As in instructions to maintain bodily strength, to be able to fight, overall just emphasizing physical strength?
Welcome to StackExchange!
This text from the atharvaveda saMhitA is one that was traditionally used for bodily strength
vA~N ma Asan nasoH prANash chakShur akShNoH shrotraM karNayoH, apalitAH keshA ashoNA dantA bahu bAhvor balam. Urvor ojo ja~Nghayor javaH pAdayoH, pratiShThA ariShTAni me sarvAtmAnibhRRiShTaH.
Speech in my mouth, breath in my nostrils, sight in my eyes, hearing in my ears, my hair not gray, my teeth not broken, much strength in my arms. Force in my thighs, speed in my calves, firm standing in my feet, all things of mine uninjured, myself not down-fallen.