Category Archives: Myology

Isometric vs Isotonic

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File:Medicine Ball Plank.jpg


It’s not enough for massage students to learn about the different muscle names, locations, attachments, and actions.  You also need to learn how a muscle contracts and the different types of contractions.  Sure you love muscles when you get to school, but by the end you feel like you’re choking on all the information being shoved into you.

Different types of muscle contractions used to not be a big deal if you didn’t understand, but lately many students have mentioned getting some questions involving eccentric muscle contractions on their licensure exams.  You have to understand this material now.  First we’re going to talk about the big categories.  There are two types of muscle contractions you need to know about.  Isometric and isotonic.

Isometric contractions are when your muscles are contracting, but they’re not changing length.  Another way to look at it is your muscle works (contracts) but the angle of the joint doesn’t change.  For example above is a picture of a man doing planks.  These are advanced planks, but nonetheless he is holding the position without moving.  This is an isometric contraction.  This can be done with weights also.  If you lift a weight and then hold it a specific joint angle without moving you’ll be doing an isometric contraction.



If instead in the above picture he wasn’t holding the weight there, but was curling the dumbbells up and down this would be an isotonic muscle contraction.  In an isotonic muscle contractions there are two phases: concentric- when the muscles shorten, and eccentric- when the muscles lengthen.  For example if we think about the biceps brachii during curls when the dumbbell goes up the biceps is shortening, concentric, and when the dumbbell lowers the biceps is lengthening, eccentric.  The important point is that both parts are contractions.  Just because the muscle lengthens doesn’t mean you stopped contracting and it is a stretch.  In the gym these two parts are referred to as positive reps, the concentric contraction, and negative reps, the eccentric contraction.  The eccentric contractions are theorized to rip off more myosin heads and leads to better gains, but more soreness.

So, now you have a basic understanding.  All of the muscle actions/functions you learn in school are concentric contractions.  It wouldn’t be decent of us to make you learn both for each muscle.  You already have an overwhelming amount of material to learn.  Yet, both are a part of the way you move everyday.  Anytime you start a movement, speed up, or do something explosive then you are doing a concentric muscle contraction.  Whenever you try to slow down a movement, or lower with control you’re doing an eccentric muscle contraction.  The eccentric contractions are the opposite action than the concentric.  For example imagine you dropped your phone on the floor.  You bend over to pick it up.  This would be flexion of your vertebrae.  You learn in school that rectus abdominis flexes your vertebrae.  However, gravity is already helping you to the ground.  If you concentrically contract your rectus abdominis then your face would smash into the ground.  If you decide to prove me wrong please record and send the video.  Instead you lower yourself slowly and under control.  You’re using erector spinae to control your movement down.  Erector spinae is contracting to slow you down from hitting the ground, but it’s lengthening.  This is an eccentric contraction even though you learn that erectors extend vertebrae.  Another example would be when you step off a curb, or land after a jump.  You don’t land with your knees locked out.  You flex your knees to absorb the shock.  Even though the quadriceps are knee extensors, they are going to eccentrically contract during knee flexion to slow you down.  If you used hamstrings you would collapse onto the ground.

Just to mention there is one more type.  Isokinetic contractions are contractions where you use a piece of equipment, that no matter how hard you push, makes sure you concentrically contract at the same speed through the range of motion.  Massage licensure exams don’t ask about this type of contraction.

To recap during isometric contractions your muscles don’t change length and your joint stays at the same angle.  You’re holding a position.  During isotonic contractions you are actually moving and the muscle can shorten or lengthen.  Concentric contractions are when muscles shorten and these are the actions you learn when you cover muscles in school.  Eccentric contractions are when the muscle lengthens and these are used when you are slowing down or controlling yourself.