When we were carrying out the experiment on tight nosebands (you can download the published article here, over 45,000 people have!) the thing that surprised me the most was the complete lack of obvious signs that the horses were stressed.
I remember saying to the student working with me, "this is going to be very dull, I can't see any changes, other than the horses not chewing and things, except they seem to be standing more still...".
When I analysed the data however I was blown away. The photo above shows why.
The purple line above it the heart rate when the noseband was tight. The first reading is the 10min baseline reading, where the horses were standing in the stall. The treatment session was 10 minutes at varying tightness (UN - unfastened, CAUN - conventionally fastened, 2 fingers on the nasal plane, HCAUN - 1 finger at the nasal plane and NAUN - too tight to get any fingers under the noseband at the nasal plane).
What we are looking for is a change. You can see that in each of the other treatments, the horses' heart rates remained stable, no change. In the tight treatment, they went up significantly (p = 0.001) and didn't even manage to return to normal during the 10 minute recovery period where the bridle and nosebands were removed.
Unless we measure these parameters, it's impossible to know how stressed our horses are. Unlike a dog, cat or child, horses do not bark, cry, scream or complain.
I think one of the biggest things to change my riding and training has been the addition of a heart rate monitor.
Next time I'll discuss when and why I ride with one (not all the time but sometimes) but in the meantime, don't forget to leave me a comment.