Observations and opinions regarding arm action.
When talking about arm action you’re talking about five components:
- Shoulder complex i.e. scapula.
You are also talking about three results of arm action:
Discussions regarding arm action very rarely if ever take into account all of the above.
Some additional questions/thoughts regarding arm action.
Why does one pitcher throw 95 mph with no movement and another pitcher throw 95 mph with great movement?
Why was it that Billy Wagner at 5’10" and Randy Johnson had 6’10" both threw with the same velocity?
How come so many pitchers who are 6’5" tall and weigh 230 pounds throw no faster than their 6 foot 180 pound counterparts?
Swinging a bat and throwing a baseball arm biomechanically identical.
Biomechanical simulations indicated as possible to throw 95 mph with no active muscle activity other than iso-metric actions (holding and then releasing), i.e., no active contractile activity as defined by muscle shortening actions.
The following is only for those who have nothing better to do with their lives other than to try and understand how the body actually throws the baseball.
[quote]Theory One (Ford, 1998) states that once the motion of the system begins, an angular momentum is developed in the system and the distal segment lags behind. As the proximal segment approaches maximum velocity, an external force opposes this motion, which negatively accelerates the proximal segment, allowing inertia to propel the distal segment forward. Kreighbaum and Barthels explained that as a result of the negative acceleration of the proximal segment, the axis of rotation for the more proximal segment shifts from the proximal end to the distal portion, decreasing the radius of gyration, thus decreasing the rotational inertial for the more distal segments (Kreighbaum & Barthels,1985).
This theory is the more widely accepted of the two theories and has been studied in various movements (e.g. throwing, kicking, striking). The most common analysis of Theory One is the overhand baseball throw. In a study simulating the overhand throw, Herring concluded that a series of events including: (1) proximal-to-distal sequence of the onset of joint moments, (2) simultaneous peaking of segment velocities at the instant of the preceding segments minimal velocity and (3) reversing moments, created an inertial influence on the acceleration of the distal segment (Herring & Chapman, 1992). Another study that supported Theory One utilized a model to fractionate the three dimensional angular acceleration vector of the segments during an overhand throw into the two-dimensional kinetic and kinematic parameters (Feltner, 1989).
The results of this computer model revealed that the elbow extensor muscles created no extension moment as the distal segment began its rapid extension, suggesting that the inertial component of this joint action was the responsible agent for elbow extension. While Feltner was the first to propose that the elbow extensors did not contribute substantially to elbow extension during the overhand throw, it was not until Dobbins (Roberts, 1971) who, through the use of a differential radial nerve block to eliminate triceps activity, was able to provide substantive proof. Dobbins reported that after six practice trials, the participants were able to throw at greater than 85% of the velocity attained before the nerve block. These findings give credence to Feltner’s suggestion of the relative lack of contribution of the elbow extensor muscles during the rapid elbow extension during the overhand throw. The notion that the elbow extensors sparsely contribute to elbow extension in the overhand throw was further supported by two other groups, who reported very little elbow extensor activity during the rapid elbow extension using EMG analysis (Toyoshima et al., 1976; Atwater, 1979; Fleisig et al., 1995), each supporting the inertial based Theory One (Ford, 1998)[/quote]