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PubMed2006

Bed rest and myopathies.

PURPOSE OF REVIEW: The loss of skeletal muscle with injury or critical illness can be dramatic. This review emphasizes the importance of skeletal muscle as a metabolic reserve. Changes in protein metabolism with bed rest alone and during physiological stress are discussed. Nutritional and hormonal interventions that ameliorate the loss of skeletal muscle are highlighted. RECENT FINDINGS: The loss of skeletal muscle that occurs with inactivity alone can be prevented by nutritional supplementation with an essential amino acid formula. Bed rest with accompanying hypercortisolemia produces a threefold greater loss of skeletal muscle than bed rest alone. Essential amino acids stimulate muscle anabolism during acute hypercortisolemia; however, their effects during chronic hypercortisolemia must be explored. SUMMARY: Skeletal muscle loss with trauma or critical illness is due in great part to the interaction of bed rest (muscular inactivity) and stress (hypercortisolemia). Younger individuals respond to nutritional and pharmacological interventions during bed rest alone. Given a lower relative lean mass in the elderly and the importance of skeletal muscle as a metabolic reserve during stress, it is understandable that clinical outcomes are worse in older patients. Countermeasures to the loss of skeletal muscle, especially in the stressed patient, must be developed.

Bed Rest↗

PubMed2007

Assessment of biochemical aspirin resistance at rest and immediately after exercise testing.

Some aspirin-treated patients experience thromboembolic events, a phenomenon termed 'aspirin resistance', which may be clinical or biochemical by definition. Physical exercise is known to enhance platelet secretion and aggregability. To evaluate the presence of biochemical aspirin resistance at rest and immediately after exercise in individuals with stable coronary artery disease or coronary artery disease risk factors. We prospectively enrolled 101 patients who had received 100 or 300 mg/day enteric-coated aspirin for at least 7 days. Biochemical aspirin resistance (defined as normal collagen-epinephrine closure time < 165 s) was studied using the standardized platelet function analyzer. Of the 101 patients, 63 were aspirin sensitive both at rest and immediately after exercise, 18 exhibited biochemical aspirin resistance both at rest and after exercise, and 20 were aspirin sensitive at rest but exhibited biochemical aspirin resistance immediately after exercise. The results of exercise testing were similar in all three groups (each P > 0.05). Our results indicate that in almost 20% of the patients, aspirin did not seem to protect against exercise-induced platelet activation, despite the presence of aspirin sensitivity at rest. We did not, however, determine the extent to which the biochemical aspirin resistance noted in our study applied to clinical events.

Aged↗

PubMed1997

Automatic registration and alignment on a template of cardiac stress and rest reoriented SPECT images.

Single photon emission computed tomography (SPECT) imaging with 201Tl or 99mTc agent is used to assess the location or the extent of myocardial infarction or ischemia. A method is proposed to decrease the effect of operator variability in the visual or quantitative interpretation of scintigraphic myocardial perfusion studies. To effect this, the patient's myocardial images (target cases) are registered automatically over a template image, utilizing a nonrigid transformation. The intermediate steps are: 1) Extraction of feature points in both stress and rest three-dimensional (3-D) images. The images are resampled in a polar geometry to detect edge points, which in turn are filtered by the use of a priori constraints. The remaining feature points are assumed to be points on the edges of the left ventricular myocardium. 2) Registration of stress and rest images with a global affine transformation. The matching method is an adaptation of the iterative closest point algorithm. 3) Registration and morphological matching of both stress and rest images on a template using a nonrigid local spline transformation following a global affine transformation. 4) Resampling of both stress and rest images in the geometry of the template. Optimization of the method was performed on a database of 40 pairs of stress and rest images selected to obtain a wide variation of images and abnormalities. Further testing was performed on 250 cases selected from the same database on the basis of the availability of angiographic results and patient stratification.

Coronary Disease↗

PubMed2002

A predictive fatigue model--II: Predicting the effect of resting times on fatigue.

We have recently developed a force- and fatigue-model system that accurately predicted the effect of stimulation frequency on muscle fatigue. The data used to test the model were produced by stimulation trains with resting times of 500 ms. Because the resting times between stimulation trains affect muscle fatigue, this study tested the model's ability to predict the effect of resting times on fatigue. In addition, because this study included different subjects than those used to develop the model, the validity of the model could be tested. Data were collected from human quadriceps femoris muscles using fatigue protocols that included resting times of 500, 750, or 1000 ms. Our results showed that the model predicted fatigue as being a decreasing function of resting time, which was consistent with experimental data. Reliability tests between the experimental data and predictions showed interclass correlation coefficients of 0.97, 0.95, and 0.81 for the initial, final, and percentage decline in peak forces, respectively, suggesting strong agreement between the experimental data and the predictions by the model. The success of our current force- and fatigue-model system helps to validate the model and suggests its potential use in identifying the optimal activation pattern during clinical application of functional electrical stimulation.

Algorithms↗

PubMed1979

Effect of clinical bed rest for seven days on physical performance.

Twenty-two healthy men were confined to bed in a hospital ward (clinical bed rest) for one week. Variables related to physical fitness were measured before and immediately after the bed rest period, as well as one and three months thereafter. As a result of bed rest, maximal oxygen uptake, W170 and total Hb decreased to 94%, and calculated blood volume to 93% of the initial value. Hb concentration and Hct were unaltered. Thus, red cell and plasma volumes were proportionately reduced. No significant orthostatic dysfunction developed. The blood lactate peak at maximum work remained unchanged (14.0 mM/l). The resting exertion of noradrenaline decreased moderately during the bed rest period, whilst that of adrenaline was unchanged. Body weight decreased by a mean of 0.7 kg.

Adult↗

PubMed1985

Factors of prognostic importance for subsequent rest pain in patients with intermittent claudication.

The risk of developing rest pain during a six-year period was studied in 224 non-diabetic patients with intermittent claudication. Both smoking and multiple arterial stenoses in the leg were significantly correlated with an increased risk of developing rest pain. In non-smokers and in those who had stopped smoking within one year after the initial examination, the cumulative percentage of patients without rest pain after six years was 92, and in smokers and those who stopped smoking after more than one year it was 79 (p less than 0.03 after adjustment for differences in the presence of multiple stenoses). In patients with single stenosis the cumulative percentage of patients without rest pain was 86, and in those with multiple stenoses 70 (p less than 0.05 after adjustment for differences in smoking habits). The results emphasize how important it is that patients with intermittent claudication do not smoke. The increased risk of rest pain associated with the presence of multiple arterial stenoses in the leg should be considered when making decisions concerning vascular surgery.

Aged↗

PubMedDate not supplied

Bed-rest post-femoral arterial sheath removal--what is safe practice? A clinical audit.

Numbers of patients undergoing coronary angiography and angioplasty procedures have increased in England due to targets within the National Service Framework for Coronary Heart Disease. Little evidence is available regarding optimal bed-rest duration for patients post-femoral arterial sheath removal following these procedures. Through literature review and clinical benchmarking, we aimed to identify what best practice was in the UK and whether bed rest times at our centre could be reduced without increasing complications to enable increased day case procedures. An audit tool was designed to collect data regarding method of obtaining haemostasis, length of bed-rest post-sheath removal and any post-procedural complications experienced by the patient. From a convenience sample of consecutive patients, 195 complete sets of baseline data revealed an average (median) period of 6-h bed rest. This was reduced to 3h and audit repeated yielding 176 complete data sets using the same audit tool. Femoral wound site complication rates were not significantly affected by reducing bed-rest time for diagnostic or interventional procedures. These findings contributed to an important change in practice, reducing length of stay post-procedure and should be re-explored due to increased use of femoral arterial closure devices.

Angioplasty, Balloon, Coronary↗

PubMed1993

Effects of dilevalol (R,R-labetalol) compared with nifedipine on heart rate, blood pressure and muscle blood flow at rest and on exercise in hypertensive patients.

1. Dilevalol (R,R-labetalol) is a non-selective beta-adrenoceptor antagonist with beta 2-adrenoceptor agonist activity. Its effects after 1 month's administration on heart rate, blood pressure and muscle blood flow were studied in a double-blind crossover comparison with nifedipine in 16 hypertensive patients. 2. Dilevalol and nifedipine were similarly effective in lowering systolic and diastolic blood pressure at rest, but dilevalol limited the rise in systolic blood pressure induced by exercise more than nifedipine (rise of 27 vs 53 mm Hg respectively, P < 0.01). 3. Dilevalol decreased resting heart rate compared with nifedipine (73 vs 92 beats min-1 respectively, P < 0.01). Dilevalol limited the exercise induced rise in heart rate more than nifedipine (36 vs 48 beats min-1 respectively, P < 0.01). 4. Muscle blood flow (measured by strain gauge plethysmography) was not affected by either dilevalol or nifedipine at rest. After exercise, dilevalol caused an increase in excess blood flow compared with placebo (10.8 vs 5.1 ml min-1 dl-1 respectively, P < 0.01). The difference between dilevalol and nifedipine did not reach statistical significance (10.8 vs 6.5 ml min-1 dl-1 respectively, P > 0.05). 5. On blood pressure and heart rate, dilevalol demonstrated beta-adrenoceptor blocker activity at rest and on exercise. On muscle blood flow, dilevalol appeared to have no effect at rest, but may have acted as a beta-adrenoceptor blocker rather than as a beta 2-adrenoceptor agonist during exercise.

Adolescent↗

PubMed2006

Comparative effects of ivabradine, a selective heart rate-lowering agent, and propranolol on systemic and cardiac haemodynamics at rest and during exercise.

AIM: To compare in humans the effects of ivabradine and propranolol on cardiac and systemic haemodynamics at rest, during tilt and exercise. METHODS: Nine healthy volunteers randomly received single oral doses of ivabradine (Iva, 30 mg), propranolol (Propra, 40 mg) or placebo (Plac) during a double-blind cross-over study. Doses were selected to be equipotent in heart rate (HR) reduction. HR, systolic and diastolic blood pressure (SBP, DBP), cardiac index (CI, bioimpedance), rate pressure product (RPP), plasma epinephrine (E) and norepinephrine (NE), were measured at rest at baseline, before and after two tilt and exercise tests, started 2 and 5 h after drug intake. Heart rate variability (low to high frequency ratio LF/HF) was evaluated at rest and at 5 th minute of tilt. RESULTS: At rest, HR and RPP decreased similarly with Iva and Propra (both P < 0.01). During tilt, HR increased less with Iva than Propra (P < 0.01), LF/HF decreased after Iva (P < 0.03), SBP and mean blood pressure decreased after Propra (both P < 0.01), RPP decreased similarly after Iva and Propra (both P < 0.01) and CI decreased to a greater extent with Propra than with Iva or Plac (both P < 0.04). During exercise, Iva and Propra similarly decreased HR (both P < 0.01) and RPP (P < 0.01). CONCLUSIONS: These results demonstrate that for a similar decrease in HR at rest and during sympathetic stimulation, acute administration of ivabradine, a selective heart rate-lowering agent, decreased myocardial oxygen demand to the same extent as a reference beta-blocker, propranolol, but without evidence of depressant effect on cardiac function.

Adolescent↗

PubMed1992

Blood serum biochemical changes in physically conditioned and unconditioned subjects during bed rest and chronic hyperhydration.

1. It has been suggested that prolonged exposure to a rigorous bed rest regimen (hypokinesia) may induce greater serum carbohydrate and electrolyte changes in physically conditioned than unconditional subjects and that chronic hyperhydration may normalize or attenuate the development of these biochemical alterations in physically conditioned subjects. 2. Serum carbohydrate and electrolyte changes were determined in 18 physically healthy male volunteers aged 19-24 years during 30 days of a rigorous bed rest regimen. The subjects were divided into three equal groups. The first group consisted of six unconditioned subjects with VO2 max of 44 mL/kg bodyweight/min, the second group consisted of six conditioned subjects with VO2 max of 69 mL/kg bodyweight/min and the third group consisted of six conditioned subjects with VO2 max of 69 mL/kg bodyweight/min who consumed daily an additional amount of 26 mL water/kg bodyweight and 0.10 mg sodium chloride/kg bodyweight. 3. For the simulation of the hypokinetic effect all volunteers were kept under a rigorous bed rest regimen for 30 days. During the prehypokinetic period of 15 days and during the bed rest period of 30 days the concentrations of cortisol, aldosterone, testosterone, triiodothyronine (T3), thyroxine (total; T4), glucose, potassium, sodium and chloride were determined in blood serum of volunteers. 4. During the bed rest period of 30 days serum carbohydrate and electrolyte changes were more pronounced in physically conditioned than unconditioned hypokinetic subjects. In physically conditioned hyperhydrated subjects serum carbohydrate and electrolyte changes were less pronounced than in physically conditioned and unconditioned hypokinetic subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Rest versus heavy work during the last weeks of pregnancy: influence on fetal growth.

The influence of rest versus hard work on fetal growth at the end of pregnancy was assessed prospectively in a population of women who normally work hard during pregnancy. A group of 554 women living in Kalima area (Central Zaire) was admitted for rest in a maternity village for a median duration of 22 days. Self-selection, age, parity, number of living children, socio-economic status, maternal weight and height and gestational age were controlled for. Energy intake estimated in a sample of women in the maternity village and a sample of those staying at home was similar. Protein intake was found to be higher in the resting women. The duration of rest had a strong influence on birth-weight and length in the newborn females but to a lesser extent in the newborn males. There was a 7.5-fold decrease in the rate of low birth-weight in girls when the duration of maternal rest was greater than 21 days. In boys the low-birthweight rate remained unchanged. Although this sex difference could not be explained it is concluded that, in developing countries, avoidance of heavy work can help to raise birthweight and perhaps reduce perinatal mortality.

Adult↗

PubMed2005

Distribution of rest periods between electrically generated contractions in denervated muscles of rats.

Stimulation protocols for denervated muscles distribute the generated contractions either within treatment sessions followed by hours of rest, or repeated 24 h per day with each contraction followed by a constant interval of rest. Our purpose was to directly compare the effects of the same number of identically generated contractions having different temporal daily distributions. For 5 weeks in denervated extensor digitorum longus muscles of rats, between 100 and 800 contractions were generated daily, distributed either within worksets that alternated periods of activity and rest, or separated by constant intervals of rest. Most of the tested protocols maintained muscle mass and maximum force near values of innervated controls. Although 100 contractions daily generated at constant intervals were sufficient to maintain mass and force, 100 contractions during a 4-h treatment session followed by 20 h of rest were not sufficient, and mass and force were not different from values of denervated muscles.

Analysis of Variance↗

PubMed1993

The effects of unilateral stellate ganglion blockade on human cardiac function during rest and exercise.

INTRODUCTION: Left-sided stellate ganglion predominance has been proposed as a mechanism responsible for lethal ventricular arrhythmias, due to heterogenous ventricular repolarization. To determine the cardiovascular effects of such asymmetric sympathetic ganglion innervation in man, studies were performed in 15 patients undergoing unilateral stellate ganglion blockade for the management of chronic arm pain. METHODS AND RESULTS: Standard 12-lead ECGs, systemic blood pressure, body surface potential mapping, and radionuclide angiography were performed during rest and graded exercise before and after blockade. Successful unilateral blockade was accomplished in 13 of the patients, 11 of whom had right-sided blockade and two left-sided blockade. No significant changes due to blockade of stellate ganglia, including QT intervals, were detected during rest or graded exercise in standard ECGs. No cardiac rhythm disturbances occurred in these states. Body surface potential maps and arterial blood pressure were similar during resting supine and upright positions, as well as immediately after exercise before and after blockade. Unilateral ganglionic blockade did not modify resting or exercise cardiac ejection fractions. CONCLUSION: Unilateral stellate blockade in man does not induce untoward cardiovascular effects during rest or exercise.

Adult↗

PubMed1997

Fathers' experience of their partners' antepartum bed rest.

PURPOSE: To survey paternal worries, concerns, stresses, or problems and the type of support received by men whose partners were prescribed antepartum bed rest at home, or in the hospital, or both. DESIGN: Descriptive retrospective. A national subsample of 59 men whose mates were on pregnancy bed rest were randomly selected in 1995 from a nonrandom select sample of individuals who had contacted a bed-rest support group for information. METHODS: The Paternal Bed Rest Questionnaire of open-ended questions designed to detail paternal concerns, stresses, and supports was mailed to gathers. RESULTS: Major problems for fathers were assuming multiple roles, managing emotional responses, and caring for their partner. The major paternal worry was for the health of mate and fetus. Coping strategies included using tangible assistance; altering cognitive, behavioral, and emotional responses; and verbalizing worries. Fathers reported receiving little assistance from health care providers. CONCLUSIONS: Fathers experience extreme stress when pregnancy bed rest is prescribed for a mate. Family-centered care should include care of the partner whose mate is at high-risk. Interventions that reduce paternal worry and provide emotional and tangible support are needed.

Adaptation, Psychological↗

PubMedDate not supplied

Bed rest from the perspective of the high-risk pregnant woman.

OBJECTIVE: To describe the experience of prolonged bed rest from the perspective of women during high-risk pregnancies. DESIGN: A focused ethnographic study that used interviews, participant diaries, and field notes as data sources. SETTING: Participants were obtained from an acute-care hospital antepartum unit and an antepartum home care program. PARTICIPANTS: Twenty-four women with complications of pregnancy requiring prolonged bed rest (range, 7-50 days). RESULTS: A model of the stress process in pregnant women on bed rest emerged from the data analysis. Stressors were grouped into situational (sick role, lack of control, uncertainty, concerns regarding fetus's well-being, and being tired of waiting), environmental (feeling like a prisoner, being bored, and having a sense of missing out), and family (role reversal and worry about older children) categories. Two main mediators of stress were social support and coping. Families, friends, and professionals were perceived as sources of support. Women used coping strategies, such as keeping a positive attitude, taking it 1 day at a time, doing it for the baby, getting used to it, setting goals, and keeping busy. Manifestations of stress were evidenced by adverse physical symptoms, emotional reactions, and altered social relationships. CONCLUSIONS: Prolonged bed rest is a stressful experience for pregnant women at high risk. Understanding the stress process in pregnant women confined to bed rest may assist nurses in developing interventions to reduce stressors and enhance mediators.

Adaptation, Psychological↗

PubMed1979

"Hyperfrontal" distribution of the cerebral grey matter flow in resting wakefulness; on the functional anatomy of the conscious state.

Regional cerebral blood flow was measured with the intra-arterial 133 Xenon clearance technique using a multidetector device in 11 patients undergoing carotid angiography (with normal findings). During the flow studies the patients were awake and strict resting conditions were observed. The patients did not move or speak, and sensory stimulation were kept at a minimum. It was confirmed that the distribution of the grey matter blood flow showed a hyperfrontal pattern, the flow in frontal regions being significantly (20-40%) higher than in postcentral, occipital and temporal regions. There were no technical factors or morphological features of the telencephalon which could explain this difference. It was also shown that the distribution of the white matter flow and the relative weight of the grey matter corresponded in general to hemisphere morphology. Since in normal nervous tissue the blood flow is regulated by the neuronal activity, the following interpretation is given of the main finding. The hyperfrontal flow distribution of the grey matter (cortical) flow during resting wakefulness shows that there is a high activity in frontal "efferent" (motor-behavior) regions. At the same time there is a low activity in post-central and temporal "afferent" (sensory-gnostic) cortical areas. The high frontal activity suggests that in the resting conscious state--unaccompanied by movements, speech or behavioral reactions--the brain is active with an anticipatiory "simulation of behavior". The low postcentral flow, on the other hand, may possibly be related to a global inhibition of the sensory input. Several clinical as well as general biologic arguments are forwarded to support this interpretation. It is further pointed out that the hyperfrontal distribution of the resting activity in the cerebral cortex correlates to the resting EEG, in which lower frequencies (the alpha rhythm) predominate in postcentral and temporal regions where there is a low flow/activity, and high frequencies in frontal areas where the blood flow is high. This is in agreement with the finding that the blood flow and metabolism of the brain correlate to the EEG frequency content.

Aged↗

PubMed2004

Abnormally elevated intramuscular pressure impairs muscle blood flow at rest after exercise.

We used photoplethysmography (PPG) to measure the relative changes in the anterior tibial muscle blood flow (MBF) in response to exercise when intramuscular pressure (IMP) was elevated (the test leg) or when IMP was normal (the control leg). The elevated IMP was induced by applying venous obstruction of 40 mmHg or 65 mmHg (thigh tourniquet) of a casted leg in eight healthy subjects. Subjects performed dorsiflexion of both feet in sitting position with or without venous obstruction. IMP at rest after exercise increased to 39.4+/-7.9 mmHg or to 58.3+/-8.4 mmHg, respectively. MBF at rest before exercise was 100%. At rest after exercise, it increased to 184+/-52.6% in the test leg when IMP was 39.4 mmHg, and to 279+/-108.3% in the control leg. MBF at rest after exercise was 156+/-58.2% in the test leg when IMP was 58.3 mmHg and 303+/-95.3% in the control leg. The abnormally elevated IMP induced by venous obstruction of a casted leg reduced MBF at rest after exercise. PPG seems to be a suitable method to measure changes in MBF in response to exercise and in experimental conditions with abnormally elevated IMP.

Adult↗

PubMed1993

Selective brain cooling in resting and exercising Norwegian reindeer (Rangifer tarandus tarandus).

The threshold body core temperature for selective brain cooling (SBC) as well as the slope of brain cooling were determined in three Norwegian reindeer (Rangifer tarandus tarandus) during rest and during exercise. Brain temperature was measured in the hypothalamus (Thypo) and blood temperature (Tblood) was measured either in the right carotid artery or in a few cases in the right atrium of the heart. During rest the animals were subjected to ramp-like increases of Tblood by means of a thermostatically controlled water circulated heat exchanger (HE) introduced into the rumen via a chronically implanted rumen cannula. During exercise the animals ran on a treadmill at a speed of between 5.5-8.0 km hr-1 and a slope of 13.5 degrees for periods of 30-60 min. The elevation of Tblood during both rest and exercise resulted in significant amounts of SBC. The mean threshold for SBC (Thypo = Tblood) during rest was 38.7 degrees C. The threshold for SBC was elevated significantly to 39.5 degrees C during exercise. The mean slope of SBC (increase of SBC per degree increase of Tblood) was 0.82 both during rest and exercise.

Animals↗