A QUESTION

The street in front of our house turns sharply and soon my wife and I are punishing the drive train of our tandem up a 12% grade.  At a combined weight of 330lbs and a combined continuous rep pull-up max of 35 reps, we clearly aren’t your average bike monkeys. Nay, we are the larger, slower moving apes of the cycling world.

A spindly 130lb man flies past us up the hill with a weathered face that could say either 50+ years or 500,000 miles on a bicycle. He is clearly the master of this hill. His chiseled quads don’t look weak, but as a physical therapist, I wonder about his bones. I have heard of professional cyclists having low bone density and shattering hips on falls that wouldn’t have broken the average person’s bones. I’ve heard that because of the high cadence even a power output of 300w only produces about 100lb of force per stroke; less bone-stimulating weight bearing force than walking. But what does the research say? Is cycling bad for your bones?

SOME BACKGROUND

Bone is living tissue, it is constantly being broken down and rebuilt, piece by piece. Cells called osteoclasts eat away at the bone and cells called osteoblasts make new bone. Over the course of 7-10 years the entire bone will be replaced.  The balance of bone breakdown and bone rebuilding is determined by internal and external factors. Low bone density is called osteopenia, dangerously low bone density is called osteoporosis. Here are some of the most important factors:

Internal:

• Estrogen promotes more bone growth, a drop in estrogen results in a drop in bone density.
• Cortisol results in a reduction in bone growth and thus prolonged cortisol results in lowering bone density. Cortisol is the hormone released when the body is under stress.
• Age: After around age 30, slightly more bone is broken down than rebuilt and bone density declines with age.
• Diet: If one doesn’t eat enough calcium (<1000mg/day), or doesn’t get enough vitamin-D (<600 IU/day)  to absorb the calcium, there simply isn’t enough to make new bone out of.
• Genetics: Genetic factors affect

External:

• Repetitive impact such as running or weight lifting breaks down bone, but this same impact signals the osteoblasts to make more bone and they usually end up making more than was damaged. The larger the weight (including the body weight), the more impact and thus the more bone growth.

SOME DATA

To answer my questions about bone density and cycling I searched through google scholar and PubMed until I found a Systematic Review on Cycling and Bone Health published in 2012 by Hugo Olmedillas and his research group in Spain [1]. They group examined all of the recent research and came to these conclusions

It’s True

People who just ride a road bike all the time, really do have worse bone density and it only gets worse with time

• 2/3 of the professional and master adult road cyclists could be classified as osteopenic [2]
• Both in professional and recreational cyclists, bone density has been found to be lower than in the general population [3,4]
• Nichols compared cylists to age-matched non-athletes. The cyclists lost more bone density over the course of the seven year study [4]
• Bone density in competitive cyclists gets worse as the racing season progresses [5]
• Low levels of bone density earlier in life may contribute to dangerously low levels (osteoporosis) later in life [6]

 

 

 

The Frenchman Brice Feillu won stage 7 of the Tour De France in 2009.

 

 

 

Some impact is better than none.

Almost any exercise is better for your bones than just endurance cycling (except maybe swimming).

• Wilks et all found that sprint trained cyclists had higher bone density than endurance trained cyclists [7]
• Mountain bikers have been found to have better bone density than road cyclists. [13]
• Weightlifting builds bone density more than anything else [8].
• Duathletes and Triathletes had higher bone density than those who only did endurance cycling. [1]
• Adolescent runners had better bone density than their peers who were cyclists or non-athletes [9].

Nutrition

You can’t just take extra calcium to get stronger bones. But a greater % of fat in the diet might help.

• Barry et al. tried to stave off the decline in bone density by giving a group of cyclists extra calcium but although it change their calcium levels after exercise, it didn’t improve their bone density [11].
• Brown et al. showed a small uptick in bone density in the group that ate a higher percentage of their diet as fat for 12 weeks, with no difference in body mass or fat between groups [12].
• Although factors such as nutrition and endocrine (ie cortisol levels from the stress of long rides) are beginning to be studied in cyclists, initial results haven’t shown levels far enough from normal to explain the low bone density [1].

 

 

Photo taken in Burundi by adventure cyclists Peter Gostelow

 

 

 

Calcium is like the bricks, impact is like the blueprints. Send extra bricks to the construction site but no orders and nothing extra gets built. Except maybe a kidney stone…[10]

 

APPLICATION

Cycling itself doesn’t reduce your bone density, it just doesn’t do anything to help your bone density, and if cycling is all you are doing then you aren’t doing much to help your bone density. 

How to help your bone density.

• Adequate nutrition: 1000mg of calcium and 600U of vitamin D. Don’t remove fat from your diet.
• Weight bearing activity. Running, jumping and weight lifting are the most effective.

The catch:

The very same weight bearing exercise that builds bone density can cause fractures in those with very poor bone density when given in excessive doses.

The Solution:

If road cycling has been your exclusive form of exercise for more than a few years I recommend contacting your doctor to get your bone density checked. This is especially important if you have a history of smoking, are Asian or Caucasian, over age 60 and light.  Then connect with a physical therapist to get exercises that will safely improve your bone density.

REFERENCES

 

1. Olmedillas H, Gonzalez-Aguero A, Moreno LA, Casajus JA, Vicente-Rodriquez G. Cycling and Bone Health: A Systematic Review. BMC Medicine. 2012. 10.168
2. Medelli J, Lounana J, Menuet JJ, Shabani M, Cordero-MacIntyre Z: Is osteopenia a health risk in professional cyclists? J Clin Densitom 2009, 12:28-34
3.  Nichols JF, Palmer JE, Levy SS: Low bone mineral density in highly trained male master cyclists. Osteoporos Int 2003, 14:644-649.
4.  Nichols JF, Rauh MJ: Longitudinal changes in bone mineral density in male master cyclists and nonathletes. J Strength Cond Res 2012, 25:727-734.
5. Barry DW, Kohrt WM: BMD decreases over the course of a year in competitive male cyclists. J Bone Miner Res 2008, 23:484-491.
6. Rizzoli R, Bianchi ML, Garabedian M, McKay HA, Moreno LA: Maximizing bone mineral mass gain during growth for the prevention of fractures in the adolescents and the elderly. Bone 2010, 46:294-305.
7.  Wilks DC, Gilliver SF, Rittweger J: Forearm and tibial bone measures of distance- and sprint-trained master cyclists. Med Sci Sports Exerc 2009, 41:566-573.
8.  Heinonen A, Oja P, Kannus P, Sievanen H, Manttari A, Vuori I: Bone mineral density of female athletes in different sports. Bone Miner 1993, 23:1-14.
9.  Duncan CS, Blimkie CJ, Kemp A, Higgs W, Cowell CT, Woodhead H, Briody JN, Howman-Giles R: Mid-femur geometry and biomechanical properties in 15- to 18-yr-old female athletes. Med Sci Sports Exerc 2002, 34:673-681.
10. Curhan GC, Willett WC, Rimm EB, Stampfer MJ. A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones.
11.  Barry DW, Hansen KC, van Pelt RE, Witten M, Wolfe P, Kohrt WM: Acute calcium ingestion attenuates exercise-induced disruption of calcium homeostasis. Med Sci Sports Exerc 2011, 43:617-623
12.  Brown RC, Cox CM, Goulding A: High-carbohydrate versus high-fat diets: effect on body composition in trained cyclists. Med Sci Sports Exerc 2000, 32:690-694.
13.  Warner SE, Shaw JM, Dalsky GP: Bone mineral density of competitive male mountain and road cyclists. Bone 2002, 30:281-286