When hanging, the forehand is pull-ups, the arms are upright, the hands are slightly wider than the shoulders, the palms are forward, the feet are off the ground, and the skeletal muscles such as rectus abdominis, transverse abdominis, oblique abdominis and erector spinae contract with equal length to ensure that the spine is in a neutral position.
When the trunk moves upward, the biceps brachii and the brachialis muscle are far fixed and contract centripetally to bend the elbow joint; The near-fixed centripetal contraction of latissimus dorsi and deltoid muscle makes the big arm at the shoulder joint retract, which provides the main power for pull-ups, while the near-fixed centripetal contraction of the middle and lower bundles of trapezius muscle makes the scapula revolve.
When the trunk moves downward, the joint movement mode is opposite to that of the trunk moving upward, and all the skeletal muscles involved in the movement do centrifugal contraction to control the downward speed of the trunk.
Pull-ups: 1. Hold the horizontal bar with both hands, the grip distance is wide, slightly wider than the shoulders, the feet are off the ground, and the arms naturally droop and straighten.
2. Pull your body up with the contraction force of latissimus dorsi. When the chin exceeds the horizontal bar, pause for a second, let the latissimus dorsi contract completely, then gradually relax the latissimus dorsi, and let the body descend slowly until it is completely drooping. Say it again.
3, you can bend the knee joint and cross the two calves backwards, so that the body leans back slightly, which can better exercise the back muscles.
Baidu Encyclopedia-Pull-ups