Physical fitness, motivation and tactical dexterity are important aspects to get a good performance in tennis, but the mechanical efficiency of the players’ strokes often determines the level of success both recreationally and competitively (Roetert et al, 1992). Although the forehand, compared to the backhand, allows for generating more speed which has an effect on the ball and its accuracy after impact, this is also a basic groundstroke and is becoming increasingly important in modern tennis (Delgado-García et al., 2019; Fernandez-Fernandez et al., 2010; Reid, 2001). A player’s decision to use two-handed backhand (DH) or one-handed backhand (SH) is a key point in the tennis learning process, since the player will be able to obtain a major or minor biomechanical efficiency in this stroke depending on his decision (Genevois et al., 2015). For example, DH is the type of backhand that most of the baseline players usually choose, while the versatile players seem more likely to choose SH because it is easier for them making net approach strokes and backhands volleys (Genevois et al., 2015). Young tennis players prefer DH during their initiation phase since it requires less force than SH (Giangarra et al., 1993). Another factor that favors the selection of DH over SH in adult beginner players is that SH is more susceptible to tennis elbow (Giangarra et al., 1993; Roetert et al., 1995; Blackwell & Cole, 1994).
There is a need to carry out research that analyses the kinematics of the backhand since it is less studied than forehand or serve (Genevois et al., 2015; Bahamonde, 2005), the backhand is one of the two basic groundstrokes in tennis and the evolution of the backhand represents one of the biggest changes in tennis over the past decades (Genevois et al., 2015). The segments used for performing both backhands (DH and SH) are the same: hips, shoulder, upper arm and hand/racket rotation (Reid & Elliott, 2002). However, 3D photogrammetry research indicates biomechanical differences between DH and SH (Genevois et al., 2015; Giangarra et al., 1993; Akutagawa & Kojima, 2005). These studies show a sequential coordination between the different segments involved in performing the two backhands (Allen et al., 2016). It has been shown that intersegmentary coordination (IC) occurs from proximal to distal in terms of angular velocity and linear velocity (Marshall & Elliot, 2000) and that the moment of maximum trunk rotation acquires a fundamental character in the performance that we can achieve in this stroke (Genevois et al., 2015).
The biomechanical parameters of tennis strokes have been widely studied in laboratory conditions, but there is a shortage of studies that do it on the court (Allen et al., 2016). Only some biomechanical studies make of use inertial sensors in tennis (Cosac & Ionescu, 2015; Sharma et al, 2017), however after reviewing the literature, in most cases the devices are placed on the racket or forearm, and tennis performance is the result of sequenced whole body coordination (Allen et al., 2016). It will be vital also to analyze the trunk, arms and head to have a more complete monitoring of the kinematics of the stroke (Bertolotti et al., 2015).
Previous studies have shown that inertial measurement unit (IMU) gyroscopes are a valid alternative to 3D optical motion capture system for angular kinematics analysis in tennis (Delgado-García et al., 2021) since they allow capturing the rotational movements in the three axes of space; record the peak angular speeds (ωpeak) of the different segments and differentiating between different levels of play (Ahmadi et al., 2010). They also allow to discriminate the different phases of the strokes (Hansen et al., 2017; Büthe et al., 2016) and obtain the sequencing of the segments that are part of the kinematics of the stroke (Büthe et al., 2016).
The main objective of this article is to compare angular kinematics and intersegmental coordination of the upper limbs between two-handed and one-hand backhands in a sample of competition players by using gyroscopes. Additionally, this study compares ball speeds and accuracy obtained in both types of backhand. We hypothesise that there will be significant differences in terms of ωpeak and intersegmental coordination in some of the segments measured between DH and SH by using gyroscopes, but the opposite will happen in the variables speed ball and accuracy.
Limitations
Five-marker model has been the most used with 3D photogrammetric systems to analyse biomechanical differences between DH and SH (Reid, 2001; Bahamonde, 2005; Reid & Elliott, 2002). In contrast, in our study with inertial sensors, four sensors have been used since the legs sensors were suppressed in order to capture only the kinematics differences of the upper body (Ahmadi et al., 2010). The results of the present study should be interpreted with caution because of possible errors when performing analysis of human movements (Akutagawa & Kojima, 2005). Placed instruments may also contain a source of error due to skin movement (Manal et al., 2003). Another limitation of the study was the number of participants used and their play level (intermediate). In future studies, the sample will be significantly increased and only competitive tennis players will be measured. In addition, it might be interesting for future studies to determine the maximum speed without to obtain a reference value. It could be that and athlete increases their accuracy at the expense of speed.