Wednesday, 3 June 2020

When opposites contract - muscle partners

For every movement your body makes, a combination of muscle contractions occur. For each of these contractions there is a relaxation in the opposite muscle. Welcome to the world of muscle pairs.

Virtually all muscles have an opposite. When a muscle is contracting it is known as the agonist. When it contracts, it causes its opposite muscle, the antagonist, to relax. For example if you flex your biceps, its opposite the triceps relaxes. If you flex your triceps the biceps relaxes. This is something called reciprocal inhibition

Agonist and antagonist muscle pairings
The basics of agonist/antagonist muscle action. Picture from DifferenceBetween.com

So why should you care about this? Read on...

Table of contents

Supersets and alt-sets

Knowing your prime antagonist helps in the creation of effective supersetting or alt-setting if you goals are not hypertrophy or endurance. Supersetting is were you perform two exercises back to back. If you are seeking hypertrophy or looking to exhaust a particular muscle, then agonist supersets such as bench press followed by chest flyes, is the way to go. Alt-setting is where you are doing two exercises alternatingly, not necessarly as a supeset, but as a way to save time.

If you are not going for bodybuilding or the like, then agonist-antagonist supersetting or alt-setting provides the benefit of the second exercise (focusing on the antagonist muscle to the first exercise) causing reciprocal inhibition, meaning your prime agonist muscle from the first exercise relaxes and stretches, helping improve its recovery between sets.

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Stretching

Antagonist-stretching is an effective form of muscle stretching whether it is done actively or passively.

An example of actively stretching your hamstrings is by raising your knee up and extending your leg at the knee. This contracts your quadriceps causing your hamstrings to relax and stretch. This kind of active movement is believed to be better for increasing range of motion and flexibility in the stretched muscle.

You could also do this passively, by flexing the antagonist muscle if possible whilst stretching.

Clenching your quadriceps whilst stretching your hamstrings, can allow you to go deeper into the stretch. Picture from Sports Injury Clinic

Interestingly you can mix it up with a form of strectching that seems contrary to the point of reciprocal inhibition. It is antagonist static stretching. An example is if you are doing biceps curls, then you would stretch your triceps between sets. Research shows that this form of stretch can cause an increase of repetitions and agonist activiation during the exercise.

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Split routines

Knowing your muscle pairs helps in the devising of more effective split routines. If you train chest and triceps primarily on what you might call a "push" day, then the next session you train upper back and biceps on a "pull" day. This allows you to avoid overloading the previously worked out muscles whilst given them a stretch through reciprocal inhibition.

Devise more effective and efficient split routines. Picture from The Fitness Bible

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Muscle pairs

It can be quite confusing matching up each specific muscle to its opposite especially when certain actions call different muscles or parts of a muscle into action or relaxation. Thus I'll try to keep this as simple as possible by basing it on the primary motions, common exercises for those motions and the primary muscles. Keeping it simple also helps for devising agonist-antagonist muscle pairings for supersets or split sessions amongst other things.


Action

Exercises

Agonist

Antagonist

Spinal flexion

Sit-ups, hollow holds

Rectus abdominus

Erector spinae

Spinal extension

Back extensions, good mornings

Erector spinae

Rectus abdominus

Horizontal flexion

Press-ups, bench-press

Pectoralis major

Rhomboids, trapezius (mid)

Horizontal extension

Cable rows, seated rows

Rhomboids, trapezius (mid)

Pectoralis major

Elbow flexion

Bicep curls, chin-ups

Biceps

Triceps

Elbow extension

Dips, triceps extensions

Triceps

Biceps

Shoulder flexion

Pull-ups, pull-downs

Latissimus dorsi

Deltoids

Shoulder extension

Shoulder press

Deltoids

Latissimus dorsi

Knee flexion

Hamstring curls

Hamstrings

Quadriceps

Knee extension

Leg extensions

Quadriceps

Hamstrings

Hip flexion

Bent-knee leg raise, hanging-knee raise

Iliopsoas

Gluteus maximus

Hip extension

Hip thrusters

Gluteus maximus

Iliopsoas

Ankle flexion
(Dorsiflexion)

Banded foot pulls

Tibialis-anterior

Gastrocnemius, soleus

Ankle extension
(Plantar flexion)

Calf-raises

Gastrocnemius, soleus

Tibialis-anterior

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Lombard's paradox

Now whilst we know how muscles are meant to work and the effect they have on their opposite muscle, there is a interesting circumstance known as Lombard's paradox where this goes out the window. Lombard's paradox is where both the agonist and antagonist activate at the same time, this is commonly seen when standing up from a seated or squatting position.

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Recap

Knowing the antagonist muscle to that which you are working out allows you to fine tune your training in various ways. Whether it be more effective alternating sets, stretches, or split routines. Whilst the musculoskeletal system is highly complex and there are a multitude of different muscles and muscle heads activating in any given movement, each with their own antagonist, exercises can be broken down into their prime agonist and the primary antagonist.

If you have any questions then feel free to ask away in the comments or send me some feedback!

Lyle Richardson,
Gym Pal - Unlock Your Potential

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