Tendon Structure and Function

Tendon Structure and Function

• Tendons are connective tissues that attach muscle to bone.
• Their primary function is transferring force from muscles to the skeletal system, aiding in joint stabilization.
• Tendons are elastic, storing energy during short loading activities like jumping, to be released during the activity.

Relationship Between Stress and Deformation

• Tendon deformation relates to stress similarly to ligaments.
• Initially, collagen fibers within the tendon are easily stretched, exhibiting a wavy appearance.
• In the elastic zone, the tendon behaves like a spring.
• Ruptures in tendons initially affect individual fibers, then progress to complete ruptures within deformation zones.

Adaptation to Training

• Tendons adapt to training by increasing collagen synthesis and cross-link formation, similar to ligaments.
• Acute exercises increase collagen synthesis around tendon tissue.
• Changes in training intensity (increased/decreased), affect tendon mechanical properties within one to three weeks through altered cross-link formation.
• Changes in collagen-rich fibril structures require months to years to occur.

Tendon Injuries

• Tendons can be injured acutely (sudden) or through overuse.
• Acute injuries, often from forceful actions or trauma, can involve complete or partial ruptures.
• Tendon ruptures commonly involve high forces such as in eccentric contractions during high intensity sports.
• Overuse injuries can lead to inflammation and degeneration.

Overuse Injuries

• Tendons are frequently affected by overuse.
• Overuse injury can result in tendonitis (inflammation), tenosynovitis (sheath inflammation), tenoperiostitis (insertion and origin inflammation) and periostitis (periosteal inflammation).
• Bursitis (bursal inflammation possibly with bleeding) and haemobursitis (bursal inflammation possibly with bleeding, too) can also result from overuse.

Tendonitis vs. Tendinosis

• Tendonitis involves inflammation and irritation.
• Tendinopathy is tendon degeneration from long-term overuse and repetitive stress.

Muscle Structure and Function

• Muscles account for 40-45% of body mass.
• Muscle structure is designed to generate force.
• Muscle fibers (cells) are organized in different patterns, including unipennate, bipennate, multipennate, and fusiform arrangements.
• Pennate patterns offer strength, but contraction speed is lower, while fusiform patterns are faster.

Muscle Adaptation to Training

• Muscles show a rapid response to training.
• Muscle volume and strength significantly increase after a short period of strength-training.
• Both endurance (low intensity/high volume) and strength training contribute to improvements by improving the energy status of the working muscle which then impacts the ability to maintain higher strength for longer periods.

Muscle Injuries

• Muscle injuries occur as distension ruptures (pulled muscles/strains) or direct trauma (contusions).
• Lacerations can also happen.
• Hard or unusual training, particularly eccentric training, may lead to delayed-onset muscle soreness (DOMS).

Muscle Injury Healing Phases

• Muscle injury healing has three phases: inflammatory (destruction), proliferative (repair), and maturation (remodeling).