触球时的伸展
Also known as: 完全伸展, 驱动穿过球
触球时的伸展，是指在挥棒中双臂在触球区几乎达到完全伸展长度的那个点，把动力链中的最大能量传递给球。
正确的伸展意味着双手和棒头正在驱动穿过球，而不是在触球那一刻停下来。完全的伸展能产生更高的击球初速和更真实的飞行轨迹。那些过早塌陷——在完全穿过触球区之前就把手臂收回来——的打者，会产生软弱、擦边的击球。伸展对外角球的触球尤为关键，因为球是在触球区更深处被接触的，手臂必须完全伸展才能从正确的角度传递力量。
Think of hitting through two imaginary balls positioned 6 inches apart. This means the first is where you make contact and the second is where your hands are driving through. This means keeping extension alive through both contact points.
Film your swing from the side and measure the angle between your forearms at the contact frame. This means optimal extension shows roughly 150–170 degrees, with full lockout (180 degrees) indicating over-extension and significant fold indicating early deceleration.
Example
打者在触球时双臂完全伸展、驱动穿过外角球，把球打成一记强劲的平飞球，飞向反方向的空档。
How it shows up on video
At the contact frame the arms should appear near-fully extended with a slight bend remaining in the lead elbow. This means fully locked-out arms can indicate over-extension that collapses the swing before follow-through. The bat head should be ahead of the hands at contact on all middle-to-outside pitches, confirming full extension reached the ball rather than stopping at impact. Hitters who decelerate through contact will show the elbows folding back before the ball leaves the bat.
Common mistakes
- Collapsing the lead arm at contact — pulling the elbow back before the ball leaves the bat — which kills exit velocity mid-swing
- Over-extending by fully locking both elbows at contact, which reduces bat speed and produces a casting motion rather than a whipping extension
- Confusing extension through the ball with follow-through — extension is at and just after contact, not the circular finish of the swing
- On inside pitches, reaching for full extension when the contact point requires the arms to be shorter and the barrel to be more pulled through the zone
In SwingVantage Motion Lab
Motion Lab measures arm extension angle at contact and tracks the rate of arm acceleration and deceleration through the contact zone, identifying whether the hitter drives through the ball or decelerates at impact.
Frequently asked questions
完全伸展真的能增加击球初速吗？
能——完全伸展在触球时最大化了手臂杠杆的长度，相比短促、塌陷的手臂位置，能把更多来自身体旋转的动能传递给球。
内角球和外角球的伸展有什么不同？
内角球需要在完全伸展之前就完成触球，因为触球点在身体前方靠前——触球时伸展几乎已经完成；外角球则需要双臂在触球时达到完全伸展，因为球在好球带内更深的位置。
Related terms
Related guides & benchmarks
Put this into your swing
SwingVantage can spot this in your own swing — free to start.
See a sample Fast-Pitch Softball report first