Aerobic fitness and obesity: relationship to cerebral white matter integrity in the brain of active and sedentary older adults.

OBJECTIVE: Aerobic fitness (VO(2) peak) and obesity risk (OR) may impact brain health. This study examined hemispheric and segment specific relationships between VO(2) peak, OR and cerebral white-matter (CWM) integrity in the cingulum brain region in healthy older adults. METHODS: Fifteen subjects (66±6 years) completed VO(2) peak testing and MRI of the brain. OR was determined via body mass index (BMI) and abdominal girth. MRI analysis was performed with a structural 3D T1 MP-Rage and diffusion tensor imaging technique (DTI, 21 directions, repeated four times) on a 3.0 T MR imaging unit. CWM integrity indices, fractional anisotropy (FA) and mean diffusivity (MD), were computed from the tensors. The anterior, middle and posterior cingulum segments were analysed on both sides of the brain. Partial correlations (age and gender controlled) and standard multiple regressions were used to determine significant associations and unique contributions to CWM integrity. RESULTS: VO(2) peak was moderately related to FA in the left middle cingulum segment (r partial=0.573, p=0.041) and explained 28.5% of FA's total variance (p=0.10). Abdominal girth (r partial=-0.764, p=0.002) and BMI (r partial=-0.690, p=0.009) were inversely related to FA in the right posterior cingulum (RPC) segment. Abdominal girth and BMI uniquely explained 53.9% of FA's total variance (p=0.012) and 43.9% (p=0.040), respectively, in the RPC. CONCLUSION: Higher aerobic fitness and lower obesity risk are related to greater CWM integrity but not in the same cingulum segments.

The effect of exercise on the cerebral vasculature of healthy aged subjects as visualized by MR angiography.

BACKGROUND AND PURPOSE: Prior studies suggest that aerobic exercise may reduce both the brain atrophy and the decline in fractional anisotropy observed with advancing age. It is reasonable to hypothesize that exercise-induced changes to the vasculature may underlie these anatomic differences. The purpose of this blinded study was to compare high-activity and low-activity healthy elderly volunteers for differences in the cerebrovasculature as calculated from vessels extracted from noninvasive MR angiograms (MRAs). MATERIALS AND METHODS: Fourteen healthy elderly subjects underwent MRA. Seven subjects reported a high level of aerobic activity (64 +/- 5 years of age; 5 men, 2 women) and 7, a low activity level (68 +/- 6 years of age; 5 women, 2 men). Following vessel segmentation from MRA by an individual blinded to subject activity level, quantitative measures of vessel number, radius, and tortuosity were calculated and histogram analysis of vessel number and radius was performed. RESULTS: Aerobically active subjects exhibited statistically significant reductions in vessel tortuosity and an increased number of small vessels compared with less active subjects. CONCLUSIONS: Aerobic activity in elderly subjects is associated with lower vessel tortuosity values and an increase in the number of small-caliber vessels. It is possible that an aerobic exercise program may contribute to healthy brain aging. MRA offers a noninvasive approach to visualizing the cerebral vasculature and may prove useful in future longitudinal investigations.

Health benefits for veteran (senior) tennis players.

To explore the health benefits of tennis participation in veteran players and to identify future research needs, an electronic literature search using the Ovid (Cinhal, Medline, Sport Discus) library databases from 1966-2005 was undertaken. Specific search words were employed related to tennis, aging, exercise, health, and the psychophysiological systems. Public access internet search engines were also used (Google, PubMed), along with non-electronic searches of library holdings. There is ample research documenting the health benefits of regular participation in moderately intense aerobic activity. There have been research studies targeting veteran tennis players but most were cross sectional. No tennis related study successfully eliminated all confounding cross training effects. The health of veteran tennis players is improved by enhanced aerobic capacity, greater bone densities in specific regions, lower body fat, greater strength, and maintained reaction time performance in comparison with age matched but less active controls. However, it is not certain whether tennis alone can be a sole contributor to these physiological variables. Well controlled longitudinal research among elite veteran and novice older adult players is needed.

A comparison of leg-to-leg bioelectrical impedance and skinfolds in assessing body fat in collegiate wrestlers.

A comparison of the leg-to-leg bioelectrical impedance (BIA) system and skinfold analysis in estimating % body fat in a large number of National Collegiate Athletic Association (NCAA) collegiate wrestlers was conducted. A series of 5 cross-sectional assessments, including the NCAA Division I and III Championships, were completed throughout the 1998-1999 wrestling season with samples ranging from (N = 90-274). Body density was determined from the 3 skinfold measures using the Lohman prediction equation. BIA measurements were determined using the Tanita body fat analyzer, model 305. Significant correlations between methods ranging from (r = 0.67-0.83, p < 0.001) and low standard error of estimates (SEE) for % body fat ranging from 2.1-3.5% were found throughout the 5 assessment periods. This preliminary study demonstrated that the leg-to-leg bioelectrical impedance system accurately estimated % body fat when compared to skinfolds in a diverse collegiate wrestling population.

Reproducibility of resting heart rate variability with short sampling periods.

The purpose of this study was to determine whether resting heart rate variability (HRV) is reproducible with short sampling measurement periods using an office-based personal computer measurement system. Eight healthy active women participated in ECG analyses on 2 days within 1 week under controlled environmental and physiological conditions. After they rested for 10 minutes, a 10-min ECG was recorded. HRV was determined from a 2.5- and 5-min sample period using both time domain variables (meanRR and SDNN) and frequency domain variables (LF, HF, LF:HF). Repeated measures ANOVA found no significant differences between Day 1 and Day 2 for either sampling period (p > or = 0.23). For both the 2.5- and 5-min sampling periods, the intraclass correlations between days for the time domain variables showed good reproducibility (R = 0.86-0.90). The reproducibility of the frequency domain variable was only average (R = 0.67-0.96), with the LF:HF ratio yielding the higher R values.

Spectral analysis of heart rate variability and pulmonary responses to topical applications of 2% aminophylline-based thigh cream.

OBJECTIVE: Noninvasive assessment of the immediate and delayed cardiopulmonary response to a 2% aminophylline-based topical thigh reducing cream. DESIGN: Prospective, double-blind, randomized, counterbalanced study with application of: no cream (NC), placebo cream (PC) or 2% aminophylline cream (AC). SUBJECTS: Nine healthy women (aged: 23+/-3 y; weight: 58+/-3 kg; height: 165+/-7 cm; body fat: 19+/-6%; estimated maximal aerobic fitness VO2max): 40+/-4 ml/kg/min). MEASUREMENTS: Medical history, skin patch test, skinfolds, YMCA submaximal cycle ergometry test, psychological evaluations (POMS and Speilberger STAI-1). Pulmonary function and spectral analysis on heart rate variability, measured immediately post-and 4 h post-treatment, on three separate days within a three-week period. RESULTS: Pulmonary function did not change. The averaged R-R interval (ms) was significantly lower for the immediate post AC treatment, but returned to baseline in 4 h. CONCLUSION: Application of a 2% aminophylline-based thigh cream does not affect pulmonary function, however, it may cause a temporary, transient reduction in the averaged R-R interval.

The importance of fat free mass maintenance in weight loss programmes.

Obese individuals have excess total body mass, a condition resulting from an overaccumulation of both fat and fat free mass (FFM). Research has been focusing on the need to maintain FFM during weight loss because of its integral role in metabolic rate regulation, preservation of skeletal integrity and maintenance of functional capacity. It has been suggested that FFM loss should compose no more than 30% of total weight loss. Because skeletal muscle in the obese has been shown to consist of an increased amount of low density muscle tissue, impaired strength: size ratio, less capillarisation, decreased mitochondrial density, and consequently impaired work capacity, it may be necessary to stratify FFM into essential and less essential FFM categories. With this categorisation, more specific quantification of FFM loss and maintenance can be made. While FFM influences several physiological functions, it may be that a minimal loss of FFM from the obese state is not only unavoidable, but actually desirable if the loss is in the form of less essential FFM.

Fat-free mass is maintained in women following a moderate diet and exercise program.

Weight-loss programs usually result in fat-free mass (FFM) loss along with body-fat (BF) loss. This study examined which combination of diet + exercise would maintain FFM. Forty-four overweight, inactive women completed 20 wk of a randomized intervention: control (C, N = 6), diet only (D, N = 10), diet + cycling (DC, N = 8), diet + resistance training (DR, N = 11), or diet + resistance training + cycling (DRC, N = 9) group. FFM and %BF were determined from hydrostatic weighting. Exercise sessions were attended 3 d.wk-1, with a mean duration of 30 min per session. Caloric intake was reduced 628 kcal.d-1 (+/- 59). Chi squares and ANOVA showed no baseline differences between groups for socioeconomic status, age, body composition, aerobic capacity, or strength. One-way ANOVA of change with Student-Newman Keul multiple range post-hoc tests (P < 0.05) were used to analyze pre to post differences for %BF, body mass (BM), FFM, VO2max, and strength. D, DC, DR, and DRC lost significant BM (-3.7 to -5.4 kg) in comparison with C (+ 1.5 kg). All groups maintained FFM but only DRC significantly lowered %BF (-4.7%) in comparison with C. DRC and DC significantly increased VO2max. Strength 1RM (triceps extension, arm curl, leg extension, chest press) increased significantly for both DR and DRC. Results suggest that moderate levels of caloric restriction, aerobic cycle exercise, and/or resistance training are equally effective in maintaining FFM while encouraging body mass loss.

Cardiovascular effects of nicotine during physical activity and following meal consumption.

1. In two separate studies using healthy male smokers as subjects, the acute cardiovascular effects of a measured dose of nicotine (15 micrograms/kg) were examined in conjunction with light physical activity and following consumption of a meal, conditions typical of nicotine intake via smoking. 2. Increases in heart rate and systolic blood pressure attributable to nicotine were similar during rest, physical activity, and following eating, demonstrating additivity with the cardiovascular effects of activity and a caloric load. Diastolic blood pressure was less affected by nicotine. 3. These results indicate that cardiovascular activity is acutely increased following nicotine (smoking) regardless of other influences on the cardiovascular system. Such effects may help explain increased risks of acute cardiac abnormalities due to smoking.

Reduced supine cardiac volumes and diastolic filling rates in elderly patients with chronic medical conditions. Implications for postural blood pressure homeostasis.

Very elderly individuals with multiple chronic illnesses are at high risk of orthostatic hypotension, falls, and associated morbidity and mortality. Alterations in cardiac volumes and filling characteristics may contribute in part to an increased prevalence of orthostatic hypotension and falls in these people. In this study cardiac function was evaluated with gated radionuclide ventriculography in eight healthy young subjects (19-38 years) and 25 elderly persons with stable chronic illnesses (73-96 years), 14 of whom had a history of recurrent falls. Blood pressure was measured supine during the radionuclide ventriculography, then after one minute of standing. Supine stroke volume index, end diastolic volume index, cardiac index, and peak filling rates were significantly lower in elderly subjects compared to young, and ejection fraction and end systolic volume index (measures of systolic function) were the same in young and old. Compared to the young, elderly subjects had a reduction in ventricular filling during the first third of diastole, but an augmentation in the last third, during atrial contraction. Within the group of elderly subjects, the directional change in systolic blood pressure during orthostasis was significantly correlated with basal supine systolic blood pressure (R = 0.81, P less than .0001) and supine cardiac index (R = 0.66, P = .002). Thus, very old people representative of those seen in clinical practice have reduced cardiac volumes and impaired early diastolic filling, a result possibly related to elevations in systolic blood pressure. These changes in cardiac structure and function may contribute, in part, to orthostatic hypotension in advanced age.

Acute effects of nicotine on resting metabolic rate in cigarette smokers.

The acute effects of nicotine on resting metabolic rate (RMR) were examined to identify a mechanism that may help explain the inverse association between smoking and body weight. Multiple administrations of two nicotine doses (moderate [15 micrograms/kg body wt] and low [7.5 micrograms/kg body wt]) and a placebo (0 micrograms) were presented to 18 male smokers via nasal-spray solution on three separate occasions while RMR was assessed by computerized open-circuit indirect calorimetry. Plasma nicotine levels confirmed the reliability of dosing. RMR increases of 6% above base line after both moderate and low doses were significantly greater than the 3% increase after the placebo. Subsequent examination of the effects of smoking a nonnicotine cigarette suggested that the small placebo effect was due to acute metabolic consequences of inhalation. These results confirm that intake of nicotine, isolated from tobacco smoke, significantly increases RMR in humans. However, the results also indicate that non-pharmacological, behavioral aspects of smoking may also contribute to acutely increasing RMR in smokers.

The effect of nicotine on energy expenditure during light physical activity.

The metabolic effects of nicotine have been implicated in the relation between smoking and lower body weight. This study examined whether the nicotine-induced increase in the metabolic rate observed at rest is also present during physical activity. We compared the energy expenditure of 10 male smokers receiving nicotine (15 micrograms per kilogram of body weight) with that of 10 male smokers receiving placebo on two occasions, each including a period of rest and a period of exercise on a modified bicycle ergometer at workloads designed to simulate and standardize light daily activity. All had abstained from cigarette smoking the night before the study. The excess energy expenditure attributable to nicotine was more than twice as great during exercise (difference between groups, 0.51 kJ per kilogram per hour, or 12.1 percent of the metabolic rate at rest; P less than 0.001) than during rest (0.23 kJ per kilogram per hour, or 5.3 percent of the metabolic rate at rest; P less than 0.05). In contrast, the expenditure was not affected by placebo during exercise or rest in the smokers or in a comparison group of 10 non-smokers, indicating that smoking status has no long-term metabolic effect in the absence of short-term nicotine intake. We conclude that the relatively small metabolic effect of nicotine when the subject is at rest is enhanced during light exercise. Our data also suggest that the weight gain that often follows smoking cessation may be influenced not only by nicotine intake but also by the level of physical activity a smoker typically engages in while smoking.

Chronic and acute tolerance to the heart rate effects of nicotine.

Tolerance to the effects of nicotine reflects physiological adaptation and may be related to the development and persistence of smoking behavior. However, little is known about tolerance to nicotine in humans, in part due to methodological difficulties. This study examined chronic and acute tolerance to nicotine's effect on heart rate (HR) using a measured-dose nasal spray nicotine procedure. Eight "Light" smokers (less than 20 cigarettes per day) and ten "Heavy" smokers (greater than or equal to 20 per day) participated in two sessions on separate days in which they received four administrations (1 every 20 min) of a high nicotine dose (15 micrograms per kg body weight, equivalent to a typical cigarette) or a low nicotine dose (7.5 micrograms/kg) while HR was monitored during the 5 min following each administration. Compared with Light smokers, Heavy smokers had significantly smaller HR responses to the high dose, indicating greater chronic tolerance, but there was no difference between groups in response to the low dose. Acute tolerance to HR response across the four 5-min periods was not observed with either dose. However, subsequent examination of HR response in the first 2 min following each dose administration did suggest acute tolerance, particularly for the low dose, as this more acute HR response declined from the first to the last administration. These results demonstrate chronic and, to a lesser extent, acute tolerance to HR effects of nicotine and suggest that both may be dose dependent.