Always performed by a medical professional, but almost always overlooked by the health and fitness industry when measuring health and fitness, it's flippant not to measure core temperature. A raised temperature is an indication of the bodies processes (metabolism) reacting to fight disease or infection. If suffering from disease or infection, this will cause a negative impact on performance and impact many other fitness tests, for example, RHR and blood pressure may be raised and dynamic assessments performed with a lackluster approach. Therefore, identifying a raised temperature can prevent against recording lots of false fitness test data and allow you to treat your client to some needed rest.
Although we all seem to associate having our temperature measured with a mercury head thermometer in our mouth, or, joke with our friends about a thermometer in the bum, nowadays we will almost always have our temperature taken using an Infrared Ear Thermometer. As the eardrum shares blood circulation with the Hypothalamus (brain's 'thermostat'), an Infrared Ear Thermometer is a very reliable and non-intrusive method of measuring our core temperature.