The Swing is the Thing:The Biomechanics of a Softball Swing

Task 10: BiomechanicsNational Coaching Institute

Scott Searle

Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

Describe the Movement:Prepatory Phase

Stance:Start standing upright in an athletic stance with your feet 2 shoulder widths apart. Your knees should be slightly bent and turned slightly inwards as though holding a basketball between them. 1Both feet should face the plate and your toes should line up and be on the same plane. You should hold the bat loosely in your fingers lining up your proximal interphalangeal joints (between first and second digit). Both of your thumbs should wraparound your bat gently. You must not have any tension in your hands. To get your bat position, rest your bat on your shoulder as if it is an axe and raise it to a 30-60 degree angle. The bottom of the bat should be at the top of your strike zone (armpits). Your elbow should make a “v” pattern and your rear (right) elbow, should be slightly higher then your front. If yourest the bat in the nook of your elbows, the bat should be pointed at the pitcher on a slight downward angle.

Your head should be facing the pitcher, and be able to see the pitcher with both of your eyes. Your head should be level and eyebrows should be parallel to the ground. Ensure you are completely balanced, and have flexibility in your knees. A good

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

way to test this is to jump as high as you can and try to land softly. You must also have total plate coverage, so extend your bat to ensure you can reach the outside corner of the plate. You must keep your muscles loose and relaxed.

Execution Phase-Force Producing Movements

Preliminary Movement: (Load)As in all sport movements, you must go backwards before you go forwards. Shift your weight to your back foot and lift your front feel off the ground. As your weight shifts, slide your foot across the ground until it reaches your belly button. Throughout this movement, your back knee must stay in front of your back foot. During all of this movement in your lower body, keep your hands still, although a slight shoulder turn is acceptable.

Slide your front foot back across the ground towards the pitcher and land on your tip toe in the same place it started. After yourtoe-touch, your hips should slide forward in a sideways manner. Your hips lead your hands and you are creating most of your forcewith the bottom of your body. Your back foot should be driving forward as if pushing off a 2X4 lying on the ground, then pivots to show your shoelaces to the pitcher.

Execution Phase-Critical Instant

While all of this is happening, your hands should be moving toward the ball. You must keep your hands inside the flight of the ball, and drag your left thumb across your chest as if

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

throwing a Frisbee. The barrel or top of the bat should always be above your hands, and your hands should always be in front of your body.

When you hit the ball, your arms should be slightly flexed and your bat will be level to the ground. This “level swing” occurs only for a moment as you push through the ball While you are making contact, you should be hitting “into” a firmfront side.

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

Follow-Through Phase

Once the ball has left your bat, you should extend your arms in the direction the ball is travelling. Your hands should finish high, and land between your shoulder blade and ear. Your hips should continue to rotate and yourright hip should end up parallel toyour left as your bellybutton faces the pitcher.

What is being moved?Force is being produced to accelerate the bat forward in a kinematic sequence to propel the ball.

What is the velocity profile?

The entire swing should take between 2 and 3 seconds. The swing begins before the pitcher releases the ball and ends after the

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

ball leaves the bat. Assuming the pitcher throws 62 MPH the pitch will take approximately 0.3-0.5 seconds to reach the plate.The movement used to create force begins with a circular motion in the hands.2

What is the acceleration?

Acceleration is defined as the rate of change of velocity overtime.

The acceleration of the bat is defined as bat speed and caused bytwo main forces. 1) Rotational movement of trunk and circular movement of the hands. 3 2) Torque created by push/pull of the hands in addition to force created by hands. Torque is enhanced by increasing the distance from the athlete’s hands to the end ofthe bat as revealed in the chart and images below.4

2 Interview with Dale Aiken3 Adair, Robert. The Physics of Baseball. New York: HarperCollins, 1991.

4 http://www.batspeed.com/research10.html6 | P a g e

Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

   

   

Inches from end of bat Speed of Bat

0 74.5 mph

1 72.9 mph

2 71.3 mph

3 69.8 mph

4 68.2 mph

5 66.6 mph

6 65.0 mph

7 63.4 mph

8 61.8 mph

9 60.2 mph

10 58.7 mph

11 57.1 mph

12 55.5 mph

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

13 53.9 mph

14 52.3 mph

15 50.7 mph

16 49.1 mph

     

MPH change for every inch 1.6 mph

How long does the movement take?

The movement, including the load and follow-through, takes between 2.5 and 3 seconds to complete. The hitter must begin thismovement before the pitcher releases the ball. A hitter must be prepared to stall her swing in the prepatory or load phase if thepitch is a changeup. A good changeup is 10 MPH slower, then a drop or rise ball and will force the hitter to maintain her load for an extra 0.2 seconds.

What is the relationship to force?

Energy is transferred from the body, to the bat, to the ball. Large muscle groups generate force that is continued by smaller muscles before being transferred to the bat. The ball remains onthe bat for 2/1000s of a second and some energy is lost in the transfer.

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

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What is the impulse?

When the bat collides with the ball, the impulse experienced by an object equals the change in momentum of the object.

Which muscle fibres are used to generate this force?

Hitting uses Type IIb white (fast glycolytic) muscles to generateforce. This utilizes the anaerobic metabolism which creates quickness and powerful bursts of speed or force. This fibre has the highest rate of contraction of contraction and a faster rate of fatigue. In warm-up or batting practice an athlete should be given an opportunity to rest between swings to avoid fatigue.

Prepatory Phase

5 Adair, Robert. The Physics of Baseball. New York: HarperCollins, 1991.

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

Weight shift and plantarflexion of your lead foot pushing back create weight transfer to back foot. There should be no upper-body movement. Athletes often perceive a movement of their hands in this phase, but it is driven by lower body movement and does not create force.

Execution Phase-Force Producing MovementsSlight lateral slide of lead foot to start position, this slide should be no longer then 4-6 inches. Force is produced through trunk rotation caused by exertion abdominal muscles and contraction of back muscles. Rotate hips to 45 degree angle untilbat contacts ball

Execution Phase-Critical InstantAt critical instant hips are at a 45 degree angle to the front ofthe plate. Torque is created through a “palm up-palm down” hand position at contact. The hitters top hand should push and bottom hand should pull using extensors and flexors of the forearm to create maximum torque. Throughout this movement body weight shifts forward on to front foot. At critical instant, weight is shared between both feet, but is being shifted toward front foot as back is being raised into plantarflexion.

Follow-Through PhaseHips should be at 180 degree angle to front of plate facing the pitcher. Weight has shifted to front foot, but front shoulder must stay behind your knee.

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Biomechanics of a Softball SwingNational Coaching Institute

Scott Searle

Is there a stretch shortening aspect to the movement that requires the use of elastic tissue?

At critical instant arms are in full extension (muscle lengthen),and muscles use elastic tissue to shorten during follow-through. Back muscles are also shortened as the abdominal muscles lengthenat the critical instant.

To create most force, muscles must lengthen and shorten. However, in other softball movements, such as bunt or slap muscles are not shortened. Moreover, an athlete may decide not tolengthen her muscles to increase bat control.

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