Power generated by a topspin vs. a slice Ali Kazmi April 30, 2012

Breaking Down a Shot Every human motion is driven by the synergistic action of the basic biomechanical unit. The basic biomechanical unit consists of a pair of mutually antagonistic muscles that produce a common muscular torque in the same joint In tennis, the most obvious example is the biceps-triceps pair (pictured) from Ivancevic et al. (2008) An example of the basic mechanical unit

Breaking Down a Shot The three components of the kinetic chain (nervous, muscular, and skeletal systems) all work together to produce movement.

Preparation or “Loading” Breaking Down a Shot The standard forehand has two main phases: (i) preparation or “loading,” and (ii) hitting the ball. Preparation or “Loading” Includes two simultaneous actions: stepping into the right position with the left leg forward (if right-handed) and lifting the racquet above the shoulders Muscles involved: right deltoideus and biceps Hitting the Ball Includes three main movements: Right hip rotation towards the ball with feet still on the ground (muscles involved: right gluteus maximus and medius muscles) Arm swing of the racquet (Muscles involved: right pectoralis major, deltoideus, and biceps) To create topsin, a slight twist of the wrist to brush over the ball (muscles involved: right palmar flexors) Not pictured: gluteus maximus

Breaking Down a Shot The topspin is a forehand shot generated hitting the ball with an up-and-forward force that causes the ball to drop. What is “Topspin”? “Topspin” refers to the property of a ball that rotates as if rolling in the same direction as its velocity. Topspin inflicts a downward force that causes the ball to drop due to its interaction with the air (called the Magnus effect Use in Tennis Topspin provides the player an increased margin of error because the ball hits the ground quicker, and so can rise higher above the net The racquet should face below the direction the ball is moving, and brush up against the back of the ball

Breaking Down a Shot The splice is a forehand shot that utilizes “backspin” to cause an upward force that lifts the ball. What is “Backspin”? “Backspin” refers to the property of a ball that rotates as if rolling in a direction opposite to its velocity An upward force is applied to the ball that lifts the ball (also due to the Magnus effect) Use in Tennis A splice is useful for defensive shots because the ball takes a longer time to reach the opponent, giving the player more time Backspin shots also tend to bounce lower when the reach the opposite court.

Power Generation in a Topspin Stroke Power Analysis Power Generation in a Topspin Stroke Instantaneous Power = Change in Energy Initial Kinetic Energy m= 0.057kg X-velocity= 0.937m/s Y-velocity = 0.912m/s Overall velocity= 1.31m/s g=10m/s2 h= 0.9213m KE= ½*m*v2 =0.050J PE= mgh= 0.53 Total Energy= 0.58 Final Kinetic Energy m= 0.057kg X-velocity= 28.973m/s Y-velocity = 2.517m/s Overall velocity= 29.08m/s g=10m/s2 h= .9213m KE= ½*m*v2= 24.1J PE=mgh= 0.53J Total Energy= 24.6J Power Generated= 24.02W

Power Generation in a Slice Power Analysis Power Generation in a Slice Instantaneous Power = Change in Energy Initial Kinetic Energy m= 0.057kg X-velocity= 0.863m/s Y-velocity = 0.814m/s Overall velocity= 1.19m/s g=10m/s2 h= 1.051m KE= ½*m*v2 =0.040J PE= mgh= 0.60J Total Energy= 0.64J Final Kinetic Energy m= 0.057kg X-velocity= 24.096m/s Y-velocity = 2.170m/s Overall velocity= 24.2m/s g=10m/s2 h= 1.051m KE= ½*m*v2= 16.7J PE=mgh= 0.60J Total Energy= 17.3J Power Generated= 16.66W

Future Directions Further detailed analysis of impact rotation kinetic energy changes Energy transfer measurements Strategic considerations Impact of elasticity of strings of racquet Frequency of usage of different types of shots and success/failure ratios

References Elliott, B. "Biomechanics and Tennis." British Journal of Sports Medicine 40.5 (2006): 392-96. Print. Ivancevic, T. “Biomechanical Analysis of Shots and Ball Motion in Tennis and the Analogy with Handball Throws.” Physical Education and Sport 6.1 (2008): 51-66. Print