Use plyometrics to improve muscular power and military fitness

Plyometric training, sometimes called plyos (“ply-ohs”) or jump training, is a form of exercise that generates maximum muscle force in a short amount of time. Plyos take advantage of the elastic, spring-like properties of muscles, and use them to generate more power with each consecutive repetition.

What are plyometrics?

In order to be considered plyometric training, the exercise needs to follow specific mechanical steps called the stretch-shortening cycle. The first step is the eccentric phase, where a muscle is stretched—like when you stretch a spring to make it longer. Using a squat jump as an example, the eccentric phase is when you squat down before you jump up. Your quads and glutes are eccentrically stretched as you squat down. This phase stores elastic energy in the muscle and sends information from the nerves in your muscles to your spinal cord to trigger the stretch reflex. The stretch reflex is an involuntary action that causes your muscle to contract when it’s being stretched. Basically, it’s your muscles telling your spinal cord, “FYSA, we’re being stretched.”

Next is the amortization phase, or simply the brief pause in between the first and last phases. For the squat jump, it’s the very short period of time at the bottom of the squat before you jump up. During this phase, your spinal cord is transferring the information received about the muscle stretch to your motor nerves that start the muscle-contraction part of the reflex. This is your spinal cord telling your muscles: “I understand you’re being stretched. Now you have to contract.”

Finally comes the concentric phase, where you quickly shorten your muscles. It’s when you release the spring, and it shoots back to its shortened position (or the jumping portion of the squat jump). When you land from the jump, you continue right back into the eccentric phase without pausing, so you perform several squat jumps in a row.

Speed is essential in plyometric exercise. The faster you perform the eccentric phase, the more muscle cells you recruit for the concentric phase. When you contract a muscle, you don’t use every single muscle fiber in that muscle. The more fibers you’re able to recruit for a contraction, the stronger the contraction will be. If the amortization phase takes too long, the spring-like energy built up in your muscles and tendons will be lost as heat, and the stretch reflex is interrupted. Instead of using your muscles’ spring-like properties and involuntary reflexes to slingshot you into the concentric phase, you’re voluntarily using your muscles to generate all of the force you need to do your squat jump (from the example above).

Plyometrics aren’t exclusively jump training, which is why the strength and conditioning industry doesn’t use that term. Since plyometric exercise is more of a way to describe how you take advantage of the stretch-shortening cycle for training, it can be used for just about any muscle in your body, even upper-body muscles.

Proper work:rest ratios are very important for plyometric training. NSCA recommends a work:rest ratio of 1:5 to 1:10, meaning for every 1 second of work, you rest for 5–10 seconds.

Plyometric training

Plyometric training is very useful for increasing muscular power and would be particularly helpful to Soldiers training for the ACFT. Plyometric exercises are most common for the lower body, and they can be used for the upper body and even your trunk. Similar to how you plan resistance training or cardio training, plyometric training programming should follow the Frequency, Intensity, Time, and Type (FITT) principle.

Frequency is the number of sessions that you train in a week. When incorporating plyometric training into your workout program, it’s important to dedicate 1–3 days to these exercises, depending on your experience with plyos and what other components of fitness you’re training (for example, muscular strength, endurance, or power). Rest and recovery are very important for plyometric training, so it’s crucial to aim to have 2–3 days in between plyo days where you’re doing other types of workouts or active recovery.

Intensity is defined differently for plyometric training than it is for regular resistance training. Instead of measuring using a percentage of your 1-rep max, intensity is more vague and defined as the amount of stress placed on your muscles and joints. You can modify plyometric intensity by changing the type of exercises you do, the speed you do the exercises at, how high you jump, or by using weighted vests. Examples of low-intensity exercises include skips and bounds, and high-intensity exercises include box jumps, single-leg jumps, and weighted hops.

Time of your sessions better describes the number of reps and sets you do in a workout. National Strength and Conditioning Association (NSCA) recommends that beginners do 80–100 repetitions per workout, those with some experience do 100–120 reps, and very experienced athletes do 120–140 reps per workout. Proper work:rest ratios are very important for plyometric training. NSCA recommends a work:rest ratio of 1:5 to 1:10, meaning for every 1 second of work, you rest for 5–10 seconds.

Type of exercise can be upper- or lower-body plyometrics. Examples of upper-body plyos include medicine-ball chest passes with a partner, overhead throws with a partner, and plyometric push-ups. Lower-body plyos include different types of hops, bounds, and jumps.

Programming plyometrics with resistance and cardio training

If your physical training program includes doing plyometrics in the same week as resistance training, NSCA has a few recommendations. First, alternate the section of your body and intensity of your workouts. For example, if one day you’re doing a high-intensity, lower-body resistance workout, the plyo component of the day should be low-intensity upper body. Then on days you do high-intensity upper body, the plyo component should be low-intensity lower body. Avoid doing both high-intensity resistance training and plyometric training in the same workout, and avoid training the same part of your body (upper or lower) with both resistance and plyos in the same workout. High-intensity resistance and plyometric training in the same workout is known as complex training, which should only be performed by more advanced athletes and programmed by a strength and conditioning professional to include plenty of recovery between workouts.

Plyometric training and cardio training are a little less strict. Cardio exercise can have a negative effect on power output if it’s done first in a workout. If you’re going to do both cardio and plyos in the same day, NSCA recommends doing the plyos first for maximal power output.


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References

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Potach, D. H., & Chu, D. A. (2015). Program design and technique for plyometric training. In G. Haff & N. T. Triplett (Eds.), Essentials of Strength Training and Conditioning (4th ed.). Colorado Springs, CO: National Strength and Conditioning Association.