Jumping, skipping, hopping and leaping are part and parcel of sports. The muscles involved in these intense and high-impact movements need additional conditioning. Professional athletes do so by incorporating a series of jump exercises to mimic the action and loads involved.
These exercises, collectively known as plyometrics, have now made their way to neighbourhood gyms and parks as well, with people employing them to increase explosive strength and muscular endurance.
Plyometric exercises work the muscle differently — the action in the exercises makes the muscle lengthen and then rapidly shorten in a continuous rhythm (jumping and landing, for instance).
The plyometric exercise system originated in the erstwhile Soviet Union where sports scientist Yuri Verkhoshanky developed a technique called the depth jump that was used extensively to train track-and-field athletes. The rest of the world soon took note, and the depth jump was developed into a set of exercises that was given the name plyometrics by American track-and-field coach Fred Wilt in the 1970s.
Link between plyometrics and strength performance
The performance benefit of plyometric exercises can be analysed based on three parameters:
- RFD (rate of force development)
- RSI (reactive strength index) and
- Minimising the energy leak from the joints.
Strength and conditioning specialist Mrinal Roy says plyometrics directly connects strength to actual performance. “RFD is basically how much force an individual generates on the ground, which defines performance,” says Roy, also founder of Team SCCS, a Mumbai-based strength and conditioning consultancy service. “For example, to get up from the chair and start running, some [people] will be quick while some will be slow. As age increases, the RFD goes down.”
RSI, on the other hand, is the contact time with the ground. “If the contact time with the ground is more than 200 milliseconds, then no effect of plyometrics will be there — so it’s like how fast one gets off the ground after touching it,” says Roy. “And leakage of energy from the joints is reduced only through regular practice.”
Though beneficial, plyometrics needs to be done systematically and progressively, and under expert guidance. Its USP – the high impact – also has a flip side: though it conditions the muscles, it could inflict severe injuries if done incorrectly.
Since it involves high-intensity exertion, a plyometric routine should start at a low intensity and the step-up should follow fitness or performance gains.
Obesity and age factor
It is believed that every take-off in a plyometric exercise puts a load of approximately six times the body weight on landing. Refining the landing technique can ease the load, but only marginally.
These exercises may lead to bone injuries in overweight or obese people. So, it is advisable to lose excess weight before starting.
Plyometric exercises should be avoided by older people — say, those over 50 — and those not into any high-intensity performance sport or physical activity.
Number and duration
There should be a good amount of time gap between two sessions of plyometrics. An appropriate amount of contact (number of jump/landing) should also be there in each session to reap maximum benefits.
“For a normal individual, 40 contacts per session is enough, whereas for athletes this can increase to 60 contacts per session,” says Roy. “And there needs to be at least 48-70 hours of rest between two sessions of plyometrics as the body needs recovery time. So doing it, say, twice a week is good enough to get benefits. And for athletes, plyometrics exercises should not be done at least seven days prior to a tournament.”
Centre of gravity
At gyms, it is common to see people doing box jumps, a popular plyometric exercise. The idea of the exercise is to build strength in the lower limbs by jumping high.
“We may have seen many [people] jumping and managing to go higher by tucking their legs close to their chest,” says Roy. “This is a wrong technique which goes completely against the concept of plyometrics. This is a myth that by tucking your legs near to the chest and landing over, say, a 3ft box will give you benefits. The center of gravity of the body needs to be lifted to get the work done. This is the physics involved. We have seen basketball and volleyball players do it by lifting their waistline and not just achieving height by crouching.”
So just by landing over a box by tucking legs to the chest will give no benefit since the waistline will be lifted for only a few centimeters, he says.
Common plyometric exercises
- Lower body: skip jumps, squat jumps, countermovement jumps, standing broad jumps, jump to box, bounding, hopping
- Upper body: clap pushups, med-ball catch and throw
Advantages of plyometric exercises
- Injury prevention
- Muscular endurance development
- Power development
- Rehab facilitation (the final part of injury rehab just before returning to the playing field or to exercises).
- Plyometrics helps in connecting the strength of the body to the actual performance by increasing the strength and endurance level of an individual. But it needs to be done under proper supervision and guidance.
- Since plyometrics is a high-intensity exercise, it should be avoided altogether by those who are above 50 and not into any performance-sport activity. Plus, it is advisable to lose additional kilos from the body before including plyometrics into one’s regular routine.
- Landing and takeoff are equally important in plyometric exercises. Just as it is essential to lift the body’s centre of gravity by taking the waistline up during takeoff, appropriate landing is also important to avoid injuries.