Long-term Endurance Exercise Research Articles

Respiratory muscle training in healthy individuals: physiological rationale and implications for exercise performance.

The respiratory system has traditionally been viewed to be capable of meeting the substantial demands for ventilation and gas exchange and the cardiopulmonary interactions imposed by short-term maximum exercise or long-term endurance exercise. Recent studies suggest that specific respiratory muscle (RM) training can improve the endurance and strength of the respiratory muscles in healthy humans. The effects of RM training on exercise performance remains controversial. When whole-body exercise performance is evaluated using submaximal fixed work-rate tests, significant improvements are seen and smaller, but significant improvements have also been reported in placebo-trained individuals. When performance is measured using time-trial type performance measures versus fixed workload tests, performance is increased to a much lesser extent with RM training. It appears that RM training influences relevant measures of physical performance to a limited extent at most. Interpretation of the collective literature is difficult because most studies have utilised relatively small sample sizes and very few studies have used appropriate control or placebo groups. Mechanisms to explain the purported improvements in exercise performance remain largely unknown. However, possible candidates include improved ratings of breathing perception, delay of respiratory muscle fatigue, ventilatory efficiency, or blood-flow competition between respiratory and locomotor muscles. This review summarises the current literature on the physiology of RM training in healthy individuals and critically evaluates the possible implications for exercise performance.

Predictors of adipose tissue lipoprotein lipase in middle-aged and older men: Relationship to leptin and obesity, but not cardiovascular fitness

The effects of long-term endurance exercise training, body composition, and cardiovascular fitness (VO2max) on the activity of adipose tissue lipoprotein lipase (AT-LPL) and lipoprotein lipids were examined in 66 healthy age-matched middle-aged and older men (mean +/- SE, 61 +/- 1 years). We compared subcutaneous abdominal (ABD) and gluteal (GLT) heparin-elutable AT-LPL activity in 19 master athletes (VO2max > 40 mL/kg/min) and 20 lean sedentary men (VO2max < 40 mL/kg/min) versus 27 obese sedentary men (VO2max < 40 mL/kg/min; body fat > 27%). Fasting insulin and leptin levels were similar in master athletes and lean sedentary men, but were lower than in obese sedentary men. There were no differences in fasting values for total cholesterol or low-density lipoprotein cholesterol (LDL-C) among the groups, but master athletes had lower triglyceride (TG) values (P < .05) and higher high-density lipoprotein cholesterol (HDL-C) and HDL2-C (P < .05) than obese and lean sedentary men. There were no regional (ABD v GLT) differences in the activity of AT-LPL in these groups, but obese sedentary men had higher levels of ABD AT-LPL (2.1 +/- 0.3 nmol/10(6) cells x min) than lean sedentary men (0.8 +/- 0.2) and master athletes (0.5 +/- 0.1, P = .01). Similar results were observed for GLT AT-LPL. Both ABD and GLT AT-LPL activity correlated positively with percent body fat (r = .46 to .54, P < .001), fasting insulin (r = .37 to .45, P < .001), and leptin (r = .61 to .65, P < .0001), but not with VO2max. In stepwise multiple regression analysis, leptin was the main independent predictor of ABD (R2 = .43, P < .0001) and GLT (R2 = .40, P < .0001) AT-LPL activity. Plasma TG correlated positively (r = .32, P < .01) and HDL-C correlated negatively (r = -.32, P = .02) with ABD AT-LPL activity, but these relationships were not significant after controlling for percent body fat or leptin. The results of this study indicate that in healthy middle-aged and older men, the major determinants of AT-LPL activity are obesity and its major associated hormones, leptin and insulin, not cardiovascular fitness, and also suggest that the higher HDL-C levels observed in endurance-trained men are not associated with increased AT-LPL activity.

Short-term exercise training alters responses of porcine femoral and brachial arteries

The primary purpose of this study was to test the hypothesis that short-term exercise training enhances endothelium-dependent relaxation of porcine femoral and brachial arteries. Miniature swine ran on a treadmill for 1 h at 3.5 miles/h, twice daily, for 7 consecutive days (Trn; n = 8). Compared with sedentary controls (Sed; n = 7), Trn swine exhibited increased skeletal muscle citrate synthase activity (P < 0.05). Vascular rings approximately 3 mm in axial length were prepared from segments of femoral and brachial arteries, and responses to vasoactive agents were determined in vitro. Sensitivity to bradykinin (BK) was enhanced in brachial vascular rings from Trn swine compared with those from Sed swine, as indicated by lower concentration of vasorelaxing agent eliciting 50% of maximal response values [Sed, 8.63 +/- 0.09 (-log M); Trn, 9.07 +/- 0.13; P < 0.05]. This difference between groups was preserved in brachial rings in which formation of nitric oxide and vasodilator prostaglandins were inhibited [Sed, 8.57 +/- 0.17 (-log M); Trn, 8.97 +/- 0.13; P < 0.05]. Sensitivity to BK was not different between Sed and Trn in femoral arterial rings. Relaxation responses to the calcium ionophore A-23187 and sodium nitroprusside were not altered with training. Femoral and brachial arterial rings from Trn swine, compared with those from Sed swine, exhibited augmented vasocontraction across a range of concentrations and increased sensitivity to norepinephrine (all P < 0.05). These findings indicate that responses of porcine femoral and brachial arteries change in response to short-term training. Together with findings from previous studies involving longer term training, our data suggest that vascular adaptations may differ at different time points during long-term endurance exercise training.

Hyperfibrinogenemia and cardiovascular risk: possible strategies for intervention

Elevated plasma fibrinogen has been identified as an independent predictor of cardiovascular diseases. Although abundant evidence suggests a causal role of fibrinogen in the pathogenesis of atherothrombotic complications, this has not yet been proven. To overcome this dilemma, several strategies seem conceivable to intervene with hyperfibrinogenemia. Abstention from smoking and regular long-term endurance exercise significantly decrease fibrinogen. Treatment of chronic infections such as Helicobacter pylori, Chlamydia pneumoniae, or dental disease possibly influences cardiovascular risk indirectly by modifying fibrinogen levels. A number of drugs have been shown to reduce plasma fibrinogen besides their main therapeutic action; clinically, fibrates are by far the most important group. Other oral drugs with appreciable fibrinogen-lowering capacity include ticlopidine, pentoxifylline, beta-adrenergic blockers, ACE inhibitors, and several steroid hormones. Large clinical trials in patients post-myocardial infarction, with advanced periphonel arterial occlusive disease (POAD), and with diabetes mellitus, are under way, investigating in more detail the possible therapeutic efficacy of lowering fibrinogen on clinical endpoints. Aspirin might influence the physical properties of the fibrin gel structure, thereby rendering the clot more amenable to endogenous fibrinolysis. Chronic application of low dose urokinase or apheresis may be suitable in selected patient groups. Finally, a new approach consists in the interference with fibrinogen-dependent platelet aggregation through blockade of the glycoprotein IIb/IIIa-receptors.

The acute immune response to exercise: what does it mean?

The purpose of this article is to provide information about the exercise-induced alterations of cellular immune parameters depending on the intensity related to the individual anaerobic threshold (IAT) and duration of exercise. Immunological parameters were differential blood counts (CD14, CD45), monocyte subpopulations (CD14, CD16), lymphocyte subpopulations (CD3, CD4, CD8, CD45RO, CD19, CD16, CD56, HLA-DR) and natural killer cells (CD3, CD16, CD56), oxidative burst activity of neutrophils, and phagocytosis of neutrophils (flow cytometry). The main results were: (a) "Moderate" exercise (duration < 2h at about 85% of the IAT corresponding to a lactate steady state at about 2 mmol.l-1, < 30 min at the IAT corresponding to a lactate steady state of 4 mmol.l-1) elicits lower changes in cell concentrations and hormonal responses than strenuous exercise [exhaustive exercise at 100% IAT or above; (exhaustive) long-term (> 2-3h) endurance exercise]. Similar investigations about cell functions to decide about the positive or negative nature of these observations will have to follow in the future. (b) The neutrocytosis following exercise is more dependent on the duration than on the intensity of exercise. Especially exercise sessions that lead to a strong incline of the adrenocorticotropic hormone, beta-endorphin and cortisol are associated with this neutrocytosis. (c) Neutrophils' function during the exercise-induced neutrocytosis indicated by phagocytosis and oxidative burst activity is unchanged or reduced following strenuous endurance exercise, whereas bacterial URTI leads to similar neutrophil counts but significantly increased cell activities indicating the diverse meaning of the leukocytosis in infections (primed cells, enhanced cell activity, stimulated defense mechanism) and following exercise (impaired cell function, suppressed defense mechanism). (d) Regular monocytes (early differentiation stage) are strongly recruited into the circulation during long-term aerobic exercise, whereas mature monocyte cell counts (premacrophages) increase most with highly intensive (an)aerobic exercise above the IAT. Infections induced a maturation from regular to mature monocytes as a response to the infectious antigenic stimulus, whereas exercise does not, indicating the diversity between change of cell counts and function. (e) Long-term endurance diverse meaning leads to increases of activated CD45RO+ T cells (memory cell phenotype) but compared to the incline of cell concentrations and activation levels (% HLA-DR+ T cells) during infections like infectious mononucleosis this effect is small indicating only minor effects on T cell function by exercise. The effect of single bouts of exercise on immune cell counts is large but the effects on the cell function is - i.e. compared to bacterial URTI - relatively small.

49. Hyperfibrinogenemia and cardiovascular risk: possible strategies for intervention

Summary Elevated plasma fibrinogen has been identified as an independent predictor of cardiovascular diseases. Although abundant evidence suggests a causal role of fibrinogen in the pathogenesis of atherothrombotic complications, this has not yet been proven. To overcome this dilemma, several strategies seem conceivable to intervene with hyperfibrinogenemia. Abstention from smoking and regular long-term endurance exercise significantly decrease fibrinogen. Treatment of chronic infections such as Helicobacter pylori, Chlamydia pneumoniae , or dental disease possibly influences cardiovascular risk indirectly by modifying fibrinogen levels. A number of drugs have been shown to reduce plasma fibrinogen besides their main therapeutic action; clinically, fibrates are by far the most important group. Other oral drugs with appreciable fibrinogen-lowering capacity include ticlopidine, pentoxifylline, beta-adrenergic blockers, ACE inhibitors, and several steroid hormones. Large clinical trials in patients post-myocardial infarction, with advanced periphonel arterial occlusive disease (POAD), and with diabetes mellitus, are under way, investigating in more detail the possible therapeutic efficacy of lowering fibrinogen on clinical endpoints. Aspirin might influence the physical properties of the fibrin gel structure, thereby rendering the clot more amenable to endogenous fibrinolysis. Chronic application of low dose urokinase or apheresis may be suitable in selected patient groups. Finally, a new approach consists in the interference with fibrinogen-dependent platelet aggregation through blockade of the glycoprotein IIb/IIIa-receptors.

Effect of long-term endurance exercise on fibrinolytic markers

To study the long-term overall effect of habitual physical exercise on fibrinolysis, 20 sedentary males and 15 sedentary females were trained 3–4 times a week with increasing intensity during 9 months. After 24 and 36 weeks all subjects ran a 15 km and half marathon (21 km) race, respectively. Blood samples were drawn before the training programme, 5 days before both races and 5 days after the half marathon run. After the training period plasma tissue-plasminogen activator antigen concentration was slightly decreased in both the male and female population. Plasma plasminogen activator inhibitor activity decreased significantly (p<0.01) in both groups during the course of the training programme. No effect of increased fibrinolytic activity was observed, since plasma D-dimer concentrations were not changed after the test period. In summary, the results of this study demonstrate that long-term physical conditioning leads to a marked decrease in plasminogen activator inhibitor activity, without an actual increase of fibrinolytic end-products.

Enhanced left ventricular diastolic filling associated with long-term endurance training.

Normal aging is associated with an impairment in early left ventricular diastolic filling. To test the hypothesis that long-term endurance exercise training is associated with enhanced ventricular diastolic filling indices, we compared transmitral pulsed Doppler inflow spectra in healthy young adults; healthy elderly, sedentary subjects (sedentary old); and healthy elderly, endurance athletes (master athletes). Our data demonstrate that, despite an increase in left ventricular mass, early diastolic filling was enhanced in master athletes compared to the sedentary old. Blood pressure of both master athletes and the sedentary olds was greater than the young adults, but the higher blood pressure did not correlate to changes in filling parameters. Resting systolic function and heart rate were not significantly different in all three different groups. Early left ventricular filling indices in master athletes more closely resemble transmitral inflow patterns of healthy young adults. Long-term endurance exercise is associated with physiologic hypertrophy and ventricular filling dynamics more characteristic of the young than the old.

Sperm counts and reproductive hormones in male marathoners and lean controls

In women, chronic and intense endurance exercise is frequently associated with menstrual cycle alterations. In men, the effects of similar amounts of exercise are less well-studied. We tested the hypothesis that endurance exercise in men is also associated with alterations in reproductive function. We studied 12 marathon runners and 12 age-matched, lean controls; serum and semen samples were collected every 2 weeks for 12 weeks. Sperm counts, sperm morphologies, and mean levels of testosterone (T), free T, sex hormone binding globulin, cortisol, follicle-stimulating hormone, and biologically active luteinizing hormone (LH) were similar in the two groups. Mean levels of immunologically active LH were somewhat higher in the marathoners. We conclude that this level of strenuous, long-term endurance exercise does not have major adverse effects on reproductive function in men.

The adjustment of diet and insulin dose during long-term endurance exercise in type 1 (insulin-dependent) diabetic men.

We examined in 2 consecutive years the effect of a 75-km (greater than 7 h) cross country skiing on dietary and insulin requirements and glycaemic control in 9 Type 1 (insulin-dependent) diabetic patients. In the first year, the patients were hyperglycaemic (20.9 +/- 1.8 mmol/l) before the race due to excessive carbohydrate loading (65 g) and reduction (by 58%) of short-acting insulin for breakfast. In the second year, breakfast included less carbohydrate (40 g) and more protein, and the morning short-acting insulin was reduced by 35%. With this adjustment of therapy the pre-exercise hyperglycaemia was less (p less than 0.05). The morning intermediate-acting insulin was reduced by 28 and 38% in consecutive years. During both races carbohydrate intake approximated 40 g/h, and blood glucose was maintained at near normal levels after 33 km of skiing. Hypoglycaemia did not occur during exercise, but one patient had symptomatic hypoglycaemia after finishing the second race. The day after exercise insulin sensitivity was increased in all four patients studied. Insulin treated patients can perform strenuous long-term exercise and maintain near normoglycaemia with a proper adjustment of therapy. Augmented insulin sensitivity may contribute to post-exercise hypoglycaemia.

Long-term mild endurance exercise effects on the age-associated evolution of hindlimb muscle characteristics in hamsters

The purpose of the study was to describe the effects of long-term, mild daily exercise on age-associated neuromuscular changes in the Syrian hamster. Daily treadmill exercise (for 26 weeks) was administered throughout a portion (25–37%) of the life span (70–100 weeks), beginning at an age of 4 months, during which period body and muscle weights plateau and subsequently decline. Non-exercised (NEX) animals showed an increase in body weight (20%) until 7 months of age, which subsequently declined with the attainment of late adulthood to values not different from 4-month-old controls (Y) by 10.5 months. Gastrocnemius muscles were atrophied, showed twitch potentiation when stimulated in situ, and contained more type I fibers compared to young controls. Hamsters exercised from 4 to 10.5 months of age (EX) showed elevated body weights, and gastrocnemius muscles showed attenuated atrophy (muscle weight and fiber size), lack of twitch potentiation, and a significantly reduced PFK/CS enzyme ratio. Hamsters exercised only until 7 months were similar to NEX group by 10.5 months of age. Mild daily exercise, maintained throughout adult life into early senescence, attenuates muscle atrophy and promotes adaptive enzymatic changes in atrophying muscles.

Diet, muscle glycogen, and endurance performance.

Diet, muscle glycogen, and endurance performance.