Hello, Bruce is my name and I am from Queensland, Australia... and for several years I studied Kinesiology extensively and ran Classes/Trainings. There have been many thousands of people who, like myself, have worked with this modality and have come to know its many colors and facets.
The simply biofeedback mechanism of muscle response does indeed reveal the truth in a situation or condition.... as long as it is done correctly. Usually some training - even if its from a practicing kinesiologist - will assist one to do self-testing.
In using the self-test you described, it depends on how you ask the question and exactly what your intention is for that test. If you are Questioning... meaning a Yes or No response, then - as long as you are very clear on the Question and not being ambigious, a Yes will show a strong hold response, whilst a No will be a weak or not holding response.
Wheras, if you are looking for a direct response to a substance, a thing, an allergen, a toxin, a thought etc... then a strong or "switched on" response means that it does not effect your energy and therefore your physiology/metabolism.... wheras a "switched off" response means that it does.Therefore, in the case of testing wheat, dairy etc... as an example - if you have the substance/food in your mouth or hold it on your body... and it "switches off" your muscle response, then that would indicate a "sensitivity".
A Sensitivity is usually equated with an 'allergy', but the thing here is that a sensitivty can change under various environments, days, cycles or can be affected by your thoughts, emotions or something else you ate recently. Therfore, doing the Kinesiology often will show up your patterns of sensitivity, which can lead a person to better understand the complexity of allergies and general health.... and work toward Health building.
Kinesilogy can be a valuable tool to help us to be aware of the sensitivites that we may have to our foods, environment etc... and therefore modify those things over time toward feeding oursleves with what will support and switch on our energies... rather than be a victim to those things that switch us off or reduce our vitality.
I hope this helps...
Best of Health,
Bruce Gibson ND.