Explosive power is something many athletes strive for. The ability to go from a standstill to an immediate burst of power in the fastest time possible is an advantage in many activities, but training this ability has always proven to be an elusive feat. It seems some athletes have it and others just don’t. Fortunately, the training method commonly referred to as plyometrics can help improve explosive power.
The term plyometrics refers to explosive exercises like drop-jumps (dropping off of a box and immediately jumping upon landing). These exercises are practiced in a wide variety of sports. However, although plyometrics are widely utilized, they haven’t been studied as much as exercises focused on strength, speed, or endurance. Most powerlifters have at least a general idea of how many times they need to bench press to achieve a bigger lift. Most runners know what surfaces they prefer to run on to get the most out of their mileage. But these aspects of plyometrics elude athletes and coaches, which is why they were tackled in a recent study in the Journal of Strength and Conditioning.
Properly used, the term plyometrics refers to any activity involving the stretch-shortening cycle (SSC). The SSC is the term for the ergogenic effect of performing an eccentric contraction prior to a concentric contraction. These are a lot of heavy sports science terms, but it’s simpler than it sounds.
SSC is often described as a reflex that protects joints from harm. Any time a muscle is stretched it stores energy like a spring. If you engage that muscle right after it’s been stretched, it will be stronger than if you didn’t. This is why you wind up when throwing a punch. If the stretch is fast enough, the reflex kicks in as a joint-protecting mechanism. It’s like when you go to the doctor and they hit your knee with the hammer. This causes a rapid stretch of your patellar tendon similar to what an eccentric portion of a squat does, and the resulting reflex is the contraction of the muscles that control that tendon – the quads. This reflex results in a kick.
Now combine these principles into a training methodology and we have what we call plyometrics, or plyos for short. Although plyos apply to any exercise with an SSC, we usually only call the really explosive exercises plyometrics. In the study, the researchers looked at various volumes of drop-jumps and surfaces to see what had the greatest benefit on a variety of tests, like maximal strength, explosiveness, and sprinting.
Unsurprisingly, there were differences for both volume and surface. Out of the three groups that performed drop-jumps, two performed them at moderate volume – a total of 780 jumps over seven weeks – but on either a wood floor or a softer gymnastics mat. The third group was the high-volume group, performing 1,560 jumps total.
All the groups improved their drop-jumps, which makes sense because that’s what they trained. Only the high-volume group got faster at sprinting. The moderate volume group jumping on the wood floor demonstrated the greatest efficiency of all the protocols tested. Jump for jump, the hard surface showed the greatest results.
Ultimately, less is more. In this study, moderate-volume plyos performed on a hard surface were most effective in improving performance in all areas, except for sprinting in untrained individuals.
1. RR Campillo, et. al., “Effects of plyometric training volume and training surface on explosive strength,” Journal of Strength and Conditioning, 27(10), 2013.
Photo courtesy of CrossFit Impulse.