Final answer:
Muscle tension varies with activity, being minimal for light objects like an orange, slight but constant while standing, significant when lifting heavy objects like a couch, and generally very low during sleep. The force exerted is influenced by factors including the object's weight and opposing forces like friction.
Step-by-step explanation:
The amount of tension your muscle generates varies depending on the activity.
For lifting an orange, the tension would be minimal, as the weight is light. Standing motionless requires your muscles to generate enough tension to keep you upright; this is usually slight, but constant, isometric contraction.
Lifting a couch would require significant muscle tension due to the object's weight and often awkward positioning, which can put greater strain on your muscles, especially the back if not lifted correctly.
During sleep, the muscle tension is generally very low unless one is in the middle of a dream that involves movement.
The amount of tension is also related to the amount of force required to overcome both the object's weight and any opposing forces, such as friction when moving an object like a couch.
For example, moving a heavy couch would require overcoming the frictional force, which, given a normal force of 1 kN and a coefficient of friction of 0.6, can be substantial.
Muscle tension can also be affected by the number of cross-bridges formed between actin and myosin in the muscle fibers, and whether the muscle is performing isotonic (tension while changing length, as when lifting objects) or isometric contractions (tension without changing length, as when standing still).