated ghrelin decreased (p = 0.014) and PYY3–36 and GLP-1 increased (p = 0.036, p < 0.0001) immediately post-exercise, indicating appetite suppression. VAS ratings of hunger and desire to eat decreased immediately post-exercise (p = 0.0012, p = 0.0031, respectively), also indicating appetite suppression. There were no differences between exercise intensities for appetite hormones or VAS. Similar to males, post-exercise appetite regulatory hormones were altered toward suppression in highly-trained women and independent of energy cost of exercise. Results are important for female athletes striving to optimize nutrition for endurance performance.

Influence of preliminary exercise training on muscle damage indices in rats after one bout of prolonged treadmill exercise.

[Purpose] The purpose of this study was to investigate the effects of exercise on muscle damage indices in male Sprague-Dawley rats. Two groups of rats were trained in either moderate- or high-intensity treadmill running for 4 weeks. Subsequently, the concentrations of creatine kinase, lactate dehydrogenase, and high-sensitivity C-reactive protein were examined following a single bout of prolonged (3-h) intensive exercise. [Subjects and Methods] The study included forty 6-week-old male Sprague-Dawley rats weighing 150–180 g each. The aerobic exercise group was divided into high-intensity (28 m/min) and moderate-intensity (15 m/min) subgroups. Both subgroups were trained for 35 min daily for 6 days per week (excluding Sunday) over a 4-week period. Following training, the high- and moderate-intensity exercise groups and a non-exercise group performed one bout of prolonged (3-h) treadmill exercise for 3 hours at a speed of 15 m/min. [Results] Creatine kinase and lactate dehydrogenase levels differed significantly among the groups. [Conclusion] The preliminary exercise groups showed lower muscle damage and inflammatory response levels than the non-exercise group after the bout of prolonged intensive exercise.

Acute Exercise and Oxidative Stress: CrossFit(™) vs. Treadmill Bout.

CrossFit™, a popular high-intensity training modality, has been the subject of scrutiny, with concerns of elevated risk of injury and health. Despite these concerns empirical evidence regarding physiologic stresses including acute oxidative stress is lacking. Therefore, the purpose of this investigation was to examine the acute redox response to a CrossFit™ bout. Furthermore, these findings were compared to a high-intensity treadmill bout as a point of reference. Ten males 26.4 ± 2.7 yrs having three or more months of CrossFit™ experience participated in the present study. Blood plasma was collected at four time points: Pre-exercise (PRE), immediately-post-exercise (IPE), 1 hr-post (1-HP) and 2 hr-post (2-HP), to examine oxidative damage and antioxidant capacity. Regarding plasma oxidative damage, CrossFit™ and Treadmill elicited a time-dependent increase of lipid peroxides 1-HP (CrossFit™=+143%, Treadmill=+115%) and 2-HP (CrossFit™=+256%, Treadmill+167%). Protein Carbonyls were increased IPE in CF only (+5%), while a time-dependent decrease occurred 1-HP (CrossFit™=−16%, Treadmill=−8%) and 2-HP (CF=−16%, TM=−1%) compared to IPE. Regarding antioxidant capacity, Ferric Reducing Antioxidant Power also demonstrated a time-dependent increase within CrossFit™ and Treadmill: IPE (CrossFit™=+25%, Treadmill=+17%), 1-HP (CrossFit™=+26%, Treadmill=+4.8%), 2-HP (CrossFit™=+20%, Treadmill=+12%). Total Enzymatic Antioxidant Capacity showed a time-dependent decrease in IPE (CrossFit™=−10%, Treadmill=−12%), 1-HP (CrossFit™=−12%, Treadmill=−6%), 2-HP (CrossFit™=−7%, Treadmill=−11%). No trial-dependent differences were observed in any biomarker of oxidative stress. The CrossFit™ bout elicited an acute blood oxidative stress response comparable to a traditional bout of high-intensity treadmill running. Results also confirm that exercise intensity and the time course of exercise recovery influence oxidative responses.

The Effect Of Caffeine On Epoc Following Hiit Treadmill Running

PURPOSE: The purpose of this study was to investigate the effect of caffeine on the excess post-exercise oxygen consumption (EPOC) following high-intensity treadmill running. METHODS: Eight active males and females participated in the study (4 M & 4 F, Age 24.2 ± 8.3 years, Weight: 79 ± 24.8 kg, VO2max: 41.3 ± 8.9 ml/kg/min). The study was a double blind crossover design. Each participant performed 4 trials, 2 consisting of a 2x2 minute run on the treadmill at 108% of their VO2max and 2 trials consisting of a 3x2 minute run at the same intensity. For each trail the participant arrived 60 min before exercise, provided a blood sample and was given either caffeine (6mg/kg of body weight) or a placebo (maltodextrin). Following this, one hour of resting indirect calorimetry, heart rate, and core temperature data were collected. Following a pre-exercise blood sample, participants completed exercise while indirect calorimetry was measured as well as core temperature, HR, and RPE. Venous blood was drawn immediately following the bout of treadmill running and after an additional hour of resting data. RESULTS: VO2, RER, HR, and core temperature increased post exercise (p < 0.05). While not significant, RER tended to be higher 60 min post exercise in caffeine vs. placebo (C: 0.90, P: 0.88). CONCLUSION: EPOC was not elevated 60 min post HIIT treadmill exercise from 6 mg/kg of caffeine supplementation vs. placebo given 60 min before exercise.

Oxidative Stress Response Of Crossfit Vs. Treadmill Running

PURPOSE: The purpose of this study was to examine the acute effects of CrossFit on blood redox changes. METHODS: 10 males 26.4 yrs (+/− 2.7yrs) with at least three months of CrossFit experience completed “Cindy” (20min of as many pull-ups, push-ups, and squats as possible) and a 20 min 90% HRmax Treadmill bout as determined by graded exercise test on separate occasions. Blood plasma was collected at 4 different time points for each trial: pre, post, 1hr post and 2hr post, to examine lipidperoxidation (LOOH) and antioxidant capacity. RESULTS: Cindy and Treadmill elicited a time dependent increase of LOOH in 1hr post (143% and 115%) and 2hr post (256% and 167%) respectively. Ferric Reducing Antioxidant Power (FRAP) also demonstrated a time dependent increase within Cindy and Treadmill bouts; post (25%, 17%), 1hr post (26%, 4.8%), 2hr (20%, 12%) respectively. Total Enzymatic Antioxidant Capacity (TEAC) showed a time dependent decrease in post (−10%, −12%), 1hr post (−12%, −6%), 2hr post (−7%, −11%) respectively. Following Cindy, trial dependent differences existed at 1hr for FRAP (+16% over Tread) and TEAC (−11% than Tread). CONCLUSIONS: CrossFit elicited an acute blood oxidative stress response that is comparable to a bout of high intensity treadmill running; however, antioxidant response to Cindy were different during recovery.

Comparison of serum fatty acid content and caloric expenditure after a single bout of moderate-intensity and high-intensity treadmill exercise in young females

Background The idea behind high-intensity interval training (HIIT) is that an individual will burn a greater amount of calories and fat in a shorter period of time than moderate-intensity exercise. While beneficial changes have been seen when HIIT is incorporated into training programs, there is still information about HIIT that is unknown. At moderate intensities, triacylglycerol is the predominate fuel source based on percentage while carbohydrates are the predominate fuel during high-intensity exercise. Serum fatty acid (FFA) can be used as marker of fat utilization during and after exercise. The purpose of this investigation was to determine the amount of FFA released during moderateintensity and high-intensity treadmill running in endurance trained females.

Effect of microtitanium impregnated tape on the recovery of triceps surae musculotendinous function following strenuous running

We previously reported increased running economy and joint range of motion (ROM) during subsequent exercise performed 48-h following strenuous exercise while wearing garments containing micro-titanium particles generated from high-pressure aqueous processing of titanium (AQUA TITANTM). Here we utilised an isolated plantarflexion triceps surae model and AQUA TITAN-treated flexible tape to determine if dermal application of the micro-titanium could account for meaningful changes in functional properties of the musculotendinous unit. In a randomised double-blind crossover, 20 trained men day 1, baseline measures, AQUA TITAN or placebo tape covering the triceps surae, intermittent high-intensity treadmill running; day 2, rest; day 3, post-stress post-treatment outcome measures. Outcomes comprised: plantarflexion ROM via isokinetic dynamometry; short latency reflex from electromyography; Achilles tendon stiffness from isometric dynamometry, ultrasonography (Achilles-medial-gastrocnemius junction), motion analysis, and force-length modelling. High-intensity exercise with placebo tape reduced tendon stiffness (-16.5%; 95% confidence limits ±8.1%; small effect size), relative to non-taped baseline, but this effect was negligible (-5.9%; ±9.2%) with AQUA TITAN (AQUA TITAN-placebo difference -11.3%; ±11.6%). Change in latency relative to baseline was trivial with placebo (1.6%; ±3.8%) but large with AQUA TITAN (-11.3%; ±3.3%). The effects on ROM with AQUA TITAN (1.6%; ±2.0%) and placebo were trivial (-1.6% ±1.9%), but the small difference (3.1%; ±2.7%) possibly greater with AQUA TITAN. AQUA TITAN tape accelerated the reflex response and attenuated reduced Achilles tendon stiffness following fatiguing exercise. Altered neuromuscular control of tendon stiffness via dermal application of micro-titanium treated materials may facilitate restoration of musculotendinous contractile performance following prior strenuous exercise.

Do metaboreceptors alter heat loss responses following dynamic exercise?

Metaboreceptor activation during passive heating is known to influence cutaneous vascular conductance (CVC) and sweat rate (SR). However, whether metaboreceptors modulate the suppression of heat loss following dynamic exercise remains unclear. On separate days, before and after 15 min of high-intensity treadmill running in the heat (35°C), eight males underwent either 1) no isometric handgrip exercise (IHG) or ischemia (CON), 2) 1 min IHG (60% of maximum, IHG), 3) 1 min IHG followed by 2 min of ischemia (IHG+OCC), 4) 2 min of ischemia (OCC), or 5) 1 min IHG followed by 2 min of ischemia with application of lower body negative pressure (IHG+LBNP). SR (ventilated capsule), cutaneous blood flow (Laser-Doppler), and mean arterial pressure (Finometer) were measured continuously before and after dynamic exercise. Following dynamic exercise, CVC was reduced with IHG exercise (P < 0.05) and remained attenuated with post-IHG ischemia during IHG+OCC relative to CON (39 ± 2 vs. 47 ± 6%, P < 0.05). Furthermore, the reduction in CVC was exacerbated by application of LBNP during post-IHG ischemia (35 ± 3%, P < 0.05) relative to IHG+OCC. SR increased during IHG exercise (P < 0.05) and remained elevated during post-IHG ischemia relative to CON following dynamic exercise (0.94 ± 0.15 vs. 0.53 ± 0.09 mg·min(-1)·cm(-2), P < 0.05). In contrast, application of LBNP during post-IHG ischemia had no effect on SR (0.93 ± 0.09 mg·min(-1)·cm(-2), P > 0.05) relative to post-IHG ischemia during IHG+OCC. We show that CVC is reduced and that SR is increased by metaboreceptor activation following dynamic exercise. In addition, we show that the metaboreflex-induced loading of the baroreceptors can influence the CVC response, but not the sweating response.

Isokinetic eccentric resistance training prevents loss in mechanical muscle function after running

The aim of the study was to verify whether 8 weeks of resistance training employing maximal isokinetic eccentric (IERT) knee extensor actions would reduce the acute force loss observed after high-intensity treadmill running exercise. It was hypothesized that specific IERT would induce protective effects against muscle fatigue and ultrastructural damages, preventing or reducing the loss in mechanical muscle function after running. Subjects were tested before and after IERT protocol for maximal isometric, concentric and eccentric isokinetic knee extensor strength (60° and 180° s(-1)). In a second session, subjects performed treadmill running (~35 min) and the previously mentioned measurements were repeated immediately after running. Subsequently, subjects were randomized to training (n = 12) consisting of 24 sessions of maximal IERT knee extensors actions at 180° s(-1), or served as controls (n = 8). The effects of acute running-induced fatigue and training on isokinetic and isometric peak torque, and rate of force development (RFD) were investigated. Before IERT, running-induced eccentric torque loss at 180° s(-1) was -8 %, and RFD loss was -11 %. Longitudinal IERT led to reduced or absent acute running-induced losses in maximal IERT torque at 180° s(-1) (+2 %), being significantly reduced compared to before IERT (p < 0.05), however, RFD loss remained at -11 % (p > 0.05). In conclusion, IERT yields a reduced strength loss after high-intensity running workouts, which may suggest a protective effect against fatigue and/or morphological damages. However, IERT may not avoid reductions in explosive muscle actions. In turn, this may allow more intense training sessions to be performed, facilitating the adaptive response to running training.

Immediate effects of a single exercise bout on protein O-GlcNAcylation and chromatin regulation of cardiac hypertrophy

Cardiac hypertrophy induced by pathological stimuli is regulated by a complex formed by the repressor element 1-silencing transcription factor (REST) and its corepressor mSin3A. We previously reported that hypertrophic signaling is blunted by O-linked attachment of β-N-acetylglucosamine (O-GlcNAc) to proteins. Regular exercise induces a physiological hypertrophic phenotype in the heart that is associated with decreased O-GlcNAc levels, but a link between O-GlcNAc, the REST complex, and initiation of exercise-induced cardiac hypertrophy is not known. Therefore, mice underwent a single 15- or 30-min bout of moderate- to high-intensity treadmill running, and hearts were harvested immediately and compared with sedentary controls. Cytosolic O-GlcNAc was lower (P < 0.05) following 15 min exercise with no differences in nuclear levels (P > 0.05). There were no differences in cytosolic or nuclear O-GlcNAc levels in hearts after 30 min exercise (P > 0.05). Cellular compartment levels of O-GlcNAc transferase (OGT, the enzyme that removes the O-GlcNAc moiety from proteins), REST, mSin3A, and histone deacetylases (HDACs) 1, 2, 3, 4, and 5 were not changed with exercise. Immunoprecipitation revealed O-GlcNAcylation of OGT and HDACs 1, 2, 4, and 5 that was not changed with acute exercise; however, exercised hearts did exhibit lower interactions between OGT and REST (P < 0.05) but not between OGT and mSin3A. These data suggest that hypertrophic signaling in the heart may be initiated by as little as 15 min of exercise via intracellular changes in protein O-GlcNAcylation distribution and reduced interactions between OGT and the REST chromatin repressor.

High-intensity interval training increases intrinsic rates of mitochondrial fatty acid oxidation in rat red and white skeletal muscle

High-intensity interval training (HIIT) can increase mitochondrial volume in skeletal muscle. However, it is unclear whether HIIT alters the intrinsic capacity of mitochondrial fatty acid oxidation, or whether such changes are associated with changes in mitochondrial FAT/CD36, a regulator of fatty acid oxidation, or with reciprocal changes in the nuclear receptor coactivator (peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1α)) and the corepressor (receptor-interacting protein 140 (RIP140)). We examined whether HIIT alters fatty acid oxidation rates in the isolated subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria of red and white skeletal muscle and (or) induces changes in muscle PGC-1α and RIP140 proteins and mitochondrial FAT/CD36 protein content. Rats were divided into untrained or HIIT-trained groups. HIIT animals performed 10 bouts of 1-min high-intensity treadmill running (30-55 m·min(-1)), separated by 2 min of rest, for 5 days a week for 4 weeks. As expected, after the training period, HIIT increased mitochondrial enzymes (citrate synthase, COXIV, and β-hydroxyacyl CoA dehydrogenase) in red and white muscle, indicating that muscle mitochondrial volume had increased. HIIT also increased the rates of palmitate oxidation in mitochondria of red (37% for SS and 19% for IMF) and white (36% for SS and 12% for IMF) muscle. No changes occurred in SS and IMF mitochondrial FAT/CD36 proteins, despite increasing FAT/CD36 at the whole-muscle level (27% for red and 22% for white). Concurrently, muscle PGC-1α protein was increased in red (22%) and white (16%) muscle, but RIP140 was not altered. These results indicate that increases in SS and IMF mitochondrial fatty acid oxidation induced by HIIT are accompanied by an increase in PGC-1α, but not RIP140 or FAT/CD36.

Heart ABCA1 and PPAR- α Genes Expression Responses in Male rats: Effects of High Intensity Treadmill Running Training and Aqueous Extraction of Black Crataegus-Pentaegyna.

Introduction:Heart as a high metabolic and aerobic tissue is consuming lipid as a fuel for its energy provision at rest during light and moderate exercise, except when lactate level is higher in blood circulation. It has been shown that any type of regular exercise and crataegus species would improve cardiovascular function and minimizes several risk factors via stimulating lipid metabolism by acting on enzymes and genes expression such as ABCA1 and PPAR α which are involving in this process.Materials and Methods:Twenty Wistar male rats (4-6 weeks old, 140-173 g weight) were used. Animals were randomly classified into training (n = 10) and control (n = 10) groups and then divided into saline-control (SC), saline-training (ST), Crataegus-Pentaegyna -control (CPC), and Crataegus-Pentaegyna -training (CPT) groups. Training groups have performed a high-intensity running program (at 34 m/min (0% grade), 60 min/day, 5 days/week) on a motor-driven treadmill for eight weeks. Animals were orally fed with Crataegus-Pentaegyna extraction (500mg/kg) and saline solution for six weeks. Seventy- two hours after the last training session, rats were sacrificed, hearts were excised, cleaned and immediately frozen in liquid nitrogen and stored at -80 °C until RNA extraction. Plasma also was collected for plasma variable measurements. Statistical analysis was performed using a two way analysis of variance, and significance was accepted at P < 0.05.Results:A non-significant (P < 0.4, P < 0.79, respectively) increase in ABCA1 and PPAR α genes expression was accompanied by a significant (P < 0.01, P < 0.04, P < 0.04, respectively) reduction in TC, TG, and VLDL-C levels in Crataegus-Pentaegyna groups.Conclusions:Our findings show that a high intensity treadmill running was able to express ABCA1 and PPAR α in rat heart. Data also possibly indicate that the Crataeguse-Pentaegyna supplementation solely could mimic training effect on the mentioned genes and lipid profiles via different mechanism(s).

Paper 221: Neuromuscular Response of the Reconstruced Leg is Diminished During a Heavy Intensity Running Bout

IntroductionEfficient neuromuscular response provides shock-absorption and protection of the graft and cartilage following anterior cruciate ligament reconstruction. The purpose of the present study was to investigate if accumulation of metabolic fatigue may impair the neuromuscular response of the reconstructed leg during high intensity treadmill running.

Metabolism and performance during extended high-intensity intermittent exercise after consumption of low- and high-glycaemic index pre-exercise meals

The metabolic and performance benefits of prior consumption of low-glycaemic index (GI) meals v. high-GI meals were determined in extended high-intensity intermittent exercise. Participants (ten males and four females, aged 25·8 (sd 7·3) years) completed two testing days (each consisting of back-to-back 90-min intermittent high-intensity treadmill running protocols separated by 3 h) spaced by at least 7 d. Using a randomised counterbalanced cross-over design, low-GI, lentil-based meals (GI about 42) or high-GI, potato-based meals (GI about 78) matched for energy value were consumed 2 h before, and within 1 h after, the first exercise session. Performance was measured by the distance covered during five 1-min sprints (separated by 2·5 min walking) at the end of each exercise session. Peak postprandial blood glucose was higher by 30·8 % in the high-GI trial compared with the low-GI trial, as was insulin (P = 0·039 and P = 0·003, respectively). Carbohydrate oxidation was lower by 5·5 % during the low-GI trials compared with the high-GI trials at the start of the first exercise session (P < 0·05). Blood lactate was significantly higher (6·1 v. 2·6 mmol/l; P = 0·019) and blood glucose significantly lower (4·8 v. 5·4 mmol/l; P = 0·039) at the end of the second exercise session during the high-GI trial compared with the low-GI trial. Sprint distance was not significantly different between conditions. A low-GI meal improved the metabolic profile before and during extended high-intensity intermittent exercise, but did not affect performance. Improvements in metabolic responses when consuming low-GI meals before exercise may be beneficial to the long-term health of athletes.

The Effect Of Resistance And Aerobic Exercise On Plasma Total Pyy And Acylated Ghrelin Concentrations

The gut hormones ghrelin (appetite-stimulating) and PYY (appetite-reducing) are involved in the regulation of body weight. Research shows that acylated ghrelin is suppressed and total PYY increases during high intensity aerobic exercise, but there is a paucity of data on resistance exercise. PURPOSE: To assess the effect of treadmill running and free weight resistance exercise on plasma acylated ghrelin and total PYY concentrations. METHODS: 12 healthy males (age 21.2 ± 1.1 y, body mass 74.4 ± 8.3 kg, BMI 23.4 ± 1.6 kg·m−2, VO2max 62.0 ± 6.1 mL·kg−1·min−1, mean ± SD) undertook 3, 8 h trials (aerobic, resistance and control) in a random crossover design. All trials began in the morning after an overnight fast. On the aerobic trial participants ran for 60 min at 68 ± 2 % of VO2max then rested for 7 h. On the resistance trial participants completed a 90 min free weight session performing 3 sets of 12 reps of 10 different exercises at 80% of 12 rep max, then rested for 6.5 h. On the control trial participants rested for 8 h. Venous plasma was taken at 0, 0.75, 1.5, 2, 2.5, 5, 5.5 and 8 h and acylated ghrelin and total PYY concentrations measured using enzyme immunoassay (SPI-BIO and Diagnostic System Laboratories respectively). RESULTS: Acylated ghrelin was suppressed during resistance and aerobic exercise (two-way ANOVA, time P = 0.001, trial × time P = 0.035). Post hoc analysis indicated between trial differences for aerobic and control at 0.75 h and between resistance and control at 0.75 and 1.5 h. After adjusting for multiple comparisons the only difference to remain significant was between resistance and control at 1.5 h. Total PYY increased during aerobic but not during resistance exercise (two-way ANOVA, trial P < 0.01, time P < 0.01, trial × time interaction P = 0.027). Post hoc analysis indicated trial differences between control and aerobic (P = 0.038) and resistance and aerobic (P = 0.028). CONCLUSION: Acylated ghrelin is suppressed and total PYY increases during high intensity treadmill running. Resistance exercise suppresses acylated ghrelin but there is no effect on total PYY.

‘Priming’ exercise and O2 uptake kinetics during treadmill running

We tested the hypothesis that priming exercise would speed V(O2) kinetics during treadmill running. Eight subjects completed a square-wave protocol, involving two bouts of treadmill running at 70% of the difference between the running speeds at lactate threshold (LT) and V(O2) max, separated by 6-min of walking at 4 km h(-1), on two occasions. Oxygen uptake was measured breath-by-breath and subsequently modelled using non-linear regression techniques. Heart rate and blood lactate concentration were significantly elevated prior to the second exercise bout compared to the first. However, V(O2) kinetics was not significantly different between the first and second exercise bouts (mean+/-S.D., phase II time constant, Bout 1: 16+/-3s vs. Bout 2: 16+/-4s; V(O2) slow component amplitude, Bout 1: 0.24+/-0.10 L min(-1)vs. Bout 2: 0.20+/-0.12 L min(-1); mean response time, Bout 1: 34+/-4s vs. Bout 2: 34+/-6s; P>0.05 for all comparisons). These results indicate that, contrary to previous findings with other exercise modalities, priming exercise does not alter V(O2) kinetics during high-intensity treadmill running, at least in physically active young subjects. We speculate that the relatively fast V(O2) kinetics and the relatively small V(O2) slow component in the control ('un-primed') condition negated any enhancement of V(O2) kinetics by priming exercise in this exercise modality.

The effects of nightly normobaric hypoxia and high intensity training under intermittent normobaric hypoxia on running economy and hemoglobin mass

We investigated the effects of nightly intermittent exposure to hypoxia and of training during intermittent hypoxia on both erythropoiesis and running economy (RE), which is indicated by the oxygen cost during running at submaximal speeds. Twenty-five college long- and middle- distance runners [maximal oxygen uptake (Vo(2max)) 60.3 +/- 4.7 ml x kg(-1) x min(-1)] were randomly assigned to one of three groups: hypoxic residential group (HypR, 11 h/night at 3,000 m simulated altitude), hypoxic training group (HypT), or control group (Con), for an intervention of 29 nights. All subjects trained in Tokyo (altitude of 60 m) but HypT had additional high-intensity treadmill running for 30 min at 3,000 m simulated altitude on 12 days during the night intervention. Vo(2) was measured at standing rest during four submaximal speeds (12, 14, 16, and 18 km/h) and during a maximal stage to volitional exhaustion on a treadmill. Total hemoglobin mass (THb) was measured by carbon monoxide rebreathing. There were no significant changes in Vo(2max), THb, and the time to exhaustion in all three groups after the intervention. Nevertheless, HypR showed approximately 5% improvement of RE in normoxia (P < 0.01) after the intervention, reflected by reduced Vo(2) at 18 km/h and the decreased regression slope fitted to Vo(2) measured during rest position and the four submaximal speeds (P < 0.05), whereas no significant corresponding changes were found in HypT and Con. We concluded that our dose of intermittent hypoxia (3,000 m for approximately 11 h/night for 29 nights) was insufficient to enhance erythropoiesis or Vo(2max), but improved the RE at race speed of college runners.

Dietary Carnosine And Anserine Inhibits High-intensity Exercise-induced Decrease In Rat Sarcoplasmic Reticulum Ca2+ -handling

Carnosine and anserine are histidine-containing dipeptides that are present in the brain, heart, skin, liver, kidney and skeletal muscle. Various physiological actions have been ascribed to carnosine in skeletal muscle including pH buffering, acting as an antioxidant, the regulation of Ca2+sensitivity and excitation-contraction (E-C) coupling. PURPOSE: The hypothesis tested in this study was that dietary chicken breast extract (CBEX), a rich source of carnosine and anserine, would attenuate deteriorations in sarcoplasmic reticulum (SR) function that occur with high-intensity exercise. METHODS: The CBEX was prepared from the pectoralis major muscles of chicken and mixed with 9 volumes of standard rat chow. Following 5 weeks of dietary CBEX, SR Ca2+-uptake rate, Ca2+-release rate and Ca2+-stimutated ATPase activity were examined in homogenates of the superficial portion of vastus lateralis muscles from rats subjected to high-intensity treadmill running for 2.5 min. RESULTS: Dietary CBEX caused an approximately 15 and 45% increased (P < 0.01) in the muscle carnosine and anserine concentrations, respectively, but no changes in the SR Ca2+-handling ability, i.e., Ca2+-uptake and release rates, in resting muscle. Our data confirm that high-intensity exercise evokes depressions in SR Ca2+-handling. In spite of the same run time, SR Ca2+-handling was reduced to a lesser degree in muscle from CBEX-containing chow-fed rats, compared to standard chow-fed rat. Alterations in SR Ca2+-ATPase activity were not paralleled by those in Ca2+-uptake. Dietary CBEX elicited a 12.4% reduction (P < 0.05) in the catalytic activity of resting muscle. After exercise, the activity was depressed to similar extents between CBEX-containing chowand standard chow-fed rats. CONCLUSIONS: These results implicate the modified SR Ca2+-handling ability as one contributor to inhibition of the fatigue development resulting from carnosine and anserine.

The Expression of MMP-2 Following Immobilization and High-Intensity Running in Plantaris Muscle Fiber in Rats

The effect of 2-week, high-intensity running and a 2-week immobilization on muscle fiber type composition of the plantaris muscle from 18 female, 6-month-old Wistar rats (running, n = 6; immobilization, n = 6; sedentary control, n = 6) was bio- and histochemically investigated. The high-intensity treadmill running began with 20 min (32 m/min, 0% gradient, 75% VO2 max), up to 50 min/day. Right hind limbs were immobilized by an external fixation procedure for 13 days. Muscle mass of the plantaris muscle in the immobilized groups was reduced by 16% in comparison with the sedentary control group. High-intensity running and immobilization increased both mRNA and protein levels of matrix metalloproteinase type 2 (MMP-2) in plantaris. Running and immobilization decreased the percentages of transverse sectional area of fast-twitch glycolytic (FG) type IIb fibers, running increased relative cross-sectional area of fast-twitch oxidative glycolytic (FOG) type IIa muscle fibers, whereas immobilization increased relative cross-sectional area of slow-twitch oxidative (SO) muscle fibers (type I). Our results suggest that both high-intensity running and immobilization are enough to induce overwhelming changes in plantaris.