Reduction In Aerobic Capacity Research Articles

Cardiopulmonary exercise testing in younger patients with persistent dyspnea following acute, outpatient COVID-19 infection.

Studies using cardiopulmonary exercise testing (CPET) to evaluate persistent dyspnea following infection with COVID-19 have focused on older patients with co-morbid diseases who are post-hospitalization. Less attention has been given to younger patients with post-COVID-19 dyspnea treated as outpatients for their acute infection. We sought to determine causes of persistent dyspnea in younger patients recovering from acute COVID-19 infection that did not require hospitalization. We collected data on all post-COVID-19 patients who underwent CPET in our clinic in the calendar year 2021. Data on cardiac function and respiratory response were abstracted, and diagnoses were assigned using established criteria. CPET data on 45 patients (238.3 ± 124 days post-test positivity) with a median age of 27.0 (22.0-40.0) were available for analysis. All but two (95.6%) were active-duty service members. The group showed substantial loss of aerobic capacity-average VO2 peak (L/min) was 84.2 ± 23% predicted and 25 (55.2%) were below the threshold for normal. Spirometry, diffusion capacity, high-resolution computed tomography, and echocardiogram were largely normal and were not correlated with VO2 peak. The two most common contributors to dyspnea and exercise limitation following comprehensive evaluation were deconditioning and dysfunctional breathing (DB). Younger active-duty military patients with persistent dyspnea following outpatient COVID-19 infection show a substantial reduction in aerobic capacity that is not driven by structural cardiopulmonary disease. Deconditioning and DB breathing are common contributors to their exercise limitation. The chronicity and severity of symptoms accompanied by DB could be consistent with an underlying myopathy in some patients, a disorder that cannot be differentiated from deconditioning using non-invasive CPET.

Cardiovascular Hemodynamic Response to Peak Exercise in Individuals with Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, progressive neurological condition that results in physical disability brought about, in part, by decreased aerobic capacity. Physical disability and aerobic deconditioning may increase risks of cardiovascular morbidity and mortality. The reduction in aerobic capacity may be associated with low maximal heart rate and/or low cardiac output. Yet it is unclear if the cardiovascular hemodynamic response to peak exercise differs between individuals with and without MS who have similar aerobic capacities. Purpose: To compare the cardiovascular hemodynamic response to peak exercise between individuals with and without MS, with similar aerobic capacities. We hypothesized individuals with similar aerobic capacities would also exhibit similar hemodynamic responses, regardless of disease condition. Methods: Individuals with MS (n=14 (2 males), 38 ± 8 yrs, 24.6 ± 4.5 kg/m 2 ) and without MS (n=14 (1 male), 33 ± 9 yrs, 28.8 ± 13.8 kg/m 2 ) underwent maximal incremental cycle exercise test to assess maximal aerobic capacity (VO 2 peak). Heart rate (HR) was measured continuously via Polar Heart Rate Monitor. Ascending aortic blood flow velocity images (VTI) via continuous wave Doppler echocardiography, and brachial blood pressure (BP) via brachial sphygmomanometry were obtained every other minute of the exercise test. Stroke volume (SV) was calculated from VTI and the area of the aorta, cardiac output (Q) was calculated as SV × HR, and Mean arterial pressure (MAP) was calculated from BP. Maximal arteriovenous oxygen difference (avO2diff) was calculated as VO 2 peak ⁄ Q. Results: There was no significant difference in VO 2 peak between groups (MS: 30.8 ml/kg·min -1 vs CON: 28.2 ml/kg·min -1 , p=0.65). Both groups (MS and CON) had significant time (rest to peak) differences in SV (rest: MS = 74.6 ± 32.5 mL, CON = 65.7 ± 23.1 mL, peak: MS = 114.4 ± 42.4 mL, CON = 84.2 ± 33.3 mL; p<0.001), HR (rest: MS = 65 ± 15 bpm, CON = 61 ± 10 bpm, peak: MS = 167 ± 13 bpm, CON = 175 ± 11 bpm; p<0.001), Q (rest: MS = 4.7 ± 2.2 L/m, CON = 4.0 ± 1.3 L/m, peak: MS = 12.3 ± 5.0 L/min, CON = 12.3 ± 5.1 L/min; p<0.001), and MAP (rest: MS = 84 ± 10 mmHg, CON = 83 ± 13 mmHg, peak: MS = 102 ± 7 mmHg, CON = 104 ± 17 mmHg, p <0.001). There was also a significant group by time interaction in HR (p = 0.04), but no group by time interactions in SV, Q, or MAP. Finally, there was not significant difference in avO 2 diff between groups (MS: 2.3 ± 1.2 mL/100 mL vs CON: 2.7 ± 1.5 mL/100 mL). Conclusion: Our findings suggest that individuals with MS exhibit different cardiac hemodynamics to achieve maximal aerobic capacity than those without MS. Individuals with MS reached maximal Q via a slightly higher, although statistically non-significant, stroke volume but a lower HR. This suggests that people with MS may rely on different mechanisms for achieving VO2peak compared to controls, but future research is needed to elucidate this hemodynamic pattern. Department of Defense office of the Congressionally Directed Medical Research Program on Multiple Sclerosis This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Multicomponent exercise training is effective in improving health and behavior indicators in Brazilian elderly women: A non-randomized trial

Objective: The aim was to evaluate the effects of a supervised 12-week Multicomponent exercise training on elderly women health and behavior indicators. Methods: Anthropometric characteristics and body composition, functional capacity, sedentary behavior, physical activity level and biochemical profile were evaluated in the control group (67.2 ± 5.2 years, n = 14) and in the experimental group (67.4 ± 6.1 years, n = 41). The experimental group were composed by 41 elderly women who performed 12 weeks of Multicomponent exercise training involving strength, aerobic, flexibility and balance exercises. The inclusion criteria for the study were women aged 60 years or more and presentation of a medical certificate authorizing the practice of physical exercise. Results: Maintenance of anthropometric characteristics and body composition was observed in both groups (p > 0.05). There was an improvement in aerobic capacity, lower and upper limb strength in the experimental group (p < 0.01), while the control group showed a reduction in aerobic capacity, lower limb strength, agility and dynamic balance (p < 0.01), as shown in Fi.gure 3. There was a reduction in sedentary behavior and an increase in physical activity level in experimental group (p < 0.05), but not in control group. Experimental group showed an improvement in glucose levels and lipid profile (p < 0.01). Conclusion: Multicomponent exercise training was efficient to improve health and behavior indicators of the elderly women.

Increased modifiable cardiovascular risk factors in patients with Takayasu arteritis: a multicenter cross-sectional study

BackgroundModifiable cardiovascular risk factors (MCRFs), such as those related to aerobic capacity, muscle strength, physical activity, and body composition, have been poorly studied in Takayasu arteritis (TAK). Therefore, the aim of the study was to investigate MCRFs and their relationships with disease status and comorbidities among patients with TAK.MethodsA multicenter cross-sectional study was conducted between 2019 and 2020, in which 20 adult women with TAK were compared with 16 healthy controls matched by gender, age, and body mass index. The following parameters were analyzed: aerobic capacity by cardiopulmonary test; muscle function by timed-stands test, timed up-and-go test, and handgrip test; muscle strength by one-repetition maximum test and handgrip test; body composition by densitometry; physical activity and metabolic equivalent by IPAQ, quality of life by HAQ and SF-36; disease activity by ITAS2010 and NIH score; and presence of comorbidities.ResultsPatients with TAK had a mean age of 41.5 (38.0–46.3) years, disease duration of 16.0 (9.5–20.0) years, and a mean BMI of 27.7±4.5 kg/m2. Three out of the 20 patients with TAK had active disease. Regarding comorbidities, 16 patients had systemic arterial hypertension, 11 had dyslipidemia, and two had type 2 diabetes mellitus, while the control group had no comorbidities. TAK had a significant reduction in aerobic capacity (absolute and relative VO2 peak), muscle strength in the lower limbs, increased visceral adipose tissue, waist-to-hip ratio, reduced walking capacity, decreased weekly metabolic equivalent, and quality of life (P< 0.05) as compared to controls. However, there were no correlations between these MCRFs parameters and disease activity.ConclusionsTAK show impairment in MCRFs; therefore, strategies able to improve MCRF should be considered in this disease.

Aerobic capacity and telomere length in human skeletal muscle and leukocytes across the lifespan.

A reduction in aerobic capacity and the shortening of telomeres are hallmarks of the ageing process. We examined whether a lower aerobic capacity is associated with shorter TL in skeletal muscle and/or leukocytes, across a wide age range of individuals. We also tested whether TL in human skeletal muscle (MTL) correlates with TL in leukocytes (LTL). Eighty-two recreationally active, healthy men from the Gene SMART cohort (31.4±8.2 years; body mass index (BMI)=25.3±3.3kg/m2), and 11 community dwelling older men (74.2±7.5years-old; BMI=28.7±2.8kg/m2) participated in the study. Leukocytes and skeletal muscle samples were collected at rest. Relative telomere length (T/S ratio) was measured by RT-PCR. Associations between TL, aerobic capacity (VO2 peak and peak power) and age were assessed with robust linear models. Older age was associated with shorter LTL (45% variance explained, P<0.001), but not MTL (P= 0.7). Aerobic capacity was not associated with MTL (P=0.5), nor LTL (P=0.3). MTL and LTL were correlated across the lifespan (rs=0.26, P=0.03). In healthy individuals, age explain most of the variability of LTL and this appears to be independent of individual aerobic capacity. Individuals with longer LTL also have a longer MTL, suggesting that there might be a shared molecular mechanism regulating telomere length.

PO-014 The effects of HIIT on ROS-AMPK- PGC-1α pathway in skeletal muscle and VO2max of ageing Wistar rats.

Objective To observe the 16 weeks of HIIT intervention on SOD,ROS and its related factors AMPK and oxidation capacity PGC-1α expression and the influence of the VO2max and its change rule in the process of the natural aging rats, To explore the correlation between the expression of ROS, AMPK and PGC-1αand the change of VO2max; Furthermore, it provides a theoretical basis for HIIT to delay the reduction of aerobic capacity in skeletal muscle ageing.&#x0D; Methods 58 male wistar rats(age：32 weeks) were selected and randomly divided into quiet group (C) and HIIT intervention group (H). All rats were fed in the barrier environment. Each group of rats entered the animal laboratory for a week of adaptive feeding and exercise. VO2max was tested and observed every two weeks in each group. Rats of group C don't exercise, group H at a rate of 50%, 70% and 90% VO2max corresponding alternation of 50 min/day, 5 days/week, for 16 weeks of exercise intervention, and according to the VO2max test results the exercise intensity. Both groups of rats in the intervention of 8 weeks, 16 weeks after the end of the 24 hours of materials, stripping rats soleus, SOD and content of ROS was tested by multifunctional enzyme mark, using western blot test the expression of AMPK and PGC-1α. VO2max, SOD, ROS test results and AMPK, PGC-1α, and relative expression data were analyzed using SPSS for one way ANOVA.&#x0D; Results The cardiopulmonary endurance of rats in group C and group H showed a decreasing trend in group C and group H during HIIT intervention, but the decrease trend in group H was slower than that in group C. 2. During 16 weeks aging , SOD expression of group C in the process of rendering first rise after falling, and expressed in 8 weeks SOD content was significantly lower than base value (P &lt; 0.05), 16 weeks group C SOD levels higher than the base state. After 16 weeks of intervention, the expression of SOD in group H was relatively flat in the first 8 weeks, and the trend was in 8-16 weeks, and was significantly lower than 8 weeks in 16 weeks (P &lt; 0.05). 3.The ROS content was significantly higher than basic state in 8 weeks and 16 weeks in the intervention process (P&lt;0.05), and the ROS content was significantly higher than 8 weeks (P&lt;0.05) at 16 weeks. The ROS content of group C and group H was significantly higher than that in the group at 8 weeks (P &lt; 0.05). 4.The AMPK content in group C was significantly lower than that of the basic value (P&lt;0.05), and the AMPK content in group H was significantly higher than that in group C (P&lt;0.05). 5.After the intervention of 16 weeks, the content of PGC-1α in group C and group H showed a decrease trend and significantly lower than the basic value (P&lt;0.05), but the content of group H was significantly higher than that of group C (P&lt;0.05). 6.The changes of AMPK, PGC-1α and cardiopulmonary endurance were the same in all groups during the intervention.&#x0D; Conclusions 1.16 weeks of HIIT can effectively delay the decrease of SOD content in the aging rats, thus inhibiting the accumulation of ROS in the body. 2.16 weeks of HIIT intervention can effectively delay the expression of VO2max and AMPK and PGC-1α in aging rats. 3.16 weeks HIIT may delay the decrease of AMPK-PGC1 protein expression by inhibiting the accumulation of skeletal muscle ROS in the aging rats, thus inhibiting the decrease of VO2max.

Maximum Strength Estimate of Quadriceps and Brachial Biceps Muscles in Patients with Chronic Heart Disease

Patients diagnosed with heart disease display diminished exercise tolerance, which can be attributed not only to a reduction in aerobic capacity but probably also to a strength deficit. The aim of this study was to estimate maximum dynamic strength of the quadriceps and the brachial biceps muscles in patients affected by chronic heart disease. Maximum strength was estimated by means of sub-maximal tests in 30 healthy sedentary volunteers and 140 male patients with chronic heart disease: 52 patients with coronary artery disease (CA D); 72 patients diagnosed with chronic heart failure (CHF); 16 patients who had undergone heart transplant (HT). Maximum strength estimate of the two muscles tested was significantly lower in patients diagnosed with heart disease compared to the control group. When patients were subdivided according to the type of disease, a clear trend among groups was displayed with maximum strength being higher in controls, followed by the CA D group, then the CHF group, and the HT group. In conclusion it seems possible to assert that maximum strength of both the muscle groups examined is significantly lower in patients diagnosed with cardiovascular disease than in control subjects. Moreover, chronic cardiovascular patients are characterized by a muscular impairment that parallels the history of the disease. This information should be kept in mind when planning a rehabilitation program.

Maximum Strength Estimate of Quadriceps and Brachial Biceps Muscles in Patients with Chronic Heart Disease

Patients diagnosed with heart disease display diminished exercise tolerance, which can be attributed not only to a reduction in aerobic capacity but probably also to a strength deficit. The aim of this study was to estimate maximum dynamic strength of the quadriceps and the brachial biceps muscles in patients affected by chronic heart disease. Maximum strength was estimated by means of sub-maximal tests in 30 healthy sedentary volunteers and 140 male patients with chronic heart disease: 52 patients with coronary artery disease (CA D); 72 patients diagnosed with chronic heart failure (CHF); 16 patients who had undergone heart transplant (HT). Maximum strength estimate of the two muscles tested was significantly lower in patients diagnosed with heart disease compared to the control group. When patients were subdivided according to the type of disease, a clear trend among groups was displayed with maximum strength being higher in controls, followed by the CA D group, then the CHF group, and the HT group. In conclusion it seems possible to assert that maximum strength of both the muscle groups examined is significantly lower in patients diagnosed with cardiovascular disease than in control subjects. Moreover, chronic cardiovascular patients are characterized by a muscular impairment that parallels the history of the disease. This information should be kept in mind when planning a rehabilitation program.

The Association Between Waist Circumference and FITNESSGRAM® Aerobic Capacity Classification in Sixth-Grade Children.

Cardiorespiratory fitness is often assessed through measures of maximal oxygen uptake, sometimes referred to as aerobic capacity (26). The importance of adequate aerobic capacity for optimal health has been observed in numerous studies examining both adults (1,2,20) and children (17,24). An increased risk of overweight and metabolic syndrome in adults can result from a reduction in aerobic capacity from childhood to adolescence (4,11).

Aerobic Capacity Before And After Radio Frequency Ablative Treatment For Atrial Fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia which is presently being treated with Radio frequency ablative surgery and its effects on aerobic capacity is unknown. Aerobic capacity has been assessed on all age ranges but there is little data on individuals with atrial fibrillation. PURPOSE: To determine the aerobic capacity in individuals with atrial fibrillation before and after radio frequency ablative treatment. METHODS: 12 individuals diagnosed with atrial fibrillation and scheduled for radiofrequency ablative surgery (65.25 ± 9.20 years) were selected for testing of which 3 were females and 9 were males. The tests were scheduled for one week prior and one month after the procedure. Graded exercise tests were completed on a cycle ergometer with a minimum cadence of 50 rpm. Heart rate metabolic data, and perceived exertion was collected at rest, exercise, and recovery. RESULTS: Twelve subjects complete testing prior to the procedure and three were able to complete the follow-up testing after 1 month of the procedure. Nine subjects withdrew due to post-operative complications (n=4) and treatment failure (n=5). Baseline VO2 for the twelve subjects was 13.24 ± 5.64 ml/kg/min. The three subjects able to complete the before and after assessments showed a reduction in aerobic capacity (14.4 ± 3.1 and 11.46 ± 3.82 ml/kg/min, respectively). Although this is statistically insignificant due to the low number of participants, it should be noted that these values are substantially lower than the normative values for that average age range pre and post testing. CONCLUSION: The aerobic capacity of all subjects’ prior to surgery were low when compared to normative data for their age group and fell in a range closer to heart failure NYHA Class III. The post-operative data shows further deterioration suggesting that one month post-surgery is not enough time for full recovery of this patient population. Further studies should assess long-term follow-up post 6 and 12 months to identify the effects of this procedure on physical capacity.

A Comparison of Effects of Rapid and Gradual Weight Loss Methods on Body Composition, Aerobic Capacity, and Anaerobic Power in Trained Wrestlers

ABSTRACTIntroduction: Weight loss in many sports particularly in weight category sports is very important, since it can play a major role in the success of athletes. The purpose of this study was to compare the effects of rapid and gradual weight loss protocols on body composition, aerobic capacity, and anaerobic power in trained wrestlers.Methods: 22 trained wrestlers (mean age: 20 to 25 y) volunteered to participate and were randomly assigned into two rapid (group 1) and gradual (group 2) groups. Participants in group 1 lost their weight during 48 hours using traditional methods, while subjects in group 2 did it according to a well-designed diet over a span of 12 days. All subjects were asked to reduce approximately 4% of their body weight. Prior and after the weight loss interventions, body composition, aerobic capacity, and anaerobic power were measured via Bruce and Wingate tests.Results: Results showed that rapid weight loss caused to a significant reduction in aerobic capacity, and anaerobic power ...

Influence of body mass index, body fat percentage and age at menarche on aerobic capacity (VO₂ max) of elementary school female students

To identify and relate body fat percentage (skin fold measures), body mass index (BMI) and age at menarcheto aerobic capacity using the indirect VO₂ maximum value (VO₂ max) of girls in the second cycle of primary school. A total of 197 girls aged 13.0 ± 1.2 years on average, students from two public schools in the city of Atibaia in São Paulo, were evaluated. Anthropometric evaluation of skin folds was performed using the Slaughter protocol for teenage girls, and BMI (kg/m²) was based on "Z score" (graphic of percentile) according to WHO recommendations. The Léger protocol was used to determine VO₂ max. Pearson linear regression and the Student t-test were used for statistical analysis. 22.3% of the girls were overweight and 3.5% were obese according to the classification proposed by the WHO; 140 (71.1%) girls reported menarche. The average age at menarche was 12.0 ± 1.0 years and was significantly higher in the group with normal BMI (12.2 ± 0.9 years) than in the overweight or obese groups (11.6 ± 1.0 years). The average indirect VO₂ max value was 39.6 ± 3.7 mL/kg/min, ranging from 30.3 to 50.5 mL/kg/min. The advance of chronological age and early age at menarche were positively correlated with lower VO₂ max values. This study showed that 25.8% of the girls had aBMI value above WHO recommendations. Girls with higher BMI and higher body fat percentage had lower VO₂ max. The earlier age at menarche and the advance of chronological age were the most important factors for the reduction of aerobic capacity. The ageat menarche was higher in girls with adequate BMI compared tooverweight or obese girls.

NO OXYGEN? SHUT DOWN YOUR F1FO-ATPASE

Mitochondria are our bodies' powerhouses, and to efficiently produce energy, via aerobic respiration, they use the enzymatic activities of four different protein complexes (I to IV) to pump hydrogen ions across the inner mitochondrial membrane. The H+ ions will then flow back into the mitochondria, down their concentration gradient, via a fifth complex, which drives ATP production, where the H+ ions are then accepted by oxygen to make water. ‘Without oxygen, animals have to move to anaerobic respiration, which yields a much lower level of ATP. So their balance between ATP supply and demand is greatly affected’, explains Gina Galli, from the University of Manchester, UK. The absence of oxygen (anoxia) can be disastrous, as can be seen in pathologies such as stroke or heart attacks, but for some animals, such as the red-eared slider turtle, anoxic periods are just a normal part of life. So, as part of her postdoc in Jeffrey Richards' lab at the University of British Columbia, Canada, Galli decided to find out what we can learn from anoxia tolerant turtles (p. 3283).Galli already knew some of the tricks turtles employ during periods of anoxia: ‘They have the ability to shut down all the cellular processes in their bodies that consume a large amount of ATP, but we wanted to see if that was also the case at the level of the mitochondria.’ To investigate this possibility, she divided 26 turtles into two groups. One group was kept in normal, normoxic water conditions while the other group was submerged in water devoid of oxygen for 2 weeks. Galli then isolated cardiac fibres from the turtle's hearts and placed individual fibres into tiny respirometer chambers, equipped with oxygen-sensing electrodes. Galli could then measure the fibres' aerobic respiration capacity by how much oxygen was depleted. To measure the capacity of the individual complexes I–IV, Galli used specific drugs to inhibit each complex. Overall, she found that the aerobic capacity at complexes I–IV was reduced in the cardiac fibres from anoxic turtles.Next, Galli wondered whether this reduction in aerobic capacity was caused by a reduction in the enzymatic activity of each complex. To test this, Galli supplied tissue samples with substrates that were unique to each complex, one by one, and measured how much product was produced. To her surprise, Galli found that each of the complexes from anoxic turtles was working at the same rate as complexes from normoxic turtles. Perplexed, Galli wondered whether the apparent reduction in aerobic capacity was perhaps just due to a decrease in the total number of mitochondria in cardiac cells from anoxic turtles. However, anoxic and normoxic cardiac fibres were able to produce the same amount of citrate (via the unique mitochondrial enzyme citrate synthase), suggesting that total mitochondrial levels were the same in the two conditions.So, Galli decided to test the enzymatic activity of the fifth and final complex, also known as the F1FO-ATPase, and found its enzymatic activity was indeed shut down. Suddenly, everything fell into place – shutting down this complex would reduce flow through complexes I–IV but not their enzymatic activities. In addition, shutting down this complex has clear benefits, as Galli explains: ‘When there's no oxygen, the F1FO-ATP synthase will start consuming ATP to keep that H+ gradient going. It starts to chew up all of the available ATP; it will eventually lead to ATP depletion and that's one of the biggest contributors to cellular breakdown.’ Recent studies have shown that, in mammals, drugs inhibiting this final complex do protect tissues against anoxia, but it seems that turtles have known the secret all along!

Metabolic rate, cardiac response, and aerobic capacity in fibromyalgia: a case–control study

Objectives: Several studies report reduced aerobic capacity in patients with fibromyalgia (FM). The purpose of our study was to investigate whether a reduction in aerobic capacity in these patients is accompanied by alterations in metabolic rate and heart rate (HR) response.Method: Twelve women with FM and 12 healthy controls (HCs) matched on sex and age, and with similar leisure time physical activity, participated in the study. All subjects performed an incremental submaximal cycle ergometer test to anaerobic threshold [AT; i.e. blood lactate concentration (bLa) ≥ 4 mmol/L], followed by a stepwise test to exhaustion to estimate maximal oxygen consumption (VO2max).Results: Oxygen consumption and workload were lower among patients than HCs both at AT and at termination of the VO2max test (p < 0.011 for all comparisons). Two patients (18%) and nine HCs (75%) reached VO2max criteria. The relationship between metabolic rate and workload did not differ between groups at exercise below AT. At exercise above AT, the metabolic rate increased disproportionally to workload in the patients. Although the patients had a higher anaerobic contribution to the total metabolic rate at the end of the submaximal test, the anaerobic contribution at the end of the maximal test did not differ between groups. HR responses were largely similar between groups.Conclusions: The current study indicates that patients with FM have similar metabolic and cardiovascular responses to submaximal exercise as HCs. However, these patients have reduced ability to reach VO2max and a possible deficit in the metabolic system when exercising above the AT.

Physical fitness, walking performance, and gait in multiple sclerosis

BackgroundWalking impairment is a prevalent, life-altering feature of multiple sclerosis (MS). There has been recent speculation that physiological deconditioning (i.e., reductions in aerobic capacity, balance, and muscular strength) contributes to walking and gait impairments in MS. ObjectiveThis study examined the associations among aerobic capacity, balance, and lower-limb strength asymmetries, walking performance, and gait kinematics in 31 persons with MS and 31 matched controls. MethodsParticipants underwent standard assessments of peak aerobic capacity, muscular strength (i.e., asymmetry between knee muscles), and balance. Walking performance was measured using the timed 25-ft walk (T25FW) and six-minute walk (6MW). Gait parameters were captured using a GaitRite™ electronic walkway. ResultsAerobic capacity, balance, and knee-extensor asymmetry were associated with walking performance and gait in persons with MS (r=.2–.6) and explained differences in walking and gait variables between MS and control groups (∆R2=.27–.34). Aerobic capacity and lower-limb strength asymmetries, but not balance, explained significant variance in walking performance and gait kinematics in the MS sample (R2=.32–.58). ConclusionsPhysiological deconditioning explains variability in walking disability in persons with MS and might represent a target of multimodal exercise training interventions for improving mobility outcomes in this population.

Fructose-rich diet leads to reduced aerobic capacity and to liver injury in rats.

The main purpose of this research was to investigate the alterations in the aerobic capacity and appearance of metabolic alterations in Wistar rats fed on fructose-rich diet. We separated twenty-eight rats into two groups according to diet: a control group (C) (balanced diet) and a fructose-rich diet group (F). The animals were fed these diets for 60 d (d 120 to 180). We performed insulin, glucose as well as a minimum lactate test, at d 120 and 180. At the end of the experiment, sixteen animals were euthanized, and the following main variables were analysed: aerobic capacity, the serum aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio, serum and liver triglyceride concentrations, serum and liver thiobarbituric acid reactive substance (TBARS) concentrations, serum and liver catalase and superoxide dismutase (SOD) activity and haematoxylin-eosin histology (HE) in hepatocytes. The remaining twelve animals were submitted to an analysis of their hepatic lipogenic rate. The animals fed a fructose-rich diet exhibited a reduction in aerobic capacity, glucose tolerance and insulin sensitivity and increased concentrations of triglycerides and TBARS in the liver. Catalase and SOD activities were reduced in the livers of the fructose-fed animals. In addition, the serum AST/ALT ratio was higher than that of the C group, which indicates hepatic damage, and the damage was confirmed by histology. In conclusion, the fructose-rich diet caused significant liver damage and a reduction in insulin sensitivity in the animals, which could lead to deleterious metabolic effects.

Mechanisms underlying parallel reductions in aerobic capacity in non-migratory threespine stickleback (Gasterosteus aculeatus) populations

Non-migratory, stream-resident populations of threespine stickleback, Gasterosteus aculeatus, have a lower maximum oxygen consumption ((O(2),max)) than ancestral migratory marine populations. Here, we examined laboratory-bred stream-resident and marine crosses from two locations (West and Bonsall Creeks) to determine which steps in the oxygen transport and utilization cascade evolved in conjunction with, and thus have the potential to contribute to, these differences in (O(2),max). We found that West Creek stream-resident fish have larger muscle fibres (not measured in Bonsall fish), Bonsall Creek stream-resident fish have smaller ventricles, and both stream-resident populations have evolved smaller pectoral adductor and abductor muscles. However, many steps of the oxygen cascade did not evolve in stream-resident populations (gill surface area, hematocrit, mean cellular hemoglobin content and the activities of mitochondrial enzymes per gram ventricle and pectoral muscle), arguing against symmorphosis. We also studied F1 hybrids to determine which traits in the oxygen cascade have a genetic architecture similar to that of (O(2),max). In West Creek, (O(2),max), abductor and adductor size all showed dominance of marine alleles, whereas in Bonsall Creek, (O(2),max) and ventricle mass showed dominance of stream-resident alleles. We also found genetically based differences among marine populations in hematocrit, ventricle mass, pectoral muscle mass and pectoral muscle pyruvate kinase activity. Overall, reductions in pectoral muscle mass evolved in conjunction with reductions in (O(2),max) in both stream-resident populations, but the specific steps in the oxygen cascade that have a genetic basis similar to that of (O(2),max), and are thus predicted to have the largest impact on (O(2),max), differ among populations.

Run Performance of Middle-Aged and Young Adult Runners in the Heat

The aging process may impair exercise tolerance in the heat. It is not clear whether this impairment is partly due to a reduction in aerobic capacity. To compare the exercise performance and thermoregulatory responses of middle-aged and young adults with similar aerobic capacities and training statuses, 7 middle-aged (54±2 years; 58±4 ml·kg - 1·min - 1) and 7 young (28±1 years; 61±5 ml·kg - 1·min - 1) male competitive endurance runners underwent 2 10-km self-paced and 2 fixed-workload (90% of race speed) runs until fatigue on a treadmill in hot (40°C) and moderate (20°C) environments on separate days. The runners' total time, average speed, rectal temperature, heat storage rate, physiological strain index, sweat rate, sweat sensitivity, number of heat-activated sweat glands and sweat rate per sweat gland were measured or calculated. Body fat, body surface area, body surface area per body mass, training volume and VO2max were similar between the 2 groups. No differences were observed in total time (59±3; 49±3; 27±2; 54±5 min in the middle-aged and 60±2; 49±3; 27±2; 51±4 min in the young group), average speed, rectal temperature, heat storage rate, physiological strain index, sweat rate (17±7; 15±3; 23±7; 13±2 g.m - 2.min - 1 in the middle-aged and 20±5; 14±4; 22±5; 15±4 g.m - 2.min - 1 in the young group) or sweat sensitivity between age groups (p>0.05) in any trial. The number of heat-activated sweat glands (88±14; 80±18; 90±16; 66±14 cm - 2 in the middle-aged and 43±10; 32±10; 37±11; 31±11 cm - 2 in the young group) was higher, and the sweat rate per sweat gland was smaller, in the middle-aged than the young group (p<0.05) in all of the trials. We conclude that running performance and body thermoregulation are similar between young and middle-aged runners with similar aerobic capacities and training statuses under hot and moderate conditions in self-paced and fixed-intensity runs. The decrease observed in the sweat rate per sweat gland in middle-aged men was compensated for by a higher number of heat-activated sweat glands.

Neuromuscular Economy, Strength, and Endurance in Healthy Elderly Men

Declines in muscular strength resulting from reduced neural activity may influence the reduction in aerobic capacity in older men. However, there has been little investigation into the relationship between muscular strength and economy of movement during aerobic exercise in elderly subjects. Thus, the purpose of this study was to investigate the possible relationship between strength, aerobic performance, and neuromuscular economy in older men. Twenty-eight aged men (65 ± 4 years old) were evaluated in dynamic (1 repetition maximum test), isometric strength (maximal voluntary contraction), and rate of force development. Peak oxygen uptake, maximal workload, and ventilatory threshold were determined during a ramp protocol on a cycle ergometer. Throughout the same protocol, the neuromuscular economy (electromyographic signal) of the vastus lateralis was measured. Significant correlations were found between muscular strength, cardiorespiratory fitness, and neuromuscular economy (r = 0.43-0.64, p < 0.05). Our results suggest that cardiorespiratory capacity and economy of movement are associated with muscular strength during aging.

Age related decreases in thermoregulation and cardiovascular function in horses

Older horses have an increased risk of hyperthermia due to impaired cardiovascular function. While many studies have investigated thermoregulation in horses during exercise, none have investigated the effects of ageing. To test the hypothesis that there is a difference in thermoregulation during exercise and plasma volume (PV) in young and old horses. Study 1: 6 young (Y, 7.7 ± 0.5 years) and 5 old (O, 26.0 ± 0.8 years) unfit Standardbred mares (507 ± 11 kg, mean ± s.e.) ran on a treadmill (6% grade, velocity calculated to generate a work rate of 1625 watts) until core temperature reached 40 °C. Core (CT), skin (ST), rectal temperature (RT) and heart rate (HR) were measured every min until 10 min post exertion. Packed cell volume (HCT), lactate (LA) and plasma protein (TP) were measured in blood samples collected before, at 40 °C and every 5 min until 10 min post exercise. Sweat loss was estimated using bodyweight. Study 2: Plasma volume was measured in 26 young (8.2 ± 0.7 years) and 8 old (26.6 ± 0.7 years) Standardbred mares (515 ± 12 kg) using Evans Blue dye. Pre-exercise blood (rBV) and red cell (rRCV) volumes were calculated using PV and HCT. Data analysis utilised repeated measures ANOVA and t tests and data are expressed as mean ± s.e. Old horses reached 40 °C faster (998 ± 113 vs. 1925 ± 259 s; P < 0.05) with a greater HR at 40 °C (184 ± 6 vs. 140 ± 5 beats/min; P < 0.05) and greater sweat losses (P < 0.05). Heart rate did not differ (P > 0.05) post exercise. Age did not alter (P > 0.05) CT, ST, RT, LA, HCT or TP. Plasma volume was greater in Y vs. O horses (P < 0.05, 28.5 ± 1.4 vs. 24.1 ± 1.6 l) as was rBV (41.3 ± 2.0 vs. 35.3 ± 2.3 l) and rRCV (13.3 ± 0.6 vs. 11.1 ± 0.8 l). Ageing compromises the ability to handle the combined demand of exercise and thermoregulation in part due to decreased absolute pre-exercise PV.