Last update:
29-Sep-2017

OBJECTIVE Assessment of the differences in isokinetic concentric strength of the knee extensors and flexors in soccer players measured before the end of the season (April) in the years 2013 and 2014.

METHOD Measurements were made in the April of 2013 and 2014 in 13 professional soccer players of hamstring (H) and quadriceps (Q) peak torque-ratio (PT), and total work (TW) at two testing speeds (60º·s^-1 and 180º·s^-1), expressed as per-kg body weight (Nm·kg^-1), and peak muscle torque (PT) (Nm), using an IsoMed 2000-dynamometer chair. Repeated measures analysis (based on general linear modeling) was used to assess the differences.

RESULTS Between 2013 and 2014 a positive Δ-change was observed in mean match playing time (+35%, p=0.001), but less time had been spent during training sessions on isokinetic strength training. Correlation analysis according to the different velocities showed significantly negative correlation in 2013 between the playing time and TWQ at 60ºs^-1 and at 180ºs^-1 between TWQ and age (p<0.05). PT was lower for the players in 2014 than in 2013 at 60ºs^-1: Q (Nm)–(-32.0, p=0.002) v 60ºs^-1 Q (Nm kg^-1)–(-0.40, p=0.002), as was the percentage of ratio (%)–(^-13.1, p<0.001) and TWH (-93, p=0.043). In 2014, positive correlation was found of 60ºs^-1 PTH (Nm), 60ºs^-1 PTH (Nm·kg) and 180ºs^-1 PTQ (Nm) measurements with the playing-time (p<0.05). In 2014 Angular velocity of 180ºs^-1 PT was lower in 2014 at H-(Nm) (-9.8, p=0.008), ratio (%) (-21.1, p<0.001) and in TWH (^-144, p=0.045).

CONCLUSIONS The limited time spent on individual training sessions in the second year of testing, because of higher mean match-play time and the optional nature of the isokinetic concentric strength training, appeared to affect negatively the maximum torque of the knee and thus increase the risk for severe injuries.

Key words: Angular velocity, Concentric maximum strength, In-season, Isokinetic, Leg strength, Soccer players.