Research studies indicate that, by determining the physiological load placed on athletes during competitions, it can aid in the development of strength and conditioning programmes, according to the specific demands placed on athletes (Deutch et al., 1998; Kay&Gill, 2004). Physiological data, specifically on rugby union players, are furthermore limited and more information is needed (Banfi et al., 2006; Deutch et al., 2007). The aim of the study was to investigate the physiological demands of South African male U/21 club rugby players and to establish the correlation between physiological demands experienced during rugby games and practice sessions. Scientific methods to describe physiological demands in sport that are used are heart-rates and blood-lactate measurements (Eniseler, 2005). A group of U/21 rugby players (n=15) of the University of Pretoria (Tuks) rugby club participated in this study. Components that were tested included blood-lactate concentrations and heart-rates during rugby match and practice sessions. The data of the Tuks U/21 team was statistically analysed with descriptive statistics (means and standard deviations). Significant differences between match and practice sessions, at a p-value of P < 0.05, were determined by a dependent t-test. An independent t-test was used to determine significant differences between the forward and backs group (Thomas&Nelson, 2005). The results showed that statistically significant differences (p<0.05) were found between mean heart-rate in the rugby match (154.40 ±13.53) and practice sessions (138.33±4.81). No significant differences were found between peak lactate measurements in the match (5.39 ±2.44) and practice sessions (4.93±1.83). Between the forward and backs group no statistical significance could be found for average heart-rate and blood-lactate levels in practice sessions and the match. The findings of the present study indicate that rugby union matches for club level U/21 players are an intermittent type of activity, with both the use of aerobic and anaerobic energy systems. Additional research on more amateur rugby clubs is needed to extend the knowledge of club level coaches. / Dissertation (MA)--University of Pretoria, 2012. / Biokinetics, Sport and Leisure Sciences / unrestricted