The inclusion criteria consisted of well-trained men, aged between 18 and 32 years (mean ± SD), having practiced RT for at least for 3 years without interruptions and a back squat/body mass ratio ≥1.5 and bench press/body mass ratio ≥1.0 (33). Moreover, the inclusion criteria comprised absence of the following (assessed by questionnaires): myopathies, arthropathies, neuropathies; muscle, thromboembolic and gastrointestinal disorders; cardiovascular and infection diseases; nondrinker (no alcohol intake whatsoever in their diet), nonsmoker, nonsupplements, and nonpharmacological substances (e.g., anabolic steroids); or any illegal agents for muscle growth at least for 1 year.
All volunteers were informed about the objectives and procedures of the study and gave us their written informed consent. The study (no. 1,697) was approved by the University Review Board for the Use of Human Subjects of the Federal University of Triangulo Mineiro and was written in accordance with the standards set out by the Declaration of Helsinki.
All the subjects completed 3-day diet records (2 days in the middle of the week and 1 at the weekend) (37), which (the 3-day food record) were collected twice during the study, in the first and last training weeks. Energy and macronutrients (carbohydrates, proteins, and fat) were quantified by a nutritionist who used “DietSmart Professional” software, version 7.7. Data on macronutrients were corrected for body mass to reduce interindividual differences.
To maximize muscle anabolic response, all volunteers consumed 30 g of a nutritional supplement (Whey Protein Super Bland concentrate, Spartacus Nutrition, São Paulo, Brazil) containing 24 g of whey protein and 6.4 g of carbohydrate immediately after all training sessions (3).
Body Composition Assessments
Total-body dual-energy x-ray absorptiometry (DXA) was performed using a densitometer plus scanner (GE/Lunar iDXA Corp., Madison, WI, USA, EUA). To minimize interobserver variations, all scans and analyses were performed by the same evaluator at the same time of day, and the day-to-day percent coefficient of variation was 0.5% for the bone-free lean mass and fat mass. Patients were instructed to remove metal objects (e.g., snaps, belts, underwire bras, jewelry), as well as their shoes and wore only light clothes. Body composition was analyzed using enCORE 14.0 software (GE/Lunar iDXA Corp.) for the total body. The upper trunk was defined as the trunk region minus the android region. More details on the analysis of regional body composition were described in another study (35). The muscle mass index (MMI) was calculated dividing the appendicular muscle mass (fat-free mass of arms and legs) by the height in meters squared.
Maximum Strength Assessment
The lower and upper body strength was quantified by the 1RM test, which consisted of the maximum load that an individual could lift during the exercises. Before the 1RM test, all volunteers reported no exercise other than activities of daily living for at least 72 hours. The 1RM test complied with recognized guidelines as established by the American College of Sports Medicine (1). The subjects performed a specific warm-up before testing consisting of loads corresponding ∼50% of the 1RM and 5–10 repetitions were performed. After the warm-up, the volunteers were allowed to rest for 1 minute. Then, 3–5 repetitions were performed and the load was increased between 60 and 80% of 1RM. After doing this exercise, the volunteers rested for 3 minutes. Then, the load was adjusted to find the equivalent load of 1 repetition maximum, which ranged between 3 and 5 attempts. The load that was adopted as the maximum load was the one used for the last part of the exercise that was performed with no more than one repetition by the volunteer. At the end of the study, only the 1RM of the back squat and the bench press exercises were reassessed, and it was used to determine muscle strength gains. The 1RM back squat was conducted before 1RM bench press with a 20-minute rest period separating tests (34). The same qualified fitness professional supervised all the 1RM tests.
Delayed Onset Muscle Soreness
A visual numeric pain rating scale was used to detect delayed onset muscle soreness (DOMS) as recommended by The National Initiative on Pain Control (26). All volunteers self-reported the subjective delayed muscle soreness (scale 0–10) according to the body segments (chest, elbow flexors, elbow extensors, thigh, and calf) the day after (24 hours) the first and the last RT session.
Resistance Training Protocol
A 5-days-a-week (Monday to Friday) regimen of the RT protocol (Table 1) was performed over 8 weeks. Both groups performed 2 different volume-equated training routines (HFRT and LFRT). Both groups performed 10 sets (except triceps extension and barbell curl, in which 5 sets were performed) per exercise, 8–12 repetition maximums with 70–80% of 1RM per set and 90 seconds rest recovery between sets and exercise in the training week. However, the LFRT group performed 2 specific resistance exercises in each training session, whereas the HFRT group performed all resistance exercises in each training session (Table 1). The LFRT group performed the RT (length time ∼31 minutes) divided according to the body segments: Monday—shoulder adductors and elbow extensors, Tuesday—knee extensors and hip extensors and flexors, Wednesday—shoulder extensors and elbow flexors, Thursday—knee flexors and plantar flexors, and Friday—shoulder abductors, lumbar spine flexors, and extensors. The HFRT group performed the RT (length time ∼32 minutes) for all body segments: Monday–Friday—shoulder adductors, elbow extensors, knee extensors, hip extensors and flexors, shoulder extensors, elbow flexors, knee flexors, plantar flexors, shoulder abductors, lumbar spine flexors, and extensors. The exercises performed were leg press 45°, squat, bench press, seated row, hamstring curl, barbell curl, tricep extension, lateral raises, calf standing, abdominal crunch, and lower back bench (Table 1). A warm-up session (1 set of 15 repetitions) with ∼50% of 1RM was performed in each exercise before each RT session. At the end of the RT sessions, stretching exercises were done so that participants could cool down. During RT, if the volunteer was able to perform more than 12 repetitions in the first set of each exercise, the load was adjusted between 5 and 10% to ensure the repetition zone between 8 and 12 repetitions and maintain the relative load of 70–80% of 1RM and a progressive overload.
Data distributions were assessed using the D'Agostino-Pearson test. The data are presented by mean and SD or confidence interval of 95% (delta values). For the participant's age and experience, the data are presented by median and interquartile interval. The Student's independent t-test (continuous data) or Mann-Whitney test (discrete data) was used to compare the baseline characteristics between the HFRT and LFRT groups. Levene's test was used to determine the equality of variances at baseline. Mauchly's test was used to evaluate the sphericity. Repeated measure analysis of variance was used to determine the effects of the group (LFRT and HFRT), time (pre and post), and interaction of time by group. When the repeated measure analysis of variance (F-test) was significant, effect size (partial eta-squared) and observed power statistics were calculated (Table 6). The Student's independent t-test was used to compare the difference in training volume (at weeks 1, 4, 8, and sum of the 8 weeks, for exercise and all exercises). Statistical significance was considered at p ≤ 0.05.
There was no difference between the groups concerning the participants' characteristics at baseline (Table 2).
Adherence to the HFRT and the LFRT was 98 and 97%, respectively. There were no differences in the dietary measure (carbohydrate, protein, fat, and energy) either within or between subjects over the course of the study (Table 3).
The changes in fat-free mass (total, trunk, gynoid, leg, and MMI) and muscle strength (bench press and squat) and muscle soreness (DOMS) after 8 weeks of intervention (pre vs. post) were statistically compared and interpreted. The LFRT showed more DOMS than HFRT at the beginning, middle, and end of the study (Table 4).
The HFRT showed a higher total volume than LFRT at the beginning, middle, and end of the study (Table 5).
There were significant (p < 0.05) effects for time in fat-free mass (total, trunk, gynoid, leg, and MMI) and muscle strength (bench press and squat), which indicates that both the interventions increase fat-free mass and muscle strength. There was no significant interaction (time vs. groups) in fat-free mass and muscle strength, which indicates that the responses were similar between the interventions (Table 6).
This study examined changes in muscle mass and maximal strength after an 8-week RT in different frequencies (LFRT and HFRT) in well-trained subjects. Our results showed that 8 weeks of HFRT (5 days a week) increases muscle mass and strength similarly to LFRT (1 day a week) in well-trained subjects. Thus, HFRT is not more effective than LFRT in increasing muscle mass and strength in well-trained subjects when the sets (10–15 sets per week) and intensity (8–12 RM) are equated per week.
The few existing studies concerning the RT frequency effect on muscle mass and strength in well-trained subjects have been limited to a 3-day frequency as HFRT (34,36). Evidence of different configurations of RT frequency is important to confirm previous findings or to bring new insight into RT frequency and muscle mass and strength gain interaction (13). Hence, we investigated the impact of 2 different frequencies: HFRT with 5 days a week vs. LFRT with 1 day a week, on muscle strength and size gains in well-trained men. Despite using higher frequency than those studies (5 vs. 3 times per week), we also did not observe significant differences between HFRT and LFRT for gains in total muscle mass, leg muscle, hip muscle, upper-trunk muscle, MMI, and bench press and squat strength. Our results are congruent with those of Thomas and Burns (36), who also showed hypertrophy and strength gains after RT regardless of training frequency in well-trained subjects. In addition, our findings are also supported by other studies that examined changes in muscle mass and strength after different RT frequencies in untrained (9) and older (14) subjects. Moreover, in a pilot study, Ribeiro et al. (29) showed that 4 weeks of RT over 4-day (n = 5) and 6-day frequencies promote similar increases in muscle mass and strength in elite bodybuilders. In contrast, a study reported that HFRT was better than LFRT (34). However, in this study, the researchers measured 3 muscles and reported that HFRT was better in forearm flexor hypertrophy but was not in extensors and vastus lateralis (hypertrophic responses were similar between HFRT and LFRT) (34). Therefore, it seems that regardless of the days per week used, different frequencies (with sets and intensity equalized per week) respond in a positive and similar fashion regarding changes in muscle mass and strength in well-trained subjects.
It is well known that a high RT set number per week produces greater hypertrophy gains (22,31), especially in well-trained subjects (2,18). In a systematic review and meta-analysis, Schoenfeld et al. (31) showed that greater muscle hypertrophy is achieved by performing at least 10 sets per week per muscle group. In the current study, both groups performed 10–15 sets (15 sets to biceps and triceps) per week per muscle group. Our finding showed that 10–15 sets distributed over 1 week (HFRT; 5 days a week, 2–3 sets per day) increase muscle mass and strength similarly to 10–15 sets performed in 1 day a week (LFRT 1 day a week, 10–15 sets per day) in well-trained subjects. These findings suggest that the total number of sets per week (i.e., ≥10 sets per muscle), but not the total volume distribution during the week, is important for muscle mass and strength gains in well-trained subjects.
We observed that the LFRT group showed more DOMS than HFRT at the beginning, middle, and end of the study (Table 4). Delayed onset muscle soreness has been associated with exercise-induced muscular damage (20). Muscular damage has been attributed to mechanical stimulus (i.e., eccentric contraction); however, metabolic stimuli (i.e., ischemia or hypoxia) may exacerbate the damage from eccentric contractions (20). Although the LFRT and HFRT were performed with similar loads (at 70% of 1RM), the higher daily volume per muscle group (e.g., metabolic stimuli) observed in LFRT (∼5 times higher than the HFRT) may have contributed to more DOMS (20). In a recent study, Bartolomei et al. (5) showed that an acute bout of resistance exercise with a higher volume produces a greater increase in the metabolic markers (i.e., cytokine, hormonal, and lactate response), muscle swelling (ultrasound measures), and DOMS and produces greater reduced muscle performance (countermovement jump and strength) in resistance-trained men. Furthermore, protection against muscle damage and DOMS due to resistance exercise has been attributed to the repeated bout effect (20). Thus, because the HFRT group performed a higher frequency in a week of resistance exercise for all muscle groups than the LFRT group (5 vs. 1 times/week), the repeated bout effect may have contributed to a protective effect against the DOMS in the HFRT group. Although LFRT caused more DOMS levels than HFRT, there was no difference between the groups for muscle mass and strength gains. Thus, HFRT may be an alternative strategy to LFRT, when sets and intensity are equated per week, to increase their muscle mass and strength without causing DOMS in well-trained subjects.
A dose-response relationship between RT set numbers per muscle group per week and hypertrophy has been reported (31). It has also been observed that a high daily set number per muscle group induces a lower repetition number (i.e., fatigue) in subsequent sets after the first sets, leading to a lower total volume per muscle group per week (19). Therefore, it seems reasonable to assume that RT with a low daily set number per muscle group and HFRT would promote a higher total volume per muscle group per week and more muscle mass gains than RT with a high daily set number per muscle group and LFRT. Indeed, in this study, the HFRT group performed a higher total volume (−13.9%; Table 5) than the LFRT group. This represented a small increase of ∼1.4 set per week in the HFRT group compared with the LFRT group. However, there was no significant difference between the groups in muscle mass and strength gains. These data suggest that the increased total volume (∼1.4 set per week) observed in the HFRT was not sufficient to improve muscle mass and strength gains in well-trained subjects compared with LFRT. Indeed, it has been shown that a small increase from 10 sets in RT does not cause a great change in hypertrophic gains (31). In a systematic review and meta-analysis, Schoenfeld et al. (31) showed that each set per week represents only a very small change in muscle size of 0.37%. Thus, increasing the RT frequency (when the sets and intensity are equated per week) to avoid the fatigue due to high volume of LFRT does not improve muscle mass and strength gains in HFRT compared with LFRT.
We set up the HFRT (5 days a week) with 2–3 sets (performed to volitional failure) per day to equal the set numbers per week of the HFRT group with the set numbers per week of the LFRT group. It has been observed that when the RT volume is increased, acute postexercise muscle protein synthesis is maximized in young men (7). An implication of this assumption for the current study is the possibility that the lack of superiority of HFRT over LFRT in muscle mass gain was due to low daily training volume (2–3 sets in 5-days-a-week routine) and, consequently, low muscle anabolic response. Although previous findings demonstrated that when given an adequate stimulus (e.g., volitional failure) during a training session, a low daily set number (i.e., ≤3 sets) per muscle group seems to be enough to achieve a maximum muscle anabolic response (4,8,13,15,23,24,27,28), these studies were not performed with well-trained subjects. Thus, future research is needed to address this issue.
In conclusion, our results showed that 10–15 sets (8–12 RM) distributed over a week (HFRT; 5 days a week, 2 set per day) increased muscle mass and strength similarly to 10–15 (8–12 RM) sets performed in 1 day a week (LFRT 1 day a week, 10–15 sets per day) in well-trained subjects. Therefore, our findings suggest a set number (≥10 sets) per week performed to volitional failure (8–12 RM), instead of training frequency, is an important “stimulus” to promote muscle mass and strength gains in well-trained subjects when the sets and intensity are equated per week. Thus, HFRT and LFRT are similar overload strategies for promoting muscular adaptation in well-trained subjects when the sets and intensity are equated per week.
Our results suggest that HFRT and LFRT are similar overload strategies for promoting muscular adaptation in well-trained subjects. This allows a greater possibility of manipulation of training frequency without reducing the performance in muscle strength and mass gains. In addition, the LFRT group showed more DOMS than did the HFRT group during the study. Thus, HFRT may be an alternative strategy to LFRT to increase their muscle mass and strength without DOMS in well-trained subjects.
This investigation was supported by the Fundação de Amparo à Pesquisa do Estado de Minas Gerais—FAPEMIG and by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES. The authors gratefully acknowledge the contributions of Jefferson Fernandes de Sousa for supervising the training sessions throughout the study and João Vitor Borges Mercaldi for funding part of the whey protein supplementation.
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Keywords:Copyright © 2019 by the National Strength & Conditioning Association.
training volume; split routine; total-body routine; hypertrophy