Maturation, ageing, and exercise effects on tendons and ligaments Flashcards
Maturation of tendon & ligaments
- Maturation - dramatic increase in mechanical properties of tendon/ligaments (strength, stiffness) (up to skeletal maturity)
- Ageing - more gradual decrease in mechanical properties
- Altered mode of failure – avulsion more common in children/adolescents than adults
What did they find? Maturation of tendon
- Patellar tendon in adults is larger & stiffer than in children
- Increased collagen fibril diameter
- Increased cross sectional area
- Tendon stiffness did not differ between men and women or between boys and girls
Maturation of tendon & ligament
- Asynchronous maturation of mid- substance and bone-tendon (or bone- ligament) junction
- Prior to skeletal maturity, strength of MCL substance > bone-ligament junction > failure by tibial avulsion
- After skeletal maturity > failure in ligament substance
Sever’s disease
- Calcaneal apophysitis – inflammation of growth plate
- Affects children 8-11 years
- Overuse problem – exacerbated by running, jumping (squeeze test)
Osgood schlatter disease
- Tibial tuberosity apophysitis
- Overuse problem – aggravated by jumping or running
- More common in boys (although gender gap reducing with increasing participation by girls in sports)
- Affects boys 13-14 and girls 11-12
imbalanced adaptation btwn muscle and tendon in teenage athletes
• 19 adolescent volleyball players (avg 16yrs); 18 adults (avg 47yrs) previous volleyball (MRI and ultrasound)
• Knee ext torque & PCSA of quadriceps similar for adolescent & adults
• Patellar tendon CSA lower in adolescents than adults (+ higher stress at
max force)
• Non-uniform adaptation of muscle and tendon in young athletes results in inc tendon stress during late adolescence
– muscles get stronger but tendon doesn’t get thicker
Can strength training help to even out the mismatch between muscle and tendon properties in children?
- Tendon stiffness (∼29% ) increased and Young’s modulus (∼25%) increased
- A decrease electromechanical delay ∼13% for the RT group
ageing
lifestyle
diet
environment
Effects of age - Muscle
•decrease muscle mass (sarcopenia)
• decrease number and size of muscle fibres > atrophy
• Conflicting results for proportion of type I & II fibres
• Neuromuscular changes – decrease capacity to detect info and activate muscles (motor units remodel)
Strength decreases can be partly offset by resistance exercise
• In active older adults, biochemical properties of remaining muscle mass are well maintained
start to see decline at 45 yo
self-renewal potential
decrease self-renewal potential in tendons in comparison to muscle
Effects of age – Achilles tendon loses stiffness
- Older tendons were 15% more compliant than younger tendons
- decrease contractile force
- decrease rate of force development
- Implications for falls ?
- Inconsistent findings of effects of ageing on tendon mechanical properties
- older tendons don’t tend to rupture
Effects of age – patellar tendon
Exercise training in older adults increased stiffness of patellar tendons
• But is increased stiffness linked to increased capacity to move (ie: walking ability)?
Exercise training in older adults
- Active participation in exercise tends to lessen the impact of ageing on performance
- Reduces age-related loss of muscle mass and bone mineral density • Neural adaptation (plasticity)
- Improves quality of life and health
- Helps prevent falls
- Cannot stop ‘healthy’ biological ageing but can markedly reduce many of the decrements in physical capacity with exercise!
Gender differences in tendon properties
- Previously thought that males have stiffer tendons than females
- Males tend to be stronger than females
- We found that Achilles tendon stiffness is linked to strength but not to gender
Gender differences in ligament properties
• Female athletes are at a 4 times ↑ risk of sustaining a non-contact ACL injury than males.
• Why?
• Increased participation of females in sport
(title IX in USA)
• Strength imbalance between quads and hams
• Neuromuscular strategy (less hamstrings activation)
• Different mechanical properties (from cadaveric study)
Specificity of exercise
- Exercise can induce tendon hypertrophy and increase tendon stiffness
- Effects vary for different types and intensities of exercise
- Consider direction of loading
- Consider magnitude of loading
- Time course varies for different tissues
- Consider de-training effects
Effects of load magnitude- Achilles tendon
- Increase in stiffness,elastic modulus, size of AT only in high magnitude load
- Low strain exercise may be insufficient trigger for tendon adaptation
Effects of duration – older adults
- Increase in stiffness, modulus, size of AT only in high magnitude load after 14 weeks
- No further improvement after 1.5 years
- AT is sensitive on narrow time scales – even at older ages
THEREFORE MAXIMISE EFFECTS AT SHORT TIME PERIODS
Achilles and patellar tendons behave differently under similar jump training protocols
AT increase strain with added mass but opp. to patella
Effects of detraining of tendon
- tendons take longer to adapt but quicker to detrain
• After a period of sudden detraining, physical activity should berestarted with caution and with appropriate rehabilitation programs.
*** Summary of effects of exercise type on tendon
- Exercise Type
- Endurance ∞ stiffness
- Stretching decreases stiffness
- Isometric exercise/Concentric, eccentric resistance/ Plyometric - increase stiffness
- For adaptation of tendon mechanical properties, need:
- High loads
- High tendon strains
- If isometric, be performed at long muscle lengths 9( don’t want tendons to be slack at short lengths)
- Be performed consistently for at least 8 weeks (up to 12-14 w)
Mechanotransduction
“How precisely does exercise promote tissue adaptation?”
1. The mechanical trigger
2. Communication throughout the tissue to distribute the loading message
3. Tissue factory (produces /assembles tissue)
• Cell signaling at each stage enables this process
Mechanotherapy = turning movement into tissue healing
tendons adapt slowly due to mechanotransduction
