Quantifying change of direction load using positional data from small-sided games in soccer.

PURPOSE: Quantifying change of direction (COD) load through positional data from small-sided games (SSG) and assess its criterion and construct validity. METHODS: Elite male youth soccer players (n = 25, 16.8 ± 1.3 years) played three SSG (5v5, 5×4 min) with different field dimensions (small [40×30 m], medium [55×38 m], large [70×45 m]). Positional data of the players was obtained with a Local Position Measurement system. COD load (AU) was quantified based on the combination of velocity and change in heading direction. Additionally, total distance covered, running distance, acceleration count, deceleration count, and Rating of Perceived Exertion were measured. Criterion validity was assessed by correlating COD load and the load indicators. Construct validity was determined by testing the differences between the SSG field dimensions. RESULTS: Strong correlations were determined between COD load and total distance covered (r = 0.74, p < .01) and running distance (r = 0.84, p < .01). Middle and large field size resulted in highest COD load (p < .05). CONCLUSION: These results suggest that the COD load measure shows sufficient criterion and construct validity.

Seasonal Training Load and Wellness Monitoring in a Professional Soccer Goalkeeper.

The purpose of this investigation was to (1) quantify the training load practices of a professional soccer goalkeeper and (2) investigate the relationship between the training load observed and the subsequent self-reported wellness response. One male goalkeeper playing for a team in the top league of the Netherlands participated in this case study. Training load data were collected across a full season using a global positioning system device and session-RPE (rating of perceived exertion). Data were assessed in relation to the number of days to a match (MD- and MD+). In addition, self-reported wellness response was assessed using a questionnaire. Duration, total distance, average speed, PlayerLoad™, and load (derived from session-RPE) were highest on MD. The lowest values for duration, total distance, and PlayerLoad™ were observed on MD-1 and MD+1. Total wellness scores were highest on MD and MD-3 and were lowest on MD+1 and MD-4. Small to moderate correlations between training load measures (duration, total distance covered, high deceleration efforts, and load) and the self-reported wellness response scores were found. This exploratory case study provides novel data about the physical load undertaken by a goalkeeper during 1 competitive season. The data suggest that there are small to moderate relationships between training load indicators and self-reported wellness response. This weak relation indicates that the association is not meaningful. This may be due to the lack of position-specific training load parameters that practitioners can currently measure in the applied context.