Running, may improve long-term bone health more effectively than non weight-bearing activities like cycling.

The authors of a new study measuring the hormones of mountain ultra-marathon runners said exercise that puts greater strain on bones such as running may be the answer to long-term bone health.

Previous research from the Istituto Ortopedico Galeazzi in Milan found that cyclists racing in ultra-endurance conditions suffered chronic bone resorption – where calcium from bone is released into the blood stream, weakening bones.

In this study, the same group set out to find whether a similar group of elite athletes – mountain ultra-marathon runners – had the same response.

Researchers measured two vital bone constituents as well as hormones associated with energy regulation. Osteocalcin and P1NP are two proteins associated with bone formation and their levels in blood are an indicator of bone health.

Glucagon, leptin and insulin are hormones involved in regulating metabolism and indicate the body’s energy needs. Increasing glucagon levels indicate an energy demand, whilst increasing insulin and leptin levels indicate adequate or excessive energy levels.

The researchers measured these three hormones as well as levels of osteocalcin and P1NP in 17 trained runners before and after a 65-km mountain ultra-marathon run and compared it to the hormones and bone constituents of 12 adults of the same age who didn’t run the race but did low to moderate physical exercise.

Compared to the control group, ultra-marathon runners had higher levels of glucagon and lower levels of leptin and insulin when finishing the race. The falling levels of insulin within this group were linked to similarly falling levels of both osteocalcin and P1NP – suggesting that athletes may be diverting energy from bone formation to power the high-energy demands of their metabolism.

However, ultra-marathon runners had higher P1NP levels at rest compared to controls, suggesting that they may divert energy from bones during racing but have a net gain in bone health in the long-term.

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

One theory that could explain the effect of different exercises on bone formation is the role of osteocalcin, explains Lombardi.

“Previous studies have shown that osteocalcin communicates with beta cells in the pancreas, which regulate the body’s glucose metabolism,” said Lombardi. “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.

“Our work has shown that bones aren’t just lying idle but are actively communicating with other organs and tissues to drive the body’s energy needs,” he added.

“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.”

In a related study released last month, Spanish researchers have analysed the effect of endurance running training on the stiffness index, a variable that is directly related to bone quality.

The results confirm that the greater the race distance that is trained, the better; this can be used, therefore, to prevent the progressive decline in bone mineral density that occurs with age.

In healthy individuals, bone quality – chiefly determined by bone mineral density – depends on factors such as sex, age, race and diet. It can be modified, however, by making lifestyle changes – for instance by doing regular exercise.

Meanwhile, a new study, led by researchers from Camilo José Cela University (UCJC), determines how training to compete in endurance races (from 10 km to marathons) can modify the mechanical properties of the calcaneus, a bone in the foot that forms the heel.

The changes in the mechanical properties of the bone were measured using the stiffness or rigidity index, a variable that is directly related to the bone density of the calcaneus.

During the study, bone densitometries – or bone density tests – were performed on both the right and left feet of 122 marathon runners and 81 half marathon and 10km runners, and their values were compared to those of a control group of sedentary individuals of a similar age.

“The results showed that the endurance runners had a greater stiffness index than the sedentary individuals,” as explained by Beatriz Lara, the main author of the study and a member of the Exercise Physiology Laboratory at UCJC.

The improved stiffness index was observed in both the male and female runners.