To test the efficacy and accuracy of a novel non-invasive lactate sensor in humans undergoing strenuous leg exercise.

The study investigators have designed a novel non-invasive lactate sensor (Lactisense) Lactisense is a planar, flexible, passive, chip-less resonator that can be taped to the skin in order to measure lactate levels in the body. It sends a signal to a nearby reader, which can be translated into a concentration value. It has so far been tested in the lab with good accuracy, but has not been tested on humans. The sensors are designed to use very low energy microwaves that can detect alterations in interstitial and muscle metabolites.

In this study the investigators will test the sensor by having participants perform strenuous exercise (lifting weights) with Lactisense sensors attached to their skin on the top of the thigh and upper arm to evaluate lactate levels at the site of production and systemic levels respectively. The exercise will be performed using a well-established protocol to elevate lactate levels using a leg-press weights machine. The investigators will use a commercial capillary blood lactate meter (via finger prick) to verify whether lactate levels are actually changing in the body, and use Lactisense to try to measure these changes and compare to the values obtained using the commercial capillary blood lactate meter.

Inclusion Criteria:

Healthy and physically active volunteers

Exclusion Criteria:

Existing health conditions e.g blood pressure > 150/95, joint injury that would contraindicate exercise. Individuals who answer "yes" to any of the health condition questions on the PAR-Q questionnaire will also be excluded. As ketones might interfere with the sensor signal, we will exclude anyone with metabolic conditions or following a ketogenic diet.