Isometric vs isotonic contraction

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Kevin Mangelschots

Before we get into the argument between isometric vs isotonic contraction to figure out which one is better, let us take a look at the different types of muscle contractions.

They both sound very much alike, but there are a couple of key differences between these two forms of muscle contraction.

What is an isotonic muscle contraction?

An isotonic contraction can be defined as the shortening or lengthening of a muscle against a constant tonus/load. In other words, the length of the muscle changes, but the load remains the same.

An isotonic, also called dynamic stretching routine will fit perfectly as a warm-up.

Two different types of isotonic contractions can be distinguished based on the above definition, namely the concentric muscle contraction and the eccentric muscle contraction.

Illustration describing the difference between a concentric and an eccentric muscle contraction.

  • Concentric contraction

    A concentric contraction means the muscle contracts and shortens during exercise against a constant load. This is one of the most popular and well-known forms of weight training. Weightlifting is mostly based on this principle.

    For example, the concentric part of the bench press means the upward movement of the barbell contracts and shortens the chest and triceps muscles.

  • Eccentric contraction

    An eccentric contraction means the muscle contracts and lengthens during exercise against a constant load. This is one of the most popular forms of weight training. Again, weightlifting is based on this principle.

    For example, lowering the bar during the bench press contracts and lengthens the chest and triceps muscles.

What is an isometric muscle contraction?

Illustration describing what an isometric muscle contraction is.

An isometric contraction means that the muscle length or joint angle doesn’t change during muscle tension. In other words, the involved body parts during the exercise remain at the same length/static.

Examples of isometric exercises also called static exercises are planking, holding a squat at a 90° angle, or bridging and maintaining that position.

An isometric, also called a static exercise stretching program is a great way to cool down. Isometric stretches are best performed after working out.

Isotonic vs. isometric contraction: Differences and advantages

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Isotonic muscle contraction

  • More blood is pumped into the muscles, increasing muscular endurance
  • More variety in workouts
  • Fewer repetitions are needed to increase strength and muscle mass
  • You build strength in the full range of motion (ROM)
  • Easy to exercise all muscle groups
  • Improves bone density

Isometric muscle contraction

  • Can get to, and maintain maximum muscle contraction
  • Improves bone density
  • Improves cholesterol levels
  • Improves digestion
  • Good for rehabilitation and recovery
  • Maintain muscle mass and strength

As we can see, each form of muscular contraction has its benefits. Thus, combining them to get the best results makes the most sense.

Examples of an isotonic contraction

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These are some examples of an isotonic contraction:

  • Bench pressing
  • Squatting
  • Deadlifting
  • Lunges
  • Burpees
  • Walking
  • Running
  • Swimming
  • Straight leg kicks to stretch

Isometric muscle contraction examples

  • Planking
  • Squatting until parallel and maintaining that position
  • Holding two dumbbells beside your body at shoulder height
  • Getting into a stretching position and maintaining constant muscular tension

Isotonic stretching vs. isometric stretching routine

Picture of a woman stretching in front of a field of grass.


Isotonic stretching

It’s possible to perform an isotonic stretching also called a dynamic stretching routine.

Examples of isotonic stretching are:

  • The walking knee-to-chest exercise
  • Straight leg kick
  • Side shuffles
  • Arm circles
  • Jumping jacks

A dynamic stretching routine is better suited as a warm-up or cool-down rather than with the single purpose of increasing your range of mobility.

Isometric stretching

Another form of stretching is called isometric stretching, also commonly called a static stretching routine.

Examples of isometric stretching exercises are:

  • Standing hamstrings stretch
  • Planking
  • Seated butterfly stretch
  • Cobra pose
  • Calf stretch
  • Upper backstretch

Isometric stretching is best performed after working out to cool down or to increase the range of motion.

Performing static stretching exercises right before working out will hurt your athletic performance due to reducing strength and increasing the risk of acquiring injuries in the process.

If you are hellbent on performing a static stretching routine before a workout, then it is recommended to do so at least one hour before working out.

Which one delivers the most benefits?

Image of the word, “conclusions” written on a black backboard with white chalk.
 

In my opinion, isotonic training generally gives the most benefits regarding daily functioning.

We often require isotonic movements during our daily lives like for example walking or picking something up from the ground.

Examples of good, functional isotonic exercises are squats and deadlifts. Mainly because those are movements that we naturally perform during the day.

Isometric exercises can also have an important place in your workouts to improve your daily functioning. Especially the core muscles, which main function is stabilizing your core and spine for a long period of time.

With all that being said and done, I believe a combination of both isotonic and isometric training is best for optimal results.

I would spend most of my time training performing isotonic strength exercises and do some isometric exercises on the side as assistance work. Just because your main focus lies on isotonic work doesn’t mean you have to exclude isometric work entirely.