Canadian journal of applied physiology = Revue canadienne de physiologie appliquee最新文献

{"title":"Effects of eccentric exercise on cycling efficiency.","authors":"Joaquin Sanchis Moysi,&nbsp;Jerónimo Carmelo Garcia-Romero,&nbsp;José Ramón Alvero-Cruz,&nbsp;Germán Vicente-Rodriguez,&nbsp;Ignacio Ara,&nbsp;Cecelia Dorado,&nbsp;José A L Calbet","doi":"10.1139/h05-119","DOIUrl":"https://doi.org/10.1139/h05-119","url":null,"abstract":"<p><p>The aim of this study was to find out whether the efficiency of concentric muscle contraction is impaired by eccentric squatting exercise. The study involved 25 male physical education students in two experiments. In the first experiment 14 subjects undertook cycling exercise at 65% VO(2)max until exhaustion on two occasions. During the experimental condition their cycling was interrupted every 10 min so they could perform eccentric squatting exercise, whereas in the control condition they rested seated on the bike during the interruptions. Eccentric squatting consisted of 10 series of 25 reps with a load equivalent to 150% of the subject's body mass on the shoulders. During the first experiment gross efficiency decreased (mean +/- SE) from 17.1 +/- 0.3 to 16.0 +/- 0.4%, and from 17.2 +/- 0.3 to 16.5 +/- 0.4%, between the 2nd and 9th cycling bouts of the experimental and control conditions, respectively (both p < 0.05). The reduction in cycling efficiency was similar in both conditions (p = 0.10). Blood lactate concentration [La] was higher during the experimental than in the control condition (p < 0.05), but substrate oxidation was similar. MVC was decreased similarly (25-28%) in both conditions. The 11 subjects participating in the second experiment undertook 25 reps of eccentric squatting exercise only, each with a load equivalent to 95% of his maximal voluntary contraction (MVC), repeated every 3 min until exhaustion. One hour after the end of the eccentric squatting exercise series cycling, VO(2) and gross cycling efficiency were comparable to the values observed before the eccentric exercise. Both experimental protocols with eccentric exercise elicited similar muscle soreness 2 days later; however, at this time cycling efficiency was similar to that observed prior to eccentric exercise. The interposition of cycling exercise between the eccentric exercise bouts accelerated the recovery of MVC. We conclude that eccentric exercise does not alter or has only a marginal effect on gross cycling efficiency even in presence of marked muscle soreness.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 3","pages":"259-75"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-119","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24982585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regulatory impact of intra-hepatic carbohydrate and lipid metabolism.","authors":"Jean-Marc Lavoie,&nbsp;Raynald Bergeron,&nbsp;Martin G Latour","doi":"10.1139/h05-121","DOIUrl":"https://doi.org/10.1139/h05-121","url":null,"abstract":"<p><p>The first evidence that the liver can afferently contribute to regulatory activities comes from studies on regulation of food intake. The hepatic afferent pathway has been shown to be responsive to glucoprivic as well as lipoprivic stimuli. Similarly to regulation of food intake, it has been reported that the liver may afferently contribute to the metabolic regulation of exercise. The best reported evidence of this view is the observation that the decrease in insulin and the increase in glucagon and noradrenaline levels during exercise are diminished in hepatic vagotomized rats (Lavoie et al., 1989). The concept behind these observations is that the liver, through the existence of hepatic glucoreceptors, is responsive to a decrease in glycogen content or to some metabolites of the glycolytic chain related to liver glycogen content. There is also some evidence that lipids in the liver may have some regulatory impact inside and outside the liver. Recent interest in looking at lipid metabolism in liver has been spurred by the observation that the increased flux of lipids through the hepatic portal vein has been associated with increased risks of metabolic and cardiovascular abnormalities. To explore this avenue, a 10% triglyceride emulsion was infused into either the portal or a peripheral vein of rats for 48 hrs while another group of rats was acutely infused for 2 hrs into the portal vein. The results indicate that all of these lipid infusions resulted in an increase in liver lipid infiltration, which may be associated with the development of a state of hepatic and peripheral insulin resistance.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 3","pages":"282-91"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-121","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24982587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insulin sensitivity in skeletal muscle regulated by a hepatic hormone, HISS.","authors":"W Wayne Lautt","doi":"10.1139/h05-123","DOIUrl":"https://doi.org/10.1139/h05-123","url":null,"abstract":"<p><p>The current state of the HISS (hepatic insulin sensitizing substance) hypothesis is briefly outlined. In the postmeal absorptive state, 50-60% of the glucose storage action of insulin is accounted for by the actions of HISS released from the liver and acting on skeletal muscle. Hepatic parasympathetic nerves permissively regulate the ability of a pulse of insulin to release HISS, thereby potentiating the impact of insulin in the fed state. HISS release in response to insulin decreases progressively with fasting to create a physiological state of HISS-dependent insulin resistance. HISS release is regulated by parasympathetic nerves via muscarinic receptors and nitric oxide, and insulin resistance of skeletal muscle produced by hepatic denervation is reversed by intraportal but not intravenous acetylcholine or a nitric oxide donor. It is suggested that HISS-dependent insulin resistance occurs in animal models including sucrose-fed rats, spontaneously hypertensive rats, chronic liver disease, fetal alcohol effect in the adult offspring, and type 2 diabetes.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 3","pages":"304-12"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-123","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24982589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mobilization of glucose from the liver during exercise and replenishment afterward.","authors":"R Richard Pencek,&nbsp;Patrick T Fueger,&nbsp;Raul C Camacho,&nbsp;David H Wasserman","doi":"10.1139/h05-122","DOIUrl":"https://doi.org/10.1139/h05-122","url":null,"abstract":"<p><p>The liver is anatomically well situated to regulate blood glucose. It is positioned downstream from the pancreas, which releases the key regulatory hormones glucagon and insulin. It is also just downstream from the gut, permitting efficient extraction of ingested glucose and preventing large excursions in systemic glucose after a glucose-rich meal. The position of the liver is not as well situated from the standpoint of experimentation and clinical assessment, as its primary blood supply is impossible to access in conscious human subjects. Over the last 20 years, to study hepatic glucose metabolism during and after exercise, we have utilized a conscious dog model which permits sampling of the blood that perfuses (portal vein, artery) and drains (hepatic vein) the liver. Our work has demonstrated the key role of exercise-induced changes in glucagon and insulin in stimulating hepatic glycogenolysis and gluconeogenesis during exercise. Recently we showed that portal venous infusion of the pharmacological agent 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside leads to a marked increase in hepatic glucose production. Based on this, we propose that the concentration of AMP may be a component of a physiological pathway for stimulating hepatic glucose production during exercise. Insulin-stimulated hepatic glucose uptake is increased following exercise by an undefined mechanism that is independent of liver glycogen content. The fate of glucose taken up by the liver is critically dependent on hepatic glycogen stores, however, as glycogen deposition is greatly facilitated by prior glycogen depletion.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 3","pages":"292-303"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-122","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24982588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Glucagon receptors: effect of exercise and fasting.","authors":"Carole Lavoie","doi":"10.1139/h05-124","DOIUrl":"https://doi.org/10.1139/h05-124","url":null,"abstract":"<p><p>One paradox of hormonal regulation during exercise is the maintenance of glucose homeostasis after endurance training despite a lower increase in plasma glucagon. One explanation could be that liver sensitivity to glucagon is increased by endurance training. Glucagon exerts its effect through a 62 KDa glycoprotein receptor, member of the G protein-coupled receptor. To determine whether changes with exercise in glucagon sensitivity occurred at the level of the glucagon receptor (GR), binding characteristics of hepatic glucagon receptors were ascertained in rat purified plasma membranes. Saturation kinetics indicated no difference in the dissociation constant or affinity of glucagon receptor, but a significantly higher glucagon receptor binding density in liver in endurance trained compared to untrained animals. Along with endurance training, it appears that fasting also changes GR binding characteristics. In animals fasting 24 hrs, a significant increase in glucagon receptor density was also reported. Although the exact mechanism remains unknown, there is no doubt that the liver can adapt to physiological stress through modulation of GR binding characteristics to enhance the hepatic glucose production responsiveness to glucagon.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 3","pages":"313-27"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-124","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24982590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aging, resistance training, and motor unit discharge behavior.","authors":"Gary Kamen","doi":"10.1139/h05-126","DOIUrl":"https://doi.org/10.1139/h05-126","url":null,"abstract":"<p><p>Researchers have alluded the existence of \"neural factors\" in the expression and development of muscular strength. Candidate neural factors including motor unit recruitment, rate coding, double firing, and motor unit synchronization are discussed in this review. Aging is generally accompanied by lower motor unit discharge rates. However, both young and older adults exhibit rapid changes in muscular strength with repeated strength testing. These strength changes occur with concomitant albeit transient increase in motor unit discharge rate. These and other neural factors may contribute to the initial increase in muscular strength observed during the early phases of resistance exercise training.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 3","pages":"341-51"},"PeriodicalIF":0.0,"publicationDate":"2005-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-126","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24982592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Achievement of peak VO2 during a 90-s maximal intensity cycle sprint in adolescents.","authors":"Craig A Williams,&nbsp;Sébastien Ratel,&nbsp;Neil Armstrong","doi":"10.1139/h05-112","DOIUrl":"https://doi.org/10.1139/h05-112","url":null,"abstract":"<p><p>The aim of this study was to determine whether peak oxygen uptake (PVO2) attained in a 90-s maximal intensity cycle sprint is comparable to that from a conventional ramp test. Sixteen participants (13 boys and 3 girls, 14.6 +/- 0.4 yr) volunteered for the study. On Day 1 they completed a PVO2 test to exhaustion using a 25 W x min(-1) ramp protocol beginning at 50 W. Peak VO2 was defined as the highest VO2 value achieved, and aerobic power (Wmax) as the power output of the final 30 s. On Day 2 the participants completed two 90-s maximal sprints (S1 and S2). A 45-min recovery period separated each sprint. Mean oxygen uptake over the last 10 s of each sprint was determined as PVO2, and minimum power (MinP-30 s) as the mechanical power attained in the final 30 s. A one-way ANOVA was used to analyse differences between S1, S2, and the ramp test for PVO2 and MinP-30 s. Peak VO2 was not significantly different between the ramp, S1, or S2 (2.64 +/- 0.5, 2.49 +/- 0.5, and 2.53 +/- 0.5 L x min(-1), respectively, p > 0.68). The S1 and S2 PVO2 scores represented 91 +/- 10% and 92 +/- 10% of the ramp aerobic test. The MinP-30 s for S1 and S2 were significantly lower than the Wmax of the ramp test, p < 0.05. Hence, for researchers solely interested in PVO2 values, a shorter but more intensive protocol provides an alternative method to the traditional ramp aerobic test.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 2","pages":"157-71"},"PeriodicalIF":0.0,"publicationDate":"2005-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-112","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25157465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Protective effects of moderate exercise with dietary vitamin C and E on blood antioxidative defense mechanism in rats with streptozotocin-induced diabetes.","authors":"Mustafa Naziroğlu,&nbsp;Peter J Butterworth","doi":"10.1139/h05-113","DOIUrl":"https://doi.org/10.1139/h05-113","url":null,"abstract":"<p><p>Daily moderate exercise and supplementation of vitamins C and E (VCE) can be beneficial in diabetes by ameliorating the effects of free radical production. The present study sought to analyze the effect of moderate exercise accompanying VCE supplementation on lipid peroxidation (LP) and antioxidative systems in the blood of streptozotocin-induced diabetic rats. Forty female Wistar rats were randomly divided 4 groups. The 1st and 2nd groups served as the control and diabetic groups, respectively. The 3rd group was the diabetic-exercise group. The 4th group, also diabetic-exercise rats, received VCE-supplemented feed. Animals in the exercised groups were moderately exercised on a treadmill 5 days a week for 3 weeks. Diabetes was induced on Day 0 of the exercise. Plasma and red blood cell (RBC) samples were taken from all animals on Day 20. Glutathione peroxidase, catalase, and reduced glutathione levels in plasma and RBCs, and vitamins A, E, and beta-carotene in plasma were lower in diabetic rats than in control animals, whereas there was a significant increase in platelet counts in both plasma and RBC LP levels. The decreased antioxidant enzymes and vitamins, and the increased LP levels and WBC counts, did improve through exercise only, although their levels were mostly increased by exercise + VCE supplementation. There were no significant changes in the hemoglobin and hematocrit values in the 4 groups. In conclusion, these data demonstrate an increase in LP in the blood of diabetic animals whereas there was a decrease in the antioxidant vitamins and enzymes. However, dietary VCE with moderate exercise may strengthen the antioxidant defense system by decreasing reactive oxygen species.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 2","pages":"172-85"},"PeriodicalIF":0.0,"publicationDate":"2005-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-113","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25157466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Immune alterations, lipid peroxidation, and muscle damage following a hill race.","authors":"Richard J Simpson,&nbsp;Martin R Wilson,&nbsp;James R Black,&nbsp;James A Ross,&nbsp;Greg P Whyte,&nbsp;Keith Guy,&nbsp;Geraint D Florida-James","doi":"10.1139/h05-115","DOIUrl":"https://doi.org/10.1139/h05-115","url":null,"abstract":"<p><p>Hill races usually include large downhill running sections, which can induce significant degrees of muscle damage in a field setting. This study examined the link between muscle damage, oxidative stress, and immune perturbations following a 7-km mountainous hill race with 457 m of ascent and 457 m of descent. Venous blood samples were taken from 7 club level runners before, immediately after, and 48 hrs postrace. Samples were analysed for total and differential leukocyte counts, markers of muscle damage (CK), lipid peroxidation (MDA), and acute phase proteins (CRP; fibrinogen; alpha-1-ACT). The total antioxidant status (TEAC) and plasma levels of the proinflammatory cytokines IL-6, IL-8, and TNF-alpha were also determined. Subjective pain reports, and plasma activities of CK, MDA, and circulatory monocytes reached peak values at 48 hrs postrace (p < 0.05). TEAC and the cytokine IL-8 increased immediately after the race (p < 0.05). Plasma TNF-alpha remained unchanged (p > 0.05). Despite the reports of muscle damage and soreness, no evidence of an acute phase response was observed (p > 0.05), which may be explained by the failure of the race to induce a plasma TNF-alpha response. Future studies should examine the link between muscle damage, oxidative stress, and the acute phase response following hill races of longer duration with larger eccentric components.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 2","pages":"196-211"},"PeriodicalIF":0.0,"publicationDate":"2005-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-115","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25158501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physical fitness and the metabolic syndrome in adults from the Quebec Family Study.","authors":"Normand G Boulé,&nbsp;Claude Bouchard,&nbsp;Angelo Tremblay","doi":"10.1139/h05-111","DOIUrl":"https://doi.org/10.1139/h05-111","url":null,"abstract":"<p><p>Physically fit individuals have a lower risk of cardiovascular disease and type 2 diabetes. However, it is unknown whether the associations between physical fitness and the metabolic syndrome are independent of total and abdominal adiposity. Physical fitness was defined as the physical work capacity on a cycle ergometer at heart rate of 150 bpm (PWC 150) in a sample of 158 men and 198 women 20-60 years of age. PWC 150 was adjusted for fat-free mass prior to the analyses. Percent body fat was estimated by hydrostatic weighing. Visceral and subcutaneous abdominal fat were measured by computed tomography. The prevalence of the metabolic syndrome was based on two definitions. The metabolic syndrome decreased with increasing fitness in men (approx. 6 times higher in less fit vs. most fit tertile, p < 0.05) and in women (approx. 4 times higher in less fit vs. most fit tertile, p < 0.05). Fitness was negatively associated with most individual components of the metabolic syndrome, except HDL-cholesterol for which the correlation was positive. However, in men and in women, the effects of physical fitness on the individual components of the metabolic syndrome were attenuated after considering total and abdominal adiposity.</p>","PeriodicalId":79394,"journal":{"name":"Canadian journal of applied physiology = Revue canadienne de physiologie appliquee","volume":"30 2","pages":"140-56"},"PeriodicalIF":0.0,"publicationDate":"2005-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1139/h05-111","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25157464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}