This chapter presents and summarises the evidence which underpins guidelines from governments and international agencies with regard to the level and nature of physical activity likely to confer benefits for health. All aspects of the recommendations are discussed, including intensity, amount, frequency and pattern of aerobic activity as well as the need to maintain muscular strength and endurance. Recent evidence for the inclusion of guidance on sedentary behaviour is examined, as is the different approach of steps per day. A section on the potential of walking, a safe and easily accessible activity, to improve fitness and confer health benefits precedes a separate section on active travel. The challenge of changing physical activity behaviour is addressed, as are short sections dealing with ‘benefits versus risks’ and the economic consequences of high levels of inactivity.

This special issue of the British Journal of Sports Medicine marks the 21st anniversary of the publication of the seminal review paper Walking to Health by Morris and Hardman, which presented an elegant synthesis of the health benefits of walking, a broad and complex field of scientific enquiry.1 It concisely summarised the extensive physiological, metabolic and other health-related impacts of different patterns of walking across all ages, and also positioned this knowledge in the wider context of national public health efforts by providing practical and policy-relevant recommendations. The simplicity of its title reflects its core finding—walking is good for health. At all ages, for primary and secondary prevention, to save healthcare costs, for individuals to live their lives with the full potential of good health, to create better communities and to improve the environment, walking offers a solution. Providing guidance on how to use science in practical actions and to inform public policy may seem very contemporary, and for some an uncomfortable necessity, but communicating science so it could inform policy was a hallmark of the authors’ contribution to their respective fields of social epidemiology and exercise science. Those new to this field are encouraged to find time to read the original paper, in particular to see just how much we already knew back then. In 1997 as a final-year doctorate student, the first author (FCB) distinctly recalls the arrival of this review article by way of a library request. Back then, and certainly in Australia, not all journal articles were as readily available as they are today. Reading it was both rewarding and reinforcing because integrating the discipline of exercise science with the field …

We tested the hypothesis that 30 min of brisk walking daily would offset the increase in plasma TAG concentrations associated with substituting dietary fat for carbohydrate. Fourteen subjects (six males) aged 57 (sd 5) years underwent three 4 d trials in a counterbalanced order: (i) 4 d on a typical UK diet (40 % energy from fat, 45 % carbohydrate and 15 % protein); (ii) 4 d on an isoenergetic diet but substituting fat for carbohydrate in line with the present recommendations (30 % fat, 55 % carbohydrate and 15 % protein); (iii) 4 d on the same recommended diet with 30 min of brisk walking each day. The food provided for the first 3 d of each trial was isoenergetic with each volunteer's previously determined daily energy intake. On day 4, the subjects consumed breakfast, lunch and an early evening meal, equivalent in total to 90 % of their daily energy intake. Blood samples were collected and substrate utilisation and energy expenditure were determined in the fasted state and for 9 h postprandially. Substrate utilisation differed significantly among trials (P = 0·003); RER was higher on the recommended diet trial than during either of the other two trials (P = 0·012 and 0·021 for the UK diet and recommended diet with walking, respectively). The rise in plasma TAG concentrations over the day was steeper on the recommended diet trial than on the other two trials (trial × time interaction, P = 0·040). The increase in postprandial TAG concentrations associated with substituting dietary fat for carbohydrate was offset by 30 min of brisk walking daily.

This chapter contains section titled: Introduction Role of Physical Activity in Promoting Cardiovascular Health How Much is Required? Successful Interventions Recent Initiatives in the UK Key Points Recommendations for Future Research Key References

Knowledge of the reproducibility of oral fat tolerance tests is important for experimental design and data interpretation. In this study, seven normolipidaemic men underwent two fat tolerance tests (blood taken fasting and for six hours after a meal containing 1.2 g fat, 1.2 g carbohydrate per kg body mass) with an interval of one week. Eleven normolipidaemic women underwent two fat tolerance tests--one during the follicular phase of the menstrual cycle, the other during the mid-luteal phase. Dietary intake was controlled for two days and subjects refrained from exercise for three days before each test. There was no significant difference in postprandial triglyceride responses between the two tests in the men (10.20 +/- 3.45 mmol/l.h vs. 9.68 +/- 2.77 mmol/l.h, NS) (mean +/- SD); intraclass correlation coefficient between the two tests was 0.93, and within-subject coefficient of variation was 10.1 %. In the women, the postprandial triglyceride response was lower in the luteal phase (6.75 +/- 1.83 mmol/l.h) than in the follicular phase (8.36 +/- 3.71 mmol/l.h) (p = 0.05), intraclass correlation was 0.65 and within-subject coefficient of variation was 23.2 %. These results suggest that, with adequate control of preceding lifestyle, reproducibility of postprandial triglyceride responses is high in men, but menstrual phase should be taken into consideration when studying these responses in women.

This study aimed to determine whether changes in plasma heparin-releasable lipoprotein lipase (LPL) activity following a brisk walk were associated with decreases in fasting and/or postprandial triglyceride (TG) concentrations. Two groups of pre-menopausal women participated. In one group (fasting study group, n=10), TG concentrations and post-heparin plasma LPL activity were measured in the fasted state on two occasions: ~18 h after a 2-h treadmill walk at 50% maximal oxygen uptake (exercise trial); and after a day of no exercise (control trial). The other group (postprandial study group, n=9) undertook two oral fat tolerance tests (blood samples taken fasting and for 6 h after a high-fat meal), with plasma LPL activity measured 6 h after meal ingestion. Pre-conditions were the same as for the fasting study group (i.e. control and prior exercise). Prior exercise reduced fasting TG concentrations by 23 (7)% (fasting study group) [mean (SEM)] and by 18 (9)% (postprandial study group) (both P<0.05), and the postprandial TG response by 23 (6)% (postprandial study group) (P<0.01). Plasma LPL activity was not significantly increased by exercise in either the fasting or postprandial study groups. However, exercise-induced changes in both fasting and postprandial LPL activity were significantly correlated with the respective exercise-induced changes in fasting TG concentration and the postprandial TG response (r=−0.70 and −0.77 respectively, P<0.05 for both). These data suggest that increased LPL activity may contribute to the hypotriglyceridaemic effect of moderate exercise, although other mechanisms are also likely to be involved.

Endurance trained people exhibit low levels of postprandial lipemia. However, this favorable situation is rapidly reversed with de-training and it is likely that the triglyceride (TG) lowering effects of exercise are mainly the result of acute metabolic responses to recent exercise rather than long-term training adaptations. A large body of evidence suggests that postprandial lipemia can be attenuated following an individual exercise session, with the energy expended during exercise being an important determinant of the extent of TG lowering. Increased lipoprotein lipase-mediated TG clearance and reduced hepatic TG secretion are both likely to contribute to the exercise-induced TG reductions. These changes may occur in response to post-exercise substrate deficits in skeletal muscle and/or the liver. In addition, regular exercise can oppose the hypertriglyceridaemia sometimes seen with low-fat, high-carbohydrate diets. Levels of physical activity should therefore be taken into account when considering nutritional strategies for reducing the risk of cardiovascular disease.

OBJECTIVE: A low-fat, high-carbohydrate diet (≤30% of total energy intake as fat) in conjunction with moderate intensity physical activity is widely recommended for weight maintenance and reduction. The aim of this study was to assess the effect of adding daily exercise to a short-term high-carbohydrate diet on fasting and postprandial leptin levels. SUBJECTS: Eight healthy, postmenopausal women aged 60±4 y (mean±s.d.) (body mass index, BMI: 26.4±2.3 kg m −2 ; predicted maximal oxygen uptake: 29±2 ml kg −1 min −1 ). DESIGN: Plasma responses were studied after subjects consumed the same high-fat, mixed meal on three occasions: after 3 days on a low-carbohydrate diet (35, 50 and 15% energy from carbohydrate, fat and protein, respectively) (Low-CHO); after 3 days on an isoenergetic high-carbohydrate diet (corresponding values 70, 15 and 15%) (High-CHO); and after 3 days on the same high-carbohydrate diet with 60 min of brisk walking daily (High-CHO-Ex). MEASUREMENTS: Fasting and postprandial plasma or serum concentrations of leptin, glucose and insulin. RESULTS: Fasting leptin was significantly higher ( P <0.05) after the High-CHO (18.4±2.6 ng ml −1 ) (mean±s.e.m.) than after both the Low-CHO and the High-CHO-Ex interventions, which did not differ significantly from each other (16.9±2.1 and 15.5±2.0 ng ml −1 , respectively; P =0.08). Overall (fasted and postprandial states), plasma leptin concentrations were significantly higher after the High-CHO than after the High-CHO-Ex intervention. There was a strong, positive, linear relation between postprandial insulin responses and postprandial leptin concentrations at 6 h. In addition, there was a strong, negative, linear relation between whole-body insulin sensitivity (based on postprandial responses of glucose and insulin) and postprandial leptin concentrations at 6 h. CONCLUSION: Daily moderate intensity exercise, without concomitant changes in body fat mass, suppressed fasting and postprandial circulating leptin concentrations after consumption of a short-term high-carbohydrate diet. As shown in previous studies, insulin appears to be an important modulator of leptinaemia.

PURPOSE:To compare the effects of different patterns of regular brisk walking on fitness, risk factors for cardiovascular disease, and psychological well-being in previously sedentary adults. METHODS:Twenty-one subjects (14 women), aged 44.5 +/- 6.1 yr (mean +/- SD) were randomly assigned to two different, 6-wk programs of brisk walking in a cross-over design, with an interval of 2 wk. One program comprised one 30-min walk per day, 5 d.wk(-1) (long bout) and the other three 10-min walks per day, also 5 d.wk(-1) (short bouts). All walking was at 70-80% of predicted maximal heart rate. Maximal oxygen uptake ((.)VO(2max)), body composition, resting arterial blood pressure, fasting plasma lipoprotein variables, and psychological parameters were assessed before and after each program. RESULTS:Overall, subjects completed 88.2 +/- 1.1% and 91.3 +/- 4.1% of prescribed total walking time in the short- and long-bout programs, respectively. Both programs increased plasma concentrations of high-density lipoprotein cholesterol, and decreased concentrations of triacylglycerol and total cholesterol (all < 0.05). There were no changes in body mass, but the sum of four skinfolds, waist circumference, and hip circumference were decreased after both walking programs (all P<0.05). Predicted (.)VO(2max) increased with both programs ( P<0.05), but this increase was greater with the program based on short bouts (P<0.05). Both walking patterns resulted in similar decreases in tension/anxiety (P<0.05). CONCLUSION:These findings suggest that three short bouts (10 min) of brisk walking accumulated throughout the day are at least as effective as one continuous bout of equal total duration in reducing cardiovascular risk and improving aspects of mood in previously sedentary individuals.

Moderate exercise improves insulin sensitivity and reduces triacylglycerol (triglyceride; TG) concentrations. We hypothesized that changes in insulin sensitivity are an important determinant of exercise-induced changes in postprandial TG concentrations. Altogether, 38 men and 43 women, all of whom were normotriglyceridaemic and normoglycaemic, each underwent two oral fat tolerance tests with different pre-conditions: control (no exercise) and prior exercise (90 min of exercise at 60% of maximal O(2) uptake the day before). Venous blood samples were obtained in the fasting state and for 6 h after a high-fat mixed meal. In the control trial there were significant correlations between log fasting TG concentration and log fasting insulin concentration (r=0.42, P<0.0005) and between log postprandial TG response (area under the curve) and log postprandial insulin response (r=0.48, P<0.0005). Prior exercise reduced the fasting TG concentration by 18.2 +/- 2.2% (mean +/- S.E.M.) (P<0.0005), the postprandial TG response by 21.5 +/-1.9% (P<0.0005), the fasting insulin concentration by 3.8 +/- 3.1% (P<0.01) and the postprandial insulin response by 11.9 +/- 2.5% (P<0.0005). However, there was no relationship between the exercise-induced changes in log fasting TG and log fasting insulin (r=0.08, P=0.50), nor between the exercise-induced changes in log postprandial TG response and log postprandial insulin response (r=0.04, P=0.70). These data suggest that the reductions in fasting and postprandial TG levels elicited by a session of moderate-intensity exercise are not mediated by an increase in insulin sensitivity.

In this study, we examined the effects of 1 and 2 h of brisk walking on post-prandial metabolism. Eleven pre-menopausal women participated in three oral fat tolerance tests with different pre-conditions: control (no exercise), 1 h walk (1 h of walking at 50% maximal oxygen uptake, VO2max, on the day before) and 2 h walk (2 h walking at 50% VO2max on the day before). Venous blood samples were taken in the fasted state and for 6 h after ingestion of a high-fat mixed meal. Compared with the control trial, the 1 h walk reduced post-prandial lipaemia by a mean of 9.3%, whereas the 2 h walk reduced it by 22.8% (P < 0.01 for trend). Similarly, the 2 h walk reduced the post-prandial insulin response to a greater extent than the 1 h walk (17.3 vs 7.6%; P < 0.05 for trend). The results demonstrate that the beneficial effects of exercise on post-prandial metabolism are related to the duration and, therefore, the energy expenditure of the exercise session.

Moderate intensity exercise reduces postprandial triacylglycerol (TG) concentrations. We tested whether this reflects increased TG clearance.Eight normotriglyceridaemic men, aged 48·3 ± 7·3 years (mean ± SD), performed two oral fat tolerance tests (blood samples taken in the fasted state and for six hours after a high‐fat meal containing 1·00 g fat, 0·97 g carbohydrate, 58 kJ energy kg−1 fat‐free body mass) and two intravenous fat tolerance tests (blood samples in the fasted state and after a bolus injection of Intralipid, 0·1 g fat kg−1 body mass). The afternoon before one oral and one intravenous test, subjects walked briskly for 90 min; no exercise was performed before the control tests.Prior exercise reduced fasting TG concentration similarly in the oral (16 ± 7 %) (mean ± SEM) and intravenous (18 ± 7 %) tests, and reduced postprandial TG concentrations in the oral test by 18 ± 6 % (all P < 0·05). However, prior exercise did not increase Intralipid clearance (disappearance curve slopes: control, 4·69 ± 0·49 % min−1; exercise, 4·85 ± 0·40 % min−1).These data suggest that mechanisms other than increased TG clearance mediate the lower postprandial TG concentrations seen after moderate exercise.