[ca] La velocitat de colpeig és un factor determinant del rendiment en tots els grups d'edat i tant al tennis masculí com femení. Sembla clar que la capacitat d'aplicar velocitat a la bola és de naturalesa multifactorial i que el resultat és la conseqüència de la suma dels aspectes tècnics, les característiques antropomètriques, el rang de moviment i els nivells de força. No obstant això, hi ha un cert interès per definir aquells aspectes físics que condicionen la velocitat en els diferents cops, a més d'examinar les possibles diferències entre jugadors de diferents edats i nivells. Conjuntament, la manera com aquestes variables es veuen afectades per la competició sembla essencial per enfocar l'entrenament i les estratègies de recuperació. Aquesta tesi té com a objectiu establir aquelles variables de força i potència determinants per a la velocitat de colpeig. A més, oferir informació sobre noves variables que també poden ser rellevants per a la producció de velocitat i com es poden entrenar amb noves metodologies d'entrenament. Per acabar, també s'examinarà com aquests aspectes determinants es veuen afectats per la fatiga induïda per la competició. Per això, es van dur a terme vuit estudis. Els resultats mostren que la força dinàmica màxima no sembla correlacionar-se positivament amb la velocitat de colpeig. D'altra banda, les variables isomètriques derivades de la corba força-temps semblen ser rellevants per fer cops més ràpids. Això indica la importància de la capacitat d'un jugador de produir alts nivells de força en curts períodes de temps en múltiples posicions articulars presents al moviment esportiu. A més, sembla que certes propietats contràctils poden ser rellevants per a la producció de velocitat, encara que un major o menor nivell d'aquesta variable pot tenir un efecte positiu o negatiu depenent del grup muscular analitzat. Finalment, partits simulats d'uns 80 minuts semblen ser una càrrega física insuficient per provocar canvis en els factors determinants, cosa que indica que els jugadors joves poden necessitar més volums de joc o competicions repetides per afectar negativament aquestes variables.

[en] Several physical abilities are considered as determinant performance factors that can differentiate the level and success of a tennis player. Alongside technical proficiency, tactical awareness and certain psychological traits, some physical capacities stand out as essential for improved performance. Among these aspects, stroke velocity seems highly relevant in all age groups and in both male and female participants. The ability to apply speed to the ball, especially in the serve, seems to give the player the capacity to dominate the point and therefore a higher advantage during match-play. Previous literature has intended to establish the main physical traits that differentiate faster and slower strokes. It seems clear that these actions are of a multifactorial nature and that the outcome is the consequence of the summation of technical aspects, the anthropometric characteristics of the player, range of motion values and strength and power levels. Nevertheless, there is a certain interest in defining those physical aspects that determine velocity production in the various tennis strokes, alongside examining the possible differences between players of different ages and levels. Added, how these variables are affected by tennis competition seems essential towards training approaches and effective recovery strategies. This thesis aims at establishing those strength and power variables determinant for stroke velocity. Also, it intends to offer insights on novel measurements that may also be relevant contributors to velocity production and how these may be stimulated by new training methodologies. Last, how these determinant aspects are affected by fatigue induced by match-play will also be examined. Towards these goals, eight studies were carried out. Studies 1 and 2 correlated strength and power measurements to stroke velocity. Studies 3, 4 and 5 examined match-induced changes in the relevant variables. Study 6 approached a novel training method towards velocity enhancement and studies 7 and 8 were reviews of the literature. Results of this research show that maximal dynamic strength does not seem to positively correlate to stroke velocity in young participants. On the other hand, isometric force-time curve variables such as the rate of force development and impulse in specific joint positions of the kinetic chain seem to be relevant to perform faster strokes in these populations. This indicates the importance of a player's capacity to produce high levels of strength in short periods of time in multiple joint positions present in the motion. Because of this, training approaches that perform fast movements with light weights may be a valid option towards stroke velocity increases, although further research is needed to establish specific load prescriptions and injury risk. Also, contractile properties seem in some way relevant for velocity production, although an increased or decreased level of this variable may have a different effect on velocity production depending on the muscle group analysed. Last, single bouts of simulated match-play seem an insufficient load to elicit changes in determinant factors of stroke velocity, indicating that young players may need greater playing volumes or repetitive events to negatively affect these key variables.