High-impact weight-bearing activities such as running is better than non-weight-bearing exercises like cycling, increasing bone density and maintaining bone health in the long run, a study suggests.

Chronic bone resorption has been previously reported in a group of cyclists racing in ultra-endurance conditions. This process is involved in the weakening of bones by releasing the calcium from bone into the blood stream.

To test whether mountain ultra-marathon runners, another group of elite athletes, would have a similar response, researchers examined hormones (glucagon, leptin, and insulin) and plasma levels of two proteins associated with bone formation—osteocalcin and P1NP in 17 trained runners before and after a 65-km mountain ultramarathon run. The results were evaluated against the data on 12 adults of the same age who only did low-to-moderate physical activity.

Glucagon, leptin, and insulin are involved in regulating metabolism and indicate the energy needs of the body. Increased glucagon levels suggest an energy demand, whereas elevated insulin and leptin levels indicate adequate or excessive energy levels.

Ultramarathon runners had elevated levels of glucagon and lower levels leptin and insulin as they finished the race. The drop in insulin levels was similar to that observed in osteocalcin and P1NP levels, indicating that athletes may be redirecting energy from bone formation to fuel the high-energy demands of their metabolism.

In addition, the group also exhibited higher P1NP levels at rest compared to controls. This is indicative of a net gain in bone health in the long term.

“The every-day man and woman need to exercise moderately to maintain health,” said principal study author Dr. Giovanni Lombardi in a news release. “However, our findings suggest that those at risk of weaker bones might want to take up running rather than swimming or cycling.”

The impact of different exercises on bone health may be mediated by osteocalcin, a protein that plays a role in regulating the glucose metabolism of the body, Lombardi explained.

“Because running exerts a higher physical load on bone than swimming or cycling, it could be that these forces stimulate bone tissue to signal to the pancreas to help meet its energy needs in the long-term.”

The study highlights that bones are not lying idle, but are communicating actively with other organs and tissues to address the energy requirements of the body, Lombardi said.

“We often find that metabolic conditions and fracture risks are linked to the same underlying condition, so the more we learn about the interaction between bones and body metabolism, the better we will understand complex but important diseases such as diabetes and osteoporosis,” he added.

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