Maximal Work Capacity Research Articles

Determination of maximum working capacity of retrofittable cutters on the basis of physical-mechanical features of tool hard alloys

This research is dedicated to the determination of maximum working capacity temperature of tool hard alloy cutters during a processing of parts by means of cutting made of hard-to-cut materials including assessment of possibility of using of tools made in Russian Federation without loss of the processing efficiency.

PP.25.02] EFFECT OF TRAINING OPTIMIZATION ON MAXIMAL FUNCTIONAL PARAMETERS IN SPORT-DANCERS

Objective: Improvement of the aerobic capacity is the main goal of sports preparation and cardio-vascular rehabilitation.Cardio-plulmonary stress test is a useful tool for creation of individualized training programs. Design and method: In the present study we investigated the effect of training optimization aimed at improvement of aerobic functional abilities in male amateur sport-dancers. Two maximal cardio-respiratory tests were carried out on a treadmill (at the beginning and the end of an experimental 2-month period) and the dynamic in the maximal aerobic and total ergometric work capacity of the athletes was evaluated. During the 2-month period additional aerobic training sessions were included in the athletes’ program with intensity based on the individual anaerobic threshold (AnT) determined during the first test. These workloads consisted of 60-minute jogging sessions at intensity corresponding to 65 ÷ 80% of AnT (116 ÷ 145 beats min−1) twice weekly and trekking in spare time (3–4 times during the 2-month period). Results: The follow-up functional test revealed significant increase of the measured absolute and relative values of maximal oxygen uptake (8.5%, 9.2%, respectively; p* < 0.05), of achieved maximal treadmill speed (12.2%; p* < 0.05) and decrease in maximal pulmonary ventilation (−15.9%; p* < 0.05). These changes in the analyzed main functional parameters were accompanied by statistically significant decrease in maximal lactate concentration (−17.3%; p* < 0.05) and slight decrease of the registered maximal heart rate (−3 beats min−1; p > 0.05). Conclusions: The results allowed us to conclude that the training sessions added to the athletes’ program had contributed to the established substantial positive effect on the aerobic abilities. The results confirm the view that the application of individually tailored workloads in aerobic training programs is an important factor for optimization of metabolic energy pathways and a prerequisite for marked improvement of the organism functional work capacity.

Evaluation of the metabolic rate based on the recording of the heart rate.

The assessment of harsh working conditions requires a correct evaluation of the metabolic rate. This paper revises the basis described in the ISO 8996 standard for the evaluation of the metabolic rate at a work station from the recording of the heart rate of a worker during a representative period of time. From a review of the literature, formulas different from those given in the standard are proposed to estimate the maximum working capacity, the maximum heart rate, the heart rate and the metabolic rate at rest and the relation (HR vs. M) at the basis of the estimation of the equivalent metabolic rate, as a function of the age, height and weight of the person. A Monte Carlo simulation is used to determine, from the approximations of these parameters and formulas, the imprecision of the estimated equivalent metabolic rate. The results show that the standard deviation of this estimate varies from 10 to 15%.

A model to estimate vertical speed of ascending evacuation from maximal work capacity data

This paper describes the development of an ascending evacuation model based on physical work capacity of a selected sample. The model is based on the combination of several field experiments, existing databases and pre-tests that were combined to define initial test conditions in the laboratory environment on a step machine. Maximal oxygen consumption (VO2max) of 13 male and 12 female subjects (data was pooled), was measured, and they climbed at 3 step rates specified according to individual percentage of their maximal aerobic capacity (%VO2max) levels. The first nineteen subjects were used for model development and the last six for validation. The paper gives an overview on the collected laboratory data and puts it into relation with the field data from both oxygen consumption and heart rate perspective. The maximum vertical displacement (hvert in m/min) can be calculated according to: hvert=−21.7727+0.4024∗VO2max+0.2658∗%VO2max. The discussion covers limitations and possibilities of the model and suggests the literature and databases that form the basis for practical use of the prediction model. Paper defines the needs for future work and possible information sources to improve the model.

Evaluation of the effects of olodaterol on exercise endurance in patients with chronic obstructive pulmonary disease: results from two 6-week crossover studies.

BackgroundTwo replicate, double-blind, placebo-controlled, 6-week crossover studies assessed the effect of the once-daily long-acting β2-agonist olodaterol 5 μg and 10 μg on constant work-rate cycle endurance in patients with moderate to very severe chronic obstructive pulmonary disease.MethodsPatients received placebo, olodaterol 5 μg once daily (QD) and olodaterol 10 μg QD in a randomised order for 6 weeks each, with a 2-week washout period in between. The primary end point was change in endurance time during constant work-rate cycle ergometry to symptom limitation at 75 % maximal work capacity after 6 weeks of treatment (2 h post-dose), based on log10-transformed data. Key secondary end points were inspiratory capacity at isotime and intensity of breathing discomfort at isotime.Results151 and 157 patients were randomised and treated in Studies 1222.37 and 1222.38, respectively, with 147 and 154 being included in the full analysis sets. Mean endurance time at week 6 was increased compared to placebo by 14.0 % (Study 1222.37; p < 0.001) and 11.8 % (Study 1222.38; p < 0.01) with olodaterol 5 μg, and by 13.8 % (Study 1222.37; p < 0.001) and 10.5 % (Study 1222.38; p < 0.01) with olodaterol 10 μg. Inspiratory capacity at isotime increased with olodaterol 5 μg (Study 1222.37, 0.182 L, p < 0.0001; Study 1222.38, 0.084 L, p < 0.05) and 10 μg (Study 1222.37, 0.174 L; Study 1222.38, 0.166 L; both studies, p < 0.0001), and breathing discomfort was significantly reduced in Study 1222.37 (olodaterol 5 μg, 0.77 Borg units, p < 0.001; olodaterol 10 μg, 0.63 Borg units, p < 0.01) but not Study 1222.38.ConclusionsThese studies provide further characterisation of the efficacy of olodaterol, showing that improvements in airflow (forced expiratory volume in 1 s) are associated with increases in inspiratory capacity and improvements in exercise endurance time.Trial registrationsNCT01040130 (1222.37) and NCT01040793 (1222.38).Electronic supplementary materialThe online version of this article (doi:10.1186/s12931-016-0389-5) contains supplementary material, which is available to authorized users.

Synthesis and Characterizations of MOF-199 Using PODFA as Porogen for CO&lt;sub&gt;2&lt;/sub&gt; Adsorption Applications

Copper-based metal-organic framework (MOF-199, also known as Cu-BTC and HKUST-1) materials were successfully synthesized by hydrothermal method using renewable straight-chain fatty alcohol with eight carbon chain length (i.e. octyl alcohol). The addition of palm oil derived fatty alcohol (PODFA) was suggested to act as porogen (structure directing agent) that aided the particle formation and flexible porous structure. This synthesis approach was environmental-friendly and sustainable by utilizing the fatty alcohols originated from biomass such as palm oil. The resulting MOF-199 materials exhibited single crystalline octahedral morphology structure by X-ray diffraction analyses and SEM images. The optimum ratio of octyl alcohol exhibited well-defined single octahedral particles at size range of ca. 10-50 µm and reduced by-product formation of cuprous oxide at high temperature synthesis. The nature of MOF-199 having apparently high surface area, high pore volume and low density provided the possibility in carbon capture storage. The CO2 adsorption capacity of MOF-199 investigated using high pressure volumetric analyser (HPVA-II) at ambient temperature (i.e. 25 °C) was found to be at maximum working capacity.

Greater Strength Gains after Training with Accentuated Eccentric than Traditional Isoinertial Loads in Already Strength-Trained Men.

As training experience increases it becomes more challenging to induce further neuromuscular adaptation. Consequently, strength trainers seek alternative training methods in order to further increase strength and muscle mass. One method is to utilize accentuated eccentric loading, which applies a greater external load during the eccentric phase of the lift as compared to the concentric phase. Based upon this practice, the purpose of this study was to determine the effects of 10 weeks of accentuated eccentric loading vs. traditional isoinertial resistance training in strength-trained men. Young (22 ± 3 years, 177 ± 6 cm, 76 ± 10 kg, n = 28) strength-trained men (2.6 ± 2.2 years experience) were allocated to concentric-eccentric resistance training in the form of accentuated eccentric load (eccentric load = concentric load + 40%) or traditional resistance training, while the control group continued their normal unsupervised training program. Both intervention groups performed three sets of 6-RM (session 1) and three sets of 10-RM (session 2) bilateral leg press and unilateral knee extension exercises per week. Maximum force production was measured by unilateral isometric (110° knee angle) and isokinetic (concentric and eccentric 30°.s−1) knee extension tests, and work capacity was measured by a knee extension repetition-to-failure test. Muscle mass was assessed using panoramic ultrasonography and dual-energy x-ray absorptiometry. Surface electromyogram amplitude normalized to maximum M-wave and the twitch interpolation technique were used to examine maximal muscle activation. After training, maximum isometric torque increased significantly more in the accentuated eccentric load group than control (18 ± 10 vs. 1 ± 5%, p < 0.01), which was accompanied by an increase in voluntary activation (3.5 ± 5%, p < 0.05). Isokinetic eccentric torque increased significantly after accentuated eccentric load training only (10 ± 9%, p < 0.05), whereas concentric torque increased equally in both the accentuated eccentric load (10 ± 9%, p < 0.01) and traditional (9 ± 6%, p < 0.01) resistance training groups; however, the increase in the accentuated eccentric load group was significantly greater (p < 0.05) than control (1 ± 7%). Knee extension repetition-to-failure improved in the accentuated eccentric load group only (28%, p < 0.05). Similar increases in muscle mass occurred in both intervention groups. In summary, accentuated eccentric load training led to greater increases in maximum force production, work capacity and muscle activation, but not muscle hypertrophy, in strength-trained individuals.

The effect of age and unilateral leg immobilization for 2 weeks on substrate utilization during moderate-intensity exercise in human skeletal muscle.

This study aimed to provide molecular insight into the differential effects of age and physical inactivity on the regulation of substrate metabolism during moderate-intensity exercise. Using the arteriovenous balance technique, we studied the effect of immobilization of one leg for 2weeks on leg substrate utilization in young and older men during two-legged dynamic knee-extensor moderate-intensity exercise, as well as changes in key proteins in muscle metabolism before and after exercise. Age and immobilization did not affect relative carbohydrate and fat utilization during exercise, but the older men had higher uptake of exogenous fatty acids, whereas the young men relied more on endogenous fatty acids during exercise. Using a combined whole-leg and molecular approach, we provide evidence that both age and physical inactivity result in intramuscular lipid accumulation, but this occurs only in part through the same mechanisms. Age and inactivity have been associated with intramuscular triglyceride (IMTG) accumulation. Here, we attempt to disentangle these factors by studying the effect of 2weeks of unilateral leg immobilization on substrate utilization across the legs during moderate-intensity exercise in young (n=17; 23±1years old) and older men (n=15; 68±1years old), while the contralateral leg served as the control. After immobilization, the participants performed two-legged isolated knee-extensor exercise at 20±1W (∼50% maximal work capacity) for 45min with catheters inserted in the brachial artery and both femoral veins. Biopsy samples obtained from vastus lateralis muscles of both legs before and after exercise were used for analysis of substrates, protein content and enzyme activities. During exercise, leg substrate utilization (respiratory quotient) did not differ between groups or legs. Leg fatty acid uptake was greater in older than in young men, and although young men demonstrated net leg glycerol release during exercise, older men showed net glycerol uptake. At baseline, IMTG, muscle pyruvate dehydrogenase complex activity and the protein content of adipose triglyceride lipase, acetyl-CoA carboxylase 2 and AMP-activated protein kinase (AMPK)γ3 were higher in young than in older men. Furthermore, adipose triglyceride lipase, plasma membrane-associated fatty acid binding protein and AMPKγ3 subunit protein contents were lower and IMTG was higher in the immobilized than the contralateral leg in young and older men. Thus, immobilization and age did not affect substrate choice (respiratory quotient) during moderate exercise, but the whole-leg and molecular differences in fatty acid mobilization could explain the age- and immobilization-induced IMTG accumulation.

폐타이어 열분해에 의한 카본블랙을 이용한 황화수소와 암모니아 제거를 위한 흡착제 개발

Hydrogen sulfide and ammonia are one of the common malodorous compounds that can be found in emissions from many sewages treatment plants and industrial plants. Therefore, removing these harmful gases from emissions is of significance in both life and industry because they can cause health problems to human and detrimental effects on the catalysts. In this work, pyrolytic carbon blacks from waste tires were used to develop adsorbent with good adsorption capacity for removal of hydrogen and ammonia. Pellet-type adsorbents were prepared by a mixture of carbon black, metal oxide and sodium hydroxide or hydrochloric acid, and their adsorption capacities were estimated by using breakthrough curve of a continuous fixed bed adsorption column at ambient condition. The adsorbent manufactured with a mixture of carbon black, iron oxide(III) and sodium hydroxide showed the maximum working capacity of hydrogen sulfide. For ammonia, maximum working capacity was obtained by the adsorbent manufactured with a mixture of carbon black, copper oxide(II) and hydrochloric acid.

WS14.3 Exercise testing as diagnostic marker for the outcome after intravenous antibiotic therapy for patients with cystic fibrosis

Objective To assess the success of intravenous antibiotic therapy in patients with cystic fibrosis (CF) with pulmonary exacerbations the forced expiratory volume in 1 second (FEV 1 ) of lung function testing is the routinely used diagnostic method. In this study we aim to investigate maximal exercise testing on bicycle ergometer to evaluate the outcome after antibiotic treatment. Methods We measured the effects of hospital treatmentwith intravenous antibiotics on peak exercise capacity. For this purpose progressive bicycle exercise test was performed at admission and discharge to determine maximum working capacity (Wmax). Oxygen saturation and heart rate as well as O 2 demand have been continuously measured over time during ergometry. FEV1 was determined by lung function testing before and after treatment. Results 190 bicycle ergometries have been performed in patients with CF and pulmonary exacerbation who received hospital treatment from 9/2012 until 9/2014 at the Charite university clinic in Berlin. Wmax improved in 43 of 95 of treated CF patients (33.7%). An increment of the FEV1 could be detected in 75 of 95 subjects (78.9%). Interestingly 8 subjects (8.4%) with improved Wmax showed a decrease in FEV 1 and 10 subjects (10.5%) with a better result in lung function testing after therapy showed a declined Wmax. Conclusion Significant results could be obtained for an improvement of Wmax, O 2 consumption, heart rate and FEV 1 after therapy. These results indicate that exercise testing should be considered as a further diagnostic instrument to evaluate the outcome after antibiotic therapy in patients with CF.

Postnatal Undernutrition (PUN) Permanently Alters the Heart to Reduce Maximal Exercise Capacity in Female Mice

Undernutrition during development increases the risk for adult cardiovascular disease. To determine if PUN alters heart structure function, and maximal exercise capacity in adulthood, newborn control mouse pups were fostered to dams fed a control (CON; 20% protein) or a protein-restricted diet (PUN; 8% protein; n=7-10 litters/treatment). At 21 d (PN21) pups were fed the CON diet ad lib. At PN70 a maximal treadmill test was performed to determine VO2peak; maximal vertical work was calculated for the final 30 sec. At PN80 cardiac function was evaluated by echocardiography. VO2peak was the same in CON and PUN mice and higher in males than females (249 + 9 and 169 + 6 ml/hr, respectively, P<0.001); gender x diet, NS. Maximal vertical work at VO2peak was higher in CON than PUN females (1.64 + 0.07 and 1.33 + 0.06 J/min, respectively, P < 0.01) but not males; gender x diet, P<0.02. Resting cardiac output was higher in CON than PUN offspring (18.8 + 0.7 and 16.3 + 0.7 ml/min, respectively; P<0.02) and in males than females (19.2 + 0.7 and 15.9 + 0.7 ml/min, respectively; P<0.01; gender x diet, NS) due to differences in stroke volume (CON: 43.0 ± 1.5; PUN: 37.7 ± 1.4 µl; P<0.05; males: 46.8 ± 1.5; females: 34.0 ± 1.4 µl; P<0.05), and left ventricular mass (CON: 104 ± 5; PUN: 90 ± 5 mg; P<0.05; males: 108 ± 5; females: 90 ± 5 mg; P<0.05). Thus, PUN permanently reduces left ventricular mass which in turn reduces stroke volume and maximal treadmill work capacity in female mice. Male mice were able to compensate for the reduction in cardiac output and maintain maximal exercise capacity. Supported by NIH AR46308, T32HL07676, USDA/ARS 6250-51000-051

Electrical Myostimulation (EMS) Improves Glucose Metabolism and Oxygen Uptake in Type 2 Diabetes Mellitus Patients--Results from the EMS Study.

In patients with type 2 diabetes mellitus (T2DM) exercise training is recommended to improve glycemic control. Electrical myostimulation (EMS) of skeletal muscles is a new method to increase exercise capacity in patients with chronic heart failure. The aim of this study was to investigate the effects of EMS in T2DM on glucose metabolism, body composition, and exercise performance using a newly designed stimulation suit that involves trunk, leg, and arm muscles. Fifteen individuals (nine males; 61.7±14.8 years old) were trained for 10 weeks twice weekly for 20 min with EMS. Effects on glucose, glycosylated hemoglobin (HbA(1c)), oxygen consumption, and body composition were evaluated. There was a significant increase of oxygen uptake at the aerobic threshold from 12.3±0.8 to 13.3±0.7 mL/kg/min (P=0.003) and of maximal work capacity from 96.9±6.4 to 101.4±7.9 W (P=0.046), with a concomitant trend for improved maximal oxygen uptake (from 14.5±0.9 to 14.7±0.9 mL/kg/min [P=0.059]). Fasting blood glucose level decreased from 164.0±12.5 to 133.4±9.9 mg/dL (P=0.001), and HbA(1c) level decreased from 7.7±0.3% to 7.2±0.3% (P=0.041), whereas mean total weight (from 101.5±4.0 to 103.1±4.3 kg) and proportion of body fat (from 38.8±3.2% to 40.3±3.4%) remained statistically unchanged. EMS can improve glucose metabolism and functional performance in T2DM patients. These data suggest that EMS might emerge as a novel additional therapeutic mode of exercise training and might help patients to overcome their sedentary lifestyle.

A convenient prediction model for complete recovery time after exhaustion in high-intensity work

We aimed to propose a convenient model for predicting complete recovery time (CRT) after exhaustion in high-intensity work. Before participating in the laboratory test, each of the 47 young adult subjects provided demographic information and filled out the perceived functional ability (PFA) and physical activity rating (PA-R) questionnaires. All subjects were required to perform one cycling test (at 70% maximum working capacity). Subjects continued cycling until exhaustion and then sat and recovered until their heart rates (HR) returned to baseline values. We found that CRT was significantly correlated with relative body mass index, the PFA score, PA-R score and maximum heart rate (HRmax). Accordingly, a prediction model for CRT was proposed. Furthermore, by replacing HRmax with age-predicted maximal HR, we obtained a more convenient prediction model that was independent of any physiological indexes that can only be obtained by subject testing.

Men born in 1913 followed to age 100 years

Objectives. To examine causes of death for men above 80 years of age, and health status in centenarians in a cohort of men followed from age 50 years. Factors of importance for survival were studied. Design. A representative sample of men born in 1913 was first examined in 1963 and re-examined at ages 54, 60, 67, 75, 80 and 100 years. Results. Of 973 selected men, 855 (88%) were examined at age 50, and 10 were alive at age 100.Twenty-seven percent lived until 80 years. Cardiovascular disease was the most common cause of death after this age. Dementia was recorded in two of ten men at age 100. Long survival was related to the mothers' high age at death, to non-smoking, high social class at age 50 and high maximum working capacity at age 54 years. At age 100, the seven examined men had low/normal blood pressure. Serum values of troponin T, N-terminal pro-brain natriuretic peptides and C-reactive protein were elevated, but echocardiographic findings were normal. Conclusions. Ten men experienced their 100th birthday. Survival was related to non-smoking, mothers' high age at death, high social class and previous high physical working capacity. Age-adjusted reference levels for laboratory tests are needed for centenarians.

Birth order and physical fitness in early adulthood: Evidence from Swedish military conscription data

Physical fitness at young adult ages is an important determinant of physical health, cognitive ability, and mortality. However, few studies have addressed the relationship between early life conditions and physical fitness in adulthood. An important potential factor influencing physical fitness is birth order, which prior studies associate with several early- and later-life outcomes such as height and mortality. This is the first study to analyse the association between birth order and physical fitness in late adolescence. We use military conscription data on 218,873 Swedish males born between 1965 and 1977. Physical fitness is measured by a test of maximal working capacity, a measure of cardiovascular fitness closely related to V02max. We use linear regression with sibling fixed effects, meaning a within-family comparison, to eliminate the confounding influence of unobserved factors that vary between siblings. To understand the mechanism we further analyse whether the association between birth order and physical fitness varies by sibship size, parental socioeconomic status, birth cohort or length of the birth interval. We find a strong, negative and monotonic relationship between birth order and physical fitness. For example, third-born children have a maximal working capacity approximately 0.1 (p < 0.000) standard deviations lower than first-born children. The association exists both in small (3 or less children) and large families (4 or more children), in high and low socioeconomic status families, and amongst cohorts born in the 1960s and the 1970s. While in the whole population the birth order effect does not depend on the length of the birth intervals, in two-child families a longer birth interval strengthens the advantage of the first-born. Our results illustrate the importance of birth order for physical fitness, and suggest that the first-born advantage already arises in late adolescence.

Dietary nitrate supplementation improves exercise performance and decreases blood pressure in COPD patients

Dietary nitrate (NO3−) supplementation via beetroot juice has been shown to increase the exercise capacity of younger and older adults. The purpose of this study was to investigate the effects of acute NO3− ingestion on the submaximal constant work rate exercise capacity of COPD patients. Fifteen patients were assigned in a randomized, single-blind, crossover design to receive one of two treatments (beetroot juice then placebo or placebo then beetroot juice). Submaximal constant work rate exercise time at 75% of the patient's maximal work capacity was the primary outcome. Secondary outcomes included plasma NO3− and nitrite (NO2−) levels, blood pressure, heart rate, oxygen consumption (VO2), dynamic hyperinflation, dyspnea and leg discomfort. Relative to placebo, beetroot ingestion increased plasma NO3− by 938% and NO2− by 379%. Median (+interquartile range) exercise time was significantly longer (p = 0.031) following the ingestion of beetroot versus placebo (375.0 + 257.0 vs. 346.2 + 148.0 s, respectively). Compared with placebo, beetroot ingestion significantly reduced iso-time (p = 0.001) and end exercise (p = 0.008) diastolic blood pressures by 6.4 and 5.6 mmHg, respectively. Resting systolic blood pressure was significantly reduced (p = 0.019) by 8.2 mmHg for the beetroot versus the placebo trial. No other variables were significantly different between the beetroot and placebo trials. These results indicate that acute dietary NO3− supplementation can elevate plasma NO3− and NO2− concentrations, improve exercise performance, and reduce blood pressure in COPD patients.

Establishing the Criterion Validity and Reliability of Common Methods for Quantifying Training Load

The purpose of this investigation was to compare the criterion validity and test-retest reliability of common methods for quantifying training load. Ten (5 men and 5 women) recreational athletes (mean ± SD, VO2max: 37.0 ± 4.3 ml·kg-1·min-1; age: 23.8 ± 8.4 years) completed 18 randomly assigned steady state (SS) and interval (INT) training sessions during a 6-week period. Steady-state sessions were 18 minutes in duration and were performed at 35, 50, and 65% of maximum work capacity (Wmax). Interval sessions were performed at 50, 60, and 70% of Wmax with a work to rest ratio of 1:1 and matched for total work with the 50% SS session. Oxygen consumption (VO2) and heart rate (HR) were measured throughout all sessions, whereas blood lactate concentration and rating of perceived exertion (RPE) measures were taken every 6 minutes during sessions. Session-RPE (sRPE) was collected after each exercise bout. All individual correlations between VO2 and external work (r = 0.88-0.97), HR (r = 0.65-0.90), and RPE-based methods (r = 0.55-0.89) were statistically significant. External work correlated best with the total V[Combining Dot Above]O2 and was significantly different from RPE-based methods. A poor level of test-retest reliability was shown for Banister's TRIMP (15.6% coefficient of variation [CV]), Lucia's TRIMP (10.7% CV), and sRPE (28.1% CV). Good reliability was shown for HR (3.9% CV) and a moderate level for RPE 6-20 (8.5% CV) as a measure of exercise intensity. These results suggest external work to be the most valid and reliable method for quantifying training load. Poor levels of reliability were reported for each of the HR-based TRIMP methods and RPE-based methods.

Effect of sildenafil on skeletal and cardiac muscle in Becker muscular dystrophy

Patients with Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy lack neuronal nitric oxide synthase (nNOS). nNOS mediates physiological sympatholysis, thus ensuring adequate blood supply to working muscle. In mice lacking dystrophin, restoration of nNOS effects by a phosphodiesterase 5 (PDE5) inhibitor (sildenafil) improves skeletal and cardiac muscle performance. Sildenafil also improves blood flow in patients with BMD. We therefore hypothesized that sildenafil would improve blood flow, maximal work capacity, and heart function in patients with BMD. A randomized, double-blind, placebo-controlled crossover design with two 4-week periods of treatment, separated by 2-week washout was used. We assessed brachial artery blood flow during maximal handgrip exercise, 6-minute walk test, maximal oxidative capacity, and life quality; cardiac function was evaluated by magnetic resonance imaging (MRI) at rest and during maximal handgrip exercise. Muscle nNOS and PDE5 were tested with Western blotting in 5 patients. Sixteen patients completed all skeletal muscle evaluations, and 13 completed the cardiac MRI investigations. Sildenafil had no effect on any of the outcome parameters. No serious adverse effects were recorded. PDE5 and nNOS were deficient in 5 of 5 biopsies. Despite positive evidence from animal models of dystrophinopathy and physiological findings in patients with BMD, this double-blind, placebo-controlled clinical study showed no effect of sildenafil on blood flow, maximal work capacity, and heart function in adults with BMD. This discrepancy may be explained by a significant downregulation of PDE5 in muscle.

Pushing the limits: exercise stress in the healthy human heart.

Pushing the limits: exercise stress in the healthy human heart.

Vitamin D replacement therapy in patients with cardiac syndrome X.

The aim of present study was to assess whether vitamin D, with proven beneficial effects on the cardiovascular system, has any effect on angina and exercise-induced ischemia in patients with cardiac syndrome X and low serum vitamin D. Patients with cardiac syndrome X and low serum vitamin D3 were studied before and after treatment with an intramuscular injection of vitamin D3 (300,000 units, every other week for 2 months). We determined the angina episode (per day) and several indices of exercise capacity. At the end of the treatment course (75±6 day), a significant increase of serum vitamin D3 occurred and was within the normal range (45±8 ng/ml) and the frequency of angina improved significantly (p=0.003). Exercise duration and maximal work capacity increased significantly (p<0.001). Maximal ST-segment depression (mm) decreased significantly (p=0.001). The calculated Duck treadmill score improved significantly (p=0.001). Our findings show that vitamin D replacement therapy in patients with cardiac syndrome X and vitamin D deficiency dramatically improves symptoms and signs of ischemia.