Submaximal Exercise Intensities Research Articles

Short-term pre-operative high-intensity interval training does not improve fitness of colorectal cancer patients.

BackgroundPre‐operative cardiorespiratory fitness (CRF) in colorectal cancer (CRC) patients has been shown to affect post‐operative outcomes. The aim of this study was to test the feasibility of high‐intensity interval training (HIIT) for improving fitness in pre‐operative CRC patients within the 31‐day cancer waiting‐time targets imposed in the UK.MethodsEighteen CRC patients (13 males, mean age: 67 years (range: 52‐77 years) participated in supervised HIIT on cycle ergometers 3 or 4 times each week prior to surgery. Exercise intensity during 5 × 1‐minute HIIT intervals (interspersed with 90‐second recovery) was 100%‐120% maximum wattage achieved at a baseline cardiopulmonary exercise test (CPET). CPET before and after HIIT was used to assess CRF.ResultsPatients completed a mean of eight HIIT sessions (range 6‐14) over 19 days (SD 7). There was no significant increase in VO2 peak (23.9 ± 7.0 vs 24.2 ± 7.8 mL/kg/min (mean ± SD), P = 0.58) or anaerobic threshold (AT: 14.0 ± 3.4 vs 14.5 ± 4.5 mL/kg/min, P = 0.50) after HIIT. There was a significant reduction in resting systolic blood pressure (152 ± 19 vs 142 ± 19 mm Hg, P = 0.0005) and heart rate at submaximal exercise intensities after HIIT.ConclusionsOur pragmatic HIIT exercise protocol did not improve the pre‐operative fitness of CRC patients within the 31‐day window available in the UK to meet cancer surgical waiting‐time targets.

Caloric Regulation Linked Thermogenesis in Acute Submaximal Intensity Exercise Model as The Effect of Audio Frequency Exposure

Thermogenesis is an essential physiological mechanism in both bodies thermal and energy balance. Thermal balance is significantly associated with body heat homeostasis linked thermogenesis-caloric regulation. The caloric or energy balance was reported under facultative thermogenesis within skeletal muscle stimulated by exercise. Importantly, decreased energy expenditure, imbalance energy intake, and loss of energy was developed for types of obesity. Recently, music tempo and frequency are proposed as the new raw model of exercise treatment against the progression of overweight in the population. Thus, our preliminary pre-post test randomized study aimed to investigate the physical-physiological connection between thermogenesis, caloric regulation, acute- maximal and submaximal intensity exercise model and musical frequency/tempo on the body thermal homeostasis and physiological performance in the younger athlete. This study involved 45 participants with homogeneity in age, height, weight, heartbeat, and physical fitness. Interestingly, co-treatment high intensity, moderate intensity exercise and moderate intensity exercise with middle musical tempo/frequency decreased body temperature without relevant alteration on caloric production. Furthermore, this exercise model significantly induced caloric production and energy expenditure in a similar pattern with the placebo. Also, musical-moderate intensity exercise exposure enhanced muscle thermogenesis without effect to overheat condition during the treatment. The circulating level of physiological-physical stress marker (cortisol) significantly decreased post musical exposure. Hence, the development of physical combination therapy for individual onset obesity progress to metabolic syndrome can contribute to the prevention of metabolic disease. This combination model may offer an alternative solution to combating overweight and obesity through musical-exercise co-treatment. However, further studies are emerging to widely establish this model for global communities.

The Impact of Cycling Cadence on Respiratory and Hemodynamic Responses to Exercise.

The physiological consequences of freely chosen cadence during cycling remains poorly understood. We sought to determine the effect of cadence on the respiratory and hemodynamic response to cycling exercise. Eleven cyclists (10 males, 1 female; age, 27 ± 6 yr; V˙O2max = 60.8 ± 3.7 mL·kg·min) completed four, 6-min constant-load cycling trials at 10% below their previously determined gas exchange threshold (i.e., 63% ± 5% peak power) while pedaling at 60, 90, and 120 rpm, and a freely chosen cadence (94.3 ± 6.9 rpm) in randomized order. Standard cardiorespiratory parameters were measured and an esophageal electrode balloon catheter was used to assess electromyography of the diaphragm (EMGdi) and the work of breathing (Wb). Leg blood flow index (BFI) was determined on four muscles using near-infrared spectroscopy with indocyanine green dye injections. Oxygen uptake (V˙O2) increased as a function of increasing cadence (all pairwise comparisons, P < 0.05). The EMGdi and Wb were significantly greater at 120 rpm compared with all other conditions (all P < 0.01). Vastus medialis and semitendinosus BFI were significantly greater at 120 rpm compared with 60 and 90 rpm (all P < 0.05). Gastrocnemius BFI was higher at 120 rpm compared with all other cadences (all P < 0.01). No difference in BFI was found in the vastus lateralis (P = 0.06). Blood flow index was significantly correlated with the increase in V˙O2 with increasing cadence in the medial gastrocnemius (P < 0.001) and approached significance in the vastus lateralis (P = 0.09), vastus medialis (P = 0.06), and semitendinosus (P = 0.09). There was no effect of cadence on Borg 0-10 breathing or leg discomfort ratings (P > 0.05). High cadence cycling at submaximal exercise intensities is metabolically inefficient and increases EMGdi, Wb, and leg muscle blood flow relative to slower cadences.

Increasing Iron Status through Dietary Supplementation in Iron-Depleted, Sedentary Women Increases Endurance Performance at Both Near-Maximal and Submaximal Exercise Intensities

Iron deficiency persists as the most common micronutrient deficiency globally, despite having known detrimental effects on physical performance. Although iron supplementation and aerobic exercise have been examined individually and are known to improve physical performance, the impact of simultaneous iron supplementation and aerobic training remains unclear. The aim of this study was to examine the individual and combined effects of iron supplementation and aerobic training on improving maximal and submaximal physical performance in iron-depleted, nonanemic (IDNA) women. We hypothesized that women receiving iron would improve their endurance performance but not their estimated maximal oxygen consumption (eVO2max). Seventy-three sedentary, previously untrained IDNA (serum ferritin <25 µg/L and hemoglobin >110 g/L) women aged 18-26 y with a body mass index (kg/m2) of 17-25 participated in a double-blind, 8-wk, randomized controlled trial with a 2×2 factorial design including iron supplementation (42 mg elemental Fe/d) or placebo and aerobic exercise training (5 d/wk for 25 min at 75-85% of age-predicted maximum heart rate) or no training. Linear models were used to examine relations between training, supplement, and changes in the primary outcomes of observed maximal oxygen consumption (VO2peak) and eVO2max and ventilatory threshold (absolute oxygen consumption and percentage of maximum). Re-evaluation of a published meta-analysis was used to compare effects of iron supplementation on maximal oxygen consumption (VO2max) and VO2peak. There were significant training-by-supplement interactions for VO2peak, volume of oxygen consumption at the ventilatory threshold, and the percentage of eVO2max where the threshold occurred, with the iron-untrained group performing better than the placebo-untrained group. There was no beneficial effect of iron supplementation for VO2max (mean difference: 0.53; 95% CI: -0.75, 1.81; P=0.42), but a significant benefit was observed for VO2peak (mean difference: 1.87; 95% CI: 0.15, 3.60; P=0.03). Iron supplementation increases endurance performance at submaximal and maximal (VO2peak) exercise intensities in IDNA women. However, increasing iron status does not increase eVO2max. This trial was registered at clinicaltrials.gov as NCT03002090.

Renal function during exercise and recovery

This review paper analyzes the response of renal function during two types of exercise: 1) exercise of increasing intensity and 2) exercise of submaximal intensity and prolonged duration. During an effort of increasing intensity there is a decrease in renal blood flow that, theoretically, could compromise renal function. However, several studies seem to show that the kidney has self-regulatory mechanisms that allow maintaining the filtration fraction. On the other hand, ultra resistance exercises, such as ironman, are becoming more frequent. Knowing the renal response to this type of exercise is essential to apply knowledge to emergency situations such as dehydration or hyponatremia.

Effect of a four-week ketogenic diet on exercise metabolism in CrossFit-trained athletes

BackgroundThe ketogenic diet is becoming a popular nutritional model among athletes. However, the relationship between its use and metabolism during exercise seems to have not been fully investigated.MethodsThe aim of the study was to assess the effects of a four-week ketogenic diet (KD) on fat and carbohydrate (CHO) utilization during an incremental cycling test (ICT) in CrossFit-trained female (n = 11) and male (n = 11) athletes. During the ICT (while consuming the customary diet and after the KD), oxygen uptake and carbon dioxide exhalation were registered, and CHO and fat utilization as well as energy expenditure were calculated.ResultsIn males, the KD led to an increase in fat utilization (g·min− 1·kgFFM− 1 and % oxidation). It was particularly noticeable at exercise intensities up to 80% of VO2max. An increase in the area under the curve (AUC) was seen in males but not in females at up to ≤65% VO2max of fat utilization.ConclusionsMale CrossFit-trained athletes seem to be more prone to shifts in macronutrient utilization (in favor of fat utilization) during submaximal intensity exercise under a ketogenic diet than are female athletes.Trial registrationClinical Trials Gov, NCT03665948. Registered 11 September 2018 (retrospectively registered).

Measuring V̇O2 in hypoxic and hyperoxic conditions using dynamic gas mixing with a flow-through indirect calorimeter.

ABSTRACTMeasurements of gas exchange while breathing gases of different O2 concentrations are useful in respiratory and exercise physiology. High bias flows required in flow-through indirect calorimetry systems for large animals like exercising horses necessitate the use of inconveniently large reservoirs of mixed gases for making such measurements and can limit the amount of equilibration time that is adequate for steady-state measurements. We obviated the need to use a pre-mixed reservoir of gas in a semi-open flow-through indirect calorimeter by dynamically mixing gases and verified the theoretical accuracy and utility of making such measurements using the mass-balance N2-dilution method. We evaluated the accuracy of the technique at different inspired oxygen fractions by measuring exercising oxygen consumption (V̇O2) at two fully aerobic submaximal exercise intensities in Thoroughbred horses. Horses exercised at 24% and 50% maximum oxygen consumption (V̇O2 max) of each horse while breathing different O2 concentrations (19.5%, 21% and 25% O2). The N2-dilution technique was used to calculate V̇O2. Repeated-measures ANOVA was used to tested for differences in V̇O2 between different inspired O2 concentrations. The specific V̇O2 of the horses trotting at 24%V̇O2max and cantering at 50%V̇O2max were not significantly different among the three different inspired oxygen fractions. These findings demonstrate that reliable measurements of V̇O2 can be obtained at various inspired oxygen fractions using dynamic gas mixing and the N2-dilution technique to calibrate semi-open-circuit gas flow systems.

Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans.

Regular physical activity has a positive effect on human health, but the mechanisms controlling these effects remain unclear. The physiologic and biologic responses to acute exercise are predominantly influenced by the duration and intensity of the exercise regimen. As exercise is increasingly thought of as a therapeutic treatment and/or diagnostic tool, it is important that standardizable methodologies be utilized to understand the variability and to increase the reproducibility of exercise outputs and measurements of responses to such regimens. To that end, we describe two different cycling exercise regimens that yield different physiologic outputs. In a maximal exercise test, exercise intensity is continually increased with a greater workload resulting in an increasing cardiopulmonary and metabolic response (heart rate, stroke volume, ventilation, oxygen consumption and carbon dioxide production). In contrast, during endurance exercise tests, the demand is increased from that at rest, but is raised to a fixed submaximal exercise intensity resulting in a cardiopulmonary and metabolic response that typically plateaus. Along with the protocols, we provide suggestions on measuring physiologic outputs that include, but are not limited to, heart rate, slow and forced vital capacity, gas exchange metrics, and blood pressure to enable the comparison of exercise outputs between studies. Biospecimens can then be sampled to assess cellular, protein, and/or gene expression responses. Overall, this approach can be easily adapted into both short- and long-term effects of two distinct exercise regimens.

PO-246 Effects of Different Methods of Precooling on Sub-maximal Intensity Exercise in Heat and High Humidity

Objective This study aimed to investigate the influence of using different precooling measures on the capacity of competition and the exercise performance in hot and humidity environment. The most effectual means of precooling will be recommended to help coaches and athletes to improve the ability and performance in training and matches&#x0D; Methods Ten male football (Rugby) players who came from the rugby team totally completed four experimental conditions in hot/humid conditions (38℃, 50% humidity). Initially, a 30-min precooling period consisting of either nothing to control (CONT, C); wearing cooling vest (4℃, V); ingesting of ice beverage (2.3 ml /kg of 4℃, I); or the mix method of combination of V and I (V+I, M). Following this, sub-maximal exercise (80% VO2max) of treadmill test occurred, until athletes exhausted&#x0D; Results The running distance of M and V and I have a significant increase (P≤0.05) than CONT. The peak oxygen uptake of exhaustion was no significant difference between each other. After exercise, the change rate of heart rate ratio of M compared with CONT has a very significant decrease (P≤0.01). The core temperature of M and CONT has a significant increase (P≤0.05) in comparison. The surface temperature of I and M and V comparison with CONT has a very significant increase (P≤0.01). When participants exhaust, the RPE of M in comparison with CONT had significantly lower (P≤0.05). The RPB and the rating of thermal sensation of each condition were no significant difference. After exercise, the blood lactic concentration of each ones was no significant difference&#x0D; Conclusions In hot and humidity condition, precooling has a promoting effect on the sub-maximal exercise. Precooling measures could improve the exercise performance and maintain the stability of functional status and physiology, especially the mix method.&#x0D;

Left ventricular function during exercise in trained pre-adolescent soccer players.

It is unclear, what the underlying cardiovascular mechanisms are that give rise to the high level of aerobic fitness seen in youth soccer players. The aim of the study was to evaluate global and regional markers of systolic and diastolic function in a group of pre-adolescent soccer players during an incremental exercise test. Twenty-two, male soccer players (SP) from two professional soccer clubs (age: 12.0±0.3years) volunteered for the study. Fifteen recreationally active boys (CON), of similar age (age: 11.7±0.2years) were also recruited. All boys underwent a cycle ergometer test to exhaustion. Cardiac dimensions were determined using M-mode echocardiography. During submaximal and maximal exercise, continuous-wave Doppler ultrasound techniques were used to derive stroke volume (SVIndex). Tissue-Doppler imaging was used to quantify systolic (S'adj) and diastolic function (E; E'adj and E/E') at rest and both submaximal and maximal exercise intensities. Speckle tracking echocardiography was used to determine peak longitudinal ε at submaximal exercise intensities. SP demonstrated significantly (P≤0.05) greater peak VO2 values than CON (SP: 48.0±5.0 vs CON: 40.1±7.5mL/kg/min). Allometrically scaled to body surface area left ventricular end-diastolic volume (LVEDV) was larger (P≤0.05) in the SP (51.3±9.0) compared to CON (44.6±5.8mL·BSA1.5 ). At the same relative, submaximal exercise intensities, the SP demonstrated greater SVIndex, cardiac output (QIndex), and E. No differences were noted for peak longitudinal ε during submaximal exercise. Factors that augment pre-load and LV volume appear to determine the superior aerobic fitness seen in the soccer players.

Influence of Cardio-Respiratory Fitness on Physical Performance in Elite Youth Soccer

The purpose of this study was to assess the relationship between: Peak oxygen uptake (VO2max) and running economy (RE) with physical measures associated with elite youth soccer performance obtained during soccer match-play. Seventeen highly trained youth soccer players (age: 13.3±0.4y) volunteered to participate. Initially player’s ventilatory threshold (VT) and VO2max was established using a treadmill protocol. On the subsequent visit, players ran for 4 min, at three different speeds (8km/h, 80%VT and 95%VT). Physical soccer-based performance was assessed using a maximal Yo-Yo IR1 and via Global positioning systems (GPS) derived variables obtained during three, 2x20min, 11 v 11 soccer matches. Partial correlations revealed significant relationships between relative VO2max and measures of physical soccer performance (r = 0.54–0.88). Moreover, measures of ventilatory equivalent (VEVO2), a determinant of RE, at all sub-maximal exercise intensities were inversely related to the volume (m) and percentage (%) of very high intensity activities. Current findings emphasise the need for high levels of cardio-respiratory fitness in high level youth soccer players, with superior levels of fitness being associated with a greater amount of high and very high intensity activity during soccer match-play.

High-intensity interval training in overweight and obese children and adolescents: systematic review and meta-analysis.

While High Intensity Interval Training is praised in many populations for its beneficial effects on body composition and cardiometabolic health, its use among obese youth remain uncertain. This study aimed at determining whether HIIT is effective to improve aerobic fitness and reduce cardiometabolic risk factors in overweight and obese youth. A systematic search was conducted and articles reporting studies that investigated the effects of HIIT in 6 to 18-year-old youth were eligible. Meta-analyses were performed when appropriate. Fifteen studies were included for the systematic review and meta-analyses. HIIT significantly improves maximal oxygen uptake (1.117 [95% CI: 0.528 to 1.706], P<0.001), and reduces body mass (-0.295 [95% CI: -0.525 to -0.066], P<0.05), body fat (-0.786 [95% CI: -1.452 to -0.120], P<0.05), systolic and diastolic blood pressure (-1.026 [95% CI: -1.370 to -0.683], P<0.001; -0.966 [95% CI: -1.628 to -0.304], P<0.01 respectively), and the HOMA-IR (-1.589 [95% CI: -2.528 to -0.650], P<0.01). However, there is significant heterogeneity, and low to high inconsistency for most cardiometabolic risk factors and aerobic fitness. Although few studies have reported cardiometabolic risks, HIIT may also be as effective as traditional endurance continuous training to decrease blood pressure and insulin resistance. HIIT is effective to improve aerobic fitness, body composition, and cardiometabolic risk factors in obese youth, but data are insufficient to determine whether it is more effective than traditional continuous submaximal intensity exercise training.

Fat max as an index of aerobic exercise performance in mice during uphill running

Endurance exercise performance has been used as a representative index in experimental animal models in the field of health sciences, exercise physiology, comparative physiology, food function or nutritional physiology. The objective of the present study was to evaluate the effectiveness of Fatmax (the exercise intensity that elicits maximal fat oxidation) as an additional index of endurance exercise performance that can be measured during running at submaximal exercise intensity in mice. We measured both Fatmax and Vo2 peak of trained ICR mice that voluntary exercised for 8 weeks and compared them with a sedentary group of mice at multiple inclinations of 20, 30, 40, and 50° on a treadmill. The Vo2 at Fatmax of the training group was significantly higher than that of the sedentary group at inclinations of 30 and 40° (P < 0.001). The running speed at Fatmax of the training group was significantly higher than that of the sedentary group at inclinations of 20, 30, and 40° (P < 0.05). Blood lactate levels sharply increased in the sedentary group (7.33 ± 2.58 mM) compared to the training group (3.13 ± 1.00 mM, P < 0.01) when running speeds exceeded the Fatmax of sedentary mice. Vo2 at Fatmax significantly correlated to Vo2 peak, running time to fatigue, and lactic acid level during running (P < 0.05) although the reproducibility of Vo2 peak was higher than that of Vo2 at Fatmax. In conclusion, Fatmax can be used as a functional assessment of the endurance exercise performance of mice during submaximal exercise intensity.

Do interindividual differences in cardiac output during submaximal exercise explain differences in exercising muscle oxygenation and ratings of perceived exertion?

Considerable interindividual differences in the Q˙−V˙O2 relationship during exercise have been documented but implications for submaximal exercise tolerance have not been considered. We tested the hypothesis that these interindividual differences were associated with differences in exercising muscle deoxygenation and ratings of perceived exertion (RPE) across a range of submaximal exercise intensities. A total of 31 (21 ± 3 years) healthy recreationally active males performed an incremental exercise test to exhaustion 24 h following a resting muscle biopsy. Cardiac output (Q˙ L/min; inert gas rebreathe), oxygen uptake (V˙O2 L/min; breath‐by‐breath pulmonary gas exchange), quadriceps saturation (near infrared spectroscopy) and exercise tolerance (6–20; Borg Scale RPE) were measured. The Q˙−V˙O2 relationship from 40 to 160 W was used to partition individuals post hoc into higher (n = 10; 6.3 ± 0.4) versus lower (n = 10; 3.7 ± 0.4, P < 0.001) responders. The Q˙−V˙O2 difference between responder types was not explained by arterial oxygen content differences (P = 0.5) or peripheral skeletal muscle characteristics (P from 0.1 to 0.8) but was strongly associated with stroke volume (P < 0.05). Despite considerable Q˙−V˙O2 difference between groups, no difference in quadriceps deoxygenation was observed during exercise (all P > 0.4). Lower cardiac responders had greater leg (P = 0.027) and whole body (P = 0.03) RPE only at 185 W, but this represented a higher %peak V˙O2 in lower cardiac responders (87 ± 15% vs. 66 ± 12%, P = 0.005). Substantially lower Q˙−V˙O2 in the lower responder group did not result in altered RPE or exercising muscle deoxygenation. This suggests substantial recruitment of blood flow redistribution in the lower responder group as part of protecting matching of exercising muscle oxygen delivery to demand.

Blood Pressure Response to Exercise and Cardiovascular Disease.

This review aimed to provide a clinical update on exercise blood pressure (BP) and its relationship to cardiovascular disease (CVD), outlining key determinants of abnormal exercise BP responses. We also highlight current evidence gaps that need addressing in order to optimise the relevance of exercise BP as clinical CVD risk factor. Abnormal exercise BP manifests as either exercise hypotension (low BP response) or as exaggerated exercise BP (high BP response). Exercise hypotension is an established sign of existing and likely severe CVD, but exaggerated exercise BP also carries elevated CVD risk due to its association with sub-clinical hypertension. Although exaggerated exercise BP is related to heightened CVD risk at any exercise intensity, recent data suggest that the BP response to submaximal intensity exercise holds greater prognostic and clinical significance than BP achieved at peak/maximal intensity exercise. Cardiorespiratory fitness is a strong modifier of the exercise BP response, and should be taken into consideration when assessing the association with CVD. Both exercise hypotension and exaggerated exercise BP serve as markers that should prompt evaluation for potential underlying CVD. However, the clinical utility of these markers is currently inhibited by the lack of consensus informing the definitions and thresholds for abnormalities in exercise BP.

The effects of acute carbohydrate and caffeine feeding strategies on cycling efficiency

ABSTRACTTo assess the effect of carbohydrate and caffeine on gross efficiency (GE), 14 cyclists (V̇O2max 57.6 ± 6.3 ml.kg−1.min−1) completed 4 × 2-hour tests at a submaximal exercise intensity (60% Maximal Minute Power). Using a randomized, counter-balanced crossover design, participants consumed a standardised diet in the 3-days preceding each test and subsequently ingested either caffeine (CAF), carbohydrate (CHO), caffeine+carbohydrate (CAF+CHO) or water (W) during exercise whilst GE and plasma glucose were assessed at regular intervals (~30 mins). GE progressively decreased in the W condition but, whilst caffeine had no effect, this was significantly attenuated in both trials that involved carbohydrate feedings (W = −1.78 ± 0.31%; CHO = −0.70 ± 0.25%, p = 0.008; CAF+CHO = −0.63 ± 0.27%, p = 0.023; CAF = −1.12 ± 0.24%, p = 0.077). Blood glucose levels were significantly higher in carbohydrate ingestion conditions (CHO = 4.79 ± 0.67 mmol·L−1, p < 0.001; CAF+CHO = 5.05 ± 0.81 mmol·L−1, p < 0.001; CAF = 4.46 ± 0.75 mmol·L−1; W = 4.20 ± 0.53 mmol·L−1). Carbohydrate ingestion has a small but significant effect on exercise-induced reductions in GE, indicating that cyclists’ feeding strategy should be carefully monitored prior to and during assessment.

Assessment of Metabolic Flexibility by Means of Measuring Blood Lactate, Fat, and Carbohydrate Oxidation Responses to Exercise in Professional Endurance Athletes and Less-Fit Individuals.

Increased muscle mitochondrial mass is characteristic of elite professional endurance athletes (PAs), whereas increased blood lactate levels (lactatemia) at the same absolute submaximal exercise intensities and decreased mitochondrial oxidative capacity are characteristics of individuals with low aerobic power. In contrast to PAs, patients with metabolic syndrome (MtS) are characterized by a decreased capacity to oxidize lipids and by early transition from fat to carbohydrate oxidation (FATox/CHOox), as well as elevated blood lactate concentration [La-] as exercise power output (PO) increases, a condition termed 'metabolic inflexibility'. The aim of this study was to assess metabolic flexibility across populations with different metabolic characteristics. We used indirect calorimetry and [La-] measurements to study the metabolic responses to exercise in PAs, moderately active individuals (MAs), and MtS individuals. FATox was significantly higher in PAs than MAs and patients with MtS (p<0.01), while [La-] was significantly lower in PAs compared with MAs and patients with MtS. FATox and [La-] were inversely correlated in all three groups (PA: r=-0.97, p<0.01; MA: r=-0.98, p<0.01; MtS: r=-0.92, p<0.01). The correlation between FATox and [La-] for all data points corresponding to all populations studied was r=-0.76 (p<0.01). Blood lactate accumulation is negatively correlated with FATox and positively correlated with CHOox during exercise across populations with widely ranging metabolic capabilities. Because both lactate and fatty acids are mitochondrial substrates, we believe that measurements of [La-] and FATox rate during exercise provide an indirect method to assess metabolic flexibility and oxidative capacity across individuals of widely different metabolic capabilities.

Oral versus Nasal Breathing during Moderate to High Intensity Submaximal Aerobic Exercise

Introduction: When comparing oral breathing versus nasal breathing, a greater volume of air can be transported through the oral passageway but nasal breathing may also have benefits at submaximal exercise intensities. Purpose: The purpose of this study was to determine breathing efficiency during increasing levels of submaximal aerobic exercise. Methods: Nineteen individuals (males N=9, females N=10) completed a test for maximal oxygen consumption (VO2max) and on separate days 4-min treadmill runs at increasing submaximal intensities (50%, 65%, and 80% of VO2max) under conditions of oral breathing or nasal breathing. Respiratory (respiration rate [RR], pulmonary ventilation [VE]), metabolic (oxygen consumption [VO2], carbon dioxide production [VCO2]) and efficiency measures (ventilatory equivalents for oxygen [Veq×O2-1] and carbon dioxide [Veq×CO2-1] were obtained. Data were analyzed utilizing a 2 (sex) x 2 (condition) x3 (intensity) repeated measures ANOVA with significance accepted at p≤0.05. Results: Significant interactions existed between breathing mode and intensity such that oral breathing resulted in greater RR, VE, VO2, and VCO2 at all three submaximal intensities (p&lt;.05). Veq×O2-1 and Veq×CO2-1 presented findings that nasal breathing was more efficient than oral breathing during the 65% and 80% VO2max intensities (p&lt;0.05). Conclusion: Based on this analysis, oral breathing provides greater respiratory and metabolic volumes during moderate and moderate-to-high submaximal exercise intensities, but may not translate to greater respiratory efficiency. However when all variables are considered together, it is likely that oral breathing represents the more efficient mode, particularly at higher exercise intensities.

Influence of Dietary Acid Load on Exercise Performance.

Diet composition can affect systemic pH and acid-base regulation, which may in turn influence exercise performance. An acidic environment in the muscle impairs performance and contributes to fatigue; therefore, current trends in sports nutrition place importance on maximizing the alkalinity of the body with ergogenic aids and dietary strategies. This review examines the evidence on the effects of dietary manipulations on acid load and exercise performance. Ten studies that investigated the effect of high versus low dietary acid loads on athletic performance generally identified that low dietary acid loads increased plasma pH, but did not consistently improve exercise performance at maximal or submaximal exercise intensities. In addition, the few studies conducted have several limitations including lack of female subjects and use of exercise tests exclusive to cycling or treadmill running. Although the research does not strongly support a performance benefit from low dietary acid loads, a more alkaline dietary pattern may be beneficial for overall health, as dietary induced acidosis has been associated with greater risk of cardiovascular disease and bone disease. The review includes dietary recommendations for athletes to reduce dietary acid load while still meeting sports nutrition recommendations.

Effects of various acute hypoxic conditions on the hemorheological response during exercise and recovery1.

Even though exercise hemorheology at hypoxic condition has been considered as a good tool to understand clinical hemorheology, there have been limited studies reported. Previous researches showed that hemorheological variables are closely correlated with oxygen delivery capacity during exercise. The present study investigated hypoxic responses including RBC deformability and aggregation, metabolic parameters and complete blood cell counts at various hypoxic conditions during cycling exercise and recovery. Eleven Korean healthy male subjects performed submaximal bike exercise at sea level (20.9% O2) and under various hypoxic conditions (16.5% O2, 14.5% O2, 12.8% O2, and 11.2% O2) in a random order. The submaximal bike exercise intensity of the subjects was 70% maximum heart rate at sea level. All variables were measured at rest, during exercise and recovery 30-minute, respectively. As oxygen partial pressure decreased, arterial blood oxygen saturation decreased but oxygen uptake did not change much. Heart rate and lactate concentration during exercise increased when oxygen partial pressure is less than or equal to 14.5% O2 condition. Red blood cell (RBC) counts, hemoglobin counts, and hematocrit level were not apparently altered with hypoxic conditions. RBC deformability showed significant alterations at 11.2% O2 conditions compared with other hypoxic conditions during exercise or recovery, except at 10 minutes recovery. However, decreases in oxygen partial pressure did not affect red blood cell aggregation. Therefore, we conclude that alterations in RBC deformability may reduce aerobic capabilities at hypoxic condition.