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ARTICLE Hormonal responses after resistance exercise performed with maximum and submaximum movement velocities Ilias Smilios, Panagiotis Tsoukos, Andreas Zafeiridis, Apostolos Spassis, and Savvas P. Tokmakidis

Abstract: This study examined the effects of maximum and submaximum movement velocities after a muscular hypertrophy type resistance exercise protocol on testosterone, human growth hormone (hGH) and cortisol concentrations and on neuromuscular performance assessed with a vertical jump. Eleven males performed a control and 3 resistance exercise protocols (4 sets of squat and 4 sets of leg-press exercises, 8 repetitions/set, 10-repetition maximum load). The first exercise protocol was performed at maximum velocity (Vmax); the second at 70% of Vmax with equal training volume (70%VmaxEV) to Vmax; and the third at 70% of Vmax (70%Vmax) with a 10.6% higher training volume to Vmax. Testosterone and hGH increased after all exercise protocols (p < 0.05) compared with baseline and were higher versus control values (p < 0.05). Cortisol concentrations gradually decreased in 70%Vmax, 70%VmaxEV and control protocols following a typical circadian rhythm (p < 0.05), but remained relatively constant in Vmax protocol. Comparisons among protocols showed that hGH was higher in 70%Vmax versus Vmax (p < 0.05), while cortisol was higher in Vmax versus 70%VmaxEV and control (p < 0.05). The greatest reduction in vertical jump and increase in heart rate were observed after the Vmax protocol (p < 0.05). In conclusion, a hypertrophy type resistance exercise protocol performed at maximum movement velocity increases testosterone and hGH and generates a greater biological stress, as evident by a higher cortisol concentrations and heart rate responses, and a greater reduction in neuromuscular performance. A protocol, however, performed at submaximum movement velocity combined with greater training volume stimulates to a greater extent the hGH response with no effect on cortisol. Key words: testosterone, growth hormone, cortisol, vertical jump, strength training. Résumé : Cette étude analyse les effets sur la concentration de testostérone, l’hormone de croissance humaine (HCH) et de cortisol et sur la performance neuromusculaire au cours d’un saut vertical d’un mouvement exécuté a` vitesse maximale et sous-maximale a` la suite d’un protocole d’exercices contre résistance a` des fins d’hypertrophie musculaire. Onze hommes participent a` trois protocoles d’exercices et a` un protocole de contrôle (4 séries de flexion accroupie et 4 séries de développé des jambes, 8 répétitions/série, maximum en 10 répétitions). Le premier protocole d’exercices est accompli a` vélocité maximale (« Vmax »), le deuxième a` 70% de Vmax et a` volume égal a` Vmax (« 70%VmaxEV »), le troisième a` 70% de Vmax (70%Vmax) et avec 10,6% de plus de volume d’entraînement qu’a` Vmax. Les concentrations postexercice de testostérone et de GHS dans tous les protocoles sont plus grandes (p < 0,05) comparativement aux valeurs de base et au protocole de contrôle (p < 0,05). À la suite des protocoles a` 70%Vmax, a` 70%VmaxEV et de contrôle, les concentrations de cortisol diminuent graduellement selon un rythme circadien typique (p < 0,05), mais demeurent stables dans le protocole Vmax. Les comparaisons entre protocoles révèlent des valeurs plus élevées de HCH a` 70%Vmax comparativement a` Vmax (p < 0,05) et des valeurs plus élevées de cortisol a` Vmax comparativement a` 70%VmaxEV et au protocole de contrôle (p < 0,05). C’est a` la suite du protocole Vmax qu’on observe la plus grande diminution de la hauteur de saut vertical et la plus grande augmentation du rythme cardiaque (p < 0,05). En conclusion, effectuer a` vélocité maximale un protocole d’exercices contre résistance a` des fins d’hypertrophie suscite une augmentation des concentrations de testostérone et d’HCH et génère un plus grand stress biologique comme le révèlent la plus haute concentration de cortisol et la plus grande fréquence cardiaque ainsi que la plus grande diminution de la performance neuromusculaire. Toutefois, un protocole d’exercices effectués a` vélocité sous-maximale et a` plus grand volume d’entraînement stimule davantage la réponse de l’HCH sans répercussion sur le cortisol. [Traduit par la Rédaction] Mots-clés : testostérone, hormone de croissance, cortisol, saut vertical, entraînement a` la force.

Introduction Changes in hormonal concentrations following a resistanceexercise session contribute to the regulation of long-term neuromuscular adaptations (Hansen et al. 2001; Kvorning et al. 2006; Rønnestad et al. 2011). Most resistance-exercise studies have focused on changes in concentrations of testosterone, human growth hormone (hGH) and cortisol, which have been implicated in nerve and muscle tissue function, growth and metabolism as well as in regulation of inflammatory response (Bonifazi et al.

2004; Crewther et al. 2011; Herbst and Bhasin 2004; Liu et al. 2003; Miles 2005). There is a consensus that the hormonal responses to resistance exercise depend on protocol characteristics such as the amount of muscle mass activated, the exercise order, the load used, the number of repetitions per set, the number of sets per exercise, and the length of rest interval between sets (Ahtiainen et al. 2003; Kraemer et al. 1990; Migiano et al. 2010; Simao et al. 2013; Smilios et al. 2003). Alterations in one of the above parameters or in their configuration create a unique stimulus that

Received 10 April 2013. Accepted 29 September 2013. I. Smilios, P. Tsoukos, A. Spassis, and S.P. Tokmakidis. Department of Physical Education and Sport Science, Democritus University of Thrace, Komotini 69100, Greece. A. Zafeiridis. Department of Physical Education and Sport Science – Serres, Aristotle University of Thessaloniki, Agios Ioannis, Serres 62110, Greece. Corresponding author: Ilias Smilios (e-mail: [email protected]). Appl. Physiol. Nutr. Metab. 39: 351–357 (2014) dx.doi.org/10.1139/apnm-2013-0147

Published at www.nrcresearchpress.com/apnm on 2 October 2013.

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modifies the hormonal response. For example, an increase in the number of sets or a reduction in the rest interval may augment the testosterone, hGH and cortisol responses (Buresh et al. 2009; Kraemer et al. 1990; Smilios et al. 2003). Movement velocity is another parameter that may affect the biological stress of resistance training and thus, the neuromuscular adaptations. An increase in movement velocity is associated with higher heart rate (HR), blood lactate and energy expenditure, and an augmented disruption of muscle ultra-structure (Hunter et al. 2003; Mazzetti et al. 2007; Shepstone et al. 2005). Movement velocity during resistance exercise can range from low to maximum. The execution of a movement with maximum velocity augments the rate of force development and muscle electrical activity by lowering the activation threshold of the motor units (Carpentier et al. 1996; Desmedt and Godaux 1977). The greater muscle mass activated from the early stages of exercise and the increased rate of force development may in turn induce higher hormonal responses, through peripheral and neural mechanisms. If hormones, along with mechanical and other metabolic signals, contribute to the neuromuscular adaptations observed during resistance training, it would be interesting to know whether movement velocity (i.e., submaximum vs. maximum) during resistance exercise has an effect on hormonal response. The 2 studies that examined the effects of movement velocity on hormonal responses following resistance exercise reported reduced (Goto et al. 2008) or unchanged (Headley et al. 2011) testosterone, hGH and cortisol responses with faster compared with slower movements. Both studies, however, (i) employed only submaximal movement velocities during the execution of resistance exercises; (ii) used protocols that are not typically recommended for the development of muscle hypertrophy, regarding the combination of loads and the number of repetitions (i.e., loads 70%–85% of 1 repetition maximum (1RM), 6–12 repetitions per set, 2–6 sets per exercise, 1–3 min of rest between sets Ratamess et al. 2009); and (iii) applied the same absolute movement time for all subjects without adjusting for the subject’s maximal movement velocity and anatomical characteristics. The instruction to perform the same range of motion at a fixed time period (e.g., 2 s) to tall and short or to “fast” and “slow” individuals might not be appropriate, since the same movement might be performed at greater absolute and relative speeds by 1 subject than the other. The standardization of movement velocity to the maximum velocity that each person can achieve would normalize these differences and provide information for the effects of movement velocity per se on the hormonal response. Based on the above, the effects of movement velocity (submaximum vs. maximum) during a muscle hypertrophy protocol on hormonal responses have yet to be determined. This is despite the quest as to which movement velocity is more effective in inducing neuromuscular adaptation and the fact that muscular hypertrophy protocols are widely used for improving health, fitness, and sport performance. The knowledge on the effects of submaximum and maximum movement velocity on hormones that contribute to neuromuscular adaptations would provide valuable information for designing muscle hypertrophy protocols. Therefore, the aim of this study was to examine the effects of submaximum and maximum movement velocity during a hypertrophy type resistance exercise protocol on testosterone, hGH and cortisol responses as well as on neuromuscular performance.

Materials and methods Subjects Eleven males (age: 22.5 ± 3.3 years, height: 181 ± 5 cm, and body mass: 81.6 ± 5.6 kg) participated in the study. Before the initiation of the study, the institutional review board committee of Democritus University of Thrace approved the experimental protocol and all participants signed an informed consent form. The subjects were

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classified as moderately to well-trained individuals and had previous experience (6 months to 3 years) with resistance training. Their training regime included lifting moderate to heavy loads (50%–90% of the 1RM) for 2 to 3 times per week. All participants were healthy, free of medication, and did not receive any nutritional supplements. The subjects were instructed to maintain their regular diet and physical activity throughout the study and were requested to abstain from caffeine and alcohol consumption for 24 h, and avoid any physical activity for 48 h before testing. Study design Each subject performed 3 resistance exercise protocols and a resting control session. The resistance protocols consisted of 4 sets of squat and 4 sets of leg press exercises using a 10-repetition maximum (10RM) load with a 3-min rest between sets. The first protocol involved the execution of 8 repetitions per set using maximum movement velocity (Vmax). The set was terminated either when the required number of repetitions was completed or when the movement velocity fell below 85% of the maximum for 2 consecutive repetitions (all subjects were not able to complete the required number of repetitions at all sets with maximum velocity). In the second protocol, the participants performed the resistance exercises at 70% of maximum velocity with equal training volume (70%VmaxEV) to that in the Vmax (that is the same number of repetitions was completed and the same load was used in each set as in Vmax protocol). In the third protocol, the participants exercised at 70% of maximum velocity (70%Vmax) completing all 8 repetitions in all sets. The 70%Vmax protocol is regarded as a typical resistance training session that a person would perform for muscular hypertrophy regarding the intensity used and the number of sets and repetitions completed at each set. Finally, the participants were involved in a resting control protocol to account for the effects of circadian rhythm on hormonal concentrations. The Vmax, the 70%Vmax, and the control protocols were performed in random order using a counterbalanced design. The 70%VmaxEV was executed after the Vmax protocol (not always in sequential order) since it was necessary to know the number of repetitions performed at each set in the Vmax protocol. All 4 protocols were performed with 1 week intervals at the same time of the day for each subject. Five subjects started the sessions at 0930 h and 6 subjects at 1100 h. These times were kept constant for each subject (within a time period of 10 min) to avoid a diurnal effect. Serum testosterone, 22 kDa hGH, and cortisol concentrations were measured before, immediately after, and at 20 min and 40 min after the completion of the sessions. Vertical jump height was also measured at the same time points as an index of neuromuscular performance. Measurements 10RM load Three days before the exercise sessions, the 10RM load was determined in the parallel squat exercise (knee angle: 74.3 ± 5.2°) using a Smith machine and in the leg press exercise (knee angle: 75.3 ± 3°) using a 45° diagonal leg press machine. These exercises were selected because they activate large muscle groups of the lower limbs. Before the 10RM test, the subjects attained a squatting position, with their thighs parallel to the floor. The subjects maintained this position and the location of the barbell was marked on the sliding bars of the machine. Next, the subjects were asked to lower the foot plate during the leg press exercise until a similar knee angle to that in the parallel squat exercise was achieved and the position of the foot plate was marked. During the squat and leg press exercises the downward movement was controlled by metal stops that were placed on the previously marked points, while the upward movement was performed until the knees were fully-extended. For the 10RM load determination, the subjects performed initially 10 repetitions with a load perceived at 50%–60% of their 1RM. Published by NRC Research Press

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Afterwards, the loads increased progressively by 5–20 kg, every 4 min, until the subjects were not able to complete the 10 repetitions with full range of motion. Three to 4 sets were required to determine the 10RM load. Mechanical parameters The vertical displacement of the bar during the squat and the leg press exercises was measured as a function of time with a linear encoder (Ergotest Technology, Langesund, Norway) attached on the barbell with a cord. When the barbell was moved by the subjects, a signal was transmitted by the encoder, with a resolution of 0.075 mm, to an A/D converter (Muscle Lab, Ergotest Technology; sampling frequency 100 Hz) interfaced through a PC with software for data acquisition and analyses (MuscleLab version 6.07, Ergotest Technology). The external load was inserted in the software and the mechanical parameters of average velocity, force and power during movement were calculated. Based on total force and displacement data, total work with the execution of each exercise session was calculated. Visual and auditory signals guided the subjects during the execution of the exercises to produce the power output specific to the resistance exercise protocol performed at that day. Blood analyses Eight milliliters of blood were drawn at each sampling point in serum separator tubes, allowed to clot for 30 min and centrifuged at 1500g for 15 min (Hermle Z300K, Labortechnik GmbH, Germany). Serum was removed, separated into 250 ␮L aliquots and frozen at −80 °C for later analysis. Serum was analyzed (StatFax 2100, Awareness Technology Inc., Palm City, Fla., USA) by EMSAs (DRG Instruments GmbH, Germany) for testosterone, cortisol and hGH concentrations with assay sensitivities of 0.29 nmol·L−1, 6.9 nmol·L−1, and 0.5 ␮g·L−1 and intra-assay coefficient of variability of 3.7%, 5.1%, and 2.5%, respectively. The samples of each subject were analyzed in duplicate in the same run. Hormonal values are reported uncorrected for plasma volume changes, since tissues are exposed to absolute hormonal concentrations.

Experimental procedure The subjects reported in the laboratory after an overnight fast. They avoided caffeine and alcohol consumption for 24 h and did not perform physical exercise for 48 h before the experimental sessions. After resting for 15 min in the supine position, the first blood sample was drawn via an indwelling venous catheter placed into an antecubital vein. Before the start of the exercise sessions, the subjects performed a standardized warm-up, which included jogging and stretching exercises of the lower limbs. Next, the subjects executed a specific warm-up of 2 sets of 5 repetitions of squats with loads corresponding to 60% and 80% of the 10RM load, respectively, with a 3-min rest between sets. Afterwards, the subjects executed 3 repetitions of the leg press exercise, rested for 4 min and then performed 3 repetitions of the squat exercise. Both exercises were performed with maximum movement velocity to determine the maximum velocity of the day for each exercise (average of the 3 repetitions) with the 10RM load. This velocity was used to set the limits for termination of exercise in Vmax protocol (85% of Vmax) and for movement velocity in 70%VmaxEV and 70%Vmax protocols. After 4 min of rest, the participants executed 3 vertical jumps using a Vertek device as an index of neuromuscular performance of the lower limbs. Then, the experimental protocols began. The warm-up and the maximal velocity testing periods lasted approximately 25 min and the the Vmax, 70%VmaxEV, 70%Vmax, and control protocols lasted 34 ± 1, 35 ± 2, 34 ± 2 and 35 min, respectively. Thus, the total exercise session duration lasted 60 ± 3 min. During the resistance exercise sessions, the velocity of the eccentric part of the movement was chosen by the subjects and the velocity of the concentric part of the movement was specific to the

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resistance exercise session performed at that day (maximal or 70% of maximum). In the Vmax session, no subject was able to complete 8 repetitions with movement velocities above 85% of maximum in all 4 sets of the squat and the leg-press exercises. The average number of repetitions per set was 7.82 ± 0.28 (range: 7.25–8) for the squat exercise and 7.23 ± 0.68 (range: 6.25–8) for the leg-press exercise. In total, the subjects completed 60.18 ± 2.52 out of 64 repetitions (range: 55–63) in the Vmax protocol. During the leg press exercise, the load was decreased by 5% in 1 set for 2 subjects and in 2 sets for 1 subject. The load adjustments were performed to ensure the completion of at least 6 repetitions, which is the least amount of recommended repetitions for a hypertrophy type protocol (Ratamess et al. 2009), with a velocity above 85% of maximum. In the 70%VmaxEV session the subjects performed at each set the same number of repetitions with the same loads as in the Vmax session. In the 70%Vmax session all subjects completed 8 repetitions at all sets without load adjustments. During the training workouts and the recovery periods the subjects were allowed to drink water ad libitum. After the completion of resistance-exercise protocols blood samples were drawn immediately after exercise (within 1 min after the termination of exercise), as well as at 20 min and at 40 min of recovery. All blood samples were drawn with the subjects in the supine position. Vertical jump height was measured within 1 min after the blood sampling after the termination of exercise at the twentieth and fortieth minutes of recovery. HR was continuously monitored during the resistance exercise protocols (Polar RS400, Polar electro, Finland). The HR values recorded during the exercise phase in each set were averaged to obtain the mean HR value for the whole exercise protocol. During the control protocol the exact same procedure was followed with the exception that the subjects did not perform any exercise protocol but sat passively for 60 min. Statistical analyses All data are presented as means ± SD. The normality of distribution of the data was examined with the Shapiro–Wilks test and the homogeneity of variance assumption was not violated. A 1-way repeated measures ANOVA was used to examine the differences among protocols in training volume, total work, movement velocity and HR. A 2-way ANOVA with repeated measures on both factors was used to examine the interaction between exercise protocol (Vmax, 70%Vmax, 70%VmaxEV, control) and time point (before exercise, immediately after, 20 min after, and 40 min after exercise) on hormonal concentrations and vertical jump height. Significant differences between means were located with the Tukey HSD test. The level of significance was set at p < 0.05. The effect sizes were calculated using partial eta squared (␩p2) for ANOVAs and Cohen’s d (d = difference between means/pooled SD) for pairwise comparisons. The small, medium, and large effects would be reflected for ␩p2 in values greater than 0.0099, 0.0588, and 0.1379, respectively, and for Cohen’s d in values greater than 0.2, 0.5, and 0.8, respectively (Cohen 1988).

Results Training data The ANOVA indicated a significant effect of “protocol” for training volume (p < 0.05; ␩p2 = 0.61) and total work (p < 0.05; ␩p2 = 0.50). Pairwise comparisons showed that training volume (product of sets × repetitions × load) and total work were lower in the Vmax than in the 70%Vmax protocol by 10.6% ± 8.5% (p < 0.05, d = 0.37) and 13.4% ± 8.9%, (p < 0.05, d = 0.67; Table 1), respectively. By design, the training volume during the 70%VmaxEV protocol was adjusted to match the one attained in Vmax protocol. The ANOVA identified a significant effect of protocol for average movement velocity (p < 0.05; ␩p2 = 0.92). Pairwise comparisons showed that the average movement velocity was higher during Published by NRC Research Press

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Table 1. Mean ± SD values for average movement velocity of 4 sets in absolute values and as a percent of maximum, during the concentric and the eccentric phases of the squat and leg press exercises in the 3 resistance-exercise protocols. Vmax

70%VmaxEV

70%Vmax

Training volume (kg) Total work (J)

9781.4±2633.9 23720±5105

9781.4±2633.9 23225±5353

10742.9±2605.6† 27048±6157†

Movement velocity (m/s) Squat concentric Squat eccentric Leg press concentric Leg press eccentric

0.56±0.07 0.41±0.11 0.44±0.07 0.32±0.09

0.43±0.07* 0.35±0.07* 0.37±0.06* 0.29±0.06

0.44±0.06* 0.35±0.05* 0.36±0.07* 0.29±0.08

69.24±2.71* 67.98±2.76*

75.56±6.22* 71.93±5.67*

Movement velocity (%max) Squat concentric 98.31±7.1 Leg press concentric 92.9±8.09

Note: *p < 0.05 vs. Vmax; †p < 0.05 vs. Vmax and 70%VmaxEV. Vmax, maximum movement velocity protocol; 70%VmaxEV, 70% of maximum velocity with equal training volume to Vmax protocol; 70%Vmax, 70% of maximum movement velocity protocol.

the Vmax protocol (95.61% ± 6.81% of maximum velocity) than in the 70%VmaxEV (68.61 ± 2.17% of maximum velocity p < 0.05, d = 5.34) and the 70%Vmax protocol (73.74 ± 5.67% of maximum velocity; p < 0.05, d = 3.49; Table 1). HR differed significantly among protocols (p < 0.05, ␩p2 = 0.62). Pairwise comparisons revealed that mean HR was significantly higher in Vmax versus 70%Vmax and 70%VmaxEV (145.42 ± 17.28 vs. 137.43 ± 21.21 and 127.2 ± 22.81 beats·min−1, respectively; p < 0.05; d = 0.41 and 0.90, respectively) and higher in 70%Vmax versus 70%VmaxEV (p < 0.05; d = 0.46). Hormonal responses The ANOVA revealed a significant main effect of “time” (p < 0.05, ␩2p = 0.64) and a significant “protocol × time” interaction (p < 0.05, ␩2p = 0.34) on testosterone concentrations. Testosterone concentration increased immediately after exercise and remained elevated at 20 min postexercise in all exercise protocols compared with the respective baseline values (p < 0.05; Vmax: d = 0.57–1.08, 70%VmaxEV: d = 0.43–0.80, 70%Vmax: d = 0.62–1.21). During the control session the testosterone levels remained relatively constant. Pairwise comparisons between protocols revealed that testosterone concentrations immediately postexercise were higher in all exercise protocols versus the respective control value (p < 0.05; d = 0.71–0.84). At 20 min postexercise, testosterone concentrations remained significantly higher in Vmax and Vmax70%EV compared with those in the control session (p < 0.05; d = 0.45). No differences were observed among the exercise sessions in testosterone concentration at any time point (p > 0.05; d = 0.06–0.33; Fig. 1A). The ANOVA revealed significant main effects of protocol (p < 0.05, ␩p2 = 0.28) and “time” (p < 0.05, ␩p2 = 0.73) as well as a significant protocol × time interaction (p < 0.05, ␩p2 = 0.34) on hGH concentrations. hGH increased immediately postexercise and remained elevated at 20 min postexercise in all 3 exercise protocols compared with the baseline concentration (p < 0.05; Vmax: d = 1.03–1.4, 70%VmaxEV: d = 0.95–1.2, 70%Vmax: d = 1.43–1.45). At 40 min postexercise, hGH returned to baseline values in Vmax, but remained elevated versus baseline in 70%VmaxEV (p < 0.05; d = 0.54) and the 70%Vmax protocols (p < 0.05; d = 1.08). hGH did not change in the control session. Comparisons among protocols revealed that hGH concentrations immediately after exercise and at 20 min postexercise were higher in all exercise protocols versus the respective values in control (p < 0.05; d = 0.85–1.19). Furthermore, immediately postexercise, hGH was higher in 70%Vmax versus Vmax (p < 0.05; d = 0.36; Fig. 1B). The ANOVA revealed significant main effects of protocol (p < 0.05, ␩p2 = 0.33) and time (p < 0.05, ␩2 = 0.55), and a significant protocol × time interaction (p < 0.05, ␩p2 = 0.25) on cortisol concentrations. Cortisol concentrations gradually decreased in 70%Vmax,

70%VmaxEV and control protocols following the circadian rhythm (p < 0.05; 70%Vmax: d = 0.45–0.71, 70%VmaxEV: d = 0.65–0.98, control: d = 0.87–1.39), while remained constant in the Vmax protocol (p > 0.05, d = 0.05–0.27). Cortisol concentrations after the Vmax protocol were higher at all postexercise time points compared with the respective once in the 70%VmaxEV and the control protocols (p < 0.05; d = 0.48–0.88) and at 20 min postexercise compared with that in the 70%Vmax protocol (p < 0.05; d = 0.63; Fig. 1C). Vertical jump The ANOVA revealed significant main effects of protocol (p < 0.05, ␩p2 = 0.35) and time (p < 0.05, ␩p2 = 0.78), and a significant protocol × time interaction (p < 0.05, ␩p2 = 0.23) on vertical jump height. Vertical jump decreased immediately after all exercise protocols and remained lower at 40 min postexercise compared with baseline values (p < 0.05; Vmax: d = 0.51–0.6, 70%VmaxEV: d = 0.23–0.26, 70%Vmax: d = 0.18–0.38). Vertical jump performance did not change throughout the control session. Comparisons among protocols showed that before exercise, vertical jump height was higher in Vmax and 70%VmaxEV versus 70%Vmax and control protocols (p < 0.05; d = 0.17–0.26). Immediately postexercise, and at 20 and 40 min postexercise, the vertical jump was lower in Vmax and 70%Vmax versus 70%VmaxEV and control (p < 0.05; d = 0.24–0.35; Fig. 2A). Because of significant differences in baseline values of vertical jump, the postexercise data were analyzed as a percent change from baseline. The ANOVA revealed a significant main effect of protocol (p < 0.05; ␩p2 = 0.43): that is vertical jump decreased significantly more in Vmax versus 70%VmaxEV, 70%Vmax, and control irrespective of the time point examined (p < 0.05; d = 0.93–2.25; Fig. 2B).

Discussion The main findings of this study were that a muscular hypertrophy resistance exercise protocol performed at Vmax increases testosterone and hGH responses to a similar extent as when the protocol is executed at submaximum velocity with equal training volume (70%VmaxEV). It should be pointed out, however, that the performance of the protocol with submaximum velocity and slightly greater training volume (70%Vmax) increases more hGH concentration and does not alter cortisol concentrations. Movement velocity affects the physiological responses during the execution of a resistance-exercise protocol (Hunter et al. 2003; Mazzetti et al. 2007; Shepstone et al. 2005). To the best of our knowledge, this the first study that normalized the movement velocity to the individual’s maximum speed. All previous studies used a fixed time period (e.g., 1, 3 or 5 s) for the execution of each repetition. However, this might not be appropriate for subjects with different anatomical and performance characteristics, since Published by NRC Research Press

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Fig. 1. Mean ± SD concentrations for testosterone (A), growth hormone (B), and cortisol (C) before, immediately after, and at 20 min and 40 min after exercise in a control session and in 3 muscular hypertrophy resistance exercise protocols performed at maximal movement velocity (Vmax) at 70% of maximal movement velocity with equal training volume (70%VmaxEV) to Vmax protocol, and at 70% of maximal velocity (70%Vmax). a, p < 0.05 vs. respective before exercise value; b, p < 0.05 vs. respective value in control; c, p < 0.05 vs. respective value in Vmax; d, p < 0.05 vs. respective value in 70%VmaxEV; e, p < 0.05 vs. respective value in 70%Vmax.

Fig. 2. Mean ± SD for absolute vertical jump height values before, immediately after, and at 20 min and 40 min after exercise (A) and as % change values from “before exercise” (B) in a control and in 3 muscular hypertrophy resistance exercise protocols performed at maximal movement velocity (Vmax), at 70% of maximal movement velocity with equal training volume (70%VmaxEV) to Vmax protocol, and at 70% of maximal velocity (70%Vmax). *, Significant main effect of protocol (Vmax < 70%VmaxEV, 70%Vmax, control; p < 0.05); a, p < 0.05 vs. respective before exercise value; c, p < 0.05 vs. respective value in Vmax; e, p < 0.05 vs. respective value in 70%Vmax.

the same movement at the same time (e.g., 2 s) might be performed at different velocities. Therefore, the method used to define training velocity may affect the physiological responses caused by an exercise session. The application of the protocol based on the individual’s maximum velocity requires specific equipment and continuous monitoring during the execution of the exercises. Although this could be difficult to apply on a daily basis, it might optimize adaptations and should be taken into consideration for highly trained individuals. It would be of scientific and practical importance for a proper training program design to examine if fixed time movements or individualized velocities, based on each

subject’s maximum, may differentiate the physiological stress during resistance exercise. The results of this study showed that in hypertrophy-type resistance exercise executed with maximum velocity cortisol concentrations remained unchanged, while in protocols performed at submaximum velocities cortisol concentration decreased in accordance with a circadian rhythm (control session). In previously published studies, Headley et al. (2011) did not observe any effect of movement velocity on cortisol responses when only the velocity of the eccentric phase of the movement was modified (2 s the concentric phase and 2 s the eccentric (2:2) vs. 2:4) using loads 55%–75% of 1RM. In contrast, Goto et al. (2008) found a higher cortisol increase during the resistance exercise performed with slower velocity (3:3) than with the faster (1:1) using a low load (40% of 1RM). The differences in the results between previous studies and this study could be collectively attributed to different loads (low to submaximal loads in previous studies vs. only submaximal loads in our study) and velocities (fixed velocities vs. percent of maximum velocity in our study) used, as well as to the modification of the movement velocity at different phases of contraction (eccentric vs. concentric in our study). Cortisol, as a stress hormone, increases more after the execution of higher volume protocols combined with high metabolic stress, as compared with lower volume protocols (Crewther et al. 2011; McCaulley et al. Published by NRC Research Press

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2009; Smilios et al. 2003). In this study cortisol concentrations were higher after the Vmax protocol, which also caused the highest neuromuscular stress, as evident by the greatest reduction in neuromuscular performance. In any case, the use of cortisol as an index of stress and overall training adaptation to resistance training requires further investigation. In agreement with previous studies, testosterone concentration increased following all 3 muscular hypertrophy protocols (Kraemer et al. 1990; McCaulley et al. 2009; Rønnestad et al. 2011). However, testosterone responses were similar between maximum and submaximum movement velocities. It appears that the velocity of movement does not affect testosterone response in a hypertrophy resistance exercise protocol. Probably the hypophysis–pituitary– gonadal axis and the newly proposed hypophysis–gonadal axis (Lee et al. 2002), which regulates testosterone concentration, are similarly activated at both velocities. In agreement with the present study, Headley et al. (2011) did not find any differences in testosterone and hGH responses when only the velocity of the eccentric phase of the movement was modified. In contrast, Goto et al. (2008) found greater testosterone and hGH responses with the slower movement (3:3 vs. 1:1). The differences in the loads employed (40% of the 1RM vs. 10RM in our study), the method used to control the movement velocity (fixed movement time vs. individualized velocity as a percent of maximum in our study), and the control of the velocity of either both or 1 phase of the movement (concentric and eccentric vs. only the concentric phase of the movement in our study) may explain the discrepancies in Goto’s and our results. The greater hGH response in this study was observed with the 70%Vmax session where the subjects exercised with a higher training volume (by 10.6% than in the Vmax session). Therefore, it appears that a higher training volume favors a greater hGH response. Similarly, previous studies have shown greater hGH responses in high volume as compared with low volume protocols or when the training volume and the metabolic requirements were increased by the number of sets performed in a specific protocol (Gotshalk et al. 1997; Smilios et al. 2003). It appears that within the range of the velocities examined in this study, hGH responses are more sensitive to the total work produced than to the rate of work production. These results are well supported by our study in the absence of differences in hGH responses between Vmax and 70%VmaxEV that differ in movement velocity but not in training volume. Metabolic requirements should be greater with increased training volume. Therefore, the significantly greater hGH response in 70%Vmax versus Vmax show that greater metabolic requirements, which are due to increased training volume, may provide a stronger stimulus for hGH secretion than the neural stimulus from muscle afferents that should be greater with maximum movement velocities (Godfrey et al. 2003). hGH concentrations remained elevated at 40 min following the execution of protocols with submaximal velocity compared with baseline values, but not, though, compared with corresponding control session values. Whether the movement velocity affects the time that hGH remains elevated following resistance exercise is an interesting topic, which pertains to potential differences in adaptations and requires further study. In the present study we did not find any differences in the magnitude of changes in testosterone and hGH concentrations between the maximum and the submaximum (70% of maximum) movement velocities when the training volume was matched, while cortisol concentrations appear higher when we applied the maximum velocity. In our study, the concentric movement time ranged from 0.6 to 1.2 s and the eccentric from 0.6–1.4 s, which are considered as a fast movement (Ratamess et al. 2009). Other studies have used slower movements (≥3 s) to examine the acute and chronic effects of resistance training on physiological and physical performance parameters (Hunter et al. 2003; Munn et al. 2005). Considering the roles of movement velocity and hormones on

Appl. Physiol. Nutr. Metab. Vol. 39, 2014

neuromuscular functions and adaptations, it would be of scientific and practical interest to examine hormonal responses after the execution of hypertrophy protocols with slower submaximum velocities, i.e., 50%, 25% or even 10% of maximum. In addition, how hormonal responses compare between fixed velocities of movement and a velocity chosen freely by the subjects is not known. The individuality of movement velocity may further expand our perspective of how this parameter affects hormonal concentrations during resistance exercise. In any case, hormonal concentrations are one of the endocrine factors that may be involved in regulation of training adaptation. Other factors such as hormonal clearance rates, hormone degradation, receptor binding protein activation and regulation should also be examined to gain more insight on the effects of movement velocity during resistance exercise on endocrine function, and consequently on tissue recovery and remodeling. It should be mentioned, however, that the endocrine function is one of the mechanisms that regulate tissue adaptations with resistance training. Studies have observed neuromuscular adaptations in the absence exercise induced increases in hormonal concentrations, suggesting that muscular hypertrophy and strength increases are due to local muscular factors (West et al. 2010; Wilkinson et al. 2006). However, other studies have shown reduced strength and muscle mass increases under conditions of either reduced systemic hormonal concentrations or with the absence of exercise-induced hormonal responses (Hansen et al. 2001; Inoue et al. 1994; Kvorning et al. 2006; Rønnestad et al. 2011). Differences in the size of the muscles examined, the structure of the training programs, and the experimental approach used may explain the discrepancy in the results. In any case, our belief is that endocrine function is one of the mechanisms involved in tissue adaptations with exercise and along with other systemic and intramuscular mechanisms regulates tissue function and adaptation. Most previous studies that employed a hypertrophy-type resistanceexercise protocol with relatively similar configuration that were used in this study have demonstrated increases in testosterone, hGH and cortisol concentrations. The magnitude of the increases depended on the muscle mass activated, the exercise order, the rest interval length, the number of repetitions per set, and the number of sets per exercise (Ahtiainen et al. 2003; Buresh et al. 2009; Kraemer et al. 1990, Migiano et al. 2010; Simão et al. 2013; Smilios et al. 2003). Our study makes a step forward examining the effect of movement velocity on the magnitude of response. During a hypertrophy type protocol, the execution of exercises with either maximum or submaximum movement velocity causes similar, moderate to large, increases of testosterone and hGh concentrations at velocities 70%–100% of maximum. Cortisol, on the other hand, decreased following a typical circadian rhythm, when the repetitions were performed at submaximum movement velocity. It should be noted, however, that our subjects were accustomed to resistance training and this may have affected cortisol response. Previous studies (Kraemer et al. 1999; Cadore et al. 2008) have shown a reduced cortisol response to hypertrophy protocols in trained compared with untrained individuals or following a resistance-training period. It is possible that trained individuals may need a stronger stimulus (i.e., increased movement velocity or volume) to achieve greater cortisol response. Indeed, in the present study, cortisol levels remained at moderately higher levels when repetitions were performed with maximal movement velocity compared with those with submaximum velocity. Thus, results from studies with untrained individuals should not be extrapolated to trained participants and vice versa. It should be mentioned that during the Vmax protocol the subjects were not able to maintain maximum movement velocity levels at all repetitions although they were exerting maximum effort. For example, the average velocity during the leg press exercise was at 93% of maximum (Table 1). This may limit our conclusion for the effects of “maximum velocity” on hormonal Published by NRC Research Press

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Smilios et al.

responses. Still, movement velocity was very close to maximum levels (i.e., >95% of maximum velocity). In conclusion, maximum movement velocity during a muscular hypertrophy resistance exercise protocol increases testosterone and hGH, and maintains higher cortisol levels compared with protocols with submaximum movement velocity in subjects accustomed to resistance training. At submaximum movement velocities (70% of maximum), the 2 primary anabolic hormones, testosterone and hGH, increased, while cortisol that inhibits protein synthesis did not change. Therefore, submaximum velocity movements appear to create different physiological conditions for muscular adaptations. Nevertheless, the greater biological stress, as evident by cortisol concentrations, increased heart rate response and greater reduction in neuromuscular performance, imposed by maximum movement velocity during a muscular hypertrophy protocol may activate other systemic mechanisms providing muscular adaptations through alternative pathways.

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Hormonal responses after resistance exercise performed with maximum and submaximum movement velocities.

This study examined the effects of maximum and submaximum movement velocities after a muscular hypertrophy type resistance exercise protocol on testos...
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