Exercise Adaptation / Injury Prevention Tidbits

Dealing with Injury

Dumbbell Seated Shoulder External RotationImmediately stop an exercise that causes the joint or muscle unusual pain. Do not test or stretch the muscle since further damage could occur. Regardless of the findings the initial treatment remains the same. Administer first aid. Allow time for the joint or muscle to heal as you continue to workout using exercises that do not further aggravate the injury during its recovery. After sufficient recovery time, start back very conservatively with a single set or brief bout with very light resistance. Continue to slowly progress steadily, increasing the load or volume throughout the following weeks, only if you can perform the load pain free. Be cautious not to aggravate the injury by attempting to progress too rapidly. Be aware that it is possible to not feel pain or discomfort after over doing it until after the workout or the next day - after it is too late. See a physician for serious injuries or if the pain persists or gets worse. A sports medicine physician specializes in exercise and athletic related injuries. A physical therapist should also be able to refer you to a physician knowledgeable in exercise related injuries for proper diagnosis. A specialist can help you determine possible underlying causes of the injury and make necessary program modifications to prevent future injuries. See Adaptation Criteria and Causes of Injury.

Injury Rehabilitation Phases

  1. Immobilization
  2. Range of motion (ROM)
  3. Strength
  4. Return to activity

Bomgardner R (2001) Rehabilitation phases and program design for the injured athlete. Strength and Conditioning Journal, 23(6): 24-25.

  • Inflammation Phase
    • First aid and Immobilization
    • Manage inflammation
    • Lasts days
  • Repair Phase
    • Rehabilitative exercises
    • Fibroplasia (formation of collagen)
    • Angiogenesis (formation of new local blood vessels)
    • Lasts weeks
  • Remodeling Phase
    • Conservative reintroduction of activity
      • progressive increases of intensity and volume
    • Collagen maturation and remodeling initiate
    • Lasts months

Evans P (1980). The healing process at cellular level: a review. Physiotherapy, 66(8): 256-259

Irritability Scale

Irritability can be rated Low, Medium, or High based on 3 factors:

  • Pain level (Score of 1-10)
  • What it takes to provoke the symptoms
  • Latency or time it takes the symptoms to resolve after provocation

Care must be taken when assessing patients of high irritability because once symptoms are provoked, the remaining assessments are unclear.

Tovin BJ (2006). Prevention and Treatment of Swimmer's Shoulder. North American Journal of Sports Physical Therapy, 1(4): 166-175.

Strength Imbalance and Injury Relationship

Individuals with strength differences of more than 10% between the quadriceps of the right and left legs were more likely to sustain lower limb injuries compared to individuals without such strength imbalances (Bender et al, 1964).

If these strength differences were due to past injury, one could speculate that previous injury at least partly attributed to increased the risk of injury, not necessarily the strength imbalance itself, since past injury is most predictive of future injury (see studies below) and past injury typically results in weakness (and decreased range of motion) in the injured limb.

Ankle Sprain Predictors

BMI and past ankle sprains were much more predictive of future injury in high school athletes than were balance, height, ligamentous laxity, ankle tape/bracing usage, and hip strength balance. High school football players were 16 times more likely to sustain an ankle sprain if the athlete was overweight or obese and had a history of ankle sprain. Incidentally, the use of preventive taping or bracing did not reduce the incidence of injury.

Mirabella MR, Tyler TF & McHugh MP (2004) Risk Factors for Ankle Sprains in High School Football Players. Journal of Athletic Training. Supplement 39(2), 38.

Tyler TF, McHugh MP & Tetro (2004) Risk Factors for Ankle Sprains in High School Athletes. Journal of Athletic Training. Supplement 39(2), 37.

Past Distal Injuries Delay Proximal Muscular Activation in Both Affected and Unaffected Limbs

Bullock-Saxton (1994) found a delay in Gluteus Maximus activity in individuals with a previous injury to the ankle. Changes appeared to occur in both the previously injured and uninjured sides of the body.

Bullock-Saxton JE, Janda V, Bullock MI (1994). The Influence of Ankle Sprain Injury on Muscle Activation During Hip-extension. Int J Sports Med. 15(6): 330-334.

Exercise & Arthritis

Exercise can decrease pain and improve functional capacity, ROM, and muscular strength

Felson DT, Lawrence RC, Hochberg MC, McAlindon T, Dieppe PA, Minor MA, Osteoarthritis: New insights. Part 2. Treatment approaches. Ann Intern Med. 133: 726-737, 2000.

Casper JM, Berg K. Effects of exercise on osteoarthritis: A review. J Strength Cond Res. 12: 120-125, 1998.

Foot Parts

The human foot has 26 bones, approximately 20 muscles, 33 joints, and over 100 ligaments holding it all together.

Connective Tissue Sheaths

Connective Tissue Sheaths

Weight training may strengthen the sheaths of connective tissue within and around the muscle by increasing their collagen content. These connective tissues sheaths provide the framework that supports muscle overload and are the main component in the tensile strength and passive viscoeclastic properties of muscle.

  • endomysium surrounds individual fibers
  • perimysium encloses groups of muscle fibers
  • epimysium surrounds the entire muscle


Tensile strength and elasticity of bones decrease about 2% per decade from age 20 to 90 years (Hayes, 1986).

Bone is only one fifth the weight of steel but can withstand two times the compression force as granite, or four times the compression force as concrete.

Weight bearing activities such as walking can prevent bone mineral loss. Weight resistive exercises can prevent bone mineral loss if the antigravity musculature is activated.

In animal studies, the first 40 repetitions of an exercise stimulate greater than 95% of bone formation. Additional repetitions do not significantly increase bone formation (Riewald 2004).

Astronauts have about the same rate of bone loss as those on bed rest: about one percent per month.

Riewald S (2004). Bone of Contention: What Exercises Increase Bone Strength? Strength and Conditioning Journal. 26(1): 46-47.

Joint Cartilage

Joint Cartilage

Resistance training can thicken the hyaline cartilage on the articular surfaces of the bone (Ingelmark & Elsholm 1948).

Joint cartilage depends on synovial fluid for its nutrition since it has no vascularization. Synovial fluid is forced into the cartilage surfaces when the joint is loaded, as in physical activity. Joint cartilage functions in an elastic manner during short term loading. The cartilage becomes temporarily deformed when long term loading forces water out of the cartilage. It returns to its original shape after cessation of loading when water is again drawn into the cartilage. The alternate compression and decompression along with the pumping of synovial fluid due to physical activity is partly responsible for nutrition to the cartilage.

Chondrocyte response to mechanical stimulation contributes to the maintenance of articular cartilage homeostasis. Articular chondrocyte metabolism is modulated by direct effects of shear forces that act on the cell through mechanotransduction processes. (Lane Smith 2000)

The cartilage of immobilized joints undergo atrophy when subjected to reduced loading. Cartilage thickness is only partially restored with exercise. (Gahunia 2012)

Joint loading on cartilage results in anabolic effects which are least partially, mediated by alterations in the synovial fluid. The composition of the synovial fluid reflects the combined extracellular pathways of all articular tissues. (Van den Hoogen 1998)

Regular exercise alters synovial fluid in such a way that it has a favorable effect on cartilage proteoglycans content, one of the main matrix components and of importance to the physical properties of cartilage.  It does this by enhancing the proteoglycans synthesis and reducing the proteoglycans breakdown. Many possible candidates, including IGF-I and IGF-II, could potentially contribute to the loading effect. (Van den Hoogen 1998)

Gahunia HK, Pritzker KPH (2012) Effect of Exercise on Articular Cartilage, Orthopedic Clinics; 43(2),  187–199.

Ingelmark BE, Elsholm R (1948). A study on variations in the thickness of the articular cartilage in association with rest and periodical load. Uppsala Lakaretorenings Foxhandlingar;53: 61–64.

Lane Smith R, Trindade MC, Ikenoue T, Mohtai M, Das P, Carter DR, Goodman SB, Schurman DJ (2000). Effects of shear stress on articular chondrocyte metabolism. Biorheology;37(1-2): 95-1.

Van den Hoogen BM, van de Lest CH, van Weeren PR, Lafeber FP, Lopes-Cardozo M, van Golde LM, Barneveld A (1998). Loading-induced changes in synovial fluid affect cartilage metabolism. Br J Rheumatol;37(6): 671-6.

Tendon and Ligament

Resistance training can increase the size and strength of tendons and ligaments (Fahey et al. 1975). This may be due to an increase of collagen within the connective tissue sheaths (Laurent 1978).

The elastic limit of a tendon or ligament can be enhanced by exercise and training and can be reduced by aging and inactivity. The elastic limits of ligament are estimated to be 12-50%, and the elastic limits of tendon is 9-30% (Weakest at MTJ).

Research using animal models demonstrates that junction strength of ligaments increases with endurance-type physical activity and decreases with immobilization. Furthermore, damaged ligaments regain strength faster if physical activity is performed afterwards.

Junction strength failure of a bone-ligament preparation occurs at the attachment site of the ligament. The Junction strength failure is similar in a bone-tendon-muscle-tendon-bone preparation, although separation may also occur at the muscletendinous junction or in the muscle itself.

Tendons exhibit viscoelastic properties and are adaptive to conditions of increased loading and disuse. Strains within the tendons near their insertion site do not appear to be uniform. The traditional concept of tensile failure may not be the essential factor in the pathomechanics of insertional tendinopathy. Particular joint positions are more likely to stress the area of the tendon usually affected by tendinopathy. Incorporating different joint position during exercise may allow for more controlled stresses on these affected areas of the tendon which may allow for better maintenance of the mechanical strength of that tendon region in effort to prevent injury. Such exercises could stress a healing area of the tendon in a controlled manner thereby stimulating healing once an injury has occurred. (Maganaris 2004)

Also see Ligament Elasticity comment and Pectoralis Major Tears.

Fahey TD, Akka L, Rolph R (1975). Body composition and Vo2max of exceptional weight-trained athletes. J Appl Physiol. 39(4):559-61.

Laurent GJ, Sparrow MP, Bates PC, Millward DJ (1978). Turnover of muscle protein in the fowl. Collagen content and turnover in cardiac and skeletal muscles of the adult fowl and the changes during stretch-induced growth. Biochem J. 176(2):419-27.

Maganaris CN, Narici MV, Almekinders LC, Maffulli N (2004). Biomechanics and pathophysiology of overuse tendon injuries: ideas on insertional tendinopathy. Sports Med. 34(14):1005-17.


As with all living tissue, the vertebrae and its supporting structures remodel and strengthen when subjected to stress such as progressive exercise (Brickley-Parsons & Glimcher 1984).

Movement of the spine under load facilitates nutrient delivery to the intervertebral discs (Gullbrand 2015), alters disk PH levels (Tatsuro 1993), and may mitigate inflammation (Sowa & Agarwal 2008).

Performing spinal exercises through a full range of motion can increase and maintain functional spinal flexibility (Contreras & Schoenfeld 2011) and spinal stability thereby decreasing risk of low back pain (Nelson 1993, 1995).

Also see Low Back Debate.

Brickley-Parsons D and Glimcher MJ (1984). Is the chemistry of collagen in intervertebral discs an expression of Wolff's Law? A study of the human lumbar spine. Spine (Phila Pa 1976) 9: 148-163.

Contreras B, Schoenfeld B (2011). To Crunch or Not to Crunch: An Evidence-Based Examination of Spinal Flexion Exercises, Their Potential Risks, and Their Applicability to Program Design. Strength and Conditioning Journal; 33(4), 8-18.

Gullbrand SE, Peterson J, Ahlborn J, Mastropolo R, Fricker A, Roberts TT, Abousayed M, Lawrence JP, Glennon JC, Ledet EH (2015). Dynamic Loading–Induced Convective Transport Enhances Intervertebral Disc Nutrition. Spine; 40(15): 1158-1164.

Nelson BW, O'Reilly E, Miller M, Hogan M, Wegner JA, Kelly C (1995). The clinical effects of intensive, specific exercise on chronic low back pain: a controlled study of 895 consecutive patients with 1-year follow up. Orthopedics, 18(10), 971-981. (PDF)

Nelson BW (1993). A rational approach to the treatment of low back pain. J Musculoskel Med, 10(5), 67-82. (PDF)

Sowa G, Agarwal S (2008). Cyclic tensile stress exerts a protective effect on intervertebral disc cells. Am J Phys Med Rehabil; 87(7), 537-44.

Tatsuro K (1993). Biochemical changes associated with symptomatic human intervertebral discs. Clinical Orthop. 298: 372-377.

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