Decreased exercise blood pressure in older adults after exercise training: contributions of increased fitness and decreased fatness.

OBJECTIVE: To describe the contribution of changes in fitness and fatness resulting from exercise training on changes in submaximal exercise blood pressure (BP) during treadmill testing. DESIGN AND SETTING: Prospective, randomised, controlled trial. PARTICIPANTS: Sedentary older adults (n = 115) with untreated prehypertension or mild hypertension. INTERVENTION: Six-month supervised aerobic and strength training. MAIN OUTCOME MEASUREMENT: Systolic BP (SBP) was assessed at rest and during each stage of a maximal graded exercise test (GXT) that determined Vo(2)peak. General and regional fatness was assessed by anthropometry, dual-energy x-ray absorptiometry and MRI. BP changes were calculated for each GXT stage, and multivariate regression models were used to describe the association of changes in exercise BP with changes in fitness and fatness. RESULTS: After training, exercisers versus controls had significantly increased Vo(2)peak and significantly lower measures of general and regional fatness. Also, stage-specific SBP was significantly lower at stage 3 (-9.4 vs -1.6 mm Hg, p = 0.03) and stage 4 (-7.9 vs -1.2 mm Hg, p = 0.03). Pooled regression analysis across all stages showed that exercisers had a 7.1 mm Hg reduction in SBP, but this reduction fell short of statistical significance (p = 0.12) compared with controls. A 1.0 ml/kg/min increase in Vo(2)peak and a 1.0 cm decrease in waist circumference independently predicted a 1.0 mm Hg decrease in exercise SBP (p = 0.04 and p = 0.001, respectively). CONCLUSIONS: Decreased exercise SBP was independently associated with decreased waist circumference, a marker of abdominal obesity and increased fitness. These findings suggest that exercise training improves multiple factors that have an independent influence on SBP.

Development of a guarded liquid ionization chamber for clinical dosimetry.

Liquid ionization chambers are considered superior to air-filled chambers in terms of size, energy dependence and perturbation effects. We constructed and tested a liquid ionization chamber for clinical dosimetry, the GLIC-03, with a sensitive volume of approximately 2 mm3. We also examined two methods to correct for general ion recombination in pulsed photon beams: that of Johansson et al, which modifies Boag's theory for recombination in gases, and an empirical method relating recombination to dose per pulse. The second method can be used even in cases where the first method is not applicable. The response of the GLIC-03 showed a stable, linear and reproducible decrease of 1% over 10 h. The liquid-filled GLIC-03 had a 1.1 +/- 0.4% energy dependence while that of the air-filled GLIC-03 was 2.1 +/- 0.3% between the 6 and 18 MV beams from a Clinac 21EX. The two methods for recombination correction agreed within 0.2% for measurements at 18 MV, 700 V, 100 MU min(-1). Measurements with the GLIC-03 in Solid Water in the build-up region of an 18 MV beam agreed with extrapolation chamber measurements within 1.4%, indicating that the GLIC-03 causes minimal perturbation.

Circuit weight training in cardiac patients.

This was a prospective, randomized evaluation of the safety and efficacy of 10 weeks of circuit weight training in patients, aged 35 to 70 years, with documented coronary artery disease. Circuit weight training refers to the performance of a series of weight-lifting exercises using a moderate load with frequent repetitions. Patients had participated in a supervised cardiac rehabilitation program for a minimum of 3 months before the study. Control patients (n = 20) continued with their regular exercise consisting of a walk/jog and volleyball program, while the experimental group (n = 20) substituted circuit weight training for volleyball. No sustained arrhythmias or cardiovascular problems occurred. The experimental group significantly increased treadmill time from 619 to 694 seconds while the treadmill time of the control group did not change. Strength in the experimental group increased by an average of 24% while there was no change in the control patients. Circuit weight training appears to be safe, and to result in significant increases in aerobic endurance and musculoskeletal strength compared with traditional exercise used in cardiac rehabilitation programs.

Usefulness of self-efficacy in predicting overexertion during programmed exercise in coronary artery disease.

Overexertion during group jogging was evaluated in relation to self-perceived functional capacity and ability to self-monitor exertional heart rate in 40 men, mean age 55 +/- 9 years, with documented coronary artery disease. Patients' confidence in their ability to jog various distances was measured with a jog self-efficacy (SE) scale before a group exercise program was begun. Depression, type A personality, and performance of symptom-limited treadmill exercise were also assessed. Later, each patient was monitored with ambulatory (Holter) electrocardiography during programmed group jogging. Ambulatory monitoring disclosed significant noncompliance with exercise prescriptions: 33% of patients exceeded their prescribed range of 70% to 85% of maximal treadmill heart rate for at least 10 minutes of the 20-minute exercise bout. Another 25% spent 10 minutes or longer exercising below the prescribed range. Pretest jog SE predicted the number of minutes patients exercised above or below the prescribed intensity, but depression, type A and treadmill performance measures did not. Self-monitoring accuracy (the amount of agreement between exercise heart rate recorded by the electrocardiogram and by the patient) was also related to the number of minutes patients exercised outside the prescribed range. Comparison of SE and self-monitoring accuracy variables revealed that "overachievers" were patients who overestimated their ability to jog, while "underachievers" were those who overestimated their heart rate during exercise. Self-perceptions and self-monitoring skills appear to be important independent predictors of behavioral compliance to exercise guidelines.

Effects of single nightly injections of growth hormone-releasing hormone (GHRH 1-29) in healthy elderly men.

Age-related reductions in growth hormone (GH) and insulin-like growth factor-I (IGF-I) may contribute to decreased muscle mass and strength in older persons. The relationship of this phenomenon to skeletal muscle bioenergetics has not been reported. We sought to determine whether administration of GH-releasing hormone (GHRH) would sustain increases in GH and IGF-I and improve skeletal muscle function and selected measures of body composition and metabolism. We measured GH secretion, muscle strength, muscle histology, and muscle energy metabolism by phosphorus nuclear magnetic resonance spectroscopy (31P-NMRS), body composition, and endocrine-metabolic functions before and after 6 weeks of treatment. Eleven healthy, ambulatory, non-obese men aged 64 to 76 years with low baseline IGF-I levels were treated at home as outpatients by nightly subcutaneous self-injections of 2 mg GHRH for 6 weeks. We measured GH levels in blood samples obtained every 20 minutes from 8:00 PM to 8:00 AM; AM serum levels of IGF-I, IGF binding protein-3 (IGFBP-3), and GH binding protein (GHBP); muscle strength; muscle histology; the normalized phosphocreatine abundance, PCr/[PCr + Pi], and intracellular pH in forearm muscle by NMRS during both sustained and ramped exercise; body composition by dual-energy x-ray absorptiometry (DEXA); lipid levels; and glucose, insulin, and GH levels during an oral glucose tolerance test (OGTT). GHRH treatment increased mean nocturnal GH release (P < .02), the area under the GH peak ([AUPGH] P < .006), and GH peak amplitude (P < .05), with no change in GH pulse frequency or in levels of IGF-I, IGFBP-3, or GHBP Two of six measures of muscle strength, upright row (P < .02) and shoulder press (P < .04), and a test of muscle endurance, abdominal crunch (P < .03), improved. GHRH treatment did not alter exercise-mediated changes in PCr/[PCr + Pi] or intracellular pH, but decreased or abolished significant relationships between changes in PCr/[PCr + Pi] or pH and indices of muscle strength. GHRH treatment did not change weight, body mass index, waist to hip ratio, DEXA measures of muscle and fat, muscle histology, glucose, insulin, or GH responses to OGTT, or lipids. No significant adverse effects were observed. These data suggest that single nightly doses of GHRH are less effective than multiple daily doses of GHRH in eliciting GH- and/or IGF-I-mediated effects. GHRH treatment may increase muscle strength, and it alters baseline relationships between muscle strength and muscle bioenergetics in a manner consistent with a reduced need for anaerobic metabolism during exercise. Thus, an optimized regimen of GHRH administration might attenuate some of the effects of aging on skeletal muscle function in older persons.

Comparing calibration methods of electron beams using plane-parallel chambers with absorbed-dose to water based protocols.

Recent absorbed-dose-based protocols allow for two methods of calibrating electron beams using plane-parallel chambers, one using the N(Co)D,w for a plane-parallel chamber, and the other relying on cross-calibration of the plane-parallel chamber in a high-energy electron beam against a cylindrical chamber which has an N(Co)D,w factor. The second method is recommended as it avoids problems associated with the Pwall correction factors at 60Co for plane-parallel chambers which are used in the determination of the beam quality conversion factors. In this article we investigate the consistency of these two methods for the PTW Roos, Scanditronics NACP02, and PTW Markus chambers. We processed our data using both the AAPM TG-51 and the IAEA TRS-398 protocols. Wall correction factors in 60Co beams and absorbed-dose beam quality conversion factors for 20 MeV electrons were derived for these chambers by cross-calibration against a cylindrical ionization chamber. Systematic differences of up to 1.6% were found between our values of Pwall and those from the Monte Carlo calculations underlying AAPM TG-51, and up to 0.6% when comparing with the IAEA TRS-398 protocol. The differences in Pwall translate directly into differences in the beam quality conversion factors in the respective protocols. The relatively large spread in the experimental data of Pwall, and consequently the absorbed-dose beam quality conversion factor, confirms the importance of the cross-calibration technique when using plane-parallel chambers for calibrating clinical electron beams. We confirmed that for well-guarded plane-parallel chambers, the fluence perturbation correction factor at d(max) is not significantly different from the value at d(ref). For the PTW Markus chamber the variation in the latter factor is consistent with published fits relating it to average energy at depth.

Exercise blood pressure response is related to left ventricular mass.

An exaggerated SBP response to exercise has been associated with increased left ventricular (LV) mass in some but not all studies. A total of 43 women and 34 men, aged 55-75 years, without evidence of cardiovascular disease, with a mean resting BP of 142+/-9/77+/-8 mmHg had their BP measured at rest and during maximal treadmill exercise. LV mass was measured using magnetic resonance imaging. LV mass was adjusted for lean body mass, which was assessed by dual energy X-ray absorptiometry. LV mass was within the normal range for the majority of the subjects. Among the resting and exercise BP indices, maximal SBP was the strongest correlate of LV mass (r=0.41, P<0.05). In multivariate analysis, maximal SBP was independently associated with LV mass after adjustment for lean body mass and gender, explaining 3% of the variance (P<0.05). Maximal exercise SBP is a modest but still independent predictor of LV mass in older persons with normal LV mass. These results raise the possibility that the SBP response to maximal exercise is an early marker of LV hypertrophy.

Introduction to the symposium: resistive weight training: a new approach to exercise for cardiac and coronary disease prone populations.

This symposium is concerned with the use of resistive exercise in cardiac and coronary prone populations. In the past, these populations have been refrained from resistive exercise. However, recent studies suggest that this form of exercise is safe and has favorable effects on physical fitness, cardiac risk factors such as hypertension and hyperlipidemia, and psychological status.

Resistive training effects on strength and cardiovascular endurance in cardiac and coronary prone patients.

Resistive training using heavy loads with few repetitions increases strength but does little to improve cardiovascular endurance. Circuit weight training, a form of resistive training using moderate loads with frequent repetitions, is used to improve both cardiovascular and strength fitness. Studies of circuit weight training in healthy adults and athletes have shown increases of 20-45% and cardiovascular improvement from 0 to 15%. An increasing number of exercise programs for cardiac and coronary prone populations have introduced circuit weight training. The few reported studies have shown that high risk patients can attain increases in fitness similar to those seen in healthy populations. Furthermore, the hemodynamic responses to circuit weight training suggest that it is a clinically safe and acceptable form of exercise.

Effects of diltiazem or propranolol during exercise training of hypertensive men.

This was a prospective, randomized, double-blind, placebo-controlled trial to establish whether beta blockers or calcium-channel blockers limit exercise capacity and training responses in men with mild hypertension. Circuit weight and aerobic training was used to assess the effects of drugs on cardiovascular fitness and muscle strength. Fifty-two sedentary men, ages 25-59 yr, with a diastolic blood pressure of 90-105 mm Hg off drugs, without significant ST depression during maximal stress testing, received diltiazem, propranolol, or placebo. Maximal oxygen uptake (VO2max) and exercise duration during treadmill testing, as well as one-repetition maximal strength, were assessed on eight weight machines after a single-blind placebo baseline, after 2 wk of drug run-in, and after 10 wk of exercise training. Total daily doses were 240 mg for propranolol and 360 mg for diltiazem. Propranolol decreased VO2max after drug run-in (P less than 0.05). Exercise training increased VO2max (P less than 0.05) in the diltiazem and placebo groups. After training VO2max in the propranolol group increased (P less than 0.05) from run-in but not beyond baseline levels. Thus, the reduction of VO2max consequent to propranolol therapy limited the overall benefits of training. Exercise duration did not change with run-in and increased (P less than 0.05) with training by 22%, 19%, and 10% for the diltiazem, placebo, and propranolol groups, respectively. Strength after run-in was unchanged, and exercise training increased strength (P less than 0.0001) on all weight machines in all groups. The results show an advantage of diltiazem to propranolol, particularly among physically active patients engaged in aerobic exercise who require antihypertensive therapy.

Self-efficacy mediates strength gains during circuit weight training in men with coronary artery disease.

Motivation to engage in health-promoting exercise has been ascribed to global personality traits such as self-esteem or athletic self-confidence. Self-Efficacy Theory challenges this view by proposing that highly specific estimates of personal capabilities mediate adoption of new or difficult behavior patterns. We tested this assumption by measuring self-efficacy perceptions in 40 men with coronary artery disease who participated in an experiment evaluating effects of circuit weight training (CWT). Specific self-efficacy estimates were assessed during baseline strength/endurance testing and after 10 wk participation in CWT or volleyball. Correlational analyses of self-efficacy in relation to performance on strength/endurance tests strongly supported the contention that adoption of novel activities is governed by highly specific self-perceptions. Participation in CWT produced greater strength and endurance gains than did volleyball, and these changes were accompanied by increased self-efficacy in CWT subjects for activities resembling the training tasks. The assertion that self-efficacy perceptions directly mediate involvement in challenging physical activities was supported by multiple regression analyses. These revealed that pre-training self-efficacy judgments predicted post-test strength gains even after controlling for baseline strength, type of training and frequency of participation in exercise sessions.

The effect of wall thickness on the response of a spherical ionization chamber.

Air-filled ionization chambers are used widely for radiation dosimetry. For some applications it is important to know the effect on the chamber response of photon attenuation and scattering in the chamber walls. Traditionally, the wall effect is determined by measuring the chamber response as a function of wall thickness and extrapolating linearly to zero thickness. We have constructed a spherical graphite chamber with variable wall thickness. The change in the chamber response with wall thickness has been measured in a 137Cs gamma-ray beam. Our data show that the change in response is not linear with wall thickness, in agreement with the theoretical prediction of Bielajew (1990 Med. Phys. 17 583-7). A linear versus non-linear extrapolation of the measured data to zero wall thickness leads to a difference of almost 1% in the estimate of the wall correction factor, Kw. The value of Kw obtained using the non-linear extrapolation is in good agreement with the result obtained using Monte Carlo techniques.

Exercise, lipids, and obesity in adolescents with parental history of coronary disease.

PURPOSE: The purpose of this study is to determine 1) if adolescents of parents with clinically manifest premature coronary artery disease (CAD) are less physically fit and habitually active, and have less favorable lipid profiles and more obesity than children of nonaffected parents, and 2) if aerobic fitness and activity are related to obesity and lipids in adolescents. SETTING: Patients were identified in the Coronary Care Unit or out-patient clinic. Adolescents were evaluated in the cardiovascular laboratories at the Francis Scott Key Medical Center. DESIGN: Comparisons between groups were tested with ANOVA: Univariate and multivariate regression were used to assess relationships among study variables. SUBJECTS: Thirty-six children of affected parents, ages 12 to 19 years, and 29 comparison subjects participated in the study. MEASURES: Fitness was determined by treadmill testing, fasting blood was analyzed for lipoprotein lipids, habitual physical activity was measured by self-report, and the sum of six skinfolds was used to calculate obesity. RESULTS: Total and LDL cholesterol were higher in girls with a parental history of CAD. The sample size was too small to draw any definitive conclusions about differences, based on parental history in lipids or fitness in the boys, or obesity in both genders. Overall, joggers were more fit and less fat than nonjoggers. Girls playing organized sports were more fit and less fat than nonparticipants. Aerobic fitness correlated negatively with obesity in both genders; fitness was independently associated with HDL cholesterol only in the boys. CONCLUSION: (ABSTRACT TRUNCATED AT 250 WORDS)

Mandibular distraction osteogenesis: a comparison of distraction rates in the rabbit model.

The rabbit model has been used to study the effects of different rates of distraction upon mandibular bone. Bilateral distraction was performed at two different rates anterior to the molar teeth. Both experimental groups were significantly inferior to sham operated controls in terms of bone density (DEXA) and mechanical testing. No difference in new bone formation between the two distraction rates was detected by these modalities. However, histological examination revealed non-union to be more common in the rapidly distracted group. This suggests that attempts to shorten the duration of external fixation in clinical mandibular distraction osteogenesis should be by methods other than more rapid distraction.

Establishing mechanisms to conduct multi-institutional research--fatigue in patients with cancer: an exercise intervention.

PURPOSES/OBJECTIVES: To describe the process of establishing a multi-institutional interdisciplinary team of oncology researchers and conducting a pilot study of an exercise intervention for fatigue. DATA SOURCES: Project meeting minutes and records, research team members' logs, subjects' research records, the research study proposal, and team members' individual and collective shared experiences. DATA SYNTHESIS: Site investigators established research teams at five academic medical centers. Fifty subjects were enrolled in the study and tested during their cancer treatment. Study methods, including instrumentation, were evaluated carefully and revised. CONCLUSIONS: The multi-institutional network of researchers is an effective and efficient model for testing an intervention to manage fatigue during cancer treatment. IMPLICATIONS FOR NURSING PRACTICE: Exercise is a feasible and potentially beneficial intervention to combat distressing cancer treatment-related fatigue. A pilot study is essential to determine the best methods for conducting a clinical trial and to develop the teams of researchers necessary for such a project.

Evaluation of methods for determining rearward static stability of manual wheelchairs.

Wheelchair standards have been under development for several years. A set of tests has been approved by the American National Standards Institute (ANSI) and by the International Standards Organization (ISO) but continue to be refined. Static stability is one of the indicators used to evaluate manual wheelchairs and is measured by placing a loaded wheelchair on a platform that is tilted until the wheelchair's front wheels lift off of the platform. Currently, if the wheelchair parking brakes slip, a block is placed behind the rear wheels and the tip angle is measured. The results for eight different wheelchairs with three load cases showed that the rearward tip angle for the block is significantly different (p < 0.05) from that with the brakes alone.

Power wheelchair range testing and energy consumption during fatigue testing.

The range of a power wheelchair depends on many factors including: battery type, battery state, wheelchair/rider weight, terrain, the efficiency of the drive train, and driving behavior. The purpose of this study was to evaluate the feasibility of three methods of estimating power wheelchair range. Another significant purpose was to compare the current draw on pavement to current draw on an International Standards Organization (ISO) Double Drum tester at one m/sec. Tests were performed on seven different power wheelchairs unloaded, and loaded with an ISO 100 kg test dummy. Each chair was configured according to the manufacturer's specifications, and tires were properly inflated. Experienced test technicians were used for the tennis court tests, and treadmill tests. An ISO 100 kg test dummy was used for the ISO Double Drum test. Energy consumption was measured over a distance of 1500 m for each of the three test conditions. The rolling surface was level in all cases. Repeated measure analysis of variance (ANOVA) revealed a significant difference (p = 0.0001) between the predicted range at maximum speed for the three tests. Post hoc analysis demonstrated a significant difference (p < 0.01) in estimated range at maximum speed between the Double Drum test and the treadmill test, as well as between the Double Drum test and the tennis court test. Our results indicate no significant difference (p > 0.05) between the predicted range at maximal speed between the treadmill and tennis court tests. A simple relationship does not exist between the results of range testing with the Double Drum tester and the tennis court. An alternative would be to permit the use of a treadmill for range testing as simple relationships between all pertinent treadmill and tennis court range data were found. For the Double Drum tester used, the current demand is higher than under normal usage. This presents a problem as current is related to load torque in a power wheelchair. Hence, the Double Drum tester friction must be reduced. The predicted range for the tennis court test at maximum speed ranges from a low of 23.6 km to a high of 57.7 km. The range of the power wheelchair can be improved by the use of wet lead acid batteries in place of gel lead acid batteries.

Posterior-variant alien hand syndrome: clinical features and response to rehabilitation.

PURPOSE: This case highlights the clinical features and course of recovery of a patient presenting to the rehabilitation service with posterior-variant alien hand syndrome (AHS) following thalamic stroke. METHODS: Single case report. RESULTS: Clinical signs and symptoms included mild hemiparesis, dyspraxia, dysmetria, primary sensory loss and hemispatial neglect. Autonomous movements and personification of the affected extremity which were ego-syntonic in nature were characteristic of posterior-variant AHS. The associated neurological impairments resolved early during the course of rehabilitation and the patient made excellent functional gains. CONCLUSION: This case highlights the distinguishing features differentiating posterior-variant AHS from more classical AHS and underscores the excellent prognosis of this variant.

Type 2 diabetes in Singapore: the role of exercise training for its prevention and management.

The prevalence of type 2 diabetes has been increasing in Singapore and is a major risk factor for cardiovascular disease. Exercise training is an important therapeutic modality for managing glycaemic control and improving cardiovascular health among persons with type 2 diabetes. It may also help to prevent or delay the onset of this harmful condition. This review examines the evidence and possible mechanisms by which exercise training produces these benefits, and gives a brief review of appropriate exercise activities.