Significant Strength Gains Observed in Rugby Players after Specific Resistance Exercise Protocols Based on Individual Salivary Testosterone Responses

Abstract

Our previous work has demonstrated that professional athletes show protocol-dependent variability in salivary testosterone (T) responses to resistance exercise (RE). The current study examines the consistency and functional outcomes of prescribing a RE regimen based on T response. We hypothesized that prescribing an individual-specific RE protocol based on T response would enhance weight training gains. Sixteen amateur rugby players [(mean ± SD) age: 20 ± 2 years; height: 181.5 ± 8.2 cm; weight: 94.2 ± 11.1 kg] were characterized by their maximal (T_max) and minimal (T_min) T response to four RE protocols: four sets of 10 repetitions (reps) at 70% of one repetition maximum (1RM) with 2 minutes' rest between sets (4 ×10-70%); three sets of five reps at 85% 1RM with 3 minutes' rest (3 × 5-85%); five sets of 15 reps at 55% of 1RM with 1 minute's rest (5 × 15-55%); and three sets of 5 reps at 40% 1RM with 3 minutes' rest (3 × 5-40%). Eight athletes then performed a 3-week training block performing only their T_max protocol. The remaining eight only performed T_min. After 3 weeks, the athletes were retested on the RE protocols and then crossed over and performed the alternate 3-week training block. All 16 athletes showed significant increases in estimated bench and leg press 1RM strength and bodyweight while performing T_max. When T_min was performed, 75% of athletes showed either no change or a significant decline in 1RM performance. Consistent protocol-responses over the experimental period were seen for both the T_max and T_min protocols in 12 of 16 athletes. Thus, a relationship between an individual's biologically available T response to RE and enhanced functional gains is reported.

Introduction

As with many athletic pursuits, improving aspects of body size, speed, power, and strength assists rugby performance and resistance to injury (¹⁷). Resistance exercise (RE) is regarded as an important part of an athlete's training schedule to achieve these aims (¹¹). Like many athletes, rugby players have great demands on their training volume in terms of skill and team training, so there is a need for RE to be as time-effective as possible. Various RE types are reported to improve power, strength, muscle size, and endurance (¹⁰).

It is highly likely that muscular adaptation is mediated by changes in hormones and growth factors. RE clearly elicits acute hormonal responses (^1,12), but the exact nature of the relationship with muscle adaptations remains equivocal. It has been reported in some studies that specific loading parameters of RE influence endocrine response. For example, Kraemer and colleagues (¹⁹) reported that although growth hormone secretion is sensitive to hypertrophy protocols, testosterone (T) is not. Typically, researchers have found that hypertrophy protocols (high total work, moderate loads, and short rest periods) elicit relatively large increases in serum total T concentration (^13,18,20). Furthermore, in these same studies, the use of weight training with lower total work and longer rest periods resulted in lesser or nonsignificant increases in T concentration. Other authors have reported an increase in total T concentration after both endurance exercise and resistance training irrespective of whether it is high load-low volume or low load-high volume (¹⁶). Decreases in serum total T have also been reported in body builders in response to some RE protocols (⁷). However, these studies focus on pooled group data across time rather than individual athlete responsiveness. It is possible that this focus has contributed to the variable results observed.

T in particular, as the primary anabolic hormone, has been linked to strength and muscle gain. The relationship in humans is based on a number of observations that include: men show muscle growth at puberty when T production increases (²²); aging men gradually lose muscle mass and strength, and exogenous application of T can reverse this trend (²); T replacement increases fat-free mass and muscle size in hypogonadal men (⁵); exogenous application of supraphysiologic doses of T in intact men results in greater strength and muscle gains from resistance exercise (^4,27); and pharmacologic blockade of T-specific receptors suppresses exercise-induced hypertrophy of skeletal muscle (¹⁵).

In addition, Hansen and colleagues (¹⁴) described a larger relative increase in isometric strength when the anabolic hormonal response was enhanced by additional leg exercises. Furthermore, Staron and coworkers (²⁶) linked increases in strength and muscle fiber transformation in men to increased serum T levels. These data, taken together, may suggest a link between acute exercise-induced elevations of T and increased strength possibly via endocrine-modulated protein synthesis. More recent data have demonstrated that T promotes the differentiation of pluripotent stem cells toward a myogenic lineage (²⁴).

This study examines salivary T as it offers a noninvasive collection methodology that enables steroid hormone sampling in athletes over a range of training conditions and environments. Salivary measurements are reliable (⁸) and highly correlated with serum measurements (^21,29). In addition, saliva contains only the unbound or bioavailable fraction of T (^9,28). Therefore, salivary T reflects the level of T that is available to bind to androgen receptors and thereby modulate physiological and functional responses.

Few studies have examined and compared acute individual T responses of rugby players with commonly prescribed RE protocols. In a recent study (³), we observed that 15 professional elite rugby players who performed four distinct RE protocols in a random order showed an insignificant protocol effect T concentration when considered as a homogenous group. However, when individual data among protocols were examined, a clear protocol-dependent effect was observed. Each individual athlete seemed to respond optimally, in terms of a T concentration increase, to one or two of the protocols, with minimal responses to the other protocols.

We hypothesized that functional strength gain may be further enhanced by individuals adopting a non-traditional periodization, focused for a prolonged period on a protocol that maximized T response (T_max). Frequent retesting could be employed to determine if and when this should change based on T responses. This could have practical significance given the fact that training programs for professional athletes are complex and sessions are prioritized. Thus, the purpose of the present study was to investigate the functional effects of four distinct RE protocols prescribed based on individual T responses in a group of amateur rugby players. We also aimed to examine the consistency of the RE protocol that elicited T responses in this population.

Methods

Experimental Approach to the Problem

Athletes performed four distinct RE protocols in an initial characterization phase. During this phase, each protocol was randomly completed on two occasions with at least 2 days between each protocol. The protocol that produced the maximal (T_max) and the minimal (T_min) change in salivary T concentration, when averaged over two repeated sessions, was recorded for each individual. After initial testing, the group was split into two subgroups, each containing eight individuals. One subgroup performed a 3-week training block that involved RE twice a week on their individualized T_max protocol. The other subgroup performed their T_min protocol during the same period. These athletes were retested on the four protocols (once per protocol) after 3 weeks of training. After resting for 5 days (unloading), a cross-over in protocol occurred, and subjects performed the alternate training block for 3 weeks. Recharacterization sessions were performed (twice per protocol) after the second training block. No other weight training was performed. The T_max and T_min protocols were based on the initial characterization results and were not adjusted to reflect any changes in response observed during the experimental period.

Subjects

Before the study, participants attended a presentation outlining the purpose and procedures involved. Written informed consent was provided, and ethical approval was obtained from the Waikato Ethics Committee. Sixteen amateur rugby players [(mean ± SD) age: 20 ± 2 years; height: 181.5 ± 8.2 cm; weight: 94.2 ± 11.1 kg] were studied during their off season. These subjects had at least 2 years of weight training experience and performed at least 4 hours per week off-season training. All athletes were familiar with the purpose of the trial and the procedures involved.

Procedures

Before the study, the maximal bench press and leg press strength of the athletes was assessed. The one repetition maximum (1RM) was determined for each exercise to allow calculation of loads using a previously reported method (³⁰). Body weight was measured before breakfast using free-standing electronic scales on the Friday of each week between 0700 and 0730 hours.

Resistance Training Protocols

Athletes performed the RE protocols at a private gymnasium at the same time on each testing day to account for the circadian rhythm shown by T. In addition, the athletes were directed to mimic their pre-exercise routine (e.g., diet, transportation) as closely as possible on testing days. The four RE protocols each consisted of four exercises (bench press, leg press, seated row, and squats) that activated large muscle masses and were: four sets of 10 repetitions (reps) at 70% of 1RM with 2 minutes' rest between sets (4 × 10-70%); three sets of five reps at 85% 1RM with 3 minutes' rest (3 × 5-85%); five sets of 15 reps at 55% of 1RM with 1 minute's rest (5 × 15-55%); and three sets of five reps at 40% 1RM with 3 minutes' rest (3 × 5-40%). Saliva samples were obtained immediately before and within 5 minutes of completing exercise. Saliva sample collection, procedures, and sample analyses for [T] were as previously described (³). The mean coefficient of variation (CV) for the T immunoassay analyses was 3.2% ± 2.1%.

The loading parameters of the four protocols were based on those used in previous studies (^25,31). Athletes were instructed to perform the exercises in the 3 × 5-40% protocol with the intention of producing the greatest rate of force development possible. In the initial characterization phase, subjects completed each protocol twice (total of eight sessions) in random order with each RE protocol separated by at least 2 days.

Statistical Analyses

Repeated-measure analyses of variance were undertaken to determine treatment effects. The α level for significance was set at P ≤ 0.05. A χ² analysis was performed to test for individual protocol consistency.

Results

All 16 athletes completed the four-protocol testing before, after the first 3 weeks, and after the second 3-week training block. Of the 16 athletes, 12 showed consistency in protocol eliciting both T_max and T_min during the experimental period. This consistency is significantly higher than would be expected by chance (P < 0.001, χ² test). One other athlete showed consistency with respect to the protocol that induced the T_max response only (Table 1). Other training, order of training block, and repeats had no significant effect (P > 0.05) on responses. Individual responses were protocol-dependent (P < 0.01).

Table 1: Free testosterone concentration changes in amateur athletes

Responses in Athletes Performing T_max Then T_min Training Blocks: Bench Press and Body Weight.

1RM data for both the bench press and leg press were estimated based on the best set performance in either of the two workouts per week. These data, as well as body weight (one weekly measurement), were normalized into a percent increase based on data from the initial test period for each individual. When these data were pooled into a group mean and standard error, the results were significantly different (P < 0.05) between the two blocks, with all eight athletes significantly increasing strength and body weight (P < 0.05) during the first 3-week training block (Figure 1).

Figure 1: Strength and body weight responses of amateur athletes (n = 16) to protocols that elicited the largest (T_max) and smallest (T_min) change in salivary testosterone concentration and training protocols. Subjects performed 3 weeks of their individual T_max before 3 weeks of T_min training. 1RM = the estimated 1 repetition maximum bench press lift based on an individual's best set.

After retesting and another 5 days of unloading, the group performed their T_min protocol. On average, this second 3-week training block led to a loss of both strength and body weight in the athletes (Figure 1). Four of the individual athletes showed a significant loss of 1RM strength and body weight. Two athletes showed no significant changes, and two showed small but significant gains in strength and body weight when performing their T_min protocol. Interestingly, these latter two athletes were subjects 14 and 16, who had shown changes in protocol response during the experimental period. Part of this overall difference may simply have been a plateau effect, with training gain leveling out during the experimental period.

Responses in Athletes Performing T_min Then T_max Training Block: Bench Press and Body Weight.

To determine whether gains observed were in fact caused by a plateau effect, the other half of the original group undertook the reverse pattern of training. The eight individuals in this second group started training on their T_min for their first 3-week block. They then crossed over to their T_max for a second 3-week training period. Under these experimental conditions, the T_min protocol performed during the first 3 weeks led to a small average loss in strength and body weight in the group (Figure 2). Of the eight individuals, five showed significant decreases (P < 0.05), one had a nonsignificant change, and two made slight gains. Of the two that made gains, one athlete was subject 8, who showed inconsistency in the protocol inducing T_min and T_max during the experimental period.

Figure 2: Strength and body weight responses of amateur athletes (n = 16) to protocols that elicited the largest (T_max) and smallest (T_min) change in salivary testosterone concentration and training protocols. Subjects performed 3 weeks of their individual T_min before 3 weeks of T_max training. 1RM = the estimated 1 repetition maximum bench press lift based on an individual's best set.

After the cross-over, the group on average showed significant strength and body weight gains (P < 0.05). All eight athletes showed gains that were significantly different from the changes observed in the first 3-week block (P < 0.05).

Leg Press Responses

A similar pattern emerged for both groups in leg press results. These results are presented in Table 2. In the first group, all eight individuals showed significant strength gains in leg press during the first 3-week block (performing T_max). In the second 3-week block (performing T_min), five of the athletes showed a small, significant loss of strength, two athletes showed no significant changes, and one athlete showed a small but significant gain. In the second group, all eight individuals showed strength gains in their second training block of 3 weeks (performing T_max). In contrast, six individuals showed a significant strength loss in the first 3-week training block (performing T_min), while one showed a slight but significant gain in strength.

Table 2: Strength and body weight responses of amateur athletes

Discussion

In the present study, we examined the effect of four distinct RE protocols (4 × 10-70%, 3 × 5-85%, 5 × 15-55%, or 3 × 5-40%) on acute T saliva responses over a period of approximately 14 weeks. A cross-over intervention was imposed on two subgroups. Salivary T was determined immediately before and after training and is presented as a change in [T]. In this study, we report functional strength gains in sub-elite athletes during their off season that were strongly linked to RE protocols that induced a maximal free salivary T response.

A previous study (³) reported that elite athletes showed a protocol-dependent maximal salivary T response. Individuals varied in this protocol. This study of amateur rugby players reinforced these earlier findings. In addition, 12 of the 16 athletes showed significant consistency not only in the RE protocol that induced a T_max response during the experimental period, but also in the protocol that presented the T_min response. This is compelling evidence that the protocol that induces an anabolic response in an individual is consistent and that this consistency is maintained for a period of time irrespective of other training. To our knowledge, the consistency observed has not been previously reported.

The data presented in the current study suggest that most of our athletes' gains were enhanced, in terms of both strength and body weight, when performing the T_max protocol. Furthermore, athletes generally lost strength and body weight as a result of performing their T_min protocol. However, a number of individuals did gain during both training blocks. Interestingly, these were generally individuals who did not show a consistency in the protocol that produced T_max or T_min during the recharacterization of the four RE protocols.

Our report suggests, for the first time, a direct relationship between RE protocols shown to induce T_max in an individual and functional gain. It does not prove that T is the effector in this gain, but it clearly demonstrates that T can be used as a marker for selecting protocols to maximize functional gain. Over time, the choice of protocol may need to be varied depending on other factors. It is unlikely that an individual would continue indefinitely to be maximally responsive to one type of protocol. However, given the known effects of T on maximal voluntary strength and skeletal muscle hypertrophy (⁶) and the observations of Hansen et al. (¹⁴), this observation could prove beneficial for periodization prescription.

Some interesting trends were observed when examining individual T_max and T_min responses to the four RE protocols. Both of the individuals that had the largest T response to the 3 × 5-40% protocol presented the 4 × 10-70% protocol as their minimal response before and after the experimental period. Similarly, of the seven individuals that responded optimally to the 4 × 10-70% protocol, five (71%) consistently presented the 5 × 15-55% protocol as their minimal response protocol. Such observations could have important ramifications for practitioners prescribing RE. The existence of a response threshold dependent on RE protocol variables has been suggested for T (^18,23). If there were individual variation in hormonal threshold levels, it would make sense that individuals responded differently to RE. One might expect that this threshold would differ among individuals and that this variance may be normally distributed among a population. For example, individuals with low T response thresholds may have an enhanced hormonal response to a low-load, explosive training protocol. Alternatively, for individuals that required a large volume of exercise to elicit a T response, a 5 × 15-55% type protocol may be more appropriate. Individual responses may be related to individual response thresholds, although this requires further investigation.

There are several caveats that need to be applied to our study. First, the study was relatively short with only a small number of athletes. Second, 1RM estimations from best repetitions may not offer absolute accuracy, although our results can be regarded as showing relativity. Third, only four RE protocols were employed. Whereas classical periodization often employs a set time on strength, power, hypertrophy, and a range of other factors, the current strictness of the protocols was more limiting than would be seen in more modern alinear and micro-periodizations, in which variety may play an important role in maintaining gains. It is also acknowledged that an increase in body weight does not necessarily reflect an increase in muscle mass.

What our research suggests is that testing an individual's T response periodically to a variety of protocols may enable trainers to select an optimal protocol that maximizes an individual's functional gain during a 3- to 4-week period. This still utilizes a periodization approach, but one based on initial hormone responsiveness, thereby optimizing an athlete's RE time. Although the mechanism by which functional gain was achieved remains unknown, it seems that the ability of a RE protocol to induce an increase in free T is causatively linked to strength and body weight gains. These conclusions should be more rigorously tested in larger populations across a range of weight-training experiences. A training study that compared serum free T and salivary T responses should also be considered.

Practical Applications

Professional athletes must gain as much benefit as possible from RE. This study observed a relationship between salivary T responses to RE and strength gains. Specifically, optimizing T response at an individual level to create a maximally anabolic environment enhanced 1RM strength and body weight gains in rugby players. This relationship between hormonal response and functional gains may have important implications for RE prescription and help trainers to structure workouts to achieve maximal benefits.