Incremental Cycle Exercise Research Articles

The ratio of heart rate to heart rate variability reflects sympathetic activity during incremental cycling exercise

ABSTRACT A low-frequency to a high-frequency component ratio (LF/HF) in heart rate variability (HRV) may not accurately reflect sympathetic nervous activity during exercise. Thus, a valid HRV-based index of sympathetic nervous activity is needed. Therefore, the heart rate to LF ratio (Heart rate/LF) was evaluated as sympathetic nervous activity index which is reflected by catecholamine levels during incremental exercise. In this study, 15 healthy adults performed an incremental exercise test using a cycle ergometer. HRV was derived from electrocardiography and HRV components related to the autonomic nervous system were obtained using frequency analysis. Heart rate/LF was calculated using the heart rate and LF component produced by HRV analysis. Catecholamine, blood lactate levels and respiratory gas were also measured throughout the exercise test. While LF/HF did not increase with increasing exercise intensity, Heart rate/LF non-linearly increased during the incremental exercise test, as did noradrenaline and blood lactate. Interestingly, Heart rate/LF values were positively correlated with noradrenaline (ρ = 0.788, p < 0.05) and blood lactate (ρ = 0.802, p < 0.05) levels and carbon dioxide production (ρ = 0.903, p < 0.05) from at rest through the exercise stages. Heart rate/LF reflects sympathetic nervous activity and metabolic responses during incremental cycling exercise and has potential as an HRV index of sympathetic nervous activity during exercise. Trial registration: UMIN Japan identifier: UMIN000039639..

Sub-Minute Analysis of Lactate from a Single Blood Drop Using Capillary Electrophoresis with Contactless Conductivity Detection in Monitoring of Athlete Performance.

A simple and fast method for the analysis of lactate from a single drop of blood was developed. The finger-prick whole blood sample (10 µL) was diluted (1:20) with a 7% (w/v) solution of [tris(hydroxymethyl)methylamino] propanesulfonic acid and applied to a blood plasma separation device. The device accommodates a membrane sandwich composed of an asymmetric polysulfone membrane and a supporting textile membrane that allows the collection of blood plasma into a narrow glass capillary in less than 20 s. Separated and simultaneously diluted blood plasma was directly injected into a capillary electrophoresis instrument with a contactless conductivity detector (CE-C4D) and analyzed in less than one minute. A separation electrolyte consisted of 10 mmol/L l-histidine, 15 mmol/L dl-glutamic acid, and 30 µmol/L cetyltrimethylammonium bromide. The whole procedure starting from the finger-prick sampling until the CE-C4D analysis was finished, took less than 5 min and was suitable for monitoring lactate increase in blood plasma during incremental cycling exercise. The observed lactate increase during the experiments measured by the developed CE-C4D method correlated well with the results from a hand-held lactate analyzer (R = 0.9882). The advantage of the developed CE method is the speed, significant savings per analysis, and the possibility to analyze other compounds from blood plasma.

Estimation of anaerobic threshold by cardiac repolarization instability: a prospective validation study

BackgroundAssessing lactate (LT) or anaerobic thresholds (AT) in athletes is an important tool to control training intensities and to estimate individual performance levels. Previously we demonstrated that ECG-based assessment of cardiac repolarization instability during exercise testing allows non-invasive estimation of AT in recreational athletes. Here, we validate this method in professional and amateur team sports athletes.MethodsWe included 65 team sports athletes (32 professionals and 33 amateur athletes; 51 men, 14 women, mean age 22.3 ± 5.2 years) undergoing a standardized incremental cycle exercise test. During exercise testing a high-resolution ECG (1000 Hz) was recorded in Frank-leads configuration and beat-to-beat vector changes of cardiac repolarization (dT°) were assessed by previously established technologies. Repolarization-based AT (ATdT°) was estimated by its typical dT°-signal pattern. Additionally, LT was detected in accordance to methods established by Mader (LTMader) and Dickhuth (LTDickhuth).ResultsAll athletes performed exercise testing until exhaustion with a mean maximum workload of 262.3 ± 60.8 W (241.8 ± 64.4 W for amateur athletes and 283.4 ± 49.5 W for professional athletes). Athletes showed ATdT° at 187.6 ± 44.4 W, LTDickhuth at 181.1 ± 45.6 W and LTMader at 184.3 ± 52.4 W. ATdT° correlated highly significantly with LTDickhuth (r = 0.96, p < 0.001) and LTMader (r = 0.98, p < 0.001) in the entire cohort of athletes as well as in the subgroups of professional and amateur athletes (p < 0.001 for all).ConclusionsATdT°, defined by the maximal discordance between dT° and heart rate, can be assessed reliably and non-invasively via the use of a high-resolution ECG in professional and amateur athletes.

The Effects of Beverage Intake after Exhaustive Exercise on Organ Damage, Inflammation and Oxidative Stress in Healthy Males.

Strenuous exercise induces organ damage, inflammation and oxidative stress. To prevent exercise-induced organ damage, inflammation and oxidative stress, rehydrating may be an effective strategy. In the present study, we aimed to examine whether beverage intake after exhaustive exercise to recover from dehydration prevents such disorders. Thirteen male volunteers performed incremental cycling exercise until exhaustion. Immediately after exercise, the subjects drank an electrolyte containing water (rehydrate trial: REH) or did not drink any beverage (control trial: CON). Blood samples were collected before (Pre), immediately (Post), 1 h and 2 h after exercise. Urine samples were also collected before (Pre) and 2 h after exercise. We measured biomarkers of organ damage, inflammation and oxidative stress in blood and urine. Biomarkers of muscle, renal and intestinal damage and inflammation increased in the blood and urine after exercise. However, changes in biomarkers of organ damage and inflammation did not differ between trials (p > 0.05). The biomarker of oxidative stress, thiobarbituric acid reactive substances (TBARS), in plasma, showed different changes between trials (p = 0.027). One hour after exercise, plasma TBARS concentration in REH had a higher trend than that in CON (p = 0.052), but there were no significant differences between Pre and the other time points in each trial. These results suggest that beverage intake after exercise does not attenuate exercise-induced organ damage, inflammation or oxidative stress in healthy males. However, rehydration restores exercise-induced oxidative stress more quickly.

Mechanisms of Exertional Dyspnea in Patients with Mild COPD and a Low Resting DLCO

Patients with mild chronic obstructive pulmonary disease (COPD) and lower resting diffusing capacity for carbon monoxide (DLCO) often report troublesome dyspnea during exercise although the mechanisms are not clear. We postulated that in such individuals, exertional dyspnea is linked to relatively high inspiratory neural drive (IND) due, in part, to the effects of reduced ventilatory efficiency. This cross-sectional study included 28 patients with GOLD I COPD stratified into two groups with (n = 15) and without (n = 13) DLCO less than the lower limit of normal (<LLN; Global Lung Function Initiative criteria) and 16 healthy controls. We compared dyspnea (Borg scale), IND (by diaphragm electromyography), ventilatory equivalent for CO2 (V̇ E/V̇CO2), and respiratory mechanics during incremental cycle exercise in the three groups. Spirometry and resting lung volumes were similar between COPD groups. During exercise, dyspnea, IND and V̇ E/V̇CO2 were higher at equivalent work rates (WR) in the DLCO<LLN group compared with the other two groups (all p < 0.05). In patients with DLCO<LLN, severe respiratory mechanical constraints, indicated by end-inspiratory lung volume of approximately 90% of total lung capacity, occurred at a lower WR than the other two groups (p < 0.05). The dyspnea/IND relationship was similar across groups; therefore, the increased dyspnea at a standardized WR in the low DLCO<LLN group reflected the higher corresponding IND. Higher dyspnea ratings in patients with mild COPD and DLCO<LLN were associated with higher IND and V̇ E/V̇CO2 at a given work rate. Higher ventilatory requirements in the DLCO<LLN group accelerated dynamic mechanical abnormalities earlier in exercise, further increasing IND and dyspnea.

Respiratory Response to Underwater and Land‐based Cycling at the Matched Oxygen Uptake

Water immersion increases breathing effort against elevated hydrostatic pressure. Thus, aquatic exercise training may have a greater benefit for the respiratory function when compared to the same intensity of exercise performed on dryland. The purpose of this study was to investigate the effect of underwater cycling on the respiratory function and breathing pattern when compared to land-based cycling performed at the matched exercise intensity. Ten healthy men performed maximal graded exercise test and 15 minutes of incremental water-based cycling exercise (WE) and land-based cycling exercise (LE) on separate days. In WE, cycling began at 30 rpm, and the cadence was increased by 15 rpm every 5 minutes. 3 paddles were attached to the wheel of stationary bicycle to increase pedaling resistance. In LE, participants cycled continuously at 60 rpm for 15 minutes while wattage was adjusted to match oxygen uptake (VO2) to the WE condition. Using spirometry, respiratory function and respiratory muscle pressure were measured before and after cycling, and the magnitude of change between pre- and post- exercise was also measured. Breathing pattern was measured continuously during cycling. Water temperature and immersion level were kept at 31.5 ℃ and xiphoid appendix, respectively. VO2 duringcycling in water and on dryland was similar. Minute ventilation, inspiratory and expiratory volumes, and respiratory rate increased whereas, inspiratory and expiratory times decreased as the cycling intensity (VO2) increased (all P < 0.05). Respiratory rate was slightly higher at 60 rpm in WE than LE (27 ± 3 vs. 24 ± 3 bpm, P = 0.053). Inspiratory time was significantly higher at rest in WE than LE (1.4 ± 0.1 vs. 1.2 ± 0.0 sec, P < 0.05). After cycling exercise, change in the forced expiratory volume in one second and change in the peak expiratory flow were significantly lower in WE than LE (-0.04 ± 0.15 vs. 0.06 ± 0.10 L, P < 0.05. -0.37 ± 0.87 vs. 0.04 ± 0.63 L, P < 0.05, respectively). These data suggest that the respiratory and breathing responses were mostly similar during underwater and land-based cycling when VO2 is matched in both conditions. However, breathing may slightly be shallower during a higher-intensity aquatic cycling which may have chronic effects on respiratory function after multiple bouts of aquatic cycling for a longer term.

Thoracoabdominal asynchrony associates with exercise intolerance in fibrotic interstitial lung diseases.

The precise coordination of respiratory muscles during exercise minimizes work of breathing and avoids exercise intolerance. Fibrotic interstitial lung disease (f-ILD) patients are exercise-intolerant. We assessed whether respiratory muscle incoordination and thoracoabdominal asynchrony (TAA) occur in f-ILD during exercise, and their relationship with pulmonary function and exercise performance. We compared breathing pattern, respiratory mechanics, TAA and respiratory muscle recruitment in 31 f-ILD patients and 31 healthy subjects at rest and during incremental cycle exercise. TAA was defined as phase angle (PhAng) >20°. During exercise, when compared with controls, f-ILD patients presented increased and early recruitment of inspiratory rib cage muscle (p< 0.05), and an increase in PhAng, indicating TAA. TAA was more frequent in f-ILD patients than in controls, both at 50% of the maximum workload (42.3% vs. 10.7%, p= 0.01) and at the peak (53.8% vs. 23%, p= 0.02). Compared with f-ILD patients without TAA, f-ILD patients with TAA had lower lung volumes (forced vital capacity, p< 0.01), greater dyspnoea (Medical Research Council > 2 in 64.3%, p= 0.02), worse exercise performance (lower maximal work rate % predicted, p= 0.03; lower tidal volume, p= 0.03; greater desaturation and dyspnoea, p< 0.01) and presented higher oesophageal inspiratory pressures with lower gastric inspiratory pressures and higher recruitment of scalene (p< 0.05). Exercise induces TAA and higher recruitment of inspiratory accessory muscle in ILD patients. TAA during exercise occurred in more severely restricted ILD patients and was associated with exertional dyspnoea, desaturation and limited exercise performance.

Clinical evaluation of a novel subcutaneous lactate monitor

Lactate levels are commonly used as an indirect measure to assess metabolic stress in clinical conditions like sepsis. Dynamic lactate measurements are recommended to assess and guide treatment in patients with shock and other critical care conditions. A minimally invasive, continuous lactate monitor has potential to improve clinical decisions and patient care. The purpose of the study was to evaluate continuous lactate measurements of a novel enzymatic Continuous Lactate Monitor (CLM) developed in our laboratory. Lactate levels were monitored during incremental cycling exercise challenges as a tool for hyperlactatemia. Six healthy individuals 18–45 y/o (4 males, 2 females) participated in the study. CLM devices were inserted subcutaneously in the postero-lateral trunk below the renal angle, one hour before the exercise challenge. Each exercise challenge consisted of a 3 to 12-min warm up period, followed by up to 7, 4-min incremental workload bouts separated by rest intervals. Continuous lactate measurements obtained from CLM were compared with commercial lactate analyzer (Abbott iSTAT) measurements of venous blood (plasma) drawn from the antecubital vein. Blood was drawn at up to 25 time points spanning the duration of before exercise, during exercise, and up to 120 min post exercise. Area under the curve (AUC), and delay time were calculated to compare the CLM readings with plasma lactate concentration. Average plasma lactate concentration increased from 1.02 to 16.21 mM. Ratio of AUC derived from CLM to plasma lactate was 1.025 (0.990–1.058). Average dynamic delay time of CLM to venous plasma lactate was 5.22 min (2.87–10.35). Insertion sites examined 48 h after CLM removal did not show signs of side effects and none required medical attention upon examination. The newly developed CLM has shown to be a promising tool to continuously measure lactate concentration in a minimally invasive fashion. Results indicate the CLM can provide needed trends in lactate over time. Such a device may be used in the future to improve treatment in clinical conditions such as sepsis.

Effects of Post-Exertional Malaise on Markers of Arterial Stiffness in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Background: Evidence is emerging that individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) may suffer from chronic vascular dysfunction as a result of illness-related oxidative stress and vascular inflammation. The study aimed to examine the impact of maximal-intensity aerobic exercise on vascular function 48 and 72 h into recovery. Methods: ME/CFS (n = 11) with gender and age-matched controls (n = 11) were randomly assigned to either a 48 h or 72 h protocol. Each participant had measures of brachial blood pressure, augmentation index (AIx75, standardized to 75 bpm) and carotid-radial pulse wave velocity (crPWV) taken. This was followed by a maximal incremental cycle exercise test. Resting measures were repeated 48 or 72 h later (depending on group allocation). Results: No significant differences were found when ME/CFS were directly compared to controls at baseline. During recovery, the 48 h control group experienced a significant 7.2% reduction in AIx75 from baseline measures (p < 0.05), while the matched ME/CFS experienced no change in AIx75. The 72 h ME/CFS group experienced a non-significant increase of 1.4% from baseline measures. The 48 h and 72 h ME/CFS groups both experienced non-significant improvements in crPWV (0.56 ms−1 and 1.55 ms−1, respectively). Conclusions: The findings suggest that those with ME/CFS may not experience exercise-induced vasodilation due to chronic vascular damage, which may be a contributor to the onset of post-exertional malaise (PEM).

A pilot study investigating cortical haemodynamic and physiological correlates of exercise cognition in trained and untrained cyclists over an incremental self-paced performance test, while thinking aloud

ObjectivesFew studies have directly investigated changes in cortical haemodynamics during a self-paced interval endurance activity, while collecting conscious cognition and physiological performance data. This pilot study used functional Near Infrared Spectroscopy (fNIRS), while capturing conscious cognition using Think Aloud (TA) during an incremental paced cycling exercise. MethodsA mixed design was implemented with cycling expertise (untrained vs. trained) as the between groups variable and incremental self-paced stage (5 stages of increasing effort) and site (12 optodes across the PFC) as the within groups variables. Dependent measures were the changes in cortical O2Hb, and physiological indicators (% heart rate max (%HRmax), average power output (APO), peak power output (PPO), rate of perceived exertion (RPE) and blood lactate (Bla)) over time. Participants used TA throughout their second interval trial. ResultsTrained cyclists had higher APO and maximum power output (MPO) from stages 2–5, in addition to a greater increase in PPO over the whole trial. There were significant main effects of stage on %HRmax, Bla and RPE. Differences in cortical haemodynamics were found specifically in areas in the mid left and right PFC. TA data demonstrated that untrained participants verbalised more irrelevant information and feelings of pain and fatigue, in addition to both groups verbalising significantly more motivation-related thoughts during the final stage. ConclusionThis pilot is the first to capture changes in Cox, physiological measures and conscious cognition through the use of TA. We demonstrate the potential role of mid- PFC, and how conscious cognition may change over time. This study has implications for coaches and sport psychologists who may want to understand the cognitions of their athlete during an event and support low level athletes in developing a better understanding of the own cognitions.

Impact of supine versus upright exercise on muscle deoxygenation heterogeneity during ramp incremental cycling is site specific

PurposeWe tested the hypothesis that incremental ramp cycling exercise performed in the supine position (S) would be associated with an increased reliance on muscle deoxygenation (deoxy[heme]) in the deep and superficial vastus lateralis (VLd and VLs, respectively) and the superficial rectus femoris (RFs) when compared to the upright position (U).Methods11 healthy men completed ramp incremental exercise tests in S and U. Pulmonary dot{V}O2 was measured breath-by-breath; deoxy[heme] was determined via time-resolved near-infrared spectroscopy in the VLd, VLs and RFs.ResultsSupine exercise increased the overall change in deoxy[heme] from baseline to maximal exercise in the VLs (S: 38 ± 23 vs. U: 26 ± 15 μM, P < 0.001) and RFs (S: 36 ± 21 vs. U: 25 ± 15 μM, P < 0.001), but not in the VLd (S: 32 ± 23 vs. U: 29 ± 26 μM, P > 0.05).ConclusionsThe present study supports that the impaired balance between O2 delivery and O2 utilization observed during supine exercise is a regional phenomenon within superficial muscles. Thus, deep muscle defended its O2 delivery/utilization balance against the supine-induced reductions in perfusion pressure. The differential responses of these muscle regions may be explained by a regional heterogeneity of vascular and metabolic control properties, perhaps related to fiber type composition.

Multidimensional breathlessness response to exercise: Impact of COPD and healthy ageing

This study compared the multidimensional breathlessness response to incremental cardiopulmonary cycle exercise testing (CPET) in people with chronic obstructive pulmonary disease (COPD; n = 14, aged 69 ± 9 years, forced expiratory volume in 1-sec = 54 ± 16 % predicted) and healthy older (OA) (n = 35, aged 68 ± 5 years) and younger (YA) (n = 19, aged 28 ± 8 years) adults. Participants performed CPET and successively rated overall breathlessness intensity, unsatisfied inspiration, breathing too shallow, work/effort of breathing, and breathlessness-related unpleasantness, fear, and anxiety using the 0−10 Borg scale. At any given percent predicted peak minute ventilation, people with COPD rated all breathlessness sensations higher than OA and YAs, who were similar. Most between group differences disappeared when examined in relation to inspiratory reserve volume, except people with COPD reported higher levels of unsatisfied inspiration and breathing too shallow (vs YA), and breathlessness-related fear and anxiety (vs OA and YAs). Multidimensional ratings of breathlessness sensations during CPET provides further insight into differences in exertional symptom perceptions among people with COPD and without COPD.

Perceived Improvements of Quality of Life (QoL) among Patients with Idiopathic Pulmonary Fibrosis (IPF) in Response to a 6-Week Rehabilitation Program

Idiopathic pulmonary fibrosis (IPF) is a chronic, life-limiting with an average life expectancy of 05 years following the onset of the disease, with no curative treatments. These patients need palliative care and rehabilitation is one of the methods that can be used to improve quality of life (QoL) among these patients. Yet the research conducted to assess benefits of pulmonary rehabilitation (PR) in terms of improving physical activity and QoL in IPF patients remains limited. Hence this study aims to evaluate the effect of a bespoke pulmonary rehabilitation programme, on the physical, physiological and psychological parameters and improvements of QoL among IPF patients. Eleven (11) subjects with IPF received 6 weeks of pulmonary rehabilitation. An interviewer administered quality of life questionnaire, six-minute walking test (6MWT), Incremental bicycle exercise tests were performed, and cardiac and respiratory parameters were assessed pre- and post-rehabilitation. The 6MWT was significantly increased following training (Pre 312.55 ± 89.99; Post, 380.73 ± 59.60). A significant improvement was observed in overall QoL (2.226 ± 0.026), dyspnoea (-0.455 ± 0.004) anxiety (-2.070 ± 0.038), depression (-2.217 ± 0.027) scores. No significant changes were found in the VO2 max and other cardiopulmonary parameters, while non-significant improvement was seen in SpO2 at peak exercise from 85.8 - 86.5. Bespoke pulmonary rehabilitation program is beneficial in short term improvement of the functional exercise capacity, dyspnoea and QoL among IPF patients.

Plasma BCAA concentrations during exercise of varied intensities in young healthy men-the impact of endurance training.

BackgroundBranched-chain amino acids (BCAA) i.e., leucine (Leu), isoleucine (Ile) and valine (Val) are important amino acids, which metabolism play a role in maintaining system energy homeostasis at rest and during exercise. As recently shown lowering of circulating BCAA level improves insulin sensitivity and cardiac metabolic health. However, little is known concerning the impact of a single bout of incremental exercise and physical training on the changes in blood BCAA. The present study aimed to determine the impact of a gradually increasing exercise intensity—up to maximal oxygen uptake (VO2max) on the changes of the plasma BCAA [∑BCAA]pl, before and after 5-weeks of moderate-intensity endurance training (ET).MethodsTen healthy young, untrained men performed an incremental cycling exercise test up to exhaustion to reach VO2max, before and after ET.ResultsWe have found that exercise of low-to-moderate intensity (up to ∼50% of VO2max lasting about 12 min) had no significant effect on the [∑BCAA]pl, however the exercise of higher intensity (above 70% of VO2max lasting about 10 min) resulted in a pronounced decrease (p < 0.05) in [∑BCAA]pl. The lowering of plasma BCAA when performing exercise of higher intensity was preceded by a significant increase in plasma lactate concentration, showing that a significant attenuation of BCAA during incremental exercise coincides with exercise-induced acceleration of glycogen utilization. In addition, endurance training, which significantly increased power generating capabilities at VO2max (p = 0.004) had no significant impact on the changes of [∑BCAA]pl during this incremental exercise.ConclusionWe have concluded that an exercise of moderate intensity of relatively short duration generally has no effect on the [∑BCAA]pl in young, healthy men, whereas significant decrease in [∑BCAA]pl occurs when performing exercise in heavy-intensity domain. The impact of exercise intensity on the plasma BCAA concentration seems to be especially important for patients with cardiometabolic risk undertaken cardiac rehabilitation or recreational activity.

Transcutaneous PCO2 for Exercise Gas Exchange Efficiency in Chronic Obstructive Pulmonary Disease

Gas exchange inefficiency and dynamic hyperinflation contributes to exercise limitation in chronic obstructive pulmonary disease (COPD). It is also characterized by an elevated fraction of physiological dead space (VD/VT). Noninvasive methods for accurate VD/VT assessment during exercise in patients are lacking. The current study sought to compare transcutaneous PCO2 (TcPCO2) with the gold standard—arterial PCO2 (PaCO2)—and other available methods (end tidal CO2 and the Jones equation) for estimating VD/VT during incremental exercise in COPD. Ten COPD patients completed a symptom limited incremental cycle exercise. TcPCO2 was measured by a heated electrode on the ear-lobe. Radial artery blood was collected at rest, during unloaded cycling (UL) and every minute during exercise and recovery. Ventilation and gas exchange were measured breath-by-breath. Bland-Altman analysis examined agreement of PCO2 and VD/VT calculated using PaCO2, TcPCO2, end-tidal PCO2 (PETCO2) and estimated PaCO2 by the Jones equation (PaCO2-Jones). Lin’s Concordance Correlation Coefficient (CCC) was assessed. 114 measurements were obtained from the 10 COPD subjects. The bias between TcPCO2 and PaCO2 was 0.86 mmHg with upper and lower limit of agreement ranging −2.28 mmHg to 3.99 mmHg. Correlation between TcPCO2 and PaCO2 during rest and exercise was r2=0.907 (p < 0.001; CCC = 0.941) and VD/VT using TcPCO2 vs. PaCO2 was r2=0.958 (p < 0.0001; CCC = 0.967). Correlation between PaCO2-Jones and PETCO2 vs. PaCO2 were r2=0.755, 0.755, (p < 0.001; CCC = 0.832, 0.718) and for VD/VT calculation (r2=0.793, 0.610; p < 0.0001; CCC = 0.760, 0.448), respectively. The results support the accuracy of TcPCO2 to reflect PaCO2 and calculate VD/VT during rest and exercise, but not in recovery, in COPD patients, enabling improved accuracy of noninvasive assessment of gas exchange inefficiency during incremental exercise testing.

Multidimensional breathlessness assessment during cardiopulmonary exercise testing in healthy adults.

This study explored if healthy adults could discriminate between different breathlessness dimensions when rated immediately one after another (successively) during symptom-limited incremental cardiopulmonary cycle exercise testing (CPET) using multiple single-item rating scales. Fifteen apparently healthy adults (60% male) aged 22 ± 2years performed six incremental cycle CPETs separated by ≥ 48h. During each CPET (at rest, every 2-min and at end exercise), participants rated different breathlessness sensations using the 0-10 modified Borg scale using one of six assessment protocols, randomized for order: (1) 'BREATHLESSALL' = breathlessness sensory intensity (SI), breathlessness unpleasantness (UN), work/effort of breathing (SQW/E), and unsatisfied inspiration (SQUI) assessed; (2) SI and UN assessed; and (3-6) SI, UN, SQW/E, and SQUI each assessed alone. Physiological responses to CPET were also evaluated. Physiological and breathlessness responses to CPET were comparable across the six protocols, with the exception of SI rated lower at the highest submaximal power output (220 ± 56 watts) during the BREATHLESSALL protocol (0-10 Borg units 4.2 ± 1.7) compared to SI + UN (5.2 ± 2.1, p = 0.03) and SI alone (5.1 ± 1.9, p = 0.04) protocols. Ratings of SI and SQW/E were not significantly different when assessed in the same protocol, and were significantly higher than UN and SQUI, which were comparable. In healthy younger adults, use of two separate single-item rating scales to assess breathlessness during CPET is feasible and enables the distinct sensory intensity and affective dimensions of exertional breathlessness to be assessed.

Changes in Optical Path Length Reveal Significant Potential Errors of Muscle Oxygenation Evaluation during Exercise in Humans.

Near-infrared spectroscopy (NIRS), performed with a commonly available noninvasive tissue oxygenation monitoring device, is based on the modified Beer-Lambert law (MBLL). Although NIRS based on MBLL (NIRSMBLL) assumes that the optical path length (PL) is constant, the effects of changes in PL during exercise on muscle oxygenation calculated by MBLL are still incompletely understood. Thus, the purposes of this study were to examine the changes in optical properties during ramp incremental exercise and to compare muscle oxygen dynamics measured by time-resolved NIRS with those calculated based on MBLL. Twenty-two healthy young men performed ramp incremental cycling exercise until exhaustion. Optical properties (reduced scattering coefficient and PL) and absolute oxygenated, deoxygenated, and total hemoglobin and myoglobin concentrations (oxy[Hb + Mb], deoxy[Hb + Mb], and total[Hb + Mb], respectively) at the vastus lateralis were continuously monitored by a three-wavelength (763, 801, and 836) time-resolved NIRS device. The values of oxy-, deoxy-, and total[Hb + Mb] were then recalculated by assuming constant PL. PL at all wavelengths statistically significantly shortened during exercise. In particular, PL at 763 nm was greatly shortened, and the average changes during exercise were a 9.8% ± 3.1% reduction. In addition, significant differences in the kinetics of oxy-, deoxy-, and total[Hb + Mb] between directly measuring PL and assuming constant PL were found. The average changes in measured PL and assuming constant PL-deoxy[Hb + Mb] were increases of 28.8 ± 16.0 μM and increases of 16.4 ± 9.3 μM, respectively. Assuming constant PL in NIRSMBLL significantly underestimated actual muscle oxy/deoxygenation as compared with measurements obtained by real-time PL determination. The percent degree of the underestimated oxy/deoxygenation was greater than the percent degree of the changes in PL.

Variations in exercise ventilation in hypoxia will affect oxygen uptake.

Reports of VO2 response differences between normoxia and hypoxia during incremental exercise do not agree. In this study VO2 and VE were obtained from 15-s averages at identical work rates during continuous incremental cycle exercise in 8 subjects under ambient pressure (633 mmHg ≈1,600 m) and during duplicate tests in acute hypobaric hypoxia (455 mmHg ≈4,350 m), ranging from 49 to 100% of VO2 peak in hypoxia and 42-87% of VO2 peak in normoxia. The average VO2 was 96 mL/min (619 mL) lower at 455 mmHg (n.s. P = 0.15) during ramp exercises. Individual response points were better described by polynomial than linear equations (mL/min/W). The VE was greater in hypoxia, with marked individual variation in the differences which correlated significantly and directly with the VO2 difference between 455 mmHg and 633 mmHg (P = 0.002), likely related to work of breathing (Wb). The greater VE at 455 mmHg resulted from a greater breathing frequency. When a subject's hypoxic ventilatory response is high, the extra work of breathing reduces mechanical efficiency (E). Mean ∆E calculated from individual linear slopes was 27.7 and 30.3% at 633 and 455 mmHg, respectively (n.s.). Gross efficiency (GE) calculated from mean VO2 and work rate and correcting for Wb from a VE-VO2 relationship reported previously, gave corresponding values of 20.6 and 21.8 (P = 0.05). Individual variation in VE among individuals overshadows average trends, as also apparent from other reports comparing hypoxia and normoxia during progressive exercise and must be considered in such studies.

Effect of ambient temperature on fat oxidation during an incremental cycling exercise test

Aim: The objective of this current research was to compare fat oxidation rates during an incremental cycling exercise test in a temperate vs. hot environment. Methods: Twelve healthy young participants were recruited for a randomised crossover experimental design. Each participant performed a VO2max test in a thermoneutral environment followed by two cycling ramp test trials, one in a temperate environment (18.3°C) and another in a hot environment (36.3°C). The ramp test consisted of 3-min stages of increasing intensity (+10% of VO2max) while gas exchange, heart rate and perceived exertion were measured. Results: During exercise, there was a main effect of the environment temperature on fat oxidation rate (F = 9.35, P = 0.014). The rate of fat oxidation was lower in the heat at 30% VO2max (0.42 ± 0.15 vs.0.37 ± 0.13 g/min; P = 0.042), 60% VO2max (0.37 ± 0.27 vs.0.23 ± 0.23 g/min; P = 0.018) and 70% VO2max (0.22 ± 0.26 vs.0.12 ± 0.26 g/min; P = 0.007). In addition, there was a tendency for a lower maximal fat oxidation rate in the heat (0.55 ± 0.2 vs.0.48 ± 0.2 g/min; P = 0.052) and it occurred at a lower exercise intensity (44 ± 14 vs.38% ± 8% VO2max; P = 0.004). The total amount of fat oxidised was lower in the heat (5.8 ± 2.6 vs 4.6 ± 2.8 g; P = 0.002). The ambient temperature also produced main effects on heart rate (F = 15.18, P = 0.005) and tympanic temperature (F = 25.23, P = 0.001) with no effect on energy expenditure (F = 0.01, P = 0.945). Conclusion: A hot environment notably reduced fat oxidation rates during a ramp exercise test. Exercising in the heat should not be recommended for those individuals seeking to increase fat oxidation during exercise.

Relationship Between Lung Diffusion And Exercise Capacity In Heart Failure With Preserved Ejection Fraction

PURPOSE: Patients with heart failure with preserved ejection fraction (HFpEF) have impaired lung diffusion (DL) at rest and during exercise which may contribute to a reduced exercise capacity. However, it is unclear whether these impairments are solely due to alterations in pulmonary hemodynamics or related to other cardiopulmonary factors which may impair oxygen uptake such as the inability to recruit lung surface area. Therefore this study examined simultaneous measurements of DL for carbon monoxide (DLCO) and nitric oxide (DLNO), which allows for partitioning of DL into its alveolar-capillary membrane (Dm) and pulmonary capillary blood volume (Vc) components, to better understand the relationship between exertional changes in lung diffusion and exercise capacity. METHODS: HFpEF patients (N=17, age=62±9y, BMI=36±8kg/m2) undergoing exercise right heart catheterization performed simultaneous rebreathe DLCO/NO tests at rest and during each stage of incremental supine cycling exercise, and membrane conductance (Dm) and pulmonary capillary blood volume (Vc) were calculated. Breath-by-breath pulmonary gas exchange was recorded throughout rest and exercise. RESULTS: All patients were hemodynamically diagnosed with HFpEF (pulmonary capillary wedge pressure >15 at rest and/or >25 mmHg during exercise). Overall lung and alveolar-capillary membrane diffusion increased from rest to peak exercise (DLCO: 11.8±4.0 to 16.2±7.4 ml/min/mmHg, DLNO: 33.1±11.5 to 48.4±21.9 ml/min/mmHg, Dm: 18.9±7.2 to 28.3±13.1 ml/min/mmHg; p’s<0.01). The change in DL was related to exercise capacity (change in DLCO vs. peak VO2: R=0.69, p<0.01, change in DLNO vs. peak VO2: R=0.65, p<0.01) and this was primarily driven by changes in Dm (change in Dm vs. peak VO2: R=0.63, p<0.01) but not Vc (change in Vc vs. peak VO2: R=0.15, p=0.582). CONCLUSIONS: These data highlight that a limited increase in lung diffusion and alveolar-capillary membrane conductance during exercise are associated with a lower VO2 peak in HFpEF patients. In addition to hemodynamic constraints previously reported in HFpEF, an inability to recruit lung surface area during exercise may also contribute to the reduced exercise capacity in these patients.