Modified pull-up test is currently performed as a test of muscular endurance in females. But the measurements of this test, which reported by some universities, often have a large scatter in results. One of the reasons may be the difference of a posture in the modified pull-up. Then we built a static model and estimated the suspended force applied on both palms.
The suspended forse (T) is derived by the following expression.
T = x/b • (cos(α-β))/sinβ • W
where. W : body weight, x/b : relative position of CG, α: angle between upper limbs and the horizontal ground, β: angle between upper limbs and trunk.
It is found that the force(T) is the function of (x/b), W, α, and β.
There are variations in the value (x/b) and W between different subjects. In this sutdy the mean value of x/b is 58.6 %(SD = 1.5 %) for 34 female university students.
The angle α and β are, on the other hand, varied by the posture. When an accurate posture is made according to the manual, the angle β is fixed 90° and α is calculated to be 55.6 ± 1.5° in our subjects. Using the previous expression, the force(T) is made 33.0 ± 4.8 kgw, corresponding to 58.6 ± 1.5 % of individual body weight.
In practical testing, the angle β may be carefully followed to be 90°, however, the angle α has not been paied attention. With increasing the angle α, the greater force becomes applied to arms, and the performance of repetiton would be found to be reduced consequently.
In muscular endurance test, a constant work load, which is expressed by the ratio of body weight or maximal strength, should be applied to all subjects. Therefore, we concluded that the angle a should be described in the manual.