Progressive Resistance Training

Progression is the act of timely moving towards a goal until it has been accomplished.  Progressive overload is defined as increasing stress on the body gradually and it is accomplished by alternating intensity levels, amount and speed of repetitions, rest duration, and volume of training.  In the body, volume of training affects metabolic, hormonal, and neural responses and is indirectly related to the velocity of a muscle contraction.  It is important to note that the amount of sets in an exercise is not as effective as incorporating variation into training volume.  According to Ratamess et al. (2009), in untrained participants, 45-50% of 1-RM loads improve strength but weight variations have shown to be the most successful for progression. Variation, also known as periodization, involves a methodical process of changing one or more factor in training, like intensity or volume.  The various types of models are linear or classical, reverse linear, and undulating or nonlinear.

Resistance training improves wellbeing and motor performance, decreases cancer risk and other chronic diseases, and generates more force through many neuromuscular mechanisms.  Depending on the exercise performed a two to three minute rest is suggested.  Moderate to fast velocities and a minimum of one of 8 to 12 repetitions specifically targeting each major muscle group is recommended.  Weight machines are safer but free weights improve coordination and dramatically increasing volume increases overtraining risk.  Dynamic strength exercises include mostly concentric and eccentric actions and isometric exercises are not as common.  

References 

Ratamess, Nicholas A; Alvar, Brent A.; Evetoch, Tammy; FACSM; Housh, Terry J; Kibler, W.

Ben M.D; Kraemer, William J.; Triplett, N. Travis. Progession Models in Resistance 

Training for Healthy Adults. (2009). Medicine & Science in Sports & Exercise. 41(3): 687-

708.