Chin-ups training program

“The chin-up (also known as a chin) is a strength training exercise designed to strengthen the latissimus dorsi muscle [...]

Chin-ups target the latissimus dorsi muscle, assisted by the brachialis, brachioradialis, biceps brachii , teres major, posterior deltoid, infraspinatus, teres minor, rhomboids, levator scapulae, middle and lower trapezius and pectoralis muscles. Chin-ups are thought to build width and thickness to one’s back, as well as to promote growth of the biceps, brachialis, brachioradialis and pronator teres.” Wikipedia

Chin-up variations

“Sternal chinups — this variant employs a full range of motion, raising the sternum to the bar. The elbows are nearly directly below the shoulders this way.
Towel chin-ups — a towel is looped over the bar, and instead of the bar, the towel is gripped.
Weighted chin-ups — weight is added with dangling from a dipping belt, or via weighted belt or vest, ankle weights, chains, medicine ball between the knees, dumbbell between the feet or kettlebells on top of the feet.
One handed chin-ups — one hand grips the bar; the other hand holds the wrist/forearm of the gripping hand. It stresses the grip equally to a one-arm chin-up, but lessens the amount of work the biceps and lat of the gripping arm have to do compared to it.
One forearmed chin-ups — one hand grips the bar; the other hand holds the upper arm of the gripping hand between the elbow and shoulder. It stresses the grip and bicep equally to a one-arm chin-up, but lessens the amount of work the lat of the gripping arm has to do compared to it.
One arm chin-ups — one hand grips the bar; the other hand does not assist with the pull, it cannot touch the other arm.
Drop chin-ups — the grip is released at the top of the movement, and the bar caught towards the bottom of the movement, to incorporate a slight drop. This variant is for advanced athletes only.
Supine chin-ups — in the supine position (with the feet initially supported), the arms are held perpendicular to the body as the grip the bar; the chest is pulled towards the bar instead of the chin. This exercise is performed in the horizontal (transverse) plane, whereas other chin-up variations are performed in the vertical (coronal) plane. As a result, this variation recruits the trapezius and teres major muscles much more than a vertical chin-up would and is often considered a type of row.” Wikipedia