The secret to easier exercise as an adult may start in childhood
Exercise during childhood could have a surprising lifelong benefit, potentially making physical activity less exhausting in adulthood. In a study involving guinea fowl, researchers discovered that birds accustomed to carrying weights while growing up could carry those weights as adults without using extra energy, while untrained birds burned 23% more.
Key points
- Penn State study used guinea fowl to test if early activity affects adult movement efficiency.
- Birds that carried weights as chicks used 23% less energy when walking with loads later.
- Researcher suggests childhood exercise could make exercise easier and more accessible for adults.
A new study led by researchers at Penn State suggests that physical activity during childhood may have lasting effects on how much energy the body needs to move as an adult. Using guinea fowl as a model, the scientists found the first direct evidence that developmental experiences can change adult movement efficiency. The findings were published in Proceedings of the Royal Society B, Biological Sciences.
The research involved attaching small weights to one leg of young guinea fowl to see if carrying extra weight during development would alter how efficiently the birds moved once mature. According to Jonas Rubenson, a professor of kinesiology at Penn State, the ability to move efficiently could play an important role in animal evolution, as animals that spend less energy getting around may have more resources for finding food, hunting, and reproducing.
How the experiment worked
The experiment followed 12 guinea fowl from two weeks of age until they reached 16 weeks. Half of the birds wore lead bands on one leg, each weighing 4% of the bird's body weight, while the other six developed without added weight. All birds experienced the same living conditions and exercise routines.
At nine weeks, the researchers began training the birds to walk on a treadmill. At 16 weeks, they assessed energy expenditure using a flow-through metabolic chamber fitted to the treadmill, measuring oxygen consumption and carbon dioxide production. Each bird was tested while standing still, walking without added weight, and walking with a weight band.
This study showed how limb loading -- the application of mechanical stress on arms or legs, typically through weights or exercise -- during development can help an animal save energy during movement throughout its lifespan.
— Jonas Rubenson
What researchers found
The researchers found no differences in energy consumption when the birds were standing still. However, birds that had not carried weights while growing up experienced a 23% increase in energy expenditure when walking with the added load compared with walking without it.
The birds that had worn weights throughout development showed a different response. Their bodies had adapted so effectively that walking with the extra load required slightly less energy than walking without it. On average, birds accustomed to carrying weights used no more energy while walking with their bands than ordinary birds used when walking without any added weight.
Implications for humans
Although the experiment involved birds, the findings raise questions about human physical activity. One widely accepted hypothesis proposes that people tend to avoid movement when it feels physically demanding or requires substantial energy. If early activity influences movement efficiency in humans as it does in these birds, people who were less active during childhood might need to expend more energy to perform the same movements as adults.
Rubenson believes the discovery could have broad implications for public health, particularly as children today are generally less physically active than those in earlier generations. He said, "This study suggests that more exercise through play and exercise during childhood could make it easier for people to remain or become more active as adults."
