Ventilatory and circulatory responses at the onset of dominant and non-dominant limb exercise

We compared the ventilatory and circulatory responses during 20 s of light dynamic leg and arm exercises performed separately using dominant and non-dominant limbs. Seventeen subjects performed a 20-s single-leg knee extension-flexion exercise with a load of 5% of maximal muscle strength attached to the ankle. Fifteen of the seventeen subjects also did a single-arm elbow flexion-extension exercise in which a load was attached to the wrist in the same way as in the leg exercise. Similar movements were passively performed on the subjects by experimenters to avoid the effects of central command. The magnitude of change from rest (gain) in minute ventilation during passive movement (PAS) was significantly smaller in the dominant limbs than in the non-dominant limbs, though a significant difference was not detected during voluntary exercise (VOL). In contrast, heart rate and blood pressure responses did not show any differences between the dominant and non-dominant limbs during either VOL or PAS. In conclusion, the initial ventilatory response to PAS in the dominant limbs was lower than that of the non-dominant limbs, though the ventilatory response to VOL was not. Circulatory responses were not different between the dominant and non-dominant limbs. These results suggest that peripheral neural reflex during exercise could be different between dominant and non-dominant limbs and that ventilatory response at the onset of exercise might be controlled by the dual neural modulation of central command and peripheral neural reflex, resulting in the same ventilatory response to both dominant and non-dominant limb exercise.     

Strategy for respiratory exercise pattern associated with upper limb movements in COPD patients

INTRODUCTION:

Upper limb exercises are frequently used in respiratory physiotherapy, with UL elevation and controlled inspiratory timing. However, the use of expiration during upper limb elevation appears to be a strategy that could minimize the action of accessory muscles in patients with chronic obstructive pulmonary disease. In this context, little is known about the synchrony of upper limb (UL) movements associated with breathing. The aim of this study was to investigate the respiratory pattern of chronic obstructive pulmonary disease patients during different UL exercises associated with respiratory exercises.

METHODS:

Fifteen chronic obstructive pulmonary disease patients participated in this study. Respiratory pattern analysis by inductance plethysmography was performed during four types of upper limb exercises, two shoulder flexion-extension (one associated with inspiratory time during the concentric phase and the other associated with expiratory time) and two shoulder abduction-adduction (same timing as above). Statistical analysis was performed by the Kolmogorov-Smirnov test and ANOVA with Tukey tests (p≤ 0.05).

RESULTS:

The thoracoabdominal coordination measurements increased in the two exercises using both inspiration during shoulder flexion (PhRIB: 172%; PhREB: 131%; PhRTB: 142% and PhAng: 238%) as well as in shoulder horizontal abduction (PhRIB: 145%; PhREB: 109%; PhRTB: 130% and PhAng: 229%), differing from the exercises with expiration at the time of shoulder flexion and horizontal abduction.

CONCLUSION:

The exercises performed with inverted respiratory time produced less asynchrony and can be used as important strategies during physical exercise programs in these patients.     

Muscle oxygenation kinetics at the onset of exercise do not depend on exercise intensity

The purpose of this study was to determine whether the onset kinetics of muscle oxygenation in localized working muscle (mOxy) was affected by differences in exercise intensity. Five healthy male subjects exercised for 6 min at 125 W, 150 W, and 175 W, and 1 min at 300 W on a cycle ergometer. mOxy was estimated by near-infrared spectroscopy (NIRS) with a continuous wave photometer. The NIRS probe was positioned on the vastus lateralis muscle of the right leg. The relative change in mOxy was calculated from the relative change of the oxygenated hemoglobin (OxyHb) and deoxygenated hemoglobin (DeoxyHb) concentration from their resting values ([mOxy]=[OxyHb]–[DeoxyHb]). Assuming an exponential time course with time delay, the time constants of the mOxy were 5.7 (SD 2.2) s at 125 W, 5.6 (SD 1.9) s at 150 W, 6.0 (SD 2.2) s at 175 W, and 5.6 (SD 2.1) s at 300 W. The time delays of the mOxy were 6.7 (SD 4.2) s at 125 W, 8.6 (SD 1.6) s at 150 W, 6.4 (SD 3.0) s at 175 W, and 5.4 (SD 2.9) s at 300 W. The mean response times of the mOxy were 12.5 (SD 2.7) s at 125 W, 14.2 (SD 2.4) s at 150 W, 12.4 (SD 4.4) s at 175 W, and 11.0 (SD 3.1) s at 300 W. These results indicate that the kinetics of mOxy were not affected by differences in exercise intensity.     

Ventilatory and circulatory responses at the onset of exercise after eccentric exercise

The purpose of this study was to clarify whether delayed onset muscle soreness (DOMS) and muscle damage after eccentric exercise (ECC) could affect the ventilatory and circulatory responses at the onset of exercise, and whether those effects would continue after the disappearance of DOMS. Ten males participated in this study. We measured ventilatory and circulatory responses at the onset of exercise, for the first 20 s, during knee extension–relaxation voluntary exercise (VOL) and passive movement (PAS), which was achieved by the experimenter alternatively pulling ropes connected to the subjects’ ankles for the same period and frequency as during VOL. VOL and PAS were performed before, 2 days after, and 7 days after ECC. The following results were found: (1) the gain of minute ventilation at the onset of VOL at 2 days after ECC was significantly larger than that of before ECC; (2) the gain of minute ventilation at 7 days after ECC during both VOL and PAS was also enhanced significantly as compared to that of before ECC; and (3) heart rate and blood pressure responses were unchanged throughout the experimental period. In conclusion, ventilatory response at the onset of exercise is augmented during DOMS and EIMD after ECC and the enhanced ventilatory response continued after the disappearance of DOMS. It is suggested that enhanced ventilatory response during exercise after ECC is attributed to at least the changes in neural factors and that the mechanisms inducing these augmented ventilatory responses should be different during the period after ECC.     

Contribution of central and reflex nervous activity to the rapid increase in pulmonary ventilation at the start of muscular exercise in man

Summary To investigate the relative contributions of the central and peripheral neural drive to hyperventilation at the onset of muscular exercise, five volunteers were tested during the first ten breaths while performing both voluntary (VM) and passive (PM) ankle rotations with a frequency of 1 Hz and through an angle of 10°. Resulting breathing patterns for the two movements were compared. Hypocapnic hyperventilation, found in both PM and VM, indicated its neural origin. Respiratory changes were higher in VM than in PM. In both experimental conditions, increases in ventilation ( ) depended more on respiratory frequency (f) than on tidal volume (V _T). Moreover, increases inV _T adapted, breath-by-breath, to values lower than the initial ones, while increases inf rose progressively. Expiratory time was reduced more than inspiratory time (T _I); increases in inspiratory flow (V _T/T _I) depended to the same extent on changes in bothT _I andV _T. Increases in expiratory tidal volume were initially higher than in inspiratory tidal volume, thereby producing a reduction in functional residual capacity. Because PM respiratory changes could be considered to be of nervous reflex origin only, the identical breathing patterns in PM and VM indicated that the hyperventilation found also in VM was mainly of reflex origin. The increase in was considered to be dependent on a greater stimulus from muscle proprioreceptors.     

Spinal serotonin receptor activation modulates the exercise ventilatory response with increased dead space in goats

Small increases in respiratory dead space (VD) augment the exercise ventilatory response by a serotonin-dependent mechanism known as short-term modulation (STM). We tested the hypotheses that the relevant serotonin receptors for STM are in the spinal cord, and are of the 5-HT2-receptor subtype. After preparing adult female goats with a mid-thoracic (T6-T8) subarachnoid catheter, ventilation and arterial blood gases were measured at rest and during treadmill exercise (4.8 km/h; 5% grade) with and without an increased VD (0.2-0.3 L). Measurements were made before and after spinal or intravenous administration of a broad-spectrum serotonin receptor antagonist (methysergide, 1-2mg total) and a selective 5-HT2-receptor antagonist (ketanserin, 5-12 mg total). Although spinal methysergide had no effect on the exercise ventilatory response in control conditions, the augmented response with increased VD was impaired, allowing [Formula: see text] to increase from rest to exercise. Spinal methysergide diminished both mean inspiratory flow and frequency responses to exercise with increased VD. Spinal ketanserin impaired [Formula: see text] regulation with increased VD, although its ventilatory effects were less clear. Intrathecal dye injections indicated CSF drug distribution was caudal to the upper cervical spinal cord and intravenous drugs at the same total dose did not affect STM. We conclude that spinal 5-HT2 receptors modulate the exercise ventilatory response with increased VD in goats.     

Ventilatory responses to imagined exercise

We studied whether the ventilatory responses to imagined exercise are influenced by automatic processes. Twenty-nine athletes produced mental images of a sport event with successive focus on the environment, the preparation, and the exercise. Mean breathing frequency increased from 15 to 22 breaths/min. Five participants reported having voluntarily controlled breathing, two of them during preparation. Twenty participants reported that their breathing pattern changed during the experiment: 11 participants were unable to correctly report on the direction of changes in frequency, and 13 incorrectly reported changes in amplitude. This finding suggests that these changes were not voluntary in most participants and may therefore reveal automatic forebrain influences on exercise hyperpnea. However, these changes may also reflect nonspecific processes (e.g., arousal) different from those occurring during actual exercise.     

Ventilatory and circulatory responses at the onset of voluntary exercise and passive movement in children

The purpose of this study was to investigate whether or not the ventilatory and circulatory responses at the onset of voluntary exercise and passive movement, especially at the initial stage (phase I), in children are the same as in adults. Ten pre-teenage male children and ten adult men participated in this study. Voluntary exercise and passive movement were performed in a sitting position for about 20 s. Both the exercise and the movement consisted of flexion-extensions of the lower leg from a vertical to horizontal position, either voluntarily or passively, with a frequency of about 60 · min⁻¹. Inspiratory minute ventilation (V˙ _I), tidal volume (V _T), respiratory frequency, partial pressure of end-tidal CO₂ and O₂, heart rate (f _c) and mean blood pressure (BˉPˉ) before, during and after exercise or movement were measured using breath-by-breath and beat-to-beat techniques. Cardiorespiratory responses at the onset of voluntary exercise and passive movement were compared with the relative change (Δ), which was estimated from the value at rest (100%). In the present study, it was found that: (1) the V˙ _I during voluntary exercise were significantly lower in the children, mainly due to lower ΔV _T; (2) the Δf _c during voluntary exercise was almost the same in both groups, while Δf _c was significantly lower in the children during the last part of passive movement; (3) in the voluntary exercise and passive movement, the BˉPˉ in the children was increased a little or remained close to the value at rest, while it was significantly decreased in the adults. As a result, there were significant differences in ΔBˉPˉ between the two groups during voluntary exercise. These results suggest that the cardiorespiratory responses at the onset of voluntary exercise and passive movement may be modified during the growth process. Accepted: 30 June 2000     

Day-to-day changes in oxygen uptake kinetics at the onset of exercise during strenuous endurance training

Summary The aim of this study was to assess the effect of strenuous endurance training on day-to-day changes in oxygen uptake (VO₂) on-kinetics (time constant) at the onset.of exercise. Four healthy men participated in strenuous training, for 30 min·day^–1, 6 days·week^–1 for 3 weeks. The VO₂ was measured breath-by-breath every day except Sunday at exercise intensities corresponding to the lactate threshold (LT) and the onset of blood lactate accumulation (OBLA) which were obtained before training. Furthermore, an incremental exercise test was performed to determine LT, OBLA and maximal oxygen uptake (VO_2max) before and after the training period and every weekend. The 30-min heavy endurance training was performed on a cycle ergometer 5 days·week^–1 for 3 weeks. Another six men served as the control group. After training, significant reductions of the VO₂ time constant for exercise at the pretraining LT exercise intensity (P<0.05) and at OBLA exercise intensity (P<0.01) were observed, whereas the VO₂ time constants in the control group did not change significantly. A high correlation between the decrease in the VO₂ time constant and training day was observed in exercise at the pretraining LT exercise intensity (r=–0.76; P<0.001) as well as in the OBLA exercise intensity (r= –0.91; P<0.001). A significant reduction in the blood lactate concentration during submaximal exercise and in the heart rate on-kinetics was observed in the training group. Furthermore, VO₂ at LT, VO₂ at OBLA and VO_2max increased significantly after training (P<0.05) but such was not the case in the control group. These findings indicated that within a few weeks of training a rapidly improved VO₂ on-kinetics may be observed. This may be explained. by some effect of blood lactate during exercise on VO₂ on-kinetics, together with significantly improved cardiovascular kinetics at the onset of exercise.     

Oronasal breathing during exercise

The shift from nasal to oronasal breathing (ONBS) has been observed on 73 subjects with two independent methods. A first group of 63 subjects exercising on a bicycle ergometer at increasing work load (98–196 W) has been observed. On 35 subjects the highest value of ventilation attained with nasal breathing was 40.2±9.41 · min^–1 S.D. Ten subjects breathed through the mouth at all loads, while 5 never opened the mouth. On 13 subjects it was not possible to make reliable measurements. On a second group of 10 subjects utilizing a different techniques which did not need a face mask, the ventilation at which one changes the pattern of breathing was found to be 44.2±13.51·min^–1 S.D. On the same subjects nasal resistance did not show any correlation with ONBS. It is concluded that ONBS is not solely determined by nasal resistance, though an indirect effect due to hypoventilation and hence to changes in alveolar air composition cannot be ruled out. It is likely that ONBS is also influenced by psychological factors.     

The effects of sildenafil and acetazolamide on breathing efficiency and ventilatory control during hypoxic exercise

The reduced arterial oxygen tension at high altitude impairs the ability to work. Acetazolamide improves arterial oxygen saturation (SaO₂) by increasing ventilation but is associated with an increased work and cost of breathing. Depending on the settings, sildenafil can also increases SaO₂ possibly through a reduction in pulmonary hypertension and interstitial edema, which could improve ventilation–perfusion matching. The objective of this study is to determine the effects of acetazolamide and sildenafil on ventilatory control and breathing efficiency (V _E/VCO₂) during submaximal steady-state hypoxic exercise in healthy individuals. Following 18 h of hypoxic exposure in an altitude tent at an oxygen concentration of 12.5% (simulated altitude of 4,300 m), 15 participants performed 10 min of hypoxic exercise on a stationary bicycle at 40% of their sea level peak oxygen uptake (VO₂) while randomly receiving sildenafil 40 mg (SIL), acetazolamide 125 mg (ACZ) or a placebo (PLA). There was no difference in VO₂ during exercise between conditions while SaO₂ was greater with acetazolamide compared to both placebo and sildenafil. Acetazolamide increased ventilation (PLA 49.0 ± 3.2, SIL 47.7 ± 3.1, ACZ 52.1 ± 3.0 l/min) and reduced end-tidal CO₂ (P _ETCO₂) (PLA 32.1 ± 0.8, SIL 32.8 ± 0.9, ACZ 29.2 ± 0.7 mmHg) compared to placebo and sildenafil. Breathing was less efficient with acetazolamide (increased V _E/VCO₂) in comparison to placebo and sildenafil (PLA 41.5 ± 1.0, SIL 40.4 ± 1.3, ACZ 45.4 ± 1.0) while sildenafil did not change V _E/VCO₂ during hypoxic exercise. In conclusion, acetazolamide increased ventilation and reduced breathing efficiency while sildenafil did not affect breathing efficiency despite a trend toward a blunted ventilatory response, possibly due to a reduction in pulmonary hypertension and/or ventilatory drive, during submaximal hypoxic exercise in healthy individuals.     

Hormone response of diabetic patients to exercise at cool and warm temperatures

Summary Both exercise and high ambient temperatures stimulate the secretion of counterregulatory hormones which can change glucose homeostasis. We studied whether in diabetic patients there are any differences in the hormonal response to exercise performed at cool or warm ambient temperatures. A study was performed on eight male insulin-dependent patients at rest and during exercise at + 10° C and + 30° C. Exercise consisted of three consecutive 15-min periods at 60% of maximal aerobic capacity. The concentrations of plasma lactate and counterregulatory hormones at rest were similar at warm and cool temperature, whereas prolactin concentration was higher (P < 0.01) at +30° C. Exercise resulted in an increase in noradrenaline, growth hormone and prolactin (P < 0.01), prevented the diurnal decrease in cortisol, but had no effect on glucagon. Hormone responses to exercise were similar at + 10° C and at +30°C, except for cortisol and noradrenaline which showed greater responses at warm than at cool temperatures. This may have been due to the higher relative work load at warm compared to cool temperatures as suggested by the higher heart rate and greater increase of lactate at +30° C. These data indicate that within a range of ambient temperatures commonly occurring in sports, the response of counterregulatory hormones is largely independent of ambient temperature in insulin-dependent diabetic patients.     

Influence of diaphragm and rib cage muscle fatigue on breathing during endurance exercise

Inspiratory muscle fatigue (IMF) can develop during exhaustive exercise and cause tachypnea or rapid shallow breathing. We assessed the effects of rib cage muscle (RCM-F) and diaphragm fatigue (DIA-F) on breathing pattern and respiratory mechanics during high-intensity endurance exercise. Twelve healthy subjects performed a constant-load (85% maximal power) cycling test to exhaustion with prior IMF and a cycling test of similar intensity and duration without prior IMF (control). IMF was induced by resistive breathing and assessed by oesophageal and gastric twitch pressure measurements during cervical magnetic stimulation. Both RCM-F and DIA-F increased RCM and abdominal muscle force production during exercise compared to control. With RCM-F, tidal volume decreased while it increased with DIA-F. RCM-F was associated with a smaller increase in end-expiratory oesophageal pressure (i.e. decrease in lung volume) than DIA-F. These results suggest that RCM-F and not DIA-F is associated with rapid shallow breathing and that lowering the operating lung volume with DIA-F may help to preserve diaphragmatic function.     

Heart rate response at the onset of exercise in an apparently healthy cohort

Background

The exercise test is a powerful non-invasive tool for risk stratifying patients with or suspected of having cardiovascular disease (CVD). Heart rate (HR) response during and following exercise has been extensively studied. However, the clinical utility of HR response at the onset of exercise is less understood. Furthermore, conflicting reports exist regarding whether a faster vs. slower HR acceleration represents a CVD risk marker. The primary study purpose was to describe HR acceleration early in exercise in apparently healthy individuals.

Methods

Retrospective analyses were performed in a sample (N = 947) representing a range of age and fitness (11–78 years; VO_2peak 17–49 mL kg^?1 min^?1). HR response was defined over the initial 7 min of the protocol. Associations between HR acceleration and CVD risk factors were also assessed.

Results

Mean increases in HR were 18 ± 9 and 23 ± 11 beats at minute one, for men and women, respectively (p < 0.05). After adjusting for gender and pre-exercise HR, only modest associations were observed between the change in HR at minute one and body mass index, resting blood pressure, cigarette smoking, physical activity, HR reserve, and cardiorespiratory fitness.

Conclusion

There was wide variability in HR acceleration at the onset of exercise in this apparently healthy cohort. A lower increase in HR during the first minute of exercise was associated with a better CVD risk profile, including higher cardiorespiratory fitness, in apparently healthy individuals. These data suggest a greater parasympathetic influence at the onset of exercise may be protective in an asymptomatic population.     

Transient increase in femoral arterial blood flow to the contralateral non-exercising limb during one-legged exercise

We studied the effect of exercise intensity and duration on blood flow to the non-exercising leg during one-legged dynamic knee extension. Femoral arterial blood flow (FBF) to the non-exercising leg, blood pressure (BP), and heart rate (HR) were monitored during one-legged dynamic knee extension exercise at 15, 30, and 45% maximal voluntary contraction (MVC) in seven healthy females. There was an interaction between exercise intensity and duration for FBF and FVC (P < 0.01). During the initial phase of contralateral leg exercise at all intensities, FBF and femoral vascular conductance (FVC) of non-exercising leg increased, and the increase was larger at higher intensities (P < 0.01). After initial vasodilatation, FBF and FVC decreased to baseline, which suggests the vasoconstriction. However, FBF and FVC gradually increased during exercise at 15% MVC. We conclude that transient vasodilatation at the onset of exercise is followed by gradual change to vasoconstriction in non-exercising limb during dynamic one-legged exercise and these changes are exercise intensity- and duration-dependent.     

The effect of the amount of eccentric exercise on ventilatory response at the onset of exercise

We examined the effect of the amount of eccentric exercise (ECC) on ventilatory response at the onset of exercise. The first 10 s of ventilatory response to exercise while using the leg that had performed a relatively greater number of ECC repetitions was greater than that of the leg that had done relatively fewer repetitions, suggesting that ventilatory response at the onset of exercise varies with the degree of change in muscle condition after ECC.     

Inter-individual differences in breathing pattern at high levels of incremental cycling exercise in healthy subjects

Interindividual differences in the rate of changes in tidal volume (V_T) and respiratory frequency (f_R) were examined during a maximal incremental cycling exercise. The gain of the inspiratory off-switch reflex was inferred from the V_T vs. inspiratory duration (T_i) relationship. Some subjects also executed a static handgrip exercise, used as a “non-dynamic” exercise trial to study patterning of breathing.     

Ventilatory response at the onset of voluntary exercise and passive movement in endurance runners

The present study was performed to examine whether or not the ventilatory response at the onset of voluntary exercise and passive movement in endurance runners is the same as in untrained subjects. Twelve long-distance runners belonging to the varsity athletic club and 13 untrained subjects of our university participated as subjects in this study. Maximum oxygen uptake was significantly higher in the endurance runner group [mean (SD) 70.8 (4.7) ml?·?kg^?1?·?min^?1] than in the untrained group [49.8 (6.3) ml?·?kg^?1?·?min^?1]. Cardiorespiratory responses during voluntary exercise and passive movement of alternate flexion-extension of the right and left legs for about 15 s at a frequency of about 60?rpm, were determined by means of breath-by-breath techniques. Minute inspiratory ventilation (V˙ _I), tidal volume (V _T), respiratory frequency (f _b), cardiac output (Q˙ _c), stroke volume (SV) and heart rate (HR) increased significantly immediately at the onset of voluntary exercise and passive movement. The incremental rate for V˙ _I was greater than that for Q˙ _c. Average values and standard deviations of changes in V˙ _I were calculated as the difference between the mean of the first and second breath and the mean of five breaths preceding the exercise or movement. The rates obtained in voluntary exercise and passive movement in the endurance runner group [2.34 (0.82) and 1.72 (0.71 l?·?min^?1), respectively] were significantly (P<0.05) lower than those in the untrained group [4.16 (2.66) and 2.71 (1.56 l?·?min^?1), respectively]. Also changes in V _T and HR were significantly lower in the endurance group than in the untrained group with regard to both voluntary exercise and passive movement. The results suggest that the magnitude of cardiorespiratory responses at the onset of voluntary exercise and passive movement in humans is influenced by chronic endurance training for long periods.     

Effects of acute hypoxia on ventilatory response at the onset of submaximal exercise

In order to investigate the effects of acute hypoxia and accompanying hypocapnia on the ventilatory response at the onset of dynamic exercise, four healthy adult men performed 50W rectangular loads on a cycle-ergometer in normoxic (FIO2 = 0.21) and hypoxic (FIO2 = 0.11) conditions. No statistically significant differences in the initial ventilatory responses to exercise (both delta VI and delta VE assessed on a breath-by-breath basis) were found between eucapnic normoxia (PETO2 approximately 95, PETCO2 approximately 42 Torr) and hypocapnic hypoxia (PETO2 approximately 45, PETCO2 approximately 35 Torr). The present findings support the contention that the neurogenic ventilatory drive at the onset of early exercise is independent from PO2 and PCO2.