By Tim McClellan
Tim McClellan, MS, CSCS, is the Performance Enhancement Director at Makeplays.com. He has coached volleyball players for over 20 years, ranging from professionals to youth club competitors.
Coaching Management, 13.5, April 2005, http://www.momentummedia.comAsk any volleyball player what her primary objective is for her off-season training efforts, and the answer is always the same. Ask any club, high school, or college coach what his or her training goals are for their team, and you’ll hear an echo. They will all say, "Increase vertical jump."
The key to increasing vertical jumping ability is to incorporate plyometrics into a training program. Most coaches today understand the value of plyometrics, but few understand how to safely and effectively make it a part of their offseason training programs.
HISTORY & DEFINITIONS
It is often said that plyometrics were invented in the 1970s by Soviet Bloc and Eastern European coaches. This is actually not true. The term "plyometrics" may not have been popularized until that time, but there are much earlier accounts of Japanese judo athletes hopping up steps, track athletes performing hurdle hops, and boxers jumping rope. The effectiveness of such training has been known for at least 100 years.
But there are still many misconceptions about what plyometrics are and how they work. Simply stated, an exercise is deemed plyometric if the muscle groups utilized contract rapidly in a shortening fashion, after previously lengthening. The classic volleyball example is a middle blocker touching down after blocking a ball and immediately having to jump again to block another. The plyometric effect is present when the muscles of the thighs, glutes, calves, and core lengthen upon floor contact (eccentric contraction) and are then asked to immediately shorten (concentric contraction) in the propulsion of the next jump.
The goal of training with plyometrics is to increase the rate of this stretching and shortening, as well as the power behind it, so that the stored elastic energy more rapidly transfers to the next explosive movement. In the above example, it means the volleyball player will spend as little time as possible on the floor between jumps, while elevating as high as possible during both jumps. This rapid transfer of elastic energy into the shortening phase is believed by many to be the most productive training stimulus for improving explosive muscle contraction and increasing vertical jump capability.
Understanding plyometrics also requires knowing the difference between strength and power. Power is defined as the amount of force an athlete can apply over a distance in the amount of time it takes to do so. It differs from strength in that the strength equation does not take into account the time component.
For example, if Kaylin squats 200 pounds x 3 feet over the course of 6 seconds, her power ratio is 200x3/6 = 600/6 = 100 foot pounds/second. If her twin sister Ashley squats 150 pounds x 3 feet over the course of 3 seconds her power ratio is 150x3/3 = 150 foot pounds/second. Ashley isn’t as strong as Kaylin, but she demonstrates more power.
Since the leg extension movement required in jumping takes between 0.2 and 0.3 seconds, and maximal strength development takes usually between 0.5 and 0.7 seconds, it makes sense for athletes to incorporate exercises aimed at increasing power. Increasing strength is important for increasing power, but speed of movement is a critical second step. And speed of movement is a big component of plyometrics.
ARE THEY SAFE?
With this sound scientific reasoning for enhanced power development, and knowledge that most elite-level volleyball players, basketball players, and jumping field-events athletes use this type of training, it would seem that there should be instant incorporation of plyometrics into all volleyball training programs. However, plyometrics have been criticized for having a greater risk of injury than other methods due to increased forces of landing and immediate rebounding.
In reality, these fears won’t materialize if a progressive program is implemented. Consider these facts:
Volleyball is a plyometric sport, as are most other sports. Competitors are required to decelerate and accelerate in a different direction, be it a libero exploding laterally to dig a ball and then getting back to original position, or a middle blocker having to jump quickly to make consecutive blocks. Sending an athlete into a plyometric sport unprepared to make plyometric movements is like sending someone to a piano recital after having them practice extensively on the tuba.
Many of the reported injuries resulting from plyometrics occur in populations that are very different from competitive sport-specific athletes. For example, one article that calls plyometrics dangerous is talking about participants in aerobics classes. Comparing hard-training athletes to the bulk of participants in an aerobics class is simply inaccurate. Many aerobics participants aren’t used to plyometric activity or lack a sufficient strength base to safely perform plyometrics. Most volleyball players have extensive, though possibly informal, histories with plyometric exercise and many have access to adequate strength programs, giving those athletes a leg up when it comes to avoiding injury.
The National Strength and Conditioning Association has issued a position paper with regards to plyometric exercises touting its benefits over its risks. The paper says, "Carefully applied plyometric exercise programs are no more harmful than other forms of sports training and competition, and may be necessary for safe adaptation to the rigors of explosive sports."
So what constitutes a "carefully applied" and "safe" plyometrics program? The first step is to understand that plyometrics tax the athletes’ muscles, connective tissue, and nervous system, and thus should be implemented with care. Consider these important guidelines from the NSCA position statement:
• A thorough set of warm-up exercises should be performed before beginning a plyometric training session.
• Footwear and landing surfaces used in plyometric drills must have good shock absorbing qualities.
• Only athletes who have already achieved high levels of strength training through standard resistance training should engage in plyometric drills.
• Less demanding drills should be mastered prior to attempting more complex and intense drills.
In terms of the strength needed before starting a plyometrics program, there is no hard-and-fast rule. It has been mentioned in previous literature that a player should be able to squat twice his or her weight before beginning plyometric training, but this lacks substantiation and is not accepted by most diligent performance enhancement coaches. The National Football League, for example, is full of 350-pound linemen who cannot squat 700 pounds, yet they routinely train with plyometrics.
Rather than risk injury by making athletes "max-out" on squats, I feel it is more important to observe strength levels exhibited during play. If the athlete shows sufficient and functional strength movements while fulfilling sport requirements, he or she is ready for a plyometric program.
For example, one of our current clients is a 6’3", 16-year-old female who cannot squat twice her bodyweight. Few players her age, height, and weight would be ready for medium or advanced-level plyometrics, but this athlete actually started functional strength training when she turned 13, then started on very low levels of plyos as she developed her strength. Her years of strength work prepared her for the demands of higher-level plyometrics at a younger age. She now possesses the strength, physique, and movement skills of a college-age player, and actually has already made a verbal commitment to accept a volleyball scholarship at a prestigious university.
To implement a progressive plyometrics program, start with lower level exercises and progress slowly into medium and more advanced stages. Vern Gambetta, who has coached national and world-class athletes for three decades, says the key is to understand the stress of different types of drills and to only progress to higher stress exercises when the athlete is ready. He has developed a rating scale to help coaches understand the different stress levels (see "Rating Scale" below).
WHEN TO PROGRESS
How do you actually know when the athlete is ready to progress to the next level? Coaches, above all, must be great observers. If the player is struggling to complete the plyometric movement, then the exercise is inappropriate for that individual. If the athlete has mastered the exercise repeatedly, she is ready to move to the next level.
For example, double-leg hops down an agility ladder can be successfully used by groups of females as young as 13 on their first day of training. My past experience has shown they can handle this very low-level plyometric activity using appropriate mechanics at almost no risk of injury. Most at this age can then progress to performing the same exercise over six-inch hurdles, while some can do the same over 12-inch hurdles. However, if an athlete exhibits a lack of ability to maintain proper biomechanics, then the exercise opens the athlete up to a greater risk of injury. At that point the athlete should return to a lower level of exercise.
Some examples that might indicate that the athlete is not ready for the next level include the following:
• If the athlete shows extensive bending at the waist or her torso flops forward or from side-to side, more core work may be needed.
• If the athlete exhibits prolonged contact with the floor, she may not have the overall body strength and power necessary to proceed.
• If the athlete’s knees are collapsing towards each other, this can mean lack of quadriceps strength. This can occur on landing during the eccentric contraction or on push-off of the concentric phase. If the level of exercise is not decreased, these movements can lead to joint pain, tendonitis, excessive heaviness of the legs, and a decreased demonstrated ability to explode. Ideally, the knees should be aligned over the middle toe of each foot.
Along with the position of the knees, the position of the feet is also important during landing. It has been said that all athletes doing plyometrics should land first on their toes and balls of feet, then make contact with their heels to help absorb force. This is correct for high-level jumps and plyometrics such as depth jumps, box jumps, tuck jumps, and many repeat hops. However, this is not correct for very low-level plyometrics, such as ankle flips, rope jumping, and agility ladder drills. In these low-level exercises, the athlete’s entire floor contact should be made with the toes and balls of the feet. There should be no contact between the floor and the athlete’s heels. In addition, there should be as little noise as possible made by the athlete’s feet when landing.
The athlete should also try to keep her head up during all drills. This helps prepare her for on-court situations, when jumping and viewing the court need to be done simultaneously.
In designing your own program, it’s important to start with low-level plyometrics. Here are some examples:
• Rope jumping (various patterns)
• Speed-agility ladder
• Six-inch hurdle hops (forward hops, side hops, side-to-side hops over one hurdle, side hop with a vertical block)
• Ankle flips
• Power skips
• Side-to-side hops to create a distance (such as hitting dots on a dot drill pad).
Here are some mid-level plyometric exercises:
• Rope jumping (double jumps)
• 12-inch hurdle hops (repeat forward hops, forward hops with block, side-to-side hops with block, hop-scotch)
• Low-level depth jumps
• Dumbbell squat jumps
• Low-level single-leg box or hurdle hops
• Resisted/assisted lateral hops (can include vertical block).
High-level plyometric exercises include:
• Depth jumps
• Depth jumps onto or over another object
• Single-leg hurdle hops (both forward and lateral)
• Dumbbell split-squat jumps
• Lateral bounding
• Side step-up jumps over a bench
• Resisted/assisted hops or shuffles over hurdles.
As your athletes move into the higher levels of plyometrics, it’s especially important to be position-specific when developing a regimen. For front row players, repeat hops are a solid choice (assuming the player is ready for such training). Repeat hops can be performed as consecutive vertical movements, lateral movements, or preferably a combination of both.
For the "movement based" positions of setter, libero, or the defensive specialist in high school play, lateral movements are more appropriate. One exercise particularly helpful for this group is to attach a resisted/assisted bungee cord to the athlete via a belt. If it is attached to the left hip, the athlete would jump to the right against the resistance, usually over chalk lines or a taped area. Upon touching down they would then pop back to starting position with assistance from the stretched cord. Repeat for the desired number of repetitions (such as a set of 10 reps) then switch direction.
With any and all of the exercises, the keys to keep in mind are minimizing contact time with the ground and maintaining appropriate biomechanics. As the athletes progress, you’ll see improvement in the drills, then on the playing court.
This article is also appearing in Coaching Management’s sister publication, Training & Conditioning.
PLYOMETRIC DEMAND RATING SCALE
Rating . . . . . . . . . . . . . .Example . . . . . . . . . . .Recovery Time
1 = very low stress . . .Rope-jumping
. . . . . . . . . . . . . . . . . ankle bounces
. . . . . . . . . . . . . . . . similar low-amplitude jumps . . . . . Very rapid
2 = low stress . . . . . .Tuck jumps
. . . . . . . . . . . . . . . . similar in-place jumps
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rapid, one day required
3 = moderate stress . . .Stair jumps
. . . . . . . . . . . . . . . . . .similar short jumps
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . One to two days
4 = high stress . . . . . . Hops
. . . . . . .. . . . . . . . . . . bounds for distance
. . . . . . . . . . . . . . . . . .similar long jumps
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slow, two days required
5 = very high stress . . . Depth jumps
. . . . . . . . . . . . . . . . .similar shock-type jumps
. . . . . . . . . . . . . . . . . . . . . . . . . Very slow, three days required
. . . . . . . . . . . . . . . . . . . . . . . . highest nervous system demand