Experiences of carers of youth, adult children and spouses with ME/CFS.

OBJECTIVES: The debilitating nature of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) means that family members often take on a caring role. This study compared the experiences of people caring for three groups: youth, young adults, spouses. METHODS: An opportunistic sample of 36 carers completed an online survey of open-ended questions asking about their experiences. Thematic analysis was used to consider the three sets of responses separately and Thematic Comparison was used to identify points of connection and disconnection across the sets. RESULTS: The themes identified were very similar to those identified in past studies. Two super-ordinate themes were identified: "Lack of knowledge and understanding" and "Holistic Impact". Though most sub-ordinate themes were evident across all three groups, important differences were found. The sub-ordinate themes "Caring Blindly", "Emotional and physical health cost", and "Impact on the whole family" were more evident amongst carers of youth while the theme "Worry for the future" was more evident from carers of young adults and spouses. DISCUSSION: Differences seemed to be related to both the time since diagnosis and the life stage. A longitudinal study would help to understand how carer experiences change over the life course of caring for someone with ME/CFS.

Post-Exertional Malaise May Be Related to Central Blood Pressure, Sympathetic Activity and Mental Fatigue in Chronic Fatigue Syndrome Patients.

Post-exertional malaise (PEM) is regarded as the hallmark symptom in chronic fatigue syndrome (CFS). The aim of the current study is to explore differences in CFS patients with and without PEM in indicators of aortic stiffness, autonomic nervous system function, and severity of fatigue. One-hundred and one patients met the Fukuda criteria. A Chronic Fatigue Questionnaire (CFQ) and Fatigue Impact Scale (FIS) were used to assess the level of mental and physical fatigue. Aortic systolic blood pressure (sBPaortic) and the autonomic nervous system were measured with the arteriograph and Task Force Monitor, respectively. Eighty-two patients suffered prolonged PEM according to the Fukuda criteria, while 19 did not. Patients with PEM had higher FIS scores (p = 0.02), lower central systolic blood pressure (p = 0.02) and higher mental fatigue (p = 0.03). For a one-point increase in the mental fatigue component of the CFQ scale, the risk of PEM increases by 34%. For an sBPaortic increase of 1 mmHg, the risk of PEM decreases by 5%. For a one unit increase in sympathovagal balance, the risk of PEM increases by 330%. Higher mental fatigue and sympathetic activity in rest are related to an increased risk of PEM, while higher central systolic blood pressure is related to a reduced risk of PEM. However, none of the between group differences were significant after FDR correction, and therefore conclusions should be treated with caution and replicated in further studies.

Evidence-Based Aerobic Exercise Training in Metabolic-Associated Fatty Liver Disease: Systematic Review with Meta-Analysis.

BACKGROUND: This meta-analysis evaluates the overall effect of the non-pharmacological intervention, aerobic exercise, upon serum liver enzymes levels, glucose metabolism and anthropometric measures amongst patients with metabolic associated fatty liver disease (MAFLD). It also examines whether the effects on these outcomes are moderated by the aerobic training protocol when considered according to the American College of Sports Medicine (ACSM) recommended FITT (frequency, intensity, time, type) principles. Approach and Results: Fifteen randomized control trials were included in the meta-analysis. Compared with usual care, continuous and interval training showed significant efficacy in alanine aminotransferase (ALT) level improvement (MD = -2.4, 95% CI: -4.34 to -0.46 p = 0.015, I2 = 9.1%). Interventions based on all types of aerobic exercise protocols showed significant improvement of intrahepatic triglycerides (MD = -4.0557, 95% CI: -5.3711 to -2.7403, p < 0.0001, I2 = 0%) and BMI (MD = -0.9774, 95% CI: -1.4086 to -0.5462, p < 0.0001, I2 = 0). Meta-regression analysis demonstrated a significant correlation between total intervention time and ALT level (for all aerobic protocols: 6.0056, se = 2.6896, z = 2.2329, p = 0.02; as well as for continuous and interval aerobic protocols: 5.5069, se = 2.7315, z = 2.016, p = 0.04). CONCLUSIONS: All types of aerobic exercise protocols are effective at improving intrahepatic triglycerides and lead to a reduction in body mass index. In addition, continuous and interval aerobic exercise may be more effective at improving ALT ≤12 weeks intervention time benefits the management of MAFLD.

Relationship between Cardiopulmonary, Mitochondrial and Autonomic Nervous System Function Improvement after an Individualised Activity Programme upon Chronic Fatigue Syndrome Patients.

BACKGROUND: The therapeutic effects of exercise from structured activity programmes have recently been questioned; as a result, this study examines the impact of an Individualised Activity Program (IAP) on the relationship with cardiovascular, mitochondrial and fatigue parameters. METHODS: Chronic fatigue syndrome (CFS) patients were assessed using Chalder Fatigue Questionnaire (CFQ), Fatigue Severity Score (FSS) and the Fatigue Impact Scale (FIS). VO2peak, VO2submax and heart rate (HR) were assessed using cardiopulmonary exercise testing. Mfn1 and Mfn2 levels in plasma were assessed. A Task Force Monitor was used to assess ANS functioning in supine rest and in response to the Head-Up Tilt Test (HUTT). RESULTS: Thirty-four patients completed 16 weeks of the IAP. The CFQ, FSS and FIS scores decreased significantly along with a significant increase in Mfn1 and Mfn2 levels (p = 0.002 and p = 0.00005, respectively). The relationships between VO2 peak and Mfn1 increase in response to IAP (p = 0.03) and between VO2 at anaerobic threshold and ANS response to the HUTT (p = 0.03) were noted. CONCLUSIONS: It is concluded that IAP reduces fatigue and improves functional performance along with changes in autonomic and mitochondrial function. However, caution must be applied as exercise was not well tolerated by 51% of patients.

Effects of Post-Exertional Malaise on Markers of Arterial Stiffness in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Background: Evidence is emerging that individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) may suffer from chronic vascular dysfunction as a result of illness-related oxidative stress and vascular inflammation. The study aimed to examine the impact of maximal-intensity aerobic exercise on vascular function 48 and 72 h into recovery. Methods: ME/CFS (n = 11) with gender and age-matched controls (n = 11) were randomly assigned to either a 48 h or 72 h protocol. Each participant had measures of brachial blood pressure, augmentation index (AIx75, standardized to 75 bpm) and carotid-radial pulse wave velocity (crPWV) taken. This was followed by a maximal incremental cycle exercise test. Resting measures were repeated 48 or 72 h later (depending on group allocation). Results: No significant differences were found when ME/CFS were directly compared to controls at baseline. During recovery, the 48 h control group experienced a significant 7.2% reduction in AIx75 from baseline measures (p < 0.05), while the matched ME/CFS experienced no change in AIx75. The 72 h ME/CFS group experienced a non-significant increase of 1.4% from baseline measures. The 48 h and 72 h ME/CFS groups both experienced non-significant improvements in crPWV (0.56 ms-1 and 1.55 ms-1, respectively). Conclusions: The findings suggest that those with ME/CFS may not experience exercise-induced vasodilation due to chronic vascular damage, which may be a contributor to the onset of post-exertional malaise (PEM).

Elevated peak systolic blood pressure in endurance-trained athletes: Physiology or pathology?

Blood pressure is a function of cardiac output and peripheral vascular resistance. During graded exercise testing (GXT), systolic blood pressure (SBP) is expected to increase gradually along with work rate, oxygen consumption, heart rate, and cardiac output. Individuals exposed to chronic endurance training attain a greater exercise SBP than in their untrained state and sedentary counterparts, but it is currently unknown what is considered a safe upper limit. This review discusses key studies examining blood pressure response in sedentary individuals and athletes. We highlight the physiological characteristics of highly fit individuals in terms of cardiovascular physiology and exercise blood pressure and review the state of the current literature regarding the safety of high SBP during exercise in this particular subgroup. Findings from this review indicate that a consensus on what is a normal SBP response to exercise in highly fit subjects and direct causation linking high GXT SBP to pathology is lacking. Consequently, applying GXT SBP guidelines developed for a "normal" population to endurance-trained individuals appears unsupported at this time. Lack of evidence for poor outcomes leads us to infer that elevated peak SBP in this subgroup could more likely reflect an adaptive response to training, rather than a pathological outcome. Future studies should track clinical outcomes of those achieving elevated SBP and develop athlete-specific guidelines.

Prediction of Discontinuation of Structured Exercise Programme in Chronic Fatigue Syndrome Patients.

PURPOSE: The purpose of this study was to assess differences in the physiological profiles of completers vs. non-completers following a structured exercise programme (SEP) and the ability to predict non-completers, which is currently unknown in this group. METHODS: Sixty-nine patients met the Fukuda criteria. Patients completed baseline measures assessing fatigue, autonomic nervous system (ANS), cognitive, and cardiovascular function. Thirty-four patients completed a home-based SEP consisting of 10-40 min per day at between 30 and 80% actual HR max. Exercise intensity and time was increased gradually across the 16 weeks and baseline measures were repeated following the SEP. RESULTS: Thirty-five patients discontinued, while 34 completed SEP. For every increase in sympathetic drive for blood pressure control as measured by the taskforce, completion of SEP decreased by a multiple of 0.1. For a 1 millisecond increase in reaction time for the simple reaction time (SRT), the probability for completion of SEP also decreases by a multiple of 0.01. For a one beat HRmax increase, there is a 4% increase in the odds of completing SEP. CONCLUSION: The more sympathetic drive in the control of blood vessels, the longer the reaction time on simple visual stimuli and the lower the HRmax during physical exercise, then the lower the chance of SEP completion in ME/CFS.

Male Sexual Function in New Zealand: A Population-Based Cross-Sectional Survey of the Prevalence of Erectile Dysfunction in Men Aged 40-70 Years.

BACKGROUND: Sexual function declines with age and erectile dysfunction (ED) is a common condition worldwide; however, prevalence rates vary markedly between populations and reliable data specific to New Zealand (NZ) are lacking. AIM: To assess the prevalence of ED in NZ men using a population-based cross-sectional survey. METHODS: Postal questionnaires were sent, according to a modified Dillman method, to a randomly selected age-stratified population-based sample of 2,000 men 40 to 70 years old obtained from the electoral roll. Self-reported erectile function was assessed using the five-item International Index of Erectile Function (IIEF-5) and the single-question self-assessment tool. OUTCOMES: The prevalence of ED is presented as crude, age-adjusted to the distribution of the NZ population, and standardized to the World Health Organization World Standard Population (WSP). Associations between sexual function and age were analyzed using χ2 test. RESULTS: The response rate was 30% (599) and 28% (562) were complete for analysis. The crude prevalence of ED was 42% (22% mild, 10% mild to moderate, 6% moderate, and 4% severe), the age-adjusted prevalence was 38%, and the WSP-adjusted prevalence was 37%. Among men reporting ED, 16% were medically diagnosed and 22% were treated. ED affected 24% of men in their 40s, 38% in their 50s, and 60% in their 60s (P < .001). Age was associated with a significant increase in diagnosed ED (P = .001), treated ED (P = .006), dissatisfaction with current sexual function (P < .001), associated anxiety or depression (P = .023), and a decrease in sexual activity (P < .001). CLINICAL TRANSLATION: Approximately one in three NZ men 40 to 70 years old might have ED. Although comparable to overseas populations, this prevalence is high. STRENGTHS AND LIMITATIONS: This study provides the most reliable, comprehensive, and current information on ED and its risk factors in NZ men. Strengths include the large sample, the use of random selection from a population-based sampling frame, established effective survey methods, and the validated IIEF-5. Limitations include the inability of cross-sectional data to determine causation, non-sampling errors associated with the population-based sampling frame, the low response rate, the inability to assess non-respondents, the possibility of men with ED who were sexually inactive not responding or not completing the IIEF-5, and the inherent inability to rule out recall bias. CONCLUSION: ED is a marker of subclinical cardiovascular disease. The high prevalence and low levels of diagnosis and treatment indicate a lost opportunity for timely intervention to delay or prevent the progression toward clinical disease. Quilter M, Hodges L, von Hurst P, et al. Male Sexual Function in New Zealand: A Population-Based Cross-Sectional Survey of the Prevalence of Erectile Dysfunction in Men Aged 40-70 Years. J Sex Med 2017;14:928-936.

Does short-term whole-body vibration training affect arterial stiffness in chronic stroke? A preliminary study.

[Purpose] Previous studies have shown that stroke is associated with increased arterial stiffness that can be diminished by a program of physical activity. A novel exercise intervention, whole-body vibration (WBV), is reported to significantly improve arterial stiffness in healthy men and older sedentary adults. However, little is known about its efficacy in reducing arterial stiffness in chronic stroke. [Subjects and Methods] Six participants with chronic stroke were randomly assigned to 4 weeks of WBV training or control followed by cross-over after a 2-week washout period. WBV intervention consisted of 3 sessions of 5 min intermittent WBV per week for 4 weeks. Arterial stiffness (carotid arterial stiffness, pulse wave velocity [PWV], pulse and wave analysis [PWA]) were measured before/after each intervention. [Results] No significant improvements were reported with respect to carotid arterial stiffness, PWV, and PWA between WBV and control. However, carotid arterial stiffness showed a decrease over time following WBV compared to control, but this was not significant. [Conclusion] Three days/week for 4 weeks of WBV seems too short to elicit appropriate changes in arterial stiffness in chronic stroke. However, no adverse effects were reported, indicating that WBV is a safe and acceptable exercise modality for people with chronic stroke.

Human temperature regulation when given the opportunity to behave.

This study aimed to test the primary hypotheses that human thermoregulatory behavior is: (1) initiated before changes in rectal or esophageal temperatures; and (2) accompanied by indiscernible differences in sweating or shivering. This was achieved by placing nine, healthy, males in a situation where they were free to move between a cold (~8 °C) and a hot (~46 °C) environment. Upon behaving [i.e., move from cold to hot (C→H) or from hot to cold (H→C)], skin, rectal, and esophageal temperatures, indices of cutaneous vasomotor tone, metabolism and evaporation, and local and whole-body thermal discomfort were recorded. Rectal temperatures were similar at H→C (37.1 ± 0.2 °C) and C→H (37.1 ± 0.2 °C); yet esophageal temperatures were higher at C→H (36.9 ± 0.2 vs. 36.8 ± 0.2 °C). Skin temperature (C→H, 28.4 ± 0.9 vs. H→C, 35.0 ± 0.6 °C) and vasomotor tone were drastically different upon the decision to behave. Metabolic heat production was lower at H→C (79 ± 10 W/m(2)) than at C→H (101 ± 20 W/m(2)), yet there were no statistical differences in evaporative heat loss (C→H, 23 ± 33 W/m(2) vs. H→C, 52 ± 36 W/m(2)). Whole-body thermal discomfort was similar at C→H and H→C, yet there were inter-segmental differences. These findings indicate that skin temperature, not core temperature, plays a signaling role in the decision to behaviorally thermoregulate. However, this behavior does not occur in the complete absence of autonomic thermoregulatory responses.

Comparison study of treadmill versus arm ergometry.

The Bruce treadmill test is used worldwide to assess cardiovascular disease. However, because of the high increments of intensity between the stages of this test, it is not best suited to a number of populations. Therefore, the aim of the study was to determine the difference between physiological outcomes of the arm crank test and Bruce treadmill test and to provide a regression equation to account for this. Thirty subjects (16 men and 14 women) performed both an arm crank test and the Bruce treadmill test, on two separate days, in a random order. Peak values of oxygen uptake (VO(2) ), respiratory exchange ratio (RER), ventilation rate (V(E) ), heart rate (HR) and ratings of perceived exertion (RPE) were recorded. Arm crank VO(2peak) and peak V(E) were significantly lower compared with treadmill VO(2peak) and peak VE, in both men and women (P<0·001). Arm crank HR(peak) was significantly lower than treadmill HR(peak) in men (P<0·001). The following is the regression equation to estimate treadmill: VO(2peak) = 0·8*arm crank VO(2peak) + 0·019*body weight + 2·025*gender-0·038*gender*body weight + 0·852, with gender being '0' for males and '1' for females. This model has a r(2) of 0·832 (SEE = 0·471). This strong correlation indicates that an accurate prediction of treadmill VO(2peak) can be made by arm crank VO(2peak) , which is a good estimate of a person's maximal oxygen uptake (VO(2max) ). Therefore, the arm crank test can be of great importance for evaluation of cardiovascular disease in many people.

Peak cardiac power output in healthy, trained men.

Previous investigations into peak cardiac power output (CPO peak) have been limited to clinical populations and healthy, but non-athletic adults, and normative data on trained individuals would allow a greater understanding of this parameter. Therefore, we recruited eight healthy, well-trained male cyclists. Peak oxygen consumption ((.)VO2 peak) was assessed using an incremental ergometer test, and following a 40-min recovery period, peak cardiac output ((.)QT peak) was measured during a constant load test that elicited (.)VO2 peak (±5%) using the Defares CO2 rebreathing technique. CPO peak was calculated as described by Cooke et al. (1998). Mean (±SD) values during the constant load test were: (.)VO2 peak, 4.94 ± 0.41 l min⁻¹; (.)QT peak, 36.5 ± 3.7 l min⁻¹; mean arterial pressure, 123 ± 8 mmHg and CPO peak, 9.9 ± 1.0 W. These results demonstrate CPO peak in a well-trained population to be approximately twice those observed in healthy, but non-athletic adults. The current data provide useful information regarding the upper limits and possible 'trainability' of cardiac pumping capacity for sedentary and clinically compromised individuals.

Validity and reliability of short-term heart-rate variability from the Polar S810.

PURPOSE: : To assess the validity and the reliability of short-term resting heart-rate variability (HRV) measures obtained using the Polar S810 heart-rate monitor and accompanying software. METHODS: : Measures of HRV were obtained from 5-min R to R wave (RR) interval data for 19 males and 14 females during 10 min of quiet rest on three separate occasions at 1-wk intervals using the Polar S810. Criterion measures of HRV were obtained simultaneously using the CardioPerfect (CP; Medical Graphics Corporation, St Paul, MN) 12-lead ECG module. Measures of validity of the Polar S810 were estimated by regression analysis, and measures of reliability of both devices were estimated by analysis of change scores. Measures of the SD of normal-to-normal intervals (SDNN), the root mean square of successive differences (RMSSD), and the low-frequency (LF) and the high-frequency (HF) spectral power and their ratio (LF/HF) were analyzed after log transformation, whereas mean RR and LF and HF in normalized units were analyzed without transformation. RESULTS: : There were marginal differences between the Polar and the CP mean measures of HRV, and the uncertainty in the differences was small. The Polar S810 demonstrated high correlations (0.85-0.99) with CP for all measures of HRV indicating good to near-perfect validity. Except for the low- and the high-frequency normalized units, Polar S810 did not add any substantial technical error to the within-subject variability in the repeated measurements of HRV. CONCLUSION: : HRV measures obtained with the Polar S810 and accompanying software have no appreciable bias or additional random error in comparison with criterion measures, but the measures are inherently unreliable over a 1-wk interval. Reliability of HRV from longer (e.g., 10 min) and/or consecutive 5-min RR recordings needs to be investigated with the Polar and criterion instruments.

Levels of agreement for RR intervals and short-term heart rate variability obtained from the Polar S810 and an alternative system.

The aim of this study was to assess the agreement between HRV measures derived from a time series of RR intervals recorded by a standard 12-lead ECG (CP) and a commercially available RR interval recorder (S810). Thirty-three participants (19 males) (median age 36, range 20-63) underwent simultaneous, 5-min, supine RR-interval recordings. Each RR interval time series was analysed using the software supplied with the recording equipment. Two comparisons were then made. First, a comparison of RR interval data recording and editing only was made. Second, comparisons were made for measures of HRV derived from edited RR interval data. Agreement between RR intervals and standard HRV measures were assessed using intraclass correlation coefficient and limits of agreement. Agreement of HRV measures derived from RR intervals recorded and edited by individual systems was not acceptable. Agreement analyses for the number of RR intervals recorded and edited by each systems software showed excellent intraclass correlation coefficients (ICC lower 95% CI > 0.75) and acceptably narrow limits of agreement (LoA). These data indicate that the number of RR intervals recorded by S810 can agree well those recorded from a standard 12-lead ECG. This is true even after application of system specific data editing procedures. Commercial RR-interval recorders may offer a simple, inexpensive alternative to full 12-lead ECG in the recording and editing of RR intervals for subsequent HRV analysis in healthy populations.

Comparison of cardiac output determined by different rebreathing methods at rest and at peak exercise.

Several rebreathing methods are available for cardiac output (Q (T)) measurement. The aims of this study were threefold: first, to compare values for resting Q (T) produced by the equilibrium-CO(2), exponential-CO(2) and inert gas-N(2)O rebreathing methods and, second, to evaluate the reproducibility of these three methods at rest. The third aim was to assess the agreement between estimates of peak exercise Q (T) derived from the exponential and inert gas rebreathing methods. A total of 18 healthy subjects visited the exercise laboratory on different days. Repeated measures of Q (T), measured in a seated position, were separated by a 5 min rest period. Twelve participants performed an incremental exercise test to determine peak oxygen consumption. Two more exercise tests were used to measure Q (T) at peak exercise using the exponential and inert gas rebreathing methods. The exponential method produced significantly higher estimates at rest (averaging 10.9 l min(-1)) compared with the equilibrium method (averaging 6.6 l min(-1)) and the inert gas rebreathing method (averaging 5.1 l min(-1); P < 0.01). All methods were highly reproducible with the exponential method having the largest coefficient of variation (5.3%). At peak exercise, there were non-significant differences between the exponential and inert gas rebreathing methods (P = 0.14). The limits of agreement were -0.49 to 0.79 l min(-1). Due to the ability to evaluate the degree of gas mixing and to estimate intra-pulmonary shunt, we believe that the inert gas rebreathing method has the potential to measure Q (T) more precisely than either of the CO(2) rebreathing methods used in this study. At peak exercise, the exponential and inert gas rebreathing methods both showed acceptable limits of agreement.

Lack of agreement between gas exchange variables measured by two metabolic systems.

The purpose of this study was to assess the agreement and consistency between gas exchange variables measured by two online metabolic systems during an incremental exercise test. After obtaining local ethics approval and informed consent, 15 healthy subjects performed an incremental exercise test to volitional fatigue using the Bruce protocol. The Innocor (Innovision, Denmark) and CardiO2 (Medical Graphics, USA) systems were placed in series, with the Innocor mouthpiece attached to the pneumotach of the CardiO2. Metabolic data were analysed during the last 30 seconds of each stage and at peak exercise. There were non- significant differences (p > 0.05) between the two systems in estimation of oxygen consumption (VO2) and in minute ventilation (VE). Mean Cronbach's alpha for VO2 and VE were 0.88 and 0.92. The Bland-Altman analysis revealed that limits of agreement were -0.52 to 0.55 l.min(-1) for VO2, and -8.74 to 10.66 l.min(-1) for VE. Carbon dioxide production (VCO2) and consequently respiratory exchange ratio (RER) measured by the Innocor were significantly lower (p < 0.05) through all stages. The CardiO2 measured fraction of expired carbon dioxide (FeCO2) significantly higher (p < 0.05). The limits of agreement for VO2 and VE are wide and unacceptable in cardio-pulmonary exercise testing. The Innocor reported VCO2 systematically lower. Therefore the Innocor and CardiO2 metabolic systems cannot be used interchangeably without affecting the diagnosis of an individual patient. Results from the present study support previous suggestion that considerable care is needed when comparing metabolic data obtained from different automated metabolic systems. Key pointsThere is general concern regarding the limited knowledge available about the accuracy of a number of commercially available systems.Demonstrated limits of agreement between key gas exchange variables (oxygen consumption and minute ventilation) as measured by the two metabolic systems were wide and unacceptable in cardio-pulmonary exercise testing.Considerable care is needed when comparing metabolic data obtained from different automated metabolic systems.

The impact of short term supervised and home-based walking programmes on heart rate variability in patients with peripheral arterial disease.

The aims of the study were to determine whether heart rate variability (HRV) measured at rest and during exercise could be altered by an exercise training programme designed to increase walking performance in patients with peripheral arterial disease. Forty-four volunteers were randomised into 12 weeks of either: supervised walking training twice weekly for 30 min at 75% VO2peak (SU), home-based walking training sessions: twice weekly, 30 min per week (HB) or no exercise (CT). HRV measures were calculated from a 5-min resting ECG. Each patient then underwent maximal, graded exercise treadmill testing. All measures were repeated after 12 weeks. The SU group showed significantly (p < 0.001) increased maximal walking time (MWT) but no change in VO2peak. There were no statistically significant changes in any of the measures of HRV in any group. Effect sizes for change in HRV measures were all very small and in some cases negative. Improved walking performance was not accompanied by central cardiorespiratory or neuroregulatory adaptations in the present study. The lack of any change in HRV was possibly due to either the low intensity or discontinuous nature of exercise undertaken. Key pointsIt is known that exercise can positively influence heart rate variability in some cardiac patients.It is known that exercise can increase walking performance in peripheral vascular disease patients.Exercise training improved walking performance in peripheral vascular disease patients but HRV was unaltered.This may be due to low overall physiological demands on the cardiovascular system or the intermittent nature of the exercise.

Physiological range of peak cardiac power output in healthy adults.

AIMS: The purpose of this study was to indicate the normal range for peak cardiac power output (CPO(peak)) in healthy adults and to explore age- and sex-related variations of this parameter. METHODS AND RESULTS: Using the non-invasive exponential CO(2) rebreathing technique [J.G. Defares, J Appl Physiol13 (1958) 159], cardiac output was measured at an exercise intensity determined to coincide with > or =95% of peak oxygen consumption in 102 healthy adults (mean +/- SD, age 43 +/- 13 years, body mass 74 +/- 13 kg). Peak cardiac power was then computed from measurements of peak cardiac output (Q(Tpeak)) and peak mean arterial pressure (MAP(peak)) using the equation described by Cooke et al. [Heart79 (1998) 289]. Peak oxygen consumption in the study population was 2.42 (+/-0.74) l min(-1) and subjects achieved 101 +/- 7% of this value during the measurement of . was 17.3 (+/-4) l min(-1), and CPO(peak) was computed as 4.5 (+/-1.2) W. CPO(peak) ranged from 3.11 to 7.94 W in men and 2.53 to 5.57 W in women. Additionally, ageing appears to be associated with a significant loss of peak cardiac power in men that is not apparent in women. CONCLUSION: Although the sample size remains moderate, the CPO values attained were normally distributed and these values provide a useful indication of the normal range for CPO(peak) in healthy adults.