Depending on the stance, the body segments position and their coordination, body weight distribution can be used in different ways when creating a stroke. Stance types are defined as square, semi-open, and open stance.
Direction of the stroke is related to the timing and angle of the impact point. The unwritten rule is that the ball will be following the direction to which strings of the racquet are directed to at the point when racquet intercepts the ball. Usually, in order to perform at their best, the players change timing of torso rotation to the ball while changing direction of the stroke.
Trunk rotation highly influences the pace of the stroke demanding that the player maintains dynamic balance when accelerating using the full potential of energy stored in the muscle. In the cases of the high time and space constraints, the players do not have enough time to fully rotate the shoulders as they have to keep the dynamic balance during the stroke choosing to keep the stability of the body movement for the sake of keeping ball in play. Therefore, when performing the down the line stroke, the strings should be aligned with the baseline in front of the body, pointing to the direction straight. Cross court strokes demands earlier or later (inside out forehand) contact point, in front or sideways from the hitter’s body.
The intention of creating different shot direction has been shown to influence the way the trunk rotations are used. High-performance (ATP ranked) players are creating greater hip alignment rotations when playing down the line strokes and generating smaller separation angles of shoulders compared to hips when playing balls straight compared to cross court. The hitting stance can drastically influence the trunk rotation and kinetic chain utilization efficiency. Square stance compared to the open stance create higher trunk angular velocities enabling elbow joint pronation after the impact creating significant differences in shoulder internal rotation and wrist flexion peak torque values.
It is very important to mention that direction of the stroke can be altered by the changes in degree of the shoulder internal rotation just before the contact.
Square stance as attacking stance
By having a base of support in line with the target, player can generate much more of linear momentum as the front foot provides stability for pivoting around it. This stance is the most suitable for movement forward as the front foot provide perfect stability for the body weight transfer forwards making it easier and more efficient to employ more of the linear then angular momentum having racquet path more consistent. Sstroke production using the square compared to the open stance creates significantly higher values of the peak shoulder internal rotation nd larger wrist flexion torques, the crucial features of stroke acceleration. Players chose this stance as more solid when choosing direction of the stroke, as shown that high performance junior players chose significantly more often to position themselves in the closed stance when choosing to direct their strokes down the line.
Semi open stance as universal stance
By positioning with the semi open stance, the player can create a good push off the back foot creating strong linear momentum. Players can still use the full potential of the angular momentum especially when hitting the ball cross court, enabling more freedom of movement the joints used at the stroke production. By being in a semi open stance, player’s rear hip can be pushed through and around the pivoting front foot creating the racquet head orientation towards the ball with the cross court angle in a more natural way. Planting the rear foot behind the front foot enables the creation of the linear momentum with the support from the leg drive. In addition, in a case of the semi open stance the leg drive is enabling the larger angular range of movement through the ball. The reason why experts use mostly this type of stance is that provides possibilities of creating optimal combination of linear and angular momentum while being timely prepared at the same time. In addition to the stroke efficiency, it’s easier to manipulate the body segment coordination and disguise the stroke intention for this stance which has been proven as the tactical pattern in creating advantage during the expert’s match.
Open stance as an emergency stance
Having an open stance, the player relies more on the body angular rotation. To ensure the efficient and long range of motion forwards, the shoulder separation angle compared to the hips has to be larger, relying on the elastic capabilities of the upper back muscles due to lacking of the leg drive support. This stance makes the racquet path less consistent then a more closed stance but allows more rapid rotational momentum and faster response. Players can chose this stance for few reasons as it demands less preparation and recovery time and by relying on the angular momentum with the abbreviated backswing, players can create timely and efficient response when in urgency due to the spatio-temporal constraints of the game context.
CONCLUSION
Slower muscles groups with larger mass (legs and trunk), contribute largely to the linear momentum as the leg drive being a primary source of transferring the energy to the hips moving forward. With the notion that larger muscles groups provide larger contribution in creating forward momentum, observer’s perception of the hitter’s ability of creating an efficient leg drive, can provide important information in predicting the intention of the stroke. Trunk rotation can provide very useful information about the ball direction and pace depending on the angle of loading external rotations. The researches had shown that the stroke production using the square compared to the open stance creates significantly higher values of arm internal rotation and torques., contributing to the very offensive and penetrating abilities of the ball.
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