The 2008 Physical Activity Guidelines for Americans recommended a minimum
of 75 vigorous-intensity (7.5 metabolic-equivalent hours per week) or 150 moderate-
intensity minutes per week of aerobic activity for substantial health benefit
and suggested additional benefits accrue from doing more than double this amount.
However, it has not been entirely clear if there is an upper limit of health and longevity
benefit or if harm could occur with greatly increased levels of physical activity.

Using self-reported physical activity data from more than 650,000 individuals in
six studies in the National Cancer Institute Cohort, a study compared individuals
reporting no leisure-time physical activity to those with various multiples of the
recommended minimum to quantify the dose-response association between leisure-
time physical activity and mortality and define the upper limit of benefit or
harm associated with increased levels of physical activity. The study found a 20%
lower mortality risk among those performing some physical activity but less than
the recommended minimum of 7.5 metabolic-equivalent hours per week, a 31%
lower risk at one to two times the recommended minimum and a 37% lower risk at
two to three times the minimum. A ceiling for mortality benefit occurred at three to
five times the physical activity recommendation; however, compared with the recommended
minimum, the additional benefit was a modest 8% improvement (from
31% to 39%). There was no evidence of harm at 10 or more times the recommended
minimum. A similar dose-response relationship was observed for mortality due to
cardiovascular disease and cancer.

In summary, the study found the lowest risk of mortality among those who engaged
in 450 to 750 minutes of physical activities a week (an average of one to 1.8 hours
a day) of moderate- or half that amount of vigorous-intensity physical activities and
no excess risk, but no mortality gain at 10 or more times the minimum. The authors
concluded that meeting the 2008 Physical Activity Guidelines for Americans minimum
by either moderate- or vigorous-intensity activity was associated with nearly
the maximum longevity benefit.

However, as will be described in a future blog on physical activity and cardiovascular
disease, there is some evidence from studies of ultra-marathoners that it is
possible to “overdose” on exercise, and exceedingly high levels of physical activity
might harm health.

This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel.