Submaximal Bicycle Exercise Research Articles

Cardiorespiratory Responses to Exercise in Hypobaric versus Normobaric Hypoxia: A Randomized, Single-Blind, Crossover Study.

There is controversy whether there are meaningful physiological differences between hypobaric (HH) and normobaric hypoxia (NH). This study aimed to compare the cardiorespiratory responses to acute HH and NH under strictly controlled conditions. We hypothesized no differences at rest and during submaximal exercise, whereas during maximal exercise, a higher maximal ventilation (V̇Emax), peripheral oxygen saturation (SpO2) and maximal oxygen consumption (V̇O2max) in HH than in NH. In a randomized, single-blind, crossover design, eight young healthy subjects (three females) were studied in an environmental chamber in which either the barometric pressure (HH) or the inspired oxygen fraction (NH) was reduced to the equivalent of ~4000 m altitude. Measurements were taken at rest, during submaximal (moderate and high intensity) and maximal cycling exercise. All resting parameters were similar between HH and NH, except for a lower root mean square of the successive R-R interval differences in HH (p < 0.05). SpO2 was 2% higher in HH at all exercise intensities (p < 0.05). During submaximal exercise, minute ventilation was similar between HH and NH. However, HH yielded a 7% lower tidal volume during moderate-intensity exercise (p < 0.05) and a lower respiratory exchange ratio during high-intensity exercise (p < 0.01). V̇Emax and V̇O2max were 11% and 6% higher in HH, respectively (p < 0.01 for both). SpO2 at maximal exercise was positively correlated with V̇Emax, V̇Emax/V̇O2max and V̇O2max. The higher V̇O2max found in HH than in NH can be attributed to the higher V̇Emax counteracting desaturation at maximal exercise. Conversely, submaximal SpO2 improved in HH through mechanisms other than increased ventilation. These findings are likely due to respiratory muscle unloading in HH, which operated through different mechanisms depending on exercise intensity.

Cardiac autonomic regulation during submaximal exercise in women with fibromyalgia.

Fibromyalgia (FM) patients present impaired cardiac autonomic regulation during maximal exercise; however, it is unknown whether these alterations also manifest during submaximal exercise. The aim of this study was to compare the on-transient heart rate (HR) response and HR variability during a constant-load submaximal cycling exercise between FM and control (CON) women. Ten women with FM (age: 45.2±9.3 years) and 10 age-matched CON women (age: 48.4±6.1 years) performed a 15-min cycling exercise, with the work rate fixed at 50% of the individual peak power output attained in a maximal graded exercise test. The time intervals between consecutive heartbeats were recorded regularly during the exercise for subsequent analysis of on-transient HR response and HR variability indices. The on-transient HR time constant was similar (P=0.83) between the FM (41.0±14.1 sec) and CON (42.2±10.4 sec). During the 5-10 and 10-15 min of exercise, HR variability indices indicating sympathetic and parasympathetic activities were similar (P>0.05) between FM and CON groups. In conclusion, women with FM presented a normal cardiac autonomic response to submaximal cycling exercise. These findings have clinical relevance, as submaximal exercises are commonly prescribed for FM patients.

Prefrontal Cortex Oxygenation During Exercise in Older Adults with Motoric Cognitive Risk Syndrome.

Motoric cognitive risk syndrome (MCR) is a pre-dementia syndrome characterized by subjective memory complaints and gait impairments that may be related to lower prefrontal cortex (PFC) function. Acute bouts of aerobic exercise are shown to improve PFC function, however, the acute effects of exercise on PFC oxygenation have not yet been examined in MCR. This study aims to characterize the PFC oxygenation responses during acute exercise in older adults with MCR. Nineteen older adults with MCR performed a submaximal cycling exercise protocol. Functional near-infrared spectroscopy (fNIRS) is used to measure concentrations of oxygenated (OxyHb) and deoxygenated (DeoxyHb) hemoglobin from the PFC. There is a trend for increased OxyHb concentrations and decreased DeooxyHb concentrations during exercise. Exercise also induced significant increases in ratings of perceived exertion (RPEs) and heart rate. A significant, positive correlation between PFC OxyHb and RPEs during the cycling exercise are also observed. The findings reveal that PFC oxygenation increases during exercise in an intensity-dependent manner and the subjective perception of exertion is associated with the magnitude of PFC oxygenation. These results suggest that moderate-intensity cycling exercise may have beneficial effects on increasing cerebral blood flow in the PFC of older adults with MCR.

The Effects of Caffeine on Heart Rate and Heart Rate Variability at Rest and During Submaximal Cycling Exercise

ABSTRACT The aim of this study was to investigate the effects of caffeine on heart rate and heart rate variability (HRV) at rest and during submaximal exercise. Using a balanced, double-blind, randomized, crossover design, 16 male cyclists (age: 37 ± 9 years; V ˙ O2max: 4.44 ± 0.67 L·min−1) completed three trials in an air-conditioned laboratory. In Trial 1, cyclists completed two incremental cycling tests to establish the V ˙ O2-power output relationship and V ˙ O2max. In trials 2 and 3, cyclists were evaluated for heart rate and HRV at rest, after which they ingested a capsule containing 5 mg·kg−1 of caffeine or placebo. Thirty-five minutes post-supplementation, additional resting heart rate and HRV readings were taken after which cyclists completed a submaximal incremental cycling test (6 min stages) at 40–80% of V ˙ O2max; with HR and HRV measurements taken in the last 5 min of each increment. HRV was determined from the root mean square of successive differences between R–R intervals. There were significant supplement × exercise intensity interactions on heart rate (p = .019) and HRV (p = .023), with post hoc tests on the latter showing that caffeine increased HRV at 40%, 50%, and 60% of V ˙ O2max by 3.6 ± 4.9, 2.6 ± 2.8, and 0.6 ± 1.7 ms, respectively. There was a supplement × time interaction effect on resting HRV (p < .001), but not on heart rate (p = .351). The results of this study support the suggestion that caffeine increases the parasympathetic modulation of heart rate.Clinical trial registration number: NCT05521386.

Similar maximal aerobic capacity but lower energy efficiency during low-to-moderate exercise in women with constitutional thinness: new results from the NUTRILEAN study.

Individuals with constitutional thinness have been presented with a lower muscular energy metabolism at the cellular level but their effective aerobic capacities and exercise-related energy efficiency remains unexplored. The present study compares maximal and sub-maximal aerobic capacities between subjects with constitutional thinness and age-matched normal-weight ones. Anthropometric measures, body composition (Dual-X-ray absorptiometry), physical activity and sedentary time (GT3x actigraphs), and maximal aerobic capacities (cycling 2peak test) were assessed in 18 constitutionally thin (CT-body mass index < 17.5 kg m-2) and 17 normal-weight (NW-body mass index between 20 and 25 kg m-2) women. Energy efficiency was assessed during a submaximal cycling test and a walking exercise. CT had a lower body mass and body mass index compared to NW. Absolute peak oxygen uptake and maximal aerobic power were lower in CT subjects compared to NW (ES: -1.63 [-2.40; -0.86] and -1.32 [-2.05; -0.58], p < 0.001). 2peak related to body mass was not different between groups. Gross and net efficiency (ES: -0.78 [-1.48; -0.06], p = 0.03 and ES: -0.73 [-1.43; -0.01], p = 0.05) were lower in CT compared to NW during the submaximal cycling exercise. The gross energy cost of walking related to body mass was lower in subjects with CT (ES: -1.80 [-2.60; -0.97, p = 0.05), with no difference for the net one. Perceived exertion was similar between groups in responses to both submaximal exercises. Constitutionally thin women do not show impaired aerobic capacities at moderate to maximal intensities despite lower energy efficiency while cycling and walking at low-to-moderate intensities.

Impact of MCT Oil and Caffeine on Substrate Metabolism during Submaximal Exercise

Introduction: Recent research has suggested that medium-chain triglyceride (MCT) supplementation may increase fat oxidation (FatOx) during aerobic exercise, sparing muscle glycogen and, perhaps, enhancing performance. As both MCT and caffeine (CAF) are theorized to elicit these effects, this pilot study’s purpose was to compare the physiological responses of their combined supplementation during submaximal cycling exercise. Methods: Eight aerobically trained males (mean±SD; age 23.6±4.4 years; body mass 82.3±15.8 kg; height 180.9±8.7 cm) completed one aerobic capacity (VO2peak) test and three 45-min exercise trials at 60% VO2peak. Blinded and counterbalanced, one-hour prior to each trial, participants consumed: MCT+CAF (20 mL + 100 mg), long-chain triglycerides (LCT)+CAF (40 mL + 100 mg), or CAF (100 mg). Oxygen consumption (VO2), carbon dioxide output (VCO2), and minute ventilation (VE) were measured, subsequently calculating respiratory exchange ratio (RER), energy expenditure (EE), carbohydrate oxidation (CarbOx), and FatOx. Results: No significant differences between conditions were observed for average VO2 (p=0.474; η2=0.101), VE (p=0.323; η2=0.149), (RER (p=0.323; η2=0.149), EE (p=0.474; η2=0.101), CarbOx (p=0.274; η2=0.169), or FatOx (p=0.478; η2=0.100) or for total EE (p=0.474; η2=0.101), CarbOx (p=0.274; η2=0.169), or FatOx (p=0.478; η2=0.100). Conclusions: Co-ingestion of MCT+CAF didn’t produce any significantly different physiological responses compared to co-ingestion of LCT+CAF or the CAF control.

Submaximal, Low-Dose Eccentric vs Traditional Cycling Exercise: Reduced Oxygen Uptake and Pulmonary Artery Pressure Assessed by Echocardiography in Healthy Middle-aged Adults. A Randomized Controlled, Crossover Trial

ObjectiveTo investigate the ventilatory and circulatory differences between eccentric (ECC) and concentric (CON) cycling exercise at submaximal, low-dose intensity from onset to end-exercise in healthy middle-aged participants. DesignRandomized controlled crossover trial. SettingThe participants underwent 1 ECC and 1 CON test according to stepwise incremental exercise protocols at identical, submaximal intensities. Breath-by-breath analyses of ventilatory gas exchange and echocardiography were used to assess cardiopulmonary function during exercise. Participants24 healthy middle-aged, untrained participants (14 women, 10 men, 50±14 years) were included. Interventions1 ECC and 1 CON test at submaximal intensities. Main Outcome MeasureThe main outcome was oxygen uptake (V'O2). ResultsThe V'O2 increase was reduced by -422 mL/min (-52%, 95% confidence interval: -513 to -292, P<.001) during ECC, as well as the ventilatory drive. Echocardiographic parameters, heart rate (-14%), cardiac output (-21%), stroke volume (-15%), and pulmonary artery pressure by tricuspid regurgitation pressure gradient (TRPG) (-26%) were also significantly reduced during ECC compared with CON at identical intensities. Participants reported significantly less dyspnea and unchanged perceived leg fatigue in ECC. ConclusionECC was well tolerated, and significant reductions were observed in V'O2, ventilation, and right ventricular load compared with CON, even at low intensity levels. This study, conducted on healthy middle-aged participants, did not raise concerns that would hinder further investigation of the effects of ECC in patients with severely limited cardiopulmonary disease, and it calls for further research on this topic.

On the Relation Between Leg Motion Rate and Speech Tempo During Submaximal Cycling Exercise.

This study investigated whether temporal coupling was present between lower limb motion rate and different speech tempi during different exercise intensities. We hypothesized that increased physical workload would increase cycling rate and that this could account for previous findings of increased speech tempo during exercise. We also investigated whether the choice of speech task (read vs. spontaneous speech) affected results. Forty-eight women who were ages 18-35 years participated. A within-participant design was used with fixed-order physical workload and counterbalanced speech task conditions. Motion capture and acoustic data were collected during exercise and at rest. Speech tempo was assessed using the amplitude envelope and two derived intrinsic mode functions that approximated syllable-like and footlike oscillations in the speech signal. Analyses were conducted with linear mixed-effects models. No direct entrainment between leg cycling rate and speech rate was observed. Leg cycling rate significantly increased from low to moderate workload for both speech tasks. All measures of speech tempo decreased when participants changed from rest to either low or moderate workload. Speech tempo does not show temporal coupling with the rate of self-generated leg motion at group level, which highlights the need to investigate potential faster scale momentary coupling. The unexpected finding that speech tempo decreases with increased physical workload may be explained by multiple mental and physical factors that are more diverse and individual than anticipated. The implication for real-world contexts is that even light physical activity-functionally equivalent to walking-may impact speech tempo.

Exercise-Induced Hypoalgesia in Patients with Chronic Whiplash-Associated Disorders: Differences between Subgroups Based on the Central Sensitization Inventory.

Physical exercise is an important element in the rehabilitation of chronic whiplash-associated disorders, with the physiological process underlying pain reduction called exercise-induced hypoalgesia. In chronic whiplash-associated disorders, exercise-induced hypoalgesia appears impaired, and the research suggests a relationship with symptoms of dysfunctional nociceptive processing, such as central sensitization. This study improves our understanding of exercise-induced hypoalgesia in chronic whiplash-associated disorders by examining the differences between the extent of exercise-induced hypoalgesia in subgroups based on scores on the central sensitization inventory (CSI). Data were collected from 135 participants with chronic whiplash-associated disorders who completed a set of questionnaires. Pain pressure thresholds and temporal summations were assessed before and after a submaximal aerobic bicycle exercise test. We observed no interaction effect between exercise-induced hypoalgesia and the CSI scores for both pain pressure threshold and temporal summation. No overall statistical effect was measured in the analysis of the effect of time. The pain pressure threshold significantly related to the CSI. The temporal summation showed no correlation. During this study, we did not find evidence for a difference in the presence of exercise-induced hypoalgesia when the subgroups were created based on the central sensitization cluster calculator. Limited evidence was found for the influence of CSI scores on the delta pain pressure threshold.

Abstract 13886: Impaired Locomotor Muscle Blood Flow During Cycling Exercise in Heart Failure With Preserved Ejection Fraction

Introduction: Obesity and hypertension (HTN) are highly prevalent comorbid risk factors for heart failure with preserved ejection fraction (HFpEF). Obesity and HTN independently increase sympathetic nervous activity and impair muscle blood flow during exercise. Previous work has reported attenuated limb blood flow in patients with HFpEF; however, these findings were compared to controls with dissimilar comorbidities and during small muscle mass exercise. It is unclear if HFpEF alters muscle blood flow responses independent of the obesity- and HTN-mediated alterations. Hypothesis: We hypothesized the muscle blood flow response during cycling would be lower in HFpEF patients than age, sex, BMI, and HTN matched controls (CTL). Methods: HFpEF patients (n=14, 9M/5W, 71±7yrs, 32±4 kg/m 2 ) and CTL (n=12, 8M/4W, 69±7yrs, 31±4 kg/m 2 ) performed an incremental cycling test. Blood pressure was measured by manual sphygmomanometry, cardiac output (Q) by open-circuit acetylene wash-in technique, and systemic vascular resistance (SVR) was calculated. Vastus lateralis blood flow index (BFI) was measured by near-infrared spectroscopy and indocyanine green dye injections and venous norepinephrine concentration was measured. Changes from rest to 40 W of the incremental test are reported. Results: Resting Q, mean arterial pressure, SVR, and venous norepinephrine concentration were not statistically different between groups (p&gt;0.18). From rest to 40 W, the increases in Q (CTL: 3.9±0.8 vs. HFpEF: 3.6±0.7 L/min), mean arterial pressure (CTL: 5.7±2.7 vs. HFpEF: 6.6±6.1 mmHg), and SVR (CTL: -7.3±2.1 vs. HFpEF: -6.0±2.0 mmHg/L/min) were not statistically different between groups (all, p&gt;0.13). The HFpEF group had smaller increases in vastus lateralis BFI at 40 W compared to CTL (CTL: 7.2±3.6 vs. HFpEF: 4.2±2.6 fold-increase from rest) (p=0.02). The HFpEF group had greater increases in venous norepinephrine concentration from rest to 40 W than CTL (CTL: 164±216 vs. HFpEF: 377±247 pg/mL) (p=0.05). Conclusions: Our findings suggest that, compared to age, sex, BMI, and HTN matched controls, patients with HFpEF have an impaired locomotor muscle blood flow response during submaximal cycling exercise likely due to higher locomotor muscle vascular resistance.

Abstract 16270: Pulse Pressure Amplification Contributes to the Exaggerated Peripheral Blood Pressure Response to Exercise in Patients With HFpEF

Background: Patients with suspected heart failure and preserved ejection fraction (HFpEF) undergo invasive (right heart catheterization) cardiopulmonary exercise testing (iCPET) to confirm diagnosis. During iCPET peripheral arterial blood pressure (BP) is measured using a brachial cuff or radial arterial catheter. Notably, peripheral BP is typically higher than central BP and this difference is assessed by measuring pulse pressure amplification (PPA; peripheral - central PP; PP = systolic BP [SBP] - diastolic BP). The effect of PPA on the assessment of (exaggerated) exercise BP in HFpEF is unknown. Methods: 20 patients with HFpEF (75% Female; age: 69±7 years, BMI: 38±7 kg/m 2 ) were studied at rest and during submaximal and maximal cycling exercise. We measured radial BP (arterial catheterization) and derived ascending aortic BP using a transfer function applied to radial arterial waveforms (SphygmoCor). Pulse pressure amplification was assessed as radial-aortic pulse pressure. Data were compared with one-way and two-way (Site*Exercise Stage) ANOVA. Results: The increase in radial PP with exercise was greater than aortic PP (Site*Stage P&lt;0.001; Figure A); thus, PPA increased with exercise (ANOVA, P =0.001; Figure B). The increase in PPA was due to a greater increase in radial compared to aortic SBP (Site*Stage P=0.002; Figure C). The change in diastolic pressure was not different between sites (Figure D). Increases in PPA accounted for ~30% of the increase in radial SBP. The incidence of exaggerated exercise SBP (Male: &gt;210 mmHg; Female: &gt;190 mmHg) was higher in the radial artery compared to aorta (95 vs 40 %, χ2&lt;0.001). Conclusion: Peak exercise SBP was ~50 mmHg greater in the radial artery compared to aorta. The marked overestimation of central BP during exercise when measuring peripheral BP leads to misguided interpretation of BP responses to exercise, the magnitude of afterload and has implications for the assessment of ventricular-arterial coupling.

Effects of Sitting Recovery Protocols on Postexercise Heart Rate in Young Adults

Abstract Background We aimed to compare the effects of 3 different upright seated recovery protocols on heart rate recovery (HRR) after a submaximal ergometer exercise. Methods The study included 30 young adult volunteers (15 men and 15 women). Participants performed a submaximal cycle exercise test at a constant workload of 60 Watts until a steady HR was achieved. This was followed by 5 min of: (a) inactive, (b) active loadless, and (c) passive recovery protocols. The HRR was assessed as the difference between the peak exercise HR and the HR recorded following 1 min of recovery and as the percentage HR decline after 1 min postexercise. Abnormal HRR was defined as a reduction of 1-min HRR ≤12 b · min−1 or ≤15 b · min−1 or ≤18 b · min−1. Results In both sexes, HRR was faster during inactive recovery compared with active recovery. In males, HRR was faster during inactive recovery compared with passive recovery protocol. In females, HRR was faster during passive recovery compared with active recovery protocol. The prevalence of impaired HRR was greater in the active recovery compared with the passive and inactive recovery protocols in both sexes. Conclusion The present findings suggest that in both sexes, the postexercise HRR was mediated by a combined action of the central command and other inputs or stimuli arising from skeletal muscle activities. In addition, the active recovery protocol resulted to a slower HRR and elicited more abnormal postexercise HR responses compared with the other recovery protocols.

The impact of natural menstrual cycle and oral contraceptive pill phase on substrate oxidation during rest and acute submaximal aerobic exercise.

Previous research has identified sex differences in substrate oxidation during submaximal aerobic exercise including a lower respiratory exchange ratio (RER) in females compared with males. These differences may be related to differences in sex hormones. Our purpose was to examine the impact of the natural menstrual cycle (NAT) and second- and third-generation oral contraceptive pill (OCP2 and OCP3) cycle phases on substrate oxidation during rest and submaximal aerobic exercise. Fifty female participants (18 NAT, 17 OCP2, and 15 OCP3) performed two experimental trials that coincided with the low (i.e., nonactive pill/early follicular) and the high hormone (i.e., active pill/midluteal) phase of their cycle. RER and carbohydrate and lipid oxidation rates were determined from gas exchange measurements performed during 10 min of supine rest, 5 min of seated rest, and two 8-min bouts of submaximal cycling exercise at ∼40% and ∼65% of peak oxygen uptake (V̇o2peak). For all groups, there were no differences in RER between the low and high hormone phases during supine rest (0.73 ± 0.05 vs. 0.74 ± 0.05), seated rest (0.72 ± 0.04 vs. 0.72 ± 0.04), exercise at 40% (0.77 ± 0.04 vs. 0.78 ± 0.04), and 65% V̇o2peak (0.85 ± 0.04 vs. 0.86 ± 0.03; P > 0.19 for all). Similarly, carbohydrate and lipid oxidation rates remained largely unchanged across phases during both rest and exercise, apart from higher carbohydrate oxidation in NAT vs. OCP2 at 40% V̇o2peak (P = 0.019) and 65% V̇o2peak (P = 0.001). NAT and OCPs do not appear to largely influence substrate oxidation at rest and during acute submaximal aerobic exercise.NEW & NOTEWORTHY This study was the first to examine the influence of NAT and two generations of OCPs on substrate oxidation during rest and acute submaximal aerobic exercise. We reported no differences across cycle phases or groups on RER, and minimal impact on carbohydrate or lipid oxidation apart from an increase in carbohydrate oxidation in NAT compared with OCP2 during exercise. Based on these findings, NAT/OCP phase controls may not be necessary in studies investigating substrate oxidation.

Pulmonary ventilation and gas exchange during prolonged exercise in humans: Influence of dehydration, hyperthermia and sympathoadrenal activity.

What is the central question of the study? Ventilation increases during prolonged intense exercise, but the impact of dehydration and hyperthermia, with associated blunting of pulmonary circulation, and independent influences of dehydration, hyperthermia and sympathoadrenal discharge on ventilatory and pulmonary gas exchange responses remain unclear. What is the main finding and its importance? Dehydration and hyperthermia led to hyperventilation and compensatory adjustments in pulmonary CO2 and O2 exchange, such that CO2 output increased and O2 uptake remained unchanged despite the blunted circulation. Isolated hyperthermia and adrenaline infusion, but not isolated dehydration, increased ventilation to levels similar to combined dehydration and hyperthermia. Hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise, partly via sympathoadrenal activation. The mechanisms driving hyperthermic hyperventilation during exercise are unclear. In a series of retrospective analyses, we evaluated the impact of combined versus isolated dehydration and hyperthermia and the effects of sympathoadrenal discharge on ventilation and pulmonary gas exchange during prolonged intense exercise. In the first study, endurance-trained males performed two submaximal cycling exercise trials in the heat. On day 1, participants cycled until volitional exhaustion (135± 11min) while experiencing progressive dehydration and hyperthermia. On day 2, participants maintained euhydration andcore temperature (Tc ) during a time-matched exercise (control). At rest and during the first 20min of exercise, pulmonary ventilation ( ), arterial blood gases, CO2 output and O2 uptake were similar in both trials. At 135±11min, however, was elevated with dehydration and hyperthermia, and this was accompanied by lower arterial partial pressure of CO2 , higher breathing frequency, arterial partial pressure of O2 , arteriovenous CO2 and O2 differences, and elevated CO2 output and unchanged O2 uptake despite a reduced pulmonary circulation. The increased was closely related to the rise in Tc and circulating catecholamines (R2 ≥0.818, P≤0.034). In three additional studies in different participants, hyperthermia independently increased to an extent similar to combined dehydration and hyperthermia, whereas prevention of hyperthermia in dehydrated individuals restored to control levels. Furthermore, adrenaline infusion during exercise elevated both Tc and . These findings indicate that: (1) adjustments in pulmonary gas exchange limit homeostatic disturbances in the face of a blunted pulmonary circulation; (2) hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise; and (3) sympathoadrenal activation might partly mediate the hyperthermic hyperventilation.

Response of the carotid artery longitudinal motion to submaximal physical activity in healthy humans-Marked changes already at low workload.

The longitudinal motion of the arterial wall, that is, the displacement of the arterial wall along the artery, parallel to blood flow, is still largely unexplored. The magnitude and nature of putative changes in longitudinal motion of the arterial wall in response to physical activity in humans remain unknown. The aim of this study was therefore to study the longitudinal motion of the carotid artery wall during physical activity in healthy humans. Using in-house developed non-invasive ultrasonic methods, the longitudinal motion of the intima-media complex and the diameter changes of the right common carotid artery (CCA) in 40 healthy volunteers (20 volunteers aged 22-35 years; 20 volunteers aged 55-68 years) were assessed at rest and during submaximal supine bicycle exercise. In a subset of the subjects (n=18) also intramural shear strain were analyzed. The longitudinal motion of the intima-media complex underwent marked changes in response to physical activity, already at low workload; with most evident a marked increase of the first antegrade displacement (p < 0.001) in early systole. Likewise, the corresponding shear strain also increased significantly (p=0.004). The increase in longitudinal motion showed significant correlation to increase in blood pressure, but not to blood flow velocity or wall shear stress. In conclusion, physical activity markedly influences the longitudinal motion of the carotid artery wall in healthy humans already at low load. A possible "cushioning" function as well as possible implications for the function of the vasa vasorum, endothelium, and smooth muscle cells and extracellular matrix of the media, are discussed.

Standardizing submaximal exercise intensities for use of supine push-pull exercise during cardiovascular magnetic resonance.

Cardiovascular magnetic resonance (CMR) imaging during supine exercise at (sub)maximal oxygen consumption (VO2 ) offers unique diagnostic insights. However, maximal VO2 is not achievable in the supine position and standardizing submaximal exercise intensities remains challenging. Using heart rate or workload could be a viable option to translate VO2 -based submaximal exercise intensities. To translate submaximal exercise intensities upright cycling exercise (UCE) to supine push-pull exercise (SPPE), by comparing heart rate or workload determined during UCE, with heart rate and workload during SPPE at similar exercise intensities. Sixteen healthy young adults (20.4 ± 2.2 years; 8 female) underwent cardiopulmonary UCE and SPPE testing [mean ± standard deviation maximal VO2 : 3.2 ± 0.6 vs. 5 ± 0.3 L min-1 , p < 0.001 and median (interquartile range) of the maximum workload: 310 (244, 361) vs. 98 (98,100), p < 0.001, respectively]. Heart rate at 40% and 60% of maximal VO2 , as determined by UCE, showed low bias (-3 and 0 bpm, respectively) and wide limits of agreement (±26 and ±28 bpm, respectively), in Bland-Altman analysis. VO2 /Workload relation was exponential and less efficient during SPPE compared to UCE. Generalized estimated equation analysis predicted model-based mean workload during SPPE, with acceptable 95% confidence interval. Heart rate during UCE at submaximal exercise intensities can reasonably well be used to for SPPE in healthy subjects. Using workload, an ergometer specific, model-based mean can be used to determine exercise intensities during SPPE. Individual variations in response to posture and movement change are high. During clinical interpretation of exercise CMR, individual exercise intensity has to be considered.

Acute Cold Exposure Does Not Affect Gross Efficiency During Cycling

PURPOSE: Gross efficiency (GE) is known to decrease during exercise in the heat, but the effect of low ambient temperatures on GE is poorly understood. This study aims to investigate the effect of acute cold exposure on GE during steady state cycling before and after a time-trial. METHODS: Twenty-one, task habituated, male cyclists (age 26 ± 4 year, VO2max 60.1 ± 6.7 mL/kg/min) completed three cycling tests in temperatures of -15 °C, 0 °C and 20 °C. The exercise test consisted of a submaximal exercise bout between 55 and 65% VO2max before and after a 2500-m self-paced time trial. GE was calculated over a 3-min interval at the end of each submaximal block. The effect of acute cold exposure on body temperature was evaluated by measuring core body temperature and skin temperature on different locations. RESULTS: A multilevel linear model revealed that ambient temperature did not affect GE (&#935;2 (7) = 2.531, p = 0.282). Performing a time-trial had a significant effect on GE (&#935;2 (8) = 13.3967, p < 0.001), resulting in a lower GE after the time trial compared to before (pre: 20.6 ± 1.1%, post: 19.9 ± 1.1%, t = -5.542, p < 0.001). The decline in GE after performing a time-trial was not altered by ambient temperature (&#935;2 (7) = 3.57, p = 0.168). Acute cold exposure did not affect core body temperature (&#935;2 (7) = 0.470, p = 0.791), but mean skin temperature was significantly lower in -15 °C and 0 °C compared to 20 °C (-15 °C: 25.88 ± 1.06 °C, 0 °C: 27.32 ± 1.16 °C, 20 °C: 31.18 ± 0.78 °C, p < 0.003). CONCLUSION: Acute cold exposure did not affect GE during submaximal steady state cycling exercise performed before and after a time-trail. Low ambient temperatures resulted in lower skin temperatures, but core body temperature remained unaffected.

Longitudinal assessment of cardiorespiratory fitness and body mass of young healthy adults during COVID-19 pandemic.

Physical activity was reduced during the COVID-19 pandemic, especially when lockdowns were mandated; however, little is known about the impact of these lifestyle changes on objective measures of cardiorespiratory fitness. To address this knowledge gap, we evaluated the cardiorespiratory fitness of 14 young healthy adults (4 women, age: 27 ± 6 yr) just before the pandemic and after ∼1 yr of public health measures being in place. During fitness assessments, participants performed submaximal pseudorandom cycling exercise to assess cardiorespiratory kinetics, and a 25 W·min-1 ramp-incremental cycling test to determine peak oxygen uptake (V̇o2). Cluster analysis identified two subgroups of participants: those who had reduced peak V̇o2 at the 1-yr follow-up (-0.50 ± 0.17 L·min-1) and those whose peak V̇o2 was maintained (0.00 ± 0.10 L·min-1). Participants with reduced peak V̇o2 also exhibited slower heart rate kinetics (interaction: P = 0.01), reduced peak O2 pulse (interaction: P < 0.001), and lower peak work rate (interaction: P < 0.001) after 1 yr of the pandemic, whereas these variables were unchanged in the group of participants who maintained peak V̇o2. Regardless of changes in peak V̇o2, both subgroups of participants gained body mass (main effect: P = 0.002), which was negatively correlated with participants' level of self-reported physical activity level at the follow-up assessment (mass: ρ = -0.59, P = 0.03) These findings suggest that some young healthy individuals lost cardiorespiratory fitness during the pandemic, whereas others gained weight, but both changes could potentially increase the risk of adverse health outcomes and disease later in life if left unaddressed.NEW & NOTEWORTHY Some young healthy adults experienced cardiovascular deconditioning during the COVID-19 pandemic, with measurable reductions in cardiorespiratory fitness, whereas others experienced no change in fitness but gained body mass, which was related to self-reported physical activity during the pandemic.

Left Ventricular Strain Analysis During Submaximal Semisupine Bicycle Exercise Stress Echocardiography in Childhood Cancer Survivors

Background Childhood cancer survivors (CCSs) show relevant cardiac morbidity and mortality throughout life. Early detection is key for optimal support of patients at risk. The aim of this study was to evaluate 2-dimensional speckle-tracking echocardiography strain analysis during semisupine exercise stress in CCSs for detection of subclinical left ventricular dysfunction after cancer treatment. Methods and Results Seventy-seven CCSs ≥1-year postchemotherapy were prospectively examined at rest, low, and submaximal stress level and compared with a cohort of healthy adolescents and young adults (n=50). Global longitudinal strain (GLS), short axis circumferential strain, and corresponding strain rates were analyzed using vendor-independent software. CCSs at median 7.8 years postchemotherapy showed comparable left ventricular GLS, circumferential strain, and strain rate values at all stress stages to healthy controls. Yet, prevalence of abnormal GLS (defined as <2 SD of controls reference) in CCSs was 1.3% at rest, 2.7% at low, and 8.6% at submaximal stress. In CCSs, relative change of circumferential strain from rest to submaximal stress was lower than in healthy controls, median 16.9 (interquartile range [IQR], 3.4; 28.8) % versus 23.3 (IQR, 11.3; 33.3) %, P=0.03, most apparent in the subgroups of CCSs after high-dose anthracycline treatment and cancer diagnosis before the age of 5 years. Conclusions In this prospective 2-dimensional speckle tracking echocardiography strain study, prevalence of abnormal left ventricular GLS increased with stress level reflecting impaired cardiac adaptation to exercise stress in some CCSs. However, relatively early after last chemotherapy, this did not result in significant differences of mean GLS-, circumferential strain-, and strain rate values between CCSs and controls at any stress level.

Acute Cardiorespiratory and Metabolic Responses to Incremental Cycling Exercise in Endurance- and Strength-Trained Athletes.

Simple SummaryThe multiple structural and functional adaptive changes vary depending on the mode of training. The purpose of this study was to examine the acute effects of progressive submaximal cycling on selected cardiorespiratory and metabolic variables in endurance- and strength-trained athletes. The sample comprised participants with different training background: endurance trained group (triathletes), strength trained group (bodybuilders), and a control group (recreationally active students). The research problem was based on the verification of the minor non-specific cardiometabolic responses in strength and endurance trained athletes during a progressive submaximal cycling exercise test. The substantive finding of this study was that endurance- and strengthtrained athletes differed only in the metabolic responses of respiratory exchange ratio and blood lactate concentration, whereas the acute cardiorespiratory variables did not demonstrate any statistically relevant differences. Based on our findings we recommend that endurance-trained athletes follow a concurrent training program, combined strength and endurance training, to improve neuromuscular parameters and thus optimize their economy of movement and endurance-specific muscle power capacity.The purpose of this study was to examine the acute effects of a progressive submaximal cycling exercise on selected cardiorespiratory and metabolic variables in endurance and strength trained athletes. The sample comprised 32 participants aged 22.0 ± 0.54 years who were assigned into three groups: an endurance trained group (END, triathletes, n = 10), a strength trained group (STR, bodybuilders, n = 10), and a control group (CON, recreationally active students, n = 12). The incremental cycling exercise was performed using a progressive protocol starting with a 3 min resting measurement and then a 50 W workload with subsequent constant increments of 50 W every 3 min until 200 W. The following cardiometabolic variables were evaluated: heart rate (HR), oxygen uptake (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RER), systolic and diastolic blood pressure (SBP and DBP), and blood lactate (BLa−). We found the between-group differences in metabolic variables (the average RER and BLa−) were statistically significant (Tukey’s HSD test: CON vs. STR, p < 0.01 and p < 0.05, respectively; CON vs. END, p < 0.001; END vs. STR, p < 0.001). RER and BLa– differences in all groups depended on the workload level (G-G-epsilon = 0.438; p < 0.004 and G-G-epsilon = 0.400; p < 0.001, respectively). There were no significant differences in cardiorespiratory variables between endurance- and strength-trained groups. In conclusion, this study demonstrated that acute cardiorespiratory responses at each of the four submaximal workloads were comparable in endurance- compared to strength-trained athletes, but significantly different compared to recreationally active men. However, there were significant differences in the metabolic responses of RER and BLa−. Based on our findings we recommend that endurance-trained athletes follow a concurrent training program, combined strength and endurance training, to improve neuromuscular parameters and thus optimize their economy of movement and endurance-specific muscle power capacity.