Recently, researchers at the Salk Institute for Biological Studies had published a study in the journal Cell on the results of a substance that increased exercise endurance without daily exertion when tested in mice.
Media reports have described this substance as an "exercise pill", potentially eliminating the need for exercise.
Now, Frank Booth, a University of Missouri expert on the science of inactivity, says the "exercise pill" study did not test all of the commonly known benefits of exercise and taking the pill cannot be considered a replacement for exercise.
In the Cell paper "Exercise Mimetics" the researchers demonstrated that AMPK-PPARd pathways, which is a cellular messenger system, can be targeted by orally active drugs to enhance training adaptation or even to increase endurance without exercise. However, Booth cautions that some of the commonly known benefits of exercise were not tested in the Cell paper including - decreased resting and submaximal exercise heart rate, increased heart stroke volume at all exercise work loads, increased maximal exercise cardiac output, lower blood pressure and arterial stiffness and increased aerobic capacity.
The prevention of the increased risk of chronic disease produced by lifelong physical inactivity also was not tested in the Cell paper.
Until targeting AMPK-PPARd pathways by drugs is shown to have all the above listed exercise benefits in humans, it is premature to use the term "exercise mimetics" from the very limited observations of the Cell paper, Booth said.
Booth's expectation, based upon his more than 40 years of research experience in exercise and physical inactivity adaptations, is that the drugs in the Cell paper will only partially imitate exercise. In order for any "exercise pill" to counter physical inactivity, the pill must be polygenic, or control many genes at once; therefore the Cell drugs are not likely to provide all of the benefits of comprehensive physical activity.
In Booth's opinion, the drugs used in the Cell paper were not conclusively proven to mimic exercise, contrary to media reports.