To determine if K-D scores differed between competitive youth soccer players and recreational youth soccer players ages 8-12.


Prospective cohort study during the spring and fall soccer seasons of 2017. Participants were 8-12 years of age and were enrolled in recreational or competitive soccer.


Participants performed the K-D test before the first practice of the soccer season and during the last two weeks of the season. The main outcome measure was the time required to complete the K-D test before and after the soccer season in participants without a positive K-D screening for concussion.


Forty participants (19 competitive and 21 recreational) completed the study. The preseason recreational players (66.04s, SD = 15.22s) vs competitive players (59.88s, SD = 13.94s) had a mean difference of 6.16s (Z = .96, p = .34). The post-season recreational players (60.45s, SD = 13.46) vs competitive players (50.50s, SD = 8.49) had a mean difference of 9.95s (Z = 2.31, p = .02).


Level of play may influence performance on the K-D. Future studies of visual efficiency in youth athletes may also provide insight into differences in performance of the K-D.

Summary Points

  • Post-season recreational players performed worse (slower) compared to competitive players (mean difference 9.95s).
  • This demonstrate a potential difference in ocular efficiency in recreational versus competitive youth soccer players.
  • Setting a single threshold for a positive concussion screen across all youth soccer players could result in false positive scores among recreational players and false negative scores among competitive players. Therefore, it is imperative to establish an individual baseline for comparison when screening for concussive events.
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