Sage Vishvamitra imparted a group of hymns, Bala (strength) and Ati Bala (super strength) to Sri Rama, on the southern riverbank of Sarayu. (Bala Kanda 22 Sarga 11-20 Slokas). He told the greatness of hymns, Bala and Ati Bala as follows:
On receiving these hymns neither tiredness nor fever, nor disfiguring of personality can effect you, nor the demons can charge you either you are sleeping or unvigilant. As it is none whosoever on earth can equal you in dexterity, Rama, and by reciting these hymns none can equal you in the three worlds.
My dear Raghava, if bala atibala hymns are practised, none can equal you in the world by your handsomeness, calibre, erudition, by your discernment, and even in replying or rebutting you.
On receiving these two teachings there will be none similar to you, for bala and atibala are the mothers of all knowledge. Oh, best one among men, Raghava, if you go on reciting bala and atiblala hymns, my dear Rama, there will be no hunger or thirst to you.
And if these twin teachings are practised an inestimable renown will also accrue, oh, Raghu's legatee, these two hymns that possess brilliance are the daughters of Forefather Brahma, and I intend to impart these hymns to you, as you are the most eligible one, hence take the teachings that are kept safe from the world.
Though all of these numerous qualities are undoubtedly available with you, that too in abundance, yet these hymns if ascetically nurtured will yield various results.
Sage Viswamitra goes on to say that Bala and Atibala are daughters of Lord Brahma and mothers of all knowledge.
Later, it was narrated by Sage Valmiki that, while going along with Sage Viswamitra, Sri Rama and Lakshmana did Sadhyopaasana (worship at the junctions of sunrise/sunset).
तस्य ऋषेः परम उदारम् वचः श्रुत्वा नृप नरोत्तमौ | स्नात्वा कृत उदकौ वीरौ जेपतुः परमम् जपम् ||
(Bala Kanda 23rd Sarga 3rd Sloka)
On hearing the benign words of the sage those valorous and best ones among men got up, bathed, and on offering water oblation they mediated upon the supreme hymn.
The supreme hymn, which meditated upon can be the Gayatri mantra.
My doubt is, if Sri Rama was already practising/meditating a supreme hymn like the Gayatri mantra, why did Sage Vishvamitra impart him the Bala and Ati Bala hymns, which are said to be the mothers of all knowledge?
Are Bala and Ati Bala hymns superior to the Gayatri hymn?