This double-blind clinical study controlled with placebo, being looked for to check the tonic effects in physical activity attributed to the roots of Pfaffia glomerata. It was selected 38 normal volunteers and it took place ergoespirometric tests, with mensuration of VO2 maximum, reached maximum load, frequency heart and blood levels of lactato. The volunteers received the extract of the roots or placebo for six months. It just happened a waiver in the group placebo, it was not verified clinicallaboratorials alterations and it scored minimum manifestations of adverse effects. The ergoespirometric test accomplished in the beginning and at the end of the clinical study it didn’t evidence positive or negative alterations in the several analyzed parameters. It was ended that, in the terms of the used protocol and with the number of involved volunteers, that the standardized extract of the roots of Pfaffia glomerata didn’t promote benefits to the volunteers in aptitude terms and physical activity.