Understanding the terminology
First, (and to make matters a bit more complicated), the term contraction, when used along side the word muscle, as in muscle contraction, is generally understood by most as a shortening or reduction in the muscles’ length – and this is the dictionary definition. However in the athletic fitness world, this definition doesn’t take into account the dynamic nature of a muscle to work while being forced in the opposite direction, as in muscle lengthening, nor does it take into account a muscles dynamic ability to work while remaining in a fixed position.
So while the words muscle contraction have taken on a broader meaning in the athletic fitness world, the actual definition of the word contraction, as defined in the dictionary, is a bit of a misnomer when talking about the different types of muscle “contractions”.
What are the 3 types of muscles contractions?
So, the term tension, rather than contraction, is better suited to define the actions (dare I say, contractions!) of a muscle.
Therefore, muscles, under tension, may
- Lengthen, or
- Remain the same length.
And it is these three different types of muscular tensions that are used to define the three different types of muscular “contractions”. The three different types of muscular contractions, therefore, are:
- Concentric contractions (shorten),
- Eccentric contractions (lengthen)
- Isometric contractions (remain the same).
A concentric contraction is a type of muscle contraction where the length of the muscles shorten while undergoing tension.
For example, when you pick up a curl bar and perform a biceps curl, the length of your biceps muscles shorten. Your hands start down by your sides, and ends with your hands up by your shoulders. The biceps muscles shorten during this motion.
Another example would be if you were to perform a couple of leg curls on a hamstring machine. As your knee is flexing, your foot is approaching your buttocks, and your hamstring muscles shorten in the process.
Any muscle activity where the strength of the muscle can overcome the resistance of an object forcing the muscle’s length to shorten, is considered a concentric contraction.
Therefore, most of the exercises that you would typically do at a gym by using the various machines and/or dumbbells, etc. involve concentric contractions.
An eccentric contraction is a type of muscle contraction where the length of the muscle elongates, or lengthens, while undergoing tension.
This can occur in two different ways:
a) Voluntarily Contractions, and
b) Involuntarily Contractions
a) Voluntary eccentric contractions: Let’s use the same example above for the biceps curl. After you have completed the first part of the biceps curl, where your elbows are flexed, and your hands are holding on to the curl bar up by your shoulders, it is now time to return the weight back down towards your waistline. Typically this is done in a smooth and controlled motion where the muscle, in this case the biceps, acts to decelerate the elbow joint at the end of the movement.
The same muscle that started this motion, the biceps, is now undergoing tension in the opposite direction. It is now lengthening as it returns the weight back down towards your waist. This is an example of a voluntary eccentric contraction.
Another similar example involves the hamstring muscles. Like the example above involving leg curls, as you return the weight back to its starting point, the knee joint extends slowly with the aid of the hamstrings. These muscles undergo tension, but now in the opposite direction, where they are lengthening. This is another example of a voluntary eccentric contraction.
b) Involuntary eccentric contractions: Involuntary eccentric contractions occur when the weight or resistance you are attempting to move or lift is too heavy or strong for the muscle to accommodate. The main difference between this, and the voluntary eccentric contractions, is the lack of control over the weight/resistance during an involuntary eccentric contraction.
We can use a similar example for involuntary eccentric contractions as we did for the voluntary eccentric contractions.
Using the biceps curl exercise, let’s say that you have both of your elbows flexed, with your hands up by your shoulders, and someone hands you a 100 lb barbell. The average person who had been handed this weight, (if they don’t just drop it) would immediately have their biceps muscles lengthened, even if they tried to prevent it by tensing them. This would be an example an involuntary eccentric contraction.
It should be noted that muscles subjected to heavy involuntary eccentric loading beyond your control can suffer potentially greater damage when overloaded as compared to concentric (muscle shortening) and/or voluntary eccentric loading.
Now, voluntary eccentric contractions are just as much a part of weight training as are concentric contractions. A concentric contraction is typically associated with the exercise itself, as in biceps curls, triceps push downs etc. But, concentric contractions only account for half of the repetition of that particular exercise. (ex. Biceps curl – the muscle shortens under tension while the elbow is flexing). The other half, the returning of the weight to the starting position, is controlled through voluntary eccentric contractions. (ex. Biceps curl – the muscle lengthens under tension while the elbow is extending)
Many times, however, exercises are purposely designed around a slow return of the weight back to its starting position only. This is what is termed as negatives with respect to weight training. And it is a known fact that muscles are typically stronger during voluntary eccentric movement (muscle lengthen) when compared to a concentric movement (muscle shortening). To understand why this is, just think that it is much easier to set a 100 lb package to the ground than it is to raise one up off the ground.
Weight training therefore, involves concentric muscle movements, voluntary eccentric muscle movements, and occasionally, involuntary eccentric movements.
An isometric contraction is a type of muscle contraction where the length of the muscle doesn’t change while undergoing tension . An example of this would be if you were to take a 20 pound weight and perform a biceps curl and hold a position halfway between the repetition for 10 seconds. The length of your biceps muscle doesn’t change during this time, however a force is still being applied.
Another example would be if you were to push against a wall for 10 seconds. The wall doesn’t move and neither does the length of the muscles in your arms pushing against it. Again, a force is still being applied.