by HAC Personal Trainer Rachel Evans
All human movement is produced via muscle contractions. When you’re in the gym making fitness gains, you’re doing so by making purposeful muscle contractions via the kinds of exercise you choose.
So, what is a muscle contraction? It is the process of lengthening or shortening a muscle to produce force or create movement. When we exercise, we make purposeful muscle contractions to become stronger, fitter, healthier, etc. These contractions occur in three phases, and we’re able to identify those phases in most exercises.
Types of Muscles
SKELETAL MUSCLES
Location / Purpose: Part of the musculoskeletal system. These are the muscles that you use to move your body. These muscles attach to your bones via tendons and ligaments and use the bones as a lever system to create movement.
Type of Muscle Contraction: Mostly voluntary, can be involuntary.
SMOOTH MUSCLES
Location / Purpose: Smooth muscle lines your internal organs. Example: the lining in your intestines that move your food through your GI tract.
Type of Muscle Contraction: Involuntary. These contractions occur subconsciously. You wouldn’t want to have to consciously think about breathing or moving your food through your GI tract, etc.
CARDIAC MUSCLES
Location / Purpose: Heart tissue.
Type of Muscle Contraction: Involuntary. Like smooth muscle, cardiac muscle does its thing without you having to consciously decide to make your heart pump.
Phases of Muscle Contractions
ISOMETRIC
What does it mean? Muscle length does not change. You hold the muscle at a set length, building strength needed to perform that specific posture.
Example / Importance: Holding a static muscle contraction. You can find this phase between eccentric and concentric phases. You can prolong this phase by holding a certain position during an exercise, such as holding a plank or staying at the bottom of a squat.
ECCENTRIC
What does it mean? Muscle lengthens. The “lowering” phase. Muscle does negative work.
Example / Importance: This is the phase of a muscle contraction where greater force is created. It occurs after the isometric phase. This is when work is done. The muscle will experience micro-tears as it stretches under tension ultimately leading to strength gains with proper recovery.
CONCENTRIC
What does it mean? Muscle shortens; the “lifting” phase. Muscle does positive work.
Example / Importance: This phase is when your muscle shortens and moves an object. The force needed to move is less than your muscle’s max.
How is this knowledge applied to exercise?
Here are some generic examples:
A: Isometric phase: Squeezing your glutes and holding at the top of the thrust in bridge position. Knees are at 90°, heels are planted on the ground, and hips are raised.
B: Eccentric: Lowering the weight toward the ground, lowering your hips down.
C: Concentric: Raising the weight to the top position of hip thrust, pushing through your planted heels, and squeezing your glutes to lift body weight off of the ground.
A: Isometric phase: Holding the weight in that extended position overhead, keeping triceps squeezed.
B: Eccentric: Lowering weight back behind head, elbows bent.
C: Concentric: Squeezing triceps to lift weight straight above head, keeping elbows tucked close to the sides of head.
A: Isometric phase: Any point in which you hold the same position. Most people hold at 90°.
B: Eccentric: Lowering the weight down.
C: Concentric: Curling the weight up.
Isometric phase: N/A
Eccentric: Walking down the stairs.
Concentric: Walking up the stairs.
Bonus: If you’ve ever had to climb sets of stairs for an extended amount of time, and you notice being sore the next day – that soreness is from walking DOWN the stairs, even though walking up feels harder
effort-wise.
Isometric phase: Planks are an isometric exercise. You hold the same position the whole time, trying to maintain a muscle contraction at the same length the whole time.
Eccentric: N/A
Concentric: N/A
Fitness Challenge time! Try to think about which muscles feel like
they are shortening or lengthening during your next workout. Try
an isometric hold of some sort! Slow down each exercise and really
make that mind-muscle connection.
