An isometric contraction is when there is no discernible (or very little) change in the length of the muscle fibres during a movement. There are three primary reasons we ask you to perform isometric contractions during your class and believe it or not, it isn’t just to hurt you:
#1: Maximum intramuscular tension (the most strength your muscle will exert) is attained for only a brief period in a dynamic movement such as a lunge. In an isometric contraction you can sustain that maximal tension for a longer period of time.
For example, instead of maintaining maximum intramuscular tension for 0.25 to 0.5 seconds in the concentric portion (standing phase) of a lunge, you can sustain it for around six to twelve seconds during an isometric hold at the bottom of the lunge, more if we count slowly. Strength is greatly influenced by the total time under maximal tension. This is the reason we preach slow, controlled tempo throughout your classes e.g. when performing crunches. If you can add 10 to 20 seconds (or more) of isometric tension per class, then we increase your potential for strength gains. More strength means you can train longer and harder creating a leaner and better conditioned physique.
#2: Isometric contractions can help you improve strength at a precise point in the range of motion (ROM) of an exercise. You may find you struggle to lunge deeply and slowly without losing your balance or retaining precise technique. If we break the lunge down into the sum of its parts by asking you to hold the bottom position of the lunge we can break through plateaus and move past sticking points.
#3: Isometric contractions are not ‘energy expensive’, meaning that you don’t expend much energy by while performing an isometric hold. This allows us to reap the benefits of isometric training without compromising the rest of the movements in your class.