Heart rate and graded maximal test values to determine rugby union game intensities of adolescent boys

Abstract

Despite the need to investigate the match characteristics of junior rugby union players in order to determine the physical demands that are placed on these players, only three studies have thus far focussed on the match characteristics of adolescent rugby players. It is against this problem, that the purposes of this study were firstly, to determine the heart rate and standard graded maximal oxygen uptake test values of u/15 high school rugby players; Secondly, to determine the intensities of u/15 high school rugby union games when making use of heart rates and standard graded maximal oxygen uptake test values; Thirdly, to determine if the absolute and relative total match time that is spent in each heart rate intensity zone during u/15 high school rugby games are significantly different when making use of heart rates and standard graded maximal oxygen uptake test values; Fourthly, to determine the significant positional differences in the heart rate and standard incremental maximal oxygen uptake test values of u/15 high school rugby players; Lastly, to determine the significant positional differences in the intensities of u/15 high school rugby union games when making use of heart rates and standard incremental maximal oxygen uptake test values. The heart rates (HR) of twenty-four u/15 rugby union players (15 forwards and 9 backs) from the 1st and 2nd teams of a high school in the Potchefstroom area of the North-West Province in South Africa were monitored for the duration of several home games during the 2012 season. Furthermore, the body stature and body mass of each player were measured and each player was subjected to a standard graded maximal oxygen uptake test in the periods between rugby games. The individual heart rate intensity zones were determined by making use of this test: heart rates that corresponded to the exercise intensities below the ventilatory threshold (VT) were classified as low intensity heart rates; heart rates that corresponded to the exercise intensities between VT and the respiratory compensation point (RCP) were classified as moderate intensity heart rates and heart rates that corresponded to the exercise intensities above RCP were classified as high intensity heart rates. The results firstly indicated that adolescent rugby players showed an average VO2max value of 49.20 ml∙kg-1∙min-1, which they obtained at an average VO2max HR value of 196.94 bpm; a VT of 77.67% (154.33 bpm) of the HRmax that was reached at a VO2 of 31.08 ml∙kg-1∙min-1; a RCP at 87.38% of VO2max (42.80 ml∙kg-1∙min-1) at an average heart rate of 184.4 bpm which was determined to be 92.72% of the HRmax during a standard graded maximal oxygen uptake test. Secondly, the heart rate for the three intensity zones (low (LIZ), moderate (MIZ) and high (HIZ)) were determined to be: <154.33 bpm, 154.33-184.35 bpm and >184.35 bpm, respectively. The majority of match time was spent in the MIZ (27 min and 49 s, 56.34% of the total match time), followed by the HIZ (10 min and 55 s, 23.03% of the total match time) and the LIZ (9 min and 6 s, 19.95% of the total match time). However, the average duration of low intensity bouts was higher (67 s) compared to the low (40 s) and high (39 s) intensity bouts, respectively. Lastly, significant differences were observed for all the above-mentioned values between the LIZ and MIZ as well as between the MIZ and the HIZ. Positional comparison revealed that the backs obtained significantly higher average HR at the VT and HR’s for the LIZ and MIZ as well as significantly lower average VO2 at RCP compared to the forwards. With regard to the match analysis related results, the forwards obtained significantly lower values for the total time and relative total time spent in the LIZ compared to the backs (forwards: 05 min 22 s; backs: 15 min 11 s and forwards: 12.5%; backs: 26.4%). From the results with regard to the duration of different intensity bouts, it is also clear that forwards spent less time on low intensity bouts (33 s versus 51 s), although the average time period that was spent on high intensity bouts was more or less the same between forwards and backs (39 s versus 37 s). This may be an indication of a higher work to rest ratio and less recovery time during rugby union games for the adolescent forwards compared to the backs. To conclude, the results of this study seem to suggest that the positional specific intensities of u/15 high school rugby union games can be determined and compared by making use of these players’ heart rates and standard graded maximal oxygen uptake test values. This is an important finding due to the limitations that have been identified with regard to the use of other match analysis methods. It also stresses the need for more rugby union match analysis studies on junior rugby players which make use of the last-mentioned method in order to determine the energy requirements and match demands of this group of players more accurately.