Osteoporosis...the mere mention of the word conjures up the image of a gray-haired, bent-over, little old lady. Yet many athletes, particularly endurance athletes, female and male, are being diagnosed with osteoporosis and osteopenia in their twenties, thirties and forties. There are many factors that contribute to bone loss in endurance athletes, but calcium loss through sweat appears to play a significant role. In a landmark study by Klesges, (JAMA July 1996) he set out to determine if there was a relationship between sweat and bone loss. Klesges asked a university basketball team to wear cotton shirts during their practices. He then extracted the sweat from the shirts and measured the calcium content. Klesges calculated the players were losing 422 mg of calcium in three days of practice. He measured the bone density of the team and found the average player lost 3.8% of bone mineral density during a 3 month season. The players were then given a calcium supplemented sports drink and at the start of the next season the players had gained an average of 2% in bone mineral density.
Running, surprisingly, is linked to decreased bone density, despite being a weight-bearing activity. A study published in the British Journal of Sports Medicine found that the more a woman ran the lower her bone density. Each extra 10km run per week resulted in 1-2% lower bone density. Another study found that women who exercise for just one hour daily lose about 92 mg of calcium a day through sweat. Marathons and Ultramarathons require hours of training. In a 100 mile race a runner will be on the trail for over 24 hours! Cyclists will spend hours sweating in the saddle. The hours spent in a minimal weight-bearing activity, combined with calcium loss can lead to a significant decrease in bone density. A study of 4 Tour de France racers revealed a 25% loss of their spinal bone mass.
Here in the Pacific NW long distance running and cycling are popular activities. Numerous races such as the Seattle to Portland bike ride and Seattle Marathon attract thousands of athletes every year. It takes hours to train and participate in these events. Calcium depletion through sweat loss, inadequate food intake, and overtraining, all contribute to bone loss. To help offset these factors cyclist and runners should be encouraged to add weight-lifting to their work out routines. Lifting weights places a stress on bones that will result in increased bone strength. The weight has to be heavy enough to stress the bones, which means lifting 2 sets of 8-10 with weight heavy enough that it is difficult to complete the second set. Sufficient calcium intake includes the daily requirement, plus an additional 100-200mg of calcium for every hour of exercise over 2 hours (heavy sweaters may require up to 300mg/hr). It is easy to carrying a calcium supplement or calcium enriched sports drink while running or cycling for long distances.
If you would like help setting up a cross-training and weight-lifting program or you just want to learn exercises to help build your bones, please call and set up an appointment.