Maximal Bicycle Exercise Research Articles

Isometric knee extensor fatigue following a Wingate test: peripheral and central mechanisms

Central and peripheral fatigue have been explored during and after running or cycling exercises. However, the fatigue mechanisms associated with a short maximal cycling exercise (30 s Wingate test) have not been investigated. In this study, 10 volunteer subjects performed several isometric voluntary contractions using the leg muscle extensors before and after two bouts of cycling at 25% of maximal power output and two bouts of Wingate tests. Transcranial magnetic stimulation (TMS) and electrical motor nerve stimulation (NM) were applied at rest and during the voluntary contractions. Maximal voluntary contraction (MVC), voluntary activation (VA), twitch amplitude evoked by electrical nerve stimulation, M wave and motor potential evoked by TMS (MEP) were recorded. MVC, VA and twitch amplitude evoked at rest by NM decreased significantly after the first and second Wingate tests, indicating central and peripheral fatigue. MVC and VA, but not the twitch amplitude evoked by NM, recovered before the second Wingate test. These results suggest that the Wingate test results in a decrease in MVC associated with peripheral and central fatigue. While the peripheral fatigue is associated with an intramuscular impairment, the central fatigue seems to be the main reason for the Wingate test-induced impairment of MVC.

Isolated Quadriceps Training Restores Whole Body Exercise Capacity in CHF

The benefit of isolated (i.e., small muscle mass) muscle training and its potential translation to whole body exercise in patients with chronic heart failure (CHF) has been recognized, however the mechanisms responsible for this positive outcome remain poorly understood. PURPOSE: To study oxygen (O2) transport and metabolism at maximal cycle (whole body) and knee extensor (KE, small muscle mass) exercise in patients with CHF. METHODS: Eight healthy controls and 6 CHF patients commenced 8 weeks of KE training (both legs, separately). Before and after training, they underwent cycle and KE maximal exercise studies. RESULTS: Pre-training cycling and KE exercise peak leg O2 uptake (VO2) were 17% and 15% lower, respectively, in the patients compared to controls. Although KE training did not alter cardiac output at maximal KE or cycle exercise, it increased O2 delivery (by 54%), arterial-venous O2 difference (by 10%), and muscle O2 conductance (by 39%) at maximal KE exercise, yielding an increase in peak single leg VO2 of 53%, which exceeded untrained control subject values. Post-training, during maximal cycling, O2 delivery (40%), arterial-venous O2 difference (15%), and muscle O2 conductance (DMO2) (52%) all increased, yielding a 40% greater peak leg VO2, matching that of the controls. CONCLUSION: Small muscle mass exercise training-induced improvements in both peripheral convective and diffusive O2 transport and subsequent O2 utilization are the mechanisms responsible for the increased whole body exercise capacity in patients with CHF. Such clear improvements in these factors and exercise capacity support the efficacy of small muscle mass training as a powerful approach to promote a metabolic reserve and maintain physical function in the face of continuing central limitations associated with CHF. Supported by NIH grant PO1 HL091830 and VA E6910R.

Validity Of The Borg Rpe Scale For Parkinson's Patients

Ratings of perceived exertion (RPE) have been shown to be a valid and reliable estimate of exercise intensity in healthy populations, however, there is some indication that effort perception may be different in those with Parkinson's disease (PD). RPE is a useful tool to monitor exercise intensity, and with increasing knowledge of the benefit of exercise to PD patients, it is important to examine the efficacy of the RPE scale in this population. PURPOSE: To examine the validity of the Borg RPE scale in PD patients undergoing two maximal progressive cycling exercise tests. METHODS: 39 males and females (58.59 ± 8.11 yrs) with a clinical diagnosis of idiopathic Parkinson's disease completed two maximal progressive cycling exercise tests separated by eight weeks. Heart rate was monitored throughout, with RPE being recorded during the last minute of each stage of the test. RESULTS: Univariate correlation analysis combining both progressive exercise tests data demonstrated a positive relationship between RPE and heart rate (r = 0.61) and RPE and workload (r = 0.77). Separate mixed effects model regression analyses demonstrated that RPE scores were significant associated with heart rate (F = 4.6, p < 0.001) and workload (F = 92.3, p < 0.001). CONCLUSION: The Borg RPE scale was significantly and positively associated with both heart rate and workload in patients with Parkinson's disease during progressive exercise to maximal exertion. This strong correlation between PD patient RPE and HR suggests that exercise recommendations made to PD patients could incorporate the Borg RPE scale to help ensure PD patients exercise at an appropriate intensity. This project supported by R21 HD056316 and Department of Veteran Affairs B6678R grants.

Effect of l-ornithine hydrochloride ingestion on intermittent maximal anaerobic cycle ergometer performance and fatigue recovery after exercise

L-Ornithine plays an important role in ammonia metabolism via the urea cycle. This study aimed to examine the effect of L-ornithine hydrochloride ingestion on ammonia metabolism and performance after intermittent maximal anaerobic cycle ergometer exercise. Ten healthy young adults (age, 23.8 ± 3.9 year; height, 172.3 ± 5.5 cm; body mass, 67.7 ± 6.1 kg) with regular training experience ingested L-ornithine hydrochloride (0.1 g/kg, body mass) or placebo after 30 s of maximal cycling exercise. Five sets of the same maximal cycling exercise were conducted 60 min after ingestion, and maximal cycling exercise was conducted after a 15 min rest. The intensity of cycling exercise was based on each subject's body mass (0.74 N kg(-1)). Work volume (watt), peak rpm (rpm) before and after intermittent maximal ergometer exercise and the following serum parameters were measured before ingestion, immediately after exercise and 15 min after exercise: ornithine, ammonia, urea, lactic acid and glutamate. Peak rpm was significantly greater with L-ornithine hydrochloride ingestion than with placebo ingestion. Serum ornithine level was significantly greater with L-ornithine hydrochloride ingestion than with placebo ingestion immediately and 15 min after intermittent maximal cycle ergometer exercise. In conclusion, although maximal anaerobic performance may be improved by L-ornithine hydrochloride ingestion before intermittent maximal anaerobic cycle ergometer exercise, the above may not depend on increase of ammonia metabolism with L-ornithine hydrochloride.

Diaphragm Fatigue after Submaximal Exercise with Chest Wall Restriction

We asked whether submaximal exercise with chest wall restriction (CWR), as a model of restrictive pulmonary disease, would result in fatigue of the diaphragm in healthy humans. To address this question, we used cervical magnetic stimulation of the phrenic nerves along with measures of transdiaphragmatic pressure. Seven healthy young men (30 ± 7 yr) completed pulmonary function tests and a maximal cycle exercise test. On a separate day, baseline measures of diaphragm contractility were obtained followed by cycle exercise at 45% of maximum intensity for 10 min with no restriction (NCWR). Diaphragm contractility was assessed again at 10 and 30 min after exercise. One hour later, inelastic straps were applied to reduce forced vital capacity by 40% followed by exercise at the same intensity. Diaphragm contractility was reassessed at 10 and 30 min after exercise. During exercise, the work of breathing, respiratory pressures, ventilatory parameters, and perceptions of respiratory and leg discomfort were recorded. The work of breathing and dyspnea ratings were greater during CWR exercise compared with NCWR (P < 0.05). The CWR condition had reductions in diaphragm contractility 10 min after exercise using nonpotentiated (-20.2% ± 15.3%) or potentiated twitches (-23.3% ± 12.4%, P < 0.05). There were no differences after exercise for NCWR (P > 0.05). The reduction in diaphragm contractility was correlated with the inspiratory elastic work of breathing (r2 = 0.74, P < 0.05). We conclude that fatigue of the diaphragm occurs under restricted conditions and likely contributes to poor exercise tolerance in patients with restrictive disease.

Neuromuscular fatigue after maximal exercise in patients with cystic fibrosis

The aim of this study was to determine whether patients with cystic fibrosis (CF), despite their ventilatory limitation, would develop neuromuscular fatigue of quadriceps muscles following a maximal cycling exercise. Eleven adults with CF (age = 26.8 ± 6.9 years; forced expiratory volume in 1 s = 54.1 ± 12.8% predicted) and 11 age-matched healthy subjects performed a maximal incremental cycle test with respiratory gas exchange measurements. Maximal voluntary contraction (MVC) and electromyographic (EMG) activity of the vastus medialis muscle were recorded before and after exercise. Neural and contractile properties of the quadriceps were also investigated using femoral nerve electrical stimulation. Patients had lower exercise capacity, peak oxygen uptake and MVC than controls. MVC fell significantly postexercise in both groups (CF: −20 ± 10%, controls: −19 ± 6%; p < 0.01). EMG root mean square values, M-wave amplitude and duration were unchanged in both groups. Peak twitch (−46.9 ± 13.8%), maximal rate of twitch torque development (−50.3 ± 13.8%) and relaxation (−35.2 ± 19.5%) were all reduced after exercise in CF patients. The control group followed the same pattern (−38.4 ± 14.4%, −42.1 ± 14.7% and −15 ± 20.4%) but the statistical significance was not reached for the maximal rate of twitch torque relaxation. In conclusion, CF patients demonstrated lower limb fatigue following symptom-limited cycle exercise, which was comparable to that exhibited by healthy controls. This fatigue may be due to contractile impairments and not to transmission failure. Further studies should be conducted in a larger sample to confirm these preliminary results.

Sex influence on myocardial function with exercise in adolescents

Ventricular systolic functional response to exercise has been reported to be superior in adult men compared to women. This study explored myocardial responses to maximal upright progressive exercise in late pubertal males and females. Doppler echocardiographic techniques were utilized to estimate myocardial function response to a bout of progressive cycle exercise. Systolic functional capacity, as indicated by ejection rate (12.5 +/- 2.8 and 13.1 +/- 1.0 [x10(-2)] ml s(-1) cm(-2) for boys and girls, respectively) and peak aortic velocity (208 +/- 45 and 196 +/- 12 cm s(-1), respectively) at maximal exercise, did not differ between the two groups. Similarly, peak values as well as increases in transmitral pressure gradient (mitral E flow velocity), ventricular relaxation (tissue Doppler imaging E'), and left ventricular filling pressure (E/E' ratio) as estimates of diastolic function were similar in males and females. This study failed to reveal qualitative or quantitative differences between adolescent boys and girls in ventricular systolic or diastolic functional responses to maximal cycle exercise.

The minimal important difference of exercise tests in severe COPD

Our aim was to determine the minimal important difference (MID) for 6-min walk distance (6MWD) and maximal cycle exercise capacity (MCEC) in patients with severe chronic obstructive pulmonary disease (COPD). 1,218 patients enrolled in the National Emphysema Treatment Trial completed exercise tests before and after 4-6 weeks of pre-trial rehabilitation, and 6 months after randomisation to surgery or medical care. The St George's Respiratory Questionnaire (domain and total scores) and University of California San Diego Shortness of Breath Questionnaire (total score) served as anchors for anchor-based MID estimates. In order to calculate distribution-based estimates, we used the standard error of measurement, Cohen's effect size and the empirical rule effect size. Anchor-based estimates for the 6MWD were 18.9 m (95% CI 18.1-20.1 m), 24.2 m (95% CI 23.4-25.4 m), 24.6 m (95% CI 23.4-25.7 m) and 26.4 m (95% CI 25.4-27.4 m), which were similar to distribution-based MID estimates of 25.7, 26.8 and 30.6 m. For MCEC, anchor-based estimates for the MID were 2.2 W (95% CI 2.0-2.4 W), 3.2 W (95% CI 3.0-3.4 W), 3.2 W (95% CI 3.0-3.4 W) and 3.3 W (95% CI 3.0-3.5 W), while distribution-based estimates were 5.3 and 5.5 W. We suggest a MID of 26 ± 2 m for 6MWD and 4 ± 1 W for MCEC for patients with severe COPD.

Force-Velocity Relationship in Cycling Revisited

Maximal cycling exercise has been widely used to describe the power-velocity characteristics of lower-limb extensor muscles. This study investigated the contribution of each functional sector (i.e., extension, flexion, and transitions sectors) on the total force produced over a complete pedaling cycle. We also examined the ratio of effective force to the total pedal force, termed index of mechanical effectiveness (IE), in explaining differences in power between subjects. Two-dimensional pedal forces and crank angles were measured during a cycling force-velocity test performed by 14 active men. Mean values of forces, power output, and IE over four functional angular sectors were assessed: top = 330 degrees -30 degrees , downstroke = 30 degrees -150 degrees , bottom = 150 degrees -210 degrees , and upstroke = 210 degrees -330 degrees . Linear and quadratic force-velocity and power-velocity relationships were obtained for downstroke and upstroke. Maximal power output (Pmax) generated over these two sectors represented, respectively, 73.6% +/- 2.6% and 10.3% +/- 1.8% of Pmax assessed over the entire cycle. In the whole group, Pmax over the complete cycle was significantly related to Pmax during the downstroke and upstroke. IE significantly decreased with pedaling rate, especially in bottom and upstroke. There were significant relationships between power output and IE for top and upstroke when the pedaling rate was below or around the optimal value and in all the sectors at very high cadences. Although data from force-velocity test primarily characterize the muscular function involved in the downstroke phase, they also reflect the flexor muscles' ability to actively pull on the pedal during the upstroke. IE influences the power output in the upstroke phase and near the top dead center, and IE accounts for differences in power between subjects at high pedaling rates.

Effect of Training Status on Mood after an Immediate Bout of Maximal Treadmill and Cycle Exercise in Young Women

Effect of Training Status on Mood after an Immediate Bout of Maximal Treadmill and Cycle Exercise in Young Women

Effects of 4-week Supramaximal Exercise Training under Normobaric Hypoxia on Anaerobic Energy Release in Cyclists

PURPOSE: This study examined the effect of supramaximal pedaling exercise training under normobaric hypoxia on anaerobic energy release in cyclists. METHODS: Thirteen collegiate cyclists were randomly assigned to normoxic (NT; 20.9% O2) or hypoxic (HT; 13.5% O2) training groups. Both groups engaged in supramaximal pedaling training for 4 weeks (50 sec × 7.5% body weight × 2 (with a 10-min rest) /day, 2 days/week). All subjects performed three exercise tests before the 4-week training: 1) a maximal incremental cycling exercise test to determine their maximum oxygen uptake (VO2 peak); 2) 12 submaximal cycling tests to establish the VO2- workload × cadence relationship for determining the oxygen demand of supramaximal cycling; and 3) a 40-second Wingate anaerobic test (WAnT) to determine the anaerobic energy release using a Douglas bag. The anaerobic energy release was evaluated as the accumulated oxygen deficit over 40 seconds. After the 4-week training period, they repeated the WAnT. RESULTS: After training, the mechanical power output during the WAnT was increased between 20 and 40 sec in the HT group (P < 0.05), whereas the O2 demand, O2 deficit, and percentages of anaerobic energy release during WAnT were not changed after the 4-week training in both groups. CONCLUSIONS: The results suggest that 50-second supramaximal cycling exercise training in 13.5% O2 might enhance the mechanical power output, but not the anaerobic energy release in collegiate cyclists.

L-Arginine supplementation improves exercise capacity after a heart transplant

Endothelial dysfunction is associated with the decreased exercise capacity observed in heart-transplant (HTx) recipients. L-arginine supplementation (LAS) stimulates the nitric oxide (NO) pathway and restores endothelial function. We compared exercise capacity in healthy subjects and HTx patients and investigated whether chronic LAS might improve exercise capacity and NO/endothelin balance after an HTx. Clinical, echocardiographic, and exercise characteristics were measured in 11 control subjects and 22 HTx recipients. In a prospective, double-blind study, the 22 HTx recipients performed a 6-min exercise [6-min-walk test (6MWT)] and a maximal bicycle exercise test before and after a 6-wk period of placebo intake or LAS. Endothelial function was measured by analyzing blood NO metabolites, endothelin, and the resulting NO/endothelin balance. Exercise capacity decreased after transplantation. Unlike with the placebo intake, 6 wk of LAS improved quality of life in HTx recipients (mean +/- SEM Minnesota Score: from 15.3 +/- 1.3 to 10.6 +/- 1.1; P < 0.001) and their submaximal exercise capacity. The distance walked during the 6MWT increased (from 525 +/- 20 to 580 +/- 20 m; P = 0.002), and the ventilatory threshold during the incremental test was delayed by 1.2 min (P = 0.01). Central factors such as resting stroke volume, systolic pulmonary arterial pressure, cardiac systolodiastolic functions, and heart-rate reserve were not modified, but LAS significantly increased the NO:endothelin ratio (from 2.49 +/- 0.38 to 3.31 +/- 0.39; P = 0.03). Oral LAS may be a useful adjuvant therapeutic to improve quality of life and exercise tolerance in HTx recipients.

Limited Maximal Exercise Capacity in Patients With Chronic Heart Failure: Partitioning the Contributors

This study aimed to assess the factors limiting maximal exercise capacity in patients with chronic heart failure (CHF). Maximal exercise capacity, an important index of health in CHF, might be limited by central and/or peripheral factors; however, their contributions remain poorly understood. We studied oxygen (O2) transport and metabolism at maximal cycle (centrally taxing) and knee-extensor (KE) (peripherally taxing) exercise in 12 patients with CHF and 8 healthy control subjects in normoxia and hyperoxia (100% O2). Peak oxygen uptake (VO2) while cycling was 33% lower in CHF patients than in control subjects. By experimental design, peak cardiac output was reduced during KE exercise when compared with cycling (approximately 35%); although muscle mass specific peak leg VO2was increased equally in both groups (approximately 70%), VO2in the CHF patients was still 28% lower. Hyperoxia increased O2carriage in all cases but only facilitated a 7% increase in peak leg VO2in the CHF patients during cycling, the most likely scenario to benefit from increased O2delivery. Several relationships, peak leg VO2(KE + cycle) to capillary-fiber-ratio and capillaries around a fiber to mitochondrial volume, were similar in both groups (r = 0.6–0.7). Multiple independent observations, including a significant skeletal muscle metabolic reserve, suggest skeletal muscle per se contributes minimally to limiting maximal cycle exercise in CHF or healthy control subjects. However, the consistent attenuation of the convective and diffusive components of O2transport (25% to 30%) in patients with CHF during both cycle and even KE exercise compared with control subjects reveals an underlying peripheral O2transport limitation from blood to skeletal muscle in this pathology.

Dichloroacetate Modulates the Oxidative Stress and Inflammatory Response to Exercise in COPD

Impaired skeletal muscle function contributes to exercise intolerance in patients with COPD. Exercise-induced oxidative stress may initiate or accelerate impaired muscle function. Dichloroacetate (DCA) activates muscle pyruvate dehydrogenase complex (PDC) at rest, reducing inertia in mitochondrial energy delivery at the onset of exercise and thereby diminishing anaerobic energy production. This study aimed to determine whether DCA infusion also may reduce exercise-induced systemic oxidative stress and inflammatory response in patients with COPD. A randomized, double-blind crossover design was used in which 13 patients with COPD performed maximal cycle exercise after an IV infusion of DCA (50 mg/kg body mass) or saline solution (placebo). Venous blood was sampled before exercise, and immediately, 30 min, and 2 h after exercise. Urine samples were obtained before and 2 h after exercise. Peak workload improved significantly after DCA infusion compared to placebo (10%; p < 0.01). Urinary uric acid levels after exercise were significantly lower in the DCA condition than in the placebo condition, whereas no significant difference was observed for urinary malondialdehyde levels. Oxidized glutathione (GSSG) levels were significantly increased 2 h after exercise in the placebo condition (p < 0.02) but not after DCA infusion. No changes in reduced glutathione (GSH), GSSG/GSH ratio, and superoxide dismutase activity were observed. Plasma interleukin (IL)-6 levels significantly increased 2 h after exercise only in the DCA condition (p < 0.01). This study shows that improved performance after a pharmacologic intervention known to activate PDC was accompanied by an enhanced IL-6 response and a limited reduction in exercise-induced systemic oxidative stress.

High cardiorespiratory fitness is an independent predictor of the reduction in liver fat during a lifestyle intervention in non-alcoholic fatty liver disease

Objective:Lifestyle intervention with diet modification and increase in physical activity is effective for reducing hepatic steatosis in patients with non-alcoholic fatty liver disease (NAFLD). However, for a similar weight loss,...

Postexercise reduction in lung diffusion capacity is not attenuated by skin cooling

Pulmonary diffusion capacity for carbon monoxide (DL(CO)) is reduced by approximately 10% 1-6 h after maximal exercise. The mechanisms may be interstitial alveolar oedema and reduced pulmonary capillary blood volume. It was hypothesized that thermal stress following exercise contributes to the reduction in DL(CO), and that skin cooling would attenuate the postexercise reduction in DL(CO). Cutaneous vascular conductance (CVC), mean surface temperature (MST), rectal temperature and DL(CO) were measured before and 90 min after maximal incremental cycle exercise. Thereafter, the subjects were exposed to cold air without eliciting shivering one day and another day served as control. The measurements were repeated 120 min after exercise. Twelve healthy subjects (six male) aged 20-27 years were studied. DL(CO) was reduced by 7.1% (SD = 6.3%, P = 0.003) and 7.6% (SD = 5.3%, P<0.001) 90 and 120 min after exercise in the control experiment. It was reduced by 5.6% (SD = 5.5%, P = 0.014) 90 min after exercise and remained reduced by 6.1% (SD = 6.1%, P = 0.012) after cooling despite a significant reduction in CVC and in MST from 31.9 (SD = 0.6) degrees C to 27.4 (SD = 1.9) degrees C. We conclude that the postexercise reduction in DL(CO) is present when thermal status is restored after exercise, and that it is not influenced by further skin surface cooling.

Post-exercise heart rate recovery in healthy, obeses, and COPD subjects: relationships with blood lactic acid and PaO2 levels

Because blood acidosis and arterial oxygenation (PaO(2)) play key roles in the chemoreflex control of cardiac activity, we hypothesized that heart rate (HR) decay rate after maximal exercise may be linked to post-exercise increase in blood lactate (LA) level and/or the resting PaO(2). Twenty healthy subjects and thirty five patients at risks of cardiovascular diseases (20 obeses; 15 patients with chronic obstructive pulmonary disease, COPD) performed a maximal cycling exercise. During the recovery period, HR was continuously measured for consecutive 10-s epochs allowing to compute linear or second order polynomial equations and to calculate every minute HR variations compared to peak HR value (DeltaHR). PaO(2) was measured at rest and post-exercise maximal LA level was determined. A second order polynomial equation (y = a(2) x (2) + b(2) x + c) best fitted the post-exercise HR decay rate. The a(2) and b(2) coefficients and DeltaHR did not depend on age, sex, and body mass index. Despite a large scattering of HR decay rate, even present in healthy subjects, a(2) and DeltaHR were significantly lower in obeses and COPDs. In the whole population, both a(2) coefficient and DeltaHR were negatively correlated with maximal post-exercise LA level. DeltaHR was lowered in hypoxemic patients. Thus, the slowest post-exercise HR decay rate was measured in subjects having the highest peak LA increase or hypoxemia. Thus, even in healthy subjects, the post-exercise HR decay rate is lowered in individuals having an accentuated exercise-induced LA increase and/or hypoxemia. The mechanisms of delayed post-exercise HR recovery are only suspected because significant correlations cannot assess cause-to-effect relationships.

Cardiovascular Fitness in Hong Kong Population

The WHO recommends adults to participate moderate intensity exercise on most days of the week in order to maintain health. Physical inactivity results in deterioration of aerobic and metabolic fitness, weight gain; increase risk of type 2 diabetes, cardiovascular disease and premature mortality. PURPOSE: To investigate the relationship between cardiovascular fitness and physical inactivity in a Hong Kong population. METHODS: Four hundred and seventeen (196 male and 221 female) Hong Kong Chinese (age from 20 to 64 years) participated in this study during 2003 to 2004. All subjects were community-dwelling, ambulatory and had no major medical problems. A maximal bicycle exercise test was performed to assess VO2max. Pair wise comparison Fisher's LSD test was applied as post hoc to see change of cardiovascular fitness between age groups. The result was correlated with a report which used IPAQ to investigate physical activities and exercise levels of Hong Kong population (6370 subjects) in the same period of time. International Physical Activity Questionnaire (IPAQ) was used to describe the physical activity level. RESULTS: VO2max reduced from 29.6 to 18.4 ml/kg/min (P<0.001) in the females from the younger to the older age group. The corresponding values for the males were 39.9 and 26.0 ml/kg/min (p<0.01). Of note is the very low aerobic fitness level for all young female not the least in the light of most of them having a low BMI (range 20 - 23). The lower cardiovascular fitness reflected a low level of physical activity among the females with less involvement in vigorous (5.8% vs. 12.9%) and moderate (20.3% vs. 23.8%) physical activity compared with males. The youngest groups of female showed the highest % of physical inactivity. CONCLUSIONS: An alarming number of young female in Hong Kong have very low aerobic fitness level which is not linked with overweight or obesity. People in Hong Kong especially young female are all recommended to increase their physical activity and thereby their fitness to reduce the risk of early development of chronic disease leading to premature death.

Cardiorespiratory Fitness as a Feature of Metabolic Syndrome in Older Men and Women

OBJECTIVE—We studied the associations of cardiorespiratory fitness with metabolic syndrome in older men and women, because such data are limited in representative population samples. RESEARCH DESIGN AND METHODS—We studied a population sample of 671 men and 676 women aged 57–79 years at baseline of a randomized controlled intervention study. We assessed maximal oxygen uptake (Vo2max) by respiratory gas analysis during a maximal bicycle exercise test. RESULTS—Vo2max had a strong, inverse, and graded association with the risk of having metabolic syndrome as defined by the National Cholesterol Education Program criteria. Men and women in the lowest third of Vo2max had 10.2- and 10.8-fold higher risks and those in the middle third had 2.9- and 4.7-fold higher risks (P &amp;lt; 0.001 all) of metabolic syndrome than those with the highest Vo2max after multivariable adjustments. Factor analysis generated a principal factor that was strongly loaded by the main components of metabolic syndrome and Vo2max (−0.68 in men and −0.70 in women). CONCLUSIONS—Low cardiorespiratory fitness is associated with metabolic syndrome in older men and women. Our findings suggest that low cardiorespiratory fitness could be considered a feature of metabolic syndrome.

Dichloroacetate Enhances Performance and Reduces Blood Lactate during Maximal Cycle Exercise in Chronic Obstructive Pulmonary Disease

Impaired skeletal muscle function contributes to exercise limitation in patients with chronic obstructive pulmonary disease (COPD). This is characterized by reduced mitochondrial adenosine triphosphate generation, and greater reliance on nonmitochondrial energy production. Dichloroacetate (DCA) infusion activates muscle pyruvate dehydrogenase complex (PDC) at rest, reducing inertia in mitochondrial energy delivery at the onset of exercise and diminishing anaerobic energy production. This study aimed to determine whether DCA infusion enhanced mitochondrial energy delivery during symptom-limited maximal exercise, thereby reducing exercise-induced lactate and ammonia accumulation and, consequently, improving exercise performance in patients with COPD. A randomized, double-blind crossover design was used. Eighteen subjects with COPD performed maximal cycle exercise after an intravenous infusion of DCA (50 mg/kg body mass) or saline (control). Exercise work output was determined, and blood lactate and ammonia concentrations were measured at rest, 1 and 2 minutes of exercise, peak exercise, and 2 minutes postexercise. DCA infusion reduced peak blood lactate concentration by 20% (mean [SE]; difference, 0.48 [0.11] mmol/L, P < 0.001) and peak blood ammonia concentration by 15% (mean [SE]; difference, 14.2 [2.9] mumol/L, P < 0.001] compared with control. After DCA, peak exercise workload improved significantly by a mean (SE) of 8 (1) W (P < 0.001) and peak oxygen consumption by 1.2 (0.5) ml/kg/minute (P = 0.03) compared with control. We have shown that a pharmacologic intervention known to activate muscle PDC can reduce blood lactate and ammonia accumulation during exercise and improve maximal exercise performance in subjects with COPD. Skeletal muscle PDC activation may be a target for pharmacologic intervention in the management of exercise intolerance in COPD.