Muscle – Its Elastic Tissue

Muscle is elastic tissue. When you lower the weight on the bench press, your chest stretches. This stretch is immediately followed by a recoil effect that helps you shorten your chest muscles again [1]. It’s basically like how a rubber band works. After you stretch the band, it shoots back to return to its normal position.
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As you can imagine, this “stretch reflex” contributes to your strength performance quite a bit. The reason we don’t want to do much static stretching right before training is that these static stretches impairs the stretch reflex. When you perform static stretches that last 30+ seconds, you hold your muscles at a lengthened position and these muscles stay lengthened for several hours. As a result, the stretch reflex of your muscles is less powerful and your strength performance decreases [2].
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Dynamic stretches, on the other hand, may enhance the stretch reflex [3]. Since you go through dynamic stretches forcefully like you would when performing strength exercises, a dynamic stretch generally is more effective in preparing you for strength training than static stretching. After the workout, then you can look into doing static stretches if improving long-term range of motion is your goal. For more details and example mobility routines, visit the link in my bio!
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References:
1. https://www.researchgate.net/publication/232163543_The_Stretch-Shortening_Cycle_Proposed_Mechanisms_and_Methods_for_Enhancement
2. https://www.ncbi.nlm.nih.gov/pubmed/21659901
3. https://www.ncbi.nlm.nih.gov/pubmed/155740981d