• You Tao, PhD

5. Have You Achieved Physical Activity Level 1.7?

Updated: Apr 6

In post 4, you saw 10,000 steps/day came from a successful commercial campaign, and it translated into approximately 400 kcal for a hypothetical 40-year-old 70kg man with a resting metabolic rate at 3.5 ml oxygen/kg/min, if it was completed at a pace between 2.5~4mph on a level, firm surface.


How valid is 10,000 steps/day as a target and how effective is it? Physical activity level (PAL) measures the activity of a lifestyle. It is a better target and why?


Simon's Town, South Africa

1. Is the 10,000 steps/day target valid?

How much you would benefit from doing 10,000 steps a day depends on how many steps that give you over and above activities in the course of your daily living. In other words, you need to know how many steps you are already doing first.


This is simple. Wear an accelerometer or a pedometer for a few weeks and take the average.

The problem with translating how many steps a day into public health guideline is that the baseline level varies a lot in different populations.


8-10-year-old British children take 12,000~16,000 steps a day[1]. 6~12-year-olds in the US do between 11,000~13,000 according to a separate study [2]. Considering child obesity prevalence in both countries, children should not be restricted to 10,000 steps/day.


A meta-analysis into studies of healthy older adults returned a daily step range between 2,000-9,000. Since they are all healthy, they do not have to meet 10,000 steps daily target. In the same paper, the authors reported special populations (e.g. cancer survivors; people living with diabetes, COPD, coronary heart disease and related disorders, joint or muscle disorders) was in the range of 1,200-8,800, not too different from healthy older adults [3].


In short, one size does not fit all, and the 10,000 step/day index is not a public health recommendation.


2. Is the 10,000 steps/day target effective?

Although “10,000 steps a day” is not a public health recommendation, you may still wonder how effective it is for losing weight and improving health anyway?


To answer this question, a Japanese study recruited 730 volunteers among manufacturing workers into a 10,000 steps/day walking programme, all males aged 47 on average [4].


Japanese. Male. Manufacturing workers. The typical expectation is that this lot are stoic and mean business. What do you think that happened?


The study did confirm walking 10,000 steps/day or more was effective in lowering blood pressure. However, 306 made it after week 4, and only 83 remained in the study after 12 weeks [4]. That is 9 in 10 people dropped out in less than 3 months!


Simple, but not easy. “10,000 steps a day” is like many other things in real life. My speculation is that perhaps 70,000 steps a week is easier to achieve than this.


So if you want to convince your significant other to move a bit more, the strategy of “let’s get a Fitbit and reach for the 10,000 steps a day target together” is very likely to fail. Assuming you do not interfere with each other, the probability for that to happen is 0.1 x 0.1 x 100% = 1%! Frankly, if you have done it for more than half year, I salute you! Otherwise, I wouldn’t put my beer money on you achieving it!


The question is, is there a better alternative target?


3. Physical activity level (PAL) quantifies lifestyle and is related to health outcomes

26 years after the marketing of Manpo-kei along with the “10,000 steps” slogan, public health experts conceptualised “physical activity level” (PAL) in a FAO/WHO/UNU report in 1981.


PAL is the ratio between total energy expenditure (TEE) over energy for basal metabolism (BMR*24h). It is a dimensionless number and provides an important measure of a person’s daily physical activity. It considers walking, as well as 800 other types of activity, just about anything you would do in real life.


Classification of lifestyles using PAL [5]

It was first used by WHO to classify lifestyles into 3 types including “sedentary or light activity”, “active or moderately active”, “vigorous or vigorously active”.


4. Is my PAL < 1.7?

WHO gave some examples.


“Sedentary or light activity lifestyles: These people have occupations that do not demand much physical effort, are not required to walk long distances, generally use motor vehicles for transportation, do not exercise or participate in sports regularly, and spend most of their leisure time sitting or standing, with little body displacement (e.g. talking, reading, watching television, listening to the radio, using computers). One example is male office workers in urban areas, who only occasionally engage in physically demanding activities during or outside working hours. Another example are rural women living in villages that have electricity, piped water and nearby paved roads, who spend most of the time selling produce at home or in the marketplace, or doing light household chores and caring for children in or around their houses [5].


“Active or moderately active lifestyles. These people have occupations that are not strenuous in terms of energy demands, but involve more energy expenditure than that described for sedentary lifestyles. Alternatively, they can be people with sedentary occupations who regularly spend a certain amount of time in moderate to vigorous physical activities, during either the obligatory or the discretionary part of their daily routine. For example, the daily performance of one hour (either continuous or in several bouts during the day) of moderate to vigorous exercise, such as jogging/running, cycling, aerobic dancing or various sports activities, can raise a person’s average PAL from 1.55 (corresponding to the sedentary category) to 1.75 (the moderately active category). Other examples of moderately active lifestyles are associated with occupations such as masons and construction workers, or rural women in less developed traditional villages who participate in agricultural chores or walk long distances to fetch water and fuelwood [5].


“Vigorous or vigorously active lifestyles. These people engage regularly in strenuous work or in strenuous leisure activities for several hours. Examples are women with non-sedentary occupations who swim or dance an average of two hours each day, or non-mechanised agricultural labourers who work with a machete, hoe or axe for several hours daily and walk long distances over rugged terrains, often carrying heavy loads [5].”


If “sedentary or light activity” lifestyle applies to you, your family or your friends, you want pay extra attention to the next section.


5. Do I need to do anything if my PAL < 1.7?

In the 90’s and early 2000’s, public health researchers from many institutions around the world, including World Cancer Research Fund and American Institute for Cancer Research, studied the connection between different types of weight-related problems and lifestyle. There is consensus that a habitual PAL of 1.70 or higher is associated with a lower risk of overweight and obesity, cardiovascular disease, diabetes and several types of cancer [5].


Therefore, it is particularly important to recommend regular physical activity to populations and individuals with a sedentary or light activity lifestyle. Those with moderately or vigorously physically active lifestyles already have a habitual physical activity close to, or higher than, the health-associated PAL threshold of 1.70 times BMR. Recommendations for these individuals should be aimed at the maintenance of that activity level [5].


In summary, PAL is an important measure of lifestyle activity and you need to make conscious decisions if your PAL is less than 1.7. We will talk about the how you make sure your life has a PAL at 1.7 or more next week.


References:

1. Vincent SD, Pangrazi RP. An examination of the activity patterns of elementary school children. Pediatr Exerc Sci 2002; 14(4): 432-41

2. Cole TJ, Bellizzi MC, Flegal KM, et al. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 2000; 320 (7244): 1240-3

3. Tudor-Locke C et al. How many steps/day are enough? For older adults and special populations. Int J Behav Nutr Phys Act. 2011; 8:80.

4. Iwane M, et al. Walking 10,000 steps/day or more reduces blood pressure and sympathetic nerve activity in mild essential hypertension. Hypertens Res 2000; 23: 573-80

5. FAO/WHO/UNU. Human energy requirements: Report of a joint FAO/WHO/UNU expert consultation. Rome. 17-24 Dec 2001

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