Multi-functional device having a compression spring and associated method(s)

A portable muscle training device comprising:

• a spring having a central longitudinal axis, a proximal end, and a distal end axially opposed from said proximal end;
• a first appendage-receiving member being located adjacent to said proximal end of said spring;
• a second appendage-receiving member being located adjacent to said distal end of said spring;
• a first coupling being detachably affixed to said first appendage-receiving member and further being statically and fixedly engaged with said proximal end of said spring;
• a second coupling being detachably affixed to said second appendage-receiving member and further being statically and fixedly engaged with said distal end of said spring;
• and
• a spring-tension adjustment member being detachably connected to said second appendage-receiving member and further being adjustably and detachably connected to said second coupling;
• wherein an operating force of said spring is selectively adjusted when said second coupling is linearly reciprocated along the central longitudinal axis of said spring;
• wherein said spring has a spiral and helix shape;
• wherein said spring-tension adjustment member is concentrically spaced about said spring;
• wherein said spring is disposed along a single plane and intercalated directly between said first coupling and said second coupling.