Age-predicted Maximum Heart Rate Research Articles

Comparisons of Age-Predicted Maximum Heart Rate Equations in College-Aged Subjects

This study investigated the accuracy of age-predicted equations to predict heart rate maximum (HRmax) in a college-age sample and establish efficacy of short-duration anaerobic capacity tests to determine the actual HRmax. A criterion HRmax (CHRmax) was obtained from 96 (52 men and 44 women, age = 22.0 ± 2.8 years, height = 163.9 ± 9.5 cm, 70.6 ± 14.7 kg, resting HR = 68.9 ± 11.2 b·min) healthy volunteers during 2 200-m sprint trials on a standard track. Maximal effort was confirmed via plasma lactate ≥7 mmol·L(-1) and rating of perceived exertion ≥17 points. The CHRmax was compared to 7 age-predicted HRmax equations: Fox et al., 3 equations from Gellish et al., Tanaka et al., and gender-specific equations from Fairbarn et al., and Hossack et al. Descriptive statistics and standard errors of estimate (SEEs) were calculated. One-way analysis of variance was used to assess differences between the criterion HRmax and the age-predicted HRmax from the 7 equations. The predicted HRmax from the Fox equation and those of Gellish(3), Tanaka, and Hossack were all significantly higher (p ≤ 0.05) than the CHRmax. The Fox equation resulted in overpredicting HRmax in 88.5% of the cases compared to the CHRmax. Compared to the CHRmax, the age-predicted HRmax equations resulted in the following percentages of the CHRmax: Fox = 104.8%, SEE = 12.7; Gellish(1) = 95.2%, SEE = 12.2; Gellish(2) = 99.6%, SEE = 8.3; Gellish(3) = 101.8%, SEE = 9.1; Tanaka = 102.0%, SEE = 9.3; Fairbarn = 100.1%, SEE = 8.5; and Hossack = 105.2%, SEE = 13.9 of CHRmax. It was concluded that the Gellish(2) and Fairbarn equations were the most accurate of the age-predicted HRmax equations in a college-age population. In practical application, 2 200-m sprint trials provide a reasonable estimate of HRmax compared to a graded exercise test.

MR‐compatible treadmill for exercise stress cardiac magnetic resonance imaging

This article describes an MR-safe treadmill that enables cardiovascular exercise stress testing adjacent to the MRI system, facilitating cardiac MR imaging immediately following exercise stress. The treadmill was constructed of nonferromagnetic components utilizing a hydraulic power system. Computer control ensured precise execution of the standard Bruce treadmill protocol commonly used for cardiovascular exercise stress testing. The treadmill demonstrated no evidence of ferromagnetic attraction and did not affect image quality. Treadmill performance met design specifications both inside and outside the MRI environment. Ten healthy volunteers performed the Bruce protocol with the treadmill positioned adjacent to the MRI table. Upon reaching peak stress (98 ± 8% of age-predicted maximum heart rate), the subjects lay down directly on the MRI table, a cardiac array coil was placed, an intravenous line connected, and stress cine and perfusion imaging performed. Cine imaging commenced on average within 24 ± 4 s and was completed within 40 ± 7 s of the end of exercise. Subject heart rates were 86 ± 9% of age-predicted maximum heart rate at the start of imaging and 81 ± 9% of age-predicted maximum heart rate upon completion of cine imaging. The MRI-compatible treadmill was shown to operate safely and effectively in the MRI environment.

Prospective Evaluation of a 12-Week Walking Exercise Program and Its Effect on Fatigue in Prostate Cancer Patients Undergoing Radical External Beam Radiotherapy

To evaluate tolerability and compliance to a walking exercise program and its effect on fatigue during and after radical external beam radiation therapy (EBRT) for prostate cancer. A total of 50 subjects with prostate cancer undergoing EBRT over 6 to 8 weeks were prospectively accrued to an exercise intervention group, matched for age and clinical characteristics to 30 subjects in a historical control group who underwent EBRT with no specific exercise intervention. Starting 1 week before EBRT, exercise participants performed moderate-intensity walking targeting 60% to 70% age-predicted maximum heart rate, at least 20 min/d, 3 d/wk over 12 weeks. The Brief Fatigue Inventory was administered at baseline, mid-EBRT (week 3-4), end-EBRT (week 6-8), and 6 months post-EBRT. Of 50, 42 (84%) of exercise participants completed the walking program. There were no cardiovascular complications, musculoskeletal injuries, or other adverse events. A total of 89% subjects reported "Good-Excellent" satisfaction during and up to 6 months post-EBRT. Fatigue in control subjects escalated from baseline to end-EBRT, remaining high at 6 months post-EBRT (P[r] = 0.03). In contrast, mean total fatigue scores in exercise subjects were stable from baseline up to 6 months post-EBRT (P = 0.52). Trends for higher fatigue interference with quality of life were observed in the control group as compared with the exercise group. Moderate-intensity walking exercise during radical EBRT is safe and feasible. The high convenience and satisfaction ratings, in conjunction with the observed fatigue trends, indicate that this activity has the potential to attenuate fatigue and improve quality of life for patients with localized prostate cancer undergoing curative therapy.

Gene expression alterations at baseline and following moderate exercise in patients with Chronic Fatigue Syndrome and Fibromyalgia Syndrome

To determine mRNA expression differences in genes involved in signalling and modulating sensory fatigue, and muscle pain in patients with chronic fatigue syndrome (CFS) and fibromyalgia syndrome (FM) at baseline, and following moderate exercise. Forty-eight patients with CFS only, or CFS with comorbid FM, 18 patients with FM that did not meet criteria for CFS, and 49 healthy controls underwent moderate exercise (25 min at 70% maximum age-predicted heart rate). Visual-analogue measures of fatigue and pain were taken before, during and after exercise. Blood samples were taken before and 0.5, 8, 24 and 48 h after exercise. Leucocytes were immediately isolated from blood, number coded for blind processing and analyses and flash frozen. Using real-time, quantitative PCR, the amount of mRNA for 13 genes (relative to control genes) involved in sensory, adrenergic and immune functions was compared between groups at baseline and following exercise. Changes in amounts of mRNA were correlated with behavioural measures and functional clinical assessments. No gene expression changes occurred following exercise in controls. In 71% of patients with CFS, moderate exercise increased most sensory and adrenergic receptor's and one cytokine gene's transcription for 48 h. These postexercise increases correlated with behavioural measures of fatigue and pain. In contrast, for the other 29% of patients with CFS, adrenergic α-2A receptor's transcription was decreased at all time-points after exercise; other genes were not altered. History of orthostatic intolerance was significantly more common in the α-2A decrease subgroup. FM-only patients showed no postexercise alterations in gene expression, but their pre-exercise baseline mRNA for two sensory ion channels and one cytokine were significantly higher than controls. At least two subgroups of patients with CFS can be identified by gene expression changes following exercise. The larger subgroup showed increases in mRNA for sensory and adrenergic receptors and a cytokine. The smaller subgroup contained most of the patients with CFS with orthostatic intolerance, showed no postexercise increases in any gene and was defined by decreases in mRNA for α-2A. FM-only patients can be identified by baseline increases in three genes. Postexercise increases for four genes meet published criteria as an objective biomarker for CFS and could be useful in guiding treatment selection for different subgroups.

Chronotropic Responses to Exercise in Heart Transplant Recipients

Partial normalization of the heart rate (HR) response can take place some time after heart transplantation (HTx), but the extent to which this occurs, its time course, and functional significance remain unclear. Seventy-seven heart transplantation patients underwent an exercise test at approximately 1, 6, and 12 mos after heart transplantation, consisting of a resting period, a submaximal exercise test, and a maximal exercise test with stair climbing, followed by a recovery period. An HR monitor was used for continuous surveillance of HR. During the follow-up, HR at rest did not change, whereas all other HR parameters obtained during and after exercise improved, demonstrating a more rapid increase, a higher peak, and a more rapid decline in HR after stopping exercise. Age-predicted maximum HR at baseline was 73% ± 9%, improving to 83% ± 10% at 6 mos (P < 0.001) and to 90% ± 10% at 12 mos (P < 0.001), whereas the Chronotropic Response Index at baseline was 0.49 ± 0.15, improving to 0.67 ± 0.17 at 6 mos (P < 0.001) and to 0.81 ± 0.23 at 12 mos (P < 0.001). Partial normalization of HR was achieved by 71% of heart transplantation patients at 12 mos, with significant changes occurring within 6 mos in most subjects. These findings should contribute to reducing the exercise restrictions that apply to the denervated heart.

NHANES: No significant link between cardiorespiratory fitness and tinnitus

NHANES: No significant link between cardiorespiratory fitness and tinnitus

Rate responsive pacing using cardiac resynchronization therapy in patients with chronotropic incompetence and chronic heart failure

Chronotropic incompetence (CI) is a common finding in patients with advanced chronic heart failure (CHF) and is associated with a worse functional capacity. Whether rate responsive pacing with cardiac resynchronization therapy (CRT) would acutely improve exercise performance in patients with advanced CHF and severe CI (<70% age-predicted maximum heart rate) is unknown. Patients (n = 13) with CHF, a CRT device, and severe CI were randomized in a double-blind crossover pilot study to either DDD (control) or DDDR (rate responsive) pacing. Six minutes walk test (6MWT) distance, oxygen consumption at anaerobic threshold (VO(2) @ AT), and maximal oxygen consumption (VO(2) max) were measured. One week later, testing was repeated in the alternate pacing mode. Rate responsive pacing commenced with standard settings in only 9 of 13 (69%) patients. In these 9 subjects, 6MWT distance improved acutely from 358.5 ± 40.7 to 376.8 ± 24.5 m with DDDR pacing (P< 0.05). VO(2) max did not improve with DDDR pacing (14.0 ± 3.2 mL/kg/min) compared with DDD pacing (13.9 ± 3.0 mL/kg/min; P= 0.69). VO(2) @ AT tended towards improvement with DDDR pacing (10.8 ± 2.9 mL/kg/min) compared with DDD pacing (9.6 ± 1.8 mL/kg/min; P= 0.29). There was a linear relationship between the increase in heart rate at minute 3 during rate responsive pacing and improvement in VO(2) @ AT (r = 0.83, P< 0.05). When rate responsive pacing using a CRT device is achieved in patients with advanced CHF and severe CI, parameters of aerobic exercise performance improve acutely. Routine exercise testing to ensure successful restoration of heart rate response may be beneficial to optimize CRT settings in this patient population.

Test Retest Reliability and Minimal Detectable Change of a Novel Submaximal Graded Exercise Test in the Measurement of Graded Exercise Test Duration

Measurement of graded exercise test duration is clinically important and can be assessed by maximal graded exercise testing. Yet, limitations of maximal graded exercise testing exist. An alternative to maximal graded exercise testing is submaximal graded exercise testing. However, no studies have investigated the reliability of a submaximal graded exercise test in the measurement of graded exercise test duration. The purpose of this study was to determine the test-retest reliability and minimal detectable change (MDC) of a novel submaximal graded exercise test in the measurement of graded exercise test duration. Fifteen people (4 men, 11 women) with a mean age of 26.20 years (SD = 9.04) participated in this study. A novel submaximal graded exercise test was used to measure graded exercise test duration for each participant. Endpoints of the test were either 85% of age-predicted maximum heart rate or voluntarily stopping the test, whichever endpoint occurred first. Heart rate and graded exercise test duration were constantly measured throughout the test. Graded exercise test duration was defined as the total duration (minutes) of the test. For all participants, the submaximal graded exercise test was conducted at baseline and 48-72 hours thereafter. The intraclass correlation coefficient for the test-retest reliability of the test in determining graded exercise test duration was 0.94 (95% CI = 0.83-0.98). The MDC of the test in the measurement of graded exercise test duration was 0.86 minutes. The results suggest that clinicians can use this novel submaximal graded exercise test to reliably measure graded exercise test duration with a measurement error, as expressed by the MDC, of 0.86 minutes.

Ideal Cardiovascular Health Assessments and All-cause and Cardiovascular Disease Mortality

The American Heart Association (AHA)'s National Goals are based on the novel term Ideal Cardiovascular Health, a measurable construct more positive than just the absence of clinical disease. PURPOSE: We examined the effect of the simultaneous presence of 7 favorable health behaviors and factors on all-cause and cardiovascular disease (CVD) mortality in 11,240 adults (23.5% women) aged 20-82 years enrolled in the Aerobics Center Longitudinal Study from 1987 to 2003. METHODS: All participants were free of CVD, cancer and abnormal electrocardiogram; had a body mass index (BMI) ≥18.5 kg/m2; and achieved ≥85% of age-predicted maximal heart rate on the treadmill test at baseline. Ideal Cardiovascular Health behaviors included not currently smoking, having a BMI=18.5-24.9 kg/m2, being physically active at or above 500 MET-minutes per week, and having a dietary pattern that includes at least two from a) ≥4.5 servings of fruit and vegetables per day, b) ≥ two 3.5-oz servings of fish per week; c) ≥ three 1-oz-equivalent servings of whole grains per day]. Ideal factors included serum total cholesterol <200 mg/dL, blood pressure <120/<80 mmHg, and fasting plasma glucose <100 mg/dL). RESULTS: During 11.6 ± 3.5 years of follow-up there were 268 deaths, 60 from CVD. Compared to participants with Poor Cardiovascular Health (0 to 2 behaviors/factors), hazard ratios (HR) of all-cause mortality were 0.73 (0.56-0.97) for those with Intermediate Cardiovascular Health (3 to 5 behaviors/factors), and 0.79 (0.52-1.21) for those with Ideal Cardiovascular Health (≥6 behaviors/factors), after adjustment for age, sex and examination year. Adjusted HRs for CVD mortality were 0.40 (0.24-0.68) and 0.22 (0.06-0.74) for Intermediate and Ideal groups respectively. The inclusion of cardiorespiratory fitness (CRF) as a health factor (>20% of age- and sex-specific ACLS cohort) decreased the adjusted HRs of Intermediate and Ideal groups for both all-cause (0.46 (0.33-0.64), 0.49 (0.31-0.79)) and CVD mortality (0.29 (0.16-0.53), 0.14 (0.04-0.50). CONCLUSION: AHA's definition of Ideal Cardiovascular Health presented a strong protective effect against CVD mortality. The diagnostic power of this tool can be improved by including CRF. Supported by NIH Grant AG06945, HL62508, DK088195, and an unrestricted research grant from the Coca-Cola Company.

Changes in Fitness following a Behavioral Weight Loss Program in Severely Obese Individuals

Behavioral weight loss programs that include both dietary and exercise components typically result in fitness improvements. However, severely obese individuals (BMI≥40 kg/m2) are often excluded from these programs; therefore it is unclear whether this population achieves similar increases in fitness and who among them are most likely to experience the greatest improvements. PURPOSE: To examine the effect of an intensive lifestyle intervention (ILI) on fitness and to identify factors associated with changes in fitness following a 1- year weight loss intervention. METHODS: 2570 participants in the Look AHEAD trial for individuals with type 2 diabetes were randomized to ILI and 2575 were randomized to the diabetes support and education (DSE) arm. ILI participants were instructed to reduce their caloric intake and increase their exercise to ≥175 min/week while DSE participants received general weight loss guidelines. All subjects completed a maximal exercise test at baseline and a submaximal test to 80% of age-predicted maximal heart rate (HRmax) at 1-year. Change in fitness was calculated as the difference in the MET value at 80% HRmax between baseline and 1-year. RESULTS: Severely obese ILI participants (N=492; BMI: mean±sd=44.8 ± 3.9 kg/m2,age: 56.4 ± 6.4 years; 66.2% female) had significant (p<0.001) improvements in absolute fitness (0.98 ± 1.2 METs) and % change in fitness (24.4 ± 30.1%) at 1-year which were significantly greater than individuals in DSE with severe obesity (p<0.001). Among ILI participants, absolute fitness was similar (p=0.68) and % change in fitness (p<0.05) was greater among the severely obese compared to those with a BMI <40. In ILI participants who were severely obese, those who had a lower baseline BMI, were younger, less fit, and were male, experienced the greatest improvements in fitness at 1 year (ps<0.001). CONCLUSIONS: Severely obese individuals achieved significant improvements in fitness at 1-year in an intensive lifestyle intervention that were similar to those with lesser degrees of obesity. Severely obese participants who were less fit at baseline experienced the largest improvements in absolute fitness at 1- year, suggesting that these individuals may receive the greatest fitness benefit from a behavioral weight loss program.

Changes in Cardiorespiratory Fitness and Percent Body Fat with Incident Metabolic Syndrome

The associations of changes in cardiorespiratory fitness (fitness) and % body fat (fatness) with metabolic syndrome (MS) are unclear. PURPOSE: We examined independent and combined associations of changes in fitness and fatness with incident MS in 5,575 adults (14% women) aged 18-82 years at baseline who were examined ≥3 times during 1979-2006. METHODS: All participants were free of CVD, cancer, abnormal ECG, diabetes, and MS; and all achieved ≥85% of age-predicted maximal heart rate on the treadmill test at baseline and 2nd examination. Fitness levels, in metabolic equivalents (METs), were estimated from a maximal treadmill test. Fatness was determined by underwater weighing or 7-site skinfold measurements. Changes in fitness and fatness were calculated as the changes in maximal METs or % body fat per year between baseline and 2nd examination (mean 2.1 years), and categorized into 'loss', 'stable', and 'gain'. Cox regression model included sex, age, examination year, maximal METs, % body fat, systolic blood pressure, glucose, triglyceride, HDL-cholesterol, waist circumference, smoking status, alcohol intake, physical activity at baseline, parental diabetes, and changes in % body fat (for fitness change) or maximal MET (for fatness change). RESULTS: There were 924 incident MS during 6.3 years of follow-up (from the 2nd through the last examination). The relative risks (RR) and 95% confidence intervals (CI) for incident MS were 0.72 (0.60-0.86) for stable fitness, and 0.67 (0.56-0.81) for fitness gain compared with fitness loss, and 1.14 (0.94-1.38) for stable fatness, and 1.30 (1.11-1.53) for fatness gain compared with fatness loss after adjusting for confounders and changes in fatness or fitness. In the joint analysis, compared with fitness loss and fatness gain group, participants with stable fitness or fitness gain showed lower risk of MS regardless of fatness change patterns, and the lowest risk was observed in fitness gain and fatness loss group (RR 0.45, 95% CI 0.35-0.58). CONCLUSIONS: Both fitness and fatness are independent risk factors of incident MS. Maintaining or improving fitness is associated with lower risk of MS, while increasing fatness is associated with higher risk of MS. Supported by NIH Grant AG06945, HL62508, DK088195, and an unrestricted research grant from the Coca-Cola Company.

Masked hypertension is “unmasked” by low-intensity exercise blood pressure

Purpose: Masked hypertension (MH) independently predicts mortality but cannot be diagnosed from clinic blood pressure (BP) taken under resting conditions. We sought to determine if MH could be identified from BP taken during a single bout of low-intensity exercise. Methods. BP was recorded at rest and during brief low-level cycling exercise (60–70% of age-predicted maximal heart rate) in 75 untreated subjects with a hypertensive response to exercise (aged 54 ± 9 years). All subjects underwent 24-h ambulatory BP monitoring (ABPM) and MH was defined as clinic BP < 140/90 mmHg and ABPM BP ≥ 130/80 mmHg. Results. There were 42 (56%) patients with MH, and at rest systolic (SBP) was higher in subjects with MH compared with those without MH (127 ± 9 vs 120 ± 9 mmHg; p < 0.05). During exercise, MH subjects had significantly higher SBP (188 ± 22 vs 168 ± 15 mmHg; p < 0.05), with a greater change from baseline (61 ± 21 vs 48 ± 15 mmHg; p < 0.05). Low-level exercise SBP was independently associated with MH, and if ≥175 mmHg, identified MH with 74% sensitivity and 67% specificity (p < 0.001). Conclusion. MH can be identified in untreated individuals from low-intensity exercise SBP. Further research on the diagnostic value of BP during early phases of exercise stress testing is needed.

Localized β-adrenergic receptor blockade does not affect sweating during exercise

The purpose of the current study was to determine the effect of a locally administered nonselective β-adrenergic antagonist on sweat gland function during exercise. Systemically administered propranolol has been reported to increase, decrease, or not alter sweat production during exercise. To eliminate the confounding systemic effects associated with orally administered propranolol, we used iontophoresis to deliver it to the eccrine sweat glands within a localized area on one forearm prior to exercise. This allowed for determination of the direct effect of β-adrenergic receptor blockade on sweating during exercise. Subjects (n = 14) reported to the laboratory (23 ± 1°C, 35 ± 3% relative humidity) after having refrained from exercise for ≥12 h. Propranolol (1% solution) was administered to a 5-cm(2) area of the flexor surface of one forearm via iontophoresis (1.5 mA) for 5 min. A saline solution was administered to the opposing arm via iontophoresis. Each subject then exercised on a motor-driven treadmill at 75% of their age-predicted maximal heart rate for 20 min, while sweat rate was measured simultaneously in both forearms. Immediately after cessation of exercise, the number of active sweat glands was measured by application of iodine-impregnated paper to each forearm. The sweat rate for the control and propranolol-treated forearm was 0.62 ± 41 and 0.60 ± 0.44 (SD) mg·cm(-2)·min(-1), respectively (P = 0.86). The density of active sweat glands for the control and propranolol-treated forearm was 130 ± 6 and 134 ± 5 (SD) glands/cm(2), respectively, (P = 0.33). End-exercise skin temperature was 32.9 ± 0.2 and 33.1 ± 0.3°C for the control and propranolol-treated forearm, respectively (P = 0.51). Results of the current study show that when propranolol is administered locally, thus eliminating the potential confounding systemic effects of the drug, it does not directly affect sweating during the initial stages of high-intensity exercise in young, healthy subjects.

Pulmonary Function and Abdominal and Thoracic Kinematic Changes Following Aerobic and Inspiratory Resistive Diaphragmatic Breathing Training in Asthmatics

This study investigated the effect of 8weeks, three times weekly, of aerobic exercise (AE), diaphragmatic inspiratory resistive breathing (DR), and aerobic exercise combined with diaphragmatic inspiratory resistive breathing (CE) on pulmonary function and abdominal and thoracic dimensions and kinematics in asthmatics. Eighty-eight inactive, moderate-persistent asthmatics were matched and randomly assigned to AE, DR, CE, or nonexercise control (NE) groups (n=22 each). AE subjects walked and/or jogged at 60% of age-predicted maximum heart rate. DR subjects performed diaphragmatic breathing combined with inspiratory resistive breathing at varying inspiration, expiration ratios. CE subjects utilized a combination of the AE and DR programs. AE, DR, and CE significantly (p≤0.05) improved chest dimensions and kinematics during inspiration at the height of the second intercostal space, during inspiration and expiration at the height of the xiphoid process, and during inspiration and expiration at the height of the midpoint between the xiphoid process and umbilicus. All exercise interventions significantly improved FVC, FEV(1), PEF, and IVC, while MVV improved following AE and CE. However, CE proved superior to AE at improving FVC (p=0.001), FEV(1) (p=0.001), and IVC (p=0.009). There were no significant changes (p>0.05) in any of the measured parameters in the NE group. CE produces adaptations greater than those for single-mode training in moderate-persistent asthmatics. The results suggest synergy rather than interference between aerobic exercise and diaphragmatic inspiratory resistive breathing and that this mode of training might be useful as an adjunct therapy in asthmatic patients.

Heart Rate Response During Exercise and Pregnancy Outcome in Women With Congenital Heart Disease

Cardiopulmonary exercise testing is often used to evaluate exercise capacity in adults with congenital heart disease including women who are considering pregnancy. The relationship between cardiopulmonary exercise testing parameters and pregnancy outcome has not been defined. We conducted a multicenter retrospective observational study of women with congenital heart disease who had undergone cardiopulmonary exercise testing within 2 years of pregnancy or during the first trimester. Cardiopulmonary exercise testing variables included peak oxygen consumption and measures of chronotropic response: peak heart rate, percentage of maximum age predicted heart rate, heart rate reserve (peak heart rate-resting heart rate), and chronotropic index [(peak heart rate-resting heart rate)/(220-age-resting heart rate)]. We identified 89 pregnancies in 83 women. There were 4 spontaneous abortions and 1 termination. One or more adverse cardiac events occurred in 18%; congestive heart failure in 14%, and sustained arrhythmia in 7%. Peak heart rate (odds ratio [OR] 0.71; 95% confidence interval [CI] [0.53, 0.94]; P=0.02), percentage of maximum age predicted heart rate (OR 0.93; 95% CI [0.88, 0.98]; P=0.01), and chronotropic index (OR 0.65; 95% CI [0.47, 0.90]; P=0.01) were associated with a cardiac event. Neonatal events occurred in 20%. Peak heart rate (OR 0.75; 95% CI [0.58, 0.98]; P=0.04), percentage of maximum age predicted heart rate (OR 0.94; 95% CI [0.89, 0.99]; P=0.02), heart rate reserve (OR 0.8; 95% CI [0.64, 0.99]; P=0.04), and chronotropic index (OR 0.73; 95% CI [0.54, 0.98]; P=0.04) correlated with a neonatal event. Peak oxygen consumption was not associated with an adverse pregnancy outcome. Abnormal chronotropic response correlates with adverse pregnancy outcomes in women with congenital heart disease and should be considered in refining risk stratification schemes.

Near infrared spectroscopy-derived interstitial hydrogen ion concentration and tissue oxygen saturation during ambulation

The objective of this study was to determine whether walking and running at different treadmill speeds resulted in different metabolic and cardiovascular responses in the vastus lateralis (VL) and lateral gastrocnemius (LG) by examining metabolite accumulation and tissue oxygen saturation. Ten healthy subjects (6 males, 4 females) completed a submaximal treadmill exercise test, beginning at 3.2kmh(-1) and increasing by 1.6kmh(-1) increments every 3min until reaching 85% of age-predicted maximal heart rate. Muscle tissue oxygenation (SO(2)), total hemoglobin (HbT) and interstitial hydrogen ion concentration ([H(+)]) were calculated from near infrared spectra collected from VL and LG. The [H(+)] threshold for each muscle was determined using a simultaneous bilinear regression. Muscle and treadmill speed effects were analyzed using a linear mixed model analysis. Paired t-tests were used to test for differences between muscles in the [H(+)] threshold. SO(2) decreased (P=0.001) during running in the VL and LG, but the SO(2) response across treadmill speeds was different between muscles (P=0.047). In both muscles, HbT and [H(+)] increased as treadmill speed increased (P<0.001), but the response to exercise was not different between muscles. The [H(+)] threshold occurred at a lower whole-body VO(2) in the LG (1.22±0.63Lmin(-1)) than in the VL (1.46±0.58Lmin(-1), P=0.01). In conclusion, interstitial [H(+)] and SO(2) are aggregate measures of local metabolite production and the cardiovascular response. Inferred from simultaneous SO(2) and [H(+)] measures in the VL and LG muscles, muscle perfusion is well matched to VL and LG work during walking, but not running.

Upregulation of circulating IL-15 by treadmill running in healthy individuals: Is IL-15 an endocrine mediator of the beneficial effects of endurance exercise?

The beneficial effects of endurance exercise include insulin-sensitization and reduction of fat mass. Limited knowledge is available about the mechanisms by which endurance exercise exerts the salutary effects. Myokines, cytokines secreted by skeletal muscle, have been recognized as a potential mediator. Recently, a role of skeletal muscle-derived interleukin-15 (IL-15) in improvement of fat-lean body mass composition and insulin sensitivity has been proposed. Yet, previous studies have reported that endurance training does not increase production or secretion of IL-15 in skeletal muscle. Here, we show that in opposition to previous findings, 30-min treadmill running at 70% of age-predicted maximum heart rate resulted in a significant increase in circulating IL-15 level in untrained healthy young men. These findings suggest that IL-15 might play a role in the systemic anti-obesogenic and insulin-sensitizing effects of endurance exercise, not only as a paracrine and autocrine but also as an endocrine factor.

Prognosis in patients achieving ≥10 METS on exercise stress testing: Was SPECT imaging useful?

BackgroundThe benefit of myocardial perfusion imaging (MPI) over exercise ECG stress testing alone is unclear in individuals attaining a workload of ≥10 METS. The purpose of this prospective study is to determine mortality and nonfatal cardiac events in patients at either intermediate pretest risk for CAD or patients with known CAD, achieving ≥10 METS regardless of peak exercise heart rate. The authors previously reported a low prevalence of significant ischemia in this patient cohort. MethodsBaseline characteristics, ECG stress test findings, and perfusion and function results from quantitative gated 99mTc-SPECT MPI were compared by achievement of a maximum age-predicted heart rate ≥85% in 509 consecutive patients who reached ≥10 METS. Events including all-cause and cardiac mortality, non-fatal myocardial infarction (MI), and late revascularization (>4 weeks after MPI) were prospectively collected. ResultsOf the 509 patients achieving ≥10 METS, follow-up for mortality was obtained in 463 (91%). Those lost to follow-up were older and had higher rates of tobacco use. The prevalences of CAD risk factors, prior known CAD, and MPI abnormalities were higher for the 68 patients failing to reach 85% of their target heart rate. The rate of ≥10% left-ventricular (LV) ischemia by MPI remained very low irrespective of attained heart rate (0.6% (3/463)). Six (1.2%) had an LVEF < 40%. Death occurred in 12 (2.6%) patients, one of which was classified as cardiac (0.1%/year). The other 11 deaths were related to cancer. Additionally, there were three nonfatal MIs (0.7 %) and one late revascularization (0.2%). Only one of these patients had any ischemia on MPI. No cardiac event patient had exercise ST depression or ≥5% LV ischemia. ConclusionsThus, patients at intermediate risk for CAD or known CAD achieving ≥10 METS have a very low prevalence of ≥10% LV ischemia and very low rates of cardiac mortality, nonfatal MI, and late revascularization, irrespective of heart rate achieved. Cardiac events did not correlate with abnormalities on the index MPI study. These results suggest that patients who attain ≥10 METS during exercise stress have an excellent prognosis over an intermediate term of follow-up, regardless of peak exercise heart rate achieved. The added value of MPI to standard exercise ECG testing in this population is questionable.

Quantifying Exertion Level During Exercise Stress Testing Using Percentage of Age-Predicted Maximal Heart Rate, Rate Pressure Product, and Perceived Exertion

To determine if the attainment of at least 85% of age-predicted maximal heart rate (APMHR), using the equation 220 - age, and/or at least 25,000 as the product of maximal heart rate and systolic blood pressure (rate pressure product, RPP) is an accurate indicator of exertion level during exercise stress testing. From May 1, 2009, to February 15, 2010, 238 patients (mean ± SD age, 49.3±11.9 years; 50% male) with symptoms suggestive of myocardial ischemia underwent an exercise stress test with the addition of ventilatory expired gas analysis and a myocardial perfusion study. Ventilatory expired gas analysis determined the peak respiratory exchange ratio (RER), which is considered a valid and reliable variable for quantifying a patient's exertion during exercise. Of the patients, 207 (87%) attained a peak RER of 1.00 or more, and 123 (52%) attained a peak RER of 1.10 or more. An APMHR of 85% or more and peak RPP of 25,000 or more were both ineffective in identifying patients who put forth a maximal exercise effort (ie, peak RER, ≥1.10). Perceived exertion was a significant indicator (P=.04) of patient exertion, with a threshold of 15 (6-20 scale) being an optimal cut point. The percentage of equivocal myocardial perfusion study results was significantly higher in patients who demonstrated a submaximal exercise effort by peak RER (P≤.007). Aerobic exercise testing is an integral component in the assessment of patients with suspected myocardial ischemia. Our findings indicate that the currently used percentage of APMHR and peak RPP thresholds are ineffective in quantifying a patient's level of exertion during exercise stress testing.

Chronotropic incompetence and coronary artery disease

Objective — Although chronotropic incompetence (CI) represents an independent predictor of mortality and incidence of coronary artery disease, its pathophysiological mechanisms remain unknown. The purpose of this investigation was to evaluate wall motion abnormalities of the left ventricle and location of coronary arterial lesions in patients with and without CI.Methods — After exclusion of confounding factors, 610 patients (mean age of 58.4 ± 11 years; 275 men) with ischaemia who underwent exercise echocardiography were studied. Based on heart rate (HR) reached in treadmill testing, patients were divided into two groups: ChI (97 patients who did not reach 85% of maximum HR recommended for age) and ChC (513 patients who achieved 85% of the maximum age-predicted HR).Results — There was a higher frequency of dyspnoea (5.2% vs. 0.6%, P = 0.003), systemic hypertension (69.1% vs. 57.3%, P = 0.031) and obesity (38.1% vs. 22.6%, P = 0.001), and a lower tolerance to effort (dyspnoea as limitation of physical effort: 36.1% vs. 8.0%, P < 0.0001; duration of treadmill test: 4.4 ± 2.2 vs. 7.2 ± 2.8, P < 0.0001; METs: 6.0 ± 2.6 vs. 8.4 ± 2.9, P = 0.002) in ChI compared to ChC. The wall motion score index (WMSI) was higher in ChI than in ChC, both at rest (1.15 ± 0.29 vs. 1.07 ± 0.19, P = 0.011) and after exercise (1.24 ± 0.29 vs. 1.15 ± 0.19, P = 0.002). Systolic function, which was evaluated in peak exercise through WMSI, was significantly more altered in the ChI group. The presence of severe injuries in right coronary was independently associated with CI (adjusted OR = 3.57, CI 95%: 1.86-6.87).Conclusion — Chronotropic incompetence is associated with ventricular dysfunction in peak exercise and critical right coronary artery lesions.