Specialised training: Plyometrics

Question 1

What is Plyometrics used for?

Answer 1

• To improve power (elastic strength)
  Power= strength x speed
• Designed to produce fast, powerful movements.

Question 2

Who does it benefit?

Answer 2

• Benefits athletes that have to lift their bodies (high jumpers + basketball players).
• Also needed by athletes that require explosive strength (ability to move parts quickly) e.g. sprinters + long jumpers.

Question 3

Plyometric training characteristics

Answer 3

• High intensity + short duration.
• Anaerobic.
• Energy systems used:
  1. ATP-PC system (0-10 secs).
  2. AGS (lasts 60 secs- 3 mins depending on intensity).

Sessions will involve GRAVITY (downward force created by lift).
- Jumping
- Hopping
- Skipping
- Clap press ups

Question 4

Types of isotonic muscle contractions + definitions

Answer 4

Concentric: Muscles shortening under contraction.
Eccentric: Muscles lengthening under contraction.

Question 5

Define a plyometric contraction

Answer 5

An initial rapid eccentric contraction followed by an explosive concentric contraction ( basically a muscle stretched prior to contraction).

Question 6

What are muscle spindles?

Answer 6

Receptors in the muscle that supply information about the rate of change and length of change of muscle.

Question 7

What is the stretch reflex?

Answer 7

A muscle that stretches eccentrically before a concentric contraction will contract more forcefully and more rapidly due to the stretch reflex (protective mechanism).

Question 8

Stretch reflex (more detail)

Answer 8

• Protective mechanism that stops a muscle overstretching and tearing.
• A muscle that is stretched before it contracts will do so with greater force due to the stored energy in the muscle.
• Muscle spindles detect any tendency to overstretch.

Question 9

What happens if there is an overstretched muscle?

Answer 9

• A nerve impulse is sent to the spinal chord which immediately contracts the muscle and stops it being overstretched.

Question 10

The process

Answer 10

1. Muscle contracts eccentrically whilst landing (stretched).
2. Muscle spindles detect rate of change and length of change.
3. Signal is sent from the muscle spindles to the CNS.
4. CNS initiates the stretch reflex to prevent over stretching.
5. This causes a powerful concentric muscular contraction.

Question 11

Stretch shortening cycle (Phase 1)

Answer 11

Phase 1:
Rapid eccentric muscle contraction when elastic energy is stored.

Question 12

Stretch shortening cycle (Phase 2)

Answer 12

Phase 2: Amortisation
- This is a short time between the end of the pre stretch and the start of the concentric contraction.
- The shorter this phase, the more powerful the muscle contraction will be.

!!! A delay in contraction will cause all potential energy to diminish !!!

Question 13

Stretch shortening cycle (Phase 3)

Answer 13

Phase 3:
Powerful concentric contraction.

Question 14

Advantages

Answer 14

1. Excellent method of developing power and elastic strength.
2. Can develop power in upper and lower body.
3. Activities can be made sport specific.

Question 15

Disadvantages

Answer 15

1. High intensity work can lead to injury through the tearing of muscle fibres.
2. Appropriate technique is crucial along with a suitable warm up.
3. More recovery time is needed.
4. Can lead to DOMS (delayed onset of muscle soreness).