Changes In Aerobic Capacity Research Articles

Prognostic Relevance of Changes in Exercise Test Variables in Pulmonary Arterial Hypertension

IntroductionExercise variables determined in patients with pulmonary arterial hypertension (PAH) at the time of diagnosis, predict survival. It is unknown whether upon treatment, subsequent changes in these exercise variables reflect improvements in survival. The aim of this study was to determine changes in exercise variables in PAH patients and to relate these changes to survival.MethodsBaseline cardiopulmonary exercise test (CPET) variables and six-minute-walk-distance (6MWD) were available from 65 idiopathic PAH patients (50 females; mean age 45±2yrs). The same variables were determined after treatment (13months) in a sub group of 43 patients. To estimate the association between changes in exercise variables and changes in cardiac function, right-ventricle ejection fraction (RVEF) was measured by cardiac MRI at baseline and after treatment in 34 patients. Mean follow-up time after the second CPET was 53 (range: 4-111) months. Kaplan-Meier analysis was used to relate survival to baseline and treatment-associated changes in exercise variables.ResultsSurvivors showed a significantly greater change in maximal oxygen uptake than non-survivors and this change in aerobic capacity was significantly related to changes in RVEF. From baseline until the end of the study period, two patients underwent a lung transplantation and 19 patients died. Survival analysis showed that baseline 6MWD (p<0.0001), maximal heart rate (p<0.0001) and the slope relating ventilation with carbon dioxide production (p≤0.05) were significant predictors of survival, whereas baseline oxygen uptake and oxygen pulse held no predictive value. Treatment associated changes in 6MWD (p<0.01), maximal heart rate (p<0.05), oxygen uptake (p<0.001) and oxygen pulse predicted survival (p<0.05), whereas changes in the slope relating ventilation with carbon dioxide production did not.ConclusionExercise variables with prognostic significance when determined at baseline, retain their prognostic relevance after treatment. However, when changes in exercise variables upon treatment are considered, a different set of variables provides prognostic information.

Effects of participation in popular weight loss and fitness programs on markers of health and fitness in women

125 sedentary women (46±12 yr, 45.5±5% body fat, 35.0±5 kg/m2) were randomized to participate in a control group (C) or Curves Complete® (CC), Weight Watchers® (WW), Jenny Craig® (JC), or Nutrisystem® (NS) weight loss programs for 12‐ wks. Participants in the diet groups were encouraged to exercise (WW, JC, NS) while those in the CC group participated in a structured exercise program. Data were analyzed by MANOVA or ANOVA and are presented as changes from baseline after 12‐wks. Participants in the diet groups had greater changes in waist (C 2.1±6.9; CC −4.7±3.2; WW −4.1±5.7; JC −3.7±3.6; NS −3.3±6.4 %, p=0.001) and hip circumference (C 0.7±2.5; CC −4.0±2.6; WW − 2.5±2.4; JC −4.2±3.5; NS −3.6±3.5 %, p=0.001). Resting HR (− 2.5±9 %, p=0.005) and SBP (−4.0±12 %, p=0.005) decreased over time with no change in DBP. SBP decreased more in some diet and exercise groups compared C (p&lt;0.05). Changes in PAC (C − 2.2±10; CC 14.4±10; WW 7.9±19; JC 8.1±11; NS 3.8±7 %, p=0.001) and 1 RM bench press (C −1.2±14; CC 6.0±12; WW 4.9±15; JC 5.4±14; NS −3.7±15 %, p=0.06). Results indicate diet and exercise programs promote improvements in fitness and the CC program promotes greater changes in aerobic capacity.

Factors associated with change in aerobic capacity following an exercise program for individuals with stroke

Community exercise programs are effective in improving aerobic capacity after stroke, but individual variability in training responses has not previously been studied. This study examined explanatory factors for post-program responses in aerobic capacity (VO2peak) with respect to training parameters and participant characteristics. Secondary analysis of data from a prospective cohort study. Thirty-two participants, mean age 63 years (standard deviation (SD) 13), 29 months (SD 26) post-stroke. Following a 6-month community exercise program, multivariate regression analysis was performed to assess for correlates with change in VO2peak with respect to training parameters (exercise duration and intensity) and participant characteristics (lower limb and balance impairment, aerobic and walking capacity). The mean improvement in VO2peak was 11% (SD 19), but individually, changes ranged from 32% decline to 56% improvement. Regression analysis revealed that only 2 variables, baseline aerobic capacity and balance impairment, accounted for the training-related change in VO2peak (R2 = 0.20, p = 0.045). There is considerable inter-individual variability in stroke exercise program responses in aerobic capacity. Lower baseline aerobic capacity and better balance were associated with greater training-related improvements in VO2peak. Identifying individuals who are more likely to respond to exercise programs may inform future work in establishing effective interventions suited for different subsets of the stroke population.

Aging has greater impact on anaerobic versus aerobic power in trained masters athletes

This study measured the relative rates of change of the three human energy systems across a 30-year age range. A cross-section of highly trained masters cyclists (n = 156 males and 17 females; 35–64 years) were tested for maximal cycling performance. There were 50 (29%) track sprint cyclists and the remaining (71%) were predominantly road cycling specialists. A 10 s peak power test measured anaerobic power, a 30 s test measured anaerobic capacity, and a progressive test to volitional fatigue was used to determine peak aerobic power. Participants’ exercise patterns were recorded using a physical activity recall questionnaire. Linear regression showed significant changes in anaerobic performance with aging. Peak anaerobic power (W · kg−1) declined at a rate (mean ± SEE) of 8.1 ± 4.1% per decade (P < 0.0001) and anaerobic capacity (kJ · kg−1) declined at 8.0 ± 3.3% per decade (P < 0.0001). Peak aerobic power [W · kg−1] did not change significantly with age [−1.8 ± 1.5% per decade (P = 0.218)]. This cross-sectional study showed performance of the two anaerobic energy systems declined significantly across the age spectrum with no change in aerobic capacity.

Lifestyle Factors Predicting Changes in Aerobic Capacity of Aging Firefighters at 3- and 13-Year Follow-Ups

To describe changes in aging firefighters' aerobic capacity at 3- and 13-year follow-ups, and to investigate the lifestyle factors predicting them. We evaluated the sufficiency of aerobic capacity for the demands of rescue diving. We studied 78 male Finnish firefighters aged 30 to 44 years at baseline. The outcome variable was aerobic capacity (L·min(-1) and mL·kg(-1)·min(-1)). The predictors were exercise, smoking, and drinking habits. The average annual change (range) in absolute and relative aerobic capacity was -1.12% (-3.43 to 1.39) and -1.33% (-3.98 to 1.63). Exercising at least 4 to 5 times a week was the best protective factor, and regular smoking and more than 15 units of alcohol a week were risk factors for decline in aerobic capacity. To prevent the excessive decline of aerobic capacity related to work demands, we must pay particular attention to exercise regularity.

Aerobic capacity in speed‐power athletes aged 20–90 years vs endurance runners and untrained participants

We studied relationships between age and aerobic capacity in three groups of subjects adhering to different exercise modalities. A total of 203 men aged 20-90 years were examined: 52 speed-power track and field athletes (SP), 89 endurance runners (ER) and 62 untrained individuals (UT). Maximal exercise characteristics were obtained during a graded treadmill test until exhaustion: oxygen uptake (VO2max), heart rate (HRmax), oxygen pulse (O2 Pulsemax) and maximal distance (Distmax). Information about training history and weekly training amount was collected. A linear model of regression was adopted. VO2max in SP was lower than in ER, but significantly higher than in UT. The cross-sectional rates of decline in body mass-adjusted VO2max and Distmax were significantly smaller in SP than in ER and UT. About 80 years of age, the levels of VO2max and Distmax reached similar values in SP and ER. The decline in HRmax, but not in O2 Pulsemax was suggested as a cardiac adaptation accounting for between-group differences in VO2max loss. Weekly training volume was a significant positive predictor of age-related changes in aerobic capacity. In conclusion, not only endurance, but also speed-power exercise appears adequate to ensure an elevated aerobic capacity at old age.

The Morganroth hypothesis revisited: endurance exercise elicits eccentric hypertrophy of the heart

The Morganroth hypothesis revisited: endurance exercise elicits eccentric hypertrophy of the heart

β-Alanine Supplementation

β-Alanine is rapidly developing as one of the most popular sport supplements used by strength/power athletes worldwide. The popularity of β-alanine stems from its unique ability to enhance intramuscular buffering capacity and thereby attenuating fatigue. This review will provide an overview of the physiology that underlies the mechanisms of action behind β-alanine, examine dosing schemes, and examine the studies that have been conducted on the efficacy of this supplement. In addition, the effect that β-alanine has on body mass changes or whether it can stimulate changes in aerobic capacity also will be discussed. The review also will begin to explore the potential health benefits that β-alanine may have on older adult populations. Discussion will examine the potential adverse effects associated with this supplement as well as the added benefits of combining β-alanine with creatine.

Endurance and resistance training lowers C-reactive protein in young, healthy females

The purpose of this study was to determine whether endurance (E) or endurance + resistance (ER) training affects C-reactive protein (CRP) and if these changes are related to alterations in fitness and (or) body composition in young females. Thirty-eight females (aged 18-24 years) were assigned to 1 of 3 groups: (1) E, (2) ER or (3) active control (AC). The E and ER groups completed 15 weeks of marathon training. The ER group performed additional resistance training and the AC group maintained their usual exercise routine. Primary outcomes were measured pre- and post-training and included anthropometric indices, dual-energy x-ray absorptiometry, plasma CRP, time to complete 1.5 miles (in minutes), and upper and lower body strength tests (i.e., 8 repetition max on bench and leg press (ER group only)). There were no differences in any variable among the groups at baseline. After training, the E group decreased time to complete 1.5 miles (p < 0.05). The AC group decreased percent and absolute body fat while the E group decreased percent body fat, absolute body fat, and android and gynoid body fat (p < 0.05). The ER group significantly improved strength (p < 0.001) and reduced plasma CRP from 2.0 ± 1.1 to 0.8 ± 0.3 mg·L(-1) (p = 0.03). No significant associations were observed between CRP and measures of body composition or aerobic capacity. Combined endurance and resistance training may be an effective modality for reducing plasma CRP in young adult females independent of changes in aerobic capacity or body composition.

Skeletal Muscle DNA and Mixed Muscle Protein Synthesis Rates with Endurance Training in Aging Humans

Decreased rates of synthesis in skeletal muscle may contribute to loss of muscle mass with age. Acute studies show that resistance exercise can increase mixed muscle protein synthesis, an effect that is enhanced with protein consumption. However, less is known about the ability of endurance exercise training and protein consumption to promote synthetic processes. Deuterium oxide (D2O) consumption allows measurement of multiple synthetic processes and provides insight into skeletal muscle adaptations over extended periods. PURPOSE: The purpose of our study was to use D2O to determine long-term rates of protein, DNA and membrane phospholipid synthesis in skeletal muscle during endurance exercise training. METHODS: ixteen healthy adult males and females (Age: 50±8 yrs, BMI: 25.3±4.1 kg/m2, VO2 max: 28.3±6.4 ml/kg/min) participated in 6-weeks of endurance exercise training and were randomized to consume either carbohydrate (CHO) or an iso-caloric drink with 20-grams protein (PRO) following each session. Each participant also consumed D2O daily to determine the synthesis rate of proteins (MPS), DNA (DNA%F) and membrane phospholipid glycerol (GLY). VO2 max and muscle biopsies were performed pre and post training. Total muscle proteins, DNA and GLY were extracted from muscle biopsy samples and analyzed for deuterium enrichment using gas or liquid chromatography and mass spectrometry. RESULTS: he increase in VO2 max with training was greater in PRO compared to CHO (PRO=+12.8±6.2% vs. CHO=+2.8±8.7%, p=0.033). MPS was not different between PRO and CHO (PRO=0.05±0.01 vs. CHO=0.06±0.01 %/hr). DNA%F was not different between PRO and CHO (PRO=3.3±2.6 vs. CHO=5.3±2.8 % new in 6-weeks). MPS and DNA%F were correlated (r2=0.26, p=0.055). The synthesis of GLY was not different between PRO and CHO (PRO=37.6±11.9 vs. CHO=42.2±11.2 % new in 6-weeks). CONCLUSIONS: Our results suggest that protein consumption following each session of endurance exercise training can lead to long-term changes in aerobic capacity. MPS, DNA%F, or GLY had similar responses to training between PRO and CHO groups. The mean DNA%F of 4% is a novel measure of skeletal muscle DNA synthesis and cannot be accounted for by mitochondrial DNA turnover. These results may indicate satellite cell activation during endurance exercise training in aging adults.

Are Improvements in Physical Fitness after an Exercise Program Related to the Symptomatology in Patients with Fibromyalgia

Problem statement: Physical exercise is considered one of the main strategies in management of Fibromyalgia (FM); While many studies have shown relevant improvements in the patients’ physical condition and psychological status, the efficacy of these treatments have not yet been completely determined and whether or not these improvements are related with symptom severity is still debated. The aim of this study was to evaluate the positive effect of exercise training on physical fitness and second to determine whether any change in aerobic capacity, strengthening or flexibility after exercise training is associated with improvements in symptoms severity of patients with FM. Approach: Thirty women with FM were randomized to either combined exercise group (CE, n = 15) which performed twice-weekly sessions of combined aerobic and resistance exercises, or usual care control group (CG, n = 15). Participants had to complete a Visual Analogue Scale (VAS) for stiffness, sleep disturbances, pain, anxiety and depression. Physical fitness (aerobic capacity, handgrip strength and flexibility) was also assessed at baseline and immediately after 12-week intervention. Results: Aerobic capacity and Range Of Motion (ROM) in both shoulders and in the right hip were significantly greater than controls. Inter-group differences were significant in anxiety and depression. Linear regressions of physical fitness variables and symptomatology showed positive correlations. Conclusions: Physical fitness seems to be related with the improvements in symptom´ severity and due to regular physical activity has demonstrated to be beneficial for individuals with FM it should be included in treatment plans for this patients group.

A genetic predisposition score for muscular endophenotypes predicts the increase in aerobic power after training: the CAREGENE study

BackgroundIt is widely accepted that genetic variability might explain a large part of the observed heterogeneity in aerobic capacity and its response to training. Significant associations between polymorphisms of different genes with muscular strength, anaerobic phenotypes and body composition have been reported. Muscular endophenotypes are positively correlated with aerobic capacity, therefore, we tested the association of polymorphisms in twelve muscular related genes on aerobic capacity and its response to endurance training.Methods935 Coronary artery disease patients (CAD) who performed an incremental exercise test until exhaustion at baseline and after three months of training were included. Polymorphisms of the genes were detected using the invader assay. Genotype-phenotype association analyses were performed using ANCOVA. Different models for a genetic predisposition score (GPS) were constructed based on literature and own data and were related to baseline and response VO2 scores.ResultsCarriers of the minor allele in the R23K polymorphism of the glucocorticoid receptor gene (GR) and the ciliary neurotrophic factor gene (CNTF) had a significantly higher increase in peakVO2 after training (p < 0.05). Carriers of the minor allele (C34T) in the adenosine monophosphate deaminase (AMPD1) gene had a significantly lower relative increase (p < 0.05) in peakVO2. GPS of data driven models were significantly associated with the increase in peakVO2 after training.ConclusionsIn CAD patients, suggestive associations were found in the GR, CNTF and the AMPD1 gene with an improved change in aerobic capacity after three months of training. Additionally data driven models with a genetic predisposition score (GPS) showed a significant predictive value for the increase in peakVO2.

Effects of strength training on endurance capacity in top‐level endurance athletes

The effect of concurrent strength (S) and endurance (E) training on adaptive changes in aerobic capacity, endurance performance, maximal muscle strength and muscle morphology is equivocal. Some data suggest an attenuated cardiovascular and musculoskeletal response to combined E and S training, while other data show unimpaired or even superior adaptation compared with either training regime alone. However, the effect of concurrent S and E training only rarely has been examined in top-level endurance athletes. This review describes the effect of concurrent SE training on short-term and long-term endurance performance in endurance-trained subjects, ranging from moderately trained individuals to elite top-level athletes. It is concluded that strength training can lead to enhanced long-term (>30 min) and short-term (<15 min) endurance capacity both in well-trained individuals and highly trained top-level endurance athletes, especially with the use of high-volume, heavy-resistance strength training protocols. The enhancement in endurance capacity appears to involve training-induced increases in the proportion of type IIA muscle fibers as well as gains in maximal muscle strength (MVC) and rapid force characteristics (rate of force development), while likely also involving enhancements in neuromuscular function.

Wheel running, skeletal muscle aerobic capacity and 1-methyl-1-nitrosourea induced mammary carcinogenesis in the rat

Emerging evidence indicates that intrinsic differences and induced changes in aerobic capacity are probably to play a critical role in the development of chronic diseases like cancer. This study was initiated: (i) to determine how citrate synthase activity, which is routinely used as a marker of aerobic capacity and mitochondrial density in skeletal muscle, was affected by voluntary running on either a motorized activity wheel or a non-motorized free wheel and (ii) to investigate the association between aerobic capacity and the carcinogenic response induced in the mammary gland by intraperitoneal injection of 1-methyl-1-nitrosurea. Overall, wheel running reduced cancer incidence (96 versus 72%, P = 0.0006) and the number of cancers per animal (2.84 versus 1.78, P < 0.0001) and induced citrate synthase activity (276 versus 353 U/mg, P < 0.0001, sedentary control versus wheel running,respectively). Both motorized and free wheel running increased citrate synthase activity (373 +/- 24, 329 +/- 11 and 276 +/- 9 U/mg protein, P < 0.0001) and reduced the average number of cancers per rat (2.84, 1.96 and 1.63, P < 0.01), sedentary control, free wheel and motorized wheel, respectively. However, regression analyses failed to provide evidence of a significant association between citrate synthase activity and either cancer incidence or cancer multiplicity. Citrate synthase activity is a single measure in a complex pathway that determines aerobic capacity. The multifaceted nature of intrinsic and inducible aerobic capacity limits the usefulness of citrate synthase activity alone in elucidating the relationship between aerobic capacity and the carcinogenic response.

Changes in blood pressure with compensatory heart rate decrease and in the level of aerobic capacity in response to repeated whole-body cryostimulation in normotensive, young and physically active men

In Poland and all over the world, whole-body cryostimulation is becoming more and more popular in the treatment of different diseases and in sport. However, changes that occur in the human body subjected to cryogenic temperatures are still not completely understood. Therefore, the aim of this study was to evaluate changes in blood circulation and aerobic capacity induced by repeated exposure to whole-body cryostimulation of young and clinically healthy male subjects. The study included 25 young men, aged 21 ± 0.9 years, average body weight 74.65 ± 6.98 kg and height 179.5 ± 5.12 cm. The participants were exposed to extremely low temperatures in a cryogenic chamber once a day for 15 days. Each session lasted 3 min at -130°C and was preceded by 30-second, adaptation in a vestibule at -60°C. Blood pressure and heart rate were measured before entering the chamber, immediately after exiting and 10 min later. We also calculated pulse pressure and the mean arterial blood pressure. Before and after the treatment the maximal oxygen uptake was measured. Our results showed a significant increase in systolic blood pressure after each cryostimulation (by an average of 19 mmHg) and an increase in diastolic blood pressure only after the first cryostimulation (by 6 mm Hg). The increase in systolic blood pressure was accompanied by a significant decrease in heart rate (by about 7 bpm). No adaptation changes were observed after 15 treatments. There were no changes in aerobic capacity after 15 sessions of WBC, however we observed a significant decrease in RBC and hemoglobin concentration. Due to the increase in systolic blood pressure after WBC, this kind of physiotherapy treatment is not recommended for people with advanced or not pharmacologically controlled hypertension.

Influence of the ten sessionsof the whole body cryostimulationon aerobic and anaerobic capacity

The aim of this study was to determine the influence of whole body cryostimulation on aerobic and anaerobic capacities. To test the hypothesis that whole body cryostimulation improves physical capacity, thirty subjects (fifteen males and fifteen females) undertook two ergocycle trials before and after the ten sessions of cryogenic chamber treatment. To assess baseline aerobic capacity, the progressive cycle ergometer test was applied. This allowed determination of maximal oxygen uptake and ventilatory thresholds. Twenty-second Wingate test was performed to assess baseline levels of anaerobic power. After finishing the treatments in the cryogenic chamber, the exercise protocol was repeated. Before the first, and after the last whole body cryostimulation, venous blood samples were drawn to determine basic blood values, including levels of erythrocytes, leukocytes and thrombocytes, hemoglobin concentration, and hematocrit. There were no changes in aerobic capacity, in both females and males, after ten sessions of 3-minute-long exposures to cryogenic temperature (-130 degrees C). Participation in the whole body cryostimulation caused an increase in maximal anaerobic power in males (from 11.1 to 11.9 W x kg(-1); P < 0.05), but not in females. It can be concluded that whole body cryostimulation can be beneficial, at least in males, for increasing anaerobic capacity in sport disciplines involving speed and strength.

Individualized 12-Week Exercise Training Programs Enhance Aerobic Capacity of Cancer Survivors

Changes in aerobic capacity were evaluated after 12 weeks of training among a motivated heterogeneous group of cancer survivors (N = 54 [41 women and 13 men]), living at moderate altitude. Changes in power at lactate threshold (PTlact), peak power (Ppeak), and peak oxygen uptake (VO2 peak) were evaluated in this group (average age, 53.8 ± 10.8 years) that completed a minimum of 12 weeks of an individualized exercise program (on average 5 days•week-1 for 47.5 ± 17.2 min•session-1). Daily exercise duration was based on the goals and functional capacity of each individual. Training intensity for each subject was based on heart rate (HR) value at lactate threshold (Tlact) obtained during a symptom-limited cardiopulmonary exercise test. Intensity was categorized into 5 ranges: recovery (60%–80% HR Tlact); endurance (80%–100% HR Tlact); threshold (100%–105% HR Tlact); intervals (105%–115% HR Tlact); and maximal efforts (≥ 115% HR Tlact). Overall compliance with the exercise prescription was ˜72% and subjects reported exercising within the 5 training ranges, 12.1%, 63.9%, 18.6%, 4.2%, and 1.2% of the time, respectively. After training, PTlact increased 9.5% (121.8 ± 43.5 vs 133.2 ± 34.1 W; P < 0.05), Ppeak increased 12.6% (175.5 ± 55.6 vs 195.6 ± 54.2 W; P < 0.05) and VO2 peak increased 11.4% (33.4 ± 12.5 vs 37.2 ± 10.4 mL•kg-1•min-1; P < 0.05). The results of this research indicate that: 1) cardiopulmonary exercise testing with lactate threshold determination was safe and effective in the evaluation and exercise prescription phase for a group of cancer survivors and 2) a training program based on 2 higher intensity workouts per week can elicit significant changes in aerobic capacity of a diverse group of cancer survivors.

Short-term exercise training improves aerobic capacity with no change in arterial function in obesity

The aim of the study is to determine the effects of short-term high-intensity exercise on arterial function and glucose tolerance in obese individuals with and without the metabolic syndrome (MetSyn). Obese men and women (BMI > 30 kg/m(2); 39-60 years) with and without MetSyn (MetSyn, n = 13; Non-MetSyn, n = 13) participated in exercise training consisting of ten consecutive days of treadmill walking for 1 h/day at 70-75% of peak aerobic capacity. Changes in aerobic capacity, flow-mediated dilation (FMD), and arterial stiffness using central and peripheral pulse wave velocity (PWV) measurements were assessed pre- and post-training. These measurements were obtained fasting and 1-h post-test meal while the subjects were hyperglycemic. Aerobic capacity improved for both groups [Non-MetSyn 24.0 +/- 1.6 vs. 25.1 +/- 1.5 mL/(kg min); MetSyn 25.2 +/- 1.8 vs. 26.2 +/- 1.7 mL/(kg min), P < 0.05]. There was no change in body weight. FMD decreased by ~20% (P < 0.05) for both groups during acute hyperglycemia (MetSyn, n = 11; Non-MetSyn, n = 10), while hyperglycemia increased central PWV and not peripheral PWV. Exercise training did not change FMD in the fasted or challenged state. Central and peripheral PWV were not altered with training for either group (MetSyn, n = 13; Non-MetSyn, n = 13). A 10-day high-intensity exercise program in obese individuals improved aerobic capacity and glucose tolerance but no change in arterial function was observed. Acute hyperglycemia had a deleterious effect on arterial function, suggesting that persons with impaired glucose homeostasis may experience more opportunities for attenuated arterial function on a daily basis which could contribute to increased cardiovascular risk.

Heart Rate Dynamics after Combined Endurance and Strength Training in Older Men

Aging alters cardiac autonomic function, which may contribute to a higher risk of cardiac events. Spectral measures of HR variability (HRV) and fractal-like behavior of HR are considered as markers of a healthy heart. The present study examined the effects of combining endurance and strength training compared with endurance or strength training alone on HR dynamics and physical fitness in older previously untrained men aged 40-67 yr. Subjects were randomized into endurance training (E, n = 23), strength training (S, n = 25), combined endurance and strength training (ES, n = 29), or control group (C, n = 16). Short-term fractal scaling exponent (alpha1) and spectral HRV were analyzed from maximal aerobic cycling tests and during supine rest, and leg extension one repetition maximum strength was measured. Aerobic capacity and maximal strength increased in the training groups performing endurance and/or strength training, respectively. Only ES showed a decrease after training in fractal HR behavior during exercise, and the difference was significant between groups (P = 0.019). During supine rest, alpha1 only decreased significantly (P = 0.039) in ES from 1.18 (SD = 0.20) to 1.11 (SD = 0.21). The decrease in alpha1 at rest from 1.21 (SD = 0.19) to 1.11 (SD = 0.22) also approached significance (P = 0.061) in E. Changes in spectral measures of HRV were minor during the study period and only occurred during exercise. Fractal HR dynamics were improved more by combining strength training with endurance training in our older men compared with endurance training alone, although strength training alone produced no changes in fractal HR behavior. The synergistic effect in fractal HR behavior occurred regardless of changes in aerobic capacity.

Systematic analysis of adaptations in aerobic capacity and submaximal energy metabolism provides a unique insight into determinants of human aerobic performance

It has not been established which physiological processes contribute to endurance training-related changes (Delta) in aerobic performance. For example, the relationship between intramuscular metabolic responses at the intensity used during training and improved human functional capacity has not been examined in a longitudinal study. In the present study we hypothesized that improvements in aerobic capacity (Vo(2max)) and metabolic control would combine equally to explain enhanced aerobic performance. Twenty-four sedentary males (24 +/- 2 yr; 1.81 +/- 0.08 m; 76.6 +/- 11.3 kg) undertook supervised cycling training (45 min at 70% of pretraining Vo(2max)) 4 times/wk for 6 wk. Performance was determined using a 15-min cycling time trial, and muscle biopsies were taken before and after a 10-min cycle at 70% of pretraining Vo(2max) to quantify substrate metabolism. Substantial interindividual variability in training-induced adaptations was observed for most parameters, yet "low responders" for DeltaVo(2max) were not consistently low responders for other variables. While Vo(2max) and time trial performance were related at baseline (r(2) = 0.80, P < 0.001), the change in Vo(2max) was completely unrelated to the change in aerobic performance. The maximal parameters DeltaVe(max) and DeltaVeq(max) (DeltaVe/Vo(2max)) accounted for 64% of the variance in DeltaVo(2max) (P < 0.001), whereas Deltaperformance was related to changes in the submaximal parameters Veq(submax) (r(2) = 0.33; P < 0.01), muscle Deltalactate (r(2) = 0.32; P < 0.01), and Deltaacetyl-carnitine (r(2) = 0.29; P < 0.05). This study demonstrates that improvements in high-intensity aerobic performance in humans are not related to altered maximal oxygen transport capacity. Altered muscle metabolism may provide the link between training stimulus and improved performance, but metabolic parameters do not change in a manner that relates to aerobic capacity changes.