Are There Differences in Concentric Isokinetic Strength Perfor-Mance Profiles between International and Non-International Elite Soccer Players?

Robert Śliwowski,Monika Grygorowicz,Andrzej Wieczorek,Łukasz Jadczak,Jakub Marynowicz

doi:10.3390/ijerph18010035

Abstract

The purpose of this study is to evaluate the differences in concentric isokinetic strength characteristics of the knee extensor and knee flexor musculature between international (IL) and non-international level (N-IL) soccer players. The second aim is to establish strength symmetry status in knee muscles for dominant (DL) and non-dominant (NDL) legs for both within and between groups. 100 male top elite soccer players (IL: n = 36, age = 27.5 ± 3.4 years and N-IL: n = 64, age = 27.7 ± 6.4 years) underwent concentric isokinetic strength tests, using a Biodex System 3 dynamometer. Results indicate that statistically significant differences between groups were noted for peak torque of hamstrings (PT-H), hamstrings/quadriceps (H/Q) ratio, and total work of hamstrings (TW-H), where mean values for the IL were similarly higher than for the N-IL group (p = 0.006, p < 0.001, and p = 0.012, respectively). Our results also showed statistically significant differences for peak torque of quadriceps (PT-Q), PT-H, total work of quadriceps (TW-Q) and TW-H between legs, where mean values noted for the DL were higher than for the NDL for both groups (p = 0.021, p < 0.001, p = 0.006, and p = 0.004, respectively). Additional results show that IL players presented more symmetrical strength between legs than N-IL. The results of this study indicate that that the greatest differences in isokinetic strength performance across players at different soccer levels relate to the hamstring muscle. As a result, systematic strength training of these muscle groups is strongly recommended.

Highlights

Isokinetic testing is one of the most commonly used methods of assessment for a wide range of strength evaluations
There was a main effect for groups (F1,98 = 7.903, P = 0.006, partial η2 = 0.075; Figure 1C), where the mean values for IL were greater than non-international level (N-IL), and for legs (F1,98 = 23.503, P < 0.001, partial η2 = 0.193; Figure 1D), where the mean values for dominant leg (DL) were greater than non-dominant leg (NDL)
There was a main effect for groups (F1,98 = 6.522, P = 0.012, partial η2 = 0.062; Figure 2C), where the mean values for IL were greater than N-IL, and for legs (F1,98 = 8.520, P = 0.004, partial η2 = 0.079; Figure 2D), where the mean values for DL were greater than NDL

Summary

Introduction

Isokinetic testing is one of the most commonly used methods of assessment for a wide range of strength evaluations. Away from PT, the most commonly described variables in isokinetic tests for soccer players’ knee muscles are: hamstring/quadriceps ratio, total work, average power, and fatigue index. Previous research has identified the isokinetic strength of knee extensor and flexor muscles as differentiating factors between soccer players of playing levels [1,2,3,4,5,6,7] and positional differences [8,9,10,11]. Some prior research indicates that soccer playing leads to a significant increase in strength in the muscles surrounding the knee [12]. Lehance et al [4] reported that concentric PT of the extensors and flexors increases

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