Analysis of Knee Joint Motion in Tennis Flat Serve Using Low-Cost Technological Approach

Abstract

Tennis serve is a closed-skill motion influenced by the kinematic chain concept. An important role on the final performance is surely linked to the knee joint motion, although only few studies addressed lower-limb influence. In this work we propose a study about the proprioceptive angle size of knee joint in the first flat serve produced by tennis players of different performance levels. Twelve subjects involved in the study are divided in three groups using the ITN classification code: beginner, intermediate and advanced players. A simple biomechanical model of lower limb was proposed to study the knee joint motion. Three flat serves were recorded using three synchronized cams. A specific algorithm was developed to obtain the maximum flexion value of front knee using coordinates of lower-limb joints. Speed of impact (S B ) and height of impact (H B )were also evaluated to compare results with previous works and to assess the tennis players' performance. Results showed a statistical meaningful difference among three groups in all performance indexes. Moreover a strong correlation was found among knee motion and S B and H B .

The Effects of Knee Flexion on Tennis Serve Performance of Intermediate Level Tennis Players

“…By including only intermediate-level tennis players, we limited the tennis level's influence on serve performance. Indeed, players of different levels could show distinct performances regardless of their knee flexion during the serve [6]. Participants and their legal guardians signed an informed consent form.…”

“…A faster serve reduces the time for the opponent to respond and may hamper the return. Another parameter used to measure tennis serve performance is the racket impact height [6][7][8].…”

“…The upper limb's angular motion is well known as a major contributor to serve speed [10,11]. However, the influence of the lower limb's angular motion is still controversial and limited to adult tennis players [5][6][7]12]. More studies are necessary to address the effects of lower limb motion on serve performance, especially in young tennis players.…”

“…Greater knee flexion during the serve preparation phase allows reaching greater knee extension velocity (since acceleration is applied during a longer period), producing a more effective lower limb drive as more mechanical energy is added to the body. However, studies that investigated the impact of knee flexion on serve performance found inconsistent results [5,6]. Sgro et al [6] found that advanced tennis players had greater knee flexion during the preparation phase, greater serve speed, and greater racket impact height than beginners.…”

“…However, studies that investigated the impact of knee flexion on serve performance found inconsistent results [5,6]. Sgro et al [6] found that advanced tennis players had greater knee flexion during the preparation phase, greater serve speed, and greater racket impact height than beginners. Moreover, they found Sensors 2021, 21, 5254 2 of 10 a positive association of maximum knee flexion with serve speed and racket impact height.…”