Validity and reliability of 6-a-side small-sided game locomotor performance in assessing physical fitness in football players

In order to determine whether small-sided game ( SSG) locomotor performance can serve as a fitness indicator, we ( 1) compared 6- a- side ( 6v6) SSG- intensity of players varying in fitness and skill, ( 2) examined the relationship of the 6v6- SSG and Yo- Yo IR2 and ( 3) assessed the reliability of the 6v6SSG. Thirty-three professional senior, 30 professional youth, 62 amateur and 16 professional woman football players performed 4 x 7 min 6v6- SSGs recorded by a Local Position Measurement system. A substantial subgroup ( N = 113) also performed the Yo- Yo IR2. Forty- seven amateur players performed two or three 6v6- SSGs. No differences in 6v6- SSG time- motion variables were found between professional senior and professional youth players. Amateurs showed lower values than professional seniors on almost all time- motion variables ( ES = 0.59. 1.19). Women displayed lower high- intensity time-motion variables than all other subgroups. Total distance run during 6v6- SSG was only moderately related to Yo- Yo IR2 distance ( r = 0.45), but estimated metabolic power, high speed (> 14.4 km center dot h(-1)), high acceleration (> 2 m center dot s(-2)), high power (> 20 W center dot kg(-1)) and very high (35 W center dot kg(-1)) power showed higher correlations ( r = 0.59- 0.70) with Yo- Yo IR2 distance. Intraclass correlation coefficient values were higher for total distance ( 0.84) than other time- motion variables ( 0.74. 0.78). Although total distance and metabolic power during 6v6- SSG showed good reproducibility ( coefficient of variation ( CV) < 5%), CV was higher ( 8- 14%) for all high- intensity time- motion variables. It was therefore concluded that standardised SSG locomotor performance cannot serve used as a valid and reliable fitness indicator for individual players.