plyometrics training in athletes and the science behind it

Plyometrics

1. Plyometrics Plyometric means to increase measurement ( plio = more; metric = measure) Greek words Plyometric is a quick, powerful movement using a pre-stretch, or countermovement, that involves the stretch–shortening cycle (SSC).

2. Purpose of plyometrics The purpose of plyometric exercise is to increase the power of subsequent movements by using both the natural elastic components of muscle and tendon and the stretch reflex.

3. Physiology Plyometric training improves the production of muscle force and power. This increased production of power is best explained by two proposed models: Mechanical Model Neurophysiological Model

4. Mechanical Model Elastic energy in the musculotendinous components is increased with a rapid stretch and then stored When this movement is immediately followed by a concentric muscle action, the stored elastic energy is released, increasing the total force production

5. Neurophysiological Model Potentiation of the concentric muscle action by use of the stretch reflex Potentiation is change in the force–velocity characteristics of the muscle’s contractile components caused by stretch Stretch reflex Muscle spindles (proprioceptive organs response to stretch)

6. Proprioception  means "sense of self". The  muscle spindle   provides information about  changes in muscle length .  The  Golgi tendon organ  provides information about  changes in muscle tension .

7. Muscle spindle

8. Muscle Spindle (MS) Structure of MS Types of fibres Nerve supply of MS Function of MS

9. Muscle spindles are encapsulated spindle shaped sensory receptors located in the muscle belly of skeletal muscles MS is formed by modified skeletal muscle fibers called intrafusal fibers which lie between regular skeletal muscle fibers, referred to as extrafusal fibers

10. Structure of muscle spindle: Muscle spindle has a central bulged portion and two tapering ends Each muscle spindle is formed by 5-20 intrafusal muscle fibers Intrafusal fibers are enclosed by a capsule, which is formed by connective tissue Intrafusal fibers are attached to the capsule on either end

11. Capsule is attached to either side of extrafusal fibers or the tendon of the muscle Thus, the intrafusal fibers are placed parallel to the extrafusal fibers

12. Signals – length and rate of change of length (velocity) of the muscle Muscles that are necessary for fine movements contain more spindles than muscles that are used for posture and coarse movements

13. Nerve supply to muscle spindle Motor nerve supply: Efferent nerve fiber supplying the muscle spindle belongs to gamma motor neuron type Extrafusal fibers are controlled by alpha motor neurons

14. Sensory nerve supply: Group Ia sensory – wraps around the equatorial region (most elastic) of both bag and chain – responds quickly to stretching Group II sensory – wraps around the region next to equator, less elastic – less responsive to stretching

15. Functions of muscle spindle Muscle spindle has two functions: Role of muscle spindle in stretch reflex Role of muscle spindle in the maintenance of muscle tone

16. STRETCH REFLEX ( myotatic reflex) Stretching of muscle causes stretching of MS Discharges sensory impulses Impulse transmitted to alpha motor neurons in spinal cord Alpha motor neurons cause contraction of extrafusal fibers

17. Hence, MS gives response to change in length of the muscle. By detecting the change in length, MS plays an important role in preventing the over stretching of the muscle

18. MUSCLE TONE Continuous and passive partial contraction of the muscles , or the muscle’s resistance to passive stretch during resting state Protective and helps in maintaining balance

19. It is due to state of continuous discharge of impulses from gamma motor neurons When the frequency of discharge from gamma motor neurons increases, muscle tone also increases

20. The stretch–shortening cycle (SSC) employs the energy storage capabilities of the SEC and stimulation of the stretch reflex to facilitate a maximal increase in muscle recruitment over a minimal amount of time.

21. The 2 nd phase of SSC is perhaps the most crucial in allowing greater power production Its duration must be kept short If the amortization phase lasts too long, the energy stored during the eccentric phase dissipates as heat, and the stretch reflex will not increase muscle activity during the concentric phase

22. The rate of musculotendinous stretch is vital to plyometric exercise Static Squat jump Countermovement jump An approach jump (volleyball) Rate of stretch and jump height?

23. The stretch–shortening cycle combines mechanical and neurophysiological mechanisms and is the basis of plyometric exercise. A rapid eccentric muscle action stimulates the stretch reflex and storage of elastic energy, which increase the force produced during the subsequent concentric action.

24. PROPOSED MECHANISM BY WHICH PLYOMETRIC TRAINING ENHANCES PERFORMANCE Enhanced muscle spindle activity Desensitization of the GTO allows greater contraction ability by muscle before it is activated because of stress to switch off muscle for protection Enhanced intramuscular and intermuscular neuromuscular efficiency

25. Determinants of plyometric training in lower limb Jump height Sprint speed improved running economy improved joint position sense postural control

26. Program Design Needs Analysis Mode Intensity Frequency Recovery Volume Program length Progression Warm-up

27. Need’s analysis Plyometric program should be designed dependent upon the athletes sport and position. sport’s individual requirements the positions within the sport needs of each athlete

28. Mode Lower body plyometrics Upper body plyometrics Trunk plyometrics

29. Games specific plyometrics Lower limb Track and field Sprinting Soccer Volleyball Basketball (center player) American football Baseball endurance sports such as distance running and triathlons Upper limb Baseball Softball tennis, golf, throws in track and field (i.e. The shot put, discus, and javelin)

30. Intensity Type of drill: Skip vs depth jump Height of the drill Points of contact: Single vs double leg Speed Body weight and External weight

31. Frequency 1 to 4 days/week Based on recovery time: 48 - 72 hours Depends on the athlete’s experience with plyometric training, and the time of year Off-season = 2-3 sessions/week for American footballers, 3-4 sessions for track and field athletes. In season = 1 session/week for American footballers, Track and field athletes = 2 to 3 time/week

32. Recovery period Rest intervals between sets, repetitions, and plyometric exercises is important for adaptations ( 2 to 3 min) Recovery for Depth jumps: Between reps - 5-10 sec; Between sets – 2-3 min The time between sets is determined by a proper work-to-rest ratio (i.e., 1:5 to 1:10) Using a 1:10 ratio, an athlete would rest ∼100 seconds if the total set length was 10 seconds. Thus, 1:5 ratio may be applied to low- and moderate-intensity drills and 1:10 ratio to higher intensity drills 48–72 hours of recovery in between training sessions

33. Volume No of reps *sets Lower body = no of foot contacts/ also expressed as distance as with plyometric bounding. Upper body = no of throws and catches

34. Program length 6 to 10 weeks vertical jump height improves as quickly as four weeks after the start of a plyometric training program.

35. Progression Low to high intensity Two legged jumps to one legged jumps Raising box jump and heights Increase weight of medicine ball Increasing number of hurdles

36. Age considerations Plyometric Training is Harmful for Children and Adolescents?

37. Safety Considerations Pre-training Evaluation of the Athlete Technique Strength Balance Physical Characteristics

38. Equipment and Facilities Landing surface grass field, suspended floor, or rubber mat are recommended concrete, tile, and hardwood are not recommended because they lack effective shock-absorbing properties Excessively thick exercise mats (6 inches [15 cm] or thicker) may extend the amortization phase and thus not allow efficient use of the stretch reflex

39. 2. Training area : proper space to perform drills 3. Equipment: boxes should have nonslip top, sturdy wood made, 4. Proper footwear 5. Supervision 6. Depth jumping : The recommended height for depth jumps ranges from 16 to 42 inches (41 to 107 cm). Depth jump box height for athletes who weigh over 220 pounds (100 kg) should be 18 inches (46 cm) or less.

40. Plyometric with other forms Plyometric combined with resistance training Plyometric combined with aerobic training

41. Contraindication to plyometric exercise acute recovery period after surgery gross instability of ankle and knee joint pain a state of unconditioning Inflammation Acute or sub-acute sprains/strains

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