Top performers like jiu-jitsu champion Marcelo Garcia avoid staying in a state of moderate, constant stress (a 'simmering six' out of ten). Instead, they master dropping to zero (deep rest) and exploding to ten (full engagement) only when needed, conserving energy and preventing burnout.

The 'burpee' was invented by physiologist Royal Burpee in 1939 as a simple, four-count test to assess physical fitness. Its efficiency led the U.S. military to adopt it for evaluating the fitness of recruits for World War II, revealing its origin as a diagnostic tool.

A coach's criticism about athletes training barefoot—a threat to a shoe company—sparked an "aha moment." Instead of dismissing it, Nike innovated by creating a shoe that replicated the benefits of barefoot running, thereby capturing the user's intent and creating a new product category.

Reframe a new goal to align with a person's existing identity and skills. Neuroscientist Emily Falk was convinced to take up running when her brother framed it as a task for academics, who excel at planning and long-term work. This shifted the activity from a foreign physical challenge to something that leveraged her pre-existing strengths, making it more appealing.

The choice between simulation and real-world data depends on a task's core difficulty. For locomotion, complex reactive behavior is harder to capture than simple ground physics, favoring simulation. For manipulation, complex object physics are harder to simulate than simple grasping behaviors, favoring real-world data.

The body restricts movement into ranges where it is weak to protect itself from injury. By actively training for strength at the full extent of your motion (e.g., full-depth squats), you signal to your nervous system that the range is safe, which in turn increases your functional flexibility.

Training methods leverage the brain's predictive nature. Repetitive practice makes the brain efficient at predicting movements, leading to mastery and lower energy use ('muscle memory'). In contrast, unpredictable training creates constant prediction errors, forcing adaptation and burning more calories, which drives growth and resilience.

Elevating the heels reduces the ankle mobility required for a deep squat. Holding a weight out front acts as a counterbalance, allowing the user to sit back into the squat, reducing direct pressure on the knees and making the full range of motion more accessible and pain-free.

Unlike barbell squats where lower back rounding ('butt wink') is a common risk, the front-foot-elevated split squat makes this dangerous movement much harder to perform. It promotes deep knee flexion and single-leg strength, building mobility and stability with a significantly lower risk of spinal injury.