John Kennedy emphasizes the importance of dynamic warmups as opposed to traditional static stretching, particularly before engaging in any strenuous physical activity. Dynamic warmups not only prepare the body physically, but also wake up the brain, readying it for the challenge to come. Static stretching, on the other hand, is more suited for the cool-down phase post-exercise, as pre-workout static stretching has been shown to reduce your ability to generate maximum force.
  

Key Points: 

1. Dynamic warmups are superior to static stretching before exercise, increasing the body’s awareness of its spatial positioning and movement, thus readying it for physical activity.
2. Different types of exercise require different warmup routines, suggesting that the exercises should tie directly into the type of workout you’re planning.
3. Exercises like bodyweight squats, walking lunges, and “toy soldiers” can serve as general-purpose dynamic warmups, but you can also focus on specific areas like the feet and ankles, hips, and thoracic spine for a more specialized warmup.
4. Warming up is not something to rush through. It aims to increase blood flow to muscles, raise core temperature, and get the body used to unusual positions. Focusing on skill and form can help make the movements become ingrained.
5. Post-exercise, static stretching can be beneficial as it returns the muscles and tendons to their normal resting length.

Source: https://www.popsci.com/story/diy/dynamic-warmup-why-how/