Wall Mounted Pendulum Power Stacks
Flexion at the elbow occurs in a palms up supinated, neutral or a palms down pronated position. The involved muscles are the bicep brachii, the deeper brachialis, and the brachioradialis.
The biceps brachii has two heads, the short head and long head both origins are found on the scapula and insertions on the radial tuberosity. One portion of the long head of the bicep inserts on the tuberosity of the forearms radius and the other part of its tendons bicep is an aponeurosis that originates from the distal insertion of the biceps brachii, and inserts into the deep fascia of the forearm. Aponeurosis is flat fibrous tissue that takes the place of a tendon having a wide area of attachment.
The brachialis originates 2/3rds down the upper arm deep to the bicep, a broad muscle with its widest part in its middle, inserting on the ulna tuberosity of the forearm. Regardless of hand position the brachialis is activated when doing a forearm flexion exercise.
The brachioradialis origin is the distal part of the humerus and inserts on the distal radius. If you stand up straight and put your hand at your side keeping your hand in a neutral position, and bring it to 90 degrees you can see this muscle contract. Seeing this, and contrary to most thought, this muscle is more activated when your hands are in a palms up position doing a curl.
The strongest position for activation of the bicep brachii and brachioradialis is several degrees above a 45 degree angle from the beginning of the curling motion. As mentioned the brachialis is activated at all times when flexing the elbow regardless of hand position, yet the position of the wrist will determine which of the active muscles is the most involved when lifting the load.
Performing a barbell curl with elbows alongside the chest activates all three muscles. As you raise the weight, a little bit of forward flexion of the shoulder will occur naturally, as the bicep plays a minor role in flexion of the anterior delts and pecs. This is only a minor movement and the lifter should only allow about 10 degrees of motion of the upper arm as the weight is raised.
What happens when flexing the elbow with palms down? When the hand is prone the bicep brachii is in a disadvantaged position, because of the biceps aponeurosis, the flat sheet tendonlike structure rotates, so now the brachioradialis has to carry the load with less help from the bicep. When the arm gets above 90 degrees whether the hand is palms up or down or in a neutral position the bicep is fully activated to elicit further upward movement.
As the weight is lowered eccentrically the biceps becomes maximally activated, the brachioradialis has minimal activity so pausing and concentrating on the lowering phase is important in building a strong bicep.
Should the lifter choose a barbell curl, EZ curl bar, dumbbell or a high low pulley based on muscle function and hand position?
A 2018 study, “Differences in electromyographic activity of biceps brachii and brachioradialis while performing three variants of curl.”, looked at EMG activity in three movements: the EZ curl bar, Dumbbell Curls, and the Barbell Curl. The researchers findings about the difference between usage of the EZ curl bar relative to the straight bar was “...the choice between these two variants purely a matter of subjective comfort related to the handgrip position.” They also found the dumbbell to be less effective in their research.
The effectiveness of the utilization of dumbbells for curling cannot be defined by this study. In the study, “Maximum bilateral contractions are modified by neurally mediated interlimb effects.” The force exerted by a single limb during a maximal bilateral contraction has been found to be less than the force associated with a maximal unilateral contraction.” This study indicates that single arm dumbbell curls may have a greater effectiveness. All aside, the bottom line is that it is great to have a variety of effective tools in training.
The advantage of the Pendulum Hi-Lo Power Stack is that there are an array of handles that can be changed quickly, as well as the weight can also be adjusted in seconds. You can supinate, pronate, semi-pronate, neutral grip, single arm, and insure each muscle group becomes maximally activated ---- a great way to Get Strong.