The Biomechanics of Dunking a Basketball Thomas DiSanto Dr. Rome Bio 438

History 1891 1936 1949 Dr. James Naismith invents basketball. Joe Fortenberry becomes the first person to dunk. The NBA is established.

Muscles involved in Jumping

Average Vertical Jump The average Division 1 basketball player jumps between 27 and 30 inches.

Objectives Examine the pros and cons of the two most fundamental dunks 1. Dunking with one hand while jumping off one foot 2. Dunking with one hand while jumping off two feet Do the different takeoffs have in-game effects? Hypothesis: The one-foot approach allows a player to dunk the ball faster while sacrificing some vertical height. The two- feet approach takes longer but allows a player to achieve a greater vertical leap.

Terrence Ross

LeBron James

Methods Filmed using the Sony Cybershot RX10 II at 480 frames/second Analysis of: 1. Vertical hip displacement from standing hip height of 42.4 in 2. Total time 3. Leg angle between hip, knee, and ankle 4. Power produced

dunk off one foot

Results

Dunk off 2 feet

Results takeoff

Results One Foot Two Feet Total Time (sec) 0.46 0.54 Max Hip Height (in) 75.46 76.00 Standing Hip Height (in) 42.4 Vertical (in) 33.06 33.60 Dunking off two feet took an additional 0.08 seconds but provided a higher vertical jump of 0.54 inches.

Explanation A good jump approach involves blocking horizontal momentum and converting it into vertical momentum. The horizontal momentum generated in the steps prior to takeoff is blocked when the feet are planted. For an efficient conversion of momentum, the center of gravity (hips) must be kept low, and one’s chest should be lowered toward the knees.

Results

Results

Explanation Hand size Holding the ball with 2 hands while preparing to jump with 2 feet allows slight use of the arms. Using your arms during a jump increases the velocity of the center of mass during takeoff. Energy that is built up in the arms is transferred to other parts of the body.

Explanation Power calculation Power was calculated by finding the difference in potential energy (= m*g*h) between the highest and lowest points of each jump. This difference was divided by time to obtain average power in Watts. Average power off 1 foot = 7,871 W Average power off 2 feet = 13,709 W Jumping with two feet caused a 74% increase in power, allowing for a higher jump.

Conclusions The results obtained support the hypothesis that dunking off two feet is a longer approach but allows for a greater vertical jump. In basketball, players must be able to jump off both one and two feet as each has its own specific in-game situations. Going forward, this knowledge gives players incredibly useful information that will help maximize their performance.

Future Directions Simulate the dunks by jumping on force plates Analyze force generation over time throughout the takeoff Add markers to the arms Analyze arm velocity to gain a better understanding of their ability to transfer energy to the other parts of the body

Acknowledgements Dr. Rome Dr. Nelson