The ability itself is Kṛṣṇa
BG 7.8 — pauruṣaṁ nṛṣu — "I am the ability in man"
BG 7.9 — jīvanaṁ sarva-bhūteṣu — "I am the life of all that lives"
BG 7.10 — buddhir buddhimatām asmi, tejas tejasvinām aham — "I am the intelligence of the intelligent, the prowess of the powerful"
BG 7.11 — balaṁ balavatāṁ cāham — "I am the strength of the strong"
BG 10.41 — whatever is glorious, beautiful or mighty springs from a spark of His splendour. The deer's speed is a spark.
But it is issued through a body — and the body is a separate factor
BG 18.61 — yantrārūḍhāni māyayā — the living entity is seated as on a machine made of material energy. A machine has specifications. You did not order yours.
BG 15.9 — the living entity takes a particular type of ear, eye, tongue, nose, touch — and with those, engages the sense objects. The word particular is the whole point.
BG 18.13–14 — the five factors of any accomplished action: adhiṣṭhānam (the seat/body), kartā (the doer), karaṇam (the instruments/senses), ceṣṭāḥ (the endeavours), and daivam (the fifth — providence).
Your effort was the fourth factor. Fast-twitch fibre density, tendon elasticity, limb-lever ratios — that's adhiṣṭhānam, factor one. You were pouring everything into factor four and demanding that it overrule factor one.
What determines which machine you get
BG 13.22 — kāraṇaṁ guṇa-saṅgo 'sya sad-asad-yoni-janmasu — association with the modes is the cause of birth in higher and lower species.
BG 14.18 — goodness rises, passion stays, ignorance descends.
BG 8.6 — yaṁ yaṁ vāpi smaran bhāvaṁ — whatever state of being one remembers at death, that he attains. This is your "conceptions we form till we leave the body."
So what is mine?
BG 3.27 — ahaṅkāra-vimūḍhātmā kartāham iti manyate — bewildered by false ego, one thinks "I am the doer."
BG 18.16 — one who sees himself as the only doer, not seeing the five factors, na sa paśyati — he does not see at all.
BG 2.47 — right to the work, never to the fruits.
BG 6.5 — uddhared ātmanātmānaṁ — elevate yourself by your own mind. Keep this one. It's your guard-rail (see §5).