Decline in VO2max with aging in master athletes and sedentary men

Fifteen well-trained master endurance athletes [62.0 +/- 2.3 (SE) yr] and 14 sedentary control subjects (61.4 +/- 1.4 yr) were reevaluated after an average follow-up period of approximately 8 yr to obtain information regarding the effects of physical activity on the age-related decline in maximal O2 uptake capacity (VO2max). The master athletes had been training for 10.2 +/- 2.9 yr before initial testing and continued to train during the follow-up period. The sedentary subjects' VO2max declined by an average of 3.3 ml.kg-1.min-1 (33.9 +/- 1.7 vs. 30.6 +/- 1.6, P less than 0.001) over the course of the study, a decline of 12% per decade. In these subjects maximal heart rate declined 8 beats/min (171 vs. 163) and maximal O2 pulse decreased from 0.20 to 0.18 ml.kg-1.beat (P less than 0.05). The master athletes' VO2 max decreased by an average of 2.2 ml.kg-1.min-1 (54.0 +/- 1.7 vs. 51.8 +/- 1.8, P less than 0.05), a 5.5% decline per decade. The master athletes' maximal heart rate was unchanged (171 +/- 3 beats/min) and their maximal O2 pulse decreased from 0.32 to 0.30 ml.kg-1.beat (P less than 0.05). These findings provide evidence that the age-related decrease in VO2max of master athletes who continue to engage in regular vigorous endurance exercise training is approximately one-half the rate of decline seen in age-matched sedentary subjects. Furthermore our results suggest that endurance exercise training may reduce the rate of decline in maximal heart rate that typically occurs as an individual ages.     

Strength training and determinants of VO2max in older men

The effects of strength training on maximal aerobic power (VO2max) and some of its determinants were studied in 12 healthy older men (60-72 yr). They underwent 12 wk of strength conditioning of extensors and flexors of each knee with eight repetitions per set, three sets per session, and three sessions per week at 80% of the one repetition maximum (1 RM). Left knee extensors showed a 107% increase in 1 RM, a 10% increase in isokinetic strength at 60 degrees/s, and a 23% increase in total work performed during 25 contractions on an isokinetic dynamometer. Strength measurements of the untrained left elbow extensors showed no change. Leg cycle ergometer VO2max per unit fat-free mass increased by an average 1.9 ml (P = 0.034) whereas arm cycle VO2max was unchanged. Pulmonary function, hemoglobin concentration, erythrocyte volume, plasma volume, and total blood volume did not change. Biopsies of the vastus lateralis showed a 28% increase in mean fiber area, no change in fiber type distribution, a 15% increase in capillaries per fiber, and a 38% increase in citrate synthase activity. The data suggest that the small increase in leg cycle VO2max in older men may be due to adaptations in oxidative capacity and increased mass of the strength-trained muscles.     

Markers of inflammation are inversely associated with VO2 max in asymptomatic men.

We investigated whether markers of inflammation, including a cytokine (IL-6), acute-phase reactants [C-reactive protein (CRP) and fibrinogen], and white blood cell (WBC) count are associated with maximal O(2) consumption (Vo(2 max)) in men without coronary heart disease (CHD). In asymptomatic men (n = 172, 51 +/- 9.3 yr old), Vo(2 max) was measured during a symptom-limited graded treadmill exercise test. Physical activity level was assessed by a standardized questionnaire. IL-6 and CRP were measured by immunoassays, fibrinogen by the Clauss method, and WBC count with a Coulter counter. IL-6 and CRP were logarithmically transformed to reduce skewness. Multivariable regression was used to assess whether markers of inflammation were associated with Vo(2 max) after adjustment for age, body mass index, CHD risk factors, and lifestyle variables (physical activity level, percent body fat, and alcohol intake). Vo(2 max) was 34.5 ml.kg(-1).min(-1) (SD 6.1). Log IL-6 (r = -0.38, P < 0.001), log CRP (r = -0.40, P < 0.001), fibrinogen (r = -0.42, P < 0.001), and WBC count (r = -0.22, P = 0.004) were each correlated with Vo(2 max). In separate multivariable linear regression models that adjusted for age, body mass index, CHD risk factors, and lifestyle variables, log IL-6 [beta-coeff = -1.66 +/- 0.63 (SE), P = 0.010], log CRP [beta-coeff = -0.99 +/- 0.33 (SE), P = 0.003], fibrinogen [beta-coeff = -1.51 +/- 0.44 (SE), P = 0.001], and WBC count [beta-coeff = -0.52 +/- 0.30 (SE), P = 0.088] were each inversely associated with Vo(2 max). In conclusion, higher circulating levels of IL-6, CRP, and fibrinogen are independently associated with lower Vo(2 max) in asymptomatic men.     

Investigation of serum leptin levels and VO2max value in trained young male athletes and healthy males

The present study aimed at investigating serum leptin levels of elite young male athletes who have been regularly exercising for a long period of time and males who do not exercise. The study included 24 trained young male athletes and 22 healthy sedentary male subjects. Athletes who participated in the study were from different sports branches and have been regularly exercising for at least 2 years. Serum leptin levels were determined by RIA. VO2max levels were identified during maximal exercise. Lactic acid levels were identified one minute before and one minute after exercise from the fingertip by Pro-lactate kit. As a result of the tests, although BMI values of trained young male athletes and healthy males were close to each other, leptin levels were significantly lower (p<0.01), VO2max values were significantly higher (p<0.01) and test periods were significantly longer (p<0.001) in the former. In conclusion, regular exercise, by reducing body fat percentage, suppresses serum leptin levels.     

Muscle respiratory capacity and VO2 max in identically trained young and old rats

Old rats have a decreased hindlimb muscle respiratory capacity and whole-body maximal O2 consumption (VO2 max). The decline in spontaneous physical activity in old rats might contribute to these age-related changes. The magnitude of the age-related decline is not uniform in all skeletal muscle respiratory enzymes, and the decrease in palmitate oxidation is particularly great. This study was designed to determine if young and old rats subjected to the same exercise-training protocol would attain similar values for VO2 max and several markers of muscle respiratory capacity. Four- and 18-mo-old Fischer 344 rats underwent an identical 6-mo program of treadmill running. After training, both age groups had increased VO2 max above sedentary age-matched controls. However, the old trained rats had a lower VO2 max than identically trained young rats. In contrast to VO2 max, the two trained groups attained similar values for gastrocnemius citrate synthase, cytochrome oxidase, 3-hydroxyacyl-CoA dehydrogenase, palmitate oxidation, and total carnitine concentration. Thus, when the young and old rats performed an identical exercise protocol within the capacity of the old animals, differences in skeletal muscle respiratory capacity were eliminated. The dissimilarity in VO2 max between the identically trained groups was apparently caused by age-related differences in factors other than muscle respiratory capacity.     

Intensity-controlled treadmill running in rats: VO(2 max) and cardiac hypertrophy

Physiological studies of long-term cardiovascular adaptation to exercise require training regimens that give robust conditioning effects and adequate testing procedures to quantify the outcome. We developed a valid and reproducible protocol for measuring maximal oxygen uptake (VO(2 max)), which was reached at a 25 degrees inclination with a respiratory exchange ratio > 1.05 and blood lactate > 6 mmol/l. The effect of intensity-controlled aerobic endurance training was studied in adult female and male rats that ran 2 h/day, 5 days/wk, in intervals of 8 min at 85-90% of VO(2 max) and 2 min at 50-60% of VO(2 max), with adjustment of exercise level according to VO(2 max) every week. After 7 wk, the increase in VO(2 max) plateaued at 60-70% above sedentary controls. Ventricular weights and myocyte length were up 25-30% and 6-12%, respectively. Work economy, oxygen pulse, and heart rate were sufficiently changed to indicate substantial cardiovascular adaptation. The model mimics important human responses to training and could be used in future studies on cellular, molecular, and integrative mechanisms of improved cardiovascular function.     

Exercise-induced splanchnic hypoperfusion results in gut dysfunction in healthy men

Background

Splanchnic hypoperfusion is common in various pathophysiological conditions and often considered to lead to gut dysfunction. While it is known that physiological situations such as physical exercise also result in splanchnic hypoperfusion, the consequences of flow redistribution at the expense of abdominal organs remained to be determined. This study focuses on the effects of splanchnic hypoperfusion on the gut, and the relationship between hypoperfusion, intestinal injury and permeability during physical exercise in healthy men.

Methods and Findings

Healthy men cycled for 60 minutes at 70% of maximum workload capacity. Splanchnic hypoperfusion was assessed using gastric tonometry. Blood, sampled every 10 minutes, was analyzed for enterocyte damage parameters (intestinal fatty acid binding protein (I-FABP) and ileal bile acid binding protein (I-BABP)). Changes in intestinal permeability were assessed using sugar probes. Furthermore, liver and renal parameters were assessed. Splanchnic perfusion rapidly decreased during exercise, reflected by increased gap_g-apCO₂ from −0.85±0.15 to 0.85±0.42 kPa (p<0.001). Hypoperfusion increased plasma I-FABP (615±118 vs. 309±46 pg/ml, p<0.001) and I-BABP (14.30±2.20 vs. 5.06±1.27 ng/ml, p<0.001), and hypoperfusion correlated significantly with this small intestinal damage (r_S = 0.59; p<0.001). Last of all, plasma analysis revealed an increase in small intestinal permeability after exercise (p<0.001), which correlated with intestinal injury (r_S = 0.50; p<0.001). Liver parameters, but not renal parameters were elevated.

Conclusions

Exercise-induced splanchnic hypoperfusion results in quantifiable small intestinal injury. Importantly, the extent of intestinal injury correlates with transiently increased small intestinal permeability, indicating gut barrier dysfunction in healthy individuals. These physiological observations increase our knowledge of splanchnic hypoperfusion sequelae, and may help to understand and prevent these phenomena in patients.     

Cold exposure increases running VO(2max) and cost of transport in goats

We inadvertently subjected a group of goats to 5 mo of cold exposure (mean minimum temperature less than -13 degrees C) during an experiment designed to examine the effects of training by daily running on one member of each sibling pair. During the three coldest months, the sedentary but cold-exposed goats experienced a 34% increase in maximal oxygen uptake (VO(2 max), P < 0.01) and a 29% increase in running speed at maximal (P < 0.05). When temperatures increased in the spring, both oxygen uptake and running speed decreased. We interpret these findings as evidence that cold is a sufficient stimulus to invoke the development of aerobic structures in muscle and that these structures subsequently can be utilized for the novel task of running. When the experiment was subsequently repeated without the cold exposure, running speed and VO(2 max) of trained animals increased less than in either group of cold-exposed animals. However, the cost of transport of these warm runners was lower than either group of cold-exposed animals (from 13-19%, P < 0. 0001). Thus, although aerobic capacity was increased with acclimation to severe winter weather, cold-acclimated goats operated with lower efficiency during locomotion.     

Crossvalidation of two heart rate-based equations for predicting VO2max in white and black men

The purpose of this investigation was to crossvalidate 2 equations that use the ratio of maximal heart rate (HRmax) to resting HR (HRrest) for predicting maximal oxygen consumption (VO2max) in white and black men. One hundred and nine white (n = 51) and black (n = 58) men completed a maximal exercise test on a treadmill to determine VO2max. The HRrest and HRmax were used to predict VO2max via the HRindex and HRratio equations. Validity statistics were done to compare the criterion versus predicted VO2max values across the entire cohort and within each race separately. For the entire group, VO2max was significantly overestimated with the HRindex equation, but the HRratio equation yielded no significant difference compared with the criterion. In addition, there were no significant differences shown between VO2max and either HR-based prediction equation for the white subgroup. However, both equations significantly overestimated VO2max in the black group. Furthermore, large standard error of estimates (ranging from 6.92 to 7.90 ml·kg(-1)·min(-1)), total errors (ranging from 8.30 to 8.62 ml·kg(-1)·min(-1)), and limits of agreement (ranging from upper limits of 16.65 to lower limits of -18.25 ml·kg(-1)·min(-1)) were revealed when comparing the predicted to criterion VO2max for both the groups. Considering the results of this investigation, the HRratio and HRindex methods appear to crossvalidate and prove useful for estimating the mean VO2max in white men as a group but not for an age-matched group of black men. However, because of inflated values for error, caution should be exercised when using these methods to predict individual VO2max.     

VO2 max is associated with ACE genotype in postmenopausal women

Relationships have frequently been found betweenangiotensin-converting enzyme (ACE) genotype and various pathologicaland physiological cardiovascular outcomes and functions. Thuswe sought to determine whether ACE genotype affected maximalO₂ consumption (O_{2 max}) and maximalexercise hemodynamics in postmenopausal women with different habitualphysical activity levels. Age, body composition, and habitual physicalactivity levels did not differ among ACE genotype groups. However, ACEinsertion/insertion (II) genotype carriers had a 6.3 ml · kg¹ · min¹higher O_{2 max}(P < 0.05) than the ACEdeletion/deletion (DD) genotype group after accounting for the effectof physical activity levels. The ACE II genotype group also had a 3.3 ml · kg¹ · min¹higher O_{2 max}(P < 0.05) than the ACEinsertion/deletion (ID) genotype group. The ACE ID group tended to havea higher O_{2 max} thanthe DD genotype group, but the difference was not significant. ACEgenotype accounted for 12% of the variation inO_{2 max} among womenafter accounting for the effect of habitual physical activity levels.The entire difference inO_{2 max} among ACEgenotype groups was the result of differences in maximal arteriovenousO₂ difference (a-vDO₂).ACE genotype accounted for 17% of the variation in maximal a-vDO₂ inthese women. Maximal cardiac output index did not differ whatsoeveramong ACE genotype groups. Thus it appears that ACE genotype accountsfor a significant portion of the interindividual differences inO_{2 max} among thesewomen. However, this difference is the result of genotype-dependentdifferences in maximala-vDO₂ andnot of maximal stroke volume and maximal cardiac output.

     

Reproducibility of an incremental treadmill VO(2)max test with gas exchange analysis for runners

The evaluation of performance through the application of adequate physical tests during a sportive season may be a useful tool to evaluate training adaptations and determine training intensities. For runners, treadmill incremental VO(2)max tests with gas exchange analysis have been widely used to determine maximal and submaximal parameters such as the ventilatory threshold (VT) and respiratory compensation point (RCP) running speed. However, these tests often differ in methodological characteristics (e.g., stage duration, grade, and speed increment size), and few studies have examined the reproducibility of their protocol. Therefore, the aim of this study was to verify the reproducibility and determine the running speeds related to maximal and submaximal parameters of a specific incremental maximum effort treadmill protocol for amateur runners. Eleven amateur male runners underwent 4 repetitions of the protocol (25-second stages, each increasing by 0.3 km·h in running speed while the treadmill grade remained fixed at 1%) after 3 minutes of warm-up at 8-8.5 km·h. We found no significant differences in any of the analyzed parameters, including VT, RCP, and VO(2)max during the 4 repetitions (p > 0.05). Further, the results related to running speed showed high within-subject reproducibility (coefficient of variation < 5.2%). The typical error (TE) values for running speed related to VT (TE = 0.62 km·h), RCP (TE = 0.35 km·h), and VO(2)max (TE = 0.43 km·h) indicated high sensitivity and reproducibility of this protocol. We conclude that this VO(2)max protocol facilitates a clear determination of the running speeds related to VT, RCP, and VO(2)max and has the potential to enable the evaluation of small training effects on maximal and submaximal parameters.     

Relationship between angiotensin-converting enzyme ID polymorphism and VO(2max) of Chinese males

Several studies have shown that the angiotensin-converting enzyme (ACE) I allele is associated with enhanced physical performance. We investigated whether this phenomenon is observed in a cohort of 67 Chinese men in Singapore. Angiotensin-converting enzyme ID polymorphism was typed with PCR method and maximal oxygen uptake (VO(2max)) of the DD, ID, and II genotypes was compared. Analysis of covariance revealed that VO(2max) was significantly higher (p<0.05) for the DD genotype (57.86 +/- 3.5 ml.kg.(-1)min(-1)) versus the ID (50.58 +/- 1.80 ml.kg.(-1)min(-1)) or II (50.48 +/- 1.58 ml.kg.(-1) min(-1)) genotype. Our findings suggest that the ACE DD genotype in young adult Chinese males is associated with higher levels of VO(2max).     

Increased thermogenic response to food and fat oxidation in female athletes: relationship with VO(2 max)

The thermogenic response to food (TRF) and substrate oxidation were studied in 12 endurance-trained and 13 untrained female subjects. Energy expenditure and substrate oxidation were calculated by indirect calorimetry before and for 6 h after an oral test meal and after the same meal given intragastrically on a separate occasion. The TRF was calculated after the oral meal, the obligatory component after the intragastric meal (OTRF), and the facultative component from the difference between the two. VO(2 max) was measured on a treadmill and body composition by underwater weighing. The TRF and OTRF were significantly higher in trained than in untrained subjects: 223 +/- 63 vs. 185 +/- 50 kJ/6 h (P < 0.03) and 174 +/- 38 vs. 131 +/- 37 kJ/6 h (P < 0.01) for the TRF and OTRF in trained vs. untrained subjects, respectively. Multiple regression analysis showed that maximum O(2) consumption (VO(2 max)), but not percentage of body fat, was significantly related to OTRF (r =0.68, P < 0.01). Trained subjects had higher fatty acid oxidation than untrained subjects before (0.6 vs. 0.4 mg. kg(-1). min(-1), P < 0.05) and after the oral meal (13 +/- 6 vs. 8 +/- 4 g/6 h P < 0.05). These results demonstrate that 1) TRF is higher in trained than in untrained women; 2) this is due to a higher cost of nutrient digestion, absorption and storage; 3) the difference is related to higher VO(2 max); and 4) fatty acid oxidation is greater in trained women in both the postabsorptive and postprandial states. These observations suggest that endurance training induces metabolic changes that favor leanness.     

Role of prostaglandin E2 (PGE2) on the corticotropin-releasing hormone (CRH)-induced ACTH release in healthy men.

The effect of PGE2 on ACTH and cortisol responses to CRH was studied in 6 healthy men who received CRH i.v. during either saline or PGE2 infusions which were started 60 min. before testing. ACTH and cortisol responses to CRH were greater during PGE2 infusion compared to the control study. The results indicate that PGE2 positively modulates CRH-induced ACTH secretion.     

Oxygen transport to skeletal muscle working at VO(2)max in acute hypoxia: theoretical predictions

The influence of acute hypoxia (30 < or = PaO(2) < or = 100 mmHg) on the values of VO(2)max and parameters of oxygen transport in muscle working at VO(2)max was studied. We investigated muscle working under different values of blood flow F (60 < or = F < or = 120 ml/min per 100 g), blood pH (7.0-7.6), and different diffusion conditions. Investigations were performed on a computer model of O(2) delivery to and O(2) consumption in the working muscle. VO(2)max, PvO(2), pO(2)- and VO(2)-distribution in muscle fiber were calculated. It was shown that the greater the degree of arterial hypoxemia, the lower the muscle VO(2)max and blood pO(2) values. When working at VO(2)max, the average and minimal values of tissue pO(2) depend on PaO(2). The greater the blood flow through muscle, the greater the VO(2)max. However, with an increasing degree of arterial hypoxemia, the effect of F and blood pH on the value of VO(2)max is weakened. The diffusion conditions produced a powerful influence on the VO(2)max value. At reduced PaO(2) they are the most important limiting factors of O(2) supply to muscle working at maximal effort.     

Aging attenuates vascular and metabolic plasticity but does not limit improvement in muscle VO(2) max

The interactions between exercise, vascular and metabolic plasticity, and aging have provided insight into the prevention and restoration of declining whole body and small muscle mass exercise performance known to occur with age. Metabolic and vascular adaptations to normoxic knee-extensor exercise training (1 h 3 times a week for 8 wk) were compared between six sedentary young (20 +/- 1 yr) and six sedentary old (67 +/- 2 yr) subjects. Arterial and venous blood samples, in conjunction with a thermodilution technique facilitated the measurement of quadriceps muscle blood flow and hematologic variables during incremental knee-extensor exercise. Pretraining, young and old subjects attained a similar maximal work rate (WR(max)) (young = 27 +/- 3, old = 24 +/- 4 W) and similar maximal quadriceps O(2) consumption (muscle Vo(2 max)) (young = 0.52 +/- 0.03, old = 0.42 +/- 0.05 l/min), which increased equally in both groups posttraining (WR(max), young = 38 +/- 1, old = 36 +/- 4 W, Muscle Vo(2 max), young = 0.71 +/- 0.1, old = 0.63 +/- 0.1 l/min). Before training, muscle blood flow was approximately 500 ml lower in the old compared with the young throughout incremental knee-extensor exercise. After 8 wk of knee-extensor exercise training, the young reduced muscle blood flow approximately 700 ml/min, elevated arteriovenous O(2) difference approximately 1.3 ml/dl, and increased leg vascular resistance approximately 17 mmHg x ml(-1) x min(-1), whereas the old subjects revealed no training-induced changes in these variables. Together, these findings indicate that after 8 wk of small muscle mass exercise training, young and old subjects of equal initial metabolic capacity have a similar ability to increase quadriceps muscle WR(max) and muscle Vo(2 max), despite an attenuated vascular and/or metabolic adaptation to submaximal exercise in the old.     

Oxygen uptake kinetics in trained athletes differing in VO2max

Previous work has shown that when VO2 kinetics are compared for endurance trained athletes and untrained subjects, the highly trained athletes have a faster response time. However, it remains to be determined whether the more rapid adjustment of VO2 toward steady state in athletes is due to VO2max differences or training adaptation alone. One approach to this problem is to study the time course of VO2 kinetics at the onset of work in athletes who differ in VO2max but have similar training habits. Therefore, the purpose of these experiments was to compare the time course of VO2 kinetics at the onset of exercise in athletes with similar training routines but who differ in VO2max. Ten subjects (VO2max range 50-70 ml . kg-1 . min-1) performed 6-minutes of cycle ergometer exercise at approximately 50% VO2max. Ventilation and gas exchange were monitored by open circuit techniques. The data were modeled with a single component exponential function incorporating a time delay, (TD); delta VO2t = delta VO2ss (1-e-t-TD/tau), where tau is the time constant delta VO2t is the increase in VO2 at time t and delta VO2ss is the steady-rate increment above resting VO2. Kinetic analysis revealed a range of VO2 half times from 21.6 to 36.0 s across subjects with a correlation coefficient of r = -0.80 (p less than 0.05) between VO2max and VO2 half time. These data suggest that in highly trained individuals with similar training habits, those with a higher VO2max achieve a more rapid VO2 adjustment at the onset of work.     

Predicting maximal aerobic capacity (VO2max) from the critical velocity test in female collegiate rowers

The objective of this study was to examine the relationship between the critical velocity (CV) test and maximal oxygen consumption (VO2max) and develop a regression equation to predict VO2max based on the CV test in female collegiate rowers. Thirty-five female (mean ± SD; age, 19.38 ± 1.3 years; height, 170.27 ± 6.07 cm; body mass, 69.58 ± 0.3 1 kg) collegiate rowers performed 2 incremental VO2max tests to volitional exhaustion on a Concept II Model D rowing ergometer to determine VO2max. After a 72-hour rest period, each rower completed 4 time trials at varying distances for the determination of CV and anaerobic rowing capacity (ARC). A positive correlation was observed between CV and absolute VO2max (r = 0.775, p < 0.001) and ARC and absolute VO2max (r = 0.414, p = 0.040). Based on the significant correlation analysis, a linear regression equation was developed to predict the absolute VO2max from CV and ARC (absolute VO2max = 1.579[CV] + 0.008[ARC] - 3.838; standard error of the estimate [SEE] = 0.192 L·min(-1)). Cross validation analyses were performed using an independent sample of 10 rowers. There was no significant difference between the mean predicted VO2max (3.02 L·min(-1)) and the observed VO2max (3.10 L·min(-1)). The constant error, SEE and validity coefficient (r) were 0.076 L·min(-1), 0.144 L·min(-1), and 0.72, respectively. The total error value was 0.155 L·min(-1). The positive relationship between CV, ARC, and VO2max suggests that the CV test may be a practical alternative to measuring the maximal oxygen uptake in the absence of a metabolic cart. Additional studies are needed to validate the regression equation using a larger sample size and different populations (junior- and senior-level female rowers) and to determine the accuracy of the equation in tracking changes after a training intervention.