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PubMedDate not supplied

Exercise training in healthy type A middle-aged men: effects on behavioral and cardiovascular responses.

Thirty-six healthy Type A men (means = 44.4 years) were randomly assigned to either an aerobic exercise training group or a strength and flexibility training group. Subjects completed a comprehensive psychological assessment battery before and after the exercise programs consisting of behavioral, psychometric, and psychophysiological testing. The behavioral assessment consisted of repeated Type A interviews that were videotaped for subsequent component analyses. The psychometric testing included two self-report questionnaires to assess Type A behavior. The psychophysiological test consisted of a standard behavioral challenge, a mental arithmetic task, performed while cardiovascular responses were monitored. Aerobic exercise (AE) training consisted of 12 weeks of continuous walking or jogging at an intensity of at least 70% of subjects' initial maximal oxygen consumption (VO2max) as determined by an initial treadmill test. Strength and flexibility (SF) training consisted of 12 weeks of circuit Nautilus training with no aerobic exercise. After 12 weeks of exercise, the AE group increased their VO2max by 15%, while the SF group did not change. Both groups experienced decreases in overt behavioral manifestations of the Type A behavior pattern and self-reported Type A traits. However, the AE group showed an attenuation of heart rate, systolic and diastolic blood pressure, and estimated myocardial oxygen consumption (MVO2) during the task and had lower blood pressure, heart rate, and (MVO2) during recovery. In contrast, the SF group showed a significant reduction only in DBP during the task, which was likely due to habituation. These results support the use of aerobic exercise as a method for reducing cardiovascular risk among healthy Type A men.

Adult↗
PubMed1980

Heat injuries among recreational runners.

With the increasing popularity of jogging and competitive running, more people are participating in races, particularly during the warm months. In the Southeastern United States, the combination of high temperatures and high relative humidity appears to be responsible for many heat-associated injuries. We studied the training, racing, and selected personal characteristics of heat-injured and age- and sex-matched uninjured recreational runners at four races. The major differences between the two groups were that injured runners had not been running as long, ran fewer miles per week, ran fewer miles per training run, and were more likely to be caught up in the excitement of the event.

Athletic Injuries↗
PubMed1984

Acute prolapsed lumbar intervertebral disc. An epidemiologic study with special reference to driving automobiles and cigarette smoking.

An epidemiologic case-control study to identify risk factors for acute prolapsed lumbar intervertebral disc was undertaken in Connecticut during 1979-1981. This paper focuses on nonoccupational factors of possible etiologic significance. Persons in their 30s were affected most frequently. Among surgical cases, the ratio of men to women was 1.5 to 1, while among probable and possible cases not undergoing surgery, the male to female ratio was about 1 to 1. Cigarette smoking in the past year was associated with an increased risk for prolapsed disc. The greater the number of hours spent in a motor vehicle, the higher the risk. Use of Swedish and Japanese cars was associated with a lower-than-average risk, while use of other cars was associated with a higher-than-average risk. For each type of car, older cars were associated with higher risks than newer cars. Variables that did not affect the risk for prolapsed lumbar disc in this study included height, weight, number of pregnancies, number of children, frequency of wearing shoes with high heels, smoking cigars or pipes, and participation in baseball or softball, golf, bowling, swimming, diving from a board, tennis, bicycling or jogging.

Acute Disease↗
PubMed1999

New in vivo measurements of pressures in the intervertebral disc in daily life.

STUDY DESIGN: We conducted intradiscal pressure measurements with one volunteer performing various activities normally found in daily life, sports, and spinal therapy. OBJECTIVES: The goal of this study was to measure intradiscal pressure to complement earlier data from Nachemson with dynamic and long-term measurements over a broad range of activities. SUMMARY OF BACKGROUND DATA: Loading of the spine still is not well understood. The most important in vivo data are from pioneering intradiscal pressure measurements recorded by Nachemson during the 1960s. Since that time, there have been few data to corroborate or dispute those findings. METHODS: Under sterile surgical conditions, a pressure transducer with a diameter of 1.5 mm was implanted in the nucleus pulposus of a nondegenerated L4-L5 disc of a male volunteer 45-years-old and weighing 70 kg. Pressure was recorded with a telemetry system during a period of approximately 24 hours for various lying positions; sitting positions in a chair, in an armchair, and on a pezziball (ergonomic sitting ball); during sneezing, laughing, walking, jogging, stair climbing, load lifting during hydration over 7 hours of sleeping, and others. RESULTS: The following values and more were measured: lying prone, 0.1 MPa; lying laterally, 0.12 MPa; relaxed standing, 0.5 MPa; standing flexed forward, 1.1 MPa; sitting unsupported, 0.46 MPa; sitting with maximum flexion, 0.83 MPa; nonchalant sitting, 0.3 MPa; and lifting a 20-kg weight with round flexed back, 2.3 MPa; with flexed knees, 1.7 MPa; and close to the body, 1.1 MPa. During the night, pressure increased from 0.1 to 0.24 MPa. CONCLUSIONS: Good correlation was found with Nachemson's data during many exercises, with the exception of the comparison of standing and sitting or of the various lying positions. Notwithstanding the limitations related to the single-subject design of this study, these differences may be explained by the different transducers used. It can be cautiously concluded that the intradiscal pressure during sitting may in fact be less than that in erect standing, that muscle activity increases pressure, that constantly changing position is important to promote flow of fluid (nutrition) to the disc, and that many of the physiotherapy methods studied are valid, but a number of them should be re-evaluated.

Circadian Rhythm↗
PubMedDate not supplied

Central and peripheral adaptations after 12 weeks of exercise training in post-coronary artery bypass surgery patients.

PURPOSE: Training adaptations in patients with coronary artery disease (CAD) have been reported previously, but little is known about central and peripheral adaptations in those recovering from coronary artery bypass graft surgery (CABG). The purpose of this study was to examine the effects of 12 weeks of endurance exercise training on exercise performance and left ventricular and peripheral vascular reserve in a group of uncomplicated CABG patients. METHODS: Thirty-one patients were recruited and began training 8 to 10 weeks after uncomplicated CABG. Patients underwent progressive exercise training consisting of walking and jogging, at 75% to 80% maximal oxygen intake (VO2max). Measures of left ventricular function included ejection fraction (EF), ventricular volumes, and the pressure volume ratio, an index of contractility. Peak ischemic exercise calf blood flow and vascular conductance was determined using strain-gauge plethysmography. Maximal oxygen intake and submaximal blood lactate concentration also was determined. RESULTS: A significant improvement in VO2max (1497 +/- 60 mL/min versus 1691 +/- 71 mL/min) was observed after training. This change was accompanied by an increase in the EF during submaximal exercise (60 +/- 3% versus 63 +/- 2% at 40% VO2max; 61 +/- 3% versus 64 +/- 3% at 70% VO2max) (P < 0.05), and the change in EF from rest to exercise (delta EF). No changes were observed for ventricular volumes during exercise, although there was a trend for a higher stroke volume at 70% VO2max. A significant increase (18%) was observed for peak ischemic exercise calf blood flow and vascular conductance. In addition, submaximal blood lactate concentration was lower after training. CONCLUSIONS: These data indicate that exercise training for 12 weeks in patients recovering from CABG can elicit significant improvements in functional capacity that, for the most part, are secondary to peripheral adaptations, with limited support for improvement in left ventricular function.

Adaptation, Physiological↗
PubMedDate not supplied

Lipids, lipoproteins, and exercise.

PURPOSE: Dose-response relationships between exercise training volume and blood lipid changes suggest that exercise can favorably alter blood lipids at low training volumes, although the effects may not be observable until certain exercise thresholds are met. METHODS AND RESULTS: Plasma triglyceride reductions are often observed after exercise training regimens requiring energy expenditures similar to those characterized to increase high-density lipoprotein cholesterol (HDL-C). Thresholds established from cross-sectional and longitudinal exercise training studies indicate that 15 to 20 miles/week of brisk walking or jogging, which elicit between 1,200 to 2,200 kcals of energy expenditure per week, is associated with triglyceride reductions of 5 to 38 mg/dL and HDL-C increases of 2 to 8 mg/dL. Exercise training seldom alters total cholesterol and low-density lipoprotein cholesterol (LDL-C) unless dietary fat intake is reduced and body weight loss is associated with the exercise training program, or both. Thus, for most individuals, the positive effects of regular exercise are exerted on blood lipids at low training volumes and accrue so that noticeable differences frequently occur with energy expenditures of 1,200 to 2,200 kcals/week. CONCLUSIONS: It appears that weekly exercise caloric expenditures that meet or exceed the higher end of this range are more likely to produce the desired lipid changes. Regarding hyperlipidemic disorders, the primary means for intervention is pharmacologic, whereas diet modification, weight loss, and exercise, although important, are viewed as adjunctive therapies. Because much is known about the exercise training-induced plasma lipid and lipoprotein modifications as well as the mechanisms responsible for these changes, rehabilitation professionals can better develop a comprehensive medical management plan that optimizes pharmacologic, reduced dietary fat intake, weight loss, and exercise interventions.

Apolipoproteins↗
PubMed1998

How effective is exercise training for the treatment of hypertension?

OBJECTIVE: Exercise is often recommended as therapy for hypertension, yet its use is not widespread among clinicians. Reasons include uncertainty regarding its efficacy, the relative importance of the exercise prescription determinants (intensity and frequency), or confounding variables including patient characteristics such as age and gender. This review will present the evidence for exercise as a treatment for hypertension using a search of the English language literature from January 1966 to January 1998. DATA SOURCES: A search of MEDLINE articles using the MESH headings and textwords of blood pressure, hypertension, exercise, and exertion as well as hand searches in related articles and cross-referencing. DATA EXTRACTION AND SYNTHESIS: Identified articles were reviewed for their design characteristics, and specific attention was made of the subject characteristics, the exercise training protocol, the magnitude of the blood pressure-lowering response, and the influence of pharmacologic treatment on blood pressure lowering. RESULTS: A total of 39 studies representing random and nonrandom designs using predominantly walking-jogging exercise were identified. These studies showed reductions in blood pressure (systolic blood pressure/diastolic blood pressure) of -13/ -18 mm Hg in hypertensive patients. Most of the antihypertensive effect of exercise training was observed after 10 weeks, whereas training more than three times per week or for more than 50 minutes did not confer added benefit. Lower intensity exercise resulted in greater blood pressure reduction than did high intensity exercise. No gender differences in the antihypertensive effect of exercise were observed although most studies were performed in men. Although few studies were performed in older patients, there did not appear to be an age-dependent antihypertensive effect of exercise. There was a paucity of literature regarding the interaction of pharmacologic therapy and exercise in hypertensive patients. CONCLUSIONS: The results support the use of exercise as an effective therapy in hypertension. Studies were generally lacking in adequate control groups. Future research opportunities are many and should include studies using ambulatory monitoring and stratification of patients with different degrees of hypertension, undergoing different pharmacologic regimens.

Clinical Trials as Topic↗
PubMed1999

Stretching before exercise does not reduce the risk of local muscle injury: a critical review of the clinical and basic science literature.

OBJECTIVE: To evaluate the clinical and basic science evidence surrounding the hypothesis that stretching immediately before exercise prevents injury. DATA SOURCES AND SELECTION: MEDLINE was searched using MEDLINE subject headings (MeSH) and textwords for English- and French-language articles related to stretching and muscle injury. Additional references were reviewed from the bibliographies, and from citation searches on key articles. All articles related to stretching and injury or pathophysiology of muscle injury were reviewed. Clinical articles without a control group were excluded. RESULTS: Three (all prospective) of the four clinical articles that suggested stretching was beneficial included a cointervention of warm-up. The fourth study (cross-sectional) found stretching was associated with less groin/buttock problems in cyclists, but only in women. There were five studies suggesting no difference in injury rates between stretchers and nonstretchers (3 prospective, 2 cross-sectional) and three suggesting stretching was detrimental (all cross-sectional). The review of the basic science literature suggested five reasons why stretching before exercise would not prevent injuries. First, in animals, immobilization or heating-induced increases in muscle compliance cause tissues to rupture more easily. Second, stretching before exercise should have no effect for activities in which excessive muscle length is not an issue (e.g., jogging). Third, stretching won't affect muscle compliance during eccentric activity, when most strains are believed to occur. Fourth, stretching can produce damage at the cytoskeleton level. Fifth, stretching appears to mask muscle pain in humans. CONCLUSION: The basic science literature supports the epidemiologic evidence that stretching before exercise does not reduce the risk of injury.

Animals↗
PubMed2003

Discrete dislocation dynamics study of strained-layer relaxation.

Numerical simulations are performed to follow the evolution of an initial density of dislocation loops in an infinite strained layer to the point where the dislocations have stopped moving. Several unexpected results are obtained. First, many of the threading arms are either annihilated or prematurely immobilized by hardening interactions such as jogging and junction formation. Second, the remaining dislocation arms are eventually trapped by stress fluctuations that arise more from local overrelaxation than from the blocking mechanisms usually considered. Third, the degree of relaxation that can be attained depends strongly on the initial density of threading arms.

Journal Article↗
PubMed1980

Enzyme activities in serum after extensive exercise, with special reference to creatine kinase MB.

It is well documented that elevations of serum enzymes used as criteria in establishing the diagnosis of acute myocardial infarction (AMI) often show a pattern of AMI after physical exercise without other clinical signs of myocardial damage. Since a clinical condition resembling AMI sometimes appears after strenuous physical exercise, this study was designed to show if the new, almost heart-specific, isoenzyme creatine kinase MB (CK-MB) would solve the diagnostic problems. Ten well trained volunteers took part in a 26 km jogging race. None of them had any cardiovascular symptoms, but the 'old' cardiac enzymes rose in some of them above the discriminatory levels, whereas CK-MB was below these levels in all cases. It is concluded that CK-MB determination is a valuable diagnostic tool, also in patients who have recently exercised extensively.

Adolescent↗
PubMed1991

A controlled study of the effects of aerobic exercise on antihypertensive drug requirements of essential hypertensive patients in the general practice setting.

1. To investigate the effect of an exercise training programme on antihypertensive drug requirements, 19 sedentary subjects (14 men and five women) with mild essential hypertension (systolic blood pressure greater than 140 mmHg but less than 180 mmHg), aged 29-55 years, were randomly assigned to 16 weeks of moderate intensity exercise or light intensity exercise (control), and titrated on antihypertensive drug therapy (captopril and hydrochlorothiazide) until resting systolic blood pressure (sitting) of less than 140 mmHg was achieved. 2. The moderate exercise group (n = 11) followed a graded walk-jog programme to greater than 60% age-predicted maximum heart rate (HRmax), attending 45 min sessions, three times each week. The light exercise group (n = 8) followed a programme of flexibility (stretching exercises) and walking to less than 60% age-predicted HRmax, attending 45 min sessions, three times each week. 3. There was no difference between treatment groups for the level of reduction in both resting systolic and diastolic blood pressure over the 16 weeks (15.64 +/- 10.6/12.81 +/- 9.97 mmHg in the moderate intensity group and 15.31 +/- 10.9/7.7 +/- 7.1 mmHg in the light intensity group). The change in 24 h ambulatory blood pressure profile was also similar in both treatment groups. The final antihypertensive drug requirements to achieve these changes in blood pressure was not significantly different between the two treatment groups. This was despite a significant improvement in submaximal exercise performance in the moderate intensity exercise group (P less than 0.001). 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2006

Long-term prognosis of nonalcoholic fatty liver disease: is pharmacological therapy actually necessary?

BACKGROUND AND AIM: Nonalcoholic fatty liver disease (NAFLD) comprises a wide spectrum of liver injury, ranging from steatosis and steatohepatitis to cirrhosis. Reasons for the different natural course in individuals with NAFLD are still unclear. The aim of this study was to describe the natural course of disease in individuals with NAFLD who did not receive pharmacological therapy. METHODS: A total of 27 individuals with NAFLD (male/female ratio: 10/17, mean age 49.7 years) were prospectively enrolled. Management after diagnosis consisted of establishment of an appropriate diet and exercise (walking and jogging) program, treatment of associated metabolic conditions such as diabetes and dyslipidemia, and discontinuation of potentially hepatotoxic drugs if the patient was taking these. Liver tests were performed at diagnosis and at 3-month intervals during the follow-up period. Mean follow-up period was 43.3 months (range 36-49 months). RESULTS: From baseline to the end of the follow-up period, although there was no significant difference observed in terms of the mean body mass index, serum aminotransferase levels significantly improved (48.8+/-29.9 U/L to 31.6+/-16.0 U/L for aspartate aminotransferase [AST] and 66.3+/-38.3 U/L to 39.6+/-22.9 U/L for alanine aminotransferase [ALT]; P<0.05). No significant differences in platelet counts, serum albumin level or prothrombin time were observed (P>0.05). No patient developed signs of advanced liver disease during the follow-up period. CONCLUSION: A treatment strategy comprising diet, exercise and management of associated metabolic conditions is associated with improvement in aminotransferases among patients with NAFLD. Further investigation is needed to examine the long-term efficacy of this approach on liver histology and clinical outcomes.

Alanine Transaminase↗
PubMed1990

The weight control practices of 15 year old New Zealanders.

More than 800 15 year old members of the Dunedin Multidisciplinary Health and Development study cohort completed a questionnaire designed to provide descriptive data concerning the weight control behaviours of this sample of New Zealand adolescents. The results showed that approximately 75% of the adolescents were within acceptable body mass index ranges. However 68% of the girls (but only 19% of the boys) wanted to weigh less than their present weight. Generally, girls were more concerned about their body weight than boys: 26% of girls weighed themselves fortnightly or more often, compared with 12% of boys; 45% of girls reported that they were trying to lose weight at present, compared with 9.5% of boys. The main methods of weight reduction included weight reduction diets (21% of girls, 4% of boys in the previous year); exercise such as jogging, walking, swimming and cycling (60% of girls, 34% of boys); and participation in dieting and fitness clubs (35% of girls, 16% of boys). In addition, 20% of girls reported using techniques such as slimming tablets (3%), cigarette smoking (5%) and self-induced vomiting (5%) to control weight. The results show that weight control is a major preoccupation of many girls and some boys. Results are discussed in relation to differential social influences on the sexes, and health consequences.

Adolescent↗
PubMed2004

Effect of total hip arthroplasty on recreational and sporting activity.

BACKGROUND: Common concerns of patients undergoing total hip arthroplasty are whether they can continue with certain recreational and sporting activities or even commence new ones after the procedure. The present paper describes preoperative and postoperative activities, the numbers participating and the time to resume these activities. METHODS: Between 1 and 2 years after total hip arthroplasty, 216 patients, who had undergone a total of 235 arthroplasties, were surveyed by postal questionnaire to ascertain how the arthroplasty had affected their recreational and sporting ability. Their preoperative and postoperative activity along with the time to resume was recorded. A general hip score and estimate of physical activity was also collected. RESULTS: The number of patients participating in sport increased from 188 preoperatively to 196 postoperatively. Patients stated that the surgery had a beneficial effect on their performance of sporting activities although the number of sporting events decreased. By multiplying individuals by the number of sports they participated in, there were 434 occurrences of sport preoperatively giving a mean for the group of 1.9 sports per patient. Postoperatively this had reduced to 382, giving a mean of 1.7. Five sports showed a significant change for individual patients from pre to postoperation. Those which showed an increase were exercise walking, where 38 patients (16.8%) who did not walk before surgery took up walking afterwards (P < 0.0001) and aqua aerobics, where 15 took up this activity postoperatively for the first time (P = 0.002). There were three sports which decreased significantly from pre to postoperation. They were, golf where 13 out of 39 (P = 0.005), tennis 13 out of 14 (P = 0.01) and jogging where six out of seven (P = 0.01) patients stopped participating. CONCLUSION: This study has shown that patients are adopting lower impact activities to participate in after total hip arthroplasty. The total number of patients performing a sport increases postoperatively but the total amount of sport played decreases. These data will help to counsel patients.

Aged↗
PubMed2000

Aerobic exercise training-induced reductions in abdominal fat and glucose-stimulated insulin responses in middle-aged and older men.

OBJECTIVE: To test the effects of aerobic exercise training on glucose-stimulated insulin responses in middle-aged and older individuals. DESIGN: A 9-month moderate-intensity aerobic exercise training trial in 17 men. SETTING: An academic medical center. INTERVENTION: Subjects walked, jogged, or cycled at 50 to 60% heart rate reserve (HRR) three times per week for 30 to 45 minutes and progressed over 6 to 9 months until subjects were training at 80 to 85% of HRR for 45 to 60 minutes three to four times per week. Training intensity was stabilized for 2 weeks before retesting. Diets were stabilized on American Heart Association Step I diets before training, and calories increased to prevent weight loss. MEASUREMENTS: At baseline and after training, subjects underwent measurement of body fat (hydrodensitometry), regional fat distribution (waist-to-hip ratio (WHR)), VO2 max (maximal treadmill testing), diet intake (7-day food records), and glucose and insulin responses during 75 g, 2-hour oral glucose tolerance tests (OGTT) and 2-hour hyperglycemic (+/-7.9 mmol/L) glucose clamps. RESULTS: Aerobic exercise training increased VO2 max by 15% and decreased body fat from 22.8 +/- 1.6 to 20.8 +/- 1.5% (P < .0001), waist circumference by 2% (P = .038), and WHR by 1% (P = .035). Fasting glucose and insulin levels, and glucose responses during the OGTT did not change, but insulin responses during the OGTT decreased 16% (P = .027) after training. Training reduced early (0-10 minutes) and late (20-120 minutes) phase insulin responses by 14% (P = .017 and .042, respectively), but did not significantly change glucose disposal (+8%, P = .398). Multiple regression analyses showed that changes in waist circumference (r2 = 0.68, P < .0001) and percent body fat (r2 = 0.08, P = .049) were independent predictors of the reductions in the late phase insulin responses with exercise training, however, changes in VO2 max were not (P = .199). CONCLUSIONS: The decrease in glucose-stimulated insulin secretion with aerobic exercise training in middle-aged and older men appears to be mediated, at least in part, by reductions in the amount of abdominal fat. Regular physical exercise may prevent or ameliorate conditions associated with hyperinsulinemia including dyslipidemia, hypertension, and atherosclerosis in this group.

Age Factors↗
PubMed1988

Limitations of rate response of an activity-sensing rate-responsive pacemaker to different forms of activity.

The responses of an activity-sensing rate-responsive system (Activitrax) to various forms of physiological activity were assessed in 15 individuals who had this pacemaker. Nine were patients with complete heart block and atrial arrhythmias; their mean age was 60 years (range, 41-85 years). Six were age-matched healthy volunteers who were exercised with an external Activitrax system attached firmly to the chest wall. The pacemaker was programmed to achieve a pacing rate of about 100 bpm at the end of the first stage of the Bruce protocol (pacemaker settings: rate = 70-150 bpm; threshold = low to medium; response = 6-9). In the activity-sensing ventricular pacing mode, all patients achieved a significant increase in treadmill time compared to constant-rate ventricular pacing (mean +/- SD, 8.0 +/- 3.3 vs 5.4 +/- 2.3 minutes; p less than 0.01), with a mean maximum pacing rate of 123 +/- 18 bpm. Jogging in place produced a prompt increase in pacing rate, with the maximum achieved at the end of the exercise. However, physiological activities such as hand-grip, the Valsalva maneuver and standing resulted in only minimal rate response. Pacing rate after ascending 4 flights of stairs was the same as that achieved after descending the same stairs (100 +/- 8 vs 105 +/- 4 bpm; p = 0.1). All 15 subjects were exercised from resting heart rate for 3 minutes on a treadmill at 1.2 mph and 2.5 mph with four gradients at each speed. Although the pacing rate increased with a faster treadmill speed (p less than 0.005), it did not respond appropriately to a change in gradient compared to the sinus rate. We conclude that although activity-sensing rate-responsive pacing gives a prompt increase in pacing rate and improves maximum exercise tolerance, further refinement is necessary because: (1) physiological activities not associated with significant movement are not detected by this pacing system; (2) detection of vibrations as an indicator of activities does not correlate well with the level of exertion.

Adult↗
PubMed1992

Usefulness and adequacy of sensor data storage and retrieval for rate response simulation.

The usefulness of sensor data storage for rate response simulation was evaluated using a new dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay 294-03 [Intermedics Inc.]). The pacemaker can store the sensor output during routine exercise and those values can be used to simulate rate profiles for other rate response settings. The predictive value of this feature was evaluated in three studies (mechanical, external pacemaker, and implanted pacemaker). In the first study, the pacemaker was submitted to three runs of eight different mechanical calibrated to-and-fro movements. In the second study, nine external pacemakers were strapped on healthy volunteers who performed three jogging tests. Finally, the predictive value of the simulation was studied in five implanted patients during three successive walking tests. In each study, the pacemaker was submitted three times to the same activity. The responsiveness was successively set to 5, 1, and 10, and the pacemaker outputs were continuously recorded on a Holter monitor. At the end of the first run, rate profile simulations for slopes 1 and 10 were performed; slope 5 rate response was simulated after the second run. A regression analysis was used to establish the correlation between predicted and achieved pacing rates for each study. The coefficients of correlation between predicted and measured pacing rates for the mechanical, external, and clinical studies were 0.999, 0.985, and 0.823, respectively. The corresponding slopes of regression lines were 1.005, 0.971, and 0.935. Calculated rate profile has a high predictive value and could be used to optimize rate responsive settings without serial exercise testings.

Acceleration↗
PubMed1992

Clinical experience with an activity sensing DDDR pacemaker using an accelerometer sensor.

The rate adaptive characteristics and pacemaker mediated tachycardia protection algorithm of an accelerometer based DDDR pacemaker were evaluated in 11 patients with bradycardia (seven atrioventricular block, four sick sinus syndrome). Rate adaptive programming was effected by collecting the acceleration level during a 3-minute moderate exercise ("tailoring" of sensor). In comparison with an externally attached piezoelectric sensor, the accelerometer sensor showed lower rate changes during external tapping of the pacemaker (16 +/- 3 vs 29 +/- 4 ppm, P less than 0.02) and applied direct pressure (1 +/- 1 vs 40 +/- 3 beats/min, P less than 0.001) on the pacemaker. At nominal setting, the accelerometer sensor showed improved rate stability and higher rate response to jogging and standing, although responses to other daily activities and treadmill exercise were similar. Apart from changing the rate responsive slope, rate response could be improved by repeat "tailoring" of the sensor at a lower exercise level, resulting in better overall rate response characteristics. The ability of the rate monitoring software to collect acceleration levels for an activity and profile the projected rate response at different rate responsive settings allowed programming to be effected with the minimum amount of exercise testing. The pacemaker also discriminated atrial tachyarrhythmias from normal sinus response using the sensor to judge the appropriateness of the atrial rate, which correctly identified and prevented rapid ventricular tracking in two patients during atrial flutter/fibrillation.

Adult↗