Active Voice: How Many Steps Per Day is Healthy, Even When You Exercise Regularly?
By Ed Coyle, Ph.D., FACSM

Epidemiological studies often measure all-cause mortality. A recent study found lower death rates in people taking 8,000 versus 4,000 steps/day. This is important, but there is more to the story.

It is also known that people who meet the 2018 Physical Activity Guidelines (150 to 300 minutes a week of moderate-intensity or 75 to 150 minutes a week of vigorous-intensity aerobic physical activity) can still be at elevated risk for disease and death if they are also sedentary for most of the day. Simply put, it appears that the good of physical activity can be overcome, to some extent, by the bad of prolonged sitting and inactivity.

In our study that published in the February 2021 issue of Medicine & Science in Sports & Exercise®, our premise was that unhealthy and yet unknown phenomena occur when people are inactive. We used step counts per day to evaluate inactivity seeking to determine what is too low.

The main metabolic health benefits of acute exercise are largely gained in one to two days through cellular adaptations that improve metabolism and/or cardiovascular function. We took the approach of altering physical activity (step count) levels for a few days in young healthy individuals. Thereafter, we determined if they adapted in a healthy way the day after a one-hour bout of running (65% V̇O2max). We chose to monitor fat metabolism because of its relevance to health. Also, because improvements in postprandial plasma triglyceride levels and whole-body fat oxidation should occur, if healthy, the day following one hour of running.

Our study had subjects take either approximately 2,500, 5,000 or 8,500 steps/day on the days prior to the bout of running. Following the two lowest step counts, the postprandial increase in plasma triglyceride was elevated an unhealthy 22% to 23%, compared to when taking 8,500 steps/day (p<0.05). Along the same lines, whole body fat oxidation was significantly lower and unhealthy (16% to 19%, p<0.05, respectively) when taking 2,500 and 5,000 steps/day compared to 8,500 steps/day. We have termed the inability of a one-hour bout of exercise to improve fat metabolism as exercise resistance due to inactivity.

In practical terms, reducing physical activity to approximately 5,000 step/day and below in young healthy individuals impairs the ability of an exercise bout to improve fat metabolism the next day. The same deleterious responses were seen with both 2,500 and 5,000 steps/day. Thus the dose response was not linear. Taking 8,500 steps/day appears to promote a healthy improvement in fat metabolism. However, we don’t know about the effectiveness of step counts in the range of 5,000 to 8,500 steps/day.

Taken together, it seems that reduced contractile activity for long periods of the day causes a condition in which current physical activity recommendations may not be as effective as needed for deriving some of the protective health benefits. Methods for reducing inactivity throughout the day obviously would result in increasing daily step counts. Additionally, we recently reported that if prolonged sitting throughout the day is interrupted hourly by 20-seconds of maximal cycling (five times of 4-second bouts), that exercise resistance can be prevented at least in terms of fat metabolism. When inactive at home, work or school, people need to include bouts of exercise/activities to remain healthy.

About the author:
Ed Coyle, Ph.D., FACSM, has directed the Human Performance Laboratory at the University of Texas-Austin for the past 38 years. Before that, he received graduate and post-doctoral training at Ball State University, the University of Arizona and Washington University Medical School (St. Louis). Dr. Coyle’s laboratory has studied the metabolic and cardiovascular factors that regulate endurance performance. His study of athletes might be thought of as reverse engineering with insights that can be applied for improving the health and performance of the general population. Dr. Coyle has been an ACSM member for more than 40 years and received ACSM’s prestigious Citation Award in 2006.

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