Bonita L. Marks

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.

Role of Aerobic Fitness and Aging on Cerebral White Matter Integrity

Abstract:  Neuroimaging research suggests that cerebral white matter (WM) integrity, as reflected in fractional anisotropy (FA) via diffusion tensor imaging (DTI), is decreased in older adults, especially in the prefrontal regions of the brain. Behavioral investigations of cognitive functioning suggest that some aspects of cognition may be better preserved in older adults who possess higher levels of aerobic fitness. There are only a few studies, however, investigating potential mechanisms for the improvements in aerobic fitness. Our study suggests that greater aerobic fitness may be related to greater WM integrity in select brain regions.

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

Objective Aerobic fitness (VO2 peak) and obesity risk (OR) may impact brain health. This study examined hemispheric and segment specific relationships between VO2 peak, OR and cerebral white-matter (CWM) integrity in the cingulum brain region in healthy older adults. Methods Fifteen subjects (66±6 years) completed VO2 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 VO2 peak was moderately related to FA in the left middle cingulum segment (r partial=0.573, p=0.041) and explained 28.5% of FAs 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 FAs 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.

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 nicotines effect on heart rate(HR) using a measured-dose nasal spray nicotine procedure. Eight “Light” smokers (<20 cigarettes per day) and ten “Heavy” smokers (≥ 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 μg per kg body weight, equivalent to a typical cigarette) or a low nicotine dose (7.5 μg/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.

The Importance of Fat Free Mass Maintenance in Weight Loss Programmes

SummaryObese 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.

The effects of healthy aging on intracerebral blood vessels visualized by magnetic resonance angiography

Histological and magnetic resonance imaging studies have demonstrated that age-associated alterations of the human brain may be at least partially related to vascular alterations. Relatively little information has been published on vascular changes associated with healthy aging, however. The study presented in this paper examined vessels segmented from standardized, high-resolution, magnetic resonance angiograms (MRAs) of 100 healthy volunteers (50 males, 50 females), aged 18-74, without hypertension or other disease likely to affect the vasculature. The subject sample was divided into 5 age groups (n=20/group) with gender equally distributed per group. The anterior cerebral, both middle cerebral, and the posterior circulations were examined for vessel number, vessel radius, and vessel tortuosity. Males exhibited larger vessel radii regardless of age and across all anatomical regions. Both males and females displayed a lower number of MRA-discernible vessels with age, most marked in the posterior circulation. Age-associated tortuosity increases were relatively mild. Our multi-modal image database has been made publicly available for use by other investigators.

Health Benefits of Tennis

The aim of the study was to explore the role of tennis in the promotion of health and prevention of disease. The focus was on risk factors and diseases related to a sedentary lifestyle, including low fitness levels, obesity, hyperlipidaemia, hypertension, diabetes mellitus, cardiovascular disease, and osteoporosis. A literature search was undertaken to retrieve relevant articles. Structured computer searches of PubMed, Embase, and CINAHL were undertaken, along with hand searching of key journals and reference lists to locate relevant studies published up to March 2007. These had to be cohort studies (of either cross sectional or longitudinal design), case–control studies, or experimental studies. Twenty four studies were identified that dealt with physical fitness of tennis players, including 17 on intensity of play and 16 on maximum oxygen uptake; 17 investigated the relation between tennis and (risk factors for) cardiovascular disease; and 22 examined the effect of tennis on bone health. People who choose to play tennis appear to have significant health benefits, including improved aerobic fitness, a lower body fat percentage, a more favourable lipid profile, reduced risk for developing cardiovascular disease, and improved bone health.

Perception of eating and exercise in children as a function of child and parent weight status

The present study assessed the effects of child body weight (obese/lean) and familial loading for obesity (two obese parents/two lean parents) on the psychophysics of sweetness, fatness and exercise workloads, as well as subjective ratings of foods varying in sugar and fat and activities varying in energy expenditure. Children were measured in a baseline state and at 6 months after the obese children had participated in a family-based behavioral weight control program. No differences between obese and lean children in perceptual ratings were observed. However, offspring of obese or lean parents differed on intensity rating, food palatability and activity enjoyment ratings. Intensity ratings for sweetness in offspring of obese parents was increased, with a similar trend for intensity ratings for fatness. Offspring of obese parents rated all foods and activities with lower palatability and enjoyment ratings than offspring of lean parents. After a 6 month family-based behavioral weight loss treatment, obese children had significant decreases in percent overweight while lean children remained stable. Changes in the pattern of food ratings were observed for the obese children, with a reduction in liking for foods high in fat and/or sugar, and an increase in ratings for food slower in fat and sugar. The effects of parental obesity on food and exercise intensity ratings and hedonic ratings were maintained. Overall, these results suggest parental weight influences behavioral factors related to obesity in children.

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.