Journal of Strength and Conditioning Research, 2005, 19(1), 6–8

q 2005 National Strength & Conditioning Association

PRECONDITIONING OF THE PERFORMANCE IN POWER

EVENTS BY ENDOGENOUS TESTOSTERONE: in memory of professor Carmelo Bosco

ATKO VIRU1 AND MEHIS VIRU2

1Institute of Exercise Biology and 2Institute of Sports Pedagogy, University of Tartu, Estonia.

Prove convincenti sono state ottenute che il testosterone è un potente induttore della sintesi di proteine contrattili nei muscoli scheletrici. Nella formazione, il ruolo del testosterone endogeno è un amplificatore dell’azione induttrice dei metaboliti accumulati durante gli esercizi di resistenza (RT). Pertanto, il testosterone è essenziale per ipertrofia miofibrillare (vedi 13, 24, 37). La maggior parte delle prove emerse  per questa esclusione dell’ Ipertrofia muscolare da training specifico si basano sul blocco farmacologico del recettore cellulare specifico del testosterone (22). Tuttavia, i dati ottenuti da Bosco e dei suoi collaboratori ha mostrato che la performance degli atleti sui test di potenza muscolare si correla con il loro livello sanguigno di testosterone. In professionisti giocatori di calcio l’altezza del salto con cotromovimento  è positivamente correlato con livello basale del testosterone nel sangue (11). La relazione specifica tra testosterone e il livello della forza esplosiva dei muscoli delle gambe erano supportato dal fatto che la resistenza aerobica, determinata dal test di 12 minuti di Cooper, ha mostrato una correlazione negativa con il livello di testosterone (11). Comparazioni tra i livelli di testosterone della mattina e le concentrazioni sono più alte, e l’ascesa del centro di gravità nel test jump con contromovimento  in 97   atleti di alto livello indicano i valori più alti del test  sono  degli sprinters, il valori più bassi di questi parametri negli sciatori di fondo, e valori intermedi nei giocatori di calcio (12). In conformità, Kraemer et al. (25) segnalano una correlazione positiva tra livello di testosterone e esercizi di estensione a doppio ginocchio. Sono state trovate anche correlazioni significative tra Potenza media e potenza  altezza media di salto durante un salto continuo per 60 secondi ed un  cambio della concentrazione nel sangue  sangue del  testosterone durante questo test (10). È impossibile presumere che alcuni secondi siano abbastanza da attivare la secrezione di un ormone, per il trasporto la quantità aumentata di un ormone a un muscolo di lavoro, e per attualizzare l’effetto metabolico di questo ormone. Tuttavia, la performance della concorrenza è preceduta dal riscaldamento su. Gli atleti sono influenzati dal  stato anticipatorio. Durante la competizione, ogni atleta può utilizzare 3 o 6 prove. Quindi, gli esercizi in competizioni di potenza vengono eseguiti con  livelli di ormone alterati nel sangue. Il significato di queste alterazioni ormonali per le prestazioni dipende dal tempo richiesto per l’attualizzazione degli effetti sul metabolismo di questi ormoni. Gli ormoni che sono legati sulla membrana cellulare e agiscono attraverso la formazione di Adenosina-monofosfato ciclico  AMPc.(ad esempio, catecolammina) hanno bisogno solo di un paio di secondi per evocare effetti sul metabolismo. Gli ormoni che si legano ai recettori specifici nel citoplasma e agiscono attraverso l’induzione della proteina di sintesi (ad esempio, testosterone e altri ormoni steroidi) richiedono in diversi casi più di 1 ora per mostrare effetti metabolici. Di conseguenza, la performance negli esercizi di tipo esplosivo di potenza può essere influenzato solo da cambiamenti ormonali prima delle prestazioni principali. Questi cambiamenti ormonali contribuiscono alle precondizioni dell’all’azione. Lo scopo del presente editoriale è di puntare l’attenzione sull’ipotesi del precondizionamento, esplorando il significato del testosterone per le prestazioni negli eventi di potenza. L’ipotesi precondizionata presuppone che nell’individuo il tasso di produzione del testosterone sia in relazione causale con (a) lo sviluppo di fibre muscolari a contrazione rapida (FT),  (b) funzionamento delle unità motorie veloci. Pertanto, 2 tipi di precondizionamento nelle prestazioni negli eventi di potenza sono correlati al testosterone endogeno. Il precondizionamento a lungo termine è legato all’influenza del testosterone sullo sviluppo dei muscoli FT. Principalmente, è correlato a il periodo di pubertale. Il precondizionamento a breve termine dovrebbe essere correlato all’influenza del testosterone sul sistema nervoso centrale. Il risultato vede “girare” nel sistema nervoso centrale il motore per prestazione di tipo esplosivo

Long-Term Preconditioning.

Results of several studies provide evidence that explosive contractile activity of

muscles (jumping, sprinting, etc.) is related to the percentage

of FT fibers in leg muscles (9, 15, 20). Thus, the

capacity for muscular activities of explosive type depends

on development of FT fiber and fast motor units. Results

of other studies indicate that testosterone is responsible

for improved anaerobic enzyme systems and structural

development of FT fibers in muscles. Bass et al. (4) established

that in the temporalis muscle of the guinea pig,

sexual differentiation of the enzyme pattern is related to

testosterone. Dux et al. (16) demonstrated that pubertal

castration alters the structure of skeletal muscle; the development

of FT muscles suffers most of all. Krotiewski

et al. (26) confirmed castration effects in male rats. Testosterone

substitution restored development of FT muscles

in male castrates. According to these results, it is

possible to assume that during puberty, interindividual

differences in testosterone production rate are decisive for

the formation and development of FT fibers.

Several studies in male adolescents support this assumption.

Already at the onset of puberty (in 11- to 12-

year-old boys), the area of FT fibers as well as blood lactate

level after 15 seconds of all-out exercise correlated

significantly with testosterone level (31). In circumpubertal

boys testosterone levels in blood or saliva correlated

with maximal anaerobic power (19, 32), maximal power

output in incremental exercise (18), blood lactate level after

Wingate test (32), and maximal voluntary strength

(31). Bosco (7) indicated that in the age period between

8.5 and 14.5 years the rise of the center of gravity in the

countermovement jump increases linearly in children of

both genders. From the age of 14.5 years differentiation

of boys appeared. At this age there is typically a pronounced

increase in blood testosterone concentration.

Thus in the pubertal period, enhanced rate of increase

of testosterone concentration in blood obviously favors the

development of a phenotype characterized by high testosterone

level and effective performance in exercise of explosive

application of forces.

Inherent high levels of testosterone may enhance

myofibrillar hypertrophy in resistance training. However,

in power events even more important is the possible influence

of high testosterone levels on central nervous

structures. In early postnatal life certain neurons of the

central nervous system become sensitive to steroids, for

example, the spinal nucleus of the bulbocavernosus becomes

highly androgen sensitive. In adulthood testosterone

regulates both the size of motoneurons of the spinal

nucleus of bulbocavernosus and the related muscle (1, 27,

28). This neuromuscular subsystem plays an important

role in male copulatory behavior. There is still no evidence

that testosterone influences the neural adaptations

in strength training, including the adjustments at the level

of spinal motoneurons. Nevertheless, data have been

collected suggesting that androgens are able to influence

structure of neurons, including dendritic branching and

synapse formation in the adult brain (2, 29). Testosterone

also influences the regenerative properties of injured cranial

motoneurons (23). The contribution of testosterone in

training-induced long-term neural adaptivity waits investigation.

Short-Term Preconditioning.

Another way of understanding

the significance of testosterone in power exercises

is the short-term preconditioning effect. Testosterone

is known to play a role in preconditioning of aggressive

behavior (34, 35). By analogy, it is possible to assume

that testosterone promotes changes in neurons that are

related not only to increased aggressiveness but also to

mobilization of neuromuscular capacity for explosive performance

in power events.

A study of a sample of normal male adolescents (15 to

17 years old) showed that a positive relationship exists

between circulating plasma testosterone levels and certain

forms of aggressive behavior (34). To extend this

study, the same team investigated another contingent of

58 healthy boys. Results suggested that circulating levels

of testosterone in the blood had a direct causal influence

on provoked aggressive behavior. A high level of testosterone

was related to readiness to respond vigorously and

assertively to provocations and threats. High levels of testosterone

made the boys more impatient and irritable,

which in turn increased their propensity to engage in aggressive-

destructive behavior (35). Results also indicated

the possibility that the testosterone effect is a permissive

one and that the sensitivity of the central nervous system

to testosterone varies interindividually (33). Castration of

adult male mice resulted in the decrease of aggressive

behavior, which was restored after testosterone replacement

(3). Experiments on rodents also showed that a differential

degree of local conversion of testosterone to estradiol

by the enzyme aromatase in the brain preoptic

area might be involved in the expression of aggressive

behavior (14).

In male sprinters after a hard training session, power

output in full squats and half squats was significantly

decreased and the ratio of electromyogram to power increased,

indicating fatigue. These changes were associated

with a decrease in the testosterone concentration in

blood (8). The developing fatigue might simultaneously

and independently impair neuromuscular function and

suppress testosterone production. However, the possibility

that the cause of impaired neuromuscular function

was a decreased testosterone level cannot be excluded.

Accordingly, the neuromuscular function may have been

impaired because of the lack of necessary preconditioning

by testosterone.

Elias (17) and Booth et al. (6) showed that during

sports competition in judo or tennis, winners have higher

levels of testosterone than losers. Therefore, Mazur and

Booth (30) suggested that testosterone prepared winners

for more effective performance.

On the background of extended experimental material,

Ingle (21) affirmed that the permissive effect of hormones

consists in making the changes in body function

or metabolic processes possible even though the hormone

itself is not the direct cause of the change. The supposed

permissive action of testosterone is obviously related to

the indirect effect of testosterone, which is actualized

without participation of androgen receptor (36). The manifestations

of the indirect effect of testosterone are the

production of insulin-like growth factor 1, competition for

the specific binding sites for glucocorticoids, autocrine release

of andromedins, transmembrane influx of extracellular

calcium, and activation of extracellular signal-related

kinase cascade via binding to a yet-unidentified extracellular

receptor (5).

Conclusion.

The hypothesis of preconditioning of performance

in power events by endogenous testosterone

opens a wide spectrum of tasks for further research. The

perspectives include testing various aspects of the hypothesis

as well as deep investigations in order to establish

the cellular-metabolic foundations of testosterone actions

on nervous structures and muscle fibers of various

types related to power performance.

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