Central and peripheral hemodynamics during maximal leg extension exercise

Summary The purpose of this study was to examine the central and peripheral hemodynamic adaptations to maximal leg extension exercise. Seventeen men (¯X=25 years, 84 kg) performed leg extension exercise (Universal equipment) for 12 repetitions (90s) to fatigue. Each repetition consisted of a 3s lifting motion, 1s pause, and 3s lowering motion. Impedance cardiography was used to measure stroke volume (SV), cardiac output ( ), systolic time intervals, and impedance contractility indices on a beat-by-beat basis. There were significant increases in systolic, diastolic, mean arterial pressure, total peripheral resistance, and HR during exercise. The mean remained similar throughout the protocol. SV decreased even though indices of myocardial performance indicated an enhancement of contractility. The magnitude of and SV were dependent upon the phase of leg extension. SV and during the lifting portions of the exercise were smaller than the lowering portions. The differences in SV and during the concentric and eccentric phases of the exercise most likely reflect the large static forces in exercising muscle which impeded venous return and increased afterload.     

The relationship of pulmonary vascular resistance and compliance to pulmonary artery wedge pressure during submaximal exercise in healthy older adults

Key points

• A consistent inverse hyperbolic relationship has been observed between pulmonary vascular resistance and compliance, although changes in pulmonary artery wedge pressure (PAWP) may modify this relationship.
• This relationship predicts that pulmonary artery systolic, diastolic and mean pressure maintain a consistent relationship relative to the PAWP.
• We show that, in healthy exercising human adults, both pulmonary vascular resistance and compliance decrease in relation to exercise‐associated increases in PAWP.
• Pulmonary artery systolic, diastolic and mean pressures maintain a consistent relationship with one another, increasing linearly with increasing PAWP.
• Increases in PAWP in the setting of exercise are directly related to a decrease in pulmonary vascular compliance, despite small decreases in pulmonary vascular resistance, thereby increasing the pulsatile afterload to the right ventricle.

Abstract

The resistive and pulsatile components of right ventricular afterload (pulmonary vascular resistance, Rp; compliance, Cp) are related by an inverse hyperbolic function, expressed as their product known as RpCp‐time. The RpCp‐time exhibits a narrow range, although it may be altered by the pulmonary artery wedge pressure (PAWP). Identifying the determinants of RpCp‐time should improve our understanding of the physiological behaviour of pulmonary arterial systolic (PASP), diastolic (PADP) and mean (mPAP) pressures in response to perturbations. We examined the effect of exercise in 28 healthy non‐athletic adults (55 ± 6 years) who underwent right heart catheterization to assess haemodynamics and calculate Rp and Cp. Measurements were made at rest and during two consecutive 8–10 min stages of cycle ergometry, at targeted heart‐rates of 100 beats min^–1 (Light) and 120 beats min^–1 (Moderate). Cardiac output increased progressively during exercise. PASP, PADP, mPAP and PAWP increased for Light exercise, without any further rise for Moderate exercise. RpCp‐time decreased for Light exercise (0.39 ± 0.08 to 0.25 ± 0.08, P < 0.001) without any further change for Moderate exercise, and the decrease in RpCp‐time was related to changes in PAWP (r ² = 0.26, P < 0.001). Changes in PASP (r ² = 0.43, P < 0.001), PADP (r ² = 0.47, P < 0.001) and mPAP (r ² = 0.50, P < 0.001) were linearly correlated with changes in PAWP, although they were not significantly related to changes in cardiac output. In healthy adults, exercise is associated with decreases in Cp and a resultant decline in RpCp‐time, indicating increased pulsatile right ventricular afterload. Changes in RpCp‐time, PASP, PADP and mPAP were systematically related to increases in PAWP.     

The effect of prolonged submaximal exercise on gas exchange kinetics and ventilation during heavy exercise in humans

This study compared ventilation, gas exchange (oxygen uptake, V̇O₂) and the surface electromyogram (EMG) activity of four major lower limb muscles during heavy exercise before (Pre-Ex) and after (Post-Ex) a sustained 90-min cycling exercise at 60% V̇O_2peak. The 90-min exercise was incorporated under the hypothesis that sustained exercise would alter substrate availability in the second exercise bout causing differences in fibre recruitment patterns, gas exchange and ventilation. Nine trained male subjects [V̇O_2peak=60.2 (1.7) ml·kg⁻¹·min⁻¹] completed two identical 6-min bouts of cycling performed at high intensity [~90% V̇O_2peak; 307 (6) W, mean (SE)]. Ventilation and gas exchange were measured breath-by-breath and the EMG was recorded during the last 12 s of each minute of the two 6-min bouts. EMG signals were analysed to determine integrated EMG (iEMG) and mean power frequency (MPF). V̇O₂ at min 3 and min 6 in Post-Ex were significantly higher (i.e., +201 and 141 ml·min⁻¹, respectively, P<0.05) than in Pre-Ex but there was a ~25% decrease of the slow component, taken as the difference between min 6 and min 3 [187 (27) vs 249 (35) ml·min⁻¹, respectively, P<0.05]. The greater whole-body V̇O₂ after 3 min of exercise in Post-Ex was not accompanied by clear alterations in the iEMG and MPF of the examined leg muscles. Ventilation and heart rate were elevated (~12–16 l·min⁻¹ and ~10 beats·min⁻¹, respectively, P<0.05) as were the ratios V̇ _E/O₂ and V̇ _E/V̇CO₂ in the Post-Ex tests. It was concluded that the V̇O₂ and ventilation responses to high-intensity exercise can be altered following prolonged moderate intensity exercise in terms of increased amplitude without associated major changes in either iEMG or MPF values among conditions.     

Sex-specific regulation of aging and apoptosis

Genetic analysis of Drosophila, mice and humans indicates that gene alleles, mutations and transgenes that affect life span tend to do so differently depending on the sex of the organism. The likely reason for this is that the sexes are different genotypes (e.g., X/X vs. X/Y) and face quite different environments: e.g., to reproduce, males have to mate with females while females have to mate with males. Genes are subject to different genetic interactions and different gene-by-environment effects in male vs. female. The consequence is that through evolution certain genes are differently selected and optimized for each sex. Both the mitochondrial genome and the X chromosome are asymmetrically inherited in Drosophila and mammals; through evolution these genes spend relatively more time under selection in females and are therefore expected to be better optimized for function in the female than in the male. Consistent with this the Drosophila X chromosome has been found to be a hotspot for sexually antagonistic fitness variation. Old Drosophila and old mammals exhibit apoptosis-an observation consistent with the idea that the mitochondria are less functional during aging due to maternal-only inheritance. One feature of aging that is common to Drosophila and mammals is that females tend to live longer than males, and this may be due in part to sub-optimal mitochondrial function in males. The data support the conclusion that a significant part of the aging phenotype is due to antagonistic pleiotropy of gene function between the sexes. Liberal application of Occam's razor yields a molecular model for the co-regulation of sex, apoptosis and life span based on the on/off status of a single gene: Sxl in Drosophila melanogaster and Xist in humans. Aging may simply represent an ancient and conserved mechanism by which genes re-assort.     

Self-efficacy and the maintenance of exercise participation in older adults

The role played by exercise self-efficacy in the maintenance of exercise participation of previously sedentary middle-aged adults 4 months after the termination of a formal exercise program is reported. Correlational and multiple regression analyses examined the influence of self-efficacy, physiological (aerobic capacity, sex, body composition), and behavioral (past exercise frequency and intensity) parameters in the maintenance of exercise participation. Self-efficacy significantly predicted exercise behavior at follow-up when controlling for biological and behavioral influences. Aerobic capacity, exercise efficacy, and exercise behavior in combination were significantly related to current energy expenditure in aerobic physical activity. The discussion focuses on the need to examine the impact of different correlates of exercise behavior at different stages of the exercise process.This project was funded by Grant AG07907 from the National Institute on Aging.     

Vascular health and longitudinal changes in brain and cognition in middle-aged and older adults

The impact of vascular health on the relations between structural brain changes and cognition was assessed in a longitudinal study of 46 adults, 23 of whom remained healthy for 5 years and 23 of whom had hypertension at baseline or acquired vascular problems during follow-up. At both measurement occasions, the volume of white matter hyperintensities (WMH) and regional brain volumes correlated with age. In 5 years, WMH volume more than doubled in the vascular risk group but did not increase in healthy participants. The frontal lobes had the highest WMH load at baseline and follow-up; the parietal WMH showed the greatest rate of expansion. In the vascular risk group, systolic blood pressure at follow-up correlated with posterior WMH volume. The fastest cortical shrinkage was observed in the prefrontal cortex and the hippocampus. Fluid intelligence correlated with WMH burden and declined along with faster WMH progression. In the vascular risk group, WMH progression and shrinkage of the fusiform cortex correlated with decline in working memory. Thus, poor vascular health contributes to age-related declines in brain and cognition, and some of the age-related declines may be limited to persons with elevated vascular risk.     

Oxygen deficit and repayment in submaximal exercise

Oxygen deficit and repayment ratios were investigated at various work loads, intensities and durations. An active baseline was used (walking at 60 m/min) from which deficit and repayment values were calculated. Oxygen uptake (VO₂) and core temperatures were measured in 30 males at baseline and during treadmill running (140 m/min) for randomly assigned durations (0.5 ... 20 min). Measurements were also made during a 30-min recovery period at baseline work. Results indicated: 1) No difference in O₂-repayment between steady-state work and work prior to steady-state (P>0.10). 2) O₂-repayment was independent of work duration (P>0.10). 3) When workload and intensity were controlled, O₂-deficit was not a significant factor in O₂-repayment (P>0.10). 4) Work intensity (workVO₂/VO₂max) was the most significant factor in O₂-repayment accounting for 69% of the variance (r = 0.83,P<0.001). Small increments in core temperature and ventilation were not significant factors in O₂-repayment. When a working baseline is used, the magnitude of O₂-repayment after exercise is independent of the work duration or the attainment of steady state. The extent of O₂-repayment after exercise is mainly dependent upon the physiological intensity of the work and the absolute workload (R = 0.89,P<0.001).     

Prolonged submaximal exercise and L-carnitine in humans

Summary Changes in the main physiological parameters and circulating indicators of carbohydrate, protein, lipid (and ketone body) metabolism were measured in ten exercising subjects before L-carnitine (L-carn) loading, after 4 weeks of daily loading with 2 g L-carn, and 6–8 weeks after terminating L-carn administration. Measurements were made on venous blood samples collected during each experiment at fixed time intervals over an initial rest of 45 min, 60 min bicycle exercise performed near 50% and 120 min recovery. Free and total plasma carnitine levels reached a plateau corresponding to an average rise of 25% for both fractions, 9–10 days after the beginning of the L-carn diet. These levels returned to their initial values 6–8 weeks after cessation of the supply. Generally L-carn supplementation did not significantly modify the physiological parameters and circulating metabolites. No distinct increase of the relative participation of endogenous lipids in the fuel supply of prolonged submaximal exercise was observed. In normal human subjects the increased demand for fatty acid oxidation resulting from exercise seems to be adequately supported by endogenous levels of carnitine.     

Effects of habitual moderate exercise on response processing and cognitive processing in older adults

We examined the effects of habitual moderate exercise on central information processing in older individuals using the reaction time (RT) and P3 component of event-related brain potentials (ERP). The present study was designed to assess cognitive function by comparing groups of 20 older individuals (69.20 +/- 1.3 years active group) who regularly engage in moderate physical activity with 20 subjects (66.90 +/- 1.1 years inactive group) who do comparatively little exercise. Subjects performed a somatosensory oddball task composed of pressing a button with their right foot as fast as possible following an electrical stimulus applied to the right index finger, and not responding to an electrical stimulus applied to the left index finger. Electroencephalogram (EEG) was recorded at the frontal (Fz), central (Cz), and parietal (Pz) sites according to the International 10-20 system referenced to linked earlobes. The RT was faster for the active group than for the inactive group, and the P3 amplitude of the active group was significantly larger than that of the inactive group. Moreover, the P3 amplitude for the active group was maximum at Pz and significantly larger than at Fz and Cz, but for the inactive group it was identical between Fz and Pz. The results suggest that habitual moderate exercise exerts positive influences in older adults not only on response processing, but also on cognitive processing.     

Effect of concurrent aerobic and resistance circuit exercise training on fitness in older adults

The purpose of this study was to determine the physiological effects of a programmed accommodating circuit exercise (PACE) program consisting of aerobic exercise and hydraulic-resistance exercise (HRE) on fitness in older adults. Thirty-five volunteers were randomly divided into two groups [PACE group (PG) 8 men and 10 women, 68.3 (4.9) years, and non-exercise control group (CG) 7 men and 10 women, 68.0 (3.4) years). The PG participated in a 12-week, 3 days per week supervised program consisting of 10 min warm-up and 30 min of PACE (moderate intensity HRE and aerobic movements at 70% of peak heart rate) followed by 10 min cool-down exercise. PACE increased (P<0.05) oxygen uptake (O₂) at lactate threshold [PG, pre 0.79 (0.20) l min^–1, post 1.02 (0.22) l min^–1, 29%; CG, pre 0.87 (0.14) l min^–1, post 0.85 (0.15) l min^–1, –2%] and at peak O₂ [PG, pre 1.36 (0.24) l min^–1, post 1.56 (0.28) l min^–1, 15%; CG, pre 1.32 (0.29) l min^–1, post 1.37 (0.37) l min^–1, 4%] in PG measured using an incremental cycle ergometer. Muscular strength evaluated by a HRE machine increased at low to high resistance dial settings for knee extension (9–52%), knee flexion (14–76%), back extension (18–92%) and flexion (50–70%), chest pull (6–28%) and press (3–17%), shoulder press (18–31%) and pull (26–85%), and leg press (21%). Body fat (sum of three skinfolds) decreased (16%), and high-density lipoprotein cholesterol (HDLC) increased (10.9 mg dl^–1) for PG. There were no changes in any variables for CG. These results indicate that PACE training incorporating aerobic exercise and HRE elicits significant improvements in cardiorespiratory fitness, muscular strength, body composition, and HDLC for older adults. Therefore, PACE training is an effective well-rounded exercise program that can be utilized as a means to improve health-related components of fitness in older adults.     

Acute moderate exercise enhances compensatory brain activation in older adults

A growing number of reports state that regular exercise enhances brain function in older adults. Recently a functional near-infrared spectroscopy (fNIRS) study revealed that an acute bout of moderate exercise enhanced activation of the left dorsolateral prefrontal cortex (L-DLPFC) associated with Stroop interference in young adults. Whether this acute effect is also applicable to older adults was examined. Sixteen older adults performed a color-word matching Stroop task before and after 10 minutes of exercise on a cycle ergometer at a moderate intensity. Cortical hemodynamics of the prefrontal area was monitored with a fNIRS during the Stroop task. We analyzed Stroop interference (incongruent-neutral) as Stroop performance. Though activation for Stroop interference was found in the bilateral prefrontal area before the acute bout of exercise, activation of the right frontopolar area (R-FPA) was enhanced after exercise. In the majority of participants, this coincided with improved performance reflected in Stroop interference results. Thus, an acute bout of moderate exercise improved Stroop performance in older adults, and this was associated with contralateral compensatory activation.     

Functional mobility of older adults after concentric and eccentric endurance exercise

Age-associated decline in muscle mass and strength impairs functional mobility in older adults. We examined the effects of an eccentric endurance exercise programme (downhill treadmill walking, DTW) at a self-selected walking speed (SSWS) on functional mobility and eccentric and concentric strength of m. quadriceps femoris of older adults. Twenty-four older adults (67?±?4?years) were randomly assigned to complete 3?×?30?min treadmill walks per week for 12?weeks on a level (n?=?11, LTW 0%) or downhill (n?=?13, DTW -10%) treadmill gradient at SSWS. SSWS was re-adjusted every 4?weeks. Participants were assessed for five repetition sit-to-stand (5-RSTS), maximal walking speed (MWS), timed up-and-go (TUG) and dynamic strength. SSWS was similar for both groups with increases from 1.18?±?0.11 to 1.53?±?0.09?m?s(-1) (LTW) and 1.26?±?0.16 to 1.61?±?0.12?m?s(-1) (DTW) (time, P?相似文献   

The role of efficacy cognitions in the prediction of exercise behavior in middle-aged adults

The present study adopted a social cognitive framework to examine the role played by perceptions of personal efficacy in adherence to exercise behavior in sedentary middle-aged adults. Subjects were followed for 5 months in order to study the process of exercise as it moved through the adoption to maintenance stage of the behavior. Participation rates paralleled those reported elsewhere in the literature. Path analytic techniques examined the role over time of efficacy, perceptual, and behavioral indicators of frequency and intensity of exercise. Self-efficacy cognitions were shown to predict adoption of exercise behavior but previous behavior proved to be the strongest predictor of subsequent exercise participation. Results are discussed in terms of examining process versus static design models in exercise and physical activity research. Implications for future research and health promotion are suggested.Funding for this research was provided by Public Health Service Grant AG07907 from the National Institute on aging.