Effect of long-term neck muscle training on pressure pain threshold: a randomized controlled trial. Eur J Pain. (2005)

Abstract
Muscle tenderness has been measured in several studies to evaluate effectiveness of treatment methods, but only short-term results have been reported so far. The aim of the present study was to evaluate the long-term effects of two different muscle training methods on the pressure pain threshold of neck muscles in women with neck pain. Altogether 180 woman with chronic, non-specific neck pain were randomized into three groups: neck muscle endurance training, neck muscle strength training and control groups. The main outcome measures included pressure pain threshold measurement at six muscle sites and on the sternum. Neck pain was assessed by a visual analogue scale (VAS). At the 12-month follow-up statistically significantly higher pressure pain threshold values were obtained in both training groups at all muscle sites compared to the baseline, while no significant change occurred in the controls. Significantly higher changes in pressure pain threshold were detected at all six sites in the strength training group and at four out of six sites in the endurance training group compared to the control group. This is the first study to show an increase in pressure pain thresholds as a result of long-term muscle training. A decrease in neck pain was associated with reduced pressure pain sensitivity in neck muscles, showing that the pressure pain threshold may be a useful outcome measure of the effectiveness of neck muscle rehabilitation.

My comments
I think this study was done on the same population as the one I blogged on previously (exact exercise program described there) where both strength and endurance training improved pain and ROM better than stretching alone. This study found a significant decrease in tender points in both the strength and endurance groups as compared to the stretching only control group. The strength group was a little better off than the endurance group.
Quotes from the paper I found particularly interesting were as follows:

“Our finding supports this earlier finding that stretching with light aerobic exercise does not seem to have much effect on pressure pain threshold values.”

“Emotions like fear may exacerbate pain (Keefe et al., 2004). Fear can be diminished or blanked out by consciously exercising structures that have been associated with pain (Klaber et al., 2004).

The latter quote is interesting enough that I am going to order both the Keefe and Klaber references which might make for a good future physical therapy blog.