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From explicit to implicit learning in ACL injury prevention?
  1. A Benjaminse1,2,
  2. M Bisschop1,
  3. P Schoenmakers1,
  4. E Otten1
  1. 1Center for Human Movement Science, University Medical Center Groningen; University of Groningen, Groningen, The Netherlands
  2. 2School of Sports Studies, Hanze University Groningen, Sports Field Lab Groningen, Groningen, The Netherlands


Background Despite reported early successes, anterior cruciate ligament (ACL) injury rates have not diminished. Currently explicit learning strategies are mainly used for prevention. However, this may be unsuitable for the control of complex motor skills.

Objective The purpose was to investigate explicit and implicit learning while keeping balance on a 4 mm narrow ridge. Results can contribute to the development of ACL injury prevention programs.

Design Randomised controlled trial.

Setting Laboratory based study with recreational athletes.

Participants 60 healthy subjects between 18 and 24 years were recruited from the university population. Females (n=36) and males (n=24) were equally distributed over three groups; implicit learning, explicit learning and the control group.

Interventions Balance time on the ridge was investigated where the groups received different types of feedback after each trial; implicit (visual feedback from video of the best trial so far), explicit (instructions) and no feedback. During the retention test after 2 weeks none of the subjects received any feedback. All subjects conducted 25 trials during both measurements. The independent t-test was used in SPSS 16.0 (SPSS Inc., Chicago, IL) where the alpha level was set a priori at p<0.05.

Main outcome Measures Grow of balance time (based on first grade regression line).

Results Growth during the intervention for implicit, explicit and control was 2.36 (SD ± 3.21; p=0.009), 1.53 (SD ± 2.09; p=0.001) and 0.84 (SD ± 1.26; p=0.209) respectively. Growth of the implicit group was significantly different from the control group (p=0.03). No other significant differences were found. Growth and group differences were not significant from each other during the retention test (p>0.05).

Conclusion Before use in the clinical setting, future research is needed to evaluate and improve the learning strategies. SD were high, which could explain the results.

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