The test detects a core chemical structure belonging to benzothiazepines. These compounds stabilize protein channels that would otherwise "leak" calcium from muscle cells during strenuous exercise.

Study leader Mario Thevis -- director of the Center for Preventive Doping Research at the German Sport University of Cologne in Germany -- said calcium is needed for muscle contraction and this leaking effect weakens the contractions and is a causal factor in muscle fatigue.

Thevis said the simple nature of the compounds means they are easy to make and sell as endurance boosters on the black market.

The study characterizes the compounds according to their weight and molecular structure. This gives the researchers a molecular "fingerprint" by which to identify the compounds, Thevis said.

The study, published in the journal Drug Testing and Analysis, shows that using high resolution mass spectrometry, JTV-519 and S-107 can be detected in spiked urine at concentrations as low as 0.1 nanograms per milliliter.