Abstract
Background:During soccer-specific movements, the strength of knee extensors and flexors is of great importance and achieving certain strength ratios between the two has been identified as an important parameter for reducing the risk of soft tissue injuries around the knee.Objective:The aim of the study was to evaluate changes in isokinetic strength of the knee flexors and extensors and their strength ratios in elite adolescent soccer players.Methods:Before and after 10 weeks of standard pre-season soccer training with progressive eccentric hamstring exercises, the players (n=18; age 17.1±0.4 years) participated in isokinetic testing to assess concentric and eccentric peak torque at 60°·s-1.Results:After 10 weeks of training, the peak eccentric torque of the non-dominant quadriceps increased (p=0.018; ω=0.24). Additionally, the average eccentric work increased in the dominant hamstrings (p=0.007; ω=0.23), dominant quadriceps (p=0.02; ω=0.31), non-dominant hamstrings (p=0.003; ω=0.25 and non-dominant quadriceps (p=0.01; ω=0.37). Lastly, the isokinetic functional ratio (eccentric hamstrings-to-concentric quadriceps) increased in favor of eccentric hamstring strength in the non-dominant limb (p=0.04; ω=0.31).Conclusion:The results of the study indicate that pre-season training induced suboptimal changes in the isokinetic strength of the knee flexors and extensors in elite adolescent soccer players. However, the lack of injuries combined with an apparent lack of preparedness explained by slow velocity isokinetic testing indicates that future research should investigate other forms of strength testing to determine soccer-specific preparedness such as isokinetic dynamometry at higher speeds (i.e.180°.s-1or 240°.s-1) and traditional weight-room testing such as 1RM tests.
Highlights
Strength is a component of fitness that is crucial for athletes in terms of sports performance, and in terms of injury prevention [1, 2]
The main findings of this study were that: 1) peak torque (PT) significantly changed only in the non-dominant leg (NL) knee extensors during eccentric isokinetic actions; 2) eccentric average work (AW) increased in the knee extensors and flexors of the dominant leg (DL) and NL; and 3) the H:QFUNC ratio increased in the NL but no changes were present for the H:QCONV
These data suggest that 10 weeks of pre-season soccer training including eccentric hamstring exercises may not have affected the maximal strength, but may have increased the ability for the players to maintain the eccentric torque during isokinetic testing evidenced by the greater AW
Summary
Strength is a component of fitness that is crucial for athletes in terms of sports performance, and in terms of injury prevention [1, 2]. Absolute knee flexor and extensor strength play an important role in performance and injury prevention, the relationship between hamstring and quadriceps strength is an important factor to consider when aiming to reduce the risk of soft tissue injuries around the knee [9 - 11]. During soccer-specific movements, the strength of knee extensors and flexors is of great importance and achieving certain strength ratios between the two has been identified as an important parameter for reducing the risk of soft tissue injuries around the knee
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