The 'T' factor

By Perry Stewart

A training regime designed to boost testosterone can increase muscle growth, strength and power, consequently improving body composition. But getting the balance right is essential.

Living in such a competitive environment means that we are always seeking ways to achieve our physical potential whether for competing within sport, setting personal bests or looking and feeling good. We meticulously choose and adopt specific resistance training protocols in the hope of achieving the desired physiological responses. Although our knowledge on how the body adapts to different training modalities is increasing, it is probably fair to say that little consideration is given to how resistance training induces beneficial hormonal responses.

Optimal responses

The function of the endocrine system (tissues and glands that secrete hormones) is to maintain homeostasis (physiological equilibrium) via hormonal reactions. Exercise disrupts homeostasis, evoking hormonal reactions. By successfully manipulating training protocols and consequently evoking appropriate hormonal reactions, it is possible to increase the cross-sectional area (CSA) of muscle, and improve strength, power and body composition. However, if significant miscalculations are made, the result may be regressive and catabolic, leading to overtraining.

The endocrine system is directly affected by five resistance training variables: exercise modality, exercise sequence, intensity/load, sets and repetitions (volume) and rest period. Understanding how these affect the endocrine system is thus essential to plan and implement training programmes effectively.

Testosterone at work

Testosterone (TST), a steroid hormone, is associated with potent anabolic activity (synthesis of larger tissue) and has therefore been proposed as a physiological marker to evaluate the anabolic status of the body. TST is thought to contribute to muscle protein synthesis, whilst reducing protein degradation [1]. Its effects on muscle tissue include both direct (muscle growth, muscle fibre transformations IIx to IIa, inhibition of muscle glycogen breakdown) and indirect adaptations (stimulation of growth hormone, neural adaptations). TST in higher concentrations is also associated with improvements in body composition.

TST is secreted primarily in the testicles for males and ovaries in females, with concentrations 1520 times lower in females than males [2]. This may go some way towards explaining the gender differences in CSA and strength. Further, this should help dispel the common misconception that women participating in resistance training will gain bulky muscles.

Training applications

The design of a training programme will influence the magnitude of acute hormonal adaptations. The optimised training protocol for the release of TST has been reported as follows [3]:

  • 35 sets of 510 repetitions performed close to repetition-maximum loads:

    i. Hypertrophy training 10 repetition maximum (RM) load, high volume of 3 sets, 1 minute's rest.

    ii. Strength training 5 RM load, moderate volume, 3 minute's rest.

Training strategies to enhance TST are explained below and summarised in Table 1:


Train large muscle groups: large muscle group exercises such as squats, deadlifts, Olympic lifts and jump squats significantly increase TST concentrations, whereas little or no change has been reported with exercises involving smaller musculature (including bench press). Therefore, within a training session, large muscle group exercises should be performed before small muscle group exercises in order to expose the smaller musculature to the increased concentrations of TST. This is supported by research that measured strength changes in the biceps following 9 weeks of strength training [4]. One group preceded bicep exercises with lower body training. Only this group showed significantly raised TST concentrations, with simultaneous increases in the strength of the biceps.


High volume and short rest periods: high volume of exercise, achieved by multiple sets, repetitions or exercises, combined with shorter rest periods, enhances the accumulation and maintenance of lactate and hydrogen ions (H+) which may act to stimulate acute release of TST. It may therefore be suggested that reducing activity during rest periods will limit the dissipation of lactate and hydrogen ions (H+) and thus keep TST elevated.


Limit total exercise time: limit exercise sessions to 60 minutes or less, as beyond this time TST levels may decrease, with an increase in cortisol secretion. This rise negatively affects the TST: cortisol ratio, causing a gradual progression towards catabolism (breakdown of tissue). Training little and often is a strategy commonly utilised by Olympic weightlifters who train at high frequencies (more than one session per day) but for short durations (eg, 30 minutes).


Time of day: TST concentrations are typically highest in the morning and lowest in the evening. Consequently, the question emerges whether it is better to exercise in the morning when concentrations are highest or to exercise in the evening to maintain increased concentrations throughout the day. One approach recommended is the use of split sessions [5], with a session divided into two parts to avoid neuromuscular fatigue and loss of intensity. This strategy may also assist in the maintenance of TST concentrations throughout the day.

Table 1: Key tactics to raise TST concentrations
1. Train large muscle groups.
  • Use large-musculature exercises, eg, squats, deadlifts, Olympic lifts and jump squats.
  • Perform the above before those for smaller muscle groups, maximising TST concentrations.

2. High volume and short rest periods is best for TST secretion.
  • 3 sets, 10 reps (the last rep should be very difficult), with 30 seconds' rest.
  • Your aim: increase accumulation of lactate and hydrogen ions (H+) by reducing duration and activity in rest periods.

3. Limit total exercise time.
  • Keep total exercise time to ≤60 minutes to minimise counterproductive effects of cortisol - better to train with greater frequency.

4. Time of day.
  • TST concentrations are highest in the morning use split sessions to keep levels elevated throughout the day.

Plan with care

Resistance training acutely increases TST concentration following the performance of high total work (35 sets of 510 repetitions), at high intensities (5 to 10 RM) and involving large musculature. This elevation is continued after the workout for up to 60 minutes before diminishing.

Please note that, for resting TST concentrations to be increased, a minimum of 2 years' resistance training experience is required.

Heavy resistance training has been shown to increase CSA, strength, power and (indirectly) body composition, which is in part due to the increase in TST. Understanding how TST contributes to neuromuscular adaptations and the strategies that enhance TST concentrations will provide important insights for the design of resistance programmes.

The bottom line is, if you are not optimising your training to increase TST levels, you may be limiting your performance.


1. Hurbst KL, Bhasin S. Testosterone action on skeletal muscle. Curr Opin Clin Nutr Metab Care, 2004, 7, 271277.

2. Kraemer WJ, Vingren JL, Spiering B. Endocrine responses to resistance training. In: Baechle TR, Earle RW (eds), Essentials of strength training and conditioning. Human Kinetics, Champaign, Illinois, 2008, 4164.

3. Kreamer WJ, Gorden SE, Fleck SJ et al. Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females. Int J Sports Med, 1991, 12, 228235.

4. Hansen S, Kvorning T, Kjaer M, Sjogaard G. The effect of short-term strength training on human skeletal muscle: importance of physiologically elevated hormone levels. Scand J Med Sci Sport, 2001, 11, 347354.

5. Turner AN, Comfort P, Moody J, Jeffreys I. Neuroendocrinology and resistance training in adult males. Prof Strength Cond, 2010, 17, 1524.


Perry Stewart is a Strength & Conditioning Coach and Lecturer at the London Sport Institute.

Please contact Perry with your comments and queries:


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