## 4 Discussion
By comparing the test results of the Yo-Yo IR1 test to the results of the GBPT, the indirect validity of the Yo-Yo IR1 test was determined, which is important for the potential use of the test in elite team handball. The mean body mass, body height and age in the present group of players were 72.5 kg, 175 cm and 25 years, respectively, which is comparable to that of other female adult top-elite field team handball players from the Danish Premier Female Team Handball League [13], National players from the First Spanish Team Handball League [37] and players in the Czech and the Serbian Female National Handball Team, respectively [38; 39]. The mean total running distance covered in the Yo-Yo IR1 test was -1330 m, which is somewhat lower (~7%) than previously reported in adult top-elite field team handball players from the Danish Premier Female Team Handball League (~1440 m, [11]) and the Brazilian Female National Handball Team (~1440 m, [40]), and also much less compared to female youth (mean age 17 years) top-elite international players (~1660 m, [41]). One of the reasons for this difference could be due to the timing of the testing in the present study. The tests were carried out in the first days after the summer break--in the early phase of the preparation period--where the players were not used to team handball-like movements such as accelerations, decelerations and change of directions in the same manner as during the competitive season. If the tests had been performed during the competition season, the test results would most certainly have been better as previously shown in other studies with female adult top-elite team handball players [11; 42]. One of the participating clubs performed the Yo-Yo IR1 test much later in the season--in the competition period just before the play-offs--and achieved significantly higher mean results. However, all the mentioned results for adult players are still lower than previous Yo-Yo IR1 test performances, for example measured in the Danish Female National Team, which won Olympic Gold in 2000 (~1510 m, mean body mass 68,5 kg, \(n=16\)), finished fourth in the World Championships in 2001 (-1675 m, mean body mass 65,5 kg, \(n=12\)) and won the European Championship in 2002 (-1540 m, mean body mass 66 kg, \(n=18\)) [42]. This may indicate that the mean results of the Yo-Yo IR1 test has not improved significantly for at least female adult top-elite field team handball players the last couple of decades. One reason could be that the mean body mass (and hence probably the muscle mass) has increased markedly for female adult elite field players since the millennium [13; 37; 43; 44]. However, the mean body mass values of present-day female elite teams seem to have almost reached a maximum. Today's female adult elite team handball players are even more professional and better physical trained than two decades ago. Nevertheless, the players are also larger with increased body mass, which may have a negative impact on the Yo-Yo IR1 test performance due to the many repeated decelerations, accelerations and 180 degrees change of directions during the test. In return, the increased body anthropometry will enhance the on-court performance in other important match activities as tackling, screening, blocking, throwing, jumping and breakthroughs. Studies have shown that body height, body mass and thus muscle mass and maximum muscle strength have important influence on especially the technical playing actions and hence on the match performance in modern female adult top-level team handball [2; 7; 13; 37; 45; 46; 47]. Likewise, muscle power is an essential factor in female team handball, which is required in actions such as sprinting, one-to-one situations and rapid change of directions. An example of such players is depicted in Figure 2A (in the bottom of the figure). Two players with high body mass (80.8 kg and 79.9 kg) performed badly in the Yo-Yo IR1 test (880 m and 1000 m).