� Plyometrics
� Definition
� Activities that enable a muscle to reach maximal force in the shortest possible time.
� Incorporates a pre-stretch or countermovement to elicit a quick, powerful response
� Models of Plyometrics
� Mechanical Model
� Based upon the elastic property of musculoskeletal tissue
� When muscle put on stretch, it contributes stored elastic energy to subsequent muscle contraction
� The series elastic component (SEC) is primary factor made up mostly of the tendon
� If concentric contraction does not occur immediately after muscle stretch, the stored elastic energy will dissipate as heat
� Models of Plyometrics
� Neurophysiological Model
� Based upon the characteristics of the muscle�s contractile components
� When muscle put on stretch, it initiates the stretch reflex
� Stretch reflex responds to muscle spindle activity
� Muscle spindle is proprioceptive organ that senses muscle stretch resulting in greater neural input to make the muscle contract concentrically
� Too long of a stretch will negate the neurophysiological effect
� Stretch-Shortening Cycle
� The combination of elastic energy and stretch reflex facilitate a maximal increase in muscle recruitment
� Occurs in 3 phases:
� Eccentric Phase
� Amortization or Transition Phase
� Concentric Phase
� Phase 1 � Eccentric Phase
� During this phase:
� SEC stores elastic energy
� Muscle spindles are stimulated
� As spindles are stretched, type 1a afferent nerve fiber sends signal to spinal cord for response
� Visualize the time of foot contact with ground until the bottom of the movement in the long jump
� Phase 2 � Amortization Phase
� During this phase:
� There is a pause from end of eccentric stretch of muscle & initiation of concentric muscle contraction
� Upon stretch of spindles, signal sent via type 1a afferent nerve fiber to spinal cord for response
� Visualize the time foot stoppage right before beginning leap of the long jump
� Phase 3 �� Concentric Phase
� During this phase:
� Energy stored in SEC is utilized to enhance force of muscle contraction or it is dissipated as heat
� Signal from spinal cord is transported via alpha motor neuron to the muscle resulting in a reflex concentric contraction
� Visualize the foot leaving the ground to propel the long jumper forward and upward toward the pit
� Example of Phase Importance
� Vertical Jump (3 different starting positions)
� If starting from a squatting position (hip and knee joints at 90o flexion), then jumping upward; virtually no eccentric phase so height attained is not optimal
� If starting from a partial squat, followed by a further flexion of hip and knee, and then moving immediately into the jump upward (countermovement), this allows for some eccentric energy and some stimulation of the stretch reflex; jumper goes higher than the squatted static position
� If starting with a run up to the pit, all phases will be incorporated resulting in highest jump upward
� Plyometric Program Design
� Based upon the components of:
� Mode
� Intensity
� Frequency
� Duration
� Recovery
� Progression
� Warm-up
� Mode
� Determined by body region performing the plyometric action
vLower-body plyometrics
vGood for all movement sports
vMost are jumping drills
vUpper-body plyometrics
vGood for throwing sports
vExamples include medicine-ball throws, catches, and several variations of the push-up
vTrunk Plyometrics
vDifficult to perform true plyometrics in the trunk musculature
vMovements must be shorter and quicker in this region to get any eccentric energy and the stretch-reflex
� Intensity
� Dependent on the drill utilized
� Examples:
� Skipping is relatively low intensity
� Minimal stress on muscles and joints
� Depth jumping is relatively high intensity
� Great stress on muscles and joints
� Note: as intensity increases, volume should decrease
� Frequency
� Number of plyometric sessions/week
� Typically ranges from one to three depending on sport and time of year
� Athletes often utilize 2-4 sessions per week
� During in-season
� one session per week is appropriate for football players
� 2-3 sessions per week is appropriate for track and field athletes
� During off-season:
� 2-3 sessions per week are appropriate for football players
� 3-4 sessions per week are appropriate for track and field athletes
� Recovery
� Primary determinant to effectiveness of plyometric program since maximal anaerobic efforts are involved
� 48 to 72 hours (avg) between plyometric sessions shoul be allowed
� During exercise sessions:
� Depth jumps
� 5-10 seconds between reps
� 2-3 minutes between sets
� Time between sets should be based upon 1:5 to 1:10 work-to-rest ratios and are specific to volume and types of drills used
� Drills for same body area should not be performed on successive days
� Volume
� Defined as number of repetitions and sets performed during a training session
� Lower-body plyometric volumes
� Based on # of foot contacts per workout
� Also could be based upon distance, as with bounding drills
� Beginner (no experience)- start with 80-100 feet
� Intermediate (some experience)- start with 100-120 feet
� Advanced (considerate experience)- start with 120-140 feet
� Upper-body plyometric volumes
� Based upon # of throws or catches per workout
� Program Length
� Typical programs are 6-10 weeks
� However, vertical jump height can improve in 4 weeks
� Plyometrics can be utilized for both resistance and aerobic training
� For quick, powerful movements, should incorporate plyometrics throughout the entire macrocycle
� Intensity and volume should vary with sport and time of season
� Progression
� Should follow the principle of progressive overload
� Typically, as intensity increases, volume should decrease
� That is,
� Start with low to moderate volumes of low intensity
� Progress to low to moderate volumes of moderate intensity
� Then to low to moderate volumes of high intensity
� Warm-up
� Should consist of low-intensity, dynamic movements
� Typical warm-up drills:
� Marching (prep for running, posture emphasis)
� Jogging (prep for impact and high-intensity drills)
� Toe jogging, straight leg jog, butt-kicks
� Skipping (prep for reciprocal coordination between upper and lower body movements; quick landings)
� Footwork (prep for change of directions)
� Lunging (prep for lunge and multi-directions)
� Plyometrics and Other Exercises
� Plyometrics and Resistance Training
� Guidelines:
� Combine lower-body resistance training with upper-body plyometrics and vice versa
� Performing heavy resistance and plyometrics on same day is not recommended
� Complex training (heavy resistance followed by plyometrics) can be performed with adequate recovery in-between
� Traditional resistance training can be combined with plyometrics to enhance muscle power
� Example: (only for advanced plyometric person)
� Performing squat jump with 30% of one�s squat 1RM utilizing an external resistance
� Plyometrics and Other Exercises
� Plyometrics and Aerobic Exercise
� May consider combining these 2 training components for intermittent sports, i.e. soccer, basketball, etc.
� Aerobic exercise may have negative effect on power production
� Advisable to perform plyometric exercise before aerobic endurance training if incorporating both components
� Safety Considerations
� Generally, injuries from plyometrics, occur due to:
� Insufficient strength and conditioning base
� Inadequate warm-up
� Improper progression of lead-up drills
� Inappropriate volume or intensity for phase of training
� Poor shoes or surface
� Lack of skill
� Safety Considerations
� Pretraining Evaluation of Athlete
� Important for reducing potential for injury and facilitating performance
� Components of evaluation:
� Technique
� Strength
� Speed
� Balance
� Age
� Physical Characteristics
� Components of Evaluation
� Technique
� Learning proper landing technique for lower-body plyometrics is essential, i.e. depth jumps
� Center of gravity cannot be offset from base of support, otherwise injury can occur
� Shoulders should be over knees during landing while flexion of ankles, knees, and hips occurs
� Components of Evaluation
� Strength
� Must have a base of strength
� For lower body plyometrics, 1 RM squat should be at least 1.5 times his/her body weight
� For upper body plyometrics, 1 RM bench press should be:
������ - at least 1.0 times athlete�s body weight if weight is
�������� over 220 pounds
����� �� -� at least 1.5 times athlete�s body weight if weight is
����� ����� less than 220 pounds
����� �� - alternative measure:
����������� ���� ������ -ability to perform 5 clap push-ups in a row
Note: If athlete doesn�t possess minimum
�� strength, plyometrics should be delayed
� Components of Evaluation
� Speed
� For lower body plyometrics, athlete should be able to perform 5 repetitions of the squat with 60% body wt in 5 sec or less
� At same time, it is recommended that athlete participate in sprint training and speed-specific resistance training
� For upper body plyometrics, athlete should be able to perform 5 repetitions of the bench press with 60% body wt in 5 sec or less
� Components of Evaluation
� Balance
� Having the ability to maintain a position without moving for a given period of time is an important �basic� for plyometrics
� 3 balance tests for evaluation
� Beginners
� Standing � double-, then single-leg hold for 30 seconds
� Some experience
� Quarter-squat � double-, then single-leg hold for 30 seconds
� Advanced
� Half-squat � double-, then single-leg hold for 30 seconds
� Components of Evaluation
� Age
� High-intensity (e.g. depth jumps) plyometric drills are not recommended for prepubescent-aged children due to potential damage to growth plates
� Psychological maturity is also required prior to initiating high-intensity plyometrics. It is important to be able to follow coach�s or trainer�s instructions.
� Components of Evaluation
� Physical Characteristics
� High-volume, high-intensity plyometrics not recommended for individuals who are more than 220 lbs; increased risk for injury due to weight.
� These individuals should not perform depth jumps from heights greater than 18 in (46 cm)
� Individuals with previous injuries to spine and other body areas that take significant stress from plyometrics should refrain from these exercises
� Equipment and Facility Considerations
� Landing surface
� Should have adequate shock-absorbing properties
� Good surfaces � grass field, suspended floor, rubber mats
� Poor surfaces � concrete, tile, hardwood floor
� Excessively thick (6 in or more) exercise mats not good since these could extend the amortization phase and not let stretch-reflex occur effectively
� Mini-trampolines also not effective for plyometrics due to extended amortization phase
� Equipment and Facility Considerations
� Training area
� Bounding and running drills should be a minimum of 33 yds and up to 109 yds for straightaway
� Standing, box, and depth jumps only need a minimal area but height of 9.8 to 13.1 ft (3-4 meters) is required
� Equipment and Facility Considerations
� Equipment
� Boxes should be sturdy with non-slip top
� Box heights should range from 6 to 42 inches with landing surfaces of at least 18 by 24 inches
� Box should be constructed of sturdy wood (3/4 in plywood or heavy-gauge metal)
� Landing surface must be non-slip
� May use nonslip treads, mixing sand into paint, rubberized flooring
� Equipment and Facility Considerations
� Proper footwear
� Footwear with good ankle and arch support, good lateral stability, and wide non-slip soles
� Supervision
� Need close monitoring to avoid injury
� Depth Jumping
� Maximum height of 48 inches can be used but not increased possibility of injury
� Recommended heights:
� 16-42 inches with 30-32 inches being the norm
� 20-30 inches for athletes weighing over 220 pounds
� Summary
� Plyometric exercise has been proven to increase muscular power
� Sufficient base of strength, speed, aerobic and flexibility training, and nutrition are important for plyometrics to be effective
� Progression is important to incorporate in order to avoid injury and maximize performance