The gym is filled with all sorts of people that can sabotage your workout.  The guy that does a set and talks to his friends for five minutes is not going to have significant increases in testosterone from his workout.  All readers of Fitness Rx for Men know that in order to stimulate testosterone during a workout, training sessions must have short rest periods (30 seconds or less) with multiple sets, a training volume with 65-80% of a 1-RM, repetitions between 10-12 reps, and use large muscle mass exercises.  Large muscle mass exercises as deadlifts, squats, and jump squats have been shown to produce large increases in testosterone compared to small muscle mass exercises as arm curls18, 22.  Back in 1990, Bill Kraemer reported research that changed the way men needed to exercise with weights.  In that study, men trained with an equal weight training volume except one group trained with moderate exercise (using a weight they could lift for ten reps) and short rest periods (1 minute) while the other group used heavy exercise (5 reps ) with 3 minute rest periods.  The results were that men using high reps with short rest periods had increases in both GH and testosterone whereas the group using heavy weights with long rest periods had no changes in either testosterone or GH2.   Muscular hypertrophy and strength gains following resistance exercise are thought to be dependent on the intensity of exercise, in a way that an intensity of 65% of a 1-RM is required to achieve a substantial effect2.  Although it may seem that testosterone is a no-brainer for increasing muscle mass and strength, the data on the effects of testosterone on muscle performance are somewhat contradictory.

The "Intramuscular Growth Factor" Camp
Elevated testosterone levels have been reported to occur in occur in some studies 2, 7, 8, 9whereas several studies have shown no difference10, 11, 12, 13 or even reductions6, 15.  Not all studies in aging older men have shown that testosterone replacement therapy increases muscle strength33, 34.    It should be mentioned that some studies have used low dose testosterone gels and creams which are not as effective as shots for increasing testosterone which may negatively obscure results; additionally different dosages have been used in different studies.  Some researchers have even gone on to believe that the gains in strength and size are all related to "intramuscular growth factors" that are independent of testosterone.  A paper presented by Dr. Goldberg in 1975 stunned scientists about the relationship between muscle growth and testosterone.  In his research, he castrated rats so that they could not produce testosterone and put their leg muscle on tension overload.  Surprisingly, the rat's leg muscles grew in size suggesting that mechanical overload increases muscle hypertrophy independent of testosterone17.  Research scientists are now discovering the signaling pathway by which mechanical stimulation of contracting muscle and intramuscular growth factors as IGF-1 activity leads to changes in satellite cells, muscle DNA content, increased muscle protein synthesis, increased muscle mass, and strength. Other recent research has demonstrated that IGF-1 increases intracellular calcium ion concentrations leading to the activation of the muscle growth signaling pathway, and subsequent muscle fiber hypertrophy15, 16. For example, in one study ten healthy men completed eight sets of maximal eccentric squats. The intramuscular IGF-I mRNA concentration increased 62% but serum testosterone showed little change35. An increase in muscle hypertrophy can lead to greater increases in muscle strength.  Reports in the literature have suggested that the insulin-like growth factor I protein plays a major role in strength training-induced skeletal muscle hypertrophy and strength improvements. Some people due to differences in genetics express higher levels of IGF-1 than others, what we call "lucky bastards".  One study compared those that expressed high levels of IGF-1 levels to those that did not.  After 10 weeks of training, with a single-leg knee-extension strength training program, 1-repetition maximum, muscle volume, and muscle quality increased significantly for all exercising groups. , subjects whom expressed higher natural levels of IGF-1 levels gained significantly more strength than those whom did not. Thus the data suggest that the IGF-1 may influence the strength response to strength training.  Hold on…before I lose you to the side of the "intramuscular growth factor" group, there are some important considerations about testosterone and strength that needs to be addressed.