You need to warmup before every workout to prevent injury and activate your muscles. Andrew takes about 10 minutes and does his proper workout in around 50 minutes. This is the optimal time for hormone secretion.

For resistance training: do 5 minutes of low-intensity cardio and pyramid up the weights for 2-3 sets. Examples:

Exercise Sets x reps Notes
Low intensity cardio 5-10 min Increase your heart rate
Leg swings 2 x 15
Cable extensions 2 x 15

For cardio: do 5-10 minutes of low-intensity and some muscle activation exercises.

Example