научная статья по теме ACUTE TESTOSTERONE AND CORTISOL RESPONSES TO HIGH POWER RESISTANCE EXERCISE Биология

Текст научной статьи на тему «ACUTE TESTOSTERONE AND CORTISOL RESPONSES TO HIGH POWER RESISTANCE EXERCISE»

ФИЗИОЛОГИЯ ЧЕЛОВЕКА, 2010, том 36, № 4, с. 102-106

УДК 612.821

ACUTE TESTOSTERONE AND CORTISOL RESPONSES TO HIGH POWER RESISTANCE EXERCISE © 2010 A. C. Fry1, C. A. Lohnes2

1 Applied Physiology Laboratory Department of Health, Sport & Exercise Sciences, University of Kansas 2 Locomotor Control Laboratory Program in Physical Therapy Washington University, St. Louis Received October 25.10.2009 г.

This study examined the acute hormonal responses to a single high power resistance exercise training session. Four weight trained men (X ± SD; age [yrs] = 24.5 ± 2.9; hgt [m] = 1.82 ± 0.05; BM [kg] = 96.9 ± 10.6; 1 RM barbell squat [kg] = 129.3 ± 17.4) participated as subjects in two randomly ordered sessions. During the lifting session, serum samples were collected pre- and 5 min post-exercise, and later analyzed for testosterone (Tes), cortisol (Cort), their ratio (Tes/Cort), and lactate (HLa). The lifting protocol was 10 x 5 speed squats at 70% of system mass (1 RM + BW) with 2 min inter-set rest intervals. Mean power and velocity were determined for each repetition using an external dynamometer. On the control day, the procedures and times (1600—1900 hrs) were identical except the subjects did not lift. Tes and Cort were analyzed via EIA. Mean ± SD power and velocity was 1377.1 ± 9.6 W and 0.79 ± 0.01 m •s-1 respectively for all repetitions, and did not decrease over the 10 sets (p < 0.05). Although not significant, post-exercise Tes exhibited a very large effect size (nmol • L-1; pre = 12.5 ± 2.9, post = 20.0 ± 3.9; Cohen's D = 1.27). No changes were observed for either Cort or the Tes/Cort ratio. HLa significantly increased post-exercise (mmol • L; pre = 1.00 ± 0.09, post = 4.85 ± 1.10). The exercise protocol resulted in no significant changes in Tes, Cort or the Tes/Cort ratio, although the Cohen's D value indicates a very large effect size for the Tes response. The acute increase for Tes is in agreement with previous reports that high power activities can elicit a Tes response. High power resistance exercise protocols such as the one used in the present study produce acute increases of Tes. These results indicate that high power resistance exercise can contribute to an anabolic hormonal response with this type of training, and may partially explain the muscle hypertrophy observed in athletes who routinely employ high power resistance exercise.

Key words: endocrine, squats, weight training.

Resistance exercise has been shown to induce an array of acute and chronic responses in human skeletal muscle. A potentially beneficial acute response is the effect of resistance exercise on circulating levels of both anabolic and catabolic hormones. For an individual seeking to improve strength and increase lean body mass, optimizing these endocrine responses appears to be a contributing factor [1]. Furthermore, the ratio of testosterone and cortisol has repeatedly been associated with the physiological stresses applied to the body [2—8]. While much has been elucidated concerning the acute resistance exercise variables and the associated endocrine responses, few data are available concerning the role of resistance exercise power and the immediate hormonal responses.

Resistance exercise has been shown to acutely increase circulating levels of total testosterone in adult males [1, 5, 7, 9—14]. Because some studies have shown no increase after resistance exercise [1, 9, 15], it is apparent that the response is dependent on a number of factors such as the amount of muscle mass involved [13], the intensity [11, 16, 17], volume [5], inter-set rest periods [7], age [10], and training experience [8]. Generally, protocols using large muscle

mass, multi-joint exercises with high relative intensities are effective for increasing acute testosterone concentrations [3-8, 10, 18-22].

Acute increases have also been demonstrated for cortisol [5, 6, 8, 16, 23, 24], although some investigations have found no response [13, 25, 26]. Although plasma volumes shifts certainly account for some of the resistance exercise-induced cortisol kinetics, circulating concentrations are influenced by numerous other factors [27]. While cortisol has been shown to acutely increase after large volumes of high power, large muscle mass exercises, the relative intensity must be great enough to elicit such a response [5, 6, 8, 12, 13, 17, 19, 21-24, 26, 28-30].

The acute effect of resistance exercise on the testosterone/cortisol (Tes/Cort) ratio is less clear. Increasing testosterone, decreasing cortisol, or both, would appear to result in a more anabolic environment for skeletal muscle. Typically, the acute hormonal response to a single resistance exercise training session is a relatively greater molar response of cortisol compared to testosterone. The net result is that the Tes/Cort ratio decreases immediately after most resistance exercise protocols [6, 27], although some studies

have failed to demonstrate acute changes in this ratio following resistance exercise [22]. On the other hand, high stress training by elite weightlifters has been shown to negatively affect this ratio at rest [3, 4, 18, 19, 28, 30], while well designed periodized programs are capable of increasing the Tes/Cort ratio [29].

While many studies have examined the acute hormonal response to resistance exercise, most investigations have focused on more traditional movements using heavy loads and relatively slow velocities. Few investigations to date have examined the effect of a high power training session incorporating lighter loads and higher velocities. Volek et al. [13, 26] found significant increases in circulating testosterone after jump squat sessions with a 30% 1 RM load. cortisol, however, did not exhibit an increase. In another study, testosterone and cortisol were increased in response to an acute bout of moderate to high intensity snatches, which would be considered a power exercise, in elite junior weightlifters [6]. However, when explosive resistance exercise was compared with sub-maximal and maximal load resistance exercise, testosterone was found to increase only when using the heaviest loads and slower velocities [17]. Because of the limited research regarding high power resistance exercise and hormonal responses, the purpose of this study was to examine the effect of a high power resistance training (HPRT) protocol on circulating levels of total testosterone, cortisol, and the Tes/Cort ratio.

METHODS

Subjects included trained men (n = 4, mean ± SD, age = 24.5 ± 2.9 years, weight = 96.9 ± 10.6 kg, height = = 182 ± 5 cm, 1 RM barbell squat = 129.3 ± 17.4 kg) who volunteered to participate in the study. At the onset of the study, all participants had been involved in a resistance training program for at least the past year and were capable of performing a 1 RM squat equal to 1.0 x body weight. Prior to participation, all subjects were informed of the protocols and risks associated with the study and signed informed consent documents approved by The University Institutional Review Board.

A randomized, repeated measures design was used to examine the acute effects of a high power resistance training (HPRT) session on serum concentrations of testosterone, cortisol and the Tes/Cort ratio. Each subject served has his or her own control, and the order of the sessions was randomized (see Fig. 1). Subjects reported to the lab on three separate occasions. The purpose of the first session was to brief the participants on the procedures and risks associated with the protocol, obtain written consent, determine barbell squat 1 RM, and familiarize participants with the speed squat movement. One RM strength for the parallel barbell squat was determined using the methods of Kraemer and Fry [31]. Subjects were required to reach a depth of parallel throughout the study, defined as the

Blood Draw

Blood Draw

1

WarmRest Up

High Power Resistance Exercise OR

No Exercise Rest

_i_i

I

0 15 20 55 60

Time, min

Fig. 1. Study time line.

posterior surface of the thigh being parallel with the floor. A high bar position (barbell on the superior aspect of the trapezius) was also used throughout the study. One RM strength was determined from the most weight that could be lifted one time using correct form. After determining 1 RM, familiarization consisted of 5 sets of 5 repetitions of speed squat with a load of 70%

1 RM system mass (1 RM barbell load + BM). Subjects were instructed to exert a maximal effort and to accelerate through the entire concentric portion of the speed squat. Verbal cues in regard to form, depth, and speed of movement were given throughout the familiarization session.

One week later, subjects returned for either the high power resistance training session (HPRT) or the control session (CON). The second session was performed

1 week later, with the order of the session conditions randomized. Subjects reported to the lab between 1600 h and 1900 h for both sessions to minimize any effects of diurnal variation on hormonal concentrations. On the HPRT day, subjects performed a general 5-minute warm-up before commencing the HPRT protocol. After warming up, 10 sets of 5 speed squat repetitions were performed using 70% of the system 1 RM mass. Two minutes of rest separated each set. Barbell velocity was measured for each repetition using a linear position transducer attached to the right side of the bar (Fitrodyne; Fitronics, Bratislava, Slovakia). Velocity was calculated as the first derivative of position with respect to time. When barbell velocity dropped below 90% for at least two repetitions of a set, the barbell weight was decreased 5 kg to permit barbell velocities to be maintained. As a result, speed of movement was maintained throughout all sets for all subjects. Force was calculated as the product of the system mass and acceleration due to gravity. Average power was calculated as the product of force and average velocity.

Serum hormonal and blood lactate response

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