INTRODUCTION: The Change of Direction Speed is one the most important factors that influences efficiency in ballgames. Different authors came up with varied findings while carrying out internationally standardized COD tests and studying their connection with dynamic leg strength. METHODS: Subjects: Forty-nine elite young soccer players (U16-U17; 178.59±6.29; 69.08±7.78). Measured body parameters [1]: Height; Weight; Right Leg Lean Mass (RLLM, kg) Left Leg Lean Mass (LLLM, kg). Change of Direction Speed [3]: Illinois Agility Test (IAT, s), 505 Right and Left change (s). Isokinetic Knee Strength parameters [2]: Extension and flexion right and left leg 2 and 15 repetition (N); H/Q Right; H/Q Left (%). CMJ (cm), CMJ Concentric and Eccentric averages (N), CMJ Flight Time (s). Instruments: InBody770, Witty Wireless Training Timer; HumacNorm isokinetic dynamometer; ForceDecks. Data processing: IBM SPSS Statistics 28 (p<.05). RESULTS: The young soccer players` lean leg mass turned out to be symmetric according to our research (RLLM, 10.07±1.02; LLLM, 10.01±.95). They performed at COD tests much better than the average at international level (IAT, 15.56±.40; COD505L, 2.57±.12; COD505R, 2.55±.12). Their average performances measured with isokinetic dynamometer were well balanced: H2ER (224.43±32.27), H2EL (218.09±33.66), H2FR (148.89±29.62), H2FL (147.86±22.44), H/Q2R (63.91±12.44), H/Q2L (67.83±10.03), H15ER (125.37±16.48), H15EL (125.77±16.85), H15FR (101.17±15.21), H15FL (102.48±14.96), H/Q15R (78.70±10.06), H/Q15L (84.94±15.90). The data measured on force plate were according to their age: CMJ (32.28±3.97); CMJC (1467.90±139.07); CMJE (728.45±80.48); CMJFT (.77±.11). The Changes of Direction Speed (IAT) showed no significant correlations with the right and left leg lean mass, or any isokinetic knee strength (extension and flexion) parameters. The COD505 tests showed strong correlations when carried out with different legs (r=.769; p<0.001), they only related to one CMJ parameter (r=.448; p<.05), it was only related to Left Leg Lean Mass (r=-.447; p<.05). However, the CMJ Contractive averages showed strong correlations in the case of both legs (r=.692; and r=.707; p<.001). The CMJ Eccentric averages and the Humac2FR, 2FL, 15ER and 15FL were also related to each other (r=.488 - .744; p<.05). CONCLUSION: It is difficult to find the relations between leg dynamic strength and traditional CODS tests. That is why we suggest improving bothskills at the same time.
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