Controlled Frequency Breathing Research Articles

Effect of Moderate- or High-Intensity Inspiratory Muscle Strength Training on Maximal Inspiratory Mouth Pressure and Swimming Performance in Highly Trained Competitive Swimmers.

Inspiratory muscle strength training (IMST) can improve exercise performance. Increased maximal inspiratory mouth pressure (MIP) could be beneficial for swimmers to enhance their performance. This study aimed to clarify the effect of high-intensity IMST for 6weeks on MIP and swimming performance in highly trained competitive swimmers. Thirty male highly trained competitive swimmers were assigned to high-intensity IMST (HI; n = 10), moderate-intensity IMST (MOD; n = 10), and control (n = 10) groups. The 6-week IMST intervention comprised twice daily sessions for 6d/wk at inspiratory pressure threshold loads equivalent to 75% MIP (HI) and 50% MIP (MOD). Before and after the intervention, MIP and swimming performance were assessed. Swimming performance was evaluated in free and controlled frequency breathing 100-m freestyle swimming time trials in a 25-m pool. For controlled frequency breathing, participants took 1 breath every 6 strokes. The MIP values after 2 and 6 weeks of IMST in the HI and MOD groups were significantly higher than those before IMST (P = .0001). The magnitudes of the MIP increases after 6 weeks of IMST did not differ between the HI (13.4% [8.7%]) and MOD (13.1% [10.1%]) groups (P = .44). The 100-m freestyle swimming times under the controlled frequency condition were significantly shorter after IMST than those before IMST in both the HI (P = .046) and MOD (P = .042) groups. Inspiratory pressure threshold load equivalent to 50% MIP could be sufficient to improve MIP and swimming performance under the controlled frequency breathing condition in highly trained competitive swimmers.

Controlled Frequency Breathing Reduces Inspiratory Muscle Fatigue.

Burtch, AR, Ogle, BT, Sims, PA, Harms, CA, Symons, TB, Folz, RJ, and Zavorsky, GS. Controlled frequency breathing reduces inspiratory muscle fatigue. J Strength Cond Res 31(5): 1273-1281, 2017-Controlled frequency breathing (CFB) is a common swim training modality involving holding one's breath for approximately 7-10 strokes before taking another breath. We sought to examine the effects of CFB training on reducing respiratory muscle fatigue. Competitive college swimmers were randomly divided into either the CFB group that breathed every 7-10 strokes or a control group that breathed every 3-4 strokes. Twenty swimmers completed the study. The training intervention included 5-6 weeks (16 sessions) of 12 × 50-m repetitions with breathing 8-10 breaths per 50-m (control group) or 2-3 breaths per 50-m (CFB group). Inspiratory muscle fatigue was defined as the decrease in maximal inspiratory pressure (MIP) between rest and 46 seconds after a 200-yard freestyle swimming race (115 seconds [SD 7]). Aerobic capacity, pulmonary diffusing capacity, and running economy were also measured pre- and posttraining. Pooled results demonstrated a 12% decrease in MIP at 46 seconds post-race (-15 [SD 14] cm H2O, effect size = -0.48, p < 0.01). After 4 weeks of training, only the CFB group prevented a decline in MIP values before to 46 seconds after race (-2 [13] cm H2O, p > 0.05). However, swimming performance, aerobic capacity, pulmonary diffusing capacity, and running economy did not improve (p > 0.05) posttraining in either group. In conclusion, CFB training appears to prevent inspiratory muscle fatigue; yet, no difference was found in performance outcomes.

Effects of controlled frequency breathing on muscle oxygenation during swimming

Effects of controlled frequency breathing on muscle oxygenation during swimming

Respiratory modulation of human autonomic function on Earth.

We studied healthy supine astronauts on Earth with electrocardiogram, non-invasive arterial pressure, respiratory carbon dioxide concentrations, breathing depth and sympathetic nerve recordings. The null hypotheses were that heart beat interval fluctuations at usual breathing frequencies are baroreflex mediated, that they persist during apnoea, and that autonomic responses to apnoea result from changes of chemoreceptor, baroreceptor or lung stretch receptor inputs. R-R interval fluctuations at usual breathing frequencies are unlikely to be baroreflex mediated, and disappear during apnoea. The subjects' responses to apnoea could not be attributed to changes of central chemoreceptor activity (hypocapnia prevailed); altered arterial baroreceptor input (vagal baroreflex gain declined and muscle sympathetic nerve burst areas, frequencies and probabilities increased, even as arterial pressure climbed to new levels); or altered pulmonary stretch receptor activity (major breathing frequency and tidal volume changes did not alter vagal tone or sympathetic activity). Apnoea responses of healthy subjects may result from changes of central respiratory motoneurone activity. We studied eight healthy, supine astronauts on Earth, who followed a simple protocol: they breathed at fixed or random frequencies, hyperventilated and then stopped breathing, as a means to modulate and expose to view important, but obscure central neurophysiological mechanisms. Our recordings included the electrocardiogram, finger photoplethysmographic arterial pressure, tidal volume, respiratory carbon dioxide concentrations and peroneal nerve muscle sympathetic activity. Arterial pressure, vagal tone and muscle sympathetic outflow were comparable during spontaneous and controlled-frequency breathing. Compared with spontaneous, 0.1 and 0.05Hz breathing, however, breathing at usual frequencies (∼0.25Hz) lowered arterial baroreflex gain, and provoked smaller arterial pressure and R-R interval fluctuations, which were separated by intervals that were likely to be too short and variable to be attributed to baroreflex physiology. R-R interval fluctuations at usual breathing frequencies disappear during apnoea, and thus cannot provide evidence for the existence of a central respiratory oscillation. Apnoea sets in motion a continuous and ever changing reorganization of the relations among stimulatory and inhibitory inputs and autonomic outputs, which, in our study, could not be attributed to altered chemoreceptor, baroreceptor, or pulmonary stretch receptor activity. We suggest that responses of healthy subjects to apnoea are driven importantly, and possibly prepotently, by changes of central respiratory motoneurone activity. The companion article extends these observations and asks the question, Might terrestrial responses to our 20 min breathing protocol find expression as long-term neuroplasticity in serial measurements made over 20 days during and following space travel?

Assessment of the Effects of Controlled Frequency Breathing on Lactate Levels in Swimming

Assessment of the Effects of Controlled Frequency Breathing on Lactate Levels in Swimming A randomly assigned maximal effort 100-yd swim test was conducted twice, once with normal breathing (NB) pattern (1 breath every 2-3 strokes), and the second using controlled frequency breathing (CFB) pattern (1 breath every 7 strokes) in 21 trained female swimmers (19.0 ± 1.1 years). Post-swim blood lactate levels, heart rate, and time to completion were measured and assessed after completion of each bout. Blood samples were taken from the earlobe at rest (prior to the bout), 0-min,1.5-min, 3-min, and 5-min post-swim. Heart rate was taken at rest and at the same time points as blood lactate.

Is resistance exercise with controlled frequency breathing superior to training of the same program with normal breathing? – future challenges

The specific internal environment in the body during exercise can influence the muscle hypertrophy and strength response. Unlike chronic hypoxic exposure, exercise training under intermittent hypoxia may lead to muscle hypertrophy with relatively low workloads. Objectives: The purpose of this brief review is to discuss how a hypoxic condition can be attained without providing ambient inspiratory hypoxic gases or inducing hypobaric hypoxia. Design and Methods: Evidence-based implications and future challenges. Results: Pulse oximetry is a simple method that measures percutaneous oxygen saturation (SpO2). Several studies reported that hypoxia is produced with increasing duration of apnea, especially in the last half of the breath-hold, with SpO2 reaching levels as low as 80%. Similarly, studies have reported changes in SpO2 during dynamic exercise at various workloads with controlled frequency breathing. Conclusions and future challenges: These results suggest a possibility that moderate- or high-intensity exercise combined with controlled frequency breathing may produce a low level of SpO2, which may be a model for muscle hypertrophy by moderate- or high-intensity exercise training with hypoxia. However, there are no published studies on the effects of resistance exercise with controlled frequency breathing on muscle size and function. Additionally, it is unclear the magnitude change in SpO2 during resistance exercise with a combination of different frequencies of breathing and various workloads. Furthermore, the safety of such a technique, particularly with respect to hypercapnia and the possible elevation of arterial pressures, is also unknown and should be investigated further.

Point:Counterpoint: Respiratory sinus arrhythmia is due to a central mechanism vs. respiratory sinus arrhythmia is due to the baroreflex mechanism

Blood pressure and heart periods fluctuate at respiratory frequencies in healthy humans. Some researchers ([8][1], [23][2]) explain this as a cause-and-effect relation: blood pressure changes trigger baroreflex-mediated R-R interval changes. Here I make the case that respiratory sinus arrhythmia is

Examination of controlled frequency breathing under conditions of changing walk cadence

Examination of controlled frequency breathing under conditions of changing walk cadence

BLOOD LACTATE AND METABOLIC RESPONSES TO CONTROLLED FREQUENCY BREATHING DURING GRADED SWIMMING

Controlled frequency breathing (CFB) is a training technique used by swimmers in an effort to simulate high-intensity workloads by limiting oxygen availability to the body and stimulating anaerobic metabolism. During CFB, a swimmer voluntarily restricts breathing, which, theoretically, limits oxygen availability and stimulates anaerobic metabolism. The purpose of this study was to determine the influence of CFB on blood lactate and metabolic responses during graded increases in swimming intensity. A free swimming (FS) protocol was used to determine blood lactate and heart rate (HR) responses to CFB, while a tethered swimming (TS) protocol was used to determine blood lactate, HR, and ventilatory responses to CFB. The subjects swam four 3-minute trials at workloads of 55, 65, 75, and 85% of peak intensity during both protocols. A total of 46 competitive collegiate swimmers participated in the study. Thirty-four subjects (14 men and 20 women) completed the FS protocol, and 12 subjects (7 men and 5 women) completed the TS protocol. CFB reduced ventilation and VO2 (p < 0.05) during the TS protocol and reduced HR (p < 0.05) during the FS protocol when compared to normal breathing. However, CFB did not alter blood lactate concentrations for either protocol (p > 0.05). Our findings demonstrate that although CFB does not alter the blood lactate response to graded increases in swimming intensity, it appears to reduce the ventilatory and HR responses to exercise. Thus, swim coaches can use CFB at moderate intensities to simulate high-intensity training but should consider adjusting HR training zones to reflect the reduction in HR associated with reduced ventilation.

Heart Rate Variability and Spontaneous Baroreflex Sequences: Implications for Autonomic Monitoring During Hemorrhage

Noninvasive procedures for predicting progression to hemodynamic instability during induced central hypovolemia in humans were evaluated. The purpose of this study was twofold: (1) to track changes in autonomic function induced by a model of hemorrhage, and (2) to determine whether measures of autonomic function are reliable without strict control of breathing. Electrocardiogram, respiratory frequency, and arterial pressure during progressive lower body negative pressure were recorded for 10 subjects, and for a separate sample of 20 subjects during 5-minute periods of spontaneous breathing or controlled-frequency breathing at 15 breaths per minute.. Heart rate variability was calculated in both time and frequency domains. Up and down baroreflex sequences were calculated with linear regression analysis between sequential changes in systolic pressures and accompanying parallel changes in R-R intervals. Heart rate variability (r = 0.92) and up (r = 0.90) and down (r = 0.96) sequences changed in direct inverse relation to decreased central volume as produced by progressive increases in lower body negative pressure, whereas mean arterial pressures remained constant (r = 0.26). Neither heart rate variability nor up and down baroreflex sequences were affected by the mode of breathing. Analysis of heart rate variability and baroreflex sequences in hemorrhaging patients may provide advance recognition of those at risk for progression to shock. In conjunction with more traditional modes of assessing volume status, tracking early changes in autonomic function may improve resuscitation efforts for the hemodynamic compromised patient.

Blood Lactate and Metabolic Responses to Controlled Frequency Breathing During Graded Swimming

Controlled frequency breathing (CFB) is a training technique used by swimmers in an effort to simulate high-intensity workloads by limiting oxygen availability to the body and stimulating anaerobic metabolism. During CFB, a swimmer voluntarily restricts breathing, which, theoretically, limits oxygen availability and stimulates anaerobic metabolism. The purpose of this study was to determine the influence of CFB on blood lactate and metabolic responses during graded increases in swimming intensity. A free swimming (FS) protocol was used to determine blood lactate and heart rate (HR) responses to CFB, while a tethered swimming (TS) protocol was used to determine blood lactate, HR, and ventilatory responses to CFB. The subjects swam four 3-minute trials at workloads of 55, 65, 75, and 85% of peak intensity during both protocols. A total of 46 competitive collegiate swimmers participated in the study. Thirty-four subjects (14 men and 20 women) completed the FS protocol, and 12 subjects (7 men and 5 women) completed the TS protocol. CFB reduced ventilation and Vo(2) (p < 0.05) during the TS protocol and reduced HR (p < 0.05) during the FS protocol when compared to normal breathing. However, CFB did not alter blood lactate concentrations for either protocol (p > 0.05). Our findings demonstrate that although CFB does not alter the blood lactate response to graded increases in swimming intensity, it appears to reduce the ventilatory and HR responses to exercise. Thus, swim coaches can use CFB at moderate intensities to simulate high-intensity training but should consider adjusting HR training zones to reflect the reduction in HR associated with reduced ventilation.

No Effect of Menstrual Phase on Cardiovascular Hemodynamic or Autonomic Responses to Orthostatic Stress

1460 Estrogens are powerful vasodilators, and changes in estrogen concentrations across the menstrual cycle could affect regional fluid pooling and compensatory autonomic responses to an orthostatic challenge. PURPOSE: To compare cardiovascular hemodynamic and autonomic responses in women during low- and high-estrogen phases of the menstrual cycle during graded, progressive lower body negative pressure (LBNP). METHODS: Eight young (age 21.8 ± 2.2 yr) eumenorrheic women were studied twice, once during low-estrogen (0–5 day) and once during high-estrogen (20–25 day) phases of the menstrual cycle. Plasma estradiol levels were measured, and then subjects were instrumented with a 3-lead ECG, pneumobelt for respiratory excursions, finger photoplethysmograph for beat-by-beat blood pressure, and segmental bioimpedance for estimation of fluid shifts (thorax, pelvis, and leg). Subjects were placed in an air-tight chamber at the level of the iliac crest. Data were collected during 5 min of controlled frequency breathing (0.25 Hz) at 0, −10, −20, −30, −40 and −50 mmHg chamber decompression and analyzed in both time and frequency domains. RESULTS: Estradiol concentrations were 48 ± 6 and 147 ± 26 pg/ml during days 0–5 and 20–25 (p<0.05). R-R interval and R-R interval spectral power, stroke volume and cardiac output, and systolic pressure to R-R interval transfer function magnitude decreased progressively during LBNP (p<0.05). Mean arterial pressure was maintained with increases of peripheral resistance. Segmental fluid shifts and cardiovascular responses to LBNP were not different during high- and low-estrogen phases. CONCLUSION: Despite increased potential for vascular dilation with high plasma estradiol concentrations, our results demonstrate normal cardiovascular hemodynamic and autonomic compensatory responses in young eumenorrheic women to simulated orthostatic stress during different menstrual phases. Supported by NIH Grant R15 HL67787-01

No Effect of Menstrual Phase on Cardiovascular Hemodynamic or Autonomic Responses to Orthostatic Stress

1460 Estrogens are powerful vasodilators, and changes in estrogen concentrations across the menstrual cycle could affect regional fluid pooling and compensatory autonomic responses to an orthostatic challenge. PURPOSE: To compare cardiovascular hemodynamic and autonomic responses in women during low- and high-estrogen phases of the menstrual cycle during graded, progressive lower body negative pressure (LBNP). METHODS: Eight young (age 21.8 ± 2.2 yr) eumenorrheic women were studied twice, once during low-estrogen (0–5 day) and once during high-estrogen (20–25 day) phases of the menstrual cycle. Plasma estradiol levels were measured, and then subjects were instrumented with a 3-lead ECG, pneumobelt for respiratory excursions, finger photoplethysmograph for beat-by-beat blood pressure, and segmental bioimpedance for estimation of fluid shifts (thorax, pelvis, and leg). Subjects were placed in an air-tight chamber at the level of the iliac crest. Data were collected during 5 min of controlled frequency breathing (0.25 Hz) at 0, −10, −20, −30, −40 and −50 mmHg chamber decompression and analyzed in both time and frequency domains. RESULTS: Estradiol concentrations were 48 ± 6 and 147 ± 26 pg/ml during days 0–5 and 20–25 (p<0.05). R-R interval and R-R interval spectral power, stroke volume and cardiac output, and systolic pressure to R-R interval transfer function magnitude decreased progressively during LBNP (p<0.05). Mean arterial pressure was maintained with increases of peripheral resistance. Segmental fluid shifts and cardiovascular responses to LBNP were not different during high- and low-estrogen phases. CONCLUSION: Despite increased potential for vascular dilation with high plasma estradiol concentrations, our results demonstrate normal cardiovascular hemodynamic and autonomic compensatory responses in young eumenorrheic women to simulated orthostatic stress during different menstrual phases. Supported by NIH Grant R15 HL67787-01

METABOLIC AND BIOMECHANIC CHANGES DURING CONTROLLED FREQUENCY BREATHING SWIMMING

Controlled frequency breathing (CFB) is a training technique used by swimmers in an effort to limit oxygen availability to the body and stimulate anaerobic metabolism. PURPOSE: The purpose of these studies was to determine the influence of CFB on metabolic and biomechanic responses during front crawl stroke swimming using both a tethered swimming protocol and a free swimming protocol. METHODS: A maximal exertion test was used to assign workloads based on peak exercise capacity. Subjects swam three minute workloads at 55%, 65%, 75% and 85% of maximal exertion for the tethered swimming protocols and 55–95% for the free swimming protocol with either normal breathing (NB) or CFB restricted to eight strokes per breath. The tethered swimming protocol was done so that oxygen consumption could be measured. The free swimming protocol was done to more closely mimic a normal swimming workout. Lactate and heart rate were measured immediately after each workload and stroke rate was counted manually. Multivariate analyses were used to compare the oxygen consumption, lactate, heart rate, and stroke rate between NB and CFB. RESULTS: Twelve subjects completed the tethered protocol and twenty-eight subjects completed the free-swimming protocol. As expected there were significant main effects for the oxygen consumption, heart rate and lactate responses to increasing workloads (P < 0.01). However, restricted breathing did not alter lactate levels, despite reductions in oxygen consumption. Heart rate (P = 0.014) and stroke rate (P = 0.011) were both higher during CFB. CONCLUSIONS: These results indicate that restricting breathing to one breath every eight strokes does not alter blood lactate levels, elevates heart rate, and may compromise stroke biomechanics.

Impairment of Autonomic Function Induced by Posture Change in Postmenopausal Women

This study was designed to determine if there is a difference in autonomic regulation induced by posture change between postmenopausal and young women. To evaluate autonomic nervous system function, spectral analysis of heart rate variability (HRV) was done in postmenopausal women (n = 13, 46-59 years of age), age-matched men (n = 8, 45-55 years of age), and young women (n = 10, 20-37 years of age) for 3-min periods of controlled frequency breathing (15 breaths/min) in supine followed by sitting positions. In the supine position, the R-R interval variation in older persons decreased significantly compared with that during the follicular phase in young women. Furthermore, the high-frequency (HF) components of HRV, which reflect only parasympathetic activity, were lower in older subjects than in young women. Following a change of position from supine to sitting, the HF component did not change significantly in the postmenopausal women or the men, but the low/high frequency (LF/HF) component ratio, which reflects the balance of autonomic nerve activities, increased significantly in the men. These results suggest that cardiac parasympathetic tone may be reduced in older persons in comparison with young women. Furthermore, arterial baroreflex control of parasympathetic nerve activity caused by posture changes is impaired in the postmenopausal women and aged-matched men. The baroreflex control of the sympathetic component is maintained in the men but not in the postmenopausal women. These differences might result in part from changes in the level of female hormones.

Reflex control of autonomic function induced by posture change during the menstrual cycle

This study was designed to determine whether autonomic regulation induced by posture changes varies during the menstrual cycle. Heart rate variability (HRV) was analyzed in women with normal menstrual cycles ( n=10, age range 20–37 years) during 3 min periods of controlled frequency breathing (15 breaths/min) in supine followed by sitting positions. In a supine or sitting position, high frequency (HF) components of HRV, which reflects only parasympathetic activity, were significantly high in the follicular phase compared with those in the menstrual phase, suggesting that parasympathetic nerve activity increases in this phase. Following the change of position to sitting from supine, the HF component decreased significantly in the menstrual, ovulatory and luteal phases, but not the follicular or premenstrual phase. After changing the position to sitting, the low to high frequency component ratio, which reflects the balance of autonomic nerve activities, was increased significantly in the menstrual, luteal and premenstrual phases, indicating that sympathetic nerve activities in these phases became predominant by the sitting position. These results suggest that parasympathetic nerve activity is predominant in the follicular phase, resulting in an impairment of baroreflex caused by posture changes. Moreover, baroreflex control of the sympathetic component, not the parasympathetic component, increases in the premenstrual phase, while the reflex response of the sympathetic component is less in the ovulatory phase compared with the menstrual or luteal phase. We concluded that baroreflex regulation of autonomic functions induced by changing positions is modified during the menstrual cycle. A difference of a balance of ovarian hormones may be responsible for these changes of autonomic functions during the menstrual cycle.

HEART RATE VARIABILITY IS NOT RELATED TO FITNESS OR PHYSICAL ACTIVITY IN SEDENTARY ADULTS 992

To test the hypothesis that autonomic modulation of heart rate is related to fitness and/or physical activity we measured indices of short term heart rate variability (HRV) during controlled frequency breathing (0.2 Hz) in the seated position and compared them with VO2MAX (incremental GXT), and calories/week from a standardized 7-day physical activity recall (PAR) interview. The subjects were sedentary individuals (137 M and 257 F, mean age 52.3, range 35-75) enrolled in the Activity Counseling Trial (ACT) study. HRV was measured in the time domain from the standard deviation (SDNN), variance(SDNN)2 and coefficient of variation (SD/mean = CV) of the R-R intervals and in the frequency domain by power spectral analysis of two, 256 beat epochs (mod. Welch method). Absolute (PSD) and normalized (norm) power were measured at low (LF, 0.04-0.15 Hz), high (HF, 0.15-0.5 Hz) and total power (TP, 0.01-0.5 Hz) and LF/HF ratio. Partial correlation coefficients (r) for VO2MAX or PAR vs. HRV were determined after removing effects of gender. Results: There was no significant correlation between HRV and PAR. For VO2max vs HRV (*P<0.05) VO2MAX = 23±6.5 ml/kg/min Table Although some of the r values are statistically significant no correlation appeared physiologically significant and < 5% of the variance in HRV could be explained by a variation in VO2MAX in this preliminary cross-sectional analyses of a sedentary population. We speculate that increases in fitness and activity will be associated with increases in HRV. This hypothesis will be tested in the ACT intervention study

Elevated heart rate variability in physically active postmenopausal women: a cardioprotective effect?

Coronary heart disease (CHD) and cardiac sudden death (CSD) incidence accelerates after menopause, but the incidence is lower in physically active versus less active women. Low heart rate variability (HRV) is a risk factor for CHD and CSD. The purpose of the present investigation was to test the hypothesis that HRV at rest is greater in physically active compared with less active postmenopausal women. If true, we further hypothesized that the greater HRV in the physically active women would be closely associated with an elevated spontaneous cardiac baroreflex sensitivity (SBRS). HRV (both time and frequency domain measures) and SBRS (sequence method) were measured during 5-min periods of controlled frequency breathing (15 breaths/min) in the supine, sitting, and standing postures in 9 physically active postmenopausal women (age = 53 +/- 1 yr) and 11 age-matched controls (age = 56 +/- 2 yr). Body weight, body mass index, and body fat percentage were lower (P < 0.01) and maximal oxygen uptake was higher (P < 0.01) in the physically active group. The standard deviation of the R-R intervals (time domain measure) was higher in all postures in the active women (P < 0.05) as were the high-frequency, low-frequency, and total power of HRV. SBRS also was higher (P < 0.05) in the physically active women in all postures and accounted for approximately 70% of the variance in the high-frequency power of HRV (P < 0.05). The results of the present investigation indicate that physically active postmenopausal women demonstrate higher levels of HRV compared with age-matched, less active women. Furthermore, SBRS accounted for the majority of the variance in the high-frequency power of HRV, suggesting the possibility of a mechanistic link with cardiac vagal modulation of heart rate. Our findings may provide insight into a possible cardioprotective mechanism in physically active postmenopausal women.

Fundamental Relations Between Short-term RR Interval and Arterial Pressure Oscillations in Humans

One of the principal explanations for respiratory sinus arrhythmia is that it reflects arterial baroreflex buffering of respiration-induced arterial pressure fluctuations. If this explanation is correct, then elimination of RR interval fluctuations should increase respiratory arterial pressure fluctuations. We measured RR interval and arterial pressure fluctuations during normal sinus rhythm and fixed-rate atrial pacing at 17.2+/-1.8 (SEM) beats per minute greater than the sinus rate in 16 healthy men and 4 healthy women, 20 to 34 years of age. Measurements were made during controlled-frequency breathing (15 breaths per minute or 0.25 Hz) with subjects in the supine and 40 degree head-up tilt positions. We characterized RR interval and arterial pressure variabilities in low-frequency (0.05 to 0.15 Hz) and respiratory-frequency (0.20 to 0.30 Hz) ranges with fast Fourier transform power spectra and used cross-spectral analysis to determine the phase relation between the two signals. As expected, cardiac pacing eliminated beat-to-beat RR interval variability. Against expectations, however, cardiac pacing in the supine position significantly reduced arterial pressure oscillations in the respiratory frequency (systolic, 6.8+/-1.8 to 2.9 +/-0.6 mm Hg2/Hz, P=.017). In contrast, cardiac pacing in the 40 degree tilt position increased arterial pressure variability (systolic, 8.0+/-1.8 to 10.8 +/-2.6, P=.027). Cross-spectral analysis showed that 40 degree tilt shifted the phase relation between systolic pressure and RR interval at the respiratory frequency from positive to negative (9 +/-7 degrees versus -17+/-11 degrees, P=.04); that is, in the supine position, RR interval changes appeared to lead arterial pressure changes, and in the upright position, RR interval changes appeared to follow arterial pressure changes. These results demonstrate that respiratory sinus arrhythmia can actually contribute to respiratory arterial pressure fluctuations. Therefore, respiratory sinus arrhythmia does not represent simple baroreflex buffering of arterial pressure.

Influence of physical responses due to controlled frequency breathing during exercise

The purpose of this study was to examine the influence of respiratory responses due to controlled frequency breathing (CFB) during steady state cycle ergometric exercise (50% of Peak VO2, 60rpm) and to compare their responses between long distance (L), badminton (B), Swimming (S) and untrained (C; Control) group. Twenty-two (n = 6; L, B, C.n = 4; S) female university students were forced to take CFB for 1 min every 3 min during 20 min exercise. The breathing frequencies (BR) were 10, 12, 15, 20 and 30 frequencies in a minute. They were represented by CFB10, CFB12, CFB15, CFB20 and CFB30 respectively. In addition, CFB5, and 40 were given in a separate series. Ventiratory volume (VE) decreased significantly, (P < 0.05) when BR decreased less than about 50% of normal breathing (NB), CFB15 in (B) and (C). It showed to be less than CFB12 in (S), and CFB10 in (L). According to the decrease of VE, tidal volume and O2 pulse increased during CFB10 and 15 in all groups to maintain a constant O2 consumption for a given workload. End tidal partial pressure of O2 (PETO2) significantly decreased during less than CFB15 in (B) and (C), during CFB10 in (L). PETCO2 increased during less than CFB15 in (B), less than CFB12 in (L) and (C). However in (S) during every CFB, neither PETO2 nor PETCO2 changed significantly. Talking about the main differences shown between the four groups, (S) and (L) significantly exceeded (C) in maintaining of VE during CFB. However, in consideration of a ratio of the frequency of CFB to that of NB, (L) could maintain VE against more strictly controlled of breathing than other groups. (B) showed similar tendencies as (C) about some responses. It is considered that these differences in respiratory responses to CFB may result from difference of the duration and the level of breathing control that were forced during their daily training rather than whether their breathing frequency during each exercise is high or low.