Colin Boreham

The physical activity, fitness and health of children

It is clear that, despite their natural tendencies, children have become less physically active in recent decades, with children today expending approximately 600 kcal· day -1 less than their counterparts 50 years ago. Although the health consequences of a reduced energy expenditure in adults is well documented, there is little direct evidence linking sedentariness with health in children. However, three main benefits arising from adequate childhood physical activity have been postulated. The first is direct improvements in childhood health status; evidence is accumulating that more active children generally display healthier cardiovascular profiles, are leaner and develop higher peak bone masses than their less active counterparts. Secondly, there is a biological carryover effect into adulthood, whereby improved adult health status results from childhood physical activity. In particular, childhood obesity may be a precursor for a range of adverse health effects in adulthood, while higher bone masses in young people reduce the risk of osteoporosis in old age. Finally, there may be a behavioural carryover into adulthood, whereby active children are more likely to become more active (healthy) adults. However, supporting evidence for this assertion is weak. Given this background, recent health guidelines suggesting that children should accumulate 60 min of moderate-intensity physical activity every day - supplemented by regular activities that promote strength flexibility and bone strength - appear to be justified. Future developments should include the implementation of large-scale, longitudinal studies spanning childhood and young adulthood, the further refinement of tools for measuring physical activity accurately in young people, and research into the relative strength of association between fitness - as well as activity - and health in children.

The ABC of Physical Activity for Health: A consensus statement from the British Association of Sport and Exercise Sciences

Absract Our understanding of the relationship between physical activity and health is constantly evolving. Therefore, the British Association of Sport and Exercise Sciences convened a panel of experts to review the literature and produce guidelines that health professionals might use. In the ABC of Physical Activity for Health, A is for All healthy adults, B is for Beginners, and C is for Conditioned individuals. All healthy adults aged 18–65 years should aim to take part in at least 150 min of moderate-intensity aerobic activity each week, or at least 75 min of vigorous-intensity aerobic activity per week, or equivalent combinations of moderate- and vigorous-intensity activities. Moderate-intensity activities are those in which heart rate and breathing are raised, but it is possible to speak comfortably. Vigorous-intensity activities are those in which heart rate is higher, breathing is heavier, and conversation is harder. Aerobic activities should be undertaken in bouts of at least 10 min and, ideally, should be performed on five or more days a week. All healthy adults should also perform muscle-strengthening activities on two or more days a week. Weight training, circuit classes, yoga, and other muscle-strengthening activities offer additional health benefits and may help older adults to maintain physical independence. Beginners should work steadily towards meeting the physical activity levels recommended for all healthy adults. Even small increases in activity will bring some health benefits in the early stages and it is important to set achievable goals that provide success, build confidence, and increase motivation. For example, a beginner might be asked to walk an extra 10 min every other day for several weeks to slowly reach the recommended levels of activity for all healthy adults. It is also critical that beginners find activities they enjoy and gain support in becoming more active from family and friends. Conditioned individuals who have met the physical activity levels recommended for all healthy adults for at least 6 months may obtain additional health benefits by engaging in 300 min or more of moderate-intensity aerobic activity per week, or 150 min or more of vigorous-intensity aerobic activity each week, or equivalent combinations of moderate- and vigorous-intensity aerobic activities. Adults who find it difficult to maintain a normal weight and adults with increased risk of cardiovascular disease or type 2 diabetes may in particular benefit from going beyond the levels of activity recommended for all healthy adults and gradually progressing towards meeting the recommendations for conditioned individuals. Physical activity is beneficial to health with or without weight loss, but adults who find it difficult to maintain a normal weight should probably be encouraged to reduce energy intake and minimize time spent in sedentary behaviours to prevent further weight gain. Children and young people aged 5–16 years should accumulate at least 60 min of moderate-to-vigorous-intensity aerobic activity per day, including vigorous-intensity aerobic activities that improve bone density and muscle strength.

The Health-Related Physical Activity of Children

SummaryThe fitness and physical activity levels of children and youth are commonly questioned, but the evidence cited is both equivocal and methodologically diverse. The amount and type of physical activity undertaken during childhood that is appropriate for optimal health is unknown, although it has been suggested that, in the absence of such criteria, activity levels known to confer health benefits in adults are also appropriate for children. The measurement of activity in children is problematical, and there is currently no valid method of assessing activity levels that is feasible for use in large studies. Therefore, studies may lack either internal validity or wider applicability.Studies using self-report methods indicate relatively high levels of activity with 60 to 70% of children taking sufficient ‘appropriate’ physical activity. However, a variety of activity thresholds have been used. Studies that use more objective methods report much lower levels of activity, especially when cardiovascular fitness criteria are applied. The use of less stringent health-related thresholds results in higher levels of ‘appropriate’ activity. Nearly all studies of teenagers report a decline in activity with age during this period. Data from the large population studies indicate that activity levels peak in children at around 13 to 14 years of age, and then markedly decline. Boys are normally reported to be more active than girls, but this difference is greatly reduced when moderate activity alone is compared, indicating that boys participate in more vigorous exercise than girls. The health effects of low levels of vigorous activity in children are unclear.There is a need to identify more clearly the quantity and type of activity which is appropriate for children’s health and well-being, and to improve assessment techniques. There is a particular need to assess the value of, and measure the prevalence of, low to moderate intensity activity below the level normally considered appropriate for cardiorespiratory fitness improvement.

The relationship between active travel to school and health-related fitness in children and adolescents: a systematic review

BackgroundActive travel to school (ATS) has been identified as an important source of physical activity for youth. However, the relationship between ATS and health-related fitness (HRF) among youth remains unclear.MethodsA systematic search of seven electronic databases (EMBASE, OVID MEDLINE, PsycINFO, PubMed, Scopus, SPORTDiscus and TRIS on line) was conducted in December 2009 and studies published since 1980 were considered for inclusion.ResultsTwenty seven articles were identified that explored the relationship between ATS and the following aspects of HRF: weight status/body composition, cardiorespiratory fitness, muscular fitness and flexibility. Forty-eight percent of the studies that examined the relationship between ATS and weight status/body composition reported significant associations, this increased to 55% once poor quality studies were removed. Furthermore, the findings from five studies, including one longitudinal study, indicate that ATS is positively associated with cardiorespiratory fitness in youth. However, the evidence for the relationships between ATS and muscular fitness or flexibility is equivocal and limited by low study numbers.ConclusionsThere is some evidence to suggest that ATS is associated with a healthier body composition and level of cardiorespiratory fitness among youth. Strategies to increase ATS are warranted and should be included in whole-of-school approaches to the promotion of physical activity.

Genetic and environmental determinants of peak bone mass in young men and women.

Peak bone mass is an important risk factor for the development of osteoporosis in later life. Previous work has suggested that genetic, intrauterine, and environmental factors all contribute to the regulation of bone mass, but the ways in which they interact with each other to do so remain poorly understood. In this study, we investigated the relationship between peak bone mass and polymorphisms of the vitamin D receptor (VDR), estrogen receptor (ER) α, and collagen type Iα1 (COLIA1) genes in relation to other factors such as birth weight, lifestyle diet, and exercise in a population‐based cohort of 216 women and 244 men in their early 20s. Stepwise multiple regression analysis showed that body weight was the strongest predictor of bone mineral density (BMD) in women, accounting for 16.4% of the variance in spine BMD and 8.4% of the variance in femoral neck BMD. Other significant predictors were VDR genotype (3.8%) and carbohydrate intake (1.6%) at the spine and vitamin D intake (3.4%) and ER genotype (3.4%) at the femoral neck. Physical activity was the strongest predictor of BMD in men, accounting for 6.7% of the variance at the spine and 5.1% at the hip. Other significant predictors were body weight (5%) and ER PvuII genotype (2.8%) at the spine and weight (3.4%) and alcohol intake (2%) at the femoral neck. Birth weight was not a significant predictor of BMD at either site but COLIA1 genotype significantly predicted birth weight in women, accounting for 4.3% of the variance. We conclude that peak bone mass is regulated by an overlapping but distinct set of environmental and genetic influences that differ in men and women. However, much of the variance in BMD was unexplained by the variables studied here, which suggests that either most of the genes that regulate BMD remain to be discovered or major environmental influences on BMD exist that have not yet been identified.

Cardiorespiratory fitness, physical activity, and arterial stiffness: the Northern Ireland Young Hearts Project.

Poor cardiorespiratory fitness and low physical activity have been identified as determinants of greater arterial stiffness, a mechanism that can partially explain the association of both variables with increased cardiovascular disease. However, the nature of these associations are not clear because cardiorespiratory fitness and physical activity can both mediate and confound the associations of one another with arterial stiffness. This issue was therefore examined in a population-based cohort of young adults. Subjects included 405 young men and women participating in an ongoing longitudinal study, the Northern Ireland Young Hearts Project. Pulse wave velocity was used to determine arterial stiffness in 2 arterial segments (aortoiliac and aortodorsalis pedis) using a noninvasive optical method. Cardiovascular fitness was estimated with a submaximal cycle test of physical work capacity and physical activity was estimated using a modified Baecke questionnaire. Associations were investigated with the use of multiple linear regression models with adjustment for potential confounders and/or intermediate variables. Cardiorespiratory fitness and sports-related physical activity (but not leisure- and work-related physical activity) were inversely associated with arterial stiffness in young adults. The associations between sports-related physical activity and arterial stiffness were strongly mediated by cardiorespiratory fitness, whereas physical activity levels did not disturb the associations between cardiopulmonary fitness and arterial stiffness. These findings suggest that arterial stiffness-related benefits of exercise are most likely to accrue if exercise prescription in young adults targets improvements in cardiorespiratory fitness.

Carbonated Soft Drink Consumption and Bone Mineral Density in Adolescence: The Northern Ireland Young Hearts Project

In an observational study of 1335 boys and girls aged 12 and 15 years, higher intakes of carbonated soft drinks (CSDs) were significantly associated with lower bone mineral density at the heel, but only in girls. Owing to the upward trend in CSD intake in adolescence, this finding may be of concern.

Training effects of short bouts of stair climbing on cardiorespiratory fitness, blood lipids, and homocysteine in sedentary young women

Objectives: To study the training effects of eight weeks of stair climbing on Vo2max, blood lipids, and homocysteine in sedentary, but otherwise healthy young women. Methods: Fifteen women (mean (SD) age 18.8 (0.7) years) were randomly assigned to control (n  =  7) or stair climbing (n  =  8) groups. Stair climbing was progressively increased from one ascent a day in week 1 to five ascents a day in weeks 7 and 8. Training took place five days a week on a public access staircase (199 steps), at a stepping rate of 90 steps a minute. Each ascent took about two minutes to complete. Subjects agreed not to change their diet or lifestyle over the experimental period. Results: Relative to controls, the stair climbing group displayed a 17.1% increase in Vo2max and a 7.7% reduction in low density lipoprotein cholesterol (p<0.05) over the training period. No change occurred in total cholesterol, high density lipoprotein cholesterol, triglycerides, or homocysteine. Conclusions: The study confirms that accumulating short bouts of stair climbing activity throughout the day can favourably alter important cardiovascular risk factors in previously sedentary young women. Such exercise may be easily incorporated into the working day and therefore should be promoted by public health guidelines.

Physical activity, sports participation and risk factors in adolescents

The purpose of this study was to analyze the relationships between physical activity (ACT), including sports participation (SP) and antecedent risk factors for coronary heart disease (CHD), in a representative sample of adolescents from Northern Ireland, a region of high coronary mortality. Biological and behavioral risk factors were measured in a random sample of 1015 school children aged 12 and 15 yr. ACT and SP were assessed by self-report questionnaire, and relationships with biological risk factors were analyzed with stepwise multiple linear regression after controlling for potential confounders. Results showed that in 15-yr-old males ACT was beneficially associated with systolic blood pressure (P < 0.05), lipid profile, and cardiorespiratory fitness (both P < 0.01). In 15-yr-old females, SP was associated beneficially with fatness and cardiorespiratory fitness. Odds ratios calculated from logistic regression revealed that for the older children, a relatively small drop (-20%) in ACT (boys) or SP (girls) was significantly related to the probability of exposure to multiple risk factors. Overall, relationships were stronger for males rather than females and for older rather than younger children. This study provides further evidence for beneficial associations between ACT, SP, and CHD risk status in adolescents.

Fitness, fatness, and coronary heart disease risk in adolescents: the Northern Ireland Young Hearts Project

PURPOSE The purpose of this study was to examine the independence and relative strengths of association between coronary heart disease (CHD) risk status and both body fatness and cardiorespiratory (C-R) fitness in 12- and 15-yr-old adolescents. METHODS The study cohort consisted of 1015 schoolchildren aged 12 and 15 yr (251 12-yr-old boys, 258 12-yr-old girls, 252 15-yr-old boys, and 254 15-yr-old girls), representing a 2% random sample of each population group. For each child, height, weight, sexual maturity (pubertal status), skin-fold thicknesses (4 sites), blood pressure (random zero sphygmomanometer), nonfasting serum total, and high density lipoprotein (HDL)-cholesterol and C-R fitness (20-m shuttle run; 20-MST) were determined under standardized conditions. Socioeconomic status and habitual physical activity were also determined from questionnaire information. Multiple regression analyses were carried out to examine relationships between five CHD risk factors, and fitness and fatness and to examine the relative strengths of fitness and fatness on CHD risk status, correcting for potential confounding variables. RESULTS Our main findings were: 1) Relationships between fatness and CHD risk factors are invariably stronger than between fitness and the same risk factors. For example, partially adjusted standardized regression coefficients for 12-yr-old boys revealed significant relationships between all five CHD risk factors and fatness, compared with three of five for fitness. The corresponding figures for 12-yr-old girls were three of five (fatness) and one of five (fitness). Broadly similar results were apparent for 15-yr-olds. 2) Although relationships between fitness and CHD risk factors do not survive further adjustment for fatness, the relationships between fatness and CHD risk are more robust and are unaffected by further adjustment for fitness. CONCLUSION Our results indicate that the observed relationships between C-R fitness and CHD risk status in adolescents are mediated by fatness, whereas the observed relationships with fatness are independent of fitness. Primary prevention of CHD during childhood should therefore concentrate upon preventing or reversing undue weight gain.