Optimal Training for Movement Acquisition and Transfer: Does 'Externally-Focused' Visual Biofeedback Promote Implicit Motor Learning?

CONTEXT: Visual biofeedback has been shown to facilitate injury-resistant movement acquisition in adolescent athletes. Visual biofeedback is typically thought to foster implicit learning, by stimulating athletes to focus attention externally (on movement outcome). However, biofeedback may also induce explicit learning, if the athlete uses the visual information to consciously guide movement execution (using an internal focus).

OBJECTIVE: To determine the degree to which athletes report statements indicative of implicit or explicit motor learning after engaging in a visual biofeedback intervention.

DESIGN: Prospective cohort.

SETTING: 3D motion analysis laboratory.

PATIENTS OR OTHER PARTICIPANTS: Twenty-five adolescent female soccer athletes (15.9±0.9 yrs, 164.9±5.67 cm, 58.9±10.3 kg).

INTERVENTIONS: Standard six-week neuromuscular training intervention (three 90-minute sessions/week), with added visual biofeedback sessions (two sessions/week). For the biofeedback training, participants performed squatting and jumping movements while interacting with a visual rectangular stimulus that mapped key parameters associated with injury risk. After the last biofeedback session in each week, participants answered open-ended questions to probe learning strategies.

MAIN OUTCOME MEASURES: Responses to the open-ended questions were categorized as "externally focused" (i.e., on movement outcome, suggestive of implicit learning), "internally focused" (i.e., on movement itself; suggestive of explicit learning), "mixed focus", or "other."

RESULTS: 171 open-ended responses were 25 collected. Most of the responses that could be categorized (39.2%) were externally focused (41.8%) followed by mixed (38.8%), and internally focused (19.4%). The frequency of external focus statements increased from week 1 (18%) to week 6 (50%).

CONCLUSIONS: While most statements were externally focused (suggesting implicit learning), the relatively large proportion of internal/mixed focus statements suggests many athletes also engaged in explicit motor learning, especially in early practice sessions. Therefore, biofeedback may impact motor learning through a mixture of implicit/explicit learning.