You know how muscles get weaker when not used, for example with prolonged bed rest or spaceflight.

At what rate do muscles get weaker in the absence of exercise?
A person gets weaker as they get older – is this the same mechanism or is it due to lack of muscle build-up in the presence of exercise?
What could cause foot muscles to get much weaker overnight? What could cause inactive muscles to get much weaker over a two hour period assuming an adequate protein intake?

Some info here:

http://www.webmd.com/healthy-aging/sarcopenia-with-aging

And more than you could ever want to know, with linked references, her:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3429036/

It’s a review of the research on muscle loss with age. And it’s a long read.

mollwollfumble said:

You know how muscles get weaker when not used, for example with prolonged bed rest or spaceflight.

At what rate do muscles get weaker in the absence of exercise?
A person gets weaker as they get older – is this the same mechanism or is it due to lack of muscle build-up in the presence of exercise?
What could cause foot muscles to get much weaker overnight? What could cause inactive muscles to get much weaker over a two hour period assuming an adequate protein intake?

The formula I was taught (for functional strength loss due to complete immobilisation) is 10% per day.

Significant loss of ability to produce force (in individual muscles) over a very short period suggests venom. I am not aware of any other explanation.

>What could cause foot muscles to get much weaker overnight? What could cause inactive muscles to get much weaker over a two hour period assuming an adequate protein intake?

RAS, both transient adjustments/varitions, but there are too the possibility of permanent changes from lesions, and probably cell/neuron death

Ever noticed when you’re unwell a type of fatigue limits the energy(and will) to summon the usual force that you use to lift and move.

brain fatigue generator

http://en.wikipedia.org/wiki/Reticular_activating_system

The reticular activating system (RAS), or extrathalamic control modulatory system, is a set of connected nuclei in the brains of vertebrates that is responsible for regulating arousal and sleep-wake transitions. As its name implies, its most influential component is the reticular formation.

mg

transition said:

http://en.wikipedia.org/wiki/Reticular_activating_system

The reticular activating system (RAS), or extrathalamic control modulatory system, is a set of connected nuclei in the brains of vertebrates that is responsible for regulating arousal and sleep-wake transitions. As its name implies, its most influential component is the reticular formation.

Now I get my noradrenalin sensitivity. Thanks transition.

buffy said:

Some info here:

http://www.webmd.com/healthy-aging/sarcopenia-with-aging

Quoting from link.
> Researchers believe the following factors play a role:

> Age-related reduction in nerve cells responsible for sending signals from the brain to the muscles to initiate movement
> A decrease in the concentrations of some hormones, including growth hormone, testosterone, and insulin-like growth factor
> A decrease in the body’s ability to synthesize protein

None of these is associated with accelerated rate at which muscles get weaker. The first might explain why it becomes more difficult to get out of a chair after sitting in it for a while.

> Inadequate intake of calories and/or protein to sustain muscle mass

Not a problem.

this has happened to you?

wookiemeister said:

this has happened to you?

it happens to all of us.

I’ve found you can start doing damage by holding your body in strange positions or exercising wrongly

standing at a work bench without a foot up and forwards will lead to back pain for example

buffy said:

And more than you could ever want to know, with linked references, her:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3429036/
It’s a review of the research on muscle loss with age. And it’s a long read.

> The physical challenges of rising from a chair, dressing and walking, bringing food to the open mouth …

Yes, having trouble with all four of those. Troubles with the fourth are unrelated – due to arthritis.

> approximately a quarter of those over 90 years of age …

I’m less than 60, aging too quickly.

> loss of skeletal muscle with old age

It’s not a loss of skeletal muscle, rather, an unpleasant weakness of skeletal muscles that ought to be stronger. Not losing muscle mass, losing muscle strength after any sort of short rest.

> with aging the decline in strength exceeds that of muscle size … Strength decreases with advancing age. Average rates of loss are 2–4% per year. This is 2–5 times faster than muscle mass is lost

Yes. I was wondering whether decline in strength could be correlated to low blood pressure or low blood glucose, given that blood pressure declines during resting and that muscles need glucose to function.

> … Baumgartner …

Him again? :-)

> As most muscles act across joints via tendons, changes in other connective tissue elements will indirectly affect the muscle’s mechanical behavior (its length–force relation)

This is my doctor’s favourite idea – problems with tendons and other connective tissue elements.

> The use of simple hand grip strength near-isometric dynamometers has been established for more than seven decades

Hand grip is a hopeless measure of muscle strength. Hopeless for me because of arthritis in hands, nothing to do with muscle strength. Also, for me it’s foot and leg muscles that hinder standing up, walking and dressing without falling over.

> Lower limb strength is lost more rapidly than upper limb strength … the loss in strength greatly exceeds the loss of muscle mass

OK, that fits. But no explanation is given in the article as to why.

> with aging, the maximum shortening velocity of type I and IIA fibers decreases by c. 20–46 and 10–30%, respectively, and these changes are seen in both males and females … decrease in the actin sliding velocity on purified myosin isoforms prepared from aged muscle determined by in vitro motility assays … Within fibers, myosin concentration falls with age. Within each fiber type, the specific tension generated is almost proportional to the myosin concentration.

Ah, now the article is starting to get more scientific. Perhaps I need more myosin.

> It has long been recognized that the pattern of histological changes seen in muscle, described above, suggested that denervation significantly contributed … The total number of limb motoneurons in the human lumbosacral region of the human spinal cord was found to average at 57–60,000 before 60 years dropping to 45,000 in octogenarians

So older people become less nervous ;-)

> Compromised vascularization … due to fibers being smaller and the resulting capillary density is unchanged.

ie. partial blockages of blood vessels.

> mitochondrial dysfunction

OK

In summary, the article gives that appearance of listing all the hypotheses for Sarcopenia that the authors can dream up, with no more than a token attempt to apply the scientific method to determine which hypotheses are the correct explanations. The authors finally conclude by suggesting more exercise – which is the modern doctor’s self-palliative.

mollwollfumble said:

buffy said:

And more than you could ever want to know, with linked references, her:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3429036/
It’s a review of the research on muscle loss with age. And it’s a long read.

> The physical challenges of rising from a chair, dressing and walking, bringing food to the open mouth …

Yes, having trouble with all four of those. Troubles with the fourth are unrelated – due to arthritis.

> approximately a quarter of those over 90 years of age …

I’m less than 60, aging too quickly.

> loss of skeletal muscle with old age

It’s not a loss of skeletal muscle, rather, an unpleasant weakness of skeletal muscles that ought to be stronger. Not losing muscle mass, losing muscle strength after any sort of short rest.

> with aging the decline in strength exceeds that of muscle size … Strength decreases with advancing age. Average rates of loss are 2–4% per year. This is 2–5 times faster than muscle mass is lost

Yes. I was wondering whether decline in strength could be correlated to low blood pressure or low blood glucose, given that blood pressure declines during resting and that muscles need glucose to function.

> … Baumgartner …

Him again? :-)

> As most muscles act across joints via tendons, changes in other connective tissue elements will indirectly affect the muscle’s mechanical behavior (its length–force relation)

This is my doctor’s favourite idea – problems with tendons and other connective tissue elements.

> The use of simple hand grip strength near-isometric dynamometers has been established for more than seven decades

Hand grip is a hopeless measure of muscle strength. Hopeless for me because of arthritis in hands, nothing to do with muscle strength. Also, for me it’s foot and leg muscles that hinder standing up, walking and dressing without falling over.

> Lower limb strength is lost more rapidly than upper limb strength … the loss in strength greatly exceeds the loss of muscle mass

OK, that fits. But no explanation is given in the article as to why.

> with aging, the maximum shortening velocity of type I and IIA fibers decreases by c. 20–46 and 10–30%, respectively, and these changes are seen in both males and females … decrease in the actin sliding velocity on purified myosin isoforms prepared from aged muscle determined by in vitro motility assays … Within fibers, myosin concentration falls with age. Within each fiber type, the specific tension generated is almost proportional to the myosin concentration.

Ah, now the article is starting to get more scientific. Perhaps I need more myosin.

> It has long been recognized that the pattern of histological changes seen in muscle, described above, suggested that denervation significantly contributed … The total number of limb motoneurons in the human lumbosacral region of the human spinal cord was found to average at 57–60,000 before 60 years dropping to 45,000 in octogenarians

So older people become less nervous ;-)

> Compromised vascularization … due to fibers being smaller and the resulting capillary density is unchanged.

ie. partial blockages of blood vessels.

> mitochondrial dysfunction

OK

In summary, the article gives that appearance of listing all the hypotheses for Sarcopenia that the authors can dream up, with no more than a token attempt to apply the scientific method to determine which hypotheses are the correct explanations. The authors finally conclude by suggesting more exercise – which is the modern doctor’s self-palliative.

The paper is not a list of all the hyptheses the authors can “dream up”. It is a review paper of the literature on research to date.

buffy said:

The paper is not a list of all the hypotheses the authors can “dream up”. It is a review paper of the literature on research to date.

Of course.

mollwollfumble said:

The authors finally conclude by suggesting more exercise – which is the modern doctor’s self-palliative.

Have you tried it?

I have to say I find the reported effects of spending too much time sitting a bit of a worry, which doesn’t (so far) stop me from spending too much time sitting.

The Rev Dodgson said:

mollwollfumble said:

The authors finally conclude by suggesting more exercise – which is the modern doctor’s self-palliative.

Have you tried it?

Many years ago.

For the past several years I’ve been wearing a pedometer constantly and trying to keep the daily total up. Pedometer support has recently cracked and new replacement from Rebel sport is total #$%^, resetting itself to zero at unpredictable intervals many times a day.

mollwollfumble said:

The authors finally conclude by suggesting more exercise – which is the modern doctor’s self-palliative.

we are living in an obesity epidemic…

“Oh, it was horrible Johnny, there was cheesecake and pork chops everywhere.”

Moll, I’ve recently started lifting weights after a long layoff. I’m looking to build strength only and doing short repetitions with heavy weight.

I did lift weights for exercise up until about 10 years ago, before deciding to become a well rounded couch potato.

The thing is, strength is increasing at a very fast rate. I’m doing a routine of two differnt sets of exercises. Type A and B.
The routine is:

Day 1 Type A
Day 2 rest
Day 3 Type B
Day 4 rest
Day 5 Type A
Day 6 rest
Day 7 rest
Day 1 Type B
Day 2 rest
Day 3 Type A
Day 4 rest
Day 5 Type B
Day 6 rest
Day 7 rest
rinse and repeat.

Since I found my maximum weight to lift in each exercise, I have been increasing weights by 2.5kg every new session without fail. I’m wondering when I will slow this down, it is sure to happen soon. It amazes me how quickley strength is being gained.

Apparently if you can believ the layfolk at the internet, this is not an uncommon occurance when someone has once trained for mucle mass or strength, lost it due to inactivity or otherwise, and then decided to regain it some time later.

mollwollfumble said:

You know how muscles get weaker when not used, for example with prolonged bed rest or spaceflight.

At what rate do muscles get weaker in the absence of exercise?
A person gets weaker as they get older – is this the same mechanism or is it due to lack of muscle build-up in the presence of exercise?
What could cause foot muscles to get much weaker overnight? What could cause inactive muscles to get much weaker over a two hour period assuming an adequate protein intake?

Socks. I think socks is the problem. That’s what could cause inactive foot muscles to get much weaker over a two hour period when feet are raised and blood pressure is low. The socks constrict the blood supply to foot muscles.