Push-up

Start in a high plank position with your hands slightly wider than shoulder-width apart and your feet together.

Engage your core and lower your body towards the ground by bending your elbows, keeping your body in a straight line.

Pause for a moment when your chest is just above the ground, then push yourself back up to the starting position by straightening your arms.

Repeat for the desired number of repetitions.

Losing tension in the core or lower back partway through the movement — because Push-up loads multiple joints at once, a small breakdown in bracing at the hips or spine compounds through the whole chain.

Flaring the elbows too wide or letting the hips sag/pike, which shifts load off Pectorals and stresses the shoulder joint.

Rushing through reps using momentum rather than controlling both the lifting and lowering phase, which is especially important since there's no external load to force good tempo.

Progressing the load or reps too quickly before technique is consistent across every rep of every set.