A Practical Guide to Strength Training
Mark Bennett
Introduction
Rugby Union is a complex game. Required on-field actions are diverse, and this is reflected in the strength qualities that support rugby success. For example, maximal strength requirements are important for activities such as scrummaging and mauling, while explosive strength is a prerequisite for sprinting, tackling and rucking (Roberts, Trewartha et al, 2008. Tillin, Pain and Folland, 2013). The significance of strength qualities for rugby union players is reflected by the fact that levels of strength and power predict a players’ level of competition (Argus, Gill and Keogh, 2012). These facts ensure that maximising both strength and power is a major focus of the training plans of professional rugby players (Gannon, Stokes and Trewartha, 2016).
This chapter aims to provide an overview of a method to plan strength training in professional rugby union.
Muscular Contractions
Movement is the product of muscular contractions that exert forces on bones; there are three types of muscular contractions:
Eccentric where the muscle body lengthens; an example is the lengthening of the biceps muscle when a bar is lowered during a barbell curl.
Concentric where the muscle belly shortens; in a barbell curl this would be the action occurring in the biceps as the bar is raised.
Isometric contraction where no movement occurs and the muscle belly remains the same length. In the previously mentioned example of a barbell curl, if the bar were being held at 90° the bicep muscle would be undergoing an isometric contraction.
The potential for force production differs between these contraction types; eccentric contractions have the greatest potential for force production, while isometric contractions in turn have a greater potential for force production than concentric contractions. In the bicep curl example, eccentric force is on average 13% greater than isometric force and 40% greater than concentric force (Doss and Karpovich, 1965). We can lower heavier weights more easily than we can lift them.
Many movements (and most in rugby) consist of an eccentric (muscle stretching) contraction followed immediately by a concentric (muscle shortening) contraction. This is referred to as a reversible muscle action and is a result of the stretch-shortening cycle (SSC) (Zatsiorsky and Kraemer, 1995). If this shortening of the muscle immediately follows the lengthening of a muscle, the force of the shortening contraction is both more powerful and forceful and expends less energy in comparison to an isolated concentric contraction (Zatsiorsky and Kraemer, 1995. Verkhoshansky and Verkhoshansky, 2011). Simplistically the increased force, power and improved energy efficiency produced by the SSC is a result of energy stored in the stretched muscle and tendon, likened to an elastic band, that can be reused when shortening occurs. The SSC is very important for explosive performance in activities such as sprinting (Kubo, Kanehisa et al, 2000) and jumping (Kubo, Kawakami et al, 1999) but even at slower running speeds it has been estimated that it contributes to a 40% saving in oxygen use (Cavagna, Dusman et al, 1968). In athletes, strong muscles and stiff tendons ensure that the SSC is efficient and powerful (Zatsiorsky and Kraemer, 1995).
This chapter is a guide to planning. The point of introducing the concept of contraction types and the SSC is simply to ensure we realise that improving sports performance is more than simply increasing our maximal lifts in the gym.
