Plyometric Training, often referred to as explosive training, consists of quick, powerful movements involving a pre-stretch or countermovement that utilizes the stretch-shortening cycle (SSC). The primary goal of these exercises is to enable a muscle to reach maximal force in the shortest possible time. Plyo Boxes are a fundamental piece of equipment used to increase the intensity of these drills by providing a surface to jump onto, over, or off.
Plyometric actions rely on the integration of two physiological models that explain how force and speed are enhanced during explosive movements.
Elastic energy is stored in the series elastic component (SEC)—primarily the tendons—during a rapid stretch (eccentric action) and then released during a subsequent concentric action to increase total force production.
This model involves potentiation, where the force-velocity characteristics of the muscle are enhanced by the stretch reflex. Muscle spindles detect rapid stretches and send signals to the spinal cord, which results in a reflexive increase in agonist muscle activity.
The amortization phase, defined as the transition time between the eccentric and concentric phases, is the most critical factor in plyometric performance. It must be kept as short as possible (ideally less than 0.1 seconds) to prevent the stored elastic energy from dissipating as heat.
Plyo Boxes are used for a variety of drills classified by their intensity and movement patterns.
The athlete jumps from the ground onto the top of a box, landing in a half-squat position. Variations include single-leg box jumps, which are high intensity, and lateral box jumps.
In Depth Jumps, also known as drop jumps, the athlete steps off a box, lands, and immediately jumps vertically, horizontally, or onto another box.
The athlete starts with one foot on the box and one on the ground, jumping upward using the foot on the box to provide the driving force.
The Drop Freeze is a beginner-level drill in which the athlete steps off a box and freezes upon landing to focus on proper landing mechanics and force absorption.
For safe and effective training, Plyo Boxes and the surrounding environment must meet specific standards.
Boxes must be sturdy and are typically constructed from 3/4-inch plywood or heavy-gauge metal. The top surface should include a nonslip landing area such as rubberized flooring, treads, or sand-mixed paint.
Box heights range from 6 to 42 inches (15 to 107 cm), and the landing surface should measure at least 18 by 24 inches. Plyometric drills should be performed on shock-absorbing surfaces such as grass, rubber mats, or suspended floors, while concrete and tile surfaces are not recommended.
Athletes weighing over 220 pounds (100 kg) should avoid high-volume Plyometric Training and limit Depth Jumps to boxes no higher than 18 inches (46 cm).
Different populations require specific considerations when incorporating PlyometricTraining.
Lower-intensity plyometric activities such as skipping and hopping are beneficial for children and adolescents. However, high-intensity Depth Jumps are contraindicated for prepubescent children because their epiphyseal growth plates have not yet closed.
Older adults should use caution when performing Plyometric Training, focusing on no more than five low-to-moderate intensity exercises and allowing three to four days of recovery between sessions.
Before advancing to high-intensity plyo box drills, athletes should demonstrate proper landing technique, including shoulders over knees, knees over toes, avoidance of valgus or inward knee movement, and a solid base of strength.
