Does limb partitioning and positioning affect acute cardiorespiratory responses during strength exercises in patients with COPD?

BACKGROUND AND OBJECTIVE: Cardiorespiratory responses and symptoms in response to endurance exercise in patients with COPD vary with the number and position of involved limbs. Responses to such variations have never been quantified for strength exercises. We therefore assessed acute cardiorespiratory responses during brief bouts of weight lifting exercises. METHODS: We compared double- versus single-limb leg extensions and arm elevations, as well as arm elevation done above or below shoulder level in patients with moderate to severe COPD (n = 10, 6 males, 66 (8.1 years), forced expiratory volume on 1 s (FEV1 ) % predicted = 34% (14%)). Minute ventilation, oxygen uptake, oxygen saturation, heart rate (HR), blood pressure (BP), rate of perceived exertion (RPE) and recovery time were collected during single sets of each exercise (10 repetitions at 80% of one repetition maximum). RESULTS: Ventilatory and gas exchange responses were not affected by the number of exercising limbs. Changes in HR, BP and RPE scores during arm elevation above shoulder level were greater after double- compared with single-arm elevation (P ≤ 0.001) and greater when exercising above compared with below shoulder level (P ≤ 0.01). Double-arm elevation above shoulder level required 1.5 min longer HR recovery time (P ≤ 0.041) compared with other exercises. CONCLUSION: Double-arm elevation above shoulder level appears to be more challenging than other strength exercise variations. Partitioning exercises and limb position may reduce perceived exertion during training.

Regulation of the chemosensory control of breathing by Kölliker-Fuse neurons.

The Kölliker-Fuse region (KF) and the lateral parabrachial nucleus (LPBN) have been implicated in the maintenance of cardiorespiratory control. Here, we evaluated the involvement of the KF region and the LPBN in cardiorespiratory responses elicited by chemoreceptor activation in unanesthetized rats. Male Wistar rats (280-330 g; n = 5-9/group) with bilateral stainless-steel guide cannulas implanted in the KF region or the LPBN were used. Injection of muscimol (100 and 200 pmol/100 nl) in the KF region decreased resting ventilation (1,140 ± 68 and 978 ± 100 vs. saline: 1,436 ± 155 ml·kg(-1)·min(-1)), without changing mean arterial pressure (MAP) and heart rate (HR). Bilateral injection of the GABA-A antagonist bicuculline (1 nmol/100 nl) in the KF blocked the inhibitory effect on ventilation (1,418 ± 138 vs. muscimol: 978 ± 100 ml·kg(-1)·min(-1)) elicited by muscimol. Muscimol injection in the KF reduced the increase in ventilation produced by hypoxia (8% O2) (1,827 ± 61 vs. saline: 3,179 ± 325 ml·kg(-1)·min(-1)) or hypercapnia (7% CO2) (1,488 ± 277 vs. saline: 3,539 ± 374 ml·kg(-1)·min(-1)) in unanesthetized rats. Bilateral injection of bicuculline in the KF blocked the decrease in ventilation produced by muscimol in the KF during peripheral or central chemoreflex activation. Bilateral injection of muscimol in the LPBN did not change resting ventilation or the increase in ventilation elicited by hypoxia or hypercapnia. The results of the present study suggest that the KF region, but not the LPBN, has mechanisms to control ventilation in resting, hypoxic, or hypercapnic conditions in unanesthetized rats.

Peak Oxygen Uptake is Slope Dependent: Insights from Ground Reaction Forces and Muscle Oxygenation in Trained Male Runners.

BACKGROUND: The aim of this study is to explore the effect of treadmill slope on ground reaction forces and local muscle oxygenation as putative limiting factors of peak oxygen uptake in graded maximal incremental running tests. Thirteen trained male runners completed five maximal incremental running tests on treadmill at - 15%, - 7.5%, 0%, 7.5% and 15% slopes while cardiorespiratory and local muscle oxygenation responses as well as ground reaction forces were continuously recorded. Blood lactate concentration and isometric knee extensor torque were measured before and after each test. RESULTS: Peak oxygen uptake was lower at - 15% slope compared to all other conditions (from - 10 to - 17% lower, p < 0.001), with no difference between - 7.5 and + 15% slope. Maximal heart rate and ventilation values were reached in all conditions. The negative external mechanical work increased from steep uphill to steep downhill slopes (from 6 to 92% of total external work) but was not correlated with the peak oxygen uptake reduction. Local muscle oxygenation remained higher in - 15% slope compared to level running (p = 0.003). CONCLUSIONS: Similar peak oxygen uptake can be reached in downhill running up to - 7.5% slope. At more severe downhill slopes (i.e., - 15%), greater negative muscle work and limited local muscle deoxygenation occurred, even in subjects familiarized to downhill running, presumably preventing the achievement of similar to other condition's peak oxygen uptake. KEY POINTS: Trained male runners can reach like level running V̇O2peak at moderate but not at severe negative slope. Negative external mechanical work increases with increasing negative slope. At maximal intensity Vastus Lateralis muscle oxygenation is higher in steep negative slope. Knee extensor isometric muscle torque is preserved after maximal level and uphill running, but reduced after downhill running, despite lower blood lactate. Progressive reduction of V̇O2 at maximal effort with increasing negative slope might be related to the metabolic consequences of increased lower limb negative external work (i.e., eccentric muscle actions).

Cardiorespiratory Response to Six-Minute Step Test in Post COVID-19 Patients-A Cross Sectional Study.

BACKGROUND AND PURPOSE: New coronavirus disease 2019 (COVID-19) can cause persistent symptoms and physical weakness that can lead to a limitation in activities of daily living (ADL). There is a lack of evidence about the performance in the six-minute step test (6MST) of post-COVID-19 patients and healthy subjects. The aim of this study is to investigate the cardiorespiratory response induced by the 6MST in post-COVID-19 patients and compare it with the response of the six-minute walk test (6MWT). METHODS: This cross-sectional study was conducted on 34 post-COVID-19 patients and 33 healthy subjects. The assessment was performed at one month from a non-severe SARS-CoV-2 infection. Both groups were assessed by using the 6MST, 6MWT, and the pulmonary function test (PFT). Post COVID functional status (PCFS) scale was used for the post-COVID-19 group to assess functional status. Physiological responses; heart rate (HR), respiratory rate (RR), oxygen saturation (SpO2), blood pressure (BP), and Borg scale for fatigue and dyspnea were recorded before and after the 6MST and 6MWT. RESULTS: the performance of the post-COVID-19 group was worse than the healthy group in both tests. In 6MWT, the distance walked by the post-COVID-19 group (423 ± 7) was 94 m less than the healthy group, and the number of climbed steps in the 6MST (121 ± 4) was 34 steps less than the healthy group. Both results were statistically significant (p < 0.001). There was a moderate positive correlation between the 6MST and 6MWT in walked distance versus steps number (r = 0.5, p < 0.001). In addition, there was a moderate correlation between the two tests in the post (HR, RR, SpO2, systolic blood pressure SBP, diastolic blood pressure DBP, dyspnea, and fatigue) with p < 0.001. CONCLUSIONS: Six-minute step tests produced similar cardiorespiratory responses when compared to a 6MWT. The 6MST can be used as an assessment tool for COVID-19 patients to evaluate their functional capacity and ADL.

Similar Slow Component of Oxygen Uptake and Ventilatory Efficiency between an Aerobic Dance Session on an Air Dissipation Platform and a Constant-Load Treadmill Test in Healthy Women.

There is a lack of evidence about the slow component of oxygen consumption (V.O2sc) and ventilatory efficiency (slope VE·VCO2−1) during an aerobic dance (AD) session on an air dissipation platform (ADP) despite the key role played in endurance exercises. This research was designed to assess V.O2sc, ventilatory efficiency, and blood lactate concentration by comparing two exercise modes: AD session on an ADP versus treadmill test at a constant-load intensity of the first ventilatory threshold (VT1). In the first session, an incremental treadmill test was completed. In sessions 2 and 3, the participants were randomly assigned to the AD session on an ADP or to a treadmill constant-load test at VT1 intensity to determine their cardioventilatory responses. In addition, their blood lactate levels and ratings of perceived exertion (RPE, CR-10) were evaluated. No significant differences were found between the constant-load treadmill test and AD session on an ADP with respect to V.O2sc, VE VCO2−1 slope, and RPE (p > 0.05). Higher blood lactate concentrations were observed in an AD session on an ADP than in a constant-load treadmill test at 10 min (p = 0.003) and 20 min (p < 0.001). The two different exercise modalities showed similar V.O2sc and VE·VCO2−1 slope, even though the blood lactate concentrations were different.

Sarcopenia as a Mediator of the Effect of a Gerontogymnastics Program on Cardiorespiratory Fitness of Overweight and Obese Older Women: A Randomized Controlled Trial.

The objectives were to analyze the effect of a gerontogymnastics program on functional ability and fitness on overweight and obese older woman and to understand if sarcopenia mediates its effect. This randomized controlled trial involved 216 overweight and obese women. The experimental group (EG) carried out 12 weeks of a gerontogymnastics program. The assessment was of gait speed, cardiorespiratory fitness, functional capacity, and muscle strength. EG showed significant improvements in almost every test. When the effect of training was adjusted by gait speed, the improvement of the 6 min walk test (MWT) for the trained group was no longer significant (p = 0.127). The improvement of the 6 MWT was significantly and positively associated with the 10 m test (ß = -10.087). After including the 10-m test in the equations, the association between the 6MWT and carrying out the training program decreased but remained significant (ß = -19.904). The mediation analysis showed a significant, direct and indirect effect with a significant Sobel test value (z = 6.606 ± 7.733; p = 0.000). These results indicate that a gerontogymnastics program improves functional capacity and fitness; and the effect of a gerontogymnastics program on CRF is mediated by sarcopenia in older women who are overweight and obese.

Comparison of Acute Responses to Two Different Cycling Sprint Interval Exercise Protocols with Different Recovery Durations.

Background: Knowledge of acute responses to different sprint interval exercise (SIE) helps to implement new training programs. The aim of this study was to compare the acute physiological, metabolic and perceptual responses to two different SIE cycling protocols with different recovery durations. Methods: Twelve healthy, active male participants took part in this study and completed four testing sessions in the laboratory separated by a minimum of 72h. Two SIE protocols were applied in randomized order: SIE6×10"/4'-six "all-out" repeated 10-s bouts, interspersed with 4-min recovery; and SIESERIES-two series of three "all-out" repeated 10-s bouts, separated by 30-s recovery and 18-min recovery between series. Protocols were matched for the total work time (1 min) and recovery (20 min). Results: In SIESERIES, peak oxygen uptake and peak heart rate were significantly higher (p < 0.05), without differences in peak blood lactate concentration and mean rating of perceived exertion compared to SIE6×10"/4'. There were no differences in peak power output, peak oxygen uptake and peak heart rate between both series in SIESERIES. Conclusions: Two series composed of three 10-s "all-out" bouts in SIESERIES protocol evoked higher cardiorespiratory responses, which can provide higher stimulus to improve aerobic fitness in regular training.

Acute Effects of Using Added Respiratory Dead Space Volume in a Cycling Sprint Interval Exercise Protocol: A Cross-Over Study.

Background: The aim of the study was to compare acute physiological, biochemical, and perceptual responses during sprint interval exercise (SIE) with breathing through a device increasing added respiratory dead space volume (ARDSV) and without the device. Methods: The study involved 11 healthy, physically active men (mean maximal oxygen uptake: 52.6 ± 8.2 mL∙kg1∙min-1). During four visits to a laboratory with a minimum interval of 72 h, they participated in (1) an incremental test on a cycle ergometer; (2) a familiarization session; (3) and (4) cross-over SIE sessions. SIE consisted of 6 × 10-s all-out bouts with 4-min active recovery. During one of the sessions the participants breathed through a 1200-mL ARDSv (SIEARDS). Results: The work performed was significantly higher by 4.4% during SIEARDS, with no differences in the fatigue index. The mean respiratory ventilation was significantly higher by 13.2%, and the mean oxygen uptake was higher by 31.3% during SIEARDS. Respiratory muscle strength did not change after the two SIE sessions. In SIEARDS, the mean pH turned out significantly lower (7.26 vs. 7.29), and the mean HCO3- concentration was higher by 7.6%. Average La- and rating of perceived exertion (RPE) did not differ between the sessions. Conclusions: Using ARDSV during SIE provokes respiratory acidosis, causes stronger acute physiological responses, and does not increase RPE.

Cardiorespiratory responses to low-level ozone exposure: The inDoor Ozone Study in childrEn (DOSE).

BACKGROUND: Indoor air pollution has emerged as a significant environmental and public health concern in recent years. However, evidence regarding the cardiorespiratory effects of indoor ozone is limited, and the underlying biological mechanisms are unclear, especially in children. Our study aimed to assess the cardiorespiratory responses to indoor ozone exposure in children. METHODS: A repeated-measure study was conducted in 46 middle-school children in Beijing, China. Real-time concentrations of ozone, along with co-pollutants including particulate matter (PM) and black carbon (BC), were monitored in classrooms from Monday to Friday. Three repeated health measurements of cardiorespiratory functions, including ambulatory electrocardiogram (ECG), blood pressure, fractional exhaled nitric oxide (FeNO) and lung function, were performed on each participant. Mixed-effect models were used to evaluate the effects of indoor ozone exposure. RESULTS: The mean (SD) indoor ozone concentration was 8.7 (6.6) ppb during the study period, which was largely below the current guideline and standards. However, even this low-level ozone exposure was associated with reduced cardiac autonomic function and increased heart rate (HR) in children. For instance, per interquartile range (IQR) increase in ozone at 2-hour moving average was associated with -7.8% (95% CI: -9.9%, -5.6%) reduction in standard deviation of all normal-to-normal intervals (SDNN), and 2.6% (95% CI: 1.6%, 3.6%) increment in HR. In addition, the associations were stronger at high BC levels (BC ≥ 3.7 µg/m3). No significant associations were found for airway inflammation and pulmonary function. CONCLUSIONS: Exposure to low-level indoor ozone that is not associated with respiratory effects was significantly related to disturbed cardiac autonomic function and increased HR in children, which suggested a possible mechanism through which ozone may affect cardiovascular health in children, and indicated more protective measures should be taken to alleviate the acute adverse effects of indoor ozone in this susceptible population.

Effects of combined supervised intermittent aerobic, muscle strength and home-based walking training programs on cardiorespiratory responses in women with breast cancer.

BACKGROUND: The aim of this investigation was to study the effects of supervised combined intermittent aerobic, muscle strength and home-based walking training programs on cardiorespiratory fitness in women with breast cancer during adjuvant chemotherapy treatment. METHODS: Thirty-two women with breast cancer undertaking adjuvant chemotherapy participated in the study (trained group n=20 and control group n=12). The trained group carried out 6weeks of supervised intermittent cycling aerobic, muscle strength and home-based walking training programs. The self-selected walking speed (WS), walking distance covered (WD), heart rate (rHR), blood lactate ([La]b) concentration and rating of perceived exertion (RPE) were assessed in the two groups during the 6-min walking test before and after the training period. RESULTS: Compared to controls, a significant increase in the WS (P<0.01) and the WD (P<0.01) accompanied by a significant decrease in resting rHR (P<0.01), exercising HR6' (P<0.01), [La]b (P<0.05), HR6'/WS (P<0.01) and [La]b/WS ratios (P<0.01) was reported in the trained group. However, a significant decrease both in WD (P<0.01) and WS (P<0.01) has been observed in the controls. No significant difference was observed in resting HR, exercising HR6', [La]b, HR6'/WS, and [La]b/WS ratios were observed in the control group. A significant improvement was observed for RPE in training group (P<0.05). However, no difference was shown in controls. CONCLUSION: Combined training based on intermittent aerobic exercise, muscle strength and walking improve cardiorespiratory responses and reduce the perception of fatigue in women with breast cancer.

Influence of water depth on energy expenditure during aquatic walking in people post stroke.

BACKGROUND AND PURPOSE: This study aimed to investigate the metabolic cost during aquatic walking at various depths in people post stroke. The secondary purpose was to examine the differences in metabolic cost between aquatic walking and land walking among individuals post stroke. DESIGN: A cross-sectional research design is used. METHODS: Twelve participants post stroke (aged 55.5 ± 13.3 years) completed 6 min of walking in 4 different conditions: chest-depth, waist-depth, and thigh-depth water, and land. Data were collected on 4 separate visits with at least 48 hr in between. On the first visit, all participants were asked to walk in chest-depth water at their fastest speed. The walking speed was used as a reference speed, which was applied to the remaining 3 walking conditions. The order of remaining walking conditions was randomized. Energy expenditure (EE), oxygen consumption (VO2 ), and minute ventilation (VE ) were measured with a telemetric metabolic system. RESULTS: Our findings showed statistically significant differences in EE, VO2 , and VE among the 4 different walking conditions: chest-depth, waist-depth, and thigh-depth water, and land (all p < .05). The participants demonstrated reduction in all variables as the water depth increased from thigh depth to chest depth. Significantly higher values in EE and VO2 were found when the water depth increased from waist depth to chest depth. However, no significant difference was found in all variables between thigh-depth and waist-depth walking. Only thigh-depth walking revealed significant differences when compared with land walking in all variables. CONCLUSIONS: People post stroke consume less energy in chest-depth water, which may allow them to perform prolonged duration of training. Thigh-depth water demonstrated greater EE compared with other water depths; thus, it can be recommended for time-efficient cardiovascular exercise. Waist-depth water showed similar EE to land walking, which may have been contributed by the countervailing effects of buoyancy and water resistance.

Acute effects of intravenous cocaine administration on serum concentrations of ghrelin, amylin, glucagon-like peptide-1, insulin, leptin and peptide YY and relationships with cardiorespiratory and subjective responses.

BACKGROUND: Food intake and use of drugs of abuse like cocaine share common central and peripheral physiological pathways. Appetitive hormones play a major role in regulating food intake; however, little is known about the effects of acute cocaine administration on the blood concentrations of these hormones in cocaine users. METHODS: We evaluated serum concentrations of six appetitive hormones: ghrelin (total and acyl-ghrelin), amylin, glucagon-like peptide-1 (GLP-1), insulin, leptin and peptide YY (PYY), as well as acute cardiorespiratory and subjective responses of 8 experienced cocaine users who received 25mg intravenous (IV) cocaine. RESULTS: Serum concentrations of GLP-1 (p=0.014) and PYY (p=0.036) were significantly decreased one hour following IV cocaine administration; there was a trend towards a decrease for insulin (p=0.055) and amylin (p=0.063) concentrations, while no significant IV cocaine effect was observed for ghrelin (total or acyl-ghrelin) or leptin concentrations (p's≫>0.5). We also observed associations between hormone concentrations acutely affected by IV cocaine (GLP-1, PYY, insulin, amylin) and some cocaine-related cardiorespiratory and subjective responses (e.g., increased heart and respiratory rates; feeling high and anxious). DISCUSSION: These findings show a significant effect of acute IV cocaine administration on some appetitive hormones and suggest potential associations between these hormones and cocaine-related cardiorespiratory and subjective responses. Additional research is needed to further investigate the potential mechanisms underlining these associations.

[Short-term exercise-based cardiac rehabilitation induced changes in cardiorespiratory, mechanical and neuromuscular responses to progressive exercise testing]. / Dissociation des réponses cardiorespiratoires et neuromusculaires à l'exercice à la suite de 4 semaines de réentraînement à l'effort chez des patients cardiaques.

Previous studies showed that changes in peak of oxygen uptake value (VO2peak) with training were poorly related to changes in Maximal Tolerated Power output (MTP) among patients with cardiovascular disease. This result could be due to a difference between cardiopulmonary adaptation to training and the skeletal muscle conditioning. OBJECTIVE: The aim of the study was to compare the responses to exercise training of electromyographic activities of vastus lateralis (rms-EMG) and respiratory parameters. METHODS: Nine cardiac patients (64.0±3.1y, 172.9±4.8cm, 83.4±16.3kg, BMI: 27.8±4.5) performed an incremental cycling exercise test to determine MTP, VO2peak and peak values of heart rate, before and after an aerobic training. Ventilatory thresholds were respectively determined as the breakpoint in the curve of carbon dioxide output against oxygen uptake plot (VT1) and the point at which the ratio of minute ventilation to carbon dioxide output starts to increase (VT2). EMGth1 and EMGth2 were defined as the first and the second breakpoints in the rms-EMG - power output relationship. RESULTS: Short-term exercise training (23.7±8.8 days) induced a significant increase in VO2peak (P=0.004), MTP (P=0.015), VT1 (P=0.001) and VT2 (P=0.001). Changes in VO2peak only attained the survival criteria (3.5±2.9mLmin-1kg-1). No significant differences (P>0.05) existed between mean power values of VT1 and EMGth1 (60.5±4.1 vs. 59.2±9.6% of MTP, respectively), or between VT2 and EMGth2 (78.3±5.7 vs. 80.2±5.2% of MTP). After training, EMGth1 occurred significantly before VT1 (60.5±6.2 vs. 64.8±4.8% of MTP, P=0.049). CONCLUSION: This might be taken into account for prescribing exercise rehabilitation according initial clinical limitations of patients.

Development of a motor driven rowing machine with automatic functional electrical stimulation controller for individuals with paraplegia; a preliminary study.

OBJECTIVE: To examine the cardiorespiratory responses of patients with spinal cord injury (SCI) paraplegia using a motor driven rowing machine. METHOD: Ten SCI patients with paraplegia [A (n=6), B (n=1), and C (n=3) by the American Spinal Injury Association impairment scale] were selected. Two rowing techniques were used. The first used a fixed seat with rowing achieved using only upper extremity movement (fixed rowing). The second used an automatically moving seat, facilitating active upper extremity movement and passive lower extremity movement via the motorized seat (motor rowing). Each patient performed two randomly assigned rowing exercise stress tests 1-3 days apart. The work rate (WR), time, respiratory exchange ratio (R), oxygen consumption (VO(2)), heart rate (HR), metabolic equivalents (METs), and rating of perceived exertion (RPE) were recorded. RESULTS: WR, time, VO(2), and METs were significantly higher after the motor rowing test than after fixed motor rowing test (p<0.05). HR after motor rowing was significantly lower than fixed rowing (p<0.05). CONCLUSION: Cardiorespiratory responses as VO(2), HR and METs can be elicited by the motor rowing for people with paraplegic SCI.

Central chemoreceptors and neural mechanisms of cardiorespiratory control

The arterial partial pressure (P CO2) of carbon dioxide is virtually constant because of the close match between the metabolic production of this gas and its excretion via breathing. Blood gas homeostasis does not rely solely on changes in lung ventilation, but also to a considerable extent on circulatory adjustments that regulate the transport of CO2 from its sites of production to the lungs. The neural mechanisms that coordinate circulatory and ventilatory changes to achieve blood gas homeostasis are the subject of this review. Emphasis will be placed on the control of sympathetic outflow by central chemoreceptors. High levels of CO2 exert an excitatory effect on sympathetic outflow that is mediated by specialized chemoreceptors such as the neurons located in the retrotrapezoid region. In addition, high CO2 causes an aversive awareness in conscious animals, activating wake-promoting pathways such as the noradrenergic neurons. These neuronal groups, which may also be directly activated by brain acidification, have projections that contribute to the CO2-induced rise in breathing and sympathetic outflow. However, since the level of activity of the retrotrapezoid nucleus is regulated by converging inputs from wake-promoting systems, behavior-specific inputs from higher centers and by chemical drive, the main focus of the present manuscript is to review the contribution of central chemoreceptors to the control of autonomic and respiratory mechanisms.