Use external cues (target, ground) for faster results
External focus means directing attention to something beyond your body, such as a spot on the ground or the target you are aiming at. The instructor says there is a lot of research that external cues work better and produce faster results, while internal cues (focusing on a body part) take longer to show they are working because they are essentially a dual task. He adds that internal cues can still be effective but take longer to confirm they are working.
Channel: Mark Immelman
Watch official source at 24:29