T-bar rows -- and almost all row variations, in fact -- work all the major muscles in your back. This includes your lats, teres major or "little lat," trapezius and erector spinae. T-bar rows also work your shoulders and the pulling muscles in your arms -- biceps, brachialis and brachioradialis. Your abdominals, hamstrings and glutes must also fire to help stabilize your body in the bent-over position as you lift.
To perform a T-bar row, straddle the bar -- facing the handle -- and bend forward from the hips, knees slightly bent. Grasp the handle and pull the crossbar of the "T" up toward your chest. You'll find differing opinions about just how much you should allow your back to hinge upward from the hips, if at all, as you perform this lift. For a very conservative workout, aim to keep your back still. For a more dynamic lift, it's OK to let your back hinge up slightly as you lift, as long as you're not hyperextending it.
Minor Differences in Grip
T-bars come with wide grips -- palms facing either down or up -- and close grips, which position your hands close against the bar and emphasize lat engagement, since they keep your elbows close to your body. You can improvise a close-grip T-bar by jamming one end of an Olympic barbell into the corner of the room, then performing T-bar rows with the other end.