Physical fitness of elite women's rugby union players over a ...

league players, respectively whereby no significant positional differences were found for the
vertical jump test (Table IV). Such comparisons may be erroneous given the changes in
vertical jump assessment over this period (e.g. chalk board versus Vertec) (Duthie et al.,
2003).
Recently, Crewther et al., (2009) reported, that the absolute expression of squat jump and
bench throw peak power was greater for the forwards than the backs when assessing lower
and upper body muscle power respectively. After normalizing the power results using ratio
scaling (power/body mass), the backs revealed superior performance in these tests, which is
consistent with previous research in rugby union players (Maud, 1983). Ratio scaling has been
criticised as it assumes a linear relationship between body size and performance, thereby
penalizing heavier individuals and showing bias towards lighter individuals (Atkins, 2004;
Jaric, Mirkov, & Markovic, 2005). There was no performance difference between the backs
and forwards after allometric scaling using either the proposed or the derived exponents. The
present study did have limitations, as scaling power values for body mass, using either the
ratio or allometric methods, did not account for body composition differences between
individual players (e.g. fat mass, muscle mass) (Crewther et al., 2009) and the regional
distribution of body and muscle mass, which can vary between forwards and backs (Bell,
Evans, Cobner, & Eston, 2005).
2.4.7 Muscle Endurance
Muscle endurance is dependent on the muscle being able to contract repetitively without
developing fatigue. A combination of muscle strength, metabolic characteristics and local
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