Using plyometrics to improve power and Speed

Rate Of Force Development   The rate of force development(RFD) is a measure of explosive strength, or simply how fast an athlete can develop force.The definition of RFD is the speed in which the contractile elements of the muscle can develop force.Therefore, improving an athlete’s RFD may make them more explosive, as they can develop larger forces in a shorter period of time. Developing a more explosive athlete through strength and power developed in the gym and a combination of plyometrics, may improve their sporting performance.There is very strong evidence to suggest that combining strength and power training with plyometrics to improve RFD will improve jumping ability, sprinting and weightlifting.

PLYOMETRICS     

A plyometric exercise is defined as an exercise that incorporates a Stretch Shortening Cycle (SSC), which is a rapid stretch of a muscle or group of muscles, immediately followed by a concentric contraction. The three phases involved are the eccentric phase (muscle lengthens), the amortization phase (short time between eccentric and concentric phases), and the concentric phase (muscle shortens).The rapid stretch during the eccentric phase will result in increased force output if immediately followed by the concentric contraction.This is a result of our body’s ability to use stored elastic energy,the potentiation of the contractile machinery.  This process relies on the interaction between the series elastic component of our muscles and the contractile machinery, and the engagement of the muscles reflex action of the muscle spindle fibres.

Plyometric training has been shown to increase power output and RFD. Before prescribing any plyometric type exercises it should be noted that this type of training is very strenuous on the central nervous system and the body, so a high level of strength is required by the athlete. The measurement of the plyometric exercise is normally described by the number of contacts. This is when the athlete’s feet make contact with the ground. The number of contacts built into a plyometric training programme should be based on the athletes training age and height and weight.

 RFD and Plyometric training:

To improve RFD, it must be factored that force needs to be increased while simultaneously the time spent executing the action must be reduced. The following training modalities have been shown to correlate to improving athlete explosive strength Ballistic training, Olympic weightlifting, plyometric training, resistance training.

.PLYOMETRIC EXERCISES THAT IMPROVE RATE OF FORCE DEVELOPMENT

·      Box Jumps

·      Horizontal Jumps

·      Vertical Jumps (Bodyweight and loaded)

·      Lateral Box Shuffles

·      Depth Jumps

·      Repeat Hurdle Jumps

·      Band Jump Outs

·      Knees to Feet Jumps

·      Seated to Box Jumps

How does RFD affect speed?

The key determinants to speed are expressing large amounts of force in very short ground contact times as well as technical efficiency. If an athlete can improve one or both of those variables then their sprinting speed performance may improve. It has been shown that improving a person’s RFD will have a positive relationship to that person’s speed. Improvements in RFD may result in an increase in tendon stiffness, increases in force production and muscle fibre type recruitment which will all impact speed performance

Ground Contact When we discuss developing speed from a technical viewpoint, research tells us that the optimum ground contact time in the acceleration phase should be 0.12 - 0.18 sec.

Ground contact time can be improved by the following.

1)   The ability to apply force to the ground very quickly so bilateral and unilateral leg strength work is important.

2)   The stiffness of the leg at footstrike (a stiffer leg and tendon can create more free energy) so plyometric jumping drills will improve this.

First Step Distance The distance of the first step when sprinting normally averages 1.5m.

Triple Extension To achieve that we need an aggressive triple extension and flexion of the ankle, knee and hip.

Both first step distance and triple extension can be improved by increasing mobility in hips and training explosive movements which include RFD and plyometric type exercises.

Push/Pull This lower limb movement is ideally accompanied by an explosive push pull of the arms. Ideally during this upper limb movement, the elbow leads with hands driving up to eye level.                                     

Max Velocity When we further investigate the characteristics required for max velocity speed, the research tells us the ground contact time is reduced to 0.08sec, the stride length is increased 2.25-2.7m.  In doing this the max velocity speeds can reach levels as high as 12.8m/s.

Despite all the research and technique based training, the one training modality that will give the athletes/teams the biggest bang for their buck when it comes to developing speed is force production. Rate of Force Development is the ability of a muscle or group of muscles to develop maximal force very quickly.

Dr Peter Weyand cites many studies on human locomotion, and he quite simply states “The key to running faster is to apply more large specific mass to the ground quickly.”  In other words you have to apply the strength and power developed in the gym onto the training pitch and competition arena.

Muscular power is an essential component of all athletic activities. Power training has become increasingly popular because of the benefits it gives the athletes when it comes to power production in the gym and on the field. To manipulate RFD we can use the following methods;

·      high-load strength training

·      low-load speed and plyometric training  

(lifting lighter loads explosively)

·      plyometric training

Exercise selection used to develop rate of force production will be very dependent on the culture and environment of the team/club.

Olympic lifting in football programmes is somewhat frowned upon, due to anxiety of coaches and players that they may get injured or that it will make them slower. However, this trend is slowly changing as more and more high profile players are now incorporating Olympic lifting into their in-season conditioning programs with the intention of increasing Rate of Force Development and improving speed on the pitch.

One way to develop strong, fast athletes is to expose them to push/pull type exercises. To begin with I have my athletes pull with resistance, so a weighted pull up (20+kg) or a deadlift attached to heavy chains and a dynamic push exercise (full acceleration) .

Some examples of dynamic push exercises would be a barbell jammer or a barbell bench throw, to recruit some type 2 fast twitch muscle fibers. (see text box 1)

Another fantastic lower body full acceleration exercise that gives all the benefits of an Olympic lift but requires less technique is the loaded barbell jump. During this exercise huge triple extension is required along with high acceleration rate, through range of movement. Through the generation of high lifting velocities, the athlete can gain improved athletic power velocities. (7)

 Summary  Incorporating  Rate of Force Development into a in-season strength cycle would consist of lifting a light loads explosively.

1-2 sessions a week FOR A 4 WEEK are required to get an adaptation from this type of training.

Day 1    

EXERCISE                                     LOAD        SETS      REPS

BARBELL JUMP SQUAT                          40%               3                     3

BARBELL JAMMER                                  35%               3                     4

SQUATS WITH CHAINS                          60%               3                     5

WEIGHTED PULL UPS                   B/W +20 K           4                    6

Submaximal Loads 

 Day 2    

 EXERCISE                                     LOAD        SETS      REPS

BOX JUMPS                                                 B/W               3                     3

BENCH THROWS                                      45%               3                     5

DEADLIFTS WITH BANDS                    70%               3                     6

SINGLE LEG STEP UPS                           40%               4                    6