Long-term Endurance Training Research Articles

Heart adaptations to long-term aerobic training in paraplegic subjects: an echocardiographic study

Case-control. To execute an echocardiographic comparison between trained and untrained spinal cord injury (SCI) subjects, and to evaluate whether long-term heart adjustments to endurance training are comparable to those observed in able-bodied (ABL) subjects. Italy. We enrolled: (1) 17 male SCI patients (lesion level T1-L3, 34±8 years, body mass index (BMI) 23.0±2.8 kg m(-2)), 10 of whom were aerobically trained for >5 years (SCI(T)); (2) 18 age-, sex- and BMI-matched ABL subjects (35±6 years, BMI 23.6±2.8 kg m(-2)), 10 of whom were aerobically trained for >5 years (ABL(T)). Training frequency and volume were recorded by a dedicated questionnaire. All subjects underwent a trans-thoracic echocardiography; SCI subjects also performed an exhaustive incremental exercise test. Comparisons were made between ABL and SCI groups, between trained and untrained subjects within each group (analysis of variance). Effects of SCI-Compared with ABL subjects, SCI patients showed lower end-diastolic volume (76±21 vs. 113±23 ml, P<0.05) and ejection fraction (61±7% vs. 65±5%, P<0.05). Effects of training-Compared with untrained status, the intra-ventricular septum thickness (SCI, +18%; ABL, +4%), the posterior wall thickness (SCI, +17%; ABL, +2%) and the total normalized heart mass (SCI, +48%; ABL, +5%) were higher in both SCI(T) and in ABL(T). VO2peak was higher in the SCI(T) subgroup compared with the SCI(U) group. Heart seems to positively adapt to long-term endurance training in SCI patients. Regular exercise may therefore increase heart size, septum and posterior wall thickness, which likely contributes to improved VO2peak. These morphological and functional changes may reduce cardiovascular risk in SCI individuals.

Echocardiographic evaluation of aged male cross country skiers

The aim of this echocardiographic study was to evaluate the effects of long-term endurance training on cardiac structure and function in three different age groups of 48 healthy middle-aged and old former or still active male cross country skiers (23 in age group I: age 58.6 ± 2.2 years; 21 in age group II: age 74.9 ± 2.2 years; four in age group III: age 89.5 ± 1.9 years). The two oldest age groups were combined and compared with age group I. No significant differences in left atrial or ventricular dimensions between these two age groups were found. A high proportion of enlarged left atrial dimensions were found among all subjects with 80% exceeding the upper reference limit of 40 mm in diameter (LADs) and 94% exceeding the upper reference limit of 20 cm(2) in area (LAAs). Mean values for LADs (mm) and LAAs (cm(2) ) were: group I: 41.9 ± 4.7 and 24.7 ± 3.3; group II: 43.5 ± 4.8 and 25.2 ± 3.7; group III: 44.5 ± 4.7 and 25.8 ± 3.7. Left ventricular diastolic diameter exceeded the upper reference limits of >54 mm in 20 subjects among all. The groups had preserved systolic and age-related diastolic function.

Intramyocellular Lipid Content Following Normobaric Hypoxia Training in Sedentary Men

Recent studies demonstrated that long-term endurance training under normoxia condition increased intramyocellular lipid (IMCL) content in older adults (Pruchnic et al. 2004). However, the adaptation of the IMCL following hypoxia training has not been reported. PURPOSE: To investigate the effects of normobaric hypoxia training on IMCL content in sedentary men. METHODS: Twenty healthy men were divided into two groups; normobaric hypoxia training group (HYPO; n=9, 30 ± 2 yrs, BMI 25.7 ± 1.3 kg/m2) and normoxia training group (NOR; n=11, 32 ± 3 yrs, BMI 25.5 ± 1.0 kg/m2). Each exercise training (60 min) was conducted with a cycle ergometer at 55% of maximal oxygen uptake (VO2max) under different oxygen concentration in the room (15.0% for HYPO, 20.9% for NOR). The subjects performed 12 training sessions over 4 weeks (3 days/wk). Before and after the training period, the IMCL and extramyocellular lipid (EMCL) contents in the vastus lateralis were determined noninvasively by proton magnetic resonance spectroscopy (1H-MRS). RESULTS: Average workload throughout the 12 training sessions was significantly lower in the HYPO group (92 ± 4 W) than in the NOR group (111 ± 7 W, P < 0.05). Despite lower workload, the HYPO group revealed higher heart rate values during the exercises (139 ± 7 W) compared with the NOR group (131 ± 3 W, P = 0.06). After a 4wk of training period, both groups showed significant increases in VO2max (P < 0.05). The IMCL level increased after the training period in both groups (65 ± 33% in the HYPO group, 39 ± 25% in the NOR group), but it did not reach statistical difference. Contrary to the IMCL, the EMCL decreased in both groups, with a significant difference between pre- and post-training only in the NOR group (P < 0.05). CONCLUSIONS: These results indicate that the training adaptations following moderate endurance training were largely different between the IMCL and EMCL. The data also suggest that moderate normobaric hypoxia exposure during the exercise does not have strong impact on the magnitude of IMCL accumulation over the short-term training period.

Long-term Endurance Training Effects On Cd4+ Lymphocyte Activation In Young And Old Men

Regular exercise is thought to maintain or improve the adaptive immune (lymphocyte) response but there is little data on the long-term exercise effects on CD4+ activation in young and older individuals. PURPOSE: To investigate if 12 months of aerobic/endurance training would enhance CD4+ activation via increased CD25 receptor expression and density in trained older and young men compared to sedentary controls. METHODS: We compared young (30±5 yr) trained (TRY, n = 14) and sedentary (UTY, n = 12) men to older (69±5 yr) trained (TRO, n = 14) and sedentary (UTO, n = 10) men for 12 months. Older men cycled for three 50 min sessions per week (60-70% VO2peak) while the TRY group completed daily endurance training (90-120 min per day, 60-80% VO2peak). Venous blood was analysed every month for resting lymphocyte count and CD4+CD25+ expression and density by flow cytometry. Results were analysed by repeated measures two-way ANOVA (time vs group) with Bonferroni post hoc test (between-group and between-month), with p<0.05. RESULTS: The TRY group had a significantly higher concentration of CD4+ than the UTY for 4 months (37±7%); there was no difference in lymphocyte count between TRO and UTO. The TRO group had a significantly greater percentage of CD4+CD25+ than the UTO group (39±16%) for 8 months, and TRY (52±20%) and UTY (57±19%) groups for 6 months. The TRO, TRY and UTY groups showed a significantly different % of CD4+CD25+ compared to the previous month in April, May, October and November. CD25 density was significantly greater in the TRY compared to UTY group (34±11%) for 10 months, and in TRY compared to TRO (39±13%) and UTO (44±12%) groups for 10 months. CD25 density was significantly different to the previous month for TRY and UTY in April, May, July, August, September, October; for TRO and UTO, in February, September. CONCLUSION: Moderate intensity/duration endurance training increased the percentage of CD4+ expressing CD25+ in older men, possibly by increasing memory cells. Endurance training in young athletes increased CD4+CD25+ density rather than the number/percentage of lymphocytes positive for the receptor. Exercise may increase the CD4+ response through different mechanisms depending upon age. Furthermore, there are seasonal differences in CD4+CD25+ expression which may affect adaptive immunity.

Long-Term Respiratory Muscle Endurance Training in Patients with Myasthenia Gravis: First Results after Four Months of Training

Myasthenia gravis (MG) is characterized by reduced muscle endurance and is often accompanied by respiratory complications. Improvement of respiratory function is therefore an important objective in MG therapy. A previous study demonstrated that respiratory muscle endurance training (RMET) over four weeks increased respiratory muscle endurance of MG patients to about 200% of baseline. The purpose of the present study was to establish an appropriate maintenance training and to test its effects over four months. Ten patients with mild to moderate MG participated in this study. During the first month, they performed five training sessions per week. For the following 3 months, training frequency was reduced to five sessions per two weeks. Myasthenia score, lung function, and respiratory endurance were determined prior to training, after the first month, and after 4 months. Myasthenia score improved from 0.71 ± 0.1 to 0.56 ± 0.1 (P = 0.007). Respiratory endurance time increased from 6.1 ± 0.8 to 20.3 ± 3.0 min (P < 0.001). In conclusion, this RMET maintenance program is feasible and is significantly beneficial for MG patients.

Physical Exercise Prevents Cellular Senescence in Circulating Leukocytes and in the Vessel Wall

The underlying molecular mechanisms of the vasculoprotective effects of physical exercise are incompletely understood. Telomere erosion is a central component of aging, and telomere-associated proteins regulate cellular senescence and survival. This study examines the effects of exercising on vascular telomere biology and endothelial apoptosis in mice and the effects of long-term endurance training on telomere biology in humans. C57/Bl6 mice were randomized to voluntary running or no running wheel conditions for 3 weeks. Exercise upregulated telomerase activity in the thoracic aorta and in circulating mononuclear cells compared with sedentary controls, increased vascular expression of telomere repeat-binding factor 2 and Ku70, and reduced the expression of vascular apoptosis regulators such as cell-cycle-checkpoint kinase 2, p16, and p53. Mice preconditioned by voluntary running exhibited a marked reduction in lipopolysaccharide-induced aortic endothelial apoptosis. Transgenic mouse studies showed that endothelial nitric oxide synthase and telomerase reverse transcriptase synergize to confer endothelial stress resistance after physical activity. To test the significance of these data in humans, telomere biology in circulating leukocytes of young and middle-aged track and field athletes was analyzed. Peripheral blood leukocytes isolated from endurance athletes showed increased telomerase activity, expression of telomere-stabilizing proteins, and downregulation of cell-cycle inhibitors compared with untrained individuals. Long-term endurance training was associated with reduced leukocyte telomere erosion compared with untrained controls. Physical activity regulates telomere-stabilizing proteins in mice and in humans and thereby protects from stress-induced vascular apoptosis.

Interaction of myocardial insulin receptor and IGF receptor signaling in exercise-induced cardiac hypertrophy

Insulin-like growth factor-1 (IGF-1) signaling has recently been implicated in the development of cardiac hypertrophy after long-term endurance training, via mechanisms that may involve energetic stress. Given the potential overlap of insulin and IGF-1 signaling we sought to determine if both signaling pathways could contribute to exercise-induced cardiac hypertrophy following shorter-term exercise training. Studies were performed in mice with cardiac-specific IGF-1 receptor (IGF1R) knockout (CIGFRKO), mice with cardiac-specific insulin receptor (IR) knockout (CIRKO), CIGFRKO mice that lacked one IR allele in cardiomyocytes (IGFR−/−IR+/−), and CIRKO mice that lacked one IGF1R allele in cardiomyocytes (IGFR+/−IR−/−). Intravenous administration of IGF-1 or 75 hours of swimming over 4 weeks increased IGF1R tyrosine phosphorylation in the heart in control and CIRKO mice but not in CIGFRKO mice. Intriguingly, IR tyrosine phosphorylation in the heart was also increased following IGF-1 administration or exercise training in control and CIGFRKO mice but not in CIRKO mice. The extent of cardiac hypertrophy following exercise training in CIGFRKO and CIRKO mice was comparable to that in control mice. In contrast, exercise-induced cardiac hypertrophy was significantly attenuated in IGFR−/−IR+/− and IGFR+/−IR−/− mice. Thus, IGF-1 and exercise activates both IGF1R and IR in the heart, and IGF1R- and IR-mediated signals may serve redundant roles in the hypertrophic responses of the heart to exercise training.

Attenuated Postprandial Insulin Concentrations With Endurance Training Are Not Mediated By Reductions In Incretin Hormones

The incretin hormones, glucagon-like peptide-1 (GLP1) and glucose-dependent insulinotropic polypeptide (GIP), are released from the intestine after food ingestion and stimulate the pancreas to secrete insulin. Together, these hormones account for approximately half of the postprandial rise in plasma insulin concentrations. Although endurance exercise training improves insulin action on glucose disposal in skeletal muscle and results in a concomitant decrease in postprandial insulin secretion from the pancreas, it is not known if a reduction in incretin hormones contributes to the lower insulin response. PURPOSE: To determine if long-term endurance training is associated with lower plasma GLP1 and GIP responses to oral glucose ingestion. METHODS: Fifteen master endurance athletes (56 ± 2y) and 14 healthy non-exercising control subjects (57 ± 2y) underwent 2h, 75 g oral glucose tolerance tests (OGTTs) during which blood samples were acquired every 30 minutes to assess glucose, insulin, GLP1, and GIP concentrations by using commercially available assays. An index of insulin action (ISI) was calculated based on glucose and insulin concentration from the OGTT. VO2max was assessed using indirect calorimetry and body fat was quantified using DXA. RESULTS: Athletes had higher VO2max (54 ± 2 vs 34 ± 2 mL/kg/min; P < 0.0001) and lower body fat (14 ± 1 vs 23 ± 1%; P <0.0001) than controls. While the area under the curve (AUC) for glucose from the OGTT did not differ between groups (P = 0.12), athletes had 41% lower insulin AUC (P = 0.02) and two-fold greater ISI (0.001). Athletes and controls did not differ in terms of GLP1 AUC (346 ± 65 vs. 414 ± 80 pM·min, p= 0.52) or GIP AUC (19.4 ± 1.3 vs. 18.0 ± 1.4 ng/mL·min, P = 0.49). CONCLUSIONS: These findings suggest the lower postprandial insulin responses that occur in athletes are not modulated by reductions in postprandial concentrations of the intestinally derived incretin hormones, GLP1 and GIP. Supported by NIH General Clinical Research Center RR00036, NIH Clinical Nutrition Research Unit DK56341, Saint Louis University Beaumont Award, and the Longer Life Foundation.

Changes In The Frequency Of Senescent Blood T-cells During 6-months Training Preparation For An Ironman Triathlon

It is well-known that athletes are at an increased susceptibility to illness when adhering to arduous training regimens in preparation for endurance events. Senescent T-lymphocytes are antigen-experienced cells that accumulate with age and fail to clonally expand following further antigenic stimulation, thus predisposing the individual to a greater risk of infection. Although acute exercise is known to alter the frequency of senescent T-cells in blood, less is known about the effects of long-term endurance training. PURPOSE: To examine the effects of 6-months training preparation for an Ironman triathlon on the frequency of senescent blood T-cells. METHODS: Ten club-level triathletes (9 males; 1 female: Age: 42.9 ± 3.1 yrs) provided a fasted resting blood sample in the morning at 27 (DEC), 21 (JAN), 15 (MAR), 9 (MAY) and 3 (JUN) weeks before the 2008 Zurich Ironman Triathlon. An additional sample was collected 2-weeks post-competition (AUG). Total training hours completed by the participants over the 6-month period was 284.4 ± 122.9. Isolated blood lymphocytes were labelled with monoclonal antibodies to assess cell surface expression and co-expression of the T-cell senescence markers KLRG1, CD57 and CD28; and the naïve and memory T-cell markers CD45RA and CD45RO on CD3+, CD3+/CD4+ and CD3+/CD8+ T-cells using four-colour flow cytometry. Data was analyzed for time-change using a repeated measures linear mixed model. RESULTS: Compared to DEC, the percentage of CD4+ T-cells expressing KLRG1 increased by 71% (MAR), 20% (MAY) and 71% (AUG). CD4+ T-cells co-expressing KLRG1 and CD57 was 192% greater in AUG compared to DEC. No changes in senescent markers were found on CD8+ T-cells. The proportion of transitional T-cells (CD45RA+/CD45RO+) increased from MAY to JUN by 141% and 115% for CD4+ and CD8+ T-cells respectively. The proportion of memory CD8+ T-cells (CD45RA-/CD45RO+) was 40% (MAY) and 55% (AUG) greater than DEC. CONCLUSION: Adherence to a 6-month training program in preparation for an Ironman triathlon leads to an increased frequency of senescent CD4+ T-cells (KLRG1+/CD57+) and a greater proportion of naïve to memory transitional CD4+ and CD8+ T-cells in blood. These changes could have important implications for athlete infection risk during periods of arduous training.

Effect of Long-Term Endurance and Strength Training on Metabolic Control and Arterial Elasticity in Patients With Type 2 Diabetes Mellitus

Poor glucose control increases the risk of vascular complications and cardiovascular mortality in patients with diabetes mellitus (DM). Our aim was to evaluate the efficacy of a long-term exercise training program on metabolic control and arterial stiffness in patients with type 2 DM. Fifty men with DM (age 52.3 +/- 5.6 years) were randomly assigned to the exercise training (E) or standard treatment for DM (control [C]) group for 24 months. Supervised exercise training included both endurance and muscle strength training 4 times/week. All exercise sessions were controlled by heart rate and intensity. Glycated hemoglobin A1c, insulin, leptin, blood lipids, blood pressure, maximal oxygen consumption in spiroergometry, and muscle strength were measured every 6 months. Arterial stiffness was assessed by measuring pulse wave velocity. Maximal oxygen consumption in spiroergometry (E 31.9 to 34.8 vs C 32.6 to 31.8 ml/kg/min; p = 0.003), muscle strength (sit-up test, E 12.7 to 20.8 vs C 14.6 to 13.1 times; p <0.001), hemoglobin A1c (E 8.2% to 7.6% vs C 8.0% to 8.3%; p = 0.006), and leptin (E 7.4 to 6.7 vs C 7.4 to 7.9 microg/L; p = 0.013) improved significantly in the E group, but no change or worsening in these variables occurred in the C group. Body weight was not different between groups at 2 years. However, pulse wave velocity increased in both groups (E +0.600 vs C +1.300 m/s; p = 0.27). In conclusion, long-term endurance and strength training was effective and resulted in improved metabolic control of DM compared with standard treatment. Despite significant cardiovascular risk reduction, conduit arterial elasticity did not improve.

Metabolomic investigation into variation of endogenous metabolites in professional athletes subject to strength-endurance training

Strength-endurance type of sport can lead to modification of human beings' physiological status. The present study aimed to investigate the alteration of metabolic phenotype or biochemical compositions in professional athletes induced by long-term training by means of a novel systematic tool, metabolomics. Resting venous blood samples of junior and senior male rowers were obtained before and after 1-wk and 2-wk training. Venous blood from healthy male volunteers as control was also sampled at rest. Endogenous metabolites in serum were profiled by GC/TOF-MS and multivariate statistical technique, i.e., principal component analysis (PCA), and partial least squares projection to latent structures and discriminant analysis (PLS-DA) were used to process the data. Significant metabolomic difference was observed between the professional athletes and control subjects. Long-term strength and endurance training induced distinct separation between athletes of different exercise seniority, and training stage-related trajectory of the two groups of athletes was clearly shown along with training time. However, most of these variations were not observed by common biochemical parameters, such as hemoglobin, testosterone, and creatine kinase. The identified metabolites contributing to the classification included alanine, lactate, beta-d-methylglucopyranoside, pyroglutamic acid, cysteine, glutamic acid, citric acid, free fatty acids, valine, glutamine, phenylalanine, tyrosine, and so on, which were involved in glucose metabolism, oxidative stress, energy metabolism, lipid metabolism, amino acid metabolism. These findings suggest that metabolomics is a promising and potential tool to profile serum of professional athletes, make a deep insight into physiological states, and clarify the disorders induced by strength-endurance physical exercise.

Is the second week post-race an adequate period to assess the effect of a long-term conditioning on digestive physiology in competing endurance horses?

In human athletes, the physiological effects of physical activity on digestion could differ depending on whether it is a bout of exercise or a long-term conditioning. When the aim is to investigate the effect of long-term endurance training on the digestive physiology in competing horses, animals need to be at complete rest during the digestibility and mean retention time (MRT) measurements. We hypothesized that the resting period allowed to horses post-race, and particularly the second week following an endurance race, could be an adequate period to assess digestive physiology and that measurements would still be representative of the pre-competition status. Nutrient total tract apparent digestibility, total MRT and faecal microbial composition and activity measured before a 90km endurance race were compared with the data obtained post-race, during the second week of the resting period. No differences in the digestibility coefficients, MRT, faecal pH, lactate concentrations and bacterial counts were observed before and after the endurance race. The propionate proportion was higher and the (C2 þ C4):C3 ratio was lower during the second week post-race than before the race. Carrying out measurements during the second week post-race provides data close to the prerace status, and avoids an a disturbed training schedule and unnecessary stress before the race in competing endurance horses.

Gene expression profiling of skeletal muscle in exercise-trained and sedentary rats with inborn high and low VO2max

The relationship between inborn maximal oxygen uptake (VO(2max)) and skeletal muscle gene expression is unknown. Since low VO(2max) is a strong predictor of cardiovascular mortality, genes related to low VO(2max) might also be involved in cardiovascular disease. To establish the relationship between inborn VO(2max) and gene expression, we performed microarray analysis of the soleus muscle of rats artificially selected for high- and low running capacity (HCR and LCR, respectively). In LCR, a low VO(2max) was accompanied by aggregation of cardiovascular risk factors similar to the metabolic syndrome. Although sedentary HCR were able to maintain a 120% higher running speed at VO(2max) than sedentary LCR, only three transcripts were differentially expressed (FDR <or=0.05) between the groups. Sedentary LCR expressed high levels of a transcript with strong homology to human leucyl-transfer RNA synthetase, of whose overexpression has been associated with a mutation linked to mitochondrial dysfunction. Moreover, we studied exercise-induced alterations in soleus gene expression, since accumulating evidence indicates that long-term endurance training has beneficial effects on the metabolic syndrome. In terms of gene expression, the response to exercise training was more pronounced in HCR than LCR. HCR upregulated several genes associated with lipid metabolism and fatty acid elongation, whereas LCR upregulated only one transcript after exercise training. The results indicate only minor differences in soleus muscle gene expression between sedentary HCR and LCR. However, the inborn level of fitness seems to influence the transcriptional adaption to exercise, as more genes were upregulated after exercise training in HCR than LCR.

Asthma and the elite athlete: Summary of the International Olympic Committee's Consensus Conference, Lausanne, Switzerland, January 22-24, 2008

Respiratory symptoms cannot be relied on to make a diagnosis of asthma and/or airways hyperresponsiveness (AHR) in elite athletes. For this reason, the diagnosis should be confirmed with bronchial provocation tests. Asthma management in elite athletes should follow established treatment guidelines (eg, Global Initiative for Asthma) and should include education, an individually tailored treatment plan, minimization of aggravating environmental factors, and appropriate drug therapy that must meet the requirements of the World Anti-Doping Agency. Asthma control can usually be achieved with inhaled corticosteroids and inhaled beta(2)-agonists to minimize exercise-induced bronchoconstriction and to treat intermittent symptoms. The rapid development of tachyphylaxis to beta(2)-agonists after regular daily use poses a dilemma for athletes. Long-term intense endurance training, particularly in unfavorable environmental conditions, appears to be associated with an increased risk of developing asthma and AHR in elite athletes. Globally, the prevalence of asthma, exercise-induced bronchoconstriction, and AHR in Olympic athletes reflects the known prevalence of asthma symptoms in each country. The policy of requiring Olympic athletes to demonstrate the presence of asthma, exercise-induced bronchoconstriction, or AHR to be approved to inhale beta(2)-agonists will continue.

Differential effects of endurance and resistance training on central fatigue

The effect of long-term endurance and resistance training on central fatigue has been studied using transcranial magnetic stimulation by exercising the biceps brachii to exhaustion and recording motor-evoked potentials from the non-exercised homologous biceps. Three groups of eight healthy individuals took part: two groups of individuals who had more than 8 years of athletic training in either an endurance or resistance sport, and a group of controls. The size of a motor-evoked potential (area of averaged rectified response) was significantly depressed in all three groups in the non-exercised arm after exhaustive exercise of the opposite arm. Recovery of motor-evoked potentials occurred earlier in endurance athletes (20 min) than in control participants (30 min) and resistance athletes (>30 min). Dexterity and maximum voluntary contraction of the biceps for the non-exercised arm were not depressed in any group. In a separate session, the limit of endurance time for the biceps was reduced significantly following exhaustive exercise of the biceps of the other arm for resistance athletes and control participants, whereas there was no change in the endurance athletes. Our findings suggest that athletic training has an effect on the mechanism of central fatigue that may be specific to the nature of training.

Effect of aerobic training on99mTc-methoxy isobutyl isonitrile (99mTc-sestamibi) uptake by myocardium and skeletal muscle: implication for noninvasive assessment of muscle metabolic profile

The effect of long-term endurance training on skeletal muscle and myocardial uptake of (99m)Tc-sestamibi, a radiopharmaceutical accumulating in the mitochondria, was investigated. Twenty-six Wistar rats were divided into a trained (5 days week(-1) endurance running for 14 weeks) and an untrained group. On completion of training, (99m)Tc-sestamibi was administered and, 2 h post-injection, the myocardium and the soleus, extensor digitorum longus (EDL) and medial gastrocnemius (MG) muscles were removed for the measurement of cytochrome c oxidase (CCO) activity and (99m)Tc-sestamibi uptake. Tissue (99m)Tc-sestamibi kinetics was preliminarily studied in 16 other rats for up to 2 h post-injection. Two hours post-injection (99m)Tc-sestamibi uptake was either stable (myocardium) or still rising (skeletal muscles). Both CCO activity and (99m)Tc-sestamibi uptake decreased in the same order (myocardium, soleus, EDL, MG) in the tissues examined. The CCO activity of the EDL and MG muscles was higher (P < 0.05) in the trained compared to the untrained group. (99m)Tc-sestamibi uptake in the soleus and EDL muscles was higher (P < 0.05) in the trained compared to the untrained rats, whereas the difference in MG was marginally significant (P = 0.06) in favour of the trained group. Long-term endurance training, resulting in elevated skeletal muscle CCO activity, is also associated with a similar increase in (99m)Tc-sestamibi uptake. This finding suggests that (99m)Tc-sestamibi could be used in imaging assessment of skeletal muscle metabolism with possible applications in both clinical and sports medicine settings.

The Impact of Pre-Dialytic Endurance Training on Nutritional Status and Quality of Life in Stable Hemodialysis Patients (Sawada Study)

Background. Protein-energy malnutrition and decreased quality of life (QOL) are common in hemodialysis (HD) patients. Although several studies have proved that regular exercise has beneficial effects, few control studies have shown the effects of exercise training on the nutritional status and QOL in HD patients. Methods. Fifty-five HD patients were recruited, and 22 of them were trained to exercise on an ergometer prior to dialysis three times a week for one year. Serum albumin levels, creatinine generation rate (CGR), and the Short Form 36 were assessed as outcome measures. Results. The serum albumin levels and CGR increased in the training group compared with baseline. The QOL scores also increased in half of the physical health and mental health dimensions in the training group. Conclusion. These observations suggest that low-dose, long-term pre-dialytic endurance training might reverse the poor clinical outcome by improving the nutritional status and QOL in HD patients.

The effects of long-term endurance training on the immune and endocrine systems of elderly men: the role of cytokines and anabolic hormones

Backgrounda decline in immune and endocrine function occurs with aging. The main purpose of this study was to investigate the impact of long-term endurance training on the immune and endocrine system of elderly men. The possible interaction between these systems was also analysed.Resultselderly runners showed a significantly higher T cell proliferative response and IL-2 production than sedentary elderly controls. IL-2 production was similar to that in young adults. Their serum IL-6 levels were significantly lower than their sedentary peers. They also showed significantly lower IL-3 production in comparison to sedentary elderly subjects but similar to the youngs. Anabolic hormone levels did not differ between elderly groups and no clear correlation was found between hormones and cytokine levels.Conclusionhighly conditioned elderly men seem to have relatively better preserved immune system than the sedentary elderly men. Long-term endurance training has the potential to decelerate the age-related decline in immune function but not the deterioration in endocrine function.

Beat‐to‐beat modulation of atrioventricular conduction during dynamic exercise in the elite athletes

PR interval shortens due to an extrinsic neural mechanism during exercise as well as PP interval. On the contrary, PR interval lengthens due to an intrinsic mechanism of the atrioventricular (AV) node, when PP interval is decreased by atrial pacing. Long-term endurance training lowers baseline heart rate (HR) and augments its variability. However, it remains unknown how endurance training modifies the extrinsic and intrinsic mechanisms controlling AV conduction. To answer this question, we compared the responses in PP, RR, and PR intervals during dynamic exercise between sedentary subjects and elite athletes, who performed ergometer exercise to increase HR to 160 beats/min from baseline. Although the mean PP and RR intervals similarly decreased during exercise, the variation of RR interval became much smaller than that of PP interval. In contrast, the PR interval variation tended to increase during exercise, despite shortened mean PR interval. A strong inverse relationship between PP interval and the subsequent change in PR interval was recognized during exercise, indicating that PR interval changed due to the intrinsic AV nodal mechanism as opposed to fluctuation in PP interval. Although the fundamental characteristics of the exercise-induced response in PR interval were the same between both groups, the intrinsic AV nodal mechanism in the athletes started to operate at a longer PP interval. The intrinsic mechanism of AV node is likely to cancel fluctuation in atrial excitation rhythm during exercise so as to stabilize ventricular excitation rhythm. We suggest that long-term endurance training allows the intrinsic AV nodal function to operate at a lower HR.

Endurance Exercise Training and L-Carnitine Supplementation Stimulates Gene Expression in the Blood and Muscle Cells in Young Athletes and Middle Aged Subjects

Endurance exercise training is known to increase fatty acid (FA) oxidation during exercise and to stimulate mRNA synthesis of mitochondrial carnitine acyltransferases in skeletal muscle. To test the hypothesis that long-term endurance training induces cellular adaptions in different tissues, we determined the relative mRNA abundances of these genes in skeletal muscle and in blood cells from young athletes and middle aged untrained persons. The first trial examined 6 cross-country skiers, at the start of high volume/low intensity exercise training and 6 months later, when training at the same exercise intensity had elicited a significantly slower rate of lactate accumulation. In the second trial of 24 middle aged untrained (12 placebo and 12 carnitine supplemented) probands the mRNA expression was determined at the beginning and after three months of a low intensity endurance training program.