WILEY-LISS PLENARY SESSION

Physical Activity, Physical Fitness, and Human Biology

Physical activity is a multidimensional behavior. It is viewed most often in terms ofenergy expenditure associated with movement and the stresses and strains associatedwith weight bearing and ground reaction forces. Physical fitness (performance- andhealth-related) and skill (proficiency) are other important dimensions related to sub-sistence and health. The context under which people are physically active is often over-looked. Context refers to types and settings, and includes subsistence, play, physicaleducation, exercise, sport, work, and others. Contexts per se and the meaningsattached to them vary among and within different cultural groups.

Physical activity and its important correlate physical fitness are central to many cur-rent discussions in public health and medicine; specifically, low levels of activity andaerobic fitness have important implications for health. Physical activity is also an in-tegral component in the evolutionary history of our species. A physically activity life-style on a regular basis has characterized our species for most of its existence. Veryrecently, it has been replaced by a sedentary lifestyle in developed and many develop-ing economies It is likely that we are biologically equipped for a physically active life-style, while cultural circumstances permit and reinforce the inactive alternative.Moreover, there have been negligible changes in our physical (skeletal) structureover the past 35,000 years or so. One can inquire, perhaps, as to how long can we tol-erate an inactive lifestyle and ready availability of food energy on essentially thesame structural base? Recent adaptations to a sedentary lifestyle constrained withina similar skeletal framework include increased overweight and obesity, decreasedcardiorespiratory fitness and muscular strength and endurance, decreased cardiovascu-lar and metabolic health, and increased morbidity and mortality. Do these cardiometa-bolic complications which are prevalent in increasing numbers of individuals in bothdeveloped and developing economies signal problems with the biological base?Moreover,these problems are increasingly more common among youth, which does not bode wellfor the future health ofmany populations, developed and developing alike.

Interface between the physical activitysciences and human biology. PT Katzmar-zyk. Queens University, Kingston, ON,Canada.

Chronic disease is quickly replacing com-municable disease and undernutrition asthe primary determinant of prematuremortality worldwide. Coronary artery dis-ease, stroke, hypertension, type 2 diabetes,and cancer have been prevalent amonghigh income countries for decades; how-ever, many low and middle income coun-tries are in the midst of the Nutrition Tran-sition and are experiencing increasingrates of chronic disease associated with therapid adoption ofWestern lifestyles, includ-ing changes in diet and physical activity.Indeed, theWorld HealthOrganization hasrecently estimated that two million deaths

worldwide annually are directly attribut-able to physical inactivity. The field ofhuman biology has traditionally had astrong focus on health-related issues,whereas the field of exercise science hashistorically placed an emphasis on per-formance-related physical activity and fit-ness. However, over the last two decades,there has been an increasing emphasis onhealth-related physical activity and physi-cal fitness in the field of exercise science.This shift has brought the fields of humanbiology and the physical activity sciencescloser together. Indeed, the study of physi-cal activity and human energetics is a cen-tral focus of much contemporary researchin human biology, drawing of many of thesamemethods as those used in exercise sci-ence. Given the changing patterns of physi-cal activity and health across countries of

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DOI: 10.1002/ajhb.20630

all socioeconomic status, the intersection ofhuman biology and the physical activitysciences has an important role to play indescribing and understanding the complexhealth issues associated with rapid eco-nomic transition. This paper will highlightsome of the important research questionsthat can be most effectively addressedthough the integration of approaches fromhuman biology and exercise science.

Physical activity and energy expenditurein the tropics: What do we know? DLDufour1, BA Piperata2. 1University ofColorado, Boulder, CO, 2Ohio State Uni-versity, Columbus, OH.

The current worldwide trend towardoverweight and obesity has led to arenewed interest in physical activity andenergy expenditure. Although reductionsin the level of physical activity is oftenassumed to be responsible for the trend to-ward overweight and obesity, there is apaucity of data on which to build such anassumption. Further, our understandingof the effects of environmental factors onlevels of physical activity and energy ex-penditure is limited. In this paper, we firstreview the literature available on physicalactivity and energy expenditure in popu-lations living in the lowland tropics,compare populations with different sub-sistence strategies, and where possible,compare physical activity and energy ex-penditure by reproductive status. Then,with the goal of better understanding var-iability in physical activity between differ-ent human groups, we focus on the activ-ity levels and energy expenditures ofwomen in three different setting for whomwehave good ethnographic data: TukanoanIndian women in the northwest Amazonia,Ribeirinha women in eastern Amazonia,andColombianwomen living in urbanCali.For the three cases, we compare (1) subsist-ence related determinants of physical activ-ity, including distances traveled to obtainfood; (2) effects of the division of laboron physical activity and energy expendi-ture; (3) diurnal patterns of activity in rela-tion to potential temperature constraints;(4) changes in activity patterns and energyexpenditure during pregnancy and lacta-tion; (5) day-to-day variability in energy ex-penditure and energy intake in relation tonutritional status.

Physical activity and subsistence energyexpenditure in circumpolar populations.WR Leonard1, JJ Snodgrass2, MV Soren-sen3. 1Northwestern University, Evan-ston, IL, 2University of Oregon, Eugene,OR, 3University of North Carolina,Chapel Hill, NC.

Early research on indigenous popula-tions of the north found that their subsist-ence lifeways required high levels of phys-ical activity and daily energy expenditure.The high energy demands of traditionalarctic life were associated with high levelsof aerobic fitness and low risks for obesityand cardiovascular (CV) disease. Overthe last 30 years, acculturation and socio-economic changes have resulted in theadoption of increasingly sedentary life-styles among native northern popula-tions. Shifts in diet and lifestyle haveresulted in marked declines in fitnessand CV health. Yet, while we have abun-dant evidence documenting the increas-ing prevalence of obesity, hypertension,and diabetes in native northern groups,we have very little information on howchanges in daily energy demands and ac-tivity patterns contribute to these emerg-ing health trends. This paper will addressthis gap by examining comparative dataon energy expenditure and physical activ-ity levels among indigenous Siberian pop-ulations living at different levels of accul-turation. Urbanization of lifestyle amongindigenous Siberians exerts a strongerinfluence on the physical activity levels ofwomen than men. Among men, the physi-cal activity levels of those living in tradi-tional herding brigades do not signifi-cantly differ from those living in largervillages and towns. In contrast, womenshow marked declines in physical activitylevels with acculturation, with the mosturbanized women having daily energyexpenditures that are only 40–50% abovebasal levels. The higher energy expendi-ture and activity levels among men arepartly associated with their continuedparticipation in physically intense sub-sistence activities (e.g., hunting, herding,hay cutting), even when living in villagesand towns. The large gender differencesin energy expenditure contribute tomarked differences in rates of overweightand obesity between Siberian men andwomen. These findings highlight import

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role that changing physical activity pat-terns play in shaping health trends inacculturating populations.

Activity, fitness and nutritional status.JD Haas, SE Crouter. Cornell University,Ithaca, NY.

Iron deficiency (ID) is the most commonnutrient deficiency in the United States,which affects *12% of the population ofwomen of reproductive age. Obesity hasreached epidemic proportions in the U.S.population, with 54.5% of women of child-bearing age classified as overweightor obese with a body mass index (BMI) �25 kg m2, and more than half of this groupclassified as obese with a BMI � 30 kg m2.The linkages between these two majornutritional problems have not been exten-sively studied. An important potentialmediating factor in the relationship be-tween low body iron stores and obesity isphysical activity (PA). It is well knownthat PA, an important part of the energybalance equation along with energyintake, plays an important role in the pre-vention and treatment of obesity, cardio-vascular disease, and other chronic dis-eases. It is also known that physical fit-ness is negatively affected by ID and irondeficiency anemia (IDA). The increasedrisk of fatigue associated with poor physi-cal fitness has the potential to reduce thelevel and intensity of discretionary PA inID and IDA individuals, thus contributingto positive energy balance and develop-ment of obesity if no compensation occursfrom reduced energy intake. Recent ex-perimental research inMexico and the USand analysis of the recent NHANES 99-04data will be presented as evidence for acausal link between iron nutritional sta-tus, physical activity, and obesity.

Activity, fitness and health outcomes inchildren and adolescents. RM Malina.Tarleton State University, Stephenville,TX.

It is generally assumed that regularphysical activity has a beneficial effect onthe health and physical fitness of childrenand adolescents. This paper systemati-cally evaluates the evidence related to this

assumption. Evidence is strongest forskeletal health, aerobic fitness, muscularstrength and endurance, adiposity inobese youth, and blood pressure in hyper-tensive youth. Evidence is suggestive foradiposity, HDL-C, and triglycerides innormal weight youth and blood pressurein normotensive youth. Data are limitedfor the metabolic syndrome, type 2 diabe-tes, and several indicators of cardiovascu-lar health in youth. In healthy, normalweight youth, the beneficial effects ofphysical activity are most evident in car-diovascular fitness, muscular strengthand endurance, and bone mineral contentand bone geometry; corresponding effectson adiposity, blood pressures, lipids, andlipoproteins are relatively small. On theother hand, beneficial effects of physicalactivity interventions are more apparentin unhealthy youth: the obese and hyper-tensive and those with the metabolic syn-drome.

Activity, fitness and health outcomes inadults. SN Blair1,2. 1University of SouthCarolina, Columbia, SC, 2University ofNorth Texas, Denton, TX.

Physical inactivity is now well estab-lished as an important cause of coronaryheart disease, type 2 diabetes, colon can-cer, loss of functional capacity, and otherhealth conditions. Much of the evidencelinking a sedentary way of life to healthoutcomes has been derived from relativelyhealthy populations, but there is also asubstantial amount of data on the benefitsof physical activity for people with chronicdisease or risk factors such as overweight,lipid profile, blood pressure, and carbohy-drate metabolism. Data from the AerobicsCenter Longitudinal Study show thatphysical fitness, determined by objectivelaboratory testing, protects against pre-mature mortality in women and men,middle-aged and older individuals, nor-mal weight and overweight persons, andin those who are healthy or who alreadyhave a chronic disease. In fact, fit individ-uals with chronic disease or a risk factoroften have lower death rates than unfitindividuals who are healthy. Moderatelevels of fitness are associated with sub-stantially lower death rates in all groupsin the population, and this level of fitness

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can be developed by taking three 10-minwalks/day for at least 5 days/week.

Genetics and health benefits associatedwith physical activity. C Bouchard. Pen-nington Biomedical Research Center,Baton Rouge, LA.

Being physically active is associatedwith a favorable risk profile for commonchronic diseases, reduced morbidities, andlower cardiovascular, and all-cause deathrates. A number of animal models haverevealed that there are strain differencesin spontaneous levels of physical activity.A threefold range has been observed be-tween the least and most active inbredmurine models. In humans, level of physi-cal inactivity exhibits familial aggrega-tion. Only a few candidate genes havebeen considered thus far, with the DRD2and MC4R genes being the most promi-nent. A recent genomic scan has revealedthree quantitative trait loci (QTLs) for anindicator of sedentarism.Human heterogeneity in response to

regular exercise is considerable. Resultsfrom twin studies and the HERITAGEFamily Study, all conducted with highlystandardized exercise-training programs,indicate that there is an almost 10-fold

range between the low- and high-gainersfor VO2 max. Similarly there are consid-erable differences in the changes regis-tered in body composition, blood pres-sure, insulin sensitivity, lipids and lipo-proteins, and other health-related traits.However, this heterogeneity in responseis not random as familial aggregationaccounts for as much as 50% of the age,sex, and baseline adjusted variance. Sev-eral candidate genes have been shown tobe predictors of the responsiveness toregular exercise: TTN and KIF5B forstroke volume; CETP for HDL-choles-terol; FLH1 and LEPR for insulin sensi-tivity; AGT and GNB3 for blood pressure.Skeletal muscle gene expression studieshave yielded novel candidates in theeffort to account for the difference be-tween the high gainers and low gainersfor insulin sensitivity. Genomic scansperformed with a large panel of markerson the HERITAGE Family Study cohorthave yielded four QTLs for the changesin hemodynamic phenotypes in responseto regular exercise. Progress in the posi-tional cloning of these QTLs will be sum-marized. It will eventually be possible toidentify at the DNA level the individualswho are likely to benefit from a physi-cally active lifestyle in terms of healthoutcomes.

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