Geeta Iyengar, B.K.S. Iyengar's daughter and a yoga teacher in her own right, once said that poses are like mantras. As we repeat them, we do so with artha (purpose) and bhavana (feeling or contemplation). Patanjali describes this process in sutra 1:28. There it refers to the repetition of a mantra, specifically, the mantra Om. Each repetition is done with presence and awareness, so it doesn't become mechanical.