What's making muscles sore?

Hello friends,

Following my last post debunking the myth that lactic acid is what causes soreness, you asked me to answer;

What causes muscle soreness after exercise?

(ps- lactic acid is an energy source for the muscles!)

So, let's get into the answer.

Muscle soreness after exercises has a few causes.

During exercise you might start to get a sensation of burn, fatigue, or twitching, or jelly legs when the muscle begins to run out of available energy.

Towards the end of a session you might noticed increased vascular flow creates that pumped, full, feeling, but it usually subsides within a few hours.

But that pain that comes in the 24-48 hours after and sometimes lingers a few days...

That pain when you can't take a seat because your thighs are so sore; the technical term is Delayed Onset Muscle Soreness or DOMS.

DOMS is not necessary to develop strength, despite what you might have been led to believe.

DOMS can be caused by:

- Inflammation in the muscle; created when demand on the muscles is higher than the muscle can currently deliver, then minor damage is caused. 

The micro damage is not a problem itself, provided that there is sufficient recovery time before re-damaging the area.

The rebuild, repair and restructure is actually one of the ways that strength is built and muscle grows (aka hypertrophy).

Tissue damage causes vasodilation, which creates swelling (even at a micro level), which creates pressure, which triggers nociceptors (pain receptors) to report pain. 

That swelling is there so that nutrients can be delivered to the tissue to heal, and damage can also be cleared up by an abundance of white cells.

- Myofascial trigger points as a result of local hypoxia when energy demand outpaces energy supply.

In other words, you're demanding more effort of that specific muscle area than it can currently perform, in a low oxygen environment, and the muscle maintains a contracted state.

I can't word it better than directly quoting this excerpt from the latest textbook "Understanding Fascia, tensegrity, and myofascial trigger points" by John Sharkey.

"When ATP supplies begin to diminish- a they will as muscles are used either over and extended period or for short time of high intensity- myosin heads remain bound to actin and can no longer swivel.

If calcium cannot escape from the sarcomere, the fibre may remain in a short state even though no nerve impulse is being received.

This can lead to muscles spasm,or at the micro level, to tight muscle fibres.

As muscles produce energy for high intensity activity through anaerobic metabolic pathways, this results in the production of lactates and inorganic phosphate."

Practices such as trigger point therapy and dry needling assist in release of calcium (that local twitch response when the needle is inserted), so that muscles can return to resting, functional length. 

Other massage/manual therapies can assist in recovery from DOMS by quieting and calming the nociceptors from signalling pain or caution, thus improving range of motion and reducing soreness. 

I hope that this explanation was clear enough to give you some understanding of what causes muscle soreness after exercise, and why massage can help. 

As you can see it's a bit of a complex function!