Understanding the Basics of Stretching

1. Understanding the Basics of Stretching Chapter 1

2. Types of Muscle Contractions: Isotonic and Isometric • Isotonic is a voluntary muscle contraction that causes movement. • Two types are concentric (muscle shortens as it works) and eccentric (muscle resists while being lengthened by an outside force). • Concentric isotonic contraction of biceps brachii happens while bending the elbow, as in an arm curl with dumbbells (see figure 1.1 on the next slide). Eccentric contraction of the biceps occurs as you lower the dumbbells. Outside force resisted is a combination of gravity and weight of dumbbells. Eccentric contraction is also negative work. • An isometric contraction is a voluntary contraction in which no movement occurs. When you hold a dumbbell in midcurl, you’re doing an isometric contraction.

3. Concentric, Eccentric, and Isometric Contractions of the Biceps Adapted, by permission, from J.H. Wilmore and D.L. Costill, 2004, Physiology of sport and exercise, 3rd ed. (Champaign, IL: Human Kinetics), 53.

4. Reflexes Relevant to Stretching • According to most textbooks, a reflex is an automatic, involuntary response to a stimulus. • Scientific and research communities have reached a consensus that reflexes are more complex and not as automatic as previously believed. The effect of a reflex is task dependent. • New knowledge of reflexes affects our explanations of why various forms of stretching work, including facilitated stretching.

5. Myotatic Stretch Reflex • It prevents a muscle from stretching too far too fast, which helps protect the joint from injury. • Reflex is what you see when a physician tests your reflexes. She strikes the biceps tendon with a rubber hammer; the arm automatically bends at the elbow. • Proprioceptors (muscle spindles) monitor length and tension of muscle. • Whether the reflex is initiated depends on the speed and the distance the muscle is stretched, whether the stretch is occurring because the opposing muscle is contracting, or if the opposing muscle is inactive, as in the hammer reflex.

6. A Representation of the Muscle Spindles, Which Mediate the Myotatic Stretch Reflex

7. Inverse Stretch Reflex • Also called autogenic inhibition, it’s mediated by stretch receptors called Golgi tendon organs (GTOs) located in the musculotendinous junction and the tendon. • Traditional PNF theory includes discussion of inverse stretch reflex and supposed effects after isometric contraction. The belief has been that GTOs monitor the load on the tendon. If the load becomes too great, GTOs are stimulated. In turn, they were thought to cause the muscle to relax through neurological inhibition. • GTOs do monitor muscle tension but do not mediate inverse stretch reflex, if such a reflex exists. • Scientists are still trying to understand GTOs and believe that their effect is task dependent and may inhibit or excite the muscle in which they’re located, as well as neighboring muscles.

8. Reciprocal Innervation • Sherrington’s research in the 1900s helped develop a model for how the neuromuscular system operates. • His law of reciprocal innervation (also called reciprocal inhibition) has described a reflex loop mediated by the muscle spindles. • When a muscle contracts, reciprocal inhibition was thought to inhibit the opposing muscle. The inhibition would allow movement to occur around a joint. • When the quadriceps muscle contracts, the hamstrings would be reciprocally inhibited, allowing the knee to straighten. If the reflex loop is not functioning well, the muscles could be fighting each other, and the movement might become difficult or compromised (figure 1.3, p. 5). (continued)

9. Reciprocal Innervation (continued) • Although reciprocal inhibition can be seen under experimental conditions, in real life it’s more complex. It’s more likely to occur when necessary, as during joint movement, not when undesirable, as in joint stabilization, when we need to have opposing muscles cocontracting. • Reflexes are now seen as task dependent, not as automatic, involuntary reactions that always occur the same way.

10. Reciprocal Inhibition: When the Quadriceps Contract, the Hamstrings May Be Inhibited

11. Types of Stretching • Passive • Active • Assisted • Ballistic • Dynamic • Static

12. Passive Stretching • It’s done to the stretcher by a partner. • With ballistic or static, stretcher relaxes and partner moves the stretched limb to gain new range of motion. • Passive stretching is used to increase flexibility at the extremes of ROM.

13. Active Stretching • Stretcher does the work instead of a partner. • Generally considered safer than passive stretching. • Stretcher controls the force and duration of stretch.

14. Active-Assisted Stretching • Active movement by the stretcher • Help from a partner • To add passive stretch • To provide resistance to motion

15. Muscle Energy Technique • MET targets the soft tissues primarily, although it contributes to joint mobilization. • MET uses an isometric contraction of the target muscle before the stretch. • Stretch is most often done passively. • Minimal force during isometric phase. • Lewit technique (PIR) • Reciprocal inhibition stretching (RI)

16. Active Isolated Stretching • AIS was developed by Aaron Mattes. • Uses active movement and reciprocal inhibition stretching. • Isolate the muscle to be stretched, then actively lengthen it to a point of light irritation. • Hold for no more than 2 seconds. • Return to starting position. • Sequence is repeated 8 to 10 times.

17. PNF Stretching • Most PNF stretching techniques are done passively or as active-assisted exercises. • Two types of PNF stretching: • Hold–relax • Contract–relax

18. Ballistic Stretching • Performed using rapid bouncing movements that force the target muscle to elongate. • Generally out of favor. • Increases the likelihood of tearing the muscle.

19. Ballistic Stretching Is Performed Using Rapid, Bouncing Movements

20. Dynamic Stretching • Dynamic flexibility is the ability to actively bring a limb through its full ROM. • Usually performed as a warm-up before exercise. • As the dynamic motion is repeated, speed of the movement increases, as does the available ROM. • Differs significantly from ballistic stretching.

21. Static Stretching • Muscle to be stretched is lengthened slowly and held in a comfortable range for 15 to 30 seconds. • Stretcher moves gently into a deeper stretch and holds again.

22. Hamstring Static Stretch: (a) the Stretch Begins and (b) Deepens After 15 to 30 Seconds a b

23. Guidelines • Tangible benefits • Proponents • Prevents injuries • Prevents soreness • Improves performance • Increases body awareness • Stimulates blood flow • Relaxes and centers mind • Opponents • Waste of time • Can cause injury

24. Guidelines • Stretch after warm-up. • Stretch twice. • Stretch once. • Stretch without pain. • Remember that flexibility varies. • Recognize when to stretch and when to strengthen.