It is firmly believed that heavy weightlifting causes a somewhat greater splash of hormones compared to any other type of loads, let it be cardio exercise or pumping.
The statement that different forms of training affect our health differently is true, but we actually know surprisingly little more about it.
In a new study published in the scientific Journal of Clinical Investigation - Insight, researchers from the University of Copenhagen have come closer to understanding the diverse effects of different forms of training.
This study shows that cardio training on an exercise bike causes three times as large an increase in the production of the hormone FGF21 than strength training with weights.
In its turn, FGF21 has a lot of positive effects on metabolism.
"Of course it is very exciting for us researchers to see how different forms of physical activity actually affect the body differently. We have known about the effects of various forms of training on more well-known hormones like adrenalin and insulin for a long time, but the fact that strength training and cardio exercise affect FGF hormones differently is new to us", says one of the researchers behind the study - Associate Professor from the Novo Nordisk Foundation Center for Basic Metabolic Research Christoffer Clemmensen.
The research involved ten healthy young men, who had been randomly divided into two groups and did both forms of training once a week.
Both training forms were relatively hard and lasted 60 minutes. The cardio exercise consisted of cycling at a level of 70 percent maximum oxygen intake, while the strength training consisted of five exercises repeated 5 x 10 times and involving the main muscle groups in the body.
Measurements taken over a period of four hours revealed a significant increase in the production of the hormone FGF21 in connection with the cardio exercise, while strength training showed no significant change concerning this hormone.
"Endurance training on a bicycle has such a marked effect on the metabolic hormone that we know ought to take a closer look at whether this regulation of FGF21 is directly related to the health-improving effects of cardio exercise. FGF21's potential as a drug against diabetes, obesity and similar metabolic disorders is currently being tested, so the fact that we are able to increase the production ourselves through training is interesting," Christoffer Clemmensen elaborates.
Scientists were sure that strength training would affect another hormone FGF19. However, the results proved them wrong.
"Directly contrary to our hypothesis the production of the growth hormone FGF19 actually dropped slightly after strength training. To me, that stresses that there is something about the effect of strength training that we simply have too little knowledge of. And of course that gives rise to more research," says co-author of the study Jørn Wulff Helge, Professor of Physical Activity and Health at the Center for Healthy Aging and the Department of Biomedical Sciences.
The team of scientists also points out that they can say nothing about the effects of a full training programme on these hormones. However, the results, especially regarding the metabolic hormone FGF21, are so significant that they provide a solid foundation for studying whether similar effects can be seen in other groups of test persons.