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Friday, September 30, 2011

Low Bone Mass in ROAD Cyclists and Ways to Fix it

It may come to a surprise that many professional road cyclists are at risk for osteoporosis.  Even with their amazing endurance and the ability to maintain very high average speeds, the combination of endurance training and non weight-bearing exercise is a recipe for reduced bone mass density (BMD) (2).  In a study by Bryant et al, 30 professional road cyclist (~29 years old) were compared to 30 young healthy males of similar age.  When comparing BMD values from multiple sites, they found that professional road cyclists had a similar head BMD, but lower values in the following locations:
  1. Arms
  2. Legs
  3. Spine
  4. Pelvis
  5. Lumbar Spine
  6. Femoral neck (most affected site -18%)
Road cyclists who neglect strength training are at risk for osteoporosis and may already be osteopenic:
Another study produced similar results.  Smathers et al. measured total body, lumbar spine and proximal femur BMD in male competitive road cyclist and compared their values to age-/ body mass-matched controls.  Despite having at least 9.4 years of racing experience and 7-22 hours per week of training, the cyclist's t-scores indicated that 9% of the cycling group and 3% of the control group were classified as osteoporotic (5).  In terms of osteopenia, 25% and 10% of the cycling and control group, respectively, were osteopenic (5).

Greater Problem with Master Road Cyclists
Differences in BMD was even more prominent when master cyclists were compared to age matched controls.  In a study performed by Nichols et al, master cyclists with a minimum of 10 years of training who performed little weight-bearing exercise were measured at the spine and total hip.  Both sites were significantly lower compared to the age matched controls.  This study showed that although the master cyclist were highly trained and physically fit, they were still at risk for developing osteoporosis with advancing age (4).


Mountain Cyclists vs. Road Cyclists
I want to emphasize that decreased bone mass density was found only in road cyclist who performed little to no weight bearing exercises.  Mountain cyclist may not have to worry about low bone mass density.  In a study specific to mountain cyclists, BMD values at the proximal femur, lumbar spine and the total body were higher than the controls (7).  The sharp forces experienced through mountain biking may provide the stimulus necessary to cause bone to adapt.


Runners vs Cyclists
Running was associated with increased bone density, especially in the leg (6).  Again, cycling was associated with a mild decrease in BMD of the total body and lumbar disks L1-L4 (6).  The results suggested that impact activities such as running, plyometrics and power exercises may generate loads several times the body weight- enough strain to stimulate adaptation of the bone (2,6).


Ways to Improve BMD
The thought of weight lifting always seem to scare road cyclists.  Many fear that heavy weight lifting will enhance strength and cause them to lose muscular endurance.  In fact, an exercise program that includes heavy weight lifting and aerobic exercise can actually improve endurance in elite athletes (8).  As I described in a separate post about lifting weights to improve endurance, heavy weight lifting recruits both slow and fast twitch muscle fibers.  For this reason among others, there is a strong relationship between muscular strength and endurance.  This means that lifting heavy weights to improve strength will also improve endurance- the opposite is true.

Here are a some ways to improve BMD through exercise:
  • Include heavy weight lifting (at least 8 RM) to a cycling program or any load that is greater than what's encountered on a daily basis (2).
  • Perform strength exercises standing such as squats, lunges, long jumps, box jumps, etc.
  • Use free weights or a weighted vest at 7-15% body weight (2).
  • Emphasize on exercises that improve muscular strength and power (2)
  • Try group exercise classes that improves muscular strength (aerobic, boot camp, zumba, etc.)
  • Plyometrics.  Studies have shown that even simple jumping exercises may increase bone mass, especially at the hip (9,10,11,12).
If spine BMD or bone status are unknown, see these exceptions to the suggestions above:
  • Avoid heavy loads (>10% body weight) (2).
  • Avoid high impact plyometrics (>2.5 times body weight)
  • Avoid loads greater than 8RM

References:
  1. Applied anatomy and biomechanics in sport. New York: Blackwell Scientific Publications, 1994. Print.
  2. Bryant, Cedric X., and Daniel J. Green. ACE advanced health & fitness specialist manual: the ultimate resource for advanced fitness professionals. San Diego: American Council On Exercise, 2008. Print.
  3. Campion, F., A.M. Nevill, M.K. Karisson, J. Lounana, M. Shabani, P. Fardellone, and J. Medelli. "Bone Status in Professional Cyclists."International Journal of Sports Medicine Sep. 2010: 511-515. Print.
  4. Nichols, Jeanne, Jacob Palmer, and Susan Levy. "Low bone mineral density in highly trained male master cyclists."International Osteoporosis Foundation and National Osteoporosis Foundation July 2003: 644-649. Print.
  5. Smathers, Aaron, Michael Bemben, and Debra Bemben. "Bone Density Comparisons in Male Competitive Road Cyclists and Untrained Controls."Medicine & Science in Sport & Exercise Feb. 2009: 290-296. Print.
  6. Stewart, Arthur, and James Hannan. "Total and regional bone density in male runners, cyclists, and controls."Medicine & Science in Sports & Exercise Aug. 2000: 1373-1377. Print.
  7. Warner, S.E., J.M. Shaw, and G.P. Dalsky. "Bone mineral density of competitive male mountain and road cyclists."Bone Jan. 2002: 281-286. Print.
  8. Hickson R., Dvorak B., Gorostiaga E., Kurowski T. & Foster C. (1988) Potential for strength and endurance training to amplify endurance performance. Journal of Applied Physiology 65, 2285-2290.
  9. Bassey, E.J. & Ramsdale, S.J. (1994). Increase in femoral bone density in yound women following high impact exercise. Osteoporos International, 4, 2, 72-75.
  10. Bassey, E.J. et al. (1998). Pre- and postmenopausal women have different bone mineral density responses in the same high-impact exercise. Journal of Bone Mineral Research 13, 12, 1805-1813.
  11. Heikkinen, R. et al. (2007). Acceleration slope of exercise-induced impacts is a determineant of changes in bone density. Journal of Biomechics. 40, 13, 2967-2974.
  12. Winters, K.M. & Snow, C.M. (2000). Body composition predicts bone mineral density and balance in premenopausal women. Journal of Women's Health and Gender-Based Medicine, 9, 8, 865-872.