# Injury Science and Tissue Healing · Triathlon Level 7: Upper-Advanced

Triathlon · Level 7: Upper-Advanced · Insporta Book (https://book.insporta.app/triathlon/level-7/injury-science-and-tissue-healing/)

Injury Science and Tissue Healing in Triathlon (Level 7: Upper-Advanced) on Insporta: 100 sourced facts behind 10 tests. Covers: phases of soft-tissue.

How tissues heal and fail: soft-tissue healing phases, bone remodelling and bone stress injuries, tendon structure and loading treatments, muscle strains and cramps, the load-capacity model and workload ratios, pain science, how injuries are studied, and overuse mechanisms in running and cycling.

## Test 1: Phases of Soft-Tissue Healing

- Healing runs through overlapping phases: inflammation (days), proliferation or repair (weeks), then remodelling (months). (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Fibroblasts lay down new collagen and new capillaries form over roughly the first few weeks. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Early repair tissue is rich in thinner type III collagen, gradually replaced by stronger type I during remodelling. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Remodelling realigns and strengthens collagen along the lines of load, a process that runs for months to over a year. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Collagen fibres orient in response to mechanical load, so graded loading produces a better organised, stronger repair. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Dubois and Esculier proposed PEACE (first days) and LOVE (after) in 2020 to update RICE and POLICE with load and education. (Source: Dubois & Esculier, Br J Sports Med 2020)
- Inflammation is part of repair, and anti-inflammatories may impair long-term tissue healing, especially at higher doses. (Source: Dubois & Esculier, Br J Sports Med 2020)
- Ice can relieve pain short term, but there is little high-quality evidence that it improves healing, and it may blunt inflammation. (Source: Dubois & Esculier, Br J Sports Med 2020)
- Mechanical load promotes repair and tissue capacity, so normal activity returns as soon as symptoms allow. (Source: Dubois & Esculier, Br J Sports Med 2020)
- Pain settles long before collagen has matured; tensile strength keeps recovering for months. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))

## Test 2: Bone Remodelling and Adaptation

- Osteoclasts resorb bone; osteoblasts then lay down new bone in the same spot. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Osteoblasts form new bone matrix, which later mineralises. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Bone remodels to match the mechanical demands on it, adding mass where loads are high. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Remodelling removes bone first and refills it over months, leaving a window of reduced strength. (Source: Warden et al., Curr Osteoporos Rep 2014)
- A full cycle of resorption, reversal and formation lasts several months in adult bone. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Bone responds best to high, fast, varied strains; breaking loading into bouts with rest improves the response. (Source: Robling et al., J Bone Miner Res 2002)
- Non-weight-bearing sports provide little osteogenic stimulus, so athletes relying on them can have low bone density. (Source: Scofield & Hecht, Curr Sports Med Rep 2012)
- Most bone mass is gained by the end of adolescence; peak is reached in the twenties. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Vitamin D increases calcium absorption; deficiency is linked to higher bone stress injury risk. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Frost proposed that bone senses strain and adds or removes mass when strain moves above or below set thresholds. (Source: Frost, Anat Rec 1987)

## Test 3: Bone Stress Injuries

- Repeated loading beyond repair capacity causes a spectrum from bone marrow oedema to a complete fracture line. (Source: Warden et al., Curr Osteoporos Rep 2014)
- Early X-rays miss most bone stress injuries; changes may appear only after two to three weeks as healing bone forms. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- MRI shows bone marrow oedema early and allows the injury to be graded. (Source: Fredericson et al., Am J Sports Med 1995)
- Fredericson graded tibial stress injuries on MRI from periosteal oedema to a visible fracture line. (Source: Fredericson et al., Am J Sports Med 1995)
- High-risk sites (femoral neck, navicular, anterior tibia, fifth metatarsal base) heal poorly and can displace or fail to unite. (Source: Warden et al., Curr Osteoporos Rep 2014)
- Sites under tension or with poor blood supply risk non-union or displacement, sometimes needing surgery. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- An anterior tibial cortex fracture line signals a high-risk injury with a real risk of non-union. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Navicular stress fractures are high-risk because of the bone's poor central blood supply. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Posteromedial tibial and most metatarsal shaft injuries are low-risk and usually heal with load modification. (Source: Warden et al., Curr Osteoporos Rep 2014)
- Low energy availability suppresses bone formation, a major modifiable risk factor for bone stress injury. (Source: Mountjoy et al., Br J Sports Med 2023 (IOC REDs consensus))

## Test 4: Tendon Structure and Tendinopathy

- Tendon is dense connective tissue made largely of parallel type I collagen fibres. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Chronic tendon pain shows disorganised matrix rather than classic inflammation, so "tendinopathy" is preferred. (Source: Khan et al., BMJ 2002)
- The model places tendinopathy on a continuum from reactive tendinopathy through tendon dysrepair to degeneration. (Source: Cook & Purdam, Br J Sports Med 2009)
- Acute overload, such as a jump in volume or a return to hills or speed, triggers the reactive stage. (Source: Cook & Purdam, Br J Sports Med 2009)
- Tendon matrix turns over slowly, so tendons lag behind muscles when load increases quickly. (Source: Magnusson et al., Nat Rev Rheumatol 2010)
- The Achilles stretches as the foot lands and recoils at push-off, saving metabolic energy. (Source: Alexander, J Exp Biol 1991)
- Peak Achilles forces in running reach roughly six to eight times body weight. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- A stiffer tendon lengthens less for a given force, transmitting muscle force faster. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Tendons respond to high loads with greater stiffness and, over time, some increase in size. (Source: Bohm et al., Sports Med Open 2015)
- The mid-portion, about 2-6 cm above the insertion, has a relatively poor blood supply and is where most tendinopathy occurs. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))

## Test 5: Loading Treatments for Tendon Pain

- Alfredson prescribed 3 x 15 eccentric heel drops with straight and bent knee, twice daily, for 12 weeks. (Source: Alfredson et al., Am J Sports Med 1998)
- HSR uses heavy loads with slow concentric and eccentric phases, usually three sessions a week. (Source: Kongsgaard et al., Scand J Med Sci Sports 2009)
- Both groups improved similarly at 12 weeks and one year; patient satisfaction tended to be higher with HSR. (Source: Beyer et al., Am J Sports Med 2015)
- A single session of heavy isometrics reduced pain for at least 45 minutes; later studies found the effect less consistent. (Source: Rio et al., Br J Sports Med 2015)
- Continuing to run was allowed if pain stayed at or below 5/10 and did not increase the next morning. (Source: Silbernagel et al., Am J Sports Med 2007)
- Tendons need load to maintain their properties; prolonged rest reduces stiffness and capacity. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Their 2010 Lancet review found injections helped in weeks but were linked to poorer results and more recurrence later. (Source: Coombes et al., Lancet 2010)
- The large ATM trial found no benefit of PRP over placebo injection for chronic Achilles tendinopathy. (Source: Kearney et al., JAMA 2021)
- Tendon cells respond to mechanical load by remodelling matrix; passive options at best ease symptoms. (Source: Cook & Purdam, Br J Sports Med 2009)
- A next-morning rise in pain or stiffness is the key sign the previous load exceeded tendon tolerance. (Source: Silbernagel et al., Am J Sports Med 2007)

## Test 6: Muscle Strains and Cramps

- The myotendinous junction is the weakest link in the muscle-tendon unit under eccentric load. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- In late swing the hamstrings decelerate the shank while lengthening, the moment of highest strain risk. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Programmes including Nordic hamstring exercises reduced hamstring injury rates by roughly 50%. (Source: van Dyk et al., Br J Sports Med 2019)
- BAMIC grades 0-4 plus a, b or c; "c" injuries extend into the tendon and take longer to return from. (Source: Pollock et al., Br J Sports Med 2014)
- Injuries involving the tendon within the muscle have longer return times and higher re-injury rates. (Source: Pollock et al., Br J Sports Med 2014)
- Medial gastrocnemius strains ("tennis leg") are typical of middle-aged and older athletes. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Schwellnus and others argue fatigue-related neuromuscular changes explain cramps better than dehydration or electrolyte loss alone. (Source: Schwellnus, Br J Sports Med 2009)
- Cramps eased in about 85 seconds, too fast for absorption, suggesting a reflex from the mouth or throat. (Source: Miller et al., Med Sci Sports Exerc 2010)
- Passive stretching reduces the abnormal nerve activity driving the cramp. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Incomplete rehabilitation leaves weaker, less extensible tissue, raising the risk of re-injury. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))

## Test 7: Load, Capacity and the Workload Ratio

- Tissues fail when applied load outstrips their current capacity; training should raise capacity faster than load. (Source: Bertelsen et al., Scand J Med Sci Sports 2017)
- It compares, for example, the last week's load with the average of the last four weeks. (Source: Gabbett, Br J Sports Med 2016)
- Gabbett suggested injury risk was lowest when the ratio stayed around 0.8-1.3 and rose above about 1.5. (Source: Gabbett, Br J Sports Med 2016)
- Critics showed mathematical coupling, poor statistical properties and little evidence it predicts injury in individuals. (Source: Impellizzeri et al., Int J Sports Physiol Perform 2020)
- Novices following a 10%-per-week build had similar injury rates to a group progressing faster. (Source: Buist et al., Am J Sports Med 2008)
- Runners who increased weekly volume by more than 30% had more distance-related injuries than those under 10%. (Source: Nielsen et al., J Orthop Sports Phys Ther 2014)
- Incidence across studies ranged from about 19% to 79%, most often in the lower limb, especially the knee. (Source: van Gent et al., Br J Sports Med 2007)
- Capacity depends on training history, body mass, biomechanics, sleep, energy and more, so identical loads land differently. (Source: Bertelsen et al., Scand J Med Sci Sports 2017)
- Load is tissue-specific; cycling and swimming hours put little impact through the tibia. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Rapid, unaccustomed increases in load, rather than high load itself, are most strongly linked to injury. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))

## Test 8: Pain Science

- Pain is produced by the brain in response to perceived threat and is shaped by context, not a readout of tissue damage. (Source: Moseley & Butler, J Pain 2015)
- Nerve signalling of potential harm can occur without pain, and pain can occur without nociception. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- The central nervous system amplifies signals, so normal inputs can hurt more and pain spreads. (Source: Woolf, Pain 2011)
- Disc degeneration appeared in 37% of pain-free 20-year-olds and 96% of pain-free 80-year-olds. (Source: Brinjikji et al., AJNR Am J Neuroradiol 2015)
- Mild, settling pain during graded rehabilitation does not necessarily mean further damage. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Fear of pain leads to avoidance, deconditioning and often more pain and disability. (Source: Vlaeyen & Linton, Pain 2000)
- Sleep loss lowers pain thresholds and stress amplifies pain processing. (Source: Finan et al., J Pain 2013)
- A bout of exercise usually lowers pain sensitivity for a while afterwards. (Source: Rice et al., J Pain 2019)
- Teaching patients the biology of pain can reduce pain and disability, especially combined with exercise. (Source: Louw et al., Physiother Theory Pract 2016)
- Rotator cuff tears are frequent in pain-free people, so scan findings must be matched to symptoms and examination. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))

## Test 9: Studying Injuries: Definitions and Evidence

- Incidence counts new cases over a period, often expressed per 1,000 hours of exposure. (Source: Bahr et al., Br J Sports Med 2020 (IOC consensus))
- Prevalence captures all current cases, new and ongoing, which suits overuse problems. (Source: Bahr et al., Br J Sports Med 2020 (IOC consensus))
- Many overuse problems reduce performance without stopping training, so they escape a time-loss count. (Source: Clarsen et al., Br J Sports Med 2013)
- The Oslo Sports Trauma Research Center questionnaire records participation, modified training, performance and pain each week. (Source: Clarsen et al., Br J Sports Med 2013)
- Previous injury is the most consistently reported predictor of a new running injury. (Source: van der Worp et al., PLoS One 2015)
- Normalising by exposure time allows comparison of groups with very different training volumes. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Observational data show association; confounding factors may explain the link. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Randomisation balances known and unknown confounders between groups. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Fokkema and colleagues found the online programme did not reduce injuries in recreational runners. (Source: Fokkema et al., Br J Sports Med 2019)
- Multifactorial causes, low event rates and poor adherence make prevention effects hard to detect. (Source: Bahr et al., Br J Sports Med 2020 (IOC consensus))

## Test 10: Overuse Mechanisms in Running and Cycling

- Fairclough showed the band is anchored to the femur and cannot slide; compression of richly innervated tissue is the likely cause. (Source: Fairclough et al., J Anat 2006)
- Exercise therapy targeting hip and knee muscles is recommended to reduce pain and improve function. (Source: Crossley et al., Br J Sports Med 2016)
- Heel raises with a towel under the toes gave better results at three months than plantar fascia stretching. (Source: Rathleff et al., Scand J Med Sci Sports 2015)
- MTSS causes diffuse pain along the posteromedial tibia; focal tenderness suggests a bone stress injury. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Pressure on the ulnar nerve in Guyon's canal causes numbness and weakness in the ring and little fingers. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Saddle pressure on the perineum can compress the pudendal nerve and reduce blood flow. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Repeated hip flexion in an aero position can thicken the artery wall, causing one-sided leg pain and weakness at high power. (Source: Peach et al., Eur J Vasc Endovasc Surg 2012)
- At low power the flow needed passes the narrowing; at high power it cannot, so symptoms appear. (Source: Peach et al., Eur J Vasc Endovasc Surg 2012)
- Repeated impact and eccentric loading in running stress bone and tendon far more than cycling. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))
- Lateral knee pain aggravated by downhill running, around 30 degrees of knee flexion, is typical of ITBS. (Source: Brukner & Khan, Clinical Sports Medicine (5th ed.))

Sources: Peer-reviewed exercise physiology and sports medicine literature, with standard textbooks for settled facts

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