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Exercise Intensity (exercise + intensity)
Selected AbstractsRed Cell Pulmonary Transit Times Through the Healthy Human LungEXPERIMENTAL PHYSIOLOGY, Issue 2 2003G. S. Zavorsky It has previously been postulated that rapid red cell capillary transit through the human lung plays a role in the mechanism of diffusion limitation in some endurance athletes. Methodological limitations currently prevent researchers from directly measuring pulmonary capillary transit times in humans during exercise; however, first pass radionuclide cardiography allows direct measurement of red blood cell (RBC) transit times through the whole lung at various exercise intensities. We examined the relationship between mean whole lung red cell pulmonary transit times (cardiopulmonary transit times or CPTT) and different levels of flow in 88 healthy humans (76 males, 12 females) from several studies (mean age 31 years). The pooled data suggest that the relationship between CPTT and cardiac index (CI), beginning at rest and progressing through to maximum exercise demonstrates that CPTT reaches its minimum value when CI is about 8.1 l m2 min,1 (2.5-3 times the CI value at rest), and does not significantly change with further increases in CI. Cardiopulmonary blood volume (CPBV) index also does not change significantly until CI reaches 2.5 to 3 times the CI value at rest and then increases roughly linearly after that point. Consequently, the systematic increase in CPBV index with increasing pulmonary blood flow between 8.1 and 20 l m2 min,1 displays an adaptive response of the cardiopulmonary system by augmenting CPBV (and perhaps pulmonary capillary blood volume through distension and recruitment) to offset the reduction in CPTT, as no significant difference in mean CPTT is observed between these levels of flow (P > 0.05). Therefore, these data demonstrate that CPBV does not reach maximum capacity during strenuous or maximum exercise. This does not support the principle of quarter-power allometric scaling for flow when explaining modifications during exercise. Therefore, we speculate that the observed relationships between CPTT, CBPV index and flow may prevent mean CPTT (and perhaps mean pulmonary capillary transit times) from decreasing below the threshold time required for oxygenation. [source] Contraction-induced changes in skeletal muscle Na+,K+ pump mRNA expression , importance of exercise intensity and Ca2+ -mediated signallingACTA PHYSIOLOGICA, Issue 4 2010N. B. Nordsborg Abstract Aim:, To investigate if exercise intensity and Ca2+ signalling regulate Na+,K+ pump mRNA expression in skeletal muscle. Methods:, The importance of exercise intensity was evaluated by having trained and untrained humans perform intense intermittent and prolonged exercise. The importance of Ca2+ signalling was investigated by electrical stimulation of rat soleus and extensor digitorum longus (EDL) muscles in combination with studies of cell cultures. Results:, Intermittent cycling exercise at ,85% of VO2peak increased (P < 0.05) ,1 and ,1 mRNA expression ,2-fold in untrained and trained subjects. In trained subjects, intermittent exercise at ,70% of VO2peak resulted in a less (P < 0.05) pronounced increase (,1.4-fold; P < 0.05) for ,1 and no change in ,1 mRNA. Prolonged low intensity exercise increased (P < 0.05) mRNA expression of ,1 ,3.0-fold and ,2 ,1.8-fold in untrained but not in trained subjects. Electrical stimulation of rat soleus, but not EDL, muscle increased (P < 0.05) ,1 mRNA expression, but not when combined with KN62 and cyclosporin A incubation. Ionomycin incubation of cultured primary rat skeletal muscle cells increased (P < 0.05) ,1 and reduced (P < 0.001) ,2 mRNA expression and these responses were abolished (P < 0.05) by co-incubation with cyclosporin A or KN62. Conclusion:, (1) Exercise-induced increases in Na+,K+ pump ,1 and ,1 mRNA expression in trained subjects are more pronounced after high- than after moderate- and low-intensity exercise. (2) Both prolonged low and short-duration high-intensity exercise increase ,1 mRNA expression in untrained subjects. (3) Ca2+i regulates ,1 mRNA expression in oxidative muscles via Ca2+/calmodulin-dependent protein kinase (CaMK) and calcineurin signalling pathways. [source] Electromyographic activity of the palatinus and palatopharyngeus muscles in exercising horsesEQUINE VETERINARY JOURNAL, Issue 5 2007S. J. HOLCOMBE Summary Reasons for performing study: Determining the respiratory related activity of the palatinus and palatopharyngeus muscles in exercising horses is relevant because dysfunction of these muscles has been implicated in the pathogenesis of dorsal displacement of the soft palate. Objective: To determine if the palatinus and palatopharyngeus muscles have respiratory activity that increases with intensity in exercising horses. Methods: Electromyographic activity was measured in the palatinus and palatopharyngeus muscles using bipolar fine-wire electrodes while the horses completed an incremental exercise treadmill protocol. Results: Both muscles displayed synchronous expiratory activity that increased significantly (P<0.05) with exercise intensity. Phasic expiratory activity of the palatinus increased 390 ± 98%, whereas phasic expiratory activity of the palatopharyngeus increased by 198 ± 30% as the treadmill speed increased from 6 to 12 m/s. Conclusions: The palatinus and palatopharyngeus muscles may be important respiratory muscles, functioning to stabilise the position of the soft palate during intense exercise. Clinical relevance: The predominant expiratory activity of these muscles may be associated with specific muscle function related to exercise or distinct upper airway phenomena of an obligate nasal breather, such as the horse. [source] Retrospective study of predictive variables for maximal heart rate (HRmax) in horses undergoing strenuous treadmill exerciseEQUINE VETERINARY JOURNAL, Issue S36 2006T. L. VINCENT Summary Reasons for performing study: Heart rate is one of the most commonly measured variables in equine exercise physiology and relative exercise intensity commonly expressed as % of maximal heart rate. A number of influences affect maximal heart rate (HRmax), including age of the horse but other factors have not been described. Objectives: To determine if fitness, health status, gender, breed, athletic use, body mass, in addition to age, are predictive of HRmax in the horse. Methods: Maximal heart rate data from 328 horses which underwent treadmill exercise tests at 5 different laboratories were obtained retrospectively. Univariable linear regression analyses were performed on individual variables. Multiple linear regression analysis using a backward elimination modelling procedure was then used to relate the observed HRmax values simultaneously with different predictive variables. Variables were retained in the final regression model if they or any of their categories were significantly predictive of HRmax at P<0.05 and if there was a significant collective contribution to the model from inclusion of each variable, also at P<0.05. Results: Age, fitness status, laboratory, gender and breed/use (combined category) were all statistically significantly predictive of HRmax. Together these variables accounted for 41% of the variance in HRmax. Age alone accounted for only ,13% of the variation between horses in HRmax. Neither body mass nor health status were significantly predictive. Conclusions: HRmax in the horse declines with age but is also influenced by other factors. As the factors investigated accounted for only 41% of the variation between horses, other unidentified variables with a strong influence on HRmax remain to be identified. Potential relevance: Factors such as fitness, age, gender, breed and use need to be considered when interpreting estimates or measurements of HRmax. [source] Recruitment pattern of muscle fibre type during flat and sloped treadmill running in Thoroughbred horsesEQUINE VETERINARY JOURNAL, Issue S36 2006D. ETO Summary Reasons for performing the study: There is little information about the muscle fibre recruitment pattern during sloped and flat track running in Thoroughbred horses. Objectives: To examine the glycogen depletion pattern of each muscle fibre type during running on a flat and sloped treadmill. Methods: Thirteen Thoroughbred horses (3,9 years old) were used. They were initially subjected to incremental exercise tests on a treadmill at 10 and 0% inclines in each horse to determine running speed at 90 and 60% VO2max. Needle biopsy samples were obtained from the middle gluteal muscle immediately after the running at 90% VO2max for 4 min and 60% VO2max for 12 min on 10% and 0% inclines treadmill. Four muscle fibre types (Types I, IIA, IIA/IIX, and IIX) were immunohistochemically identified, and optical density of Periodic Acid Schiff staining (OD-PAS) in each fibre type and the glycogen content of the muscle sample were determined by quantitative histochemical and biochemical procedures. Results: The changes in OD-PAS showed that the recruitment of all fibre types were identical after each exercise bout, i.e., 4 min running at 90% VO2max (8.4,9.4 m/sec on 10%, 13.9,14.1 m/sec on 0%), and 12 min running at 60% VO2max (5.4,6.0 m/sec on 10%, 7.9,11.2 m/sec on 0%). No significant differences were found in the recruitment patterns of each muscle fibre type between 10 and 0% inclined exercise bouts at the same exercise intensity. Conclusions: The recruitment pattern of muscle fibre type is mainly determined by exercise intensity (%VO2max) and duration, but not by running speed. Potential relevance: The results of this study indicate the possibility that up-hill running results in the same training effect as faster running on a flat track. [source] Effects of inhalation of albuterol sulphate, ipratroprium bromide and frusemide on breathing mechanics and gas exchange in healthy exercising horsesEQUINE VETERINARY JOURNAL, Issue 3 2001W. M. BAYLY Summary The possibility that pre-exercise inhalation of a bronchodilator by healthy horses could improve their mechanics of breathing and enhance performance was investigated. Ipratropium bromide (0.35 ,g/kg bwt; n = 7) was administered by nebulisation 30 min before exercise and frusemide (1 mg/kg bwt; n = 6) was given in the same manner 2 h before exercise. Albuterol sulphate (360 and 720 ,g; n = 7) were administered with a metered dose inhaler 2 h before exercise. Each drug was investigated independently of the others using cross-over protocols. Horses completed incremental exercise tests and oxygen consumption, carbon dioxide production, arterial blood gases, heart rate and measures of breathing mechanics including total pulmonary resistance (RL) and nasopharyngeal resistance (RU) were determined for each exercise intensity. The resistance of the lower airways was calculated subsequently from the difference between RL and RU. None of the drugs tested had an effect on any of the variables measured, possibly because maximal bronchodilation is stimulated in healthy horses by the normal sympathoadrenergic response to exercise. Therefore, the pre-exercise inhalation of a bronchodilator by a healthy horse is unlikely to improve performance capacity. [source] Abnormal vascular reactivity at rest and exercise in obese boysEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2 2009L. Karpoff Abstract Background, Obese children exhibit vascular disorders at rest depending on their pubertal status, degree of obesity, and level of insulin resistance. However, data regarding their vascular function during exercise remain scarce. The aims of the present study were to evaluate vascular morphology and function at rest, and lower limb blood flow during exercise, in prepubertal boys with mild-to-moderate obesity and in lean controls. Materials and methods, Twelve moderately obese prepubertal boys [Body Mass Index (BMI: 23·9 ± 2·6 kg m,2)] and thirteen controls (BMI:17·4 ± 1·8 kg m,2), matched for age (mean age: 11·6 ± 0·6 years) were recruited. We measured carotid intima-media thickness (IMT) and wall compliance and incremental elastic modulus, resting brachial flow-mediated dilation (FMD) and nitrate-dependent dilation (NDD), lower limb blood flow during local knee-extensor incremental and maximal exercise, body fat content (DEXA), blood pressure, blood lipids, insulin and glucose. Results, Compared to lean controls, obese boys had greater IMT (0·47 ± 0·06 vs. 0·42 ± 0·03 mm, P < 0·05) but lower FMD (4·6 ± 2·8 vs. 8·8 ± 3·2%, P < 0·01) in spite of similar maximal shear rate, without NDD differences. Lower limb blood flow (mL min,1·100 g,1) increased significantly from rest to maximal exercise in both groups, although obese children reached lower values than lean counterparts whatever the exercise intensity. Conclusions, Mild-to-moderate obesity in prepubertal boys without insulin resistance is associated with impaired endothelial function and blunted muscle perfusion response to local dynamic exercise without alteration of vascular smooth muscle reactivity. [source] Muscle afferent contributions to the cardiovascular response to isometric exerciseEXPERIMENTAL PHYSIOLOGY, Issue 6 2004James P. Fisher The cardiovascular response to isometric exercise is governed by both central and peripheral mechanisms. Both metabolic and mechanical stresses on the exercising skeletal muscle produce cardiovascular change, yet it is often overlooked that the afferent signal arising from the muscle can be modified by factors other than exercise intensity. This review discusses research revealing that muscle fibre type, muscle mass and training status are important factors in modifying this peripheral feedback from the active muscles. Studies in both animals and humans have shown that the pressor response resulting from exercise of muscle with a faster contractile character and isomyosin content is greater than that from a muscle of slower contractile character. Athletic groups participating in training programmes that place a high anaerobic load on skeletal muscle groups show attenuated muscle afferent feedback. Similarly, longitudinal studies have shown that specific local muscle training also blunts the pressor response to isometric exercise. Thus it appears that training may decrease the metabolic stimulation of muscle afferents and in some instances chronic exposure to the products of anaerobic metabolism may blunt the sensitivity of the muscle metaboreflex. There may be surprising parallels between the local muscle conditions induced in athletes training for longer sprint events (e.g. 400 m) and by the low-flow conditions in, for example, the muscles of chronic heart failure patients. Whether their similar attenuations in muscle afferent feedback during exercise are due to decreased metabolite accumulation or to a desensitization of the muscle afferents is not yet known. [source] Can physical activity modulate pancreatic cancer risk? a systematic review and meta-analysisINTERNATIONAL JOURNAL OF CANCER, Issue 12 2010Michael A. O'Rorke Abstract Numerous epidemiological studies have examined the association between physical activity and pancreatic cancer; however, findings from individual cohorts have largely not corroborated a protective effect. Among other plausible mechanisms, physical activity may reduce abdominal fat depots inducing metabolic improvements in glucose tolerance and insulin sensitivity, thereby potentially attenuating pancreatic cancer risk. We performed a systematic review to examine associations between physical activity and pancreatic cancer. Six electronic databases were searched from their inception through July 2009, including MEDLINE and EMBASE, seeking observational studies examining any physical activity measure with pancreatic cancer incidence/mortality as an outcome. A random effects model was used to pool individual effect estimates evaluating highest vs. lowest categories of activity. Twenty-eight studies were included. Pooled estimates indicated a reduction in pancreatic cancer risk with higher levels of total (five prospective studies, RR: 0.72, 95% CI: 0.52,0.99) and occupational activity (four prospective studies, RR: 0.75, 95% CI: 0.59,0.96). Nonsignificant inverse associations were seen between risks and recreational and transport physical activity. When examining exercise intensity, moderate activity appeared more protective (RR: 0.79, 95% CI: 0.52,1.20) than vigorous activity (RR: 0.97, 95% CI: 0.85,1.11), but results were not statistically significant and the former activity variable incorporated marked heterogeneity. Despite indications of an inverse relationship with higher levels of work and total activity, there was little evidence of such associations with recreational and other activity exposures. [source] Meta-analysis of the effects of respiratory rehabilitation programmes on exercise capacity in accordance with programme characteristicsJOURNAL OF CLINICAL NURSING, Issue 1 2007HyunSoo Oh PhD Aims and objectives., This study was performed to investigate the effects of respiratory rehabilitation programmes on exercise capacity in terms of the programme type, the protocol used and other programme characteristics. Background., As the suitable rehabilitation programmes have not been specified, diverse programmes are provided in clinics. Design., Meta-analysis of the primary study results Methods., A computerized search through MEDLINE and CINHAL in addition to tracking down references cited in bibliographies of primarily searched studies were performed to obtain sample studies. Finally 19 research reports were examined. Results., The results of meta-regression showed that the combined effect size of the programmes on exercise capacity was unaffected by forced expiratory volume (in one second), age, the duration and frequency of the programme, or study quality. In addition, the results of meta- anova indicated that the combined effect size was not affected by (i) whether a programme was hospital based or not, (ii) whether a programme was lower-extremity or combined low- and upper-extremity exercise training, (iii) measurement time, and (iv) exercise intensity. Conclusions., The effects of programmes on exercise capacity were not differed in terms of the places where rehabilitation programmes were applied, programme content, measurement time, exercise target sites of body, and the duration and frequency of the programme. Relevance to clinical practice., The results of the present study can provide objective data when constructed or applied on a respiratory rehabilitation programme in clinics. [source] Chronic fatigue syndrome: assessment of increased oxidative stress and altered muscle excitability in response to incremental exerciseJOURNAL OF INTERNAL MEDICINE, Issue 3 2005Y. JAMMES Abstract. Objectives., Because the muscle response to incremental exercise is not well documented in patients suffering from chronic fatigue syndrome (CFS), we combined electrophysiological (compound-evoked muscle action potential, M wave), and biochemical (lactic acid production, oxidative stress) measurements to assess any muscle dysfunction in response to a routine cycling exercise. Design., This case,control study compared 15 CFS patients to a gender-, age- and weight-matched control group (n = 11) of healthy subjects. Interventions., All subjects performed an incre-mental cycling exercise continued until exhaustion. Main outcome measures., We measured the oxygen uptake (Vo2), heart rate (HR), systemic blood pressure, percutaneous O2 saturation (SpO2), M-wave recording from vastus lateralis, and venous blood sampling allowing measurements of pH (pHv), PO2 (PvO2), lactic acid (LA), and three markers of the oxidative stress (thiobarbituric acid-reactive substances, TBARS, reduced glutathione, GSH, and ascorbic acid, RAA). Results., Compared with control, in CFS patients (i) the slope of Vo2 versus work load relationship did not differ from control subjects and there was a tendency for an accentuated PvO2 fall at the same exercise intensity, indicating an increased oxygen uptake by the exercising muscles; (ii) the HR and blood pressure responses to exercise did not vary; (iii) the anaerobic pathways were not accentuated; (iv) the exercise-induced oxidative stress was enhanced with early changes in TBARS and RAA and enhanced maximal RAA consumption; and (v) the M-wave duration markedly increased during the recovery period. Conclusions., The response of CFS patients to incremental exercise associates a lengthened and accentuated oxidative stress together with marked alterations of the muscle membrane excitability. These two objective signs of muscle dysfunction are sufficient to explain muscle pain and postexertional malaise reported by our patients. [source] The Effect of Using Variable Frequency Trains During Functional Electrical Stimulation CyclingNEUROMODULATION, Issue 3 2008Simona Ferrante PhD ABSTRACT Objectives., This paper describes an experimental investigation of variable frequency stimulation patterns as a means of increasing torque production and, hence, performance in cycling induced by functional electrical stimulation. Materials and Methods., Experiments were conducted on six able-bodied subjects stimulating both quadriceps during isokinetic trials. Constant-frequency trains (CFT) with 50-msec interpulse intervals and four catchlike-inducing trains (CIT) were tested. The CITs had an initial, brief, high-frequency burst of two pulses at the onset of or within a subtetanic low-frequency stimulation train. Each stimulation train consisted of the same number of pulses. The active torques produced by each train were compared. Parametric main effect ANOVA tests were performed on the active torque-time integral (TTI), on the active torque peaks and on the time needed to reach those peaks (T2P). Results., The electrical stimulation of the quadriceps produced active torques with mean peak values in the range of 1.6,3.5 Nm and a standard error below 0.2 Nm. CITs produced a significant increase of TTI and torque peaks compared with CFTs in all the experimental conditions. In particular, during the postfatigue trials, the CITs with the doublet placed in the middle of the train produced TTIs and torque peaks about 61% and 28% larger than the CFT pattern, respectively. In addition, the CITs showed the lowest reduction of the performance between prefatigue and postfatigue conditions. Conclusions., The use of CITs improves the functional electrical stimulation cycling performance compared with CFT stimulation. This application might have a relevant clinical importance for individuals with stroke where the residual sensation is still present and thus the maximization of the performance without an excessive increase of the stimulation intensity is advisable. Therefore, exercise intensity can be increased yielding a better muscle strength and endurance that may be beneficially for later gait training in individuals with stroke. [source] Does the addition of non-invasive ventilation during pulmonary rehabilitation in patients with chronic obstructive pulmonary disease augment patient outcome in exercise tolerance?PHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 1 2010A literature review Abstract Background.,Non-invasive ventilation (NIV) during exercise in patients with chronic obstructive pulmonary disease (COPD) has been shown to increase exercise time and intensity. Feasibly then, NIV during pulmonary rehabilitation will enhance post-rehabilitation training effects. The purpose of this review is to systematically consider and critique the literature concerning the effects of NIV, when used during an exercise programme in COPD patients on exercise tolerance.,Method.,An electronic literature search was completed and the reference lists of the articles that fitted the following inclusion criteria were screened. Studies that used any mode of NIV during an exercise programme with a primary outcome measure focusing on exercise tolerance and were written after the year 2000 to reflect current practice. Studies that were not written in English or had been included in previous literature reviews were excluded. The studies were then critically appraised and assigned a level of evidence based upon Scottish Intercollegiate Guidelines Network.,Results.,Twenty-eight articles were screened, of which six fitted the inclusion criteria. The methodological quality ranged from level 1, to 1+. All but one study by Bianchi et al. (2002) demonstrated a statistically significant improvement in exercise tolerance with the addition of some form of NIV during pulmonary rehabilitation. The benefits may be greater in patients with more severe airway obstruction as determined by Forced Expiration Volume (FEV), (%pred).,Conclusion.,This review would suggest that NIV may allow an increased exercise intensity and duration during pulmonary rehabilitation in patients with moderate to very severe COPD, (according to the American Thoracic Society guidelines), resulting in a greater training effect and a prolonged exercise capacity. Further research looking at long-term follow-up is recommended. Copyright © 2009 John Wiley & Sons, Ltd. [source] Intensity, repetitiveness, and directionality of habitual adolescent mobility patterns influence the tibial diaphysis morphology of athletesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009Colin N. Shaw Abstract Mobility patterns affect the loads placed on the lower limbs during locomotion and may influence variation in lower limb diaphyseal robusticity and shape. This relationship commonly forms the basis for inferring mobility patterns from hominin fossil and skeletal remains. This study assesses the correspondence between athletic histories, varying by loading intensity, repetition and directionality, measured using a recall questionnaire, and peripheral quantitative computed tomography-derived measurements of tibial diaphysis rigidity and shape. Participants included male university varsity cross-country runners (n = 15), field hockey players (n = 15), and controls (n = 20) [mean age: 22.1 (SD +/, 2.6) years]. Measurements of tibial rigidity (including J, %CA, Imax, Imin, and average cortical thickness) of both runners and field hockey players were greater than controls (P , 0.05). Differences in tibial shape (Imax/Imin, P , 0.05) between runners and hockey players reflect pronounced maximum plane (Imax) rigidity in runners, and more symmetrical hypertrophy (Imax, Imin) among hockey players. This corresponds with the generally unidirectional locomotor patterns of runners, and the multidirectional patterns of hockey players. These results support the relationship between mobility and tibial diaphysis morphology as it is generally interpreted in the anthropological literature, with greater levels of mobility associated with increased diaphyseal robusticity and shape variation. Although exercise intensity may be the primary influence on these properties, the repetitiveness of the activity also deserves consideration. In conclusion, bone morphological patterns can reflect habitual behaviors, with adaptation to locomotor activities likely contributing to variation in tibial rigidity and shape properties in archaeological and fossil samples. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] Exercise intensity-dependent regulation of peroxisome proliferator-activated receptor , coactivator-1, mRNA abundance is associated with differential activation of upstream signalling kinases in human skeletal muscleTHE JOURNAL OF PHYSIOLOGY, Issue 10 2010Brendan Egan Skeletal muscle contraction increases intracellular ATP turnover, calcium flux, and mechanical stress, initiating signal transduction pathways that modulate peroxisome proliferator-activated receptor , coactivator-1, (PGC-1,)-dependent transcriptional programmes. The purpose of this study was to determine if the intensity of exercise regulates PGC-1, expression in human skeletal muscle, coincident with activation of signalling cascades known to regulate PGC-1, transcription. Eight sedentary males expended 400 kcal (1674 kj) during a single bout of cycle ergometer exercise on two separate occasions at either 40% (LO) or 80% (HI) of,. Skeletal muscle biopsies from the m. vastus lateralis were taken at rest and at +0, +3 and +19 h after exercise. Energy expenditure during exercise was similar between trials, but the high intensity bout was shorter in duration (LO, 69.9 ± 4.0 min; HI, 36.0 ± 2.2 min, P < 0.05) and had a higher rate of glycogen utilization (P < 0.05). PGC-1, mRNA abundance increased in an intensity-dependent manner +3 h after exercise (LO, 3.8-fold; HI, 10.2-fold, P < 0.05). AMP-activated protein kinase (AMPK) (2.8-fold, P < 0.05) and calcium/calmodulin-dependent protein kinase II (CaMKII) phosphorylation (84%, P < 0.05) increased immediately after HI but not LO. p38 mitogen-activated protein kinase (MAPK) phosphorylation increased after both trials (,2.0-fold, P < 0.05), but phosphorylation of the downstream transcription factor, activating transcription factor-2 (ATF-2), increased only after HI (2.4-fold, P < 0.05). Cyclic-AMP response element binding protein (CREB) phosphorylation was elevated at +3 h after both trials (,80%, P < 0.05) and class IIa histone deacetylase (HDAC) phosphorylation increased only after HI (2.0-fold, P < 0.05). In conclusion, exercise intensity regulates PGC-1, mRNA abundance in human skeletal muscle in response to a single bout of exercise. This effect is mediated by differential activation of multiple signalling pathways, with ATF-2 and HDAC phosphorylation proposed as key intensity-dependent mediators. [source] Physical activity reduces prostate carcinogenesis in a transgenic modelTHE PROSTATE, Issue 13 2009Karyn A. Esser Abstract BACKGROUND Several epidemiological studies have reported an inverse association between physical activity and the risk of prostate cancer. To date, there are few animal studies looking at physical activity and cancer incidence, although the results are consistent with the epidemiological evidence. In general, as exercise intensity increased in the rats/mice, the likelihood that physical activity inhibited carcinogenesis increased. METHODS The present study used voluntary wheel running with C3(1)Tag mice that are predisposed to prostate cancer due to the directed expression of SV40 oncogenes. After 10 weeks, the prostates were collected from run and non-run mice and histopathology performed for the presence or absence of low grade or high grade PINS. RESULTS We found that for those mice that ran >5Km/group, 83% of the dorsolateral prostates were classified as within normal levels vs. 43% for the <5 km/day group (p,=,0.16). In addition, there was a relationship between average distance run and pathologic progression to high-grade PIN and local invasion, considered to be an early event in the formation of prostate adenocarcinoma. Forty three percent of dorsalateral prostates from mice that ran less than 5 km/day were classified with advanced pathology as compared to none (0) in mice that ran more than 5.0 km/day (p,=,0.05). CONCLUSIONS The results presented herein indicate that prostatic cancer progression is likely delayed or diminished by wheel running activity in a dose dependent manner in transgenic mice. These findings provide further evidence that exercise acts to decrease the progression of prostate cancer and they establish a transgenic animal model for future studies to define mechanism(s). Prostate 69: 1372,1377, 2009. © 2009 Wiley-Liss, Inc. [source] Protective effects of long term dietary restriction on swimming exercise-induced oxidative stress in the liver, heart and kidney of ratCELL BIOCHEMISTRY AND FUNCTION, Issue 2 2007Cenk Aydin Abstract In this study, we evaluated the hypothesis that long term dietary restriction would have beneficial effects on the oxidative stress and antioxidant enzyme systems in liver, heart and kidney in adult male rats undergoing different intensities of swimming exercise. Sixty male, Sprague,Dawley rats were assigned as either dietary restricted on every other week day (DR) or fed ad libitum (AL) groups, and each group was further subdivided into sedentary, endurance swimming exercise training (submaximal exercise) and exhaustive swimming exercise (maximal exercise) groups. Animals in the submaximal exercise group swam 5 days/week for 8 weeks, while maximal exercise was performed as an acute bout of exercise. In parallel with the increase in the intensity of the exercise, the degree of lipid peroxidation and protein oxidation were increased in both the DR and AL groups; however the rate of increase was lower in the DR group. Reduced glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) enzyme activities were lower in the DR group than in the AL group. In parallel with the increase in exercise intensity, GSH and GR enzyme activities decreased, whereas an increase was observed in GSH-Px enzyme activity. In conclusion, the comparison between the DR and AL groups with the three swimming exercise conditions shows that the DR group is greatly protected against different swimming exercise-induced oxidative stress compared with the AL group. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||