When discussing the role the lower body has in the baseball swing, the front leg often gets the majority of the focus. Most hitters initiate the swing with a stride - which is essential for a hitters timing and weight distribution. After all, it's pretty difficult to hit a baseball without balance and timing. However, the back leg also plays an instrumental part in a hitter's swing.
As a batter stands in the box in anticipation of a pitch, their back foot should be following the same rules as the rest of their body - be comfortable, relaxed and consistent. Hitting can be a very stressful activity, it's important for an athlete to stay loose to get the most out of their abilities.
Consistency is important because in the heat of competition a ballplayer may let nerves get the best of them and abandon their mechanics. A player who practices with consistency will be more confident and comfortable in a game situation.
At the moment the pitcher releases the ball and the hitter begins the recognition process, the brain should already be communicating with lower body in anticipation of the pitch type, speed and location. The role the back foot plays in this segment of the swing is essential. The shoelaces of the back foot should be aimed in the direction of the batter's desired hit location, whether that be to the a hitter's pull side, up the middle or the opposite field. This accounts for a major part of a hitter's precision and their ability to swing a bat accurately.
Another key component of the back foot in a baseball swing is it's essential in the weight distribution process. As a hitter's back foot takes aim at it's target, the weight distribution process is simultaneously taking place. During this time a players hips should begin to rotate and the bat should be in orbit through the strike zone and toward the baseball.
At the point of contact a hitter's front leg should be straight, while the back leg should be in a bent and flexed position. This is the ideal posture for a hitter looking to drive the ball with maximum force.
Some hitters, including the legendary Babe Ruth and modern day slugger Bryce Harper, can actually be seen lifting their back foot off the ground at the point of contact. This is a result of the amount of force being created during the weight distribution process.
By perfecting this technique a batter will have the ability to distribute their weight properly and stay behind the ball for a longer period of time, which will result in the player hitting the ball with more precision and power.