In the study, researchers examined three different methods of strength-training: dynamic external resistance, isokinetic resistance, and isometric resistance. In addition, frequency, intensity, and volume of workouts were also analysed to evaluate their effect on muscle growth.
In dynamic exernal resistance, the weight is raised and lowered as in most traditional approaches. In isokinetic resistance, muscles are contracted and shortened at a constant speed. With isometric resistance, muscles are contracted but not shortened, meaning there is no movement.
Public opinion in the last 10 years has generally been that isokinetic and isometric training are better than external resistance for inducing hypertrophy, because of the kind of stress those methods place on the muscles.
However, the analysis of all available research on these three training methods showed that there was not enough evidence to conclude that any of the three methods is significantly better than the others, as long as there is sufficient intensity, frequency, and volume of the workouts.
However, there may be a better method for particular individuals, based on current fitness level, fitness goals, available time to work out, and personal preferences. Talk to your personal trainer to decide on the best method or methods for your particular needs.