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Biomedical subjects

Bo Fernhall

Publications and source records attributed to Bo Fernhall.

31 records · Page 2Linked to original sources
PubMed2004

Heart rate variability at rest and during exercise in persons with Down syndrome.

OBJECTIVES: To determine whether autonomic dysfunction explains chronotropic incompetence observed in persons with Down syndrome (DS) and to measure heart rate variability (HRV) at rest and during exercise in persons with mental retardation with and without DS. DESIGN: Comparative study. SETTING: University exercise science laboratory. PARTICIPANTS: Thirty-one subjects with mental retardation (age, 20.2 y) with DS (n=16; 10 men, 6 women) and without DS (n=15; 8 men, 7 women). INTERVENTIONS: Not applicable. Main outcome measures HRV was determined at rest and at 2 steady-state exercise intensities on the treadmill in both time (standard deviation of the R-R interval, percentage of R-R intervals deviating by more than 50 ms from the previous R-R interval [deviation >50], square root of the mean squared differences of successive differences) and frequency (low-frequency power [LF]), high-frequency power [HF], the LF/HF ratio) domains. RESULTS: The DS group demonstrated a statistically lower peak heart rate (161 beats/min vs 178 beats/min, P<.05), and peak oxygen consumption (27.4 mL.kg(-1).min(-1) vs 34.3 mL. kg(-1).min(-1), P<.05) than did the group with mental retardation without DS. At rest, all time domain measures of HRV and absolute HF power were significantly higher in the DS group (P<.05). Yet, LF power and LF/HF values did not differ between groups. All HRV variables decreased significantly at both exercise intensities, with no differences between groups during exercise (P<.05). CONCLUSIONS: People with DS have greater parasympathetic activity at rest, but group differences disappear with the onset of exercise, which suggests that other variables are responsible for chronotropic incompetence in persons with DS.

Adult↗
PubMed2004

Energy expenditure of walking and running: comparison with prediction equations.

PURPOSE: This study established the published prediction equations for the energy expenditure of walking and running compared with the measured values. To make this comparison we first determined whether differences exist in energy expenditure for 1600 m of walking versus running, and whether energy expenditure differences occur due to being on the track or treadmill. METHODS: Energy was measured via indirect calorimetry in 24 subjects while walking (1.41 m.s(-1)) and running (2.82 m.s(-1)) 1600 m on the treadmill. A subgroup also performed the 1600-m run/walk on the track. The measured energy expenditures were compared with published prediction equations. RESULTS: Running required more energy (P < 0.01) for 1600 m than walking (treadmill: running 481 +/- 20.0 kJ, walking 340 +/- 14 kJ; track: running 480 +/- 23 kJ, walking 334 +/- 14 kJ) on both the track and treadmill. Predictions using the ACSM or Leger equations for running, and the Pandolf equation for walking, were similar to the actual energy expenditures for running and walking (total error: ACSM: -20 and 14.4 kJ, respectively; Legers walking: -10.1 kJ; Pandolf walking: -10.0 kJ). An overestimation (P < 0.01) for 1600 m was found with the McArdle's table for walking and running energy expenditure and with van der Walt's prediction for walking energy expenditure, whereas the Epstein equation underestimated running energy expenditure (P < 0.01). CONCLUSION: Running has a greater energy cost than walking on both the track and treadmill. For running, the Leger equation and ACSM prediction model appear to be the most suitable for the prediction of running energy expenditure. The ACSM and Pandolf prediction equation also closely predict walking energy expenditure, whereas the McArdle's table or the equations by Epstein and van der Walt were not as strong predictors of energy expenditure.

Adolescent↗
PubMed2003

Attenuated responses to sympathoexcitation in individuals with Down syndrome.

This study evaluated blood pressure and heart rate responses to exercise and nonexercise tasks as indexes of autonomic function in subjects with and without Down syndrome (DS). Twenty-four subjects (12 with and 12 without DS) completed maximal treadmill exercise, isometric handgrip (30% of maximum), and cold pressor tests, with heart rate and blood pressure measurements. Maximal heart rate and heart rate and blood pressure responses to the isometric handgrip and cold pressor tests were reduced in subjects with DS (P < 0.05). Both early (first 30 s) and late (last 30 s) responses were reduced. Obesity did not appear to influence the results, as both obese and normal-weight subjects with DS exhibited similar responses, and controlling for body mass index did not alter the results between controls and subjects with DS. Individuals with DS, without congenital heart disease, exhibit reduced heart rate and blood pressure responses to isometric handgrip exercise and cold pressor testing, consistent with autonomic dysfunction. Autonomic dysfunction may partially explain chronotropic incompetence observed during maximal treadmill exercise in individuals with DS.

Adolescent↗
PubMed2003

Effects of exercise on vasodilatory capacity in endurance- and resistance-trained men.

To determine vasodilatory responsiveness we measured forearm blood flow (FBF) following reactive hyperemia (RH), prior to and following a bout of maximal aerobic exercise in endurance- (n=14) and resistance-trained men (n=10). Both groups were similar in height, body mass, and percentage body fat. Using strain-gauge plethysmography, resting FBF was higher in the resistance-trained group [4.82 (0.84) vs 3.33 (1.17) ml min(-1) 100 ml(-1) of tissue; P<0.05]. However, the resistance-trained group had a 17%-29% lower pre-exercise FBF response to RH for the first 45 s (P<0.05). Following the maximal exercise bout there were no group differences in FBF. Post-exercise FBF was higher compared to pre-exercise values in both the endurance- (P<0.001) and resistance- (P<0.01) trained groups. Endurance-trained men appear to have a greater peak vasodilatory capacity compared to resistance-trained men, and acute maximal exercise increased the vasodilatory capacity in both groups. Acute exercise also equalized the peak vasodilatory response between the endurance- and resistance-trained groups, suggesting the potential for flow-mediated vasodilatation was similar for both groups.

Adolescent↗
PubMed2003

Effect of a one-year combined exercise training program on body composition in men with coronary artery disease.

Increased fat mass, particularly abdominal fat mass, is associated with poor metabolic profiles and an increase in cardiovascular risk factors. The purpose of this study was to evaluate the effect of a 1-year combined aerobic and strength training regimen, compared to aerobic training only, on body composition in patients with coronary artery disease (CAD). Thirty-six males with CAD were assigned to 3 groups: 13 to weight training plus aerobic training (combined training group [CT]), 13 to aerobic training only (aerobic training group [AT]), and 10 to a control group (no exercise [CG]). Body composition was determined by dual-energy x-ray absorptiometry (DEXA). Differences were observed between groups at the end of the study, controlling for prevalues. The total and trunk percent fat mass (%FM) were lower in CT compared with AT and CG (P<.05). The total %FM in AT was significantly (P<.05) lower than in CG, but the %FM of the trunk did not differ between the 2 groups. Fat-free mass (FFM) was significantly higher in CT than in AT and CG (P<.05). The results suggest that a long-term CT program is more effective than an AT program alone in producing changes in body composition. The percentage changes in total and trunk fat mass were higher in CT (-11% and -12%, respectively) than in AT (-2.4% and -0.7%, respectively). Future studies need to investigate the specific health effects of trunkal fat mass loss in patients with CAD.

Adipose Tissue↗
PubMed2003

Chronotropic incompetence in persons with down syndrome.

OBJECTIVE: To investigate the chronotropic response to exercise through peak heart rate and the Chronotropic Response Index (CRI) in participants with Down syndrome (DS) and in nondisabled control participants. DESIGN: Comparative study describing the acute exercise heart rate response. SETTING: University sports medicine facility. PARTICIPANTS: Twenty participants with DS (mean age +/- standard deviation, 24.2+/-3.5y) and 20 control participants without disabilities (age, 21.2+/-2.8y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Maximal treadmill exercise tests with metabolic and heart rate measurements. Maximal heart rate and the CRI were considered main outcomes. RESULTS: The peak oxygen consumption (41.7 vs 31.8mL. kg(-1).min(-1)) and peak heart rate (165+/-14.7 vs 192+/-7.7 beats/min) were significantly lower in participants with DS than in controls (P<.05). The CRI was below normal (.84+/-.25) in participants with DS and was normal (.97+/-.07) in controls. CONCLUSION: Both the CRI and the peak heart rates were indicative of chronotropic incompetence in participants with DS, but not in controls. The CRI of the participants with DS was similar to that reported for nondisabled populations who have a true chronotropic response to exercise. The CRI indicated that the low peak heart rate in our participants with DS was a true chronotropic response.

Adolescent↗
PubMed2002

Effect of a 1 year combined aerobic- and weight-training exercise programme on aerobic capacity and ventilatory threshold in patients suffering from coronary artery disease.

Weight-training is recommended as a complement to conventional aerobic-training for most low to moderate risk patients suffering from coronary artery disease (CAD). The purpose of this study was to evaluate the effect of a 1 year exercise programme combining weight- and aerobic-training on peak oxygen uptake (V*O2,peak) and ventilatory threshold (VT). We studied 40 men suffering CAD who were divided into three groups: 14 subjects to weight-training plus aerobic-training [mean (SD] [combined exercise group, age 55 (10) years], 14 to aerobic-training only [aerobic-training group, age 57 (11) years], and 12 to a control group [standard care, age 57 (11) years]. A symptom-limited graded exercise test using the standard Bruce protocol was performed using a 12-lead electrocardiogram, and gas analysis techniques. Muscle strength was determined only in the combined exercise group using the one-repetition maximum method on each of eight weight exercises. Arm and leg strength increased by 21.9% and 27.8% respectively ( P<0.0001) from pre to post-tests. The V*O2,peak did not differ between the combined and aerobic-training groups but their adjusted means were greater than those of the control group [39 (1.8) and 35.3 (1.8) compared to 26.2 (2.7) ml.kg(-1).min(-1) ( P<0.001)]. The oxygen uptake at VT was higher in the combined group [24.7 (1.4) ml.kg(-1).min(-1)] compared to aerobic [18.7 (1.4) ml.kg(-1).min(-1)] and control [13.6 (1.7) ml.kg(-1)min(-1)] groups ( P<0.001). Similar results were found for exercise tolerance (treadmill time to peak and at VT). Combined exercise training increased the VT more than aerobic-training alone. Combined exercise training did not improve the V*O2,peak or the functional capacity more than aerobic-training alone.

Adaptation, Physiological↗
PubMed2002

Physical activity, metabolic issues, and assessment.

Considering the important health consequences of physical activity and aerobic capacity, current guidelines recommend that all individuals should be physically active all or most days of the week. Relatively little is known about physical activity patterns or aerobic capacity of individuals who have disabilities, but existing data clearly show a disturbing pattern of low levels of physical activity and aerobic capacity in most, if not all, populations who have disabilities. More research is needed on all populations who have disabilities, not only documenting current levels of physical activity and aerobic capacity but also investigating potential strategies for improvement. Unfortunately, the techniques available for measuring physical activity have significant shortcomings. DLW shows considerable promise, but it is expensive and not appropriate for population studies. All other techniques have significant shortcomings in regard to tracking individual physical activity patterns, but they might provide valuable insight regarding group behavior. Although maximal exercise testing is the gold standard for measuring aerobic capacity, this technique is difficult to use in many populations that have disabilities. Few protocols have been validated for use with individuals who have disabilities, and indiscriminant use of protocols developed for nondisabled populations is inappropriate when testing individuals who have disabilities. Submaximal testing could be of considerable utility, but few protocols have been validated. For most populations that have disabilities, submaximal tests designed to predict VO2peak are not valid, given the altered disability-specific physiological responses, which usually result in gross overpredictions. Submaximal tests designed to compare (either intra or inter individual comparisons) physiological responses at predetermined submaximal work rates show considerable promise. Both populations of children who have disabilities that are discussed herein exhibit low levels of physical activity and aerobic capacity, which is consistent with most of the literature for any group that has disabilities. Although the mechanisms for producing lower levels of activity and aerobic capacity differ among children who have mental retardation and children who have CP, the outcome is similar in both populations. Appropriate testing methodology differs between these populations, and the different mechanisms involved demonstrate the disability-specific nature of research in children who have disabilities, which also illustrates the difficulty of producing general guidelines for exercise and physical activity interventions. Current data clearly show the need for improving both physical activity patterns and aerobic capacity in most children who have disabilities. Failure to accomplish this goal will ultimately have considerable negative health outcomes for individuals who have disabilities.

Child↗
PubMed2002

Effects of clothing on accuracy and reliability of air displacement plethysmography.

PURPOSE: The purpose of this investigation was to quantify the effects of different attire on the accuracy and reliability of estimating percent body fat (%fat) by using air displacement plethysmography (ADP). METHODS: Fifteen adults were tested four times on four separate occasions. Each session consisted of estimating %fat with ADP wearing a swimsuit (ADP(SS)), a hospital gown (ADP(HG)), and in the nude (ADP(N)), plus assessment by hydrostatic weighing (HW). RESULTS: An ANOVA revealed no significant differences within any of the four methods over the 4 days. Intraclass correlation coefficients revealed a strong relationship for repeated measures in ADP(SS) (r = 0.981), ADP(HG) (r = 0.993), ADP(N) (r = 0.989), and HW (r = 0.976). Mean data for each condition indicated a significant underestimation (P < 0.05) of %fat while wearing a hospital gown (13.8 +/- 7.7%) compared with ADP(SS) (22.0 +/- 7.8%), ADP(N) (23.5 +/- 7.5%), and HW (22.6 +/- 6.8%). CONCLUSION: Reliability of ADP does not appear to be compromised by clothing; however, wearing a hospital gown significantly affects accuracy, reducing %fat estimations by approximately 9% compared with the recommended swimsuit. Measurement in the nude does not provide more reliable or accurate measures than wearing a swimsuit.

Adolescent↗
PubMed2002

Left ventricular response to dynamic exercise in young cyclists.

PURPOSE: The purpose of this study was to compare cardiac physiological and dimensional responses to exercise in highly trained young male cyclists (mean age 13.7 +/- 1.0 yr) with those of nontrained boys. METHODS: Ventricular systolic and diastolic dimensions were measured by two-dimensional echocardiography, and stroke volume was estimated by Doppler echocardiography during a progressive maximal upright cycle test. RESULTS: At rest, the cyclists demonstrated larger left ventricular dimensions relative to body size than the nonathletes. Maximal stroke index and cardiac index were significantly greater in the cyclists. The pattern of stroke volume response to exercise was similar in the two groups, with an early rise and then plateau to exhaustion. Left ventricular diastolic dimension increased slightly at onset of exercise and then gradually declined as workload increased in both groups. CONCLUSION: Factors responsible for the greater maximal stroke volume in young endurance athletes involve those variables that contribute to resting left ventricular diastolic filling (preload).

Adolescent↗
PubMedDate not supplied

Determinants of exercise blood pressure response in normotensive and hypertensive women: role of cardiorespiratory fitness.

PURPOSE: Exaggerated blood pressure (BP) response during physical exertion is associated with increased risk for cardiovascular events. Furthermore, it may be the predisposing factor for myocardial infarction triggered by physical exertion. The authors have shown that systolic BP achieved after 6 minutes of exercise is the strongest predictor of left ventricular hypertrophy. Furthermore, a 37 mm Hg increase in systolic BP above resting BP at 6 minutes of exercise was the threshold for left ventricular hypertrophy. The purpose of this study was to determine predictors of exercise BP response in normotensive and hypertensive women. METHODS: An exercise tolerance test (Bruce) was performed by 1411 normotensive (resting BP < 140/90 mm Hg) and hypertensive (resting BP > or = 140/90 mm Hg) women. These women were faculty, students, and staff at the University of Maryland, College Park, Maryland, and the George Washington University Medical Center, as well as patients undergoing a routine exercise tolerance test at West Coast Cardiology, Pinellas Park, Florida. Two fitness categories (low-fit and high-fit) were established on the basis of treadmill time to exhaustion adjusted for age. RESULTS: Significant associations were observed among the 6-minute exercise BP and age, body mass index, resting systolic and diastolic BP, heart rate, and exercise time to exhaustion. In a stepwise multiple-regression analysis, the determinants of BP after 6 minutes of exercise were resting systolic BP and treadmill time to exhaustion (R2 = 0.36) for normotensive women and treadmill time to exhaustion and resting systolic BP (R2 = 0.30) for hypertensive women. When fitness categories were contrasted, low-fit women in both the normotensive and hypertensive categories had higher BP and rate-pressure product after 6 minutes of exercise than the high-fit women (P <.05). CONCLUSIONS: Resting systolic BP and cardiorespiratory fitness are determinants of a submaximal exercise BP response for both hypertensive and normotensive women. Low cardiorespiratory fitness is associated with a higher BP response during submaximal exercise, suggesting that increased fitness may attenuate this abnormal rise in BP. Thus, low- to moderate-intensity physical activities for most days of the week should be encouraged for all women to increase cardiorespiratory fitness. This is likely to attenuate an abnormal rise in systolic BP that may occur during routine daily activities and protect against the associated health consequences.

Adult↗
PubMedDate not supplied

Exaggerated blood pressure response to exercise is associated with inflammatory markers.

PURPOSE: An exaggerated blood pressure (EBP) response to exercise has been shown to be a predictor of future hypertension and risk of cardiovascular mortality. Although EBP is associated with endothelial dysfunction and increased left ventricular hypertrophy, the underlying mechanisms are not fully understood. Inflammatory markers, C-reactive protein (CRP) and white blood cells (WBCs), were predictive of future hypertension. The objective of this study was to examine the hypothesis that increasing levels of CRP and WBCs would be related to an EBP response during exercise. METHODS: Inflammatory markers were compared in 43 males with an EBP (systolic blood pressure [SBP] >or=210 mm Hg) response during maximal treadmill testing to an age and resting SBP-matched group of 42 males with a normal blood pressure response to exercise. RESULTS: There were significant group differences in maximal SBP and diastolic blood pressure (DBP), exercise induced increases in SBP and DBP (P <.01), and WBCs (P <.01), but CRP did not differ between groups (P =.39). White blood cells were significantly associated with maximal SBP (r = 0.31), and the exercise-induced increase in SBP (r = 0.34). However, CRP did not correlate with the maximal blood pressure response to exercise (r = 0.11, P =.33). In a stepwise multiple regression analysis, WBC was independently associated with the exercise-induced increase in SBP (beta = 0.256, P =.011). CONCLUSIONS: These results suggest that inflammation may be associated with an EBP response during exercise testing.

Biomarkers↗