The present invention relates to methods for improving muscle performance wherein a subject is administered an efficacious dose of a mixture of water soluble extracts of green and black tea. The invention also relates to a method of increasing antioxidant capacity and glutathione reductase while preventing the increased cortisol response in a subject and a method for improving testosterone levels in a subject following exercise, comprising the step of administering to a subject an efficacious dose of a mixture of water soluble extracts of green and black tea. Other aspects of the present invention relate to improving cortisol stress response and/or testosterone levels following exercise.
