Weak Muscles Lead To Bad Posture. So Why Doesn’t A Gym Workout Help?

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Weak muscles lead to bad posture. So why doesn’t a gym workout help? If you have chronic back or neck problems, you almost certainly have bad posture, though it may not be certain which came first. Nevertheless, you will often hear (or get) advice that you need to strengthen your postural muscle and correct your posture.

And after months of hard work at the gym with weights and cable machines, you feel slightly better but you still slouch now and then. Why didn’t it work fully for perfect posture ALL the time?

Muscles Types

The reason gym workouts fail to completely correct and support your posture all the time, is that it simply did not target all the relevant muscles – the stability muscles. And it was the wrong type of training for some of the muscles – gym works targets the power muscles. And muscles exercises alone isn’t enough – postural awareness is also required.

What Are The Different Types Of Muscles, And Why Do The Differences Matter?

We tend to think of muscles as simply muscles but in fact, there are broadly two basic muscle types – striated muscles (that includes those postural muscles for good posture) and smooth muscles.

  • Striated muscles are your skeletal muscles. Muscles that you usually think of such as your bicep muscle or calf muscle.Your heart muscle is also a type of striated muscle but stands distinct from the rest of the skeletal muscle.
  • Smooth muscles are usually involuntary muscle that blends in other tissue type to form say your bladder or intestines.

Longer Weaker, Shorter Stronger

One key difference between striated and smooth muscles is that the strength of the striated muscle weakens the further it is stretched apart. So the same muscle, at say, 10cm length will exert a lot of more force at both ends as it contracts then if the same muscle is stretch to, say, 20cm. More specifically the strength of the muscle is a function of the area of its cross-section – the fatter, the strong the muscle.

Smooth muscle is different is this respect. It doesn’t lose its strength as it gets stretched out. An important feature to have with a full bladder or stomach.

So now we know that skeletal muscle, a type of striated muscle, is weaker when it is stretched and stronger when it is shortened.

What Does This Mean For People With Bad Posture?

It means that one of the key things to do to strengthen weak posture muscles it to shorten the lengthened ones and lengthen the shortened ones. That is get your posture right to strengthen the key postural muscles and to release to the overly tight/strong muscles that is pulling you out of the right posture.

Sustaining good posture and strengthening the postural muscles is further confused by how we think about muscle strengthening programmes. To build strong muscles, we generally think about more repetitions, heavier weights and repeat as required. This works if we are talking about big power muscles such as your biceps and thigh muscles.

Fast Twitch VS. Slow Twitch Muscles And Posture

Postural muscles have a higher percentage of Type I (slow twitch) fibres. These are fibres that are designed for endurance, not power.

This means for slow twitch fibres, a better type of exercises is one where we use lower load threshold and holding it for longer periods of time. Again, it sounds exactly like holding the right posture for prolonged periods of time (with proper rest periods in between) will improve your posture over time.

When a movement is loaded with too heavy a load, the fast twitch (Type II) muscle fibres take over.This is one of the reason why lower load exercises like pilates and yoga are better for people with low back problems than heavy workouts at the gym.


Types of Muscle Fibres
Fiber Type Type I fibers Type II a fibers Type II x fibers Type II b fibers
Contraction time Slow Moderately Fast Fast Very fast
Size of motor neuron Small Medium Large Very large
Resistance to fatigue High Fairly high Intermediate Low
Activity Used for Aerobic Long-term anaerobic Short-term anaerobic Short-term anaerobic
Maximum duration of use Hours <30 minutes <5 minutes <1 minute
Power produced Low Medium High Very high
Mitochondrial density High High Medium Low
Capillary density High Intermediate Low Low
Oxidative capacity High High Intermediate Low
Glycolytic capacity Low High High High
Major storage fuel Triglycerides Creatine phosphate, glycogen Creatine phosphate, glycogen Creatine phosphate, glycogen
Myosin heavy chain,
human genes