Factors Effecting Serum Testosterone
1. Resistance Training
Appropriate resistance exercise causes an increase in serum T post exercise of up to 70% (5,6,8,9,10). T response to an identical workout can however fluctuate widely (10). This suggests that resistance exercise interacts with other factors to cause elevated serum T. There are a number of conflicting theories as to the possible cause of this increase. Renal blood flow is reduced and this may lead to decreased metabolic clearance of T. There may also be an alteration in testicular blood flow causing an increase in secretion from the Leydig cells. Lastly a decrease in plasma volume due to movement of water out of the cardiovascular system, would cause an increase in T concentration without an increase in total T (8,9,10).
Further increases in strength, in highly trained strength athletes, are highly correlated with increases in bioavailable T (that not bonded to SHGH) and LH (5). The T: SHGH ratio may therefore reflect individual trainability at a given time and positive changes in the ratio may be a long term adaptation to training (5). Periods of overtraining (over-reaching) cause a decrease in serum T but an increase in LH suggesting a reduced utilisation of LH in the Leydig cells. Overtraining also causes a significant increase in the catabolic hormone cortisol. The cortisol:T ratio has been suggested as an indicator of the balance between anabolic and catabolic mechanisms (7).
Multi-joint exercises, such as squats, that utilise large muscle masses are more effective than isolation exercises of smaller muscle groups (6). Some evidence suggests T concentrations decrease after around one hour of intense resistance training. Further research is required to determine the optimum volume, intensity and recovery to induce the greatest increase in T. One regularly quoted study compared the following popular lifting protocols (9):
1. 10 reps, 1 minute recovery
2. 5 reps; 3 minute recovery
It was found that the second workout caused the greatest elevation in T. This suggests that providing intensity remains sufficiently high, increases in volume through higher repetitions and/or decreased recovery induces the greater elevation in serum T (8,9).
By David Woodhouse
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