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The Salivary Testosterone and Cortisol Response to Three Loading Schemes

Crewther, Blair1,2; Cronin, John2,3; Keogh, Justin2; Cook, Christian1

Journal of Strength and Conditioning Research: January 2008 - Volume 22 - Issue 1 - p 250-255
doi: 10.1519/JSC.0b013e31815f5f91
Original Research
Free

This aim of this study was to examine the free hormone (in saliva) responses to squat workouts performed by recreationally weight-trained males, using either a power (8 sets of 6 reps, 45% 1 repetition maximum [1RM], 3-minute rest periods, ballistic movements), hypertrophy (10 sets of 10 reps, 75% 1RM, 2-minute rest periods, controlled movements), or maximal strength scheme (6 sets of 4 reps, 88% 1RM, 4-minute rest periods, explosive intent). To determine the relative importance of the different training variables, these schemes were equated by workout duration with the power and strength schemes also equated by load volume. Salivary testosterone (T) and cortisol (C) both increased following the hypertrophy scheme (P < 0.05), with little to no hormonal change across the power and maximal strength schemes (P > 0.05). In general, the postexercise T and C responses to the hypertrophy scheme exceeded the other two schemes (P < 0.05). The greater volume of load lifted in the hypertrophy protocol over the same workout duration may explain the endocrine differences observed. The similar T and C responses to the power and maximal strength schemes (of equal volume) support such a view and suggest that differences in load intensity, rest periods, and technique are secondary to volume. Because the acute hormonal responses to resistance exercise contribute to protein metabolism, then load volume may be the most important workout variable activating the endocrine system and stimulating muscle growth.

1Health and Food Group, Hort Research, Auckland, New Zealand; 2Institute of Sport and Recreation Research New Zealand, School of Sport and Recreation, Auckland University of Technology, Auckland, New Zealand; 3School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Perth, Australia

Address correspondence to Blair Crewther, BCrewther@Hortresearch.co.nz.

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Introduction

The acute testosterone (T) and cortisol (C) responses to resistance exercise play an important role in protein metabolism during the recovery period (6,11). The configuration of the various workout variables (e.g., load intensity, rest periods, technique, volume) or lifting scheme design is therefore critical to activating the endocrine system and stimulating those cellular processes that underpin muscle tissue growth. For example, muscle building or hypertrophy schemes increase T and C concentrations, whereas lifting schemes designed to maximize muscular strength, rather than muscle size, produce little to no endocrine change (4,8,21,26). Similar to maximal strength schemes, power schemes produce only modest changes in the circulating levels of these hormones (12,14,19,25). Although the hormonal responses to these lifting methods (power, hypertrophy, and maximal strength) have been widely investigated, direct comparisons between all three are scarce. Given the importance of scheme design to the acute hormonal environment, it would also be of interest to equate these schemes in some manner (e.g., load lifted, workout duration) to determine the relative contribution of the different workout variables.

Saliva is a biological medium developing greater acceptance as a method for steroid hormone determination. Salivary hormones accurately reflect the free (unbound) hormone in the blood and are of comparable concentrations (22-24), thereby providing valuable measurements of endocrine function (i.e., biologically active hormone). The noninvasive nature of saliva collection also eliminates stress responses associated with blood collection techniques (e.g., venipuncture), reducing hormone shifts and enabling greater ease in multiple sample collection. Our understanding of the steroid hormone responses to resistance exercise are, by and large, based on the blood measurement of the hormone fractions bound to specific and nonspecific carrier proteins, collectively termed the total hormone. Examining the free hormone response to resistance exercise, via saliva, would provide physiologically relevant data, particularly when you consider that the free (vs. total) hormone exhibits a more dynamic response to intense exercise (3,20). Saliva-based hormone measurement therefore provides several benefits that may enable scientists and practitioners to develop a better understanding of the hormone responses to exercise.

Addressing the aforementioned issues (e.g., scheme comparison, equating schemes, free hormone examination) would provide greater insight regarding the responsiveness of the endocrine system to resistance exercise and subsequent adaptation. The main purpose of this study was to investigate the free hormone (in saliva) responses to three different loading schemes: (a) power, (b) hypertrophy, and (c) maximal strength. These schemes were equated by workout duration with the power and maximal strength schemes also equated by load volume (total reps × load intensity). Given the importance of load volume to those stressors (e.g., total forces, total work) imposed by resistance exercise (1), it was hypothesized that the salivary T and C responses would be proportional to the volume of load lifted in each scheme.

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Methods

Experimental Approach to the Problem

The acute hormonal environment afforded by resistance exercise is related to protein metabolism in the recovery period and differs according to scheme design. Despite the biological importance of the free hormone, our understanding of the endocrine responses to resistance exercise are, by and large, based on the blood measurement of the total hormone. Direct comparisons between different lifting schemes employed within practice to maximize muscle size, strength, or power are also scarce. The goal of the present study was to examine the free hormone (in saliva) responses to squat workouts using a power, hypertrophy, or maximal strength scheme design. Squat exercises were chosen to activate the larger muscle groups of the lower body. To determine the relative contribution of the different workout variables to any endocrine change, each scheme was equated by workout duration with the power and strength schemes also equated by load volume.

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Subjects

Eleven men volunteered to participate in this study. The mean (SD) age, height, and mass of the participants were 26.6 (6.7) years, 179.6 (6.2) cm and 79.0 (8.1) kg, respectively. All subjects were healthy and characterized as recreational weight trainers, training at least 2 days per week (>2 years), but none was considered a competitive lifter. None of the subjects was taking any dietary or performance supplements. Each subject had the risks of the investigation explained to him and signed an informed consent before participation in this study. The Human Subject Ethics Committee of the Auckland University of Technology approved all procedures undertaken.

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Equipment

Subjects performed their 1 repetition maximal (1RM) assessments and leg workouts on an isoinertial supine squat machine and a modified Smith machine (Fitness Works, Auckland, New Zealand). The supine squat machine incorporated a 300-kg pin-loaded weight stack attached to a sled on low-friction sliders, allowing the performance of horizontal squatting movements. The Smith machine is a common training and assessment device and allows the performance of squatting movements in the vertical direction. With the use of additional free plates, the load for each exercise was adjustable in 2.5-kg increments. Each machine was fitted with a mechanical brake to replicate subject knee angle (90° at the bottom position) for both exercises and across all sessions. The 1RM strength for the supine squat and Smith squat exercises were 226 (18) kg and 137 (13) kg, respectively.

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Procedures

Subjects were familiarized in the first session and their 1RM determined using a repetition to failure protocol (5). Subjects then randomly completed a power (8 sets of 6 reps, 45% 1RM, 3-minute rest), hypertrophy (10 sets of 10 reps, 75% 1RM, 2-minute rest), and maximal strength scheme (6 sets of 4 reps, 88% 1RM, 4-minute rest), based on prescriptive guidelines described elsewhere (7,10). For all schemes, the supine squat preceded the Smith squat with half of the sets performed on each machine (Figure 1). Before assessment, subjects performed a warm-up consisting of two submaximal sets on the supine squat (5-10 reps, 75-125% body mass) and lower limb stretching. The maximal strength scheme was performed with a traditional technique (i.e., nonprojection), although subjects attempted to move the load explosively. In the power scheme, a ballistic technique (i.e., jump squats) was used on the supine squat, with the Smith squat performed in a similar manner, but only up to the toes to minimize the risk of injury. Controlled lifting movements (e.g., 1.5 seconds up, 1.5 seconds down) were performed in the hypertrophy scheme. Workout duration was approximately 22 minutes for all schemes with the power and maximal strength schemes also equated by load volume (Figure 1). The same investigator supervised all schemes and provided verbal encouragement for each workout. Each session was conducted at the same time of day (between 2:00 pm and 5:00 pm) to minimize the diurnal variation effect. A 2- to 3-day recovery period separated each session, with subjects instructed to replicate diet and hydration 1 day before each workout.

Figure 1

Figure 1

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Saliva Collection and Analysis

Saliva samples were collected immediately before exercise (PRE), between squat exercises (MID), immediately postexercise (P0), and then every 15 minutes (P15, P30, P45, P60) for 1 hour (Figure 1). Subjects were instructed to avoid food, drinking hot fluids, and brushing their teeth 2 hours before assessment and were seated in the laboratory for 15 minutes prior to the resting sample being provided. In each case, 2 ml of saliva was deposited into sterile containers (Labserve, Auckland, New Zealand) and stored at −20°C until assay. At the completion of exercise, subjects remained seated in the laboratory until all samples were collected. During recovery, participants were allowed to drink water ad libitum. Saliva was analyzed in duplicate for T and C concentrations, using enzyme-linked immunosorbent assay kits (Salimetrics, State College, PA). Assay sensitivity was 3.7 pg·mL−1 for T, with intra- and interassay coefficients of variation (CVs) of 3.6% and 9.5%, respectively. Cortisol sensitivity was 0.007 ng·mL−1 with respective intra- and interassay CVs of 3.1% and 9.8%. Saliva samples for each subject were analyzed in the same assay to eliminate interassay variance. Assay plates were read using an Organon Teknika 230 S plate reader (Durham, NC).

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Statistical Analyses

Standard statistical methods were used for calculating means (±SE) for the hormonal variables. Before statistical analysis, log transformation was applied to each data set to normalize the distribution and reduce nonuniformity bias. Differences (between groups) and changes (within groups) in the log concentrations of hormones were then assessed using analysis of variance with repeated measures. The criterion level for statistical significance was set at P ≤ 0.05.

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Results

The salivary T responses to the three loading schemes can be observed in Figure 2. In the hypertrophy scheme, T concentrations increased significantly from MID to P60 (26% to 89%) compared with PRE values (P = 0.000-0.015). No changes in T occurred across the power and maximal strength schemes (P > 0.05). Significant differences were found between loading scheme concentrations (hypertrophy > power and maximal strength) from P0 to P60 (P = 0.000-0.007). Differences in postexercise T were also observed between the power and strength schemes at P15 (P = 0.049) and P60 (P = 0.015).

Figure 2

Figure 2

The salivary C responses for all schemes are plotted in Figure 3. In relation to PRE concentrations, a significant increase in C was observed across the hypertrophy scheme (47% to 290%) from P0 to P60 (P = 0.000-0.024). The postexercise concentrations following the hypertrophy scheme were also greater than the power and maximal strength schemes, from P15 to P60 (P = 0.000). A significant decrease in C (−44% to −51%) was observed in the strength scheme from P30 to P60 (P = 0.018-0.026), but no differences were found between the power and maximal strength schemes at any time (P > 0.05).

Figure 3

Figure 3

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Discussion

The configuration of the various workout variables, or lifting scheme design, imposed a specific activation pattern in the salivary (free) hormone responses to resistance exercise. The hypertrophy scheme increased T and C, whereas the power and maximal strength schemes produced little to no endocrine change. In general, the postexercise T and C responses to the hypertrophy scheme were greater than the other two schemes, which themselves displayed largely similar profiles. The differing endocrine response patterns may be attributed to the volume of load lifted in each scheme (hypertrophy > power = maximal strength) over the same workout duration. The power and maximal strength hormone results also suggest that differences in load intensity, rest periods, and technique are secondary to volume.

The hypertrophy scheme produced an elevated T profile, with no significant changes across the power and maximal strength schemes. These findings are largely consistent with the blood T responses to resistance exercise protocols (2,4,9,12,21). Muscle building schemes are synonymous with a high volume of load lifted across a workout (i.e., multiple repetitions, sets, and exercises per muscle group), thereby providing the stimulus for endocrine change that mediates subsequent adaptation. This is apparent in the current study with only the high-volume hypertrophy scheme increasing T. For a given loading scheme, increasing the number of sets performed (i.e., volume) across a workout (2,21) or lifting the same volume of load but reducing the workout duration (i.e., shorter rest periods) (14,19) both promote greater T responses. Thus, the configuration of volume and workout duration presents several possibilities to explain the T activation patterns. Other studies have found the anabolic (e.g., T, growth hormone) responses to strength endurance schemes (15 reps at 60% 1RM, 1-minute rest) comparable to those designed to maximize muscle growth across workouts of similar duration (21,26). Perhaps not surprisingly, the magnitude of these changes matched the total load moved (i.e., work performed) in the respective workouts. These data confirm our power and maximal strength results, that is, if different loading schemes are equated by volume and workout duration, one may expect similar hormone responses. Collectively, these findings support the notion that the volume of load lifted, in a given time period, is an important stimulus for T secretion.

Cortisol increased after the hypertrophy scheme, whereas the maximal strength and power schemes produced little to no C change, which is again consistent with research profiling different resistance schemes with blood (2,4,8,14,15,21,25,26) or saliva measures (13). Once more, it may be reasoned that load volume is a key variable behind these observations and confirmed, in part, by the effect of set manipulation upon the hormone responses to resistance exercise (2,15,21). As with T, the C responses to strength endurance and hypertrophy schemes were found to be comparable over a similar workout period, with the respective increases closely aligned to the total load moved (21,26). This would again explain why the two equal-volume schemes in the current study did not differ in their responses. Although no hormonal differences existed between the power and maximal strength schemes, C did decrease in the heavier protocol from P30 to P60. Smilios et al. (21) also reported a temporal decrease in C following a maximal strength scheme performed on different occasions. These results were not different, however, from control data taken from subjects on a nonexercising day (21), thereby implicating diurnal hormone variation. A limitation of the present study is the lack of control data for making such a comparison. Nonetheless, our results support the general observation that hypertrophy schemes elevate C, and more so than power and maximal strength schemes, and that load volume is an important factor contributing to this trend.

It is noteworthy that the salivary T (89%) and C (290%) responses to the hypertrophy scheme are much greater than muscle building schemes of similar volume (i.e., 8-12 sets) cited elsewhere (2,4,15,21), with these studies revealing respective increases of 13% and 45% (averaged) in the total concentrations of these hormones. These findings lend support to the notion that the free and salivary hormones exhibit a more dynamic response to intense exercise than the total hormone (3,18,20). Rowbottom et al. (20) directly compared the free and total C responses to an incremental treadmill run to exhaustion, followed by two maximal cycle sprints. Free hormone concentrations increased by 344% after exercise, with the total hormone increasing by only 49%. This difference was largely attributed to the saturation threshold of corticosteroid binding globulin (CBG), the primary transport protein for C (20). In other words, the free hormone increases linearly with the bound fraction, but once the CBG binding sites become saturated, one may expect a disproportionate increase in the free (and salivary) concentrations. Exercise-induced changes in blood temperature and/or pH may also enhance the free hormone pool by impairing hormone binding to their transport proteins (16,17). Caution should therefore be exercised when interpreting total hormone data, particularly when large endocrine and metabolic changes are expected.

In conclusion, salivary T and C were elevated in response to the hypertrophy scheme, whereas the power and maximal strength schemes produced little to no endocrine change. In general, the postexercise T and C responses to the hypertrophy scheme were greater than the power and strength schemes. The greater volume of load lifted in the hypertrophy protocol over the same workout duration may explain the different endocrine responses observed in this study. The similar hormone response patterns to the equal-volume power and maximal strength schemes also support this view.

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Practical Applications

Our results suggest that the volume of load lifted across different loading schemes of equal duration is an important determinant of the free hormone (in saliva) responses to resistance exercise. If free hormone activity following resistance exercise contributes to protein metabolism during recovery, then load volume maybe the most important workout variable to consider when designing workouts to activate the endocrine system and stimulate muscle growth. Given the findings presented, it could also be hypothesized that a workout volume threshold exists in order to create a hormonal environment conducive to protein turnover (elevated T and C) and that such an environment may be achieved by various resistance training methods, as long as the total load lifted reaches this threshold.

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Acknowledgments

The Health Research Council of New Zealand provided support during the preparation of this manuscript. This project was also supported by a grant from the New Zealand Foundation for Research, Science, and Technology.

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Keywords:

endocrine; squat; power; strength; hypertrophy

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