The age-related reductions in muscular strength and skeletal muscle mass observed in older women are negatively associated with the health, functional autonomy, and survival of older women (9,28,36). Resistance training (RT) is a well-recognized method of exercise for eliciting increases in muscular strength and hypertrophy and thus has been promoted as a means to attenuate these deleterious effects of aging (1,12).
Regular RT enhances muscular strength and hypertrophy through mechanical, metabolic, and hormonal stimuli (1,30) in a manner that leads to a series of intracellular events that ultimately regulate gene expression and protein synthesis (30,31,35). These stimuli can be manipulated by the variables that make up the RT prescription. Specific to older women, studies have shown a dose-response relationship between intensity of load and an increase in muscular strength and hypertrophy (5,7,23,37). Nevertheless, there is an interdependence between volume and intensity in which increasing RT intensity results in a decreased training volume. For this reason, the adoption of RT systems that allow for the execution of higher intensities without drastic reductions in volume has been suggested to optimize volume and intensity. The pyramid (PR) system, due to its inherent characteristic of varying loads and number of repetitions, permits exercise performance at higher intensities without necessarily reducing the volume from a specific loading zone standpoint. This may promote a favorable anabolic environment for increased strength and muscle hypertrophy, maximizing the combination of mechanical (heavy loads) and metabolic (accumulation of metabolic byproducts) stimuli (30). In addition, changing the RT methods could also be a factor that improves the motivation to exercise and, consequently training adherence.
A previous study from our laboratory indicated that in novice older women, the PR load-management system was similarly as effective as constant (CT) load training (25) for inducing muscular adaptations. However, the adaptive responses to training are individual and dependent on an individual's training experience with RT (2,10,11,26). In untrained individuals, the ability to compare muscular adaptations to different systems is confounded by the fact that they tend to respond favorably to multiple training stimuli. Therefore, experiments seeking to compare different forms of training manipulation that include untrained individuals must be interpreted with a degree of circumspection, as results may be primarily a function of the novelty of exercise, and virtually any training system may provide a sufficient stimulus to bring about training adaptations. Accordingly, studying the response of individuals with longer-term training experience may be necessary to determine the potential advantages of different RT systems. On the other hand, further muscular adaptations become progressively more difficult as one gains training experience because the so-called “window of adaptation” decreases during long-term RT (21). Although improvements do not occur at same rate over long-term periods, the proper manipulation of program variables such as volume and intensity can limit training plateaus and increase the ability to achieve a higher level of muscular fitness. Given evidence showing that greater loads are superior for maximizing strength in advanced lifters (24), it is important to assess whether a system that allows higher loads over the course of an RT session without a corresponding reduction in training volume enhances long-term gains in muscular strength and hypertrophy.
The purpose of this study was to examine the effects of different RT systems (PR vs. CT load) on muscular strength and hypertrophy in resistance-trained older women. Based on speculation that varying loads results in a greater training stimulus, we hypothesized that the PR system would elicit a greater increase in muscular strength and hypertrophy than a CT load training system.
Experimental Approach to the Problem
The study was divided into 3 phases. The first 2 phases consisted of 12-week periods where participants underwent a standardized RT program for 24 weeks (weeks 3–14 and 15–26); total volume was doubled during the second 12-week phase compared with the first one. These phases were intended to acclimate the participants to the stressors of RT, thereby eliminating the beginner effect for adaptations. In the third phase of the experiment, we sought to verify the effects of PR vs. CT load RT systems in the previously preconditioned participants by performing 8 weeks of RT (weeks 29–36) according to their assigned load-management system. At the beginning of phases 1 and 3, and at the end of the third phase, 2 weeks were used for evaluations consisting of anthropometric measures (body weight and stature), tests of 1 repetition maximum (1RM) in chest press (CP), knee extension (KE), and preacher curl (PC), skeletal muscle mass and body fat by dual-energy X-ray absorptiometry (DXA), and body water by spectral bioelectrical impedance. The posttraining measurements were performed with at least 72 hours of interval after the final RT session to avoid the acute effect of the last RT session. The experimental design is displayed in Figure 1.
Initially, 58 older subjects (≥60 years old) volunteered to participate in this investigation. Recruitment was performed through newspaper and radio advertisings, and home delivery of leaflets in the central area and residential neighborhoods. All participants completed health history and physical activity questionnaires and met the following inclusion criteria: 60 years old or more, physically independent, not receiving hormonal replacement therapy, and not performing any regular physical exercise more than once a week over the 6 months preceding the beginning of the investigation. Participants also were required to pass a diagnostic, graded exercise stress test with 12-lead electrocardiogram reviewed by a cardiologist, and be deemed to have no cardiovascular restrictions for participation. After individual interviews, 12 volunteers were dismissed as potential candidates because they did not meet the inclusion criteria. The remaining 46 older women underwent a preconditioning RT program. After the first 12-week phase, 5 participants dropped out, and after the second 12-week, phase 3 participants dropped out. The remaining 38 older women were then ranked by relative strength (total strength divided by skeletal muscle mass) and randomly allocated into 1 of 2 groups: a group that performed RT with CT load (n = 19) or a group that performed RT in an ascending PR fashion (n = 19). A blinded researcher was responsible for generating random numbers (random.org) for group placement. A total of 33 participants completed the experiment (CT, n = 16, PR, n = 17) and were included in the final analyses. The reasons for withdrawal were reported as lack of time, difficulty to travel to the University, lack of motivation, and personal issues. Written informed consent was obtained from all subjects, after a detailed description of study procedures was provided. This investigation was conducted according to the Declaration of Helsinki and was approved by the Ethics Committee of Londrina State University.
Skeletal muscle mass was estimated by the predictive equation proposed by Kim et al. (15), which has been validated when compared with magnetic resonance imaging. The appendicular fat-free mass used for the equation and the estimated body fat were determined by DXA scan (Lunar Prodigy, model NRL 41990; GE Lunar, Madison, WI, USA). Before scanning, participants were instructed to remove all objects containing metal. Scans were performed with the subjects lying in the supine position along the table's longitudinal centerline axis. Feet were taped together at the toes to immobilize the legs, whereas the hands were maintained in a pronated position within the scanning region. Subjects remained motionless during the entire scanning procedure. Both calibration and analysis were performed by a skilled laboratory technician. The equipment calibration followed the manufacturer's recommendations. The software generated standard lines that set apart the limbs from the trunk and head. These lines were adjusted by the same technician using specific anatomical points determined by the manufacturer. Analyses during the intervention were performed by the same technician who was blinded to intervention time point. Previous test-retest scans resulted in a standard error of measurement of 0.29 kg and intraclass correlation coefficient of 0.997 for skeletal muscle mass and standard error of measurement of 0.90 kg and intraclass correlation coefficient of 0.980 for percentage of body fat.
Total body water (TBW), intracellular water (ICW), and extracellular water (ECW) content were assessed using a spectral bioelectrical impedance device (Xitron 4200 Bioimpedance Spectrum Analyzer, San Diego, CA, USA), which has been validated for evaluating these measures (13,18). Before measurement, the participants were instructed to remove all objects containing metal. Measurements were performed on a table that was isolated from electrical conductors, with subjects lying supine along the table's longitudinal centerline axis, legs abducted at an angle of 45°, and hands pronated. After cleaning the skin with alcohol, 2 electrodes were placed on surface of the right hand and 2 on the right foot in accordance with procedures described by Sardinha et al. (29). Subjects were instructed to urinate about 30 minutes before assessment, refrain from ingesting food or drink in the last 4 hours, avoid strenuous physical exercise for at least 24 hours, refrain consumption of alcoholic and caffeinated beverages for at least 48 hours, and avoid the use of diuretics during 7 days before each assessment. Before each measurement day, equipment was calibrated as per the manufacturer's recommendations. The values generated by the equipment software for ICW and ECW were used for analysis. The TBW was estimated by the sum of ICW and ECW. Based on the test-retest, the technical error of measurement, coefficient of variation, and intraclass correlation coefficient for TBW were 0.5 L, 1.1%, and 0.99, respectively.
Maximal dynamic strength was evaluated using the 1RM test assessed on CP, KE, and PC performed in this exact order. Testing for each exercise was preceded by a warm-up set (6–10 repetitions), with approximately 50% of the estimated load used in the first attempt of the 1RM. This warm-up was also used to familiarize the subjects with the testing equipment and lifting technique. The testing procedure was initiated 2 minutes after the warm-up. The subjects were instructed to try to accomplish 2 repetitions with the imposed load in 3 attempts in both exercises. The rest period was 3–5 minutes between each attempt and 5 minutes between exercises. The 1RM was recorded as the last resistance lifted in which the subject was able to complete only 1 single maximal execution (3). Execution technique for each exercise was standardized and continuously monitored to ensure reliability. All 1RM testing sessions were supervised by 2 experienced researchers for greater safety and integrity of the subjects. Verbal encouragement was given throughout each test. The three 1RM sessions were separated by 48 hours (intraclass correlation coefficient ≥0.96). The highest load achieved among the 3 sessions was used for analysis in each exercise. Total strength was determined by the sum of the 3 exercises.
Participants were instructed by a dietitian to complete a food record on 3 nonconsecutive days (2-week days and 1-week end day) pretraining and posttraining. Subjects were given specific instructions regarding the proper way to record quantities of all food and fluid intake, including the viewing of food models to enhance tracking precision. Total dietary energy, protein, carbohydrate, and lipid content were calculated using nutrition analysis software (version 3.1.4; Avanutri Processor Nutrition Software, Rio de Janeiro, Brazil). All subjects were asked to maintain their normal diet throughout the study period.
Resistance Training Program
Supervised RT was performed during the morning hours in the State University facilities. The protocol was based on recommendations for RT in an older population to improve muscular strength and hypertrophy (1,12). All participants were personally supervised by physical education professionals to help ensure consistent and safe performance.
The sessions were performed 3 times per week on Mondays, Wednesdays, and Fridays. The RT program was a whole-body program consisting of 8 exercises, 1 exercise performed with free weights and 7 with machines executed in the following order: CP, horizontal leg press, seated row, KE, PC (free weights), leg curl, triceps pushdown, and seated calf raise.
During the first 2 conditioning phases, all participants performed 1 set of 10–15 repetitions maximum during the first 12-week phase and then 2 sets of 10–15 repetitions maximum in the second 12-week phase. Afterward, during the third phase, the participants of the CT group performed 3 sets of 8–12 repetitions maximum with the same load in the 3 sets. The initial loads used in phase 3 were based on subjects' values from the previous phase. Although the participants of the PR group performed 3 sets with the load increasing and number of repetitions simultaneously decreasing for each set, thus, the number of repetitions used in each set was 12/10/8RM, respectively, with variable resistance. For both systems, the participants performed exercises until volitional failure or an inability to sustain exercise performance with proper form.
Participants were instructed to maintain velocity of movement at a ratio of approximately 1:2 seconds (concentric and eccentric phases, respectively). Participants were afforded a 1–2 minutes of rest interval between sets and 2–3 minutes between each exercise. Instructors adjusted the loads of each exercise according to the subject's abilities and improvements in exercise capacity throughout the study in order ensure that the subjects were exercising with as much resistance as possible while maintaining proper exercise technique. Progression for the CT training group was planned when the upper limits of the repetitions zone were completed for 2 consecutive training sessions and for PR training when the participant could perform 2 or more repetitions in the last set. For both systems, weight was increased 2–5% for the upper limb exercises and 5–10% for the lower limb exercises to the next session (1).
During every RT session, researchers recorded the load and number of repetitions performed by participants for each set of the 8 exercises. Afterward, the volume load for each exercise was calculated by multiplying the load by the number of repetitions and sets. The total volume load was the sum of all 8 exercises. Then, the sum of the 3 sessions of a week was determined to be the weekly volume load.
Two-way analysis of variance for repeated measures was applied for comparisons. When the F ratio was significant, Bonferroni's post hoc test was used to identify the mean differences. The Cohen's d effect size (ES) was calculated as posttraining mean minus pretraining mean divided by the pooled pretraining SD (6), where an ES of 0.00–0.19 was considered trivial, 0.20–0.49 was considered as small, 0.50–0.79 as moderate, and >0.80 as large (6). For all statistical analyses, significance was accepted at p ≤ 0.05. The data were analyzed using Statistica software version 10.0 (Statsoft, Inc., Tulsa, OK, USA).
Adherence to the program was satisfactory, with all subjects participating in ≥85% of the total sessions throughout the experiment, that is ≥31 sessions during phase 1 (CT = 33.7 ± 1.4, PR = 33.1 ± 1.3, p > 0.05), ≥31 sessions during phase 2 (CT = 32.6 ± 1.2, PR = 32.5 ± 1.1, p > 0.05), and ≥20 sessions during phase 3 (CT = 22.7 ± 1.2, PR = 22.5 ± 1.1, p > 0.05).
There were no significant (p > 0.05) main effects for macronutrient daily intake, indicating that the relative daily intake of carbohydrate (CT: pre = 3.9 ± 1.0 g·kg−1, post = 4.2 ± 2.5 g·kg−1; PR: pre = 3.5 ± 1.2 g·kg−1, post = 3.8 ± 1.7 g·kg−1), protein (CT: pre = 1.0 ± 0.5 g·kg−1, post = 1.1 ± 0.5 g·kg−1; PR: pre = 0.9 ± 0.4 g·kg−1, post = 0.9 ± 0.4 g·kg−1), and lipids (CT: pre = 0.8 ± 0.4 g·kg−1, post = 0.7 ± 0.6 g·kg−1; PR: pre = 0.7 ± 0.3 g·kg−1, post = 0.6 ± 0.3 g·kg−1) were not different between groups and did not change over time. No differences between groups were observed for any outcome analyzed. The general characteristics of both groups at pretraining are presented in Table 1. Table 2 presents the participants' scores at baseline.
Table 3 depicts the training load and volume load at the initial and ending weeks of the RT program. As expected, the PR presented higher (p ≤ 0.05) training load (in kilogram) values than CT; however, PR presented lower (p ≤ 0.05) volume of load (load × repetitions) compared with CT. Both groups increased training load CT and volume of load without any group by time interaction, indicating that the progression was similar between groups.
The muscular strength and body composition outcomes for both groups at pretraining and posttraining are presented in Table 4. There was no significant interaction (p > 0.05) for any outcome analyzed. However, a significant (p ≤ 0.05) change from pretraining to posttraining was observed for CP, KE, PC, total strength, skeletal muscle mass, lower limb lean soft tissue, trunk lean soft tissue, TBW, and ICW, with both groups showing similar increases over time. No main effects were noted for upper limb lean soft tissue, body fat, and ECW (p > 0.05), but findings for upper limb lean soft tissue bordered an effect for time (p = 0.07).
Table 5 presents the ES values for both groups and the differences between them. All differences between groups were of trivial magnitude.
The main and novel finding of this study was that RT performed in a PR system was not superior to a CT load system for promoting adaptations in muscular strength and hypertrophy in previously well-trained older women. We had hypothesized that the PR system would augment results. The rationale for such a hypothesis was based on the dose-response relationship between intensity and neuromuscular improvements that has been shown to exist in older adults (5,7,23,37). Because the PR system allows the use of higher intensities of load during the final sets of an exercise without impairing volume in the target repetition range (i.e., 8–12RM), it was believed that the PR system would stimulate greater neuromuscular adaptations. However, contrary to our hypothesis, the results of this study failed to demonstrate a superiority of the PR over the CT load system.
To the authors' knowledge, this is the first study comparing different RT systems in trained older women. That said, other studies have been conducted, which shed additional light on the topic. Angleri et al. (4) investigated the effect of a crescent (ascending) PR system consisting of ∼15 repetition in the first set (65% 1RM), ∼12 repetition in the second set (70% 1RM), ∼10 repetitions in the third set (75% 1RM), ∼8 repetitions in the fourth set (80% 1RM), and ∼6 repetitions in the fifth set (85% 1RM) in 2 lower limb exercises (45° leg press and KE) in 32 trained men (27.0 ± 3.9 years) during 12 weeks. The results observed indicate that the ascending PR system induced similar muscle hypertrophy compared with a traditional training approach (CT load) in young resistance-trained men. Moreover, a previous study from our laboratory (25) using a cross-over design investigated 25 untrained older women (67.6 ± 5.1 years) who performed 8 weeks of an ascending PR system consisting of 12 repetitions in the first set, 10 repetitions in the second set, and 8 repetitions in the third set. Training included a total of 8 exercises targeting the major muscles of the upper and lower body. Results indicated that the ascending PR produce similar improvements in muscle mass (estimated by DXA) and muscular strength (1RM) compared with CT load system. Therefore, the current results expand on previous findings and allow for generalizability of results to previously trained older women. Collectively, these findings indicate that the PR system is a viable strategy to enhance muscle hypertrophy across different populations. Although PR did not show superior muscular adaptations compared with CT, from a practical standpoint, it may enhance motivation by varying the training stimulus and thus potentially improve exercise adherence.
There is evidence that higher intensities of load are superior for maximizing strength development in resistance-trained individuals (17,33). There are several notable differences between these studies and ours. For one, both aforementioned studies investigated the adaptive response in well-trained young adult men, whereas we used older women. Moreover, Schoenfeld et al. (33) and Mangine et al. (17) made a direct comparison of different training intensities where 1 group trained with heavier loads vs. another with lighter loads, whereas we compared a system that allows higher intensities of load in the final sets of PR vs. a CT loading scheme throughout sets in CT group. Based on these findings, we speculate that the repetition zone range applied in the PR training was not sufficient to elicit a greater mechanical stress stimulus compared with the CT system. Nevertheless, it is important to mention that the zone of repetitions used in our experiment is a popular strategy for promoting muscle hypertrophy. Further studies using the PR system with a wider repetitions zone range (e.g., 15, 10, 5RM) and thus producing a greater mechanical and metabolic stimulus are warranted.
Our results showed that the PR group trained with higher load than CT, mainly due to the final set of each exercise because it was performed as an ascending PR; however, this difference did not elicit superior results for hypertrophy or strength. Studies indicate that when repetitions are performed until volitional concentric failure under work-based conditions, the training load may not be a defining variable for maximizing muscle hypertrophy (20,33,34). In addition, although the literature indicates a clear dose-response between training volume and muscle growth (16,32), increases in muscle mass were similar between groups despite a greater volume load performed by PR. The beneficial effects of increasing volume follow an inverted-U curve, whereby once a given threshold is reached any further increases in volume would have no further effect and at some point, it could lead to a regression in gains. Therefore, it is possible that the volume threshold was achieved in the PR system, making the discrepancies in volume of load irrelevant in terms of producing a hypertrophic response. Alternatively, it can be speculated that although the differences were statistically significant, the absolute differences were not of sufficient magnitude to enhance results.
The gains in skeletal muscle mass and strength observed in this investigation occurred without alterations in subjects' habitual nutritional intake. These results suggest that the protein and energy intake observed throughout the progressive RT in this study was sufficient to support muscular improvements. However, the protein intake of participants was below current recommendations for protein intake in older individuals to build muscle mass (14). Therefore, the participants conceivably could have achieved even greater muscular increases had more protein been ingested, although not all studies indicate a necessity for higher protein doses in older individuals (22,27,38). It is also important to mention that food records have been shown to be unreliable for determining energy intake in the general public (8,19).
This study is not without its limitations. First, the duration of the study was fairly short, encompassing 8 weeks of regimented RT. We, therefore, cannot determine if results would diverge over a longer training intervention. Second, the findings are specific to older women and cannot necessarily be extrapolated to other populations; whether results would differ for younger individuals, men, or those with previous RT experience remains to be elucidated. Third, we did not control for the sleeping time of the participants, which could impact their response to training. Fourth, the subjects had 24 weeks consistent RT experience. Although this would seem sufficient to negate any beginner effects on muscular adaptations, the findings cannot necessarily be generalized to those who have been training consistently for longer periods. Finally, our relatively low sample size could have increased the probability of type II error.
We conclude that both RT system are effective to improve muscular strength and muscle growth, but the PR training system is not superior to CT for eliciting improvements in muscular strength and muscle growth in previously trained older women.
Based on the results reported in this study, practitioners can decide which system to use based on personal preference and responsiveness. From a practical point of view, PR training can be used as an effective alternative to optimize neuromuscular adaptations at similar magnitude of CT load RT in resistance-trained older women and may enhance motivation and thus promote better adherence to exercise.
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