Stretch Reflex in the Squat

First, a quick primer on the stretch reflex. The stretch reflex is an involuntary reaction of a muscle, once stretched, to automatically try and contract. You can use this reflex to strengthen your lifts.
In the squat it creates a rebound off the bottom of the squat, helps you change direction to get upward momentum started.
Since it is an involuntary action of the muscle, it’s not necessarily something you can force to happen. There are, however, things you can do to maximize its affect:
1. Keep your upper body rigid. A rigid upper body transfers the power of this rebound directly to the bar, driving it upward. A soft torso absorbs some of this energy reducing its impact on your lift. I break upper body tightness down into two components – a) Thoracic tightness is created when you tighten your upper back by squeezing your shoulder blades down, hard b) Lumbar tightness is created by strong bracing and a strong core (with or without a belt).

2. Maintain your body position at the bottom of the squat. The most common error I see here is allowing the hips and knees to shift forward at the rebound point; this shift allows the hamstrings too loosen up, and reduces the rebound effect. A cue I like to use is to spread the floor before you start each rep, and to push out throughout each rep; drive your knees out so they don’t shift forward
3. Maintain your back angle at the bottom of the squat – don’t allow your hips to shift up or back ahead of the bar. Allowing this uses up your rebound without driving the bar upward.
4. Finally, maintain a good bar path. Make sure you keep the bar moving straight down and back up directly over the center of your feet.
In case it hasn’t become obvious, the best way to create maximum rebound leveraging the stretch reflex…is to use good squat technique.