It never ceases to amaze me how often I see volleyball coaches running their athletes through, "old school," conditioning while in season. They then go on to wonder why their athletes are hurting their knees, why verticals aren't improving and what can be done to remedy these issues. Often times the thought is to add something to the program as more is better and hard work makes improvement, right? Wrong. More is just more and hard work only leads to improvement when it is applied correctly. It seems extremely popular for coaches to implement P90X style conditioning in which their athletes do repeated vertical jumps or burpees to fatigue while throwing in sprints, pushups, crunches and whatever else. The common thought is, "it's hard, leaves the athletes gassed and contains sport-specific movements, so it must work!" This may seem sport-specific because it contains jumping, but it actually couldn't be further from what they need while in season. This is because the actual energy system demands in these types of situations are far from actual volleyball. Expecting them to respond positively with respects to their sport from jumps, agilities, suicides while fatigued or in a heavily aerobic state violates the SAID principle.
The SAIDPrinciple and Energy Systems
Specific Adaptation to Imposed Demand. That is one of the golden rules of training. It does not entirely mean that if you just keep jumping you will get better at jumping. What it does mean is that if you keep jumping with certain muscle fibers, at a certain pace, with certain recovery, you will become better at jumping a certain way. That "way" is all determined by the mechanics of the jump and the energy system(click to get a good background on the energy systems) the athlete is tapping into while they jump. Performing jumps while fatigued and in a heavily aerobic(breathing hard) state means that you are training yourself to jump better in those conditions. This often times results in having altered mechanics, relying heavily on ligamentous and structural stability(rather than muscular) to jump as well as recruiting more slow twitch fibers in the pattern than fast twitch. Jumping like this can greatly increase the risk of knee injuries as you can see below..
When our bodies enter into a largely aerobic state, they limit the amount of fast twitch fiber recruitment. This is because our fast twitch fibers are largely glycolitic which means that they're fueled anaerobically. You can read up more on the energy systems HERE. In short, the anaerobic systems are your body's first choice for fuel. It is rapidly prepared for use and requires no oxygen. When you run out of the creatine phosphate(10 seconds of activity), your body starts trying to convert the glycogen into ATP. This causes a byproduct of lactate and hydrogen. If you are expending energy at a rate faster than what your body can shuttle out these byproducts, you start to develop fatigue and that, "burning" sensation in those muscles. These byproducts are shuttled to the slow twitch fibers that can actually metabolize them with the use of oxygen into more energy. The increase in oxygen for metabolism results in heavier breathing.
So as you can see, the fast twitch fibers run out of energy pretty quickly. The slow twitch fibers can go all day. The more you train these fibers in specific movements, the more dominant they will be in recruitment strategies. So if you're jumping while in an aerobic dominant state, you're training yourself to use more slow twitch and less fast twitch when you jump.
The energy systems are not black and white. We are constantly using all of them at the same time, but there is generally one dominant one. It is normal to have an increase in breathing or feel some work in your legs during jumping. However, I would argue that doing what should be explosive style movements to glycolitic fatigue in a sport that has almost no aerobic element is extremely counter-productive to maintaining power-production and general orthopedic health.
What they need:
First, I'd like to point out that a quick google search reveals that there are no time-motion studies to be found on volleyball(or at least when I was looking). A time-motion analyses is a group of collected data taken during sporting events to tell you the average of: type of movement, intensity of movement, it's duration, frequency and amount of rest between bouts for that particular sport. This way strength and conditioning professionals can take a more objective look at what an athlete actually needs. The fact that there are none to be found on volleyball, in my mind, just goes to show that the aerobic conditioninglevel is insignificant when compared to other variables. It's for that reason that more emphasis should be focused on mechanics, maximal power output, and strength. Now with that being said, there is still a small aerobic component that could potentially limit an athletes' jumping ability at the end of a long game, but it needs to be addressed properly, without taking away from the aforementioned traits.
Researchers analyzed a German female beach volleyball team and found that in one hour of play, an athlete takes about 85 jumps on average. Another study followed a mens' beach volleyball team and found that they take an average of 145 maximal jumps during the course of play in a game. That same study noted that about 27% of the jumps were due to blocking. Though beach volleyball and indoor volleyball are two different beasts, what we can conclude from this is that since beach volleyball has 1/3 of the players and is much more active, that indoor volleyball requires even less total work output. This does however give us a, "line in the sand," to know how much work capacity they need. If you focus on giving them more capacity than what they need, then you run the risk of pulling from other training variables such as explosiveness.
Knowing the numbers above I would estimate that prepping an athlete to take 80-110 jumps(being liberal) in a game should suffice for most levels and positions. So they ideally need to be able to perform that many jumps over the period of a 60-90 minutes, without losing much "umph". Throw in the constant shuffling and repositioning and you could argue that there is an aerobic demand, but due to the amount of time between plays and the, "clusters" of movement, I would argue that it is minimal when compared to the demand on the creatine-phosphate system. You rarely see an indoor volleyball player panting or having a build up of lactic acid during a game. The main role of the aerobic system for these athletes should be to help adequately replenish the glycolitic system.
To address this, you want to try to improve the aerobic capabilities of the fast twitch fibers without giving the slow twitch fibers much stimulus. Doing this must be carefully programmed so as to not interfere with maximal power output. My favorite method for this is ballistic style conditioning. The only prerequisites for this method is that the athlete has a decent strength base, so that we know the tissues won't negatively respond to the impact, and proper jumping mechanics. If the athlete is lagging in those two areas then they are much better off focusing on those aspects than worrying about their conditioning.
Enter Ballistic style conditioning
Not only does it sound hard-core, it's pretty easy to implement, is extremely effective and is probably the most specific conditioning method for volleyball players. It is a form of interval training that is set to the individuals ability every time it is performed.
To implement this method, you need a point in which the athlete(s) can measure jump height on each of their reps. What I recommend doing is adjusting the nethigher so that they can't get one hand over when jumping(if possible) or using some other object(like a basketball hoop) for them to consistently touch when they jump. The athletes will first see how high they can get by jumping uptouching a spot on the net/object and will be instructed to mark and remember that spot. You can use tags or stickers if you don't trust them to remember.
You then pick an interval depending on the need, position, time of year and conditioning level of the athlete(s). I recommend 5-15 seconds on and 20-35 seconds off. When you start the interval the athlete(s) will jump and touch their individual spots repeatedly until the rest period starts. During the rest period, the athlete still does slight movements such as sidesteps in place. Just enough to keep the blood flow going. Then returns back to jumping when the rest ends. This is repeated UNTIL THE ATHLETE MISSES THEIR MARK, which signifies fatigue of the fast twitch fibers. At that point, the athlete stops and gets a gull recovery of 3-6 minutes so that the glycolitic system can recover. This constitutes as one set. I'd recommend doing anywhere from 1 to 3 sets depending on the situation and frequency of implementation. The training effect will make it so that the fibers can recover faster in between bouts so that they can generate near maximal forces even towards the end of the game.
This method should be used and completed before the season starts so that the training effect can be utilized in practice. So long as they are continuously practicing and playing in game-like situations, the effects should last. It will actually allow you to get in more maximal power work too, which is what you should be doing while in-season. Performing circuit-style conditioning or anything that pushes the athlete into 60-90 seconds or more of intense activity will start to diminish this affect.
Give this a try with your team next year. Get them working early so that they can get a good wave of ballistics in before their season starts and then continue to work on their maximal power and skills from there. If your team isn't ready for ballistics conditioning then working on jumping mechanics and a solid strength base will still improve their endurance on the court as well as improving their vertical.