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Introduction
LTPD Pathway
Functional Screening
Anatomical Adaptation
Game Demands
Conditioning for Rugby
Periodisation in Rugby
Content
Questions

Defining speed

The role of genetics

Genetics play a significant role in speed. For example, a speed athlete will have a higher percentage of what we call fast-twitch fibres, greater fibre bundle (fascicle) length and more efficient alignment of muscles to their long bones (Cissik, 2004). Nevertheless, all players have the capacity to improve their speed, regardless of their physical and physiological structure.

“Genes influence potential, but they don’t ensure it.”
(Sharkey & Gaskill, 2006)

Genetics may predetermine muscle fibre composition, i.e. the ratio of fast-twitch and slow-twitch fibres and while training may not be able to change this ratio, training can certainly alter how these fibres work and how they are used (Gambetta, 1991, Cissik, 2004). For example, training can increase the size of the fibres, the number of fibres recruited and lead to more co-ordinated recruitment (Bosco, 1999). Thus, while some players are born fast, all players can improve their speed capabilities.