Prediction of maximal heart rate in individuals with mental retardation.

PURPOSE: It is well known that individuals with mental retardation (MR), especially those with Down syndrome (DS), have low maximal heart rates (MHR). We evaluated the ability to predict MHR in individuals with MR and DS in comparison with persons without MR. METHODS: Subjects completed a maximal exercise test on the treadmill with metabolic and HR measurements. Stepwise multiple regression was used to develop prediction equations for subjects with MR (N = 276; 97 with DS) and without (N = 296) MR, ranging in age from 9-46 yr. RESULTS: Subjects with MR exhibited significantly lower MHR (177 vs 185 beats.min(-1)) and VO2peak (33.8 vs 35.6 mL.kg-1.min(-1)). In subjects with MR, age was a poor predictor of MHR, Y = 189 - 0.59 (age) (R = 0.30, SEE = 13.8 beats.min-1; P < 0.01), but age was a better predictor for subjects without MR, Y = 205 - 0.64 (age) (R = 0.52, SEE = 9.9 beats.min(-1); P < 0.01). A large sample Z test indicated that these regression coefficients were significantly different (P < 0.01). However, adding DS to the regression improved the prediction for subjects with MR, Y = 210 - (0.56 age) - (15.5 DS) (R = 0.57; SEE = 11.8 beats.min(-1), P < 0.01). CONCLUSION: MHR can be predicted with similar accuracy in subjects with and without MR, provided DS is accounted for in the equation for the subjects with MR.

Theoretical review: altered pain regulatory systems in chronic pain.

This review synthesizes the existing literature regarding the relationship between resting blood pressure and pain sensitivity, and the literature indicating possible endogenous opioid dysfunction in chronic pain. Adaptive interactions between the cardiovascular and pain regulatory systems occur in healthy individuals, with greater blood pressure associated with decreased acute pain sensitivity. Endogenous opioids appear necessary for full expression of this relationship. There is ample evidence indicating diminished endogenous opioid CSF/plasma levels in chronic pain patients, yet little is known about the functional effects of these opioid changes. A theoretical model is proposed based upon the literature reviewed suggesting progressive dysfunction in endogenous opioid systems with increasing chronic pain duration. This dysfunction is hypothesized to result in dysregulation of normally adaptive relationships between the cardiovascular and pain regulatory systems, resulting in increased chronic pain intensity and increased acute pain sensitivity among chronic pain patients. Preliminary data are consistent with the hypothesis of progressive opioid changes resulting in dysfunctional alterations in the adaptive blood pressure-pain relationship. Clinical implications of this theory are discussed.

Validity of a modified aerobic fitness test for adults with mental retardation.

PURPOSE: The purpose of this study was to determine whether further modifications to the Rockport Fitness Walking Test (RFWT) protocol produces similar results to the previously modified protocol (Rintala et al., 1992) used for adults with mental retardation (MR). A second purpose of this study was to evaluate prediction equations developed to estimate aerobic capacity from the 1:5RFWT. METHODS: In an effort to make the RFWT more efficient for testing adults with MR the one pacer to one walker protocol (1:1RFWT) was further modified to one pacer to five walkers (1:5RFWT). Ten healthy men and 13 women (21.7 +/- 2.6 yr) with MR (IQ = 42-68) performed graded maximal treadmill tests, one 1:1RFWT and two 1:5RFWT. RESULTS: The end times (P = 0.326) and end heart rates (P = 0.457) did not significantly differ between the 1:1RFWT, the first 1:5RFWT, and the second 1:5RFWT. Separate Bland and Altman plots indicated that both end time and end heart rate had good agreement between protocols and also had good repeatability between the two 1:5RFWT. The main predictor variable, end time, from the 1:1RFWT and the 1:5RFWT was highly (and similarly) associated with the measured aerobic capacity (VO2peak), indicating a high predictive value for the 1:5RFWT end time. Bland and Altman plots of predicted and measured VO2peak for the prediction equations of Kline et al. (1987) and Rintala et al. (1987) indicated a general overestimation of measured values. CONCLUSIONS: The 1:5RFWT provides similar end times and end heart rates as the 1:1RFWT along with similar associations of end times to measured VO2peak. The 1:5RFWT could be used to predict aerobic capacity; unfortunately, the present prediction equations overpredict VO2peak for adults with MR and need to be revised.

Endogenous opioids inhibit ambulatory blood pressure during naturally occurring stress.

OBJECTIVE: Laboratory experiments suggest that endogenous opioids inhibit blood pressure responses during psychological stress. Moreover, there seem to be considerable individual differences in the efficacy of opioid blood pressure inhibition, and these differences may be involved in the expression of risk for cardiovascular disease. To further evaluate the possible role of opioid mechanisms in cardiovascular control, the present study sought to document the effects of the long-lasting oral opioid antagonist naltrexone (ReVia, DuPont, Wilmington, DE) on ambulatory blood pressure responses during naturally occurring stress. METHOD: Thirty male volunteers participated in a laboratory stress study using naltrexone followed by ambulatory blood pressure under placebo and during the subsequent 24-hour period. Within-subject analyses were performed on ambulatory blood pressures under placebo and naltrexone conditions. RESULTS: Laboratory results indicate no significant group effects of naltrexone on blood pressure levels or reactivity. Ambulatory results indicate that during periods of low self-reported stress, no effect of opioid blockade was apparent. In contrast, during periods of high stress, opioid blockade increased ambulatory blood pressure. CONCLUSIONS: These findings suggest that naltrexone-sensitive opioid mechanisms inhibit ambulatory blood pressure responses during naturally occurring stress.

Altered cardiovascular/pain regulatory relationships in chronic pain.

In healthy individuals, there is an inverse relationship between resting blood pressure (BP) and pain sensitivity. This study examined possible dysregulation of this adaptive relation in chronic pain patients, and tested whether the extent of this dysregulation is a function of pain duration. Continuous resting BP's were assessed for 5 min after a 5-min rest period in 121 chronic benign pain patients. Unlike the inverse relationship observed previously in normals, mean resting diastolic. BPs during the assessment period were correlated positively with ratings of pain severity. A Pain Duration x Systolic BP interaction emerged (p < .05) such that the magnitude of the BP-pain relation was greatest in patients with the longest duration of pain, r(38) = .50, p < .001. A hypothesized progressive alteration in endogenous pain regulatory systems in chronic pain patients was supported. A possible role of endogenous opioid dysfunction in accounting for these alterations is discussed.

Effects of parental history of hypertension and urbanization on blood pressure in Zimbabweans.

The increasing prevalence of essential hypertension is a growing public health concern for Zimbabwe and other African countries. Two important risk factors for hypertension are urbanization and parental history of hypertension. The relations among parental history of hypertension, urbanization, and blood pressures (BPs) are poorly understood. The objective of this study is to clarify these relations in a population of urbanized, African, young adults. The relation between parental history of hypertension and urbanization on resting BP's and Bp responses to a mental arithmetic stressor was examined in a group of normotensive, Black medical students with (n = 36) and without (n = 34) a parental history of high BP, and with (n = 49) and without (n = 19) a parental history of urbanization. Results indicate that those with a positive parental history counterparts. Further, those with parents residing in urban areas had higher resting SBPs than those with parents residing in rural areas. However, no reactivity differences were apparent between the urban and rural parent groups. These data suggest that although parental history for hypertension influences both resting and reactivity BP's parental history of urbanization may influence only resting BP.

Plasma catecholamine and lactate relationship during graded exercise in men with spinal cord injury.

Catecholamine and lactate responses to incremental exercise were examined in individuals with spinal cord injury (SCI). Three men with high-level (HINJ) and four with low-level (LINJ) SCI performed VO2peak exercise tests on an arm ergometer. Forearm venous blood samples taken at rest and at the end of each work stage were analyzed for norepinephrine (NE), epinephrine (EPI), and lactate (LA) content. Mann-Whitney tests revealed that peak LA, NE, and EPI responses were greater in LINJ compared with HINJ subjects (LA = 7.1 +/- 0.5 vs 3.2 +/- 0.4 mM; NE = 3.1 +/- 1.0 vs 0.4 +/- 0.1 ng.ml-1; EPI = 0.5 +/- 0.2 vs 0.1 +/- 0.01 ng.ml-1). Spearman rank correlations for LINJ and HINJ groups were NE-EPI, rs = 0.85 vs rs = 0.17; NE-LA, rs = 0.83 vs rs = 0.31; and EPI-LA, rs = 0.73 vs rs = 0.41. The strong relationships between NE, EPI, and LA in the LINJ group were similar to those previously reported in able-bodied athletes. However, the relatively weak association between these factors in the HINJ group indicates that, while some function exits, the sympathoadrenal response to exercise is significantly impaired in these individuals. These results suggest that mechanisms other than catecholamines are primarily responsible for muscle lactate production during incremental exercise in individuals with HINJ.

Effects of stretch-based progressive relaxation training on the secretion of salivary immunoglobulin A in orofacial pain patients.

There is a growing body of evidence that psychologic stressors can affect physical health and proneness to disease through depletion of the body's immune system. Relatively little research, however, has investigated the potential immunoenhancing effect of stress-relieving strategies such as progressive muscle relaxation. This study explored the relationship between immune functioning and relaxation training with persons experiencing persistent facial pain. In a single experimental session, 21 subjects either received relaxation training or rested for an equivalent time period. Salivary immunoglobulin A, mood, pain, and tension levels were measured before and after relaxation and rest periods. Results indicated that a greater proportion of those receiving relaxation training had increases in secretion of salivary immunoglobulin A. These findings suggest that immunoenhancement may be another potential benefit of progressive relaxation training for persons with chronic pain conditions.

Cross validation of the 1-mile walking test for men with mental retardation.

The purpose of this study was to cross validate the equation developed by Rintala et al. (1992) to estimate the cardiorespiratory efficiency of men with mental retardation (MR). Subjects were 19 healthy men (27 +/- 8 yr) with MR (IQ = 58 +/- 12). Following familiarization, a graded maximal treadmill test and two 1-mile walk tests (Rockport Fitness Walking Test, RFWT) were administered. The peak VO2 value was the criterion measure used to cross validate the equation. The equation was: Peak VO2 (ml.kg-1.min-1) = 101.92 - 2.356 (MILE)-0.420 (WEIGHT). The mean differences were 2.04 (MILE1)(P = 0.02) and 2.43 (MILE2)(P = 0.004) ml.kg-1.min-1. A significant positive correlation was found between measured peak VO2 and predicted peak VO2 on both 1-mile walks (r = 0.91 and 0.93). For both predicted peak VO2 values, the Total Error (TE) was greater than standard error of estimate (SEE), indicating a systematic difference between the measured and predicted peak VO2 values. Moreover, only 58% of the measured peak VO2 values fell within the prespecified range. Test-retest reliability of RFWT was R = 0.96. However, the prediction equation underestimated the actual cardiorespiratory levels in 74% and 79% of the subjects, depending on the trial. Because the equation developed in this research underestimates the measured VO2 values for the majority of these subjects, the test is probably not statistically valid, even if reliable, and the prediction formula needs to be revised for this population.

The effects of age, gender, and family history on blood pressure of normotensive college students.

Offspring with a parental history of hypertension are, by some estimates, four times more likely to develop the disease (Corvol et al., 1992). While some studies suggest that an increased risk is observable in eight year old children, others suggest that the increased risk does not become apparent until age 20. This study examined this discrepancy by screening resting blood pressures from 403 young adults. After adjusting for body mass, a significant family history x age x gender interaction (p < .01) suggests that the effect of family history on systolic blood pressure varies by age and gender. The influence of positive family history becomes apparent in males by age 20 and in females by age 22. This relationship may help provide a rationale for interpretation and reconciliation of disparate results in the literature, and clarify our understanding of the etiologic mechanisms responsible for development of essential hypertension.

Prenatal maternal blood pressure response to stress predicts birth weight and gestational age: a preliminary study.

OBJECTIVE: The objective was to test the prospective association between prenatal maternal circulatory responses to a standardized psychologic challenge and birth outcome. STUDY DESIGN: We examined the relationship between blood pressure responses to a cognitive arithmetic stressor and birth outcome in 40 healthy primigravid women. Pregnant women between 18 and 37 years old were recruited from the University of Kentucky Prenatal Service Clinic for participation. All women performed an interactive arithmetic task while maternal heart rate and blood pressures were determined. Subsequent birth outcome parameters of birth weight and gestational age were obtained for prospective analyses. RESULTS: Results indicated that maternal systolic and diastolic blood pressures and heart rates were significantly increased during the arithmetic task (p < or = 0.01). Regression analyses suggested that women with larger diastolic blood pressure responses during stress had infants with lower birth weights (p < 0.01) and decreased gestational age (p < 0.05). CONCLUSIONS: This effect was specific to psychologic stress reactivity and was not related to maternal age, maternal race, baseline blood pressures, the trimester of stress testing, nor expired carbon monoxide. The relationship between maternal blood pressure response and birth outcome may reflect the transplacental impact of individual differences in systemic stress responsivity.

Relaxation training and opioid inhibition of blood pressure response to stress.

The present study was designed to determine the role of endogenous opioid mechanisms in the circulatory effects of relaxation training. Opioid mechanisms were assessed by examination of the effects of opioid receptor blockade with naltrexone on acute cardiovascular reactivity to laboratory stress before and after relaxation training. Thirty-two young men with mildly elevated casual arterial pressure were recruited for placebo-controlled naltrexone stress tests and relaxation training. The results indicated that relaxation training significantly reduced the diastolic pressure response to mental arithmetic stress. Opioid receptor blockade with naltrexone antagonized the effects of relaxation training. These findings suggest that some of the physiological effects of relaxation training are mediated by augmentation of inhibitory opioid mechanisms.

Psychological coping with acute pain: an examination of the role of endogenous opioid mechanisms.

This study examined the relationship among endogenous opioids, Monitoring and Blunting coping styles, and acute pain responses. Fifty-eight male subjects underwent a 1-min pressure pain stimulus during two laboratory sessions. Subjects experienced this pain stimulus once under endogenous opioid blockade with naltrexone and once in a placebo condition. Blunting was found to be negatively correlated with pain ratings, but this relationship was significantly more prominent under opioid blockade. Results for coping behaviors subjects used to manage the experimental pain were generally consistent with the Blunting results, indicating that cognitive coping was related more strongly to decreased pain ratings and cardiovascular stress responsiveness under opioid blockade. Overall, the beneficial effects of Blunting and cognitive coping on pain responses did not depend upon endogenous opioids and, in fact, became stronger when opioid receptors were blocked. The relationship between endogenous opioids and coping appears to be dependent upon situational and stimulus characteristics.

Cardiorespiratory capacity of individuals with mental retardation including Down syndrome.

This study evaluated the cardiorespiratory capacity of persons with MR with and without Down syndrome. Analyses of individual data records of maximal exercise tests with metabolic analyses were conducted on tests of 111 subjects (31 men and 16 women with DS; 35 men and 29 women without DS) from six participating centers. All centers used a walking treadmill protocol previously shown to produce valid and reliable maximal tests with this population. Peak oxygen uptake and peak minute ventilation were higher in men than in women (P < 0.006), and in subjects without DS (P < 0.006). Peak heart rate was also higher in subjects without DS (P < 0.006). Peak respiratory exchange ratio (RER) was higher in subjects without DS (P < 0.006). Using peak RER as a covariate did not change the results. An analysis of peak minute ventilation, heart rate and VO2 of subjects with a peak RER above 1.1 revealed the same results. These data show that individuals with mental retardation have low levels of peak VO2, consistent with low levels of cardiovascular fitness. Individuals with Down syndrome have even lower levels of peak VO2 than their peers without Down syndrome, a finding that is possibly mitigated by the lower peak heart rates of the individuals with Down syndrome.

The psychobiology of hostility: possible endogenous opioid mechanisms.

This study examined the role of endogenous opioids in the relation between hostility and cardiovascular stress responsiveness. Forty-six men completed the Cook-Medley Hostility Scale and experienced a laboratory pain stressor once under opioid blockade and once under placebo. Hostility scores were significantly related to the magnitude of change in cardiovascular reactivity/recovery resulting from opioid blockade. Low scorers on the Cynicism subscale displayed increases in heart rate (HR) reactivity under blockade relative to placebo, with reactivity decreases noted in high scorers. Low Hostile Affect scores were similarly associated with impaired diastolic blood pressure recovery under opioid blockade. HR recovery results were somewhat different, with high scorers on Aggressive Responding and the total Cook-Medley displaying improved HR recovery under opioid blockade, with no change noted in low scorers. These data provide preliminary support for the hypothesis that low hostile individuals rely on endogenous opioids for buffering cardiovascular stress responsiveness, but high hostiles do not.

Effects of videotaped violence on hypermnesia for imaginally encoded concrete and abstract words.

To assess whether increased arousal would differentially affect hypermnesia (enhanced recall) for imaginally encoded concrete and abstract words, two sets of materials (a violent videotape for high arousal and a bird-nest-building videotape for low arousal) were interpolated at four different points in a memory experiment. A pilot experiment measuring the change in heart rate before and after the viewing of two sets of materials confirmed the relationship between self-reported arousal and physiological state. Evidence suggests that only when arousing materials are experienced during the retention interval will hypermnesia be inhibited. In all conditions, concrete words were recalled at twice or more the rate of abstract words.

Glycemic response to stress is altered in euglycemic Pima Indians.

The aim of this work was to study the effects of a computer-driven mental arithmetic task on blood glucose in a group of four male and four female euglycemic Caucasians and a group of seven male and six female euglycemic Pima Indians. Approximately 60% of euglycemic Pima Indian Native Americans eventually develop type 2 diabetes, while only 5% of Caucasians develop the disease. All subjects had normal glucose tolerance. Subjects were given a standard breakfast; 2 h later, they were given a computerized mental arithmetic stress test for 10 min. Before, during and after the test, several variables were analyzed, including serum concentrations of glucose, insulin, glucagon and plasma cortisol and catecholamines. Heart rate, systolic and diastolic blood pressure and all the stress hormones increased during stress and decreased during recovery in all subjects. Blood glucose consistently declined one hour after the meal in all subjects. However, while it continued to decline following stress in seven out of eight Caucasian subjects, it consistently increased during and following stress in 10 out of 13 Pima Indians. Fasting serum glucose in Pima Indians and Caucasians was respectively 5.07 + 0.08 mM and 5.04 + 0.09 mM. Two-hour post-prandial values were 5.63 + 0.22 mM and 5.48 + 0.19 mM respectively, whereas post-stress values were 6.15 + 0.19 mM for Pima Indians and 5.22 + 0.20 mM for Caucasians. Both serum glucose means following stress (t = 3.1, P < 0.005) and the direction of change in serum glucose in response to mental arithmetic (chi 2 = 8.2, P < 0.01) clearly differentiated Pimas from Caucasians.(ABSTRACT TRUNCATED AT 250 WORDS)

An unusual reaction to opioid blockade with naltrexone in a case of post-traumatic stress disorder.

An unusual behavioral and cardiovascular reaction was observed during opioid blockade with naltrexone in a 32-year-old male who met DSM III-R criteria for post-traumatic stress disorder (PTSD). As part of an ongoing placebo-controlled investigation of the effects of naltrexone on laboratory and ambulatory blood pressure reactivity, this participant reported experiencing feelings of rage, explosive behavior, and other unpleasant symptoms. When compared to all other subjects (N = 24), this individual showed significantly greater effects of naltrexone on blood pressure reactivity during the laboratory stressor. His ambulatory blood pressures, when compared to placebo, were significantly increased during the 24-hr period following naltrexone. The unusual behavioral and cardiovascular responses following ingestion of naltrexone suggest an important role for endogenous opioids in adjustment to stress in this case of PTSD.

Coping styles, opioid blockade, and cardiovascular response to stress.

We investigated the hypothesis that the effects of Monitoring and Blunting coping styles are mediated in part by endogenous opioids. Mean arterial pressure (MAP) and heart rate (HR) were measured in 39 males before, during, and after a mental arithmetic stressor. Each subject experienced the protocol once under opioid blockade (naltrexone) and once in a placebo condition, in counterbalanced order. Monitoring and Blunting were assessed using the Miller Behavioral Style Scale. High Blunting and high Monitoring were both associated with poorer MAP recovery under opioid blockade than in the placebo condition. Similar effects were noted for Blunting on the measure of HR. These results indicate that the coping styles of Monitoring and Blunting may be associated with enhanced opioid mediation of cardiovascular recovery from stress.

Stress and endogenous opioids: behavioral and circulatory interactions.

Endogenous opioid peptides are the basis of a diverse system of complex neuroregulatory and endocrine mechanisms. While relatively quiescent in the resting state, these peptides are released during intense stimulation and modify, in a number of ways, circulatory homeostatic mechanisms. The endogenous opioids, primarily via endorphins and enkephalins, are capable of influencing circulatory responses to stress at the behavioral, the endocrinological, and the neural level. Recent research in humans and animals has described several roles for opioids in regulation of the circulatory stress response, and has also provided clues about the significance of opioid dysregulation in the pathophysiology of stress. Increased understanding of the basic mechanisms of stress and endogenous opioids will clarify the potential roles of opioids in important pharmacologic and behaviorally based therapeutics.