Stress and Adaptation in Exercise

1. Stress and Adaptation in Exercise

2. Stress • An agent, process, or condition that produces a demand on the body • Stress is difficult to define in an exact sense but is recognized by its effects. • Examples: • Fatigue and muscle soreness produced by exercise • Fever and other responses to illness • Behavioral changes produced by emotional stress

3. Types of Stress • Distress (“Dis” comes from a Latin term meaning bad.) – Produces negative results • Eustress (“Eu” comes from a Greek term meaning good.) – Produces positive results • The body has the same basic responses to distress and eustress. However, distress tends to produce more damage.

4. General Adaptation Syndrome • The response of the body to stress • Has three stages: • Alarm Reaction • Resistance • Exhaustion

5. Stages of the General Adaptation Syndrome • Alarm Reaction • The body’s first response to stress • Produces the “fight or flight” reaction • Cannot be sustained for very long

6. Stages of the General Adaptation Syndrome • Resistance • The body begins to change to accommodate the stress • Important for being able to withstand stress for an extended period of time

7. Stages of the General Adaptation Syndrome • Exhaustion • Stress accumulates beyond the body’s ability to resist or adjust to it • The stage in which the body’s structure or systems begin to fail • Injury can occur during this stage.

8. Physical Improvement • Requires the controlled or regular application of stress • The body becomes increasingly resistant to the applied stress. (Strength, endurance, etc. increases.) • Stress may be increased on a regular basis to account for the body’s increased resistance to stress. • Adequate recovery must be allowed between bouts of stress in order to allow adaptation without debilitating injury.

9. Whole Body Adaptation • Considers the adaptation of the entire body as a unified system • Examples: • Aerobic endurance • Muscular endurance • Acclimatization (The adaptation of the body to adverse climate conditions such as heat, cold, high altitude, etc.)

10. Tissue Adaptation • Different tissues in the body respond and adapt differently to stress. • There are a number of factors that must be considered in order to avoid excessive and damaging stress to these tissues.

11. Factors Affecting Tissue Adaptation • Type of stress • Intensity of the stress • Frequency (including the period allowed for recovery between applications of stress) • Individual limits (general health, age, flexibility, etc.) • Other factors • Diet • Levels of hormones related to adaptation • Physical and emotional state

12. Specific Tissues • Muscle • Bone • Ligaments and Tendons • Cartilage Each of these tissues is important to the structure and function of the body. Each also responds and adapts differently to stress.

13. Muscle Tissue Muscle tissue produces the force that creates movement. Muscle tissue adapts readily to stress. Properly applied stress will increase muscle size and the ability of muscle tissue to produce force. Muscle tissue grows and adapts by two means: Hypertrophy – An increase in the size of muscle cells Hyperplasia – An increase in the number of muscle cells Muscle tissue is fairly elastic and can be measurable stretched or elongated without being permanently damaged.

14. Muscle Tissue Exercise Recovery There should be about 48 hours between bouts of intense exercise acting on any specific muscle. This allows the recovery from exercise induced damage. Inadequate recovery leads to an accumulation of unhealed damage, resulting in injury.

15. FUNCTION OF BONES • Support the body shape and structure • Protect internal organs • Provide mechanical frame for movement Rigid levers muscle force produces torque through the skeletal system

16. Exercise and Bone Health • Wolff's Law - Bone remodels according to functional demands • Exercise increases mechanical stress and strain and promotes the growth and development of bone tissue. • Most is most responsive to weight bearing stress (walking, running, lifting weights, etc.) • Inadequate stress, poor diet, low levels of specific hormones and other such factors may contribute to bone weakness.

17. BONE INJURIES • Traumatic – Single event injuries caused by a large stress. • Fatigue – Injury that results from repeated small stresses.

18. Fracture Healing • Unlike other tissues, bone heals by regeneration or replacement with the same type of tissue • No scar formation • Original physical integrity and biomechanical properties may be regained

19. Tendons and Ligaments • Tendons transmit force from muscle to bone. • Most ligaments bind bones together or help maintain the position or structure of some of the body’s components. • All tendons and most ligaments are inelastic structures composed of bundles of collagen fibers surrounded by tissue that contains blood vessels and nerves. • There are a few ligaments that are composed of elastic tissue that function in a slightly different fashion than most of the other ligaments.

20. Tendons Tendons transmit force from muscle tissue to bone. Hamstring Muscles (posterior thigh) Pectoralis Major

21. Ligaments Ligaments help bind bones together and stabilize structures within the body.

22. Tendons and Ligaments • Collagen turnover rate • Average of 300 to 500 days • Several months may be required to adapt, rebuild, or repair

23. Tendons and Ligaments • Blood supply • Poor in the tendon or ligament itself • Tendons and ligaments depend on diffusion to supply inner fibers with nutrients. • Vascular damage during injury can be particularly bad for healing • Injury Recognition – Because of the limited nerve supply, injuries in tendons and ligaments may not be recognized until they have become severe.

24. Collagen Bundles Tendons and ligaments consist of bundles of collagen surrounded by tissue containing nerves and blood vessels.

25. Collagen Bundles The tissue surrounding the collagen bundles contains nerves and blood vessels. Collagen Bundles The collagen bundles in tendons and ligaments are fairly small in order to facilitate diffusion.

26. Diffusion in Tendons and Ligaments Waste diffuses out of collagen bundles It may take several months to rebuild or repair the inner fiber structure of the collagen bundles. New material diffuses into collagen bundles

27. Joint Capsule Also called the articular capsule Forms an envelope surrounding synovial joints Made of two layers Outside layer of dense fibrous tissue Inside layer of loose fibrous tissue Lined with a synovial membrane Secretes synovial fluid that lubricates the joint

28. Synovial Joint joint capsule joint capsule articular cartilage

29. Joint Capsule (continued) • Help to hold bones together across synovial joints • Fairly tough and inelastic • Loose enough so as not to restrict normal joint movement • Functions very much like ligaments

30. Shoulder Joint Capsule – Anterior View

31. Cartilage A non-vascular structural material found in various parts of the body. There are many different kinds of cartilage serving a variety of functions. Forms most of the skeleton in infants. Replaced by bone through ossification during the maturing process.

32. medial meniscus lateral meniscus Menisci – Top View

33. Vertebrae – Cross Section intervertebral discs

34. articular cartilage (yellow) pelvis labrum (red) femur labrum (red) Hip – Cross Section articular cartilage (yellow)

35. Cartilage • Because of its non-vascular nature cartilage has a very limited capacity for adaptation and healing. • Cartilage is very susceptible to injury and tissue breakdown as the result of long-term regular stress.

36. Load and Injury Repetitive Loading – Usually a lower level load that occurs repeatedly over an extended period of time (as in running). • Produces microtrauma (small injuries that are usually inconsequential by themselves) • Microtrauma at any specific location can have a cumulative effect • The cause of fatigue injuries (such as stress fractures and many tendon ruptures)

37. Load and Injury Acute Loading – A large force which greatly exceeds the stress which the body is conditioned or designed to handle. • Produces macrotrauma (large injuries) • The cause of traumatic injuries as seen in falls, car accidents, etc.

38. Relationship Between Frequency and Magnitude of Loading It takes the right combination of load magnitude and load frequency to produce an injury. As load magnitude increases, less frequency is required to produce an injury. Load Magnitude Likelihood of Injury Frequency of Loading

39. Adaptability of Different Tissues • Muscle Tissue • Adapts well to stress • Properly applied stress can increase size and strength of muscle tissue • After extreme stress a recovery period is necessary to allow the muscles to adapt without severe injury • Bone Tissue • Adapts well to stress • Adaptation takes a long time • Bone can regain its full structural integrity after an injury

40. Adaptability of Different Tissues • Cartilage • Doesn’t adapt well to stress • Tends to break down with repetitive, high stress • Often will not heal after injury • Joint Capsule, Ligaments, and Tendons • Will adapt to stress • Because of poor blood supply and slow collagen turnover rate, adaptation takes a long time • Injuries take a long time to heal and healing may not be complete