Physical Activity Can Protect Your Joints

Written by LTC Timothy Benedict, Physical Therapist

Not "Wear and Tear": Physical Activity Can Protect Your Joints!

As a 40-year-old Army Physical Therapist with 18 years in the Service, I am so thankful for the benefits that Army training has provided my body and joints.  As a former infantry Soldier, I am thankful for the long runs and foot marches, the 100-pound ruck, for Ranger School and airborne jumps.  Why?  According to some public health experts, progressive strenuous exercise—especially during our younger years—provides a lifetime of health benefits like stronger bones and cartilage^1-4.  New research is confirming that maintaining an active lifestyle throughout your lifespan is quite safe and beneficial for the body⁵.

"Wait a minute," you may ask, "Doesn't all that strain cause 'wear and tear' on your body?"  According to a recent scientific study: no, not really.  In fact, the opposite may be true.  Researchers in Germany who studied healthy individuals for over 14 years found that those who engaged in the highest amounts of physical activity had fewer changes in magnetic resonance imaging (MRI) of their spines compared to less active individuals⁶.  These changes are usually associated with the normal aging process⁷, but appear to slow down with increased physical activity.

Of course there are some limitations to the German MRI study.  The participants in this research weren't Soldiers.  Also, although the German MRI study showed that being sedentary was associated with increased signs of aging in the spine, the design of the research cannot prove physical inactivity caused the changes to the spine.  Despite the reassuring findings from this MRI study, is understandable that some Soldiers may worry they get too much activity since some research identifies elite running mileage as a risk factor for injuries⁸.  The average Soldier, however, competes at a much lower running mileage than elite athletes⁹.  This type of recreational running has actually been shown to protect the knee and hip joints from osteoarthritis⁸.

So rather than "wear and tear," a more accurate description of the effect of physical activity may be "repetition and condition."  In other words, when your body undergoes regular, progressive exercise, your tissues adapt and become more conditioned^1,10.  Research shows that active individuals have healthier, stronger joints compared to those who are sedentary^11-14.  Tissues positively adapt to the mechanical loads and stresses from regular physical training^1,10,15. 

Of course, more is not always better, especially if your body is not used to an activity.  Excessive physical overload can lead to an over-use injury.  These types of injuries are common in the military and among athletes¹⁶.  If you have experienced an injury—like falling, twisting, or doing too much activity that your body was not conditioned for—and you have treated your injury with relative rest for 4-6 weeks but continue to have problems, then it is time to get help from a healthcare provider.  The good news is that most of these injuries heal.  Even worrisome injuries such as disc herniations, meniscal tears, and cartilage damage^17-19 often heal well.  Healing may take a long time and may require periods of relative rest and activity modification following an injury.  After a serious injury, it is not realistic to expect to be 100% symptom-free, but the human body can achieve a new normal.  Individuals can be highly active even following major injuries^20,21. 

Since over-use injuries are so common in the military¹⁶, it may seem that doing less activity will protect your body and joints.  The German MRI study showed that too little activity, however, can be just as unhealthy for your body as too much activity⁶.  This explains why astronauts returning from space have weakened tissues and bones: their bodies face too little stress when living without gravity²². 

It is best to train smartly and gradually build up your tissue conditioning and avoid these types of injuries in the first place.  Here are some general tips that can help prevent overuse injuries:

• Follow a progressive plan.  Many researchers recommend keeping training increases (distance, weight, or intensity) to around 10% a week²³.  Take it a little easier every 4^th week of regular training²⁴.
• Keep an eye on signs of over-training: difficulty sleeping, persistent feelings of fatigue, easy to catch illnesses²³.  
• Change things up.  A healthy body regularly changes how it moves to help manage stress and load^25-27. 
• Ensure adequate sleep and nutrition^23,28-31.
• Engage in progressive, balanced strength-training³².
• Remember, the human body is incredibly resilient and capable of adapting to the physical demands of military service and beyond^20,21.  These adaptations take time, however!

Army training is tough, but so is the human body.  Scientific research is discovering more and more that regular physical activity does not necessarily result in harmful "wear and tear" on your body^1,33.  Injuries are possible, but tissues heal and the benefits of physical activity—like better cardiovascular health and longer life⁵—far outweigh the risks.  With progressive repetition, your tissues will become conditioned³⁴.  The benefits of being highly active will stay with you for life, especially if you maintain a healthy lifestyle.

Scientific Support

1. Miller RH. Joint loading in runners does not initiate knee osteoarthritis. Exercise and sport sciences reviews. 2017;45(2):87-95.
2. Antony B, Jones G, Venn A, et al. Childhood Physical Performance Measures and Adulthood Knee Cartilage Volume and Bone Area: A 25‐Year Cohort Study. Arthritis care & research. 2015;67(9):1263-1271.
3. Milgrom C, Simkin A, Eldad A, Nyska M, Finestone A. Using Bone's Adaptation Ability to Lower the Incidence of Stress Fractures. The American Journal of Sports Medicine. 2000;28(2):245-251.
4. Borer KT. Physical Activity in the Prevention and Amelioration of Osteoporosis in Women. Sports Medicine. 2005;35(9):779-830.
5. Saint-Maurice PF, Troiano RP, Bassett DR, et al. Association of daily step count and step intensity with mortality among US adults. Jama. 2020;323(12):1151-1160.
6. Maurer E, Klinger C, Lorbeer R, et al. Long-term effect of Physical Inactivity on Thoracic and Lumbar Disc Degeneration–a MRI Based Analysis of 385 individuals from the general population. The Spine Journal. 2020.
7. Daimon K, Fujiwara H, Nishiwaki Y, et al. A 20-year prospective longitudinal study of degeneration of the cervical spine in a volunteer cohort assessed using mri: follow-up of a cross-sectional study. JBJS. 2018;100(10):843-849.
8. Alentorn-Geli E, Samuelsson K, Musahl V, Green CL, Bhandari M, Karlsson J. The association of recreational and competitive running with hip and knee osteoarthritis: a systematic review and meta-analysis. journal of orthopaedic & sports physical therapy. 2017;47(6):373-390.
9. Grier TL, Canham-Chervak M, Anderson MK, Bushman TT, Jones BH. Effects of physical training and fitness on running injuries in physically active young men. The Journal of Strength & Conditioning Research. 2017;31(1):207-216.
10. Miller RH, Krupenevich RL. Medial knee cartilage is unlikely to withstand a lifetime of running without positive adaptation: a theoretical biomechanical model of failure phenomena. PeerJ. 2020;8:e9676.
11. Van Ginckel A, Baelde N, Almqvist K, Roosen P, McNair P, Witvrouw E. Functional adaptation of knee cartilage in asymptomatic female novice runners compared to sedentary controls. A longitudinal analysis using delayed Gadolinium Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC). Osteoarthritis and cartilage. 2010;18(12):1564-1569.
12. Urquhart DM, Tobing JF, Hanna FS, et al. What is the effect of physical activity on the knee joint? A systematic review. Medicine and science in sports and exercise. 2011;43(3):432-442.
13. Teichtahl AJ, Wluka AE, Forbes A, et al. Longitudinal effect of vigorous physical activity on patella cartilage morphology in people without clinical knee disease. Arthritis Care & Research. 2009;61(8):1095-1102.
14. Teichtahl AJ, Urquhart DM, Wang Y, et al. Physical inactivity is associated with narrower lumbar intervertebral discs, high fat content of paraspinal muscles and low back pain and disability. Arthritis research & therapy. 2015;17(1):114.
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16. Hauret KG, Jones BH, Bullock SH, Canham-Chervak M, Canada S. Musculoskeletal injuries: description of an under-recognized injury problem among military personnel. American journal of preventive medicine. 2010;38(1):S61-S70.
17. Macki M, Hernandez-Hermann M, Bydon M, Gokaslan A, McGovern K, Bydon A. Spontaneous regression of sequestrated lumbar disc herniations: Literature review. Clinical neurology and neurosurgery. 2014;120:136-141.
18. Messner K, Maletius W. The long-term prognosis for severe damage to weight-bearing cartilage in the knee: a 14-year clinical and radiographic follow-up in 28 young athletes. Acta Orthopaedica Scandinavica. 1996;67(2):165-168.
19. Pujol N, Beaufils P. Healing results of meniscal tears left in situ during anterior cruciate ligament reconstruction: a review of clinical studies. Knee Surgery, Sports Traumatology, Arthroscopy. 2009;17(4):396-401.
20. Goggins D. Can't Hurt Me. Master your Mind and Defy the Odds. Lioncrest Publishing; 2018.
21. Soong K. Veteran who lost both legs completes 31 marathons in 31 days, runners trailing his every step. Washington Post. 2017.
22. VANDENBURGH H, CHROMIAK J, SHANSKY J, DEL TATTO M, LEMAIRE J. Space travel directly induces skeletal muscle atrophy. The FASEB Journal. 1999;13(9):1031-1038.
23. Roy BA. Overreaching/overtraining: more is not always better. ACSM's Health & Fitness Journal. 2015;19(2):4-5.
24. Heard C, Willcox M, Falvo M, Blatt M, Helmer D. Effects of Linear Periodization Training on Performance Gains and Injury Prevention in a Garrisoned Military Unit. Journal of military and veterans' health. 2020;28(3):23.
25. Hamill J, van Emmerik RE, Heiderscheit BC, Li L. A dynamical systems approach to lower extremity running injuries. Clinical biomechanics. 1999;14(5):297-308.
26. Hamill J, Palmer C, Van Emmerik RE. Coordinative variability and overuse injury. Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology. 2012;4(1):1-9.
27. Brown C, Bowser B, Simpson KJ. Movement variability during single leg jump landings in individuals with and without chronic ankle instability. Clinical biomechanics. 2012;27(1):52-63.
28. Forsyth C, Kouvari M, D'Cunha NM, et al. The effects of the Mediterranean diet on rheumatoid arthritis prevention and treatment: a systematic review of human prospective studies. Rheumatology international. 2018;38(5):737-747.
29. Sofi F, Cesari F, Abbate R, Gensini GF, Casini A. Adherence to Mediterranean diet and health status: meta-analysis. Bmj. 2008;337.
30. Genel F, Kale M, Pavlovic N, Flood VM, Naylor JM, Adie S. Health effects of a low-inflammatory diet in adults with arthritis: a systematic review and meta-analysis. Journal of nutritional science. 2020;9.
31. Grier T, Dinkeloo E, Reynolds M, Jones BH. Sleep duration and musculoskeletal injury incidence in physically active men and women: A study of US Army Special Operation Forces soldiers. Sleep health. 2020.
32. Lauersen JB, Andersen TE, Andersen LB. Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries: a systematic review, qualitative analysis and meta-analysis. British journal of sports medicine. 2018;52(24):1557-1563.
33. Shrier I. Muscle dysfunction versus wear and tear as a cause of exercise related osteoarthritis: an epidemiological update. British journal of sports medicine. 2004;38(5):526-535.
34. Hohmann E, Wörtler K, Imhoff AB. MR imaging of the hip and knee before and after marathon running. The American journal of sports medicine. 2004;32(1):55-59.