Simple mathematical models of high energy ion beam assisted deposition concentration profiles in binary thin films.

Mathematical models of composed high energy ion beam assisted deposition (IBAD) concentration profiles of implanted component in binary thin films are described. Yields of the backscattered ions and sputtering of the deposited component are considered. A Gaussian probability density is assumed to apply to the ion range distribution. The construction of concentration profiles of various shapes is considered. These profiles should of course be constructed based on continuous changes of the process parameters, but certain technical problems can arise with this continuous parameter changes. Therefore, it has been assumed that the changes to the process parameters are discrete and proceed in several steps. The resulting mathematical models are combinations of error functions. Mathematical models can be used as regression functions for the determination of some parameters, e.g., the sputtering yield. Based on the mathematical model the gradient concentration profile of nitrogen in the SiNx film was experimentally produced by the IBAD method, measured by Rutherford backscattering spectroscopy and compared with the mathematical model.

Factors that influence adherence to exercise and their effectiveness: application to cystic fibrosis.

Appropriate, regular exercise is of benefit to patients with cystic fibrosis (CF). As with other segments of the population, it has been difficult to devise exercise programs to which most patients will adhere for long periods of time. In healthy children, factors that are related to positive exercise compliance include social support, perceptions of competency and self-esteem, enjoyment of activity, and availability of a variety of activities. In patients with CF, complications associated with the disease, e.g., time required for other treatment and fatigue, make compliance with recommended exercise activities more difficult. Factors likely to increase compliance in this population include explicit and continued encouragement and support from the family and healthcare team, and the introduction of behavior-changing strategies.

How much activity do youth get? A quantitative review of heart-rate measured activity.

OBJECTIVE: Recommendations for adult physical activity have shifted from 20 to 60 minutes of continuous vigorous activity 3 to 5 times a week to accumulation of 30 minutes of moderate to vigorous physical activity most days of the week. Variations of these guidelines also have been suggested for children, based on the idea of accumulating moderate to vigorous physical activity throughout the day, rather than attaining vigorous physical activity in continuous blocks. The goal of this study was to assess accumulated amounts of physical activity at different intensities in children. METHODS: We reviewed 26 studies (n = 1883) in youth aged 3 to 17 years that used heart-rate recording to measure physical activity in children to determine accumulated daily activity. Included were studies that provided time being active for at least 2 heart rate intensities at or above 120 beats/minute. Descriptive characteristics of the study groups were determined, and the influence of age, gender, and hours and days of observation on the slope of activity time as a function of percentage of heart rate reserve (HRR) was determined using hierarchical linear regression. RESULTS: Youth attained 128.0 +/- 45.6, 47.1 +/- 14.9, 29.3 +/- 13.7, and 14.7 +/- 6.0 minutes/day between 20% to 40%, 40% to 50%, 50% to 60%, and greater than 60% HRR, respectively. Age was a significant predictor of the intercept and slope of the physical activity and %HRR relationship. CONCLUSION: Youth of all ages attain >60 minutes/day of low-intensity physical activity and approximately 30 minutes/day of activity at traditional cardiovascular fitness training levels of 50% or more of HRR. Recommendations for youth activity are discussed.

Relief of central airways obstruction following spinal release in a patient with idiopathic scoliosis.

SUMMARY. Patients with idiopathic scoliosis are reported to have a restrictive pattern on pulmonary function tests. A case is presented of a teenage girl with juvenile idiopathic scoliosis who had evidence of airways obstruction in addition to restriction on pulmonary function tests (PFT). Examination of flow-volume loops suggested central airways obstruction. At the time of induction of anesthesia for the initial spinal release surgery, a double-lumen endotracheal tube could not be passed, despite fiberoptic visualization, because of extreme deviation of the left main-stem bronchus. Postoperatively, PFT demonstrated improved flows at high lung volumes and normalization of the shape of the flow volume loop. We suggest that preoperative PFT may be used to predict which patients have central airways obstruction. This may lessen unanticipated problems with intubation at the time of surgery and may identify patients who may expect immediate improvement in lung function after scoliosis repair.

The effects of whole-body restriction on task performance.

Many occupations, particularly involving maintenance operations, require individuals to perform both physical tasks and mental tasks in restricted spaces. Researchers have examined physical task performance under various restrictions; however, little research has investigated the effects of restricted space on cognitive tasks. Cognitive task performance in restricted spaces presents cognitive demands (i.e. the task itself) as well as additional physical demands (e.g. awkward postures), which may adversely affect task performance or operator workload. This research focused on the effects of whole-body restrictions on cognitive task performance. An experiment was conducted that examined 9 levels of restriction created in a laboratory: an unrestricted control, 6 single whole-body restrictions at two severity levels (2 lateral, 2 sagittal and 2 vertical) and 2 multiple restrictions (sagittal/vertical, lateral/sagittal/vertical). An inspection task served as the cognitive task. Behavioural, physiological and psychophysical measures were collected and analysed to measure the operator and performance effects. Operator response differences were found among the various forms of restriction as well as the severity level of similar forms of restriction. Increasing restriction significantly affected the behavioural and physiological operator response as opposed to the cognitive response.

Sliding properties of plasma assisted CVD CNchi coatings for metal bioimplants.

Coatings of CNchi, have been prepared on the substrates of material Ti6Al4V, of which the human joint replacements are made. The deposition of the CNchi coating was carried out by PACVD method in apparatus with standard arrangement. The methane and nitrogen have been used as precursors for CNchi compound. The infrared absorption spectroscopy and Rutherford backscattering spectroscopy were applied on diagnostics of prepared CNchi layer. Beside carbon and nitrogen the hydrogen and oxygen were found in the coatings. The sliding tests were carried out with the samples. The counter parts were the cylinders made of the polyethylene of the same type as for big joint prostheses is used. The tests were carried out in the medium of physiological solution. The CNchi coatings perform well under the lower load of 25 and 50 N. When the load is increased to 100 N, the friction coefficient slowly increases, but measured values of mu are typical for boundary lubrication.

Asthma and maternal body mass index are related to pediatric body mass index and obesity: results from the Third National Health and Nutrition Examination Survey.

OBJECTIVE: Clinical research has shown an increased prevalence of obesity in children with asthma. This study was designed to assess the relationship between asthma and pediatric body mass index (BMI) in a national database and to examine factors that may modify this relationship. DESIGN: The cross-sectional relationship between asthma and pediatric BMI and obesity (BMI > or = 85th percentile) was studied. Variables that may influence the relationship between asthma and pediatric BMI, such as race/ethnicity and television watching were included in the model for the total sample. A smaller sample of 3,009 white and African American youth were studied in regression models including maternal BMI. STUDY POPULATION: A nationally representative cross-sectional sample of 5154 children and adolescents of 6 to 16 years of age from the Third National Health And Nutrition Examination Survey. RESULTS: In the full sample, asthma and television watching were related to BMI, accounting for 3% of the variance in BMI. When maternal BMI was included in the non-Hispanic sample, television watching, maternal BMI, and the interaction of maternal BMI and asthma were related to youth BMI, accounting for 15% of the variance. The standardized BMI z-score for those youth without asthma and no maternal obesity was 0.06, which increased to 0.33 if the youth had asthma, to 0.70 if the youth did not have asthma but the mother was obese, and to 1.71 if the youth had asthma and the mother was obese. Asthma, television watching, and maternal BMI were independent predictors of youth obesity. CONCLUSIONS: BMI and prevalence of obesity is higher in youth with asthma. Pediatric BMI, but not obesity, is also related to the interaction of asthma and maternal BMI in white and African American youth. Comorbidity of asthma and obesity may complicate treatment of either condition, and prevention of obesity should be encouraged for asthmatic children.

Work and leisure time physical activity and mortality in men and women from a general population sample.

PURPOSE: The purpose of this study was to examine the long-term relationships between total physical activity and mortality from all causes and coronary heart disease (CHD) in the general population. METHODS: A prospective design was used, following participants for 29 years, beginning in 1960. The study population consisted of a randomly selected sample of white male (n = 698) and female (n = 763) residents of Buffalo, New York with a 79.0% participation rate and follow-up rates of 96.0% and 90.2% in males and females, respectively. At baseline, comprehensive information was obtained regarding participants' usual physical activity at work and during leisure time. RESULTS: As of December 31, 1989, three hundred and two (43.3%) men and 276 (41.0%) women died, 109 (15.6%) and 81 (10.6%) from CHD, respectively. In men, a significant interaction was found between activity and body mass index (BMI) for both outcomes. In women, a significant activity by age interaction was observed. In non-obese men (BMI<27.02), activity was inversely associated with all-cause [relative risk (RR) = 0.59; 95% confidence interval (CI), 0.39-0.89] and CHD mortality (RR = 0.39; 95% CI, 0.18-0.83), independent from the effects of age and education. No such associations were found in obese men and increased risks could not be ruled out. Among women, younger participants (age <60 years) had a significantly reduced risk of CHD death with increased activity (RR = 0.26; 95% CI, 0.07-0.99). No other significant associations were observed. CONCLUSIONS: Physical activity favorably influences mortality risks in non-obese men and younger women. Gender-specific factors should be considered for potential effect modification.

Providing sedentary adults with choices for meeting their walking goals.

BACKGROUND: This study was designed to test different ways of meeting the new ACSM/CDC recommendations for physical activity stating that all Americans at least 2 years of age should obtain 30 minutes of moderate intensity activity on most days of the week. METHODS: Thirty-two sedentary 18- to 55-year-old adults were randomly assigned to three groups of brisk walking/6 days per week: 30 continuous minutes, three 10-minute bouts, and 30 minutes in any combination of bouts as long as each bout was at least 5 minutes. Aerobic fitness, blood pressure, body composition, and physical activity were assessed at baseline, at end of program (16 weeks), and at follow-up (32 weeks). RESULTS: All groups significantly (P

The relationship between asthma and obesity in urban minority children and adolescents.

OBJECTIVE: To investigate the relationship between asthma and obesity in children and adolescents. DESIGN: Medical record review. SETTING: Urban community health center. PARTICIPANTS: One hundred seventy-one children aged 4 to 16 years, 85 with asthma and 86 nonasthmatic controls. MAIN OUTCOME MEASURES: Diagnosis of asthma, age, and sex-adjusted body mass index (weight in kilograms divided by the square of the height in meters). RESULTS: Seventy-eight percent of the sample was Hispanic, 17% was African American, 2% were white, and 3% were other minorities. There were significantly more children with asthma (30.6%) who were very obese (> or =95th body mass index percentile) compared with controls (11.6%) (P=.004). Children with asthma were also significantly more overweight than controls (mean+/-SD, 22.5%+/-28.3% vs 12.0%+/-19.6% overweight; P=.004). The difference in obesity between children with asthma and controls was significant for both sexes and across the 4.5 to 10.9 years and 11 to 16 years age groups. Asthma severity was not related to obesity. CONCLUSION: Asthma is a risk factor for obesity in children and adolescents.

Abdominal motor unit activity during respiratory and nonrespiratory tasks.

Abdominal muscles serve multiple roles, but the functional organization of their motoneurons remains unclear. To gain insight, we recorded single motor unit potentials from the internal oblique (IO) and transversus abdominis (TA) muscles of three standing subjects during quiet breathing, a leg lift, and an expiratory threshold load. Inspiratory airflow, recorded from a pneumotachometer, provided tidal volumes and respiratory cycle timing. Fine wires, implanted under ultrasonic imaging, detected single motor unit potentials that were visually distinguished by their spike morphology. From the number of spikes, firing profiles, times of occurrence in the respiratory cycle, and their onset, instantaneous, mean, and peak firing frequencies we deduced that 1) breathing patterns varied across tasks, 2) different motor units were recruited for each task with essentially no overlap, 3) their firing displayed prominent expiratory activity during each task, and 4) the recruitment levels and discharge patterns of IO and TA were different. We conclude that the IO and TA motor pools receive a strong central respiratory drive, yet each pool receives its own distinct, task-dependent synaptic input.

Effects of varied vocal intensity on ventilation and energy expenditure in women and men.

This study was completed to determine how ventilatory responses change by means of speech reading at three different sound pressure levels (SPL) as compared to quiet breathing prior to each task. The energy required to alter SPL was also studied and compared to energy expenditures during a quiet breathing condition. Twenty-four adults (12 women, 12 men) were studied while reading a standard passage at low, comfortable, and high SPLs for 7 minutes with quiet breathing periods between each task to achieve respiratory steady state and serve as a control to which the reading tasks were compared. The last 2 minutes of exhaled air for all speaking and quiet breathing tasks were collected using a Hans Rudolph mouth breathing face mask. A Sensor Medics Vmax 29 series diagnostic instrument system measured all ventilatory responses and energy expenditures. Volume and timing alterations in ventilation were characterized by measuring tidal volume (V[T]), inspiratory time (T[I]), inspiratory flow rate (V[T]/T[I]), and expiratory time (T[E]). Average ventilation, energy expenditure, and adequacy of ventilation were measured using minute ventilation (V[E]), oxygen consumption (VO2), carbon dioxide production (VCO2), and partial pressure of end-tidal carbon dioxide (end-tidal PET[CO2]). Results indicated volume, timing, ventilation, and energy expenditure values remained closest to quiet breathing values for the comfortable SPL. Volume, ventilation, and energy expenditure were significantly greater for the high SPL and lower for the low SPL, compared to the baseline steady state, indicating that the low SPL causes a ventilatory deficit that was found to be paid back at the end of the speech task during the quiet breathing period. These results demonstrate that an individual's comfortable SPL is the least energy-requiring way to speech breathe. As SPL rises above or below comfortable SPL, speech breathing requires more energy.

Contractility of the ventilatory pump muscles.

The ventilatory muscles are striated skeletal muscles, and their in situ function is governed by the same relationships that determine the contractile force of muscles in vitro. The ventilatory muscles, however, are functionally distinct from limb skeletal muscles in several aspects, the most notable being that the ventilatory muscles are the only skeletal muscles upon which life depends. Among the muscles that participate in ventilation, the diaphragm is closest to its optimal resting length at functional residual capacity (FRC) and has the greatest capacity for shortening and volume displacement, making it the primary muscle of inspiration. All inspiratory muscles shorten when the lung is inflated above FRC, but interactions among the various inspiratory muscles make for a wider range of high force output than could be achieved by any one muscle group acting in isolation. The velocity of inspiratory muscle shortening, especially diaphragmatic shortening, causes maximal dynamic inspiratory pressures to be substantially lower than maximal static pressures. This effect is especially pronounced during maximal voluntary ventilation, maximal exercise, and maximal inspiratory flow, volume maneuvers over the full vital capacity. During quiet breathing, the ventilatory muscles operate well below the limits of their neural activation and contractile performance. During intense activity, however, the diaphragmatic excursion approaches its limits over the entire vital capacity, and respiratory pressures may near their dynamic maximum. Because the system may operate near its available capacities during increased ventilatory demands, multiple strategies are available to compensate for deficits. For example, if the diaphragm is acutely shortened, it can still generate the required respiratory pressure if it receives more neural drive. Alternatively, other muscles can be recruited to take over for an impaired diaphragm. Thus, the whole system is highly versatile.

Alterations in intramuscular connective tissue after limb casting affect contraction-induced muscle injury.

This study examined the effect of alterations in rat intramuscular connective tissue (CT), secondary to limb immobilization, on the muscle's susceptibility to contraction-induced injury. Hindlimbs were casted for 3 wk with the extensor digitorum longus muscle fixed in a shortened (IM-SP) or lengthened position (IM-LP). An age-matched control group remained uncasted. Extensor digitorum longus muscles were injured in vivo by using a motorized foot pedal that repeatedly flexed and extended the foot while the muscle was electrically stimulated during plantar flexion. Four hours postinjury, maximum isometric tetanic force (Po) was measured in vitro and was used as a functional index of muscle injury. Muscles were fixed, sectioned, and stained for later analysis. Intramuscular CT concentration, expressed as the ratio of CT area to muscle fiber area, was significantly higher in both IM-SP (0.153 +/- 0.003) and IM-LP (0.174 +/- 0.003) groups compared with controls (0.104 +/- 0.003). Po values of injured muscles both IM-LP and IM-SP were higher than the injured controls' Po of 9.41 +/- 0.63 N/cm2 (P < 0.05). Injured IM-LP muscle forces were significantly higher than those of IM-SP. This study demonstrated that limb immobilization increases intramuscular CT concentration, which is accompanied by attenuation of muscle injury. We conclude that remodeling of intramuscular CT affects the muscle's resistance to contraction-induced injury.

Control of breathing patterns and abdominal muscles during graded loads and tilt.

Tilting from supine to upright purportedly enhances both segmental and pulmonary proprioceptive feedback, whereas an expiratory threshold load (ETL) preferentially enhances pulmonary feedback. To test this we studied 13 adults when supine and 60 degrees and 90 degrees head up. We measured tidal volume, inspiratory duration (TI), and expiratory duration (TE) from flow; estimated end-expiratory lung volume from inspiratory capacity; and determined burst amplitudes and durations from abdominal electromyograms (EMGs). ETLs were incremented from 0 (control) to 25 cmH2O in 5-cmH2O steps. Tidal volume was significantly increased by ETL but was unaffected by body position. Every load prolonged TE, whereas TI remained unchanged. When subjects were supine, abdominal EMGs were silent but became tonically active when subjects were upright. During ETL, abdominal activity became rhythmical and phase locked to expiration. Bursts amplitudes were enhanced with each increment in ETL, but burst durations did not change even though TE was prolonged. The altered breathing pattern and active expiration augmented inspiratory flow and decreased end-tidal PCO2. Responses were greatest when subjects were 90 degrees head up. The load-related increments in abdominal recruitment, with no change in burst durations, fit the concept of two central pattern generators: one controlling pattern and the other controlling rhythm of the central respiratory drive.

Respiratory and abdominal muscle responses to expiratory threshold loading in cystic fibrosis.

We hypothesized that the hyperinflation and pulmonary dysfunction of cystic fibrosis (CF) would distort feedback and therefore alter the abdominal muscle response to graded expiratory threshold loads (ETLs). We compared the respiratory and abdominal muscle responses with graded ETLs of seven CF patients with severe lung dysfunction with those of matched healthy control subjects in the supine and 60 degrees head-up positions. Breathing frequency, tidal volume, and ventilatory timing were determined from inspiratory flow recordings. Abdominal electromyograms (EMGs) were detected with surface electrodes placed unilaterally over the external and internal oblique and the rectus abdominis muscles. Thresholds, times of onset, and durations of phasic abdominal activity were determined from raw EMGs; peak amplitudes were determined from integrated EMGs. Graded ETLs were imposed by submerging a tube from the expiratory port of the breathing valve into a column of water at depths of 0-25 cmH2O. We found that breathing frequency, tidal volume, and expired minute ventilation were higher in CF patients than in control subjects during low ETLs; a change in body position did not alter these ventilatory responses in the CF patients but did in the control subjects. All CF patients, but none of the control subjects, had tonic abdominal activity while supine. CF patients recruited abdominal muscles at lower loads, earlier in the respiratory cycle, and to a higher recruitment level in both positions than the control subjects, but burst duration of phasic activity was not different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

An organizational model of sports medicine facilities in the United States.

Information on establishing the organizational structure of sports medicine clinics is useful to clinicians intending to start or expand a clinic. The purpose of this study was to identify an organizational model of existing sports medicine facilities in terms of: 1) administration and management, 2) staff qualifications and professional development, 3) location of facility, 4) range of services, 5) availability of services, 6) physician referral base, and 7) fee structure. A survey of 250 sports medicine clinics located in or near urban cities across the United States was conducted by mail. Results of this study indicate that the typical sports medicine facility is corporate-owned. A physical therapist and/or a physician establishes policy, and the physical therapist directs day-to-day operations. On average, the professional staff have four years of athletic team affiliation and seven years of clinical experience with athletes. The staff have attended less than an average of one continuing education course a year over the last five years. The typical facility is located within five miles of a major city, within 10 miles of its primary referral source and competition, and within 10 miles of its clients' homes. Most facilities employ combinations of full-time and part-time physicians, physical therapists, and athletic trainers. The typical sports medicine facility is open 12 hours each weekday. The physician referral base is composed primarily of orthopaedic and family practice physicians who refer an average of 14 new patients a week. J Orthop Sports Phys Ther 1992;15(2):80-86.

Attenuation of contraction-induced skeletal muscle injury by bromelain.

The proteolytic enzyme, bromelain, reportedly has therapeutic effects in the treatment of inflammation and soft tissue injuries. We tested the hypothesis that bromelain attenuates skeletal muscle injury induced by lengthening contractions. The left extensor digitorum longus (EDL) muscle of anesthetized hamsters was injured using a motorized foot pedal which repeatedly flexed/extended the foot through a range of 125 degrees. The EDL muscle was electrically stimulated for 400 ms during plantarflexion. Animals were assigned randomly to either a 0-d group (evaluated 3-h post-injury) or to untreated (UT) or bromelain-treated (T) groups, evaluated 3, 7, or 14 d post-injury. Following injury, T received 5 mg.kg-1 b.w. of bromelain, twice daily. Maximum isometric tetanic force (Po) was measured in vitro, then muscles were fixed, sectioned, and examined for evidence of fiber damage. The Po of injured muscles from T were higher than Po of injured muscles from UT at 3 (18.7 +/- 0.4 vs 16.5 +/- N.cm-2 and 14 d (20.5 +/- 0.6 vs 18.2 +/- 0.6 N.cm-2) (P less than 0.05), but not 7 d (19.5 +/-0.7 vs 17.7 +/- 0.8 N.cm-2). The Po of UT injured muscles were significantly lower than Po of contralateral control muscles at all time periods. Po of injured muscles from T were lower than Po from control muscles at 3 and 7 d (P less than 0.05), but not 14 d. The number of intact fibers of 3-d UT injured muscles was lower than the number of intact fibers in control muscles (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic myography as an indicator of force during sustained contractions of a small hand muscle.

To test the hypothesis that muscle sound amplitudes would remain constant during sustained submaximal isometric contractions, we recorded acoustic myograms from the abductor digiti minimi muscle in 12 subjects at 15, 25, 50, and 75% of a maximum voluntary contraction (MVC). Muscle sounds were detected with an omni-directional electret microphone encased in closed-cell foam and attached to the skin over the muscle. Acoustic amplitudes from the middle and end of the sustained contractions were compared with the amplitudes from the beginning of contractions to determine whether acoustic amplitudes varied in magnitude as force remained constant. Physiological tremor was eliminated from the acoustic signal by use of a Fourier truncation at 14 Hz. The amplitudes of the acoustic signal at a contraction intensity of 75% MVC remained constant, reflecting force production over time. At 50% MVC, the root-mean-square amplitude decreased from the beginning to the end of the contraction (P less than 0.05). Acoustic amplitudes increased over time at 15 and 25% MVC and were significantly higher at the end of the contractions than at the beginning (P less than 0.05). Alterations in the acoustic amplitude, which reflect changes in the lateral vibrations of the muscle, may be indicative of the different recruitment strategies used to maintain force during sustained isometric contractions.