A comparison of time-motion analysis methods for field based sports.

PURPOSE: To assess the validity of a digitizing time-motion-analysis method for field-based sports and compare this with a notational-analysis method using rugby-union match play. METHOD: Five calibrated video cameras were located around a rugby pitch, and 1 subject completed prescribed movements within each camera's view. Running speeds were measured using photocell timing gates. Two experienced operators digitized video data (operator 1 on 2 occasions) to allow 2-dimensional reconstruction of the prescribed movements. RESULTS: Accuracy for total distance calculated was within 2.1% of the measured distance. For intraoperator and interoperator reliability, calculated distances were within 0.5% and 0.9%, respectively. Calculated speed was within 8.0% of measured photocell speed with intraoperator and interoperator reliability of 3.4% and 6.0%, respectively. For the method comparison, two 20-minute periods of rugby match play were analyzed for 5 players using the digitizing method and a notational time-motion method. For the 20-minute periods, overall mean absolute differences between methods for percentage time spent and distances covered performing different activities were 3.5% and 198.1 +/- 138.1 m, respectively. Total number of changes in activity per 20 minutes were 184 +/- 24 versus 458 +/- 48, and work-to-rest ratios, 10.0%:90.0% and 7.3%:92.7% for notational and digitizing methods, respectively. CONCLUSION: The digitizing method is accurate and reliable for gaining detailed information on work profiles of field-sport participants and provides applied researchers richer data output than the conventional notational method.