Effect of coupling the breathing- and cycling rhythms on oxygen uptake during bicycle ergometry

Locomotor-Respiratory Entrainment upon Phonated Compared to Spontaneous Breathing during Submaximal Exercise

Recently, increased attention to breathing techniques during exercise has addressed the need for more in-depth study of the ergogenic effects of breathing manipulation. The physiological effects of phonation, as a potential breathing tool, have not yet been studied. Thus, the aim of this study was to investigate the respiratory, metabolic and hemodynamic responses of phonated exhalation and its impact on locomotor-respiratory entrainment in young healthy adults during moderate exercise. Twenty-six young, healthy participants were subjected to peak expiratory flow (PEF) measurements and a moderate steady cycling protocol based on three different breathing patterns (BrP): spontaneous breathing (BrP1), phonated breathing pronouncing "h" (BrP2) and phonated breathing pronouncing "ss" (BrP3). The heart rate, arterial blood pressure, oxygen consumption, CO2 production, respiratory rate (RR), tidal volume (VT), respiratory exchange ratio and ventilatory equivalents for both important respiratory gasses (eqO2 and eqCO2) were measured (Cosmed, Italy) simultaneously during a short period of moderate stationary cycling at a predefined cadence. To evaluate the psychological outcomes, the rate of perceived exertion (RPE) was recorded after each cycling protocol. The locomotor-respiratory frequency coupling was calculated at each BrP, and dominant coupling was determined. Phonation gradually decreased the PEF (388 ± 54 L/min at BrP2 and 234 ± 54 L/min at BrP3 compared to 455 ± 42 L/min upon spontaneous breathing) and affected the RR (18.8 ± 5.0 min-1 at BrP2 compared to 22.6 ± 5.5 min-1 at BrP1 and 21.3 ± 7.2 min-1 at BrP3), VT (2.33 ± 0.53 L at BrP2 compared to 1.86 ± 0.46 L at BrP1 and 2.00 ± 0.45 L at BrP3), dominant locomotor-respiratory coupling (1:4 at BrP2 compared to 1:3 at BrP1 and BrP2) and RPE (10.27 ± 2.00 at BrP1 compared to 11.95 ± 1.79 at BrP1 and 11.95 ± 1.01 at BrP3) but not any other respiratory, metabolic or hemodynamic measures of the healthy adults during moderate cycling. The ventilatory efficiency was shown to improve upon dominant locomotor-respiratory coupling, regardless of BrP (eqO2 = 21.8 ± 2.2 and eqCO2 = 24.0 ± 1.9), compared to the other entrainment coupling regimes (25.3 ± 1.9, 27.3 ± 1.7) and no entrainment (24.8 ± 1.5, 26.5 ± 1.3), respectively. No interaction between phonated breathing and entrainment was observed during moderate cycling. We showed, for the first time, that phonation can be used as a simple tool to manipulate expiratory flow. Furthermore, our results indicated that in young healthy adults, entrainment, rather than expiratory resistance, preferentially affected ergogenic enhancement upon moderate stationary cycling. It can only be speculated that phonation would be a good strategy to increase exercise tolerance among COPD patients or to boost the respiratory efficiency of healthy people at higher exercise loads.

Step-adaptive sound guidance enhances locomotor-respiratory coupling in novice female runners: A proof-of-concept study

Introduction

Many runners struggle to find a rhythm during running. This may be because 20-40% of runners experience unexplained, unpleasant breathlessness at exercise onset. Locomotor-respiratory coupling (LRC), a synchronization phenomenon in which the breath is precisely timed with the steps, may provide metabolic or perceptual benefits to address these limitations. It can also be consciously performed. Hence, we developed a custom smartphone application to provide real-time LRC guidance based on individual step rate.

Methods

Sixteen novice-intermediate female runners completed two control runs outdoors and indoors at a self-selected speed with auditory step rate feedback. Then, the runs were replicated with individualized breath guidance at specific LRC ratios. Hexoskin smart shirts were worn and analyzed with custom algorithms to estimate continuous LRC frequency and phase coupling.

Results

LRC guidance led to a large significant increase in frequency coupling outdoor from 26.3 ± 10.7 (control) to 69.9 ± 20.0 % (LRC) "attached". There were similarly large differences in phase coupling between paired trials, and LRC adherence was stronger for the indoor treadmill runs versus outdoors. There was large inter-individual variability in running pace, preferred LRC ratio, and instruction adherence metrics.

Discussion

Our approach demonstrates how personalized, step-adaptive sound guidance can be used to support this breathing strategy in novice runners. Subsequent investigations should evaluate the skill learning of LRC on a longer time basis to effectively clarify its risks and advantages.

Integrating Wearable Sensors and Video to Determine Microlocation-Specific Physiologic and Motion Biometrics-Method Development for Competitive Climbing

Competitive indoor climbing has increased in popularity at the youth, collegiate, and Olympic levels. A critical aspect for improving performance is characterizing the physiologic response to different climbing strategies (e.g., work/rest patterns, pacing) and techniques (e.g., body position and movement) relative to location on climbing wall with spatially varying characteristics (e.g., wall inclinations, position of foot/hand holds). However, this response is not well understood due to the limited capabilities of climbing-specific measurement and assessment tools. In this study, we developed a novel method to examine time-resolved sensor-based measurements of multiple personal biometrics at different microlocations (finely spaced positions; MLs) along a climbing route. For the ML-specific biometric system (MLBS), we integrated continuous data from wearable biometric sensors and smartphone-based video during climbing, with a customized visualization and analysis system to determine three physiologic parameters (heart rate, breathing rate, ventilation rate) and one body movement parameter (hip acceleration), which are automatically time-matched to the corresponding video frame to determine ML-specific biometrics. Key features include: (1) biometric sensors that are seamlessly embedded in the fabric of an athletic compression shirt, and do not interfere with climbing performance, (2) climbing video, and (3) an interactive graphical user interface to rapidly visualize and analyze the time-matched biometrics and climbing video, determine timing sequence between the biometrics at key events, and calculate summary statistics. To demonstrate the capabilities of MLBS, we examined the relationship between changes in ML-specific climbing characteristics and changes in the physiologic parameters. Our study demonstrates the ability of MLBS to determine multiple time-resolved biometrics at different MLs, in support of developing and assessing different climbing strategies and training methods to help improve performance.

Breath Tools: A Synthesis of Evidence-Based Breathing Strategies to Enhance Human Running

Running is among the most popular sporting hobbies and often chosen specifically for intrinsic psychological benefits. However, up to 40% of runners may experience exercise-induced dyspnoea as a result of cascading physiological phenomena, possibly causing negative psychological states or barriers to participation. Breathing techniques such as slow, deep breathing have proven benefits at rest, but it is unclear if they can be used during exercise to address respiratory limitations or improve performance. While direct experimental evidence is limited, diverse findings from exercise physiology and sports science combined with anecdotal knowledge from Yoga, meditation, and breathwork suggest that many aspects of breathing could be improved via purposeful strategies. Hence, we sought to synthesize these disparate sources to create a new theoretical framework called “Breath Tools” proposing breathing strategies for use during running to improve tolerance, performance, and lower barriers to long-term enjoyment.

Time- and Frequency-Domain Analysis of Stroke Volume Variability Using Indoor Cycling to Evaluate Physical Load of Body

A potential myocardial injury can be induced by intensive sporting activities, which may be due to ventricular tachycardia or fibrillation when individuals continue to exercise during the maximum physical loading period (the aerobic capability plateau, ACP). Herein, we conducted an incremental exercise test with the RR-interval and SV-series measurements as the input and output of the circulatory system. Through time and frequency analyses, we aimed to identify the indicators for distinguishing the normal stage (S1), last stage before ACP (S2), and ACP stage (S3) during different incremental physical loads. The cross-correlation results of the RR interval and SV series showed that the maximum coefficient of S2 was significantly greater (p < 0.05) than that of S1 (median 0.91 to 0.87), and also significantly lower (p < 0.05) than that of S3 (median 0.87 to 0.60). The corresponding spectrum shows that the decreasing correlation coefficient of SVV and Heart rate variability can be used to assess whether the body has reached the ACP. These findings can be used as a guide for exercise healthcare. Pausing or reducing the exercise load before entering the ACP could effectively reduce the risk of myocardial injury.

Maltodextrin-Based Carbohydrate Oral Rinsing and Exercise Performance: Systematic Review and Meta-Analysis

Background

Carbohydrates are an important fuel for optimal exercise performance during moderate- and high-intensity exercise; however, carbohydrate ingestion during high-intensity exercise may cause gastrointestinal upset. A carbohydrate oral rinse is an alternative method to improve exercise performance in moderate- to high-intensity exercise with a duration of 30–75 min. This is the first systematic review and meta-analysis to comprehensively examine the isolated effect of maltodextrin-based rinsing on exercise performance.

Objective

The objective of this review was to establish the effect of a maltodextrin-based carbohydrate oral rinse on exercise performance across various modes of exercise. Furthermore, a secondary objective was to determine the effects of moderators [(1) participant characteristics; (2) oral rinse protocols; (3) exercise protocol (i.e. cycling, running etc.) and (4) fasting] on exercise performance while using a maltodextrin-based, carbohydrate oral rinse.

Methods

Five databases (MEDLINE, PsycINFO, Embase, SPORTDiscus and Global Health) were systematically searched for articles up to March 2021 and screened using Covidence (a systematic review management tool). A random effects robust meta-analysis and subgroup analyses were performed using Stata Statistical Software: Release 16.

Results

Thirty-five articles met the inclusion criteria and were included in the systematic review; 34 of these articles were included in the meta-analysis. When using a conventional meta-analytic approach, overall, a carbohydrate oral rinse improved exercise performance in comparison with a placebo (SMD = 0.15, 95% CI 0.04, 0.27; p = 0.01). Furthermore, when implementing an adjusted, conservative, random effects meta-regression model using robust variance estimation, overall, compared with placebo, a carbohydrate oral rinse demonstrated evidence of improving exercise performance with a small effect size (SMD = 0.17, 95% CI − 0.01, 0.34; p = 0.051).

Conclusion

This systematic review and meta-analysis demonstrates that a maltodextrin-based carbohydrate oral rinse can improve exercise performance. When comparing the two meta-analytic approaches, although non-significant, the more robust, adjusted, random effects meta-regression model demonstrated some evidence of a maltodextrin-based carbohydrate oral rinse improving exercise performance overall.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-022-01658-3.

Attentional focus does not impact locomotor-respiratory coupling in trained runners

PURPOSE

The purpose of this study was to explore relationships between attentional strategies and LRC, running economy, perceived exertion, and dyspnea.

METHODS

25 endurance-trained males ([Formula: see text]O₂max = 68.2 ± 4.7 mL kg^-1 min^-1) ran for 5 min each at two different submaximal speeds, during which LRC and oxygen consumption ([Formula: see text]O₂) were measured. The degree of LRC was calculated as the percentage of breaths occurring during the same decile of the step cycle. Attentional focus was assessed at the end of exercise using an Attentional Focusing Questionnaire, with subscales for association, dissociation, and distress.

RESULTS

We found no significant relationships between attentional focus measures and LRC. However, dissociation scores were positively correlated with [Formula: see text]O₂ (r = 0.404), as well as  %[Formula: see text]O_2max (r = 0.474), at the slower running speed. Distress scores were the only attentional focus subscale related to perceived exertion and dyspnea (r = 0.378 to 0.654).

CONCLUSION

These findings suggest attentional focus is not driving the high levels of LRC seen in trained endurance athletes but may relate to running economy and perceptual responses.

Energy efficient physiologic coupling of gait and respiration is altered in chronic obstructive pulmonary disease

AIMS

Coupling between walking and breathing in humans is well established. In healthy systems, the ability to couple and uncouple leads to energy economization. It is unknown if physiologic efficiency is susceptible to alteration, particularly in individuals with airflow obstruction. The aim of this research was to determine if coupling was compromised in a disease characterized by abnormal airflow and dyspnoea, and if this was associated with reduced energy efficiency.

METHODS

As a model of airflow obstruction, 17 chronic obstructive pulmonary disease (COPD) patients and 23 control subjects were included and walked on a treadmill for 6 minutes at three speeds (preferred speed and ±20% preferred speed) while energy expenditure, breathing, and walking were recorded. Rating of perceived exertion was recorded at the end of each walking trial. The most commonly used frequency ratio (ie, strides:breath) and cross recurrence quantification analysis were used to quantify coupling. Linear regression models were used to determine associations.

RESULTS

Less complex frequency ratios, simpler ratios, (ie, 1:1 and 3:2) accompanied with stronger coupling were moderately associated with increased energy expenditure in COPD subjects. This was found for all three speeds.

CONCLUSION

The novel finding was that increased energy expenditure was associated with stronger and less complex coupling. Increased effort is needed when utilizing a frequency ratio of 1:1 or 3:2. The more stable the coupling, the more effort it takes to walk. In contrast to the complex energy efficient coupling of controls, those with airflow obstruction manifested simpler and stronger coupling associated with reduced energy efficiency.

Locomotor-respiratory coupling is maintained in simulated moderate altitude in trained distance runners

To determine whether acute exposure to simulated moderate altitude alters locomotor-respiratory coupling (LRC) patterns in runners, 13 trained male distance runners performed a running economy and maximal oxygen uptake (V̇o2max) test in normoxia (NORM) and hypoxia (HYP) ([Formula: see text]= 15.8%; ~2,400 m/8,000 ft) on separate days. Running economy (RE), the degree of LRC, stride frequency-to-breathing frequency quotients (SF/fb), ratings of perceived exertion (RPE), and dyspnea were assessed at three common submaximal speeds and V̇o2max. SF/fb were significantly lower at each submaximal speed in HYP (12.9 km/h: 2.91 ± 0.20 vs. 2.45 ± 0.17, 14.3 km/h: 2.53 ± 0.17 vs. 2.21 ± 0.14, 16.1 km/h: 2.22 ± 0.14 vs. 1.95 ± 0.09; P < 0.05). The degree of LRC (range: 36–99%) in HYP was not significantly different than NORM at any of the three common submaximal speeds. However, the degree of LRC was significantly higher at V̇o2max in HYP than NORM (43.8 ± 3.4% vs. 57.1 ± 3.8%; P < 0.05). RE and RPE were similar at all running speeds. Dyspnea was significantly greater in HYP compared with NORM at 16.1 km/h ( P < 0.05). Trained distance runners are able to maintain LRC in HYP, despite increases in breathing frequency. Within this unique population, years of training may enhance and optimize the ability to maintain LRC to minimize metabolic costs and dyspnea.

NEW & NOTEWORTHY Exposure to acute altitude causes increases in ventilation at rest and any submaximal exercising workload, which may alter locomotor-respiratory coupling (LRC). Our data suggest that trained distance runners can maintain LRC during acute exposure to simulated moderate altitude, even when breathing frequency is increased at any submaximal pace.

Effect of cadence on locomotor-respiratory coupling during upper-body exercise

Introduction

Asynchronous arm-cranking performed at high cadences elicits greater cardiorespiratory responses compared to low cadences. This has been attributed to increased postural demand and locomotor–respiratory coupling (LRC), and yet, this has not been empirically tested. This study aimed to assess the effects of cadence on cardiorespiratory responses and LRC during upper-body exercise.

Methods

Eight recreationally-active men performed arm-cranking exercise at moderate and severe intensities that were separated by 10 min of rest. At each intensity, participants exercised for 4 min at each of three cadences (50, 70, and 90 rev min⁻¹) in a random order, with 4 min rest-periods applied in-between cadences. Exercise measures included LRC via whole- and half-integer ratios, cardiorespiratory function, perceptions of effort (RPE and dyspnoea), and diaphragm EMG using an oesophageal catheter.

Results

The prevalence of LRC during moderate exercise was highest at 70 vs. 50 rev min⁻¹ (27 ± 10 vs. 13 ± 9%, p = 0.000) and during severe exercise at 90 vs. 50 rev min⁻¹ (24 ± 7 vs. 18 ± 5%, p = 0.034), with a shorter inspiratory time and higher mean inspiratory flow (p < 0.05) at higher cadences. During moderate exercise, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}{\text{O}}_{ 2} $$\end{document}V˙O2 and f_C were higher at 90 rev min⁻¹ (p < 0.05) relative to 70 and 50 rev min⁻¹ (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}{\text{O}}_{ 2} $$\end{document}V˙O2 1.19 ± 0.25 vs. 1.05 ± 0.21 vs. 0.97 ± 0.24 L min⁻¹; f_C 116 ± 11 vs. 101 ± 13 vs. 101 ± 12 b min⁻¹), with concomitantly elevated dyspnoea. There were no discernible cadence-mediated effects on diaphragm EMG.

Conclusion

Participants engage in LRC to a greater extent at moderate-high cadences which, in turn, increase respiratory airflow. Cadence rate should be carefully considered when designing aerobic training programmes involving the upper-limbs.

Runners maintain locomotor-respiratory coupling following isocapnic voluntary hyperpnea to task failure

INTRODUCTION

Evidence has long suggested that mammalian ventilatory and locomotor rhythms are linked, yet determinants and implications of locomotor-respiratory coupling (LRC) continue to be investigated. Anecdotally, respiratory muscle fatigue seen at the end of heavy exercise may result in an uncoupling of movement-ventilation rhythms; however, there is no scientific evidence to substantiate this claim.

PURPOSE

We sought to determine whether or not fatigue of the respiratory muscles alters locomotor-respiratory coupling patterns typically observed in highly trained individuals while running. A related query was to examine the relationship between the potential changes in LRC and measures of running economy.

METHOD

Twelve male distance runners ran at four submaximal workloads (68-89 % VO2peak) on two separate days while LRC was quantified. One LRC trial served as a control (CON), while the other was performed following an isocapnic voluntary hyperpnea to task failure to induce respiratory muscle fatigue (FT+). LRC was assessed as stride-to-breathing frequency ratios (SF/fB) and degree of LRC (percentage of breaths occurring during the same decile of the step cycle).

RESULT

Hyperpnea resulted in significant declines in maximal voluntary inspiratory (MIP) and expiratory (MEP) mouth pressures (ΔMIP = -10 ± 12 cm H2O; ΔMEP = -6 ± 9 cm H2O). There were no differences in minute ventilation between CON and FT+ (CON, all speeds pooled = 104 ± 25 L min(-1); FT+ pooled = 106 ± 23 L min(-1)). Stride frequency was not different between trials; however, breathing frequency was significantly greater during FT+ compared to CON at all speeds (CON pooled = 47 ± 10 br min(-1); FT+ pooled = 52 ± 9 br min(-1)), resulting in smaller corresponding SF/fB. Yet, the degree of LRC was the same during CON and FT+ (CON pooled = 63 ± 15 %; FT+ pooled = 64 ± 18 %).

CONCLUSION

The results indicate that trained runners are able to continue entraining breath and step cycles, despite marked changes in exercise breathing frequency, after a fatiguing hyperpnea challenge.

Grouping feedback components by common fate benefits motor-respiratory coordination

The purpose of this study was to see how motor-respiratory coordination could improve with augmented visual feedback. Participants performed inphase and antiphase patterns between movement and breathing. When the target pattern was performed properly, balls in a feedback display either moved up and down together (inphase feedback) or opposite each other (antiphase feedback). Relative phase performance was less variable in the augmented feedback conditions than in a no display control condition. Within the augmented feedback conditions, variability was lower with inphase feedback than antiphase feedback. Cross-recurrence analysis was used to determine whether other changes occurred on shorter time scales. On cross-recurrence measures, performance was more variable with inphase feedback than in the control condition and with antiphase feedback. Those results suggest that, with inphase feedback, participants were able to achieve more stable overall relative phase patterns using small within-cycle trajectory changes. Those small changes were possible because the balls in the inphase feedback display were grouped by common fate. That perceptual organization made it possible for participants to see slight mismatches between movement and breathing and control coordination accordingly.

The relationship between climbing ability and physiological responses to rock climbing

Aim. The aim of this study was to examine the relationship between submaximal and maximal physiological responses to rock climbing for climbers of differing abilities. Methods. Twenty-six male climbers performed a submaximal climbing test on a known circuit at 90° (vertical) and 105° (15° overhanging) inclination and speed 25 movements·min⁻¹. A maximal test was undertaken on a similar circuit at the same speed with inclination increasing by 10° for each successive 3 min stage. Results. Mean oxygen consumption and heart rate (HR) increased with wall inclination and climbers reached a mean (±SD) peak V˙O2 of 40.3 ± 3.5 mL·kg⁻¹·min⁻¹ during the maximal test. Self-reported climbing ability was negatively correlated with V˙O2 and HR during the submaximal test at 90° (V˙O2, r = −0.82; HR, and r = −0.66) and at 105° (V˙O2, r = −0.84; HR, and r = −0.78) suggesting an increased exercise economy for climbers with a higher ability level. Conclusion. Findings from this study indicate that there is a relationship between wall inclination and the physiological demand of a climb. However, the increased technical ability and fitness of higher level climbers appears to an extent to offset the increased demand through improved exercise economy which in turn leads to an increased time to exhaustion and an improvement in performance.

Locomotor-respiratory coupling patterns and oxygen consumption during walking above and below preferred stride frequency

Locomotor respiratory coupling patterns in humans have been assessed on the basis of the interaction between different physiological and motor subsystems; these interactions have implications for movement economy. A complex and dynamical systems framework may provide more insight than entrainment into the variability and adaptability of these rhythms and their coupling. The purpose of this study was to investigate the relationship between steady state locomotor-respiratory coordination dynamics and oxygen consumption [Formula: see text] of the movement by varying walking stride frequency from preferred. Twelve male participants walked on a treadmill at a self-selected speed. Stride frequency was varied from -20 to +20% of preferred stride frequency (PSF) while respiratory airflow, gas exchange variables, and stride kinematics were recorded. Discrete relative phase and return map techniques were used to evaluate the strength, stability, and variability of both frequency and phase couplings. Analysis of [Formula: see text] during steady-state walking showed a U-shaped response (P = 0.002) with a minimum at PSF and PSF - 10%. Locomotor-respiratory frequency coupling strength was not greater (P = 0.375) at PSF than any other stride frequency condition. The dominant coupling across all conditions was 2:1 with greater occurrences at the lower stride frequencies. Variability in coupling was the greatest during PSF, indicating an exploration of coupling strategies to search for the coupling frequency strategy with the least oxygen consumption. Contrary to the belief that increased strength of frequency coupling would decrease oxygen consumption; these results conclude that it is the increased variability of frequency coupling that results in lower oxygen consumption.

Displays that facilitate performance of multifrequency ratios during motor-respiratory coordination

A large number of ratios between movement and breathing are possible, but only a small number have been performed during exercise. The purpose of this study was twofold: (1) to investigate displays that might facilitate the performance of other ratios; and (2) to test predictions from the sine circle map and continued fractions in a model motor-respiratory task in which participants coordinated arm movement and breathing. Displays consisted of either real-time feedback or a template (non-feedback). The accuracy of ratio performance was significantly greater with the template in which the number and relative positioning of movements and breaths was depicted, compared to with real-time feedback. Across displays, the stability of ratio performance conformed to principles of the sine circle map and was significantly greater for ratios with longer continued fractions. Therefore, the motor-respiratory repertoire can be expanded by increasing participants' understanding of the pattern to be performed, but performance is constrained by general dynamical principles.

Paced Breathing in Roller-Ski Skating: Effects on Metabolic Rate and Poling Forces

Purpose:

This study aimed (1) to determine whether paced breathing (synchronization of the expiration phase with poling time) would reduce the metabolic rate and dictate a lower rate of perceived exertion (RPE) than does spontaneous breathing and (2) to analyze the effects of paced breathing on poling forces and stride-mechanics organization during roller-ski skating exercises.

Methods:

Thirteen well-trained cross-country skiers performed 8 submaximal roller-skiing exercises on a motorized driven treadmill with 4 modes of skiing (2 skating techniques, V2 and V2A, at 2 exercise intensities) by using 2 patterns of breathing (unconscious vs conscious). Poling forces and stride-mechanics organization were measured with a transducer mounted in ski poles. Oxygen uptake (VO2) was continuously collected. After each bout of exercise RPE was assessed by the subject.

Results:

No difference was observed for VO2 between spontaneous and paced breathing conditions, although RPE was lower with paced breathing (P < .05). Upper-limb cycle time and recovery time were significantly (P < .05) increased by paced breathing during V2A regardless of the exercise intensity, but no changes for poling time were observed. A slight trend of increased peak force with paced breathing was observed (P = .055).

Conclusion:

The lack of a marked effect of paced breathing on VO2 and some biomechanical variables could be explained by the extensive experience of our subjects in cross-country skiing.

Neuro-mechanical and chemical influences on locomotor respiratory coupling in humans

Mechanisms of coordination between breathing and movement during dynamic exercise are still a matter of debate. This study aimed to examine the degree of coordination between breathing and arm propulsion patterns and to compare the relative contribution of neuro-mechanical and chemical factors. Thirteen trained cross-country skiers performed constant submaximal 6-min roller skiing exercises on a motorized driven treadmill in two different poling techniques (V2A and V2 skating techniques) at two exercise intensity levels corresponding to the first and second ventilatory thresholds. The timing of arm propulsion movements in V2A and V2 techniques was considered as a mechanical/neural influence on breathing whereas exercise intensity represented the metabolic demand to breathing. The degree of coordination, expressed as the percentage of breaths presenting a constant phase interval (time between an arbitrarily chosen point of the arm movement cycle and the onset of expiration) was significantly higher in V2A than V2 (P<0.05) while exercise intensity had no effect on the degree of coordination. We concluded that locomotor-respiratory coupling occurs in cross-country skiing as simulated by roller skiing because of strong influences from neuro-mechanical factors.

Entrainment of breathing in cyclists and non-cyclists during arm and leg exercise

The purpose of this study was to compare the incidence of entrainment of breathing (ENT) between cyclists (C; n=8) and non-cyclists (NC; n=8) during leg cycling (LC) and arm cycling (AC). No subjects were training regularly in upper body endurance exercise. Day 1 consisted of spirometry and a VO2max test on both an arm and leg ergometer in random order separated by at least 60 min. On Day 2, subjects performed both AC and LC exercise with each session consisting of 5 min of warm-up at 20% and three consecutive 6 min loads at 40%, 60%, and 80% of task specific peak power output (WL1, WL2, WL3, respectively). Sessions were separated by at least 45 min. The final 3 min of each load were analyzed for entrainment of pedal and breathing frequencies using integer and half-integer ratios. A total of six subjects were unable to complete at least one exercise session at WL3 and therefore this load was excluded from analysis. Mean % VO2max during exercise was not different between cyclists and controls with respect to intensity and mode (AC= approximately 50% and 70%; LC= approximately 55% and 75% at WL1 and WL2, respectively). A repeated measures ANOVA revealed no effect on incidence of entrainment (%ENT) by group, mode of exercise, or exercise intensity (p=0.12, 0.24, and 0.88, respectively). %ENT was highest in cyclists during leg exercise (cyclists: LC=32%; AC=19%; controls: LC=18%; AC=21%) however this difference was not significant (p=0.07). In all situations that would be considered unfamiliar for both groups %ENT was similar. These results suggest that during cycling exercise at intensities of 75% VO2max or less, regular training may result in higher %ENT and that ENT is not transferable to an unfamiliar mode of exercise using different muscle groups.

Multiple time scales and subsystem embedding in the learning of juggling

To gain insight into the multiform dynamics and integration of remote yet pertinent subsystems into the performance of complex perceptual-motor skills, we recently conducted a series of longitudinal and cross-sectional experiments on the acquisition of 3-ball cascade juggling in which we measured, next to the ball trajectories, postural sway, eye and head movements and respiration. The aim of the present paper is to review the main results and theoretical implications of these experimental studies for understanding skill acquisition. As regards the evolution of the quality of the juggling itself, we found that only certain aspects of throwing and catching were adjusted, while the goal behavior of sustained juggling (operationalized as the number of consecutive throws) and the degree of frequency and phase locking between the ball trajectories, indexing pattern stability, increased monotonically. The latter three aspects evolved at different rates, reflecting the existence of a temporal hierarchy in learning. Postural sway exhibited initial manifestations of task-specific, possibly mechanically induced, modes of 3:1 and 3:2 frequency locking with the ball trajectories and only few transitions between those modes. Functional stability appeared to be enhanced during practice by minimizing the sway amplitudes rather than by adjusting the sway dynamics itself. Eye and point-of-gaze movements also showed instances of 3:1 and 3:2 frequency locking with the ball trajectories; especially establishing a 3:1 locking (horizontal eye movements) appeared to be important. Expert behavior suggested that extended practice promotes reliance on multiple sources of information, allowing the proficient juggler to switch adaptively between functional organizations involving distinct perceptual systems. No consistent coordination between breathing and juggling was found. It was concluded that multiform dynamics, involving hierarchically ordered time scales, underlie the acquisition of complex skills and that the subsystems subserving realization of the task goal become assembled and embedded in a task- and subsystem-specific manner.

Sex differences in respiratory exercise physiology

Respiratory exercise physiology research has historically focused on male subjects. In the last 20 years, important physiological and functional differences have been noted between the male and female response to dynamic exercise where sex differences have been reported for most of the major determinants of exercise capacity. Female participation in competitive and recreational sport is growing worldwide and it is universally accepted that participation in regular physical activity is of health benefit for both sexes. Understanding sex differences is of potential importance to both the clinician-scientist and the exercise physiologist since differences could impact upon exercise rehabilitation programmes for patient populations, exercise prescription for disease prevention in healthy individuals and training strategies for competitive athletes. Sex differences have been shown in resting pulmonary function, which may impact on the respiratory response to exercise. Women typically have smaller lung volumes and maximal expiratory flow rates even when corrected for height relative to men. Differences in resting and exercising ventilation across the menstrual cycle and relative to men have also been reported, although the functional significance remains unclear. Expiratory flow limitation and a high work of breathing are seen in women. Pulmonary system limitations, in particular exercise-induced arterial hypoxia, have been reported in both men and women; however, the prevalence in women is not yet known. From the available literature, it appears that there are sex differences in some areas of respiratory exercise physiology. However, detailed sex comparisons are difficult because the number of subjects studied to date has been woefully small.

Arterial desaturation during exercise in man: implication for O2 uptake and work capacity

Exercise-induced arterial hypoxaemia is defined as a reduction in the arterial O2 pressure (PaO2) by more than 1 kPa and/or a haemoglobin O2 saturation (SaO2) below 95%. With blood gas analyses ideally reported at the actual body temperature, desaturation is a consistent finding during maximal ergometer rowing. Arterial desaturation is most pronounced at the end of a maximal exercise bout, whereas the reduction in PaO2 is established from the onset of exercise. Exercise-induced arterial hypoxaemia is multifactorial. The ability to maintain a high alveolar O2 pressure (PAO2) is critical for blood oxygenation and this appears to be difficult in large individuals. A large lung capacity and, in turn, diffusion capacity seem to protect PaO2. A widening of the PAO2-PaO2 difference does indicate that a diffusion limitation, a ventilation-perfusion mismatch and/or a shunt influence the transport of O2 from alveoli to the pulmonary capillaries. An inspired O2 fraction of 0.30 reduces the widened PAO2-PaO2 difference by 75% and prevents a reduction of PaO2 and SaO2. With a marked increase in cardiac output, diffusion limitation combined with a fast transit time dominates the O2 transport problem. Furthermore, a postexercise reduction in pulmonary diffusion capacity suggests that the alveolo-capillary membrane is affected. An antioxidant attenuates oxidative burst by neutrophilic granulocytes, but it does not affect PaO2, SaO2 or O2 uptake (VO2), and the ventilatory response to maximal exercise also remains the same. It is proposed, though, that increased concentration of certain cytokines correlates to exercise-induced hypoxaemia as cytokines stimulate mast cells and basophilic granulocytes to degranulate histamine. The basophil count increases during maximal rowing. Equally, histamine release is associated with hypoxaemia and when the release of histamine is prevented, the reduction in PaO2 is attenuated. During maximal exercise, an extreme lactate spill-over to blood allows pH decrease to below 7.1 and according to the O2 dissociation curve this is critical for SaO2. When infusion of sodium bicarbonate maintains a stable blood buffer capacity, acidosis is attenuated and SaO2 increases from 89% to 95%. This enables exercise capacity to increase, an effect also seen when O2 supplementation to inspired air restores arterial oxygenation. In that case, exercise capacity increases less than can be explained by VO2 and CaO2. Furthermore, the change in muscle oxygenation during maximal exercise is not affected when hyperoxia and sodium bicarbonate attenuate desaturation. It is proposed that other organs benefit from enhanced O2 availability, and especially the brain appears to increase its oxygenation during maximal exercise with hyperoxia.

Running training and adaptive strategies of locomotor-respiratory coordination

It has been suggested that stronger coupling between locomotory and breathing rhythms may occur as a result of training in the particular movement pattern and also may reduce the perceived workload or metabolic cost of the movement. Research findings on human locomotor-respiratory coordination are equivocal, due in part to the fact that assessment techniques range in sensitivity to important aspects of coordination (e.g. temporal ordering of patterns, half-integer couplings and changes in frequency and phase coupling). An additional aspect that has not received much attention is the adaptability of this coordination to changes in task constraints. The current study investigated the effect of running training on the locomotor-respiratory coordination and the adaptive strategies observed across a wide range of walking and running speeds. Locomotor-respiratory coordination was evaluated by the strength and variability of both frequency and phase coupling patterns that subjects displayed within and across the speed conditions. Male subjects (five runners, five non-runners) locomoted at seven different treadmill speeds. Group results indicated no differences between runners and non-runners with respect to breathing parameters, stride parameters, as well as the strength and variability of the coupling at each speed. Individual results, however, showed that grouping subjects masks large individual differences and strategies across speeds. Coupling strategies indicated that runners show more stable dominant couplings across locomotory speeds than non-runners do. These findings suggest that running training does not change the strength of locomotor-respiratory coupling but rather how these systems adapt to changing speeds.

Gender differences in workload effect on coordination between breathing and cycling

PURPOSE

To investigate the gender differences in the effect of increasing workload level and thus of an increasing metabolic drive to ventilation on the degree of coordination between breathing and cycling rhythms.

METHODS

Twenty-one men and 21 women cycled on an electromagnetically braked ergometer while breathing through a pneumotachograph at workloads corresponding to 55, 75, and 95% of V0(2peak) (WL1, WL2, and WL3). Leg movements, respiratory parameters, and heart rate were continuously recorded. The degree of coordination (%coord) was quantified as the percentage of breaths starting during the same phase of leg movement.

RESULTS

In men, %coord increased with increasing exercise intensity (WL1: mean +/- SE = 18.8 +/- 2.6%, WL2: 30.9 +/- 4.9%, WL3: 40.9 +/- 5.6%), whereas in women exercise intensity had no influence on %coord (WL1: 25.0 +/- 5.0%, WL2: 29.7 +/- 5.1, WL3: 31.7 +/- 4.7%). There were no gender differences in breathing pattern during high metabolic demands. A major effect on %coord came from the regularity of the breathing rhythm, whereas cycling frequency, fitness level, or cycling experience exerted no influence.

CONCLUSIONS

The present study demonstrates that the effect of exercise intensity on the occurrence of coordination between breathing and cycling rhythms differs between men and women.

Ventilatory and gas exchange responses under spontaneous and fixed breathing modes during arm exercise

To evaluate the difference of ventilatory and gas exchange response differences between arm and leg exercise, six healthy young men underwent ramp exercise testing at a rate of 15 W.min-1 on a cycle ergometer separately under either spontaneous (SPNT) or fixed (FIX) breathing modes, respectively. Controlled breathing was defined as a breathing frequency (fb; 30 breaths.min-1) which was neither equal to, nor a multiple of, cranking frequency (50 rev.min-1) to prevent coupling of locomotion and respiratory movement, i.e., so-called locomotor-respiratory coupling (LRC). Breath-by-breath oxygen uptake (VO2), ventilation (VE), CO2 output (VCO2), tidal volume (VT), fb and end-tidal PCO2 (PETCO2) were determined using a computerized metabolic cart. Arm exercise engendered a higher level of VO2 at each work rate than leg exercise under both FIX and SPNT conditions. However, FIX did not notably affect the VO2 response during either arm or leg exercise at each work rate compared to SPNT. During SPNT a significantly higher fb and lower PETCO2 during arm exercise was found compared with leg exercise up to a fb of 30 breaths.min-1 while VE and VT were nearly the same. During fixed breathing when fb was fixed at a higher rate than during SPNT, a significantly lower PETCO2 was observed during both exercise modes. These results suggest that: 1) FIX breathing does not affect the VO2 response during either arm or leg exercise even when non-synchronization between limb locomotion movement and breathing rate was adopted; 2) at a fb of 30 breaths.min-1 FIX breathing induced a hyperventilation resulting in a lower PETCO2 which was not associated with the metabolic rate during either arm or leg exercise, showing that VE during only leg exercise under the FIX condition was significantly higher than under the SPNT condition.

Measurement of ventilatory threshold by respiratory frequency

This study was conducted to assess whether respiratory frequency can be used as a valid parameter for estimating ventilatory threshold and for examining differences in exercise modes such as a cycle ergometer and a treadmill. 24 men and 12 women performed an incremental exercise test to exhaustion on a cycle ergometer and on a treadmill. Oxygen uptake, carbon dioxide output, pulmonary ventilation, ventilatory frequency, and heart rate were measured continuously every 30 sec. during the test. Three different and independent reviewers detected the ventilatory threshold point and break point of respiratory rate, which were then compared. Analysis indicated that (1) ventilatory threshold was well correlated with break point of respiratory rate for both cycle (r=.88, p<.001) and treadmill exercise (r=.96, p<.001). However, on the average, ventilatory threshold was only 71% (cycle) or 88% (treadmill) of break point of respiratory rate. (2) The regression equation for treadmill exercise was more accurate than that for cycling, but the detected data samples were smaller. The break point of respiratory rate was more easily detected for the cycle ergometer test 33 of 36 subjects) than for the treadmill test (only 15 of 36). The cycle ergometer test identified the break point of respiratory rate more easily than did the treadmill test. (3) There was an association between physical fitness and whether the break point of respiratory rate was detectable, and the more fit the subject (above average), the more likely the break point was to be undetected. Our study demonstrates that the break point of respiratory rate is closely associated with ventilatory threshold and that the cycle ergometer test is more conducive than the treadmill test to the detectability of break point of respiratory rate.

Locomotor-respiratory coupling during axillary crutch ambulation

OBJECTIVE

To test the hypotheses that locomotor-respiratory coupling occurs in humans using axillary crutches in a swing-through ambulation pattern and that expiration occurs during crutch-stance phase during locomotor-respiratory coupling.

DESIGN

Eighteen able-bodied persons were trained in one-footed swing-through gait with axillary crutches. Then, as subjects walked at "somewhat hard" speeds (Borg) on a motorized treadmill for 5 min, we recorded signals from a crutch pressure switch and a mouthpiece-mounted thermocouple. Coupling was defined as being present when the onset of inspiration varied by < or = 5% with respect to the onset of the crutch gait cycle for a minimum of 10 consecutive gait cycles and when there was no drift on a raster plot of the respiratory phases relative to the onset of the gait cycle.

RESULTS

Ten (56%) of the 18 subjects exhibited locomotor-respiratory coupling on 1-4 occasions each, with episodes lasting 11.3-148 sec. In 17 (89%) of the 19 episodes of 1:1 locomotor-respiratory coupling, expiration occurred during the crutch-stance phase of the gait cycle and inspiration occurred during crutch swing.

CONCLUSIONS

Transient 1:1 locomotor-respiratory coupling occurs in many able-bodied subjects ambulating with axillary crutches and a swing-through gait. Expiration is most often associated with the crutch-stance phase of the gait cycle. This study may have implications for training axillary crutch users.

Coupling of breathing and movement during manual wheelchair propulsion

The hypothesis of this study was that stable coordination patterns may be found both within and between physiological subsystems. Many studies have been conducted on both monofrequency and multifrequency coordination, with a focus on both the frequency and phase relations among the limbs. In the present study, locomotor-respiratory coupling was observed in the maintenance of small-integer frequency ratios (2:1, 3:1, and 4:1) and in the consistent placement of the inspiratory phase just after the onset of the movement cycle during wheelchair propulsion. Level of experience and various motor and respiratory parameters were manipulated. Coupling was observed across levels of experience. Increases in movement frequency were accompanied by a shift to larger-integer ratios, suggesting that a single modeling strategy (e.g., the Farey tree; D. L. González & O. Piro, 1985) may be used for coordination both within the motor subsystem and between it and other physiological subsystems.

Physiological profiles of Australian surf boat rowers

The physiological profiles of 17 open grade (OG) and 13 reserve grade (RG) male surfboat rowers (SBR) aged 19-44 years were determined and compared. Parameters investigated included anthropometry, agility, isometric strength, flexibility, rowing ergometer performance (MT), peak VO2 and arterialised blood pH, lactate and bicarbonate. Means were compared using t-tests. Multiple regression analyses provided a number of models for the prediction of MT performance in SBR. The mean age, height, mass, and sum of eight skinfolds for SBR are: 26.2 (+/-5.9) years, 180.5 (+/-6.0) cm, 84.4 (+/-9.3) kg and 78.2 (+/-26.2) mm respectively. OG rowers were significantly different from RG for the parameters of ergometer performance (OG: 1360.2+/-42.9 m; RG: 1316.4+/-41.8 m), peak ventilation (OG: 174.2+/-17.2 L x min(-1); RG: 154.8+/-22.1 L x min(-1)), and post exercise blood pH levels (OG: 6.98+/-0.07; RG: 7.04+/-0.07). Performance on a rowing ergometer successfully discriminates between OG and RG rowers with the best predictors of ergometer performance in SBR being height, peak ventilation, and post exercise pH.

Relationship between Respiratory Movements and Energy Efficiency in the Post-Exercise Recovery Phase

The breathing movement is highly automated but it can be voluntarily controlled in some situations. Compared with period of exercise and post-exercise, subjects could control breathing more voluntarily in the post-exercise recovery phase. So, we analyzed relationship between the strategy for controlling the breathing movement pattern and energy efficiency in this phase. Fifteen healthy men (mean age, 22.1 years) were subjected to exercise with a bicycle ergometer at 100 W for 5 minutes, then respiratory pattern was measured four times for 5 minutes after exercise. The measurement items were 1) chest expansion, 2) abdomen expansion, 3) tidal volume, 4) respiration rate, 5) minute ventilation, 6) oxygen intake, and 7) heart rate. The items 1) and 2) were measured by a three-dimensional motion analysis system, and the items 3) through 7) were measured by a respiratory gas analyzer. As for the breathing movement pattern, there were differences among the subjects in terms of the rates of increase in chest expansion and in respiration rate after exercise. The subjects were classified into 4 groups according to these differences. The group, in which respiration rate was increased, showed the marked increase in minute ventilation and oxygen intake, and the rapid recovery of heart rate. The group, in which chest expansion rate was increased, on the other hand, showed small increase in minute ventilation and oxygen intake, and the slow recovery of heart rate. The breathing strategies which are beneficial to energy efficiency exist, however, healthy men do not always select the beneficial strategies.

Effect of sonic driving on maximal aerobic performance

The study purpose was to evaluate antecedent binaural stimulation (ABS) on maximal aerobic physical performance. Twenty-two healthy, physically active subjects, 21-34 years, randomly received one of two preparations for each session: 15 min of quiet (BLANK) or percussive sonic driving at 200+ beats per minute (bpm) using a recorded compact disc (FSS, Mill Valley, CA) with headphones (ABS). Baseline HR, blood pressure (BP), and breathing frequency (f(br)) were obtained. During each condition, HR and f(br) were recorded at 3-min intervals. The graded maximal treadmill testing was administered immediately postpreparation session on separate days, with at least 48 h rest between sessions. There were significant differences in the antecedent period means between the two conditions, ABS (HR: 70.2 +/- 10.7 bpm; f(br): 18.5 +/- 3.3 br min(-1); BP: 134.5/87.9 +/- 13.6/9.2 mm Hg) and BLANK (HR: 64.6 +/- 7.9; f(br): 14.3 +/- 2.9; BP: 126.7/80.3 +/- 12.1/8.6). Differences were noted for each 3-min interval and pre- postantecedent period. The maximal graded exercise test (GXT) results showed that there was a small but significant (P < 0.05), increase in maximal VO(2) in the ABS (49.8 +/- 6.8 ml. kg(-1). min(-1)) vs. BLANK (46.7 +/- 8.7) conditions. Related to that finding was a slight increase (0.5 min) in time to exhaustion (P < 0.05). There were no significant differences in HR or RPE (P > 0.05). There may be a latency to ABS related to entrainment or imagery-enhanced warm-up. Am. J. Hum. Biol. 12:558-565, 2000. Copyright 2000 Wiley-Liss, Inc.

Ventilation and locomotion coupling in varsity male rowers

Ventilation and locomotion coupling (entrainment) has been observed and described in rowers during incremental exercise protocols but not during simulated race conditions. The purpose of this descriptive study was to examine ventilation and locomotion entrainment on a breath-by-breath and stroke-by-stroke basis in varsity male rowers during a maximal 2,000-m ergometer test. Eight of eleven rowers entrained ventilation at integral multiples of stroke rate (1:1, 2:1, or 3:1) for at least 120 consecutive seconds, with a 2:1 entrainment pattern being most common. In all 2:1-entrained subjects, inspiration occurred at catch and finish and expiration occurred during the latter portions of drive and recovery. In entrained and unentrained breaths from all rowers, peak flow rates and tidal volumes varied depending on when the breath was initiated during the stroke cycle. Entrained rowers made use of these differences and breathed in a pattern by which they avoided initiating breaths that resulted in reduced tidal volumes. The present data indicated that ventilation was impaired at stroke finish and not at catch, as hypothesized by some previous researchers. Ventilation also appeared to be subordinate to consistent locomotive patterns under race conditions.

Ventilation and entrainment of breathing during cycling and running in triathletes

PURPOSE

To assess whether entrainment of breathing (E) during exercise: 1) differed according to the test protocol in well-trained triathletes, and 2) improved ventilatory efficiency during exercise.

METHODS

Eight triathletes performed three incremental tests until exhaustion: while cycling (CE), while running at increasing grade and constant speed (increasing GRADE) and while running at increasing speed and constant grade (increasing SPEED), respectively. E was evaluated as the percentage of breaths occurring at respiratory rates (F) corresponding to integer ratios of the exercise cycle rate. To assess whether E improved ventilatory efficiency, deltaVE/VO2 between nonentrained and entrained breaths was measured at each load.

RESULTS

Mean E was higher in CE (57.2+/-21.9%) than in increasing GRADE (46.9+/-18.7%) and increasing SPEED (41.4+/-17.2%). E decreased at high loads in CE and increasing SPEED but not in increasing GRADE. In the group of subjects, E correlated with the degree of fitness (evaluated as VO2Tvent/VO2peak%) only during increasing GRADE. By multiple regression analysis on all data, minute ventilation correlated with CO2 production but not with the exercise cycle rate; however, either F or tidal volume correlated significantly with both these variables. VE/VO2 was lower in entrained than nonentrained breaths at each load in CE and increasing GRADE experiments, but the difference was small.

CONCLUSIONS

In spite of some differences among protocols, triathletes showed significant E during incremental exercise tests. Spontaneous E appeared to slightly improve ventilatory efficiency during CE and increasing GRADE protocols.

Analysis of coordination between breathing and walking rhythms in humans

We investigated the coordination between breathing and walking in humans to elucidate whether the coordination degree depends more on metabolic load or on breathing or stride frequencies and whether coordination causes energetic economization expressed by reduction of oxygen uptake (VO2). Eighteen healthy volunteers walked on a treadmill at three load levels realized by different velocities and slopes. We analyzed the time intervals between step onset and the onset of inspiration or expiration related to stride duration (relative phase, phi) and computed the relative-phase histogram to assess the degree of coordination. The degree of coordination between breathing and stepping enhanced with increasing walking speed. Increased work load achieved by slope at constant walking speed improved coordination only slightly. No significant VO2 reduction due to coordination was found. VO2 was more strongly related to ventilation variations occurring during coordination. Also the sympathetic tone reflected by the spectral power of heart rate variability was not reduced during coordination. We conclude that during walking the coordination degree increases with increasing stride frequency and that coordination does not necessarily cause energetic economization.

Coordination Between Breathing and Finger Tracking in Man

Arm and leg movements are known to produce temporal pattern changes of breathing. This can be interpreted as coordination, as defined by von Holst (1939). The aim of the present study was to find whether breathing exerts an influence in a reverse direction on a nonrespiratory movement as well. A pursuit tracking test was used, and test individuals (N = 19) were instructed to track a visually presented step function by flexion or extension of their right index finger. Velocity and precision of the step responses proved to be dependent on their relation to the breathing time course; the differences between inspiratory and expiratory responses were smaller than those within each half-cycle. The movements were performed more rapidly and more precisely in about the middle of each half-cycle than immediately after the respiratory phase transition or during the second half of each inspiration or expiration. Discontinuous short-lasting motor actions exerted a coordinative influence on respiration comparablewith that of periodical events: Breaths coinciding with step responses were shortened, preferably when the preset step was given early in the inspiration. It was hypothesized that the reciprocal effect between both motor actions changes periodically. In the first part of each respiratory half-cycle, the respiratory rhythm exerts only a weak influence on additional movements, but it can be altered easily by simultaneous motor processes. Toward the respiratory phase-switching, the respiratory rhythm behaves more stably against coordinative influences and becomes capable of impairing an additional movement.

Running training and co-ordination between breathing and running rhythms during aerobic and anaerobic conditions in humans

The study was carried out on ten triathletes, six sprinters and ten subjects not trained in running (controls) to assess the effects of training history on the co-ordination between breathing and running rhythms during running on a treadmill. Three exercise intensities were used: 50%, 80% and 110% of the subject's anaerobic threshold (AT). All three intensities were performed twice: once with spontaneous breathing and once with breathing intentionally co-ordinated to the running rhythm. Heart rate, respiratory parameters and leg movements were continuously recorded. Blood lactate concentrations were measured discontinuously. The degree of co-ordination between running and breathing was quantified as the percentage of inspirations and/or expirations starting during the same phase of step. The results showed that the degree of both spontaneous and intended co-ordination at aerobic exercise intensities was in all three groups the same and increased in all groups with increasing intensity from 50% to 80% of AT; further increase of intensity to 110% of AT was associated with a significant decrease of co-ordination in controls and sprinters, whereas triathletes were able to maintain the same high degree of co-ordination as at 80% of AT. It was concluded that running training of either type at aerobic work loads had no effect on the co-ordination between running and breathing rhythms. At anaerobic intensities, however, the degree of co-ordination between running and breathing rhythms was higher in the endurance trained athletes than in the sprinters or in the untrained subjects. The degree of co-ordination increased with increasing regularity of breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

Entrained breathing and oxygen consumption during treadmill walking

Entrainment of the breathing rhythm to that of the rhythm of limb movement during exercise has been shown to decrease oxygen consumption for cycling at a moderate workload. This study examined the effect of entrainment on oxygen consumption during treadmill walking at two workloads. For each workload, 8 subjects performed two exercise protocols consisting of walking on a treadmill for 8 min. For the first protocol they received no instructions, but for the second protocol they were instructed to coordinate one breath per auditory cue which was provided during the last 4 min of exercise. The auditory cue was transmitted as a click via headphones. It was derived from a foot switch and was designed to synchronize breathing to the walking pace at a respiratory frequency close to that observed in the first protocol. Entrainment and oxygen consumption were compared between the protocols for the last 4-min segments for each workload. These comparisons showed that the presence of the auditory cue significantly increased entrainment from 29 to 74%, but oxygen consumption was not significantly changed.

Effect of cardiac-locomotor coupling on the metabolic efficiency of pedalling

Coupling between cardiac and locomotor rhythms (CLC) has been reported while subjects exercise at cadences that are natural to them. The hypothesis that oxygen consumption (VO2) would be lower when subjects pedalled at the rate producing 1:1 coupling of heart and pedalling rates than when they pedalled at noncoupled rates was tested with 12 men on a cycle ergometer. At a moderate power output based on their VO2max, subjects pedalled at six different pedalling rates while VO2 and heart rate were measured. The pedalling rates were the preferred frequency, frequencies 15 and 30% above and below the preferred frequency, and the 1:1 coupled frequency. In 8 of the 12 subjects it was possible to fit their data with significant regression equations relating VO2 to pedalling rate, but in no subject was the 1:1 coupled state energetically beneficial, suggesting that any functional significance of CLC is unrelated to metabolic efficiency.

Analysis of co-ordination between breathing and exercise rhythms in man

1. The purpose of the present study was to analyse the incidence and type of coordination between breathing rhythm and leg movements during running and to assess the effect of co-ordination on the running efficiency, as well as to compare the results with those found during cycling. 2. The experiments were carried out on thirty-four untrained volunteers exercising at two work loads (60 and 80% of subject's physical work capacity 170) on a treadmill. In addition nineteen of the subjects exercised at the same two work loads on a bicycle ergometer. The subjects were running at both work loads in three different modes in randomized order: with normal arm movements, without arm movements and with breathing paced by an acoustic signal which was triggered by the leg movement. 3. Respiratory variables, oxygen uptake and leg movements were continuously recorded and evaluated on-line. The degree of co-ordination was expressed as a percentage of inspirations and/or expirations starting in the same phase of the step or pedalling cycle. 4. The average degree of co-ordination was higher during running (up to 40%) than during cycling (about 20%) during both work loads. The difference in the degree of co-ordination between running and cycling is probably not due to the lack of arm movements during cycling since the degree of co-ordination during running with and without arm movements was the same. 5. The degree of co-ordination during running increased slightly but not significantly with increasing work load and could be increased significantly by paced breathing. 6. The co-ordination between breathing and running rhythms occurred in three different patterns: (a) breathing was co-ordinated all the time with the same phase of step, (b) co-ordination switched suddenly from one phase of step to another and (c) co-ordination ensued alternatively once on the right and once on the left leg movement. During cycling the pattern described in (a) occurred almost exclusively. 7. During running with a high degree of co-ordination, oxygen uptake for a given work load was slightly but significantly lower than during running with weak co-ordination.

Cardiac-locomotor coupling while finger tapping: Part II. A cross-over control study

Cardiac-locomotor coupling (CLC) has been reported by us while people finger tap at cadences natural to them. Since then, we have developed a simple cross-over control strategy in which the heart rate of one subject is related to the finger-tapping rate of another. Of the 20 normal subjects previously studied while tapping a telegraph key at a comfortable rate for 10 min., reevaluation of their data showed that 9 (45%) and 4 (20%) of them, under test and control conditions, respectively, appeared to couple at a single-digit integer ratio. Neither the incidence nor the intensity of apparent CLC under the two conditions was significantly different. Raster plots of the most tightly related rates gave no evidence of phase locking. These results have two implications. First, previously published reports on CLC (and other entrainment phenomena) should be interpreted with caution, and cross-over controls should be considered in future research. Second, the absence of CLC during finger tapping suggests that CLC may only be functionally significant during exercise of large muscle groups (e.g., by minimization of cardiac afterload) or when impact-loading occurs (e.g., by enhancing cardiac ventricular emptying.