In the 1960s, East German scientists and coaches developed a training technique of performing a heavy strength exercise, such as squats, followed immediately by a power – or ballistic – exercise, such as squat jumps or hurdle hops. A recent study from New Zealand reinforced the validity of that long-held technique.
Study results showed that performing box squats (3 sets of 3 reps, three minutes rest between sets) followed by jump squats (3×3, three minutes rest) caused greater increases in salivary testosterone and cortisol than performing strength or power exercises alone. Performing strength exercises followed by power exercises might maximize muscular adaptations to training.
Source: Journal Strength Conditioning Research, 25: 1072-1078, 2011