Phillip B. Sparling

Sedentary Behavior: Emerging Evidence for a New Health Risk

Compared with our parents or grandparents, we are spending increasing amounts of time in environments that not only limit physical activity but require prolonged sitting—at work, at home, and in our cars and communities.1 Work sites, schools, homes, and public spaces have been (and continue to be) re-engineered in ways that minimize human movement and muscular activity. These changes have a dual effect on human behavior: people move less and sit more. From an evolutionary perspective, humans were designed to move—to locomote and engage in all manner of manual labor throughout the day. This was essential to our survival as a species. The recent shift from a physically demanding life to one with few physical challenges has been sudden, occurring during a tiny fraction of human existence. n nSocietal indicators of reductions in human energy expenditure and increases in sedentary behavior during the past several decades are particularly striking. In 1970, 2 in 10 working Americans were in jobs requiring only light activity (predominantly sitting at a desk), whereas 3 in 10 were in jobs requiring high-energy output (eg, construction, manufacturing, farming).2 By 2000, more than 4 in 10 adults were in light-activity jobs, whereas 2 in 10 were in high-activity jobs.2 Moreover, during the past 20 years, total screen time (ie, using computers, watching television, playing video games) has increased dramatically. In 2003, nearly 6 in 10 working adults used a computer on the job and more than 9 in 10 children used computers in school (kindergarten through grade 12).3 Between 1989 and 2009, the number of households with a computer and Internet access increased from 15% to 69%.3 Other significant contributors to daily sitting time—watching television and driving personal vehicles—are at all-time highs, with estimates of nearly 4 hours and 1 hour, respectively.4,5 n nScientists studying the ill effects of this decrease in physical activity have revealed a complex, multifaceted relationship among physical work, energy expenditure, and health.6,7 Clinical and basic research has focused on the benefits of incorporating regular bouts of exercise into modern life to adjust to some extent for the loss of the physically active life led by our ancestors.6 Current public health recommendations propose engaging in at least 150 minutes per week of moderate-to-vigorous activity to help prevent and manage multiple chronic conditions, notably cardiovascular disease, type 2 diabetes, obesity, and some cancers.7 The evidence base that supports this exercise recommendation is substantial. (Here, we use the terms exercise and moderate-to-vigorous activity interchangeably, recognizing that, by some definitions, exercise refers specifically to intentional activity carried out for health/fitness purposes.7) n nThose who do not exercise have by convention been termed sedentary. However, this is no longer an adequate perspective. Recent epidemiologic evidence suggests that the metabolic and long-term health consequences of habitual sedentary behavior (too much sitting) are distinct from those associated with a lack of moderate-to-vigorous activity (too little exercise).8,9 This shift in perspective is being clarified through innovations in technology used to characterize movement patterns in populations.

Endurance Exercise Selectively Impairs Prefrontal-Dependent Cognition.

Two experiments are reported that examine the possibility that exercise selectively influences different types of cognition. To our knowledge, these experiments represent the first attempt to study higher-cognitive processes during exercise. Theoretical thinking was guided by the transient hypofrontality hypothesis. In both experiments, athletes who exercised at a sustained, moderate pace were compared to sedentary controls on two neuropsychological tests, one that is generally regarded as heavily dependent on prefrontal cognition and one that is relatively insensitive to prefrontal operation. Results showed that during exercise performance on tests demanding prefrontal-dependent cognition was impaired, while at the same time, cognitive processes requiring little prefrontal activity were unaffected.

Recommendations for physical activity in older adults

Older adults find it difficult to meet moderate and vigorous exercise targets. Given that a dose-response exists for physical activity and health benefits, Phillip B Sparling and colleagues argue that a change in message to reduce sedentary time and increase light activities may prove more realistic and pave the way to more intense exercise

Physical Activity Patterns in Recent College Alumni

Within this sample of recent college alumni, a high proportion indicated that they enjoy exercise (66.1%) and felt confident in setting their own fitness programs (79.4%). Yet, only 34.3% reported engaging in recommended levels of moderate or vigorous PA. In contrast to previous reports, rates of participation in vigorous, moderate, and strengthening-type PA did not differ between men and women. Alumni who reported that they engaged in adequate levels of moderate or vigorous PA had gained significantly less weight in the years following graduation than those who reported being insufficiently active (3.0 kg vs. 6.1 kg). Last, we noted a strong positive association between PA patterns as college seniors and current PA behavior as recent alumni.

University campus settings and the promotion of physical activity in young adults: lessons from research in Australia and the USA

Describes the decreasing prevalence of physical activity participation over the young adult years and the patterns of difference in the physical activity habits of young men and young women. Physical activity habits during the young adult years are likely to be important influences on habitual physical activity during overall adult life and, consequently, have significant implications for long-term health outcomes. Tertiary-education campuses are settings where there exist important yet partially neglected opportunities to influence the physical activity habits of young adults. Uses examples from Australia and the USA are used to characterise relevant contextual and practical aspects of the campus setting and the physical activity promotion opportunities that it may provide. Reviews findings from two campus-based physical activity intervention studies. In conclusion, identifies a set of issues that require further research.

Evaluation of the Bod Pod® for assessing body fat in collegiate football players

PURPOSEnThe purpose of this investigation was to evaluate the accuracy of a new air displacement plethysmograph, BOD POD Body Composition System, for determining %fat in collegiate football players.nnnMETHODSnBody fatness was estimated from body density (Db), which was measured on the same day using the BOD POD and hydrostatic weighing (HW) in 69 Division IA football players. In addition, 20 subjects were whole body scanned using dual-energy x-ray absorptiometry, DXA (Lunar DPX-L) to assess total body mineral content and %fat. Mineral content and HW determined Db were used to compute %fat from a three-component model (3C; fat, mineral, and residual).nnnRESULTSnTest-retest reliability for assessing %fat using the BOD POD (N = 15) was 0.994 with a technical error of measurement of 0.448%. Mean (+/- SEM) Db measured with the BOD POD (1.064 +/- 0.002 g x cc(-1) was significantly greater (P < 0.05) than HW (1.060 +/- 0.002 g x cc(-1)), thus resulting in a lower %fat for the BOD POD (15.1 +/- 0.8%) compared with HW (17.0 +/- 0.8%). Similar results (N = 20) were found for DXA (12.9 +/- 1.2%) and the 3C (12.7 +/- 0.8%) where %fat scores were significantly higher (P < 0.05) than scores determined using the BOD POD (10.9 +/- 1.0%).nnnCONCLUSIONSnDb measured with the BOD POD was higher than the criterion HW, thus yielding lower %fat scores for the BOD POD. In addition, BOD POD determined %fat was lower than DXA and 3C determined values in a subgroup of subjects. Assessment of %fat using the BOD POD is reliable and requires minimal technical expertise; however, in this study of collegiate football players, %fat values were underpredicted when compared to HW, DXA, and the 3C model.

Understanding Adherence to 5 Servings of Fruits and Vegetables per Day: A Theory of Planned Behavior Perspective

OBJECTIVEnThe primary purpose of the present study was to examine the utility of the Theory of Planned Behavior (TPB) in explaining the 5-A-Day intentions and behavior of college students. A secondary purpose was to determine whether any of the TPB relationships were moderated by gender or ethnicity.nnnDESIGNnA prospective design that asked college students to complete a baseline TPB 5-A-Day questionnaire and a fruit and vegetable consumption measure 1 week later.nnnSETTINGnUndergraduate fitness and health classes at 2 universities in the southern United States.nnnPARTICIPANTSn511 college students with a mean age of 19.8 years (standard deviation = 2.71).nnnMAIN OUTCOME MEASURESnTPB variables and fruit and vegetable consumption.nnnANALYSESnPath analyses and invariance (ie, to examine ethnic and gender moderated) analyses.nnnRESULTSnAffective attitude (beta = .16, P < .05) and perceived behavioral control (beta = .59, P < .05) were significant predictors of intention, which in turn was a significant predictor of behavior (beta = .32, P < .05). Follow-up invariance analyses showed that none of the TPB relationships was moderated by gender or ethnicity.nnnCONCLUSIONS AND IMPLICATIONSnThe TPB may be a useful framework on which to base a 5-A-Day intervention for male and female college students of different ethnic backgrounds.

A meta-analysis of studies comparing maximal oxygen uptake in men and women.

Abstract Since [Vdot]O2 max (ml/minute · kg body weight) is known to be the primary determinant of work capacity in weight-bearing exercise, the quantification of sex-specific factors influencing aerobic capacity is necessary if appropriate work capacity and endurance performance expectations and standards are to be developed for men and women. Yet, due to varying procedures and sample characteristics, large discrepancies exist among studies concerning the magnitude of the sex difference in [Vdot]O2 max. The purpose of this article is to provide an integrative review of the research comparing [Vdot]O2 max in men and women using the meta-analytic strategy proposed by Glass (1976). An overall estimate of the magnitude of the sex effect for each of three expressions of [Vdot]O2 max is provided. When removing the variability in aerobic capacity due to body size and body fatness, the magnitude of difference in [Vdot]O2 max between men and women is substantially reduced. When expressed relative to fat-free weig...

The gender difference in distance running performance has plateaued : An analysis of world rankings from 1980 to 1996

PURPOSEnAnnual world rankings from 1980-1996 were used i) to determine if the gender difference in distance running events has stabilized, and ii) to examine whether the relative decline in pace as race distance increases is different between men and women. World best (WB) and 100th best times in the 1500 m and the marathon (42 km) for each of the 17 years were the indices used to represent overall trends in mens vis-à-vis womens distance running.nnnMETHODSnThese data were analyzed using regression analyses to develop and compare gender-specific equations. In the 1500 m, the gender difference in WB times (11.1 +/- 1.1%) was consistent from 1980 to 1996, and the slight rate of improvement in event depth (i.e., 100th rankings) was similar for men and women.nnnRESULTSnIn the marathon, the gender difference in WB times (11.2 +/- 0.9%) was essentially the same as for the 1500 m. In 1980, the marathon was a fairly new event for the women, having only just been sanctioned by the International Amateur Athletics Federation (IAAF). As a consequence, the depth of the field increased quickly from 1980 to 1984. Since the mid-1980s, the rate of improvement for women in 100th-ranked times has leveled off to equal that of men. The average declines in relative pace for men and women from the 1500 m to the 10 km to the marathon were found to be remarkably similar with no diminishing of the gender difference as race distance increased.nnnCONCLUSIONSnBased on worldwide indices of competitive distance running, the gender difference in distance running performance has plateaued in recent years. Concomitantly, over the past decade, opportunities for women to train and compete have approached parity with those of men. It is likely that the current gender difference in performance will remain fairly constant because of biological differences between men and women that give men an advantage in distance running.

Carbohydrate-electrolyte replacement improves distance running performance in the heat

The effects of a 7% carbohydrate-electrolyte drink (CE) and an artificially sweetened placebo (P) on performance and physiological function were compared during a 40-km run in the heat. Eight highly trained male runners completed two runs on a measured outdoor course. The first 35 km of each run was performed at self-selected training pace and the last 5 km at race effort. Under a counterbalanced, double-blind design, subjects consumed 400 ml of either CE or P 30 min prior to exercise, and 250 ml every 5 km thereafter during the run. Rectal temperature, heart rate, rating of perceived exertion, sweat rate, and respiratory exchange ratio were similar during the run for CE and P. Serum Na+, K+, Cl-, total protein, osmolality, blood lactate, urea nitrogen, and % change in plasma volume were also similar for both drink conditions; however, blood glucose was significantly higher (P less than 0.01) with CE. Running performance in the last 5 km was significantly faster (P less than 0.03) during CE (21.9 min) compared with P (24.4 min). Subjects reported no differences in stomach upset, bloating, or nausea between P and CE. Results indicate that CE replacement elicits similar thermoregulatory and physiological responses during prolonged running in the heat but increases run performance and blood glucose when compared with P.