Are Endurance Sports Bad for Your Bones?
Over the past decade there has been a tremendous increase in the number of adults participating in age group endurance sports. Many take up sports to experience the joy of competition against others; some take it up as a challenge for themselves and still others take up endurance sports as a means of improving their health, quality of life, and fitness.
While there are definite benefits to being physically active and training for races can provide the motivation many need to lead an active lifestyle every activity that we do does carry some risk and competitive endurance sports may not be the best choice for those with bone density issues (BMD).
In developing countries the incidence of osteoporosis is increasing at a rate faster than what would be predicted by the aging of the population alone. It has been estimated that by 2025 the number of hip fractures in the U.S. will double to nearly 2.6 million with a greater percentage increase in men than in women. Hip fractures not only have an impact on quality of life and long term mobility but there is up to a 33% mortality rate in the first year following a hip fracture.
Endurance training can be an acceptable form of exercise for maintaining or increasing bone density in middle aged or older adults provided there is sufficient impact and the training volume is not too high. Swimming, cycling and walking have been shown to have little effect on bone density compared to controls. This is due to the lack of impact forces experienced during these activities. Stuart and Hannan (Med. Sci. Sports Exerc., vol 32: pp1373-1377; 2000) examined the effects of cycling, running or both on bone density in recreational male athletes. They found that runners had greater total and leg BMD than controls, those athletes participating in both cycling and running had greater total arm BMD whereas the cyclists had decreased spine BMD compared to controls even though all groups performed equal volumes of work throughout the study period.
Rowing because of the high compressive and shear forces placed on the spine, 4.6 times body weight, has been shown to increase lumbar spine BMD but not at other areas (Morris et al, International Journal of Sports Medicine. Vol 21:pp 518-523, 2000).
Running has mixed effects on bone density depending on total training volume. Running mileage of 20-30 km per week has a positive effect on bone, particularly lower leg and distal femur, but training volumes greater than this may create a chronic increase in cortisol that negatively impacts bone (Chilibeck, Sale, and Webber, 1995). In males running 92 km per week bone density has been found to be lower than sedentary controls (Bilanin, Blanchard, and Russek-Cohen, 1989). This equates to just over 8 hours of training per week if you have an average running speed of 11 km/hr.
It is not uncommon for age group runners, cyclists and triathletes to train at least 8 hours per week and often as much as 15 hours per week when preparing for longer distance events. While these volumes of training are necessary to compete in endurance sports there are a couple of things that you can do to decrease the negative impact endurance training can have on bone density:
1. Strength train
Strength training can increase bone density and help maintain muscle mass. Add 2-3 strength sessions per week to your program all year round. While some complain that they don’t have time there is a fair amount of research suggesting that replacing some endurance work with strength training actually improves endurance performances more than the endurance work alone.
2. Eat enough
One of the biggest contributors to decreased bone density is a negative energy balance, that state where you are burning more calories than you are taking in. Make sure you are fueling and refueling properly before during and after training.
Endurance sports, like all activities, have both positive and negative consequences; the key to enjoying a healthy sporting life is to find the right balance and minimize the negative consequences.