I am going to briefly interrupt our series on Paracetamol this month, because I came across an excellent study in the journal of Applied Physiology by Shah etal in 2005, the results of which can really help us to understand what underlies the pain & dysfunction of unhealthy muscle.

Unhealthy muscle contains tight, painful areas. Physiologists call these ‘trigger points’, of which there are two types, ‘latent’ and ‘active’. Briefly:

1. a ‘latent’ trigger point is a ‘tight area in a muscle’ that is not painful unless pressed. Pressing leads to pain locally & sometimes also at sites called ‘referral’ points.

2. an ‘active’ trigger point has pain (local and/or referred) that is either:

a. present constantly, or

b. elicited simply by using the muscle

3. muscles containing trigger points are also usually tight, shortened, weaker, with altered nerve functions

4. Trigger points arise due to acute or chronic muscle overloading

5. If pain from an active trigger point worsens to become a persistent unrelenting deep ache, a person may be diagnosed with ‘myofacial pain syndrome’

By contrast, healthy muscle:

1. contains no trigger points

2. if pressed will yield easily & feel no pain, only pressure.

Evidence suggests ‘dry needling’ benefits sore muscles. Inserting a needle into latent or active trigger points will cause the muscle to:

1. contract strongly & suddenly, a reaction called a ‘local twitch response’ (LTR),

2. produce a specific ‘LTR’ electrical signal measurable by an EMG machine.

3. often feel significantly less painful afterward

In contrast healthy muscles (no trigger point) produce no LTR or EMG signals. So physiologists can use an EMG machine to confirm if a muscle is unhealthy (has a trigger point) or healthy (none).

Read more on this next edition