Biomechanics and Kinetics of Elbow Position in the Baseball Swing By: Samantha Erosa

Overview Objective: Analyze two different swings: ‘regular’ elbow versus ‘chicken wing’ elbow Disclaimer: My natural swing utilizes the ‘regular’ elbow position. Which position produces the best results? Analysis from three positions: Elbow Bat ball Elbow measured from highest position (after loading phase). Equipment: Sanyo High Speed Camera (240 frames/second) Easton Softball Bat [33 inches(.838 m), 23 oz (.652 kg)] 11 inch softball [6.0oz (.17 kg)]

Phases of the Swing Stance Phase Feet and hand position vary. Balanced and weight evenly distributed. Personal preference. 2. Loading Phase Backward movement of shoulders and arms Backward rotation of the spine Beginning of the timing step. The cocking of the hips. Cocking of the wrists 3. Launching Phase Continuation of timing step. Opening of the hips. Forward rotation of spine. Pushing and pulling action of the arms and shoulders. Guiding action of the hands on the bat. 4. Follow-Through After contact Hips open completely toward pitcher. Stiff front leg Full Arm extension

Muscles Involved 2. Loading Phase 4. Follow-Through Elbow extensors Pectoralis major muscle, trapezius muscle, supraspinatus, and middle deltoid muscles. Lateral spine rotators Big muscles on thigh and buttocks. External hip rotators. Flexor carpi radialis, flexor carpi ulnaris 3. Launching Phase External/internal hip rotators. Pelvis muscles, forearm muscles Quadriceps Abdomen Lateral spine rotators Bicep/Tricep 4. Follow-Through Elbow extensors Forearm pronates Forearm supinates Stance Phase Preparation of muscle usage.

Significance of the Elbow Common advice: “Keep your back elbow up!” Elbow down: direction of force for the top hand is directed toward the pitcher. Driving of the top hand puts the elbow directly in the ‘slot’ and results in a good driving position. Like throwing a punch. Elbow up: more elevated position to snap the bat head further back during the loading phase. Goal is to achieve maximum torque during launching phase. Greater source of error: causes hitters to drop their back shoulder instead of getting into a good driving position. Results in an ‘upper cut’ or ‘loopy’ swing. At contact, the hitter ideally wants the elbow as close to the body as possible. This position of the elbow allows for concentration of force and energy needed for ‘explosion’ of the swing. Lose massive amounts of energy and power with elbow away from the body. With elbow far from the body, the hitter loses energy which translates into weaker contact with the ball.

Elbow Positions Regular Elbow Position Chicken Wing Elbow Position Calculated Angle: sin-1 (.1739/.3164) = 33.34° Calculated Angle: sin-1 (.3582/.8248) =25.74°

Regular Elbow position

Elbow Velocity

Elbow Acceleration

Bat Velocity

Bat Acceleration

Ball Velocity Blurry ball

Ball Acceleration At contact

Calculations: Regular Elbow Max velocity: 5.91 m/s Max acceleration: 66.638 m/s2 Bat- .838 m & .652 kg : Max velocity: 22.181 m/s KE= ½ mv2 = ½ (.652 kg)(22.181 m/s2)2 = 160.39 J ρ= mv = (.652 kg)(22.181 m/s)= 14.46 kg*m/s Max acceleration: 161.171 m/s2 F= ma= (.652 kg)(161.171 m/s2)= 105.08 N Ball- .17 kg : Max velocity: 28.257 m/s KE= ½ mv2 = ½ (.17 kg)(28.257 m/s)2 =67.87 J ρ= mv = (.17 kg)(28.257 m/s)= 4.8 kg*m/s Max acceleration: 415.051 m/s2 F= ma = (.17 kg)(415.051 m/s2)= 70.56 N

Calculations: At Contact Elbow: velocity: 3.045 m/s acceleration: 21.520 m/s2 Bat- .838 m & .652 kg : velocity: 18.842 m/s KE= ½ mv2 = ½ (.652 kg)(18.842 m/s2)2 = 115.74 J ρ= mv = (.652 kg)(18.842 m/s)= 12.28 kg*m/s acceleration: 133.874 m/s2 F= ma= (.652 kg)(133.874 m/s2)= 87.29 N Ball- .17 kg : velocity: 17.055 m/s KE= ½ mv2 = ½ (.17 kg)(17.055 m/s)2 =24.72 J ρ= mv = (.17 kg)(17.055 m/s)= 2.9 kg*m/s acceleration: 415.051 m/s2 F= ma = (.17 kg)(415.051 m/s2)= 70.56 N

Chicken Wing Elbow

Elbow Velocity

Elbow Acceleration

Bat Velocity

Bat Acceleration

Ball Velocity

Ball Acceleration At contact

Calculations: Chicken Wing Elbow Max velocity: 7.097 m/s Max acceleration: 48.203 m/s2 Bat- .838 m & .652 kg : Max velocity: 23.081 m/s KE= ½ mv2 = ½ (.652 kg)(23.081 m/s2)2 = 173.67 J ρ= mv = (.652 kg)(23.081 m/s)= 15.05 kg*m/s Max acceleration: 204.055 m/s2 F= ma= (.652 kg)(204.055 m/s2)= 133.04 N Ball- .17 kg : Max velocity: 22.643 m/s KE= ½ mv2 = ½ (.17 kg)(22.643 m/s)2 =43.58 J ρ= mv = (.17 kg)(22.643 m/s)= 3.85 kg*m/s Max acceleration: 364.526 m/s2 F= ma = (.17 kg)(364.526 m/s2)= 61.97 N

Calculations: At Contact Elbow: velocity: 3.642 m/s acceleration: 13.740m/s2 Bat- .838 m & .652 kg : velocity: 19.678 m/s KE= ½ mv2 = ½ (.652 kg)(19.678 m/s2)2 = 126.23 J ρ= mv = (.652 kg)(19.678 m/s)= 12.83 kg*m/s acceleration: 162.120 m/s2 F= ma= (.652 kg)(162.120 m/s2)= 105.70 N Ball- .17 kg : velocity: 11.061 m/s KE= ½ mv2 = ½ (.17 kg)(11.061 m/s)2 =10.40 J ρ= mv = (.17 kg)(11.061 m/s)= 1.88 kg*m/s acceleration: 330.899 m/s2 F= ma = (.17 kg)(330.899 m/s2)= 56.25 N

Comparison of Calculations ‘Regular’ Elbow Position Elbow: max velocity: 5.91 m/s max acceleration: 66.638 m/s2 ‘Chicken Wing’ Elbow Position Elbow: max velocity: 7.097 m/s max acceleration: 48.203 m/s2 Bat: max velocity: 22.181 m/s max acceleration: 161.171 m/s2 KE= 160.39 J F= 105.08 N ρ= 14.46 kg*m/s Bat: max velocity: 23.081 m/s max acceleration: 204.055 m/s2 KE= 173.67 J F= 133.04 N ρ= 15.05 kg*m/s Ball: max velocity: 28.257 m/s max acceleration: 415.051 m/s2 KE= 67.87 J F= 70.56 N ρ= 4.8 kg*m/s Ball: max velocity: 22.643 m/s max acceleration: 364.526 m/s2 KE= 43.58 J F= 61.97 N ρ= 3.85 kg*m/s ***These quantities for elbow and bat position are reflective of the ideal contact location. It is at this position that the most force and energy transfer to the ball will occur.

Comparison of Calculations- At Contact ‘Regular’ Elbow Position Elbow: velocity: 3.045 m/s acceleration: 21.520 m/s2 ‘Chicken Wing’ Elbow Position Elbow: velocity: 3.642 m/s acceleration: 13.740 m/s2 Bat: velocity: 19.678 m/s acceleration: 162.120 m/s2 KE= 126.23 J F= 105.70 N ρ= 12.83 kg*m/s Bat: velocity: 18.842 m/s acceleration: 133.874 m/s2 KE= 115.74 J F= 87.29 N ρ= 12.281 kg*m/s Ball: velocity: 11.061 m/s acceleration: 330.899 m/s2 KE= 10.40 J F= 56.25N ρ= 1.88 kg*m/s Ball: velocity: 17.055 m/s acceleration: 415.051 m/s2 KE= 24.72 J F= 70.56 N ρ= 2.9 kg*m/s As expected for the ‘chicken wing’ elbow, more force and energy is generated just before contact in comparison to the ‘regular’ elbow swing. However, due to the ‘upper cut’ less force and energy was transferred to the ball.

Does Chicken Wing Provide Extra Torque?

Regular Elbow Position

Chicken Wing Elbow

Torque: Pre-Contact Assume that the force on the bat is perpendicular to the shoulder pivot point. Center of mass of bat is roughly around 22 in (.588 m) Regular Elbow Position: Force=F= 87.29 N Lever arm=r= .4841 m Ƭ= r*F= (87.29 N)*(.4841)= 42.26 N*m Chicken Wing Elbow Position: Force=F= 105.70 N Lever arm=r= .4451 m Ƭ= r*F= (105.70 N)*(.4451)= 47.05 N*m

Which hit would go farther Which hit would go farther? (Hypothetically- constant acceleration, no wind resistance, ideal projectile motion ) Regular Elbow Position Chicken Wing Elbow Position Projected Angle: Sin-1 (.3377/1.912) = 10.17° -velocity: 17.055 m/s vfy = viy + ay *t= 0=17.055*sin(10.17)- 9.8*t t =.307 so, 2*t =.614 xf = vix *t= 17.055*cos(10.17)*.614= 10.31 m =33.8 ft -Driving position enabled solid contact- line drive. Projected Angle: sin-1 (.6005/1.899) = 18.43° velocity: 11.061 m/s vfy = viy+ ay*t=0=11.061*sin(18.43)-9.8*t t =.357 so, 2*t = .714 xf= vix*t=11.061*cos(18.43)*.714= 7.49 m =24.6 ft -Dropped shoulder resulting in poor contact- pop up.

Conclusions The ‘chicken wing’ elbow position does in fact generate more force and kinetic energy. This position also creates more torque. However, this position results in a ‘loopy’ and ‘upper cutting’ bat path that makes contact less direct. More likely to hit a pop up. The ‘regular’ elbow position generates less force and kinetic energy but due to the driving bat path, is able to make solid contact with the ball and result in more energy transfer than the ‘chicken wing’ swing. More likely to hit line drives. Further investigations: Study torque more closely. Difficult to view the motion with the limited perspective of the camera. Also, Logger Pro doesn’t have capabilities to determine exact angles or angular motion. Also will be interesting to analyze the lower body. Project was limited to the effects of the upper body in the swing but the energy originates from the lower half and is transferred into the upper body.

Tips for Hitting Keep the elbow below the shoulder position. Provides greater driving mechanism as opposed to ‘upper cutting’ the ball and hitting a pop up. Let the ball get deep for maximum energy transfer and force application. Keep elbow as close to the body as possible. If not, you will lose critical energy during the pivot portion of the swing which results in less torque.

References Van Such, Larry. "Developing Bat Speed and Power in the Baseball Swing: How To Swing The Bat For More Speed and Power." Athletic Quickness. Web. 14 Apr. 2012. <http://www.athleticquickness.com/bat_speed_power_baseballswi ng_4.asp>. Mankin, Jack. "BatSpeed.com_Baseball and Softball Swing Hitting Mechanics." Bat Speed. Web. 14 Apr. 2012. <http://www.batspeed.com/tf09.html>.