Wk9


Lecture Overview

  • Understand the physiology of plyometric and ballistic training methods.

  • Identify the phases and roles of the stretch-shortening cycle.

  • Identify the components of a safe and effective plyometric/ballistic training program.

Plyometric Mechanics and Physiology

  • Plyometrics are activities that enable the muscle to reach maximal force in the shortest possible time.

  • They entail the use of the stretch-shortening cycle, involving elastic and neural components.

  • Plyometrics are used to develop an athlete's ability to rapidly express high levels of force.

The Mechanical Model of Plyometrics

  • First, elastic energy in the musculotendinous components is increased through a rapid stretch and stored.

  • When immediately followed by a concentric action, the stored energy is released, increasing or amplifying force output.

  • Concentric action must occur immediately for stored energy to be taken advantage of.

Neurophysiological Model of Plyometric Exercise

  • Involves the potentiation of the concentric muscle action through the stretch reflex.

  • Primarily driven by muscle spindle activity.

  • The concentric action must be immediate for the reflexive action to be taken advantage of.

The Stretch-Shorten Cycle

  • Describes a situation where the shortening function of the musculotendinous unit is enhanced by a preceding rapid stretch.

  • Broken into three phases:

    • Eccentric phase

    • Amortization phase

    • Concentric phase

Plyometric Exercise

  • Ultimately, plyometric movements are a summation of mechanical and neurophysiological factors.

Adaptive Responses to Plyometric Training

Outcomes of Plyometrics

  • Typical outcomes include:

    • Increases in vertical jump height

    • Increases in horizontal jump distance

    • Improvements in sprint speed

Musculotendinous Adaptations

  • Common adaptations to plyometric training also occur at the musculotendinous level.

  • Exposure to plyometric training leads to increases in stiffness of the overall musculotendinous unit.

  • Exposure to plyometric training may lead to some increases in muscle cross-sectional area.

Neural Adaptations

  • Neural adaptations to plyometrics occur at two locations:

    • Local Adaptations

      • Decreases in Golgi tendon organ inhibition

      • Increases in muscle activation

    • Central Adaptations

      • Increases in pre-activation of muscle

Plyometric Program Design

General Guidelines

  • Design of plyometric training programs adheres to the same guidelines as the design of non-ballistic training programs.

  • Starts with the needs analysis:

    • What are the training goals of the athlete?

    • What is the current training status of the athlete?

    • What is the athlete’s training history?

    • What are the demands of the athlete’s sport?

Training Factors for Plyometrics

  • Mode

  • Intensity

  • Frequency

  • Duration

  • Recovery

  • Progression

  • Warm-up

Mode

  • Dictated by the body region(s) involved in the plyometric:

    • Upper-body plyometrics

    • Lower-body plyometrics

    • Torso/trunk plyometrics

Lower-Body Plyometrics

  • Most commonly used mode of plyometric.

  • Target the rapid expression of high levels of force.

  • Align with the principle of…:

    • Jumps in place

    • Standing jumps

    • Multiple hops and jumps

    • Bounds

    • Box drills

    • Depth jumps

Intensity

  • Intensity of the plyometric is dictated by the stress applied to the musculotendinous unit.

  • Therefore, intensity is dictated by how the plyometric is performed:

    • Number of contact points

    • Speed of movement

    • Height of the drill

    • The body mass of the athlete

Frequency

  • The number of plyometric sessions is typically dictated by the demands of the session and the recovery time required.

  • Typically, one to three sessions per week.

Recovery/Rest

  • Plyometric exercises are performed at maximal intensity.

  • Longer rest periods are required to mitigate the fatigue response and facilitate ATP-PCr turnover.

    • Between sets: 1:5 to 1:10 work:rest ratio.

    • Between repetitions: 5-10 seconds.

  • Emphasis should be placed on the quality of the work performed.

Volume

  • Plyometric volume is expressed in the number of “contacts” performed by the athlete.

  • General guidelines are similar to prescribing training volume for other modes of resistance training:

    • Beginner (no experience): 80-100 contacts

    • Intermediate (some experience): 100-120 contacts

    • Advanced (some experience): 120-140 contacts

Implementing the Program

  • Introduction of plyometric training should follow a similar process to traditional resistance training:

    • Evaluate the Athlete

    • Conduct a Needs Analysis

    • Align the Program with Training Phases, Status, and Goals

    • Teach Appropriate Technique

    • Apply Sensible Progressive Overload

Safety Considerations

  • General motor literacy must be achieved prior to the introduction of plyometric exercises.

  • Athletes will require a level of maximum strength to tolerate the sustained loading of plyometrics.

  • The general training environment should also be considered.