a. a base;

b. a supporting frame vertically mounted on the base, the supporting frame including a lower resistance support and an upper resistance support that is slidably coupled to the lower resistance support, wherein the upper resistance support has a body portion defined by a top end portion and a bottom end portion, and the lower resistance support has a body portion defined by a top end portion and a bottom end portion;

c. a vertical track member mounted on the lower resistance support of the supporting frame, the vertical track member extending vertically from about the top end portion to about the bottom end portion of the lower resistance support;

d. a top spring-attachment member having a body portion defined by a first end portion and an opposite, second end portion, the body portion extending horizontally and mounted on about the top end portion of the upper resistance support;

e. a bottom spring-attachment member having a body portion defined by a first end portion and an opposite, second end portion, the bottom spring-attachment member extending substantially parallel to and spaced apart from the top spring-attachment member and moveably coupled to the vertical track member such that a movement of the bottom spring-attachment member occurs within the vertical track member; and

f. a resilient resistance member having a body portion with a body length of l defined by a top end portion and a bottom end portion, the resilient resistance member extending substantially vertical to and detachably affixed to the top and bottom spring-attachment members, respectively.