Inter-limb asymmetries and sports performance. From assessment to the application of a sport-specific iso-inertial resistance training in young athletes
- Autores: Marc Madruga Parera
- Directores de la Tesis: Daniel Romero Rodríguez (dir. tes.), Azahara Fort Vanmeerhaeghe (codir. tes.)
- Lectura: En la Universitat de Girona ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: Anthony J. Turner (presid.), Víctor López Ros (secret.), Nuno Miguel Correia Leite (voc.)
- Programa de doctorado: Programa de Doctorado en Biología Molecular, Biomedicina y Salud por la Universidad de Girona
- Materias:
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- Resumen
Handball and tennis are defined as multi-directional, high-intensity intermittent sports both metabolically and in a muscularskeletal sense, characterised by the explosivity of the various specific skills produced in the game, and with the common element of using the upper limb to throw or hit the ball.
Inter-limb asymmetries have been defined as the differences in strength or skill between these segments. Regarding detecting these imbalances, vertical jump tests have been shown to be the tests that present the greatest asymmetries among the different skills studied in published papers. This scientific literature has also focused on demonstrating the negative effect that inter-limb asymmetries have on the performance of skills such as the jump, the change of direction, and the sprint.
A consistent finding across different types of populations is that resistance training has positive effects on health, performance, and injury prevention. With the aim of improving performance, in recent years iso-inertial resistance training has evolved to the point where it is considered to be a tested method of resistance training.
The aim of this doctoral thesis is to quantify and analyse asymmetries between limbs in jump, change of direction, sprint, and muscle power assessments, and to identify the effects these asymmetries have on performance of the different skills assessed. Another aim is to identify the effects of strength training with iso-inertial resistance and traditional resistance in young athletes.
Four inter-disciplinary studies (Studies 1,2,3, and 4) and one longitudinal study (Study 5) were carried out to meet these objectives. Studies 1 and 2 comprise the first part of the compendium of papers. The aims of Study 1 were: to quantify the inter-limb asymmetries in jump, balance, and change of direction (COD) tests, and to classify the level of asymmetries among groups depending on the chronological and maturational ages of the subjects, young, international-level athletes. The results of the chronological and maturational analyses of the inter-limb asymmetries – in relation to peak height velocity (PHV) - showed no differences between groups. Furthermore, the greatest asymmetries were found in the unilateral countermovement jump (UCMJ), which can be considered as a useful test to detect imbalances between limbs. Study 1 confirmed the need to investigate COD tests that are more precise at detecting asymmetries, given that total time appears to be a deficient measure to obtain these variables. Last, the highest neuromuscular asymmetries found in this first study were in the groups pre-PHV / U12 and circa-PHV / U14, and especially in the UCMJ in the latter group.
Study 2 was a follow-on from Study 1, the objectives of which were to determine the relationships between inter-limb asymmetries and measures of performance of different skills, and to quantify whether the asymmetries consistently favoured the same side in three frequently used unilateral jump tests, all with adolescent handball players. The results showed that the vertical, lateral, and horizonal jump asymmetries and the asymmetries based on distance were associated with reduced performance in the jump, COD, and repetition of COD tests, but did not affect linear speed. Furthermore, a low coincidence between the asymmetries and the preferred leg, determined to be the dominant limb, was detected among the different jump tests.
The second part of this project started with Study 3, the objectives of which were to quantify inter-limb asymmetries in different skills (unilateral jump, COD, and COD with iso-inertial resistance) and to analyse the relationships between these asymmetries and physical performance tests in young tennis players. The results showed different magnitudes of asymmetry among the tests, the largest of which was in the UCMJ. The tests with iso-inertial resistance, which enable the COD with overload action to be reproduced, gave greater asymmetries than those detected in the COD test. Last, large asymmetries in COD were associated with reduced performance in the UCMJ and COD tests.
This part of the project continued with Study 4, which incorporated an analysis of the COD at different angles (90º - 180º) among young handball player subjects. The results showed different magnitudes of asymmetry among tests, with the largest measures of asymmetry found in the variables of the COD deficit (CODD) at 90º and the COD with iso-inertial resistance tests. Large asymmetries in the crossover step (CRO) with iso-inertial resistance were associated with reduced performance in the CODS and the sprint tests.
Last, the objective of Study 5 was to assess the effects of an 8-week resistance training programme based on change of direction exercises using different technologies: an iso-inertial resistance training device and a cable-resistance device, recording possible variations in performance and magnitudes of inter-limb asymmetries in young handball players. Both interventions showed improvements in the different physical variables, the jump, the change of direction, the linear sprint, and the throw, although the iso-inertial programme with resistance had a greater effect on performance of the UCMJ, the unilateral jump (UBJ), COD180, V-CUT, repetition of change of direction (RCOD) and the throw (TH), and caused a greater reduction in inter-limb asymmetry values in the UCMJ. Differences between the two groups in favour of the iso-inertial training group were found in the UCMJ, RCOD and TH tests, and greater inter-limb reductions were shown in the unilateral lateral jump (ULJ) and the RCOD.
In conclusion, the asymmetries detected in the different multi-directional sports vary in magnitude depending on the test selected. Furthermore, in the individual analysis of the different tests administered, it was observed that athlete’s lower limb preferences depended on the test. Greater asymmetries were detected in the vertical jump test, the CODD variable, and the change of direction with inertial resistance test in multidirectional sports. The change of direction with inertial resistance test also enabled us to detect asymmetries in actions that approximate the actual sport. Moreover, the results showed that asymmetries have a negative impact on performance of the jump and the change of direction, and on speed in the linear sprint and the capacity to repeat the change of direction.
Last, we were able to observe that iso-inertial training results in greater adaptations in performance and larger reductions in asymmetries than conventional cable-resistance training. We can also affirm that positive adaptations in performance caused by resistance training are not necessarily associated with reduced asymmetries.
