Abstract
Purpose: Limited data are available on the acute performance-enhancing effects of single-dose administration of testosterone in healthy humans. Studies of testosterone administrations to healthy humans are rare due to the difficult nature and necessity of close clinical monitoring. However, our unique physiological experimental facilities combined with close endocrinological collaboration have allowed us to safely complete such a study. We tested the hypothesis that an intramuscular injection of 250 mg mixed testosterone esters (TEs) enhances physical performance in strength and power exercises acutely, measured 24 h after injection. Additionally, we investigated whether the basal serum testosterone concentration influences the performance in countermovement jump (CMJ), 30-s all out cycle sprint, and one-arm isometric elbow flexion.Methods: In a randomized, double-blind, placebo-controlled design, 19 eugonadal men received either a TE (n = 9, 23 ± 1 years, 183 ± 7 cm, 83 ± 10 kg) or a PLA (n = 10, 25 ± 2 years, 186 ± 6 cm, 82 ± 14 kg) injection. Hormonal levels and the performance in CMJ, 30-s all out cycle sprint, and one-arm isometric elbow flexion were measured before and 24 h after injection.Results: Firstly, an intramuscular injection of 250 mg mixed TEs did not enhance the vertical jump height in a CMJ test, peak power, mean power, and fatigue index in a 30-s all-out cycle sprint or rate of force development and maximal voluntary contraction in a one-arm isometric elbow flexion 24 h post-injection. Secondly, baseline testosterone levels appeared not to influence performance in strength and power exercises to a large extent in healthy, recreationally active young men.Conclusion: A single intramuscular injection of 250 mg mixed TEs has no acute ergogenic effects on strength and power performance in recreationally active, young men. This novel information has implication for basic physiological understanding. Whether the same applies to an elite athlete population remains to be determined. If so, this would have implications for anti-doping efforts aiming to determine the most cost-efficient testing programs.
Highlights
Long-term testosterone administration has well-known physiological effects such as inducing skeletal muscle hypertrophy (Griggs et al, 1989), accelerated lipolysis, and associated reduction of total body fat (Rebuffé-Scrive et al, 1991), as well as accelerated erythropoiesis (Beggs et al, 2014)
Testosterone stimulation produces a rapid increase in intracellular Ca2+ concentration in cultured rat myotubes within seconds to minutes (Estrada et al, 2003) and promotes insulin-like effects in incubated human skeletal muscle cells (Antinozzi et al, 2017), while stimulation with dihydrotestosterone, a product of testosterone metabolism, increases force production in intact isolated mice skeletal muscle fibers (Hamdi and Mutungi, 2010)
The screening urine sample was analyzed according to the World Anti-Doping Agency (WADA) guidelines at the Norwegian Doping Control Laboratory, Oslo University Hospital, Oslo, which is accredited by WADA and Norwegian accreditation (ISO/IEC 17025)
Summary
Long-term testosterone administration has well-known physiological effects such as inducing skeletal muscle hypertrophy (Griggs et al, 1989), accelerated lipolysis, and associated reduction of total body fat (Rebuffé-Scrive et al, 1991), as well as accelerated erythropoiesis (Beggs et al, 2014). Short-term testosterone usage may have ergogenic effects, illustrated by increased maximal bench press strength and total work in a 10-s cycle sprint in nine healthy, weighttrained, young men following 3 weeks with intramuscular injections of 200–300 mg/week testosterone enanthate, but not placebo (PLA), combined with heavy strength training (Rogerson et al, 2007). Acute testosterone administration can potentially stimulate augmented maximal voluntary contraction (MVC) force production and affect muscle energy metabolism in humans. Interosseous dorsalis I motor responses to transcranial magnet stimulation in healthy males (Bonifazi et al, 2004). This facilitates the corticospinal pathway (Bonifazi et al, 2004) that, in turn, can influence muscle activity and lead to faster muscle activation, which potentially can contribute to increased
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