When beginning a resistance training program, it is traditionally thought that adaptations within the nervous system and muscle hypertrophy play mechanistic roles for explaining the increased strength observed with resistance exercise. The initial increase in strength is thought to be primarily from neural adaptations followed by larger contributions from muscle hypertrophy after the first few weeks of training (21). This idea is further supported by studies (5,14) that have found that the percentage change in muscle size explained a significant amount of variance (~19%) in the percentage change in muscle strength. In fact, data from our own research group has observed, using within subject correlational analysis, that changes in muscle size can explain up to 35% of the variance in muscle strength after an 8-wk resistance training program (17). Given this suggested important relationship between muscle size and strength, many resistance training programs (i.e., classical periodization, daily undulating periodization) consist of a hypertrophy phase or day in an effort to provide a foundation from which to optimize strength after targeted training (3,32,33). This would also suggest that training volume is an important contributing factor for increasing muscular strength as some degree of volume is thought to be required for muscle growth (18,25,29–31). For instance, Rønnestad et al. (30) found that multiple sets increased muscle strength and size to a greater degree compared with only performing a single set and suggest that the increase in muscle size was the reason for the large increases observed in strength.
Given the aforementioned suggestion that muscle growth is a large contributor to strength gain after resistance training, it is perhaps surprising that little direct human evidence exists for this thesis (i.e., the change in size causing the change in strength). A recent review by Buckner et al. (8) suggests that there may even be a complete dissociation between the change in muscle size and strength after a resistance training program. For example, previous studies seeking to investigate this question are retrospective in nature and rely on correlational statistics to draw their conclusions on what variables are important for increasing maximal strength. Yet, despite these statistical relationships, we would be remiss to suggest that these two phenomenon are causally related just because they occur within a similar time frame. It is hypothesized instead that the changes in strength appear to be driven more so by the principle of specificity rather than the change in muscle size (9,19). Rasch (26) suggested this as early as 1955 and hypothesized that the changes in strength after exercise were largely the result of learning (27). In support of this contention, low load (30% one repetition maximum [1RM]) and high load (80% 1RM) resistance training have shown similar changes in muscle growth between conditions but divergent changes in isotonic strength (20). The authors noted that the high load condition had a greater increase in 1RM strength than the low load condition and this difference was attributed to the principle of specificity. A follow-up study from the same group using a between subject design again found similar increases in muscle size between both training conditions as previously shown (20) but demonstrated that periodically practicing the 1RM test (i.e., every 3 wk) diminished the strength differences between high load and low load training (22).
It is difficult to determine if the increased strength was due to the actual resistance training program or if it could simply be explained by practicing the test because both groups performed training and regular 1RM testing concurrently. A recent study investigated this question using a within subject design by comparing a condition which practiced the 1RM test immediately followed by three sets of additional resistance exercise (training condition) to a condition that only performed the 1RM test (testing condition) at each training session (12). The authors observed an increase in muscle size only in the training condition; however, muscle strength was not different between conditions. This would suggest that the additional exercise volume and muscle growth did not contribute to the increase in strength and supports that these changes in strength are driven largely through the principle of specificity. One limitation of that study was the use of a within subject design which makes it difficult to know if the crossover effect may have contributed to part of the change in strength. In addition, that study was completed in trained individuals and this change in muscle size may play a more important role in the early phase of training in those who are previously untrained. Thus, the purpose of this study was to further determine if muscle growth is important for increasing muscle strength or if the strength can be entirely explained from just practicing the test in untrained participants. Unlike previous studies using retrospective correlations, we tested this question using a study designed to produce different effects on one variable (muscle size) and observe how this manipulation directly impacted the results of the other variable (muscle strength).
A total of 40 untrained individuals (18 men, 22 women) were recruited for the current study. Two individuals (one man, one woman) in the hypertrophy (HYPER) training group were unable to complete the study due to personal reasons; therefore, their data was excluded from all further analyses which decreased the sample size to 18 in this group. All individuals (n = 20) in the Testing group (TEST) completed the study. Individuals were classified as “untrained” if they did not perform any resistance training for at least 6 months in the upper and lower body. Individuals were excluded if they were not between the ages of 18 and 35 yr, resistance trained in the upper and lower body, if they used tobacco related products, or had an orthopedic injury preventing exercise. The study received approval from the university's institutional review board and each participant gave written informed consent before participation.
The participants visited the laboratory 20 times over the course of 10 wk; two pretesting visits, 16 training visits (two training sessions per week), and two posttesting visits. The two pretesting visits occurred in the first week (week 1) and the two posttesting visits occurred in the last week (week 10). During previsit 1, the participants filled out an informed consent. After confirming that they did not meet any exclusion criteria, height and body mass was measured using a standard stadiometer and an electronic scale. Next, limb dominance was determined by asking which hand they wrote with (arm) and which leg they would kick a ball (leg) with. After determining arm and leg dominance, muscle thickness, 1RM testing, and familiarization of isometric and isokinetic testing were completed. During familiarization of isometric and isokinetic testing, the participants were asked to give 20% effort for each test to reduce the potential training effect of practicing maximally. Individuals were then placed in a randomized, counterbalanced fashion, into either a HYPER training group or a testing (TEST) group. Previsit 2 occurred 48–72 h after previsit 1. During the second previsit, participants performed isometric and isokinetic testing and muscular endurance in the lower and upper body. Next, a total of 16 training sessions of unilateral knee extension and chest press exercise was performed twice a week with at least 48 h in between training sessions for eight consecutive weeks. The first posttesting visit was performed 48 to 72 h after the final training session at the same time of day as previsit 1. The second posttesting visit was at least 1 d apart after the first posttesting visit and at the same time of day as previsit 2.
The HYPER group performed a high-volume resistance training program designed to produce growth and increase strength (HYPER; n = 18; men = 7, women =11) and the TEST group completed a program designed to minimize growth and maximize strength by just performing a 1RM strength test (TEST; n = 20; men = 10, women = 10). Each training session began with a measure of perceived recovery status (PRS) using a 0 to 10 scale. Knee extension exercise (Hammer Strength Plate Loaded Iso-Lateral Leg Extension; Life Fitness, Rosemont, IL) was performed unilaterally and occurred first followed by chest press exercise (Hammer Strength Plate-Loaded Iso-Lateral Bench Press; Life Fitness). For the knee extension exercise, participants had their arms crossed over the chest and wore a seat belt to minimize extra movement and emulate testing. During each training visit, individuals alternated which leg (dominant or nondominant) exercised first. Participants in both groups performed one set of 10 unloaded repetitions in each leg as a warm-up. The training protocol for the HYPER group consisted of 4 sets with a goal of 8 to 12 repetitions with 90 s of rest between sets. If the participant did not fall in between the repetition range, the load was adjusted accordingly to try and maintain the next set within 8 to 12 repetitions. Knee extension exercise was performed to volitional failure and to the beat of a metronome with 1.5 s for the concentric portion and 1.5 s for the eccentric portion. A preset bar for knee extension was used to determine full range of motion, and only those attempts that touched the bar were counted as a repetition. If the participant missed reaching the bar twice in a row, the set was terminated. Participants in both groups were then warmed up on the chest press exercise. Because of the differences in baseline strength, female participants performed one set of five unloaded repetitions as a warm-up for the chest press while male participants performed one set of 10 repetitions. For chest press exercise, the elbows had to be fully locked out to be counted as a repetition. The load was adjusted accordingly each set so that the participant fell between 8 and 12 repetitions in the HYPER group. The chest press exercise was performed to volitional failure and to the beat of a metronome with 1.5 s for the concentric portion and 1.5 s for the eccentric portion. The training protocol for the TEST group consisted of five attempts to lift as much weight as possible one time for that training visit with 90 s of rest between attempts. The load was progressively increased each attempt to try to reach or exceed their previous 1RM. During the attempts for knee extension, if the participants failed to hit the bar before the fifth attempt, the training session for that limb was terminated. Likewise, if the participants failed to fully lockout their arms on the chest press, the training session for that exercise was terminated. Most individuals completed three attempts but no one completed more than five attempts per limb/exercise for the TEST group during training. Participants in both the HYPER and TEST group were encouraged during the training visits to beat their previous best.
A 1RM for the knee extension and chest press exercise was obtained for each individual on visit 1 (previsit 1) and 19 (postvisit 1). For knee extension, a 1RM for each leg was performed. First, the seat was adjusted accordingly for each participant. The participants were instructed to have their arms crossed over the chest to ensure strict form and to avoid extra movement. In addition, a seat belt was crossed over the waist and was pulled securely. A preset bar was used to determine full knee extension and only those attempts that touched the preset bar were counted. Participants warmed up with a relative low load estimated at 30% 1RM. After this brief warm-up, the load was adjusted to an estimated 1RM and the first attempt was made. The first attempt was estimated off of how the individual’s warm-up looked to the investigators and how the warm-up felt to the participant. As participants got closer to their 1RM, the load was either increased or decreased in 1.25-kg increments until a 1RM was obtained (usually within five attempts). A period of 90 s of rest was given between each attempt. A 5-min rest period between each leg was given. After the completion of knee extension 1RM, an additional 5 min of rest occurred before 1RM testing in the chest press.
The seat height for the chest press was adjusted so that the handles were at the middle or bottom of the chest for each individual. Participants were instructed to keep their feet flat on the floor with a thumb width grip from the end of the handles to ensure strict form. To be counted as a repetition, participants had to have their arms fully locked out. Similar to knee extension, participants warmed up with a relatively low load. After the brief warm-up, the load was adjusted to an estimated 1RM and the first attempt was made. As participants got closer to their 1RM, the load was then either increased or decreased in 2.5‐kg increments until a 1RM was obtained (usually within five attempts). A period of 90 s of rest was given between each attempt.
B-mode ultrasound (GE, Fairfield, CT) was used to measure muscle thickness. The distance between the muscle-fat and muscle-bone interface was measured by placing a probe (8–10 MHz) on the skin surface while using conductive gel to avoid depressing the skin. Muscle thickness measurements were taken on the posterior upper arms at 50%, 60%, and 70% of the distance between the acromion process and lateral epicondyle (11). The minimal difference (i.e., reliability) at each site was 0.27, 0.08, and 0.19 cm for the 50%, 60%, and 70% sites, respectively. An additional measure was taken on the anterior portion of the upper arm at the 70% site to serve as a within participant time control. In addition, muscle thickness was measured at 50%, 60%, and 70% of the distance between the greater trochanter and lateral condyle of the femur on the anterior and lateral portion of the upper leg (2,17). The minimal difference (i.e., reliability) at each site on the anterior thigh was 0.11, 0.13, and 0.19 cm for the 50%, 60%, and 70% sites, respectively. The minimal difference (i.e., reliability) at each site on the lateral thigh was 0.16, 0.16, and 0.22 cm for the 50%, 60%, and 70% sites, respectively. Two images were taken at each site at each time point and were stored and later analyzed with the ultrasound software in a blinded manner by the same investigator. The average of the two measurements was recorded as the muscle thickness for that site. Muscle thickness measurements were taken pretraining (visit 1) and posttraining (visit 19).
Isometric and isokinetic torque measurements were performed on a dynamometer (Quickset System 4; Biodex, Shirley, NY). The chair and arm lengths were appropriately adjusted and recorded for lower and upper body testing to ensure the same settings were used for previsits and postvisits. Before each test, the limb was weighed to correct for gravity. Participants first performed all leg testing measurements followed by upper body testing measurements. To determine isometric strength, participants were asked to extend their leg (~3–8 s) against an immovable object as hard as possible until torque plateaued or began to decline. A test time of up to 15 s was given to allow the participant to reach their maximum potential. The participants performed two maximal voluntary contractions (MVC) with 60 s of rest between each contraction at 90° knee flexion. After isometric testing, participants then performed isokinetic testing at two different speeds in the legs. First, the participants completed two sets of three repetitions at 180°·s−1. Then they completed two sets of three repetitions at 60°·s−1. There were 60 s of rest between sets for each isokinetic test. Upon completion of isometric and isokinetic testing of the lower body, isometric strength testing was performed in the upper body on the elbow flexors. The participants performed two MVC at 60° elbow flexion against a fixed lever arm until torque plateaued or declined (~3–8 s) with 60 s of rest between attempts. This testing measurement was to serve as a within participant time control. Participants were given strong verbal encouragement throughout each test. Visual feedback was provided to the participants for all testing measurements. During visual feedback, a line was made at the maximal value the participant had reached for the first repetition. The participants were then instructed on the next repetition to exceed their previous maximal value. Isometric and isokinetic testing occurred on the second previsit and second postvisit. The order for which limb tested first was randomly determined each testing visit. The highest value achieved within each test was used for analysis.
Participants completed as many repetitions as possible for one set in the knee extension and chest press exercises using 60% of their 1RM to a cadence of 1.5 s for the concentric and 1.5 s for the eccentric portion of the lift for previsit 2. Sixty percent of their 1RM was chosen for the muscular endurance test based on Campos et al. (10). The test was terminated if the participants were unable to maintain the cadence or could not lift the load through a full range of motion. During knee extension testing, participants were buckled in with a seat belt and kept their arms crossed over the chest. Five minutes of rest between each leg was allotted as well as between the knee extension and chest press exercises. During the chest press testing, participants kept their feet flat on the floor with a thumb width grip from the end of the handles. The test was terminated if the participants were unable to maintain the cadence or could not fully lock out the arms. Postmuscular endurance testing was performed at 60% of their pre-1RM (same weight as previsit 2). Muscular endurance testing occurred on visits 2 and 20.
Surface EMG was recorded from the vastus lateralis and rectus femoris of each leg and the elbow flexors of each arm. A mark was placed on the muscle belly of each rectus femoris at 50% of the distance from the anterior-superior iliac crest to the proximal boarder of the patella. Additionally, another mark was placed on the muscle belly of each vastus lateralis at 66% of the distance from the anterior-superior iliac crest to the lateral patella. For each elbow flexor, a mark was placed between the medial acromion at a distance of one third from the antecubital fossa. The skin was shaved, abraded, and then cleaned with isopropyl alcohol wipes. Electrodes were then placed where the marks were made. Bipolar electrodes had an interelectrode distance of 20 mm, whereas a ground electrode was placed on the seventh cervical vertebrae at the neck. The surface electrodes were connected to an amplifier and digitized (iWorkx, Dover, NH). A bandpass filter was used and the signal was filtered (low-pass filter 500 Hz; high-pass filter 10 Hz), amplified (1000×) at a sample rate of 1 kHz. The participants performed two MVC for the knee extensor muscles at a joint angle of 90° on an isokinetic dynamometer (Biodex System 4). Upon completion of knee extensor testing, the participants performed two MVC for the elbow flexors at a joint angle of 60°. sEMG was only recorded from the rectus femoris, vastus lateralis, and elbow flexors during MVC. Computer software program (iWorkx) was used to analyze the data. sEMG amplitude (root mean square, RMS) was analyzed from 3 s of the highest pre- and post-MVC.
Perceived recovery status
Perceived recovery status was recorded each training visit immediately before exercising (16). Values ranged on a 0–10 scale with 0 = very poorly recovered/extremely tired and 10 = very well recovered/highly energetic.
Total exercise volume
Exercise volume was calculated by multiplying the load by the number of repetitions completed. This was done for every set of exercise as well as the warm-up throughout the training study. Exercise volume is represented herein as the average total exercise volume completed (sets of exercise + warm-up set) across the training sessions within each group.
Data are presented as mean (95% confidence interval [CI]) unless otherwise noted. A one way ANCOVA was performed with baseline values as a covariate to determine whether the changes in variables (e.g., muscle thickness, 1RM, isometric, isokinetic, muscular endurance) over the 8-wk period differed by group. Statistical significance was set at P ≤ 0.05. In the event that there were not significant differences between groups, we ran tests of statistical equivalence using a 90% CI as recommended previously (34). For muscle thickness, the margin was set a priori to half of the minimal difference (e.g,. ±0.09 cm for the 70% site of the anterior upper leg). We set a priori for the performance tests to arbitrary intervals (lower body isokinetic and isometric tests: ±10 N·m; knee extension: ±3.5 kg; chest press: ±7 kg; endurance: ±3 repetitions) given that we feel test–retest for measures of performance are unable to determine tester error from actual adaptation in this population (24).
Total exercise volume (repetitions–exercise load) is presented as mean (SD) and group differences were determined by independent samples t-test. Differences in the PRS across all 16 training sessions was determined using the Mann–Whitney U test and is reported as 25th, 50th, and 75th percentiles. Hedges g was also used to quantify the between-group effect sizes for muscle size, strength, and endurance. Statistical significance was set at P ≤ 0.05.
Descriptive data are presented as mean (SD). There were no differences between groups for age (HYPER: 21 [SD, 3] vs TEST: 22 [SD, 4] yr, P = 0.562), height (HYPER: 169.3 [SD, 8.4] vs TEST: 173.5 [(SD, 8.5] cm, P = 0.134), or body mass (HYPER: 79.3 [SD, 22.6] vs TEST: 70.4 [SD, 14.4] kg, P = 0.150). For the HYPER group, there was a 98% overall compliance in the dominant and nondominant leg, and 99% overall compliance in the chest press. In the TEST group, there was 100% overall compliance for the dominant and nondominant leg and chest press exercises.
At the posterior upper arm, there were differences between groups at the 50% site for both the dominant (P = 0.019) and nondominant arms (P = 0.022) with the HYPER group having a greater change than the TEST group. At the 60% site, there were greater changes in the HYPER group for the nondominant arm (P = 0.034) but not the dominant arm (P = 0.09) (Table 1). There were no between-group differences at the 70% site for the dominant (P = 0.062) or nondominant arm (P = 0.696). For the anterior portion of the upper leg, there were differences between groups at the 50% site for both the dominant (P = 0.014) and nondominant legs (P = 0.002) with the HYPER group having a greater change than the TEST group. At the 60% and 70% sites, there were greater changes in the HYPER group for the nondominant leg (60%: P = 0.004; 70%: P = 0.003) but not for the dominant leg (60%: P = 0.064; 70%: P = 0.085) (Table 2). For the lateral portion of the upper leg, there no differences between groups for the 50%, 60%, or 70% sites (Table 2). In addition, the changes at these sites were not equivalent between groups. The pre–post change in anterior upper arm muscle thickness was not different across time for the dominant (0.00 [−0.06 to 0.06] cm, P = 0.935) or nondominant arm (−0.01 [−0.07 to 0.04] cm, P = 0.510) and represents our within participant control given that this muscle was not directly trained. Hedges g between-group effect sizes for muscle size can be found in the supplemental digital content (see Table, Supplemental Digital Content 1, between-group effect sizes for each muscle thickness measurement. http://links.lww.com/MSS/A930).
The changes observed in lower body isometric torque (dominant, P = 0.743; nondominant, P = 0.677), isokinetic torque at 60 (dominant, P = 0.199; nondominant, P = 0.137) and 180°·s−1 (dominant, P = 0.440; nondominant, P = 0.963), and isotonic strength (dominant, P = 0.344; nondominant, P = 0.141) were not different between the HYPER and TEST groups for the dominant or nondominant legs (Table 3). Further, the results of the isotonic test of the dominant leg were statistically equivalent between groups. When considering the peak 1RM achieved across visits in the TEST group, the nondominant limb also became statistically equivalent between (mean difference [90% CI]) groups (0.37, [−1.7 to 2.5] kg). For upper body strength, there were no significant differences between groups (P = 0.522) and the changes in chest press strength were found to be equivalent between (mean difference 90% CI) the HYPER and TEST groups (−1.1 [−4.2 to 1.8] kg; Fig. 1). The pre–post change in isometric torque of the elbow flexors was not different across time for the dominant (0.7 [−0.9 to 2.3] N·m; P = 0.379) or nondominant arm (−1.2 [−3.3 to 0.8] N·m; P = 0.249) and represents our within participant control given that this muscle was not directly trained. Hedges g between-group effect sizes for muscle strength can be found in the supplemental digital content (see Table, Supplemental Digital Content 2, between-group effect sizes for muscle strength and endurance, http://links.lww.com/MSS/A931).
The changes observed in lower body repetitions to failure were significantly different for the dominant (P = 0.02) leg with the HYPER group having a greater change than the TEST group. For the nondominant leg, there were no significant differences (P = 0.161) between groups and the changes were found to be statistically equivalent (Table 3). The changes observed in upper body repetitions to failure were not significantly different between groups (P = 0.184) and were found to be statistically equivalent between (mean difference 90% CI) HYPER and TEST groups (1 [0–2] repetitions; Fig. 2). In addition, the Hedges g between-group effect sizes for muscle endurance can be found in the supplemental digital content (see Table, Supplemental Digital Content 2, between-group effect sizes for muscle strength and endurance, http://links.lww.com/MSS/A931).
There were no between-group differences for changes in sEMG amplitude of the vastus lateralis for the dominant (P = 0.307) or nondominant (P = 0.497) limb. For vastus lateralis, there was a change of 92.0 (47.9–136.1) mV for the dominant limb of the HYPER group and a 59.1 (15.1–103.2) mV change for the TEST group at an adjusted prevalue of 268.3 mV. For the nondominant limb, there was a change of 84.0 (9.5, 138.5) mV for the HYPER group and a 58.1 (5.1–111.1) mV change for the TEST group at an adjusted prevalue of 257.3 mV. Similarly, there were no between-group differences for changes in sEMG amplitude of the rectus femoris for the dominant (P = 0.706) or nondominant (P = 0.706) limb. There was a change of 33.4 (0.7–66.2) mV for the dominant limb of the HYPER group and a 25.0 (−6.0 to 55.0) mV change for the TEST group at an adjusted prevalue of 240.6 mV. For the nondominant limb, there was a change of 31.1 (−10.3 to 72.6) mV for the HYPER group and a 45.1 (5.7–84.4) mV change for the TEST group at an adjusted prevalue of 235.0 mV. The pre–post change in sEMG amplitude of the elbow flexors was not different across time for the dominant (2.8 [−101.1 to 106.9] mV, P = 0.957) or nondominant arm (65.7 [−15.1 to 146.7] mV, P = 0.249) and represents our within participant control given that this muscle was not directly trained.
Perceived recovery status
The PRS was rated similarly between groups (see Table, Supplemental Digital Content 3, perceived recovery status for each training visit, http://links.lww.com/MSS/A932). There were two exceptions (visit 2 and visit 6), with the HYPER group reporting lower perceived recovery than the TEST condition.
There were between-group differences (mean 95% CI) for exercise volume of the dominant (11,049.3 [9254.6–12,844.0] kg, P < 0.001) and nondominant (10,889.8 [9231.5–12,548.0] kg, P < 0.001) leg with the HYPER group completing significantly more total volume than the TEST group (Fig. 3). There were between-group differences for exercise volume of the chest press (P < 0.001) with the HYPER group completing significantly more total volume than the TEST group (13,259.9 [9632.0–16,887.8] kg, Fig. 3). Individual plots for exercise volume can be found in the supplemental digital content for the lower body (see Figure, Supplemental Digital Content 4, individual exercise volume completed for knee extension exercise, http://links.lww.com/MSS/A933) and upper body (see Figure, Supplemental Digital Content 5, individual exercise volume completed for chest press exercise, http://links.lww.com/MSS/A934).
To provide an idea of the repetitions completed each set for the HYPER group, we provide the average repetitions for visit 9 (middle session) which is representative for the majority of training visits. On visit 9, the dominant leg completed 10 (9–10), 9 (8–9), 9 (8–10), and 9 (8–10) repetitions for sets 1, 2, 3, and 4, respectively. The nondominant leg completed 10 (9–10), 9 (8–10), 9 (9–10), and 9 (9–10) repetitions for sets 1, 2, 3, and 4, respectively. For the chest press, the HYPER group completed on average 10 (9–10), 9 (8–10), 9 (8–10), and 10 (8–11) repetitions for sets 1, 2, 3, and 4, respectively.
To determine if muscle growth is important for increasing muscle strength, we created a between subject design in which one group performed exercises to increase muscle size and strength (i.e., hypertrophy training) while the other group performed exercises to maximize strength and minimize muscle growth (i.e., practicing the test). The main findings from the current study are: 1) practicing the 1RM increases strength equivalent to a condition performing traditional high-volume training, 2) muscle size increased following a protocol to induce muscle growth while there were no changes in muscle size just performing the 1RM test, 3) there were no significant differences in isometric and isokinetic strength outcomes between groups, and 4) the HYPER group observed a greater change in muscular endurance but this was only true for the dominant leg of the knee extension exercise.
The HYPER group from the current study observed an increase in muscle size which agrees with previous observations following a high volume training protocol (25,30). There was a greater change of muscle thickness for both the dominant and nondominant limbs at the 50% site of the anterior upper leg for the HYPER group. Interestingly, at the 60% and 70% sites, only the nondominant leg saw a greater change in comparison to the TEST group (Table 2). Although both limbs are active in most activities, we hypothesize that the increase at all sites of the nondominant limb may be due to the less frequent use of this limb in daily activities making this limb more responsive compared with the dominant limb. Future research may want to consider this finding when using a within-subject design where each limb serves as a different condition as our results suggest that limb dominance may influence the changes observed. For the upper body, there were significant differences in the change in muscle thickness in the posterior upper arm at the 50% site in the dominant and nondominant arms and at the 60% site in the nondominant arm between the HYPER and TEST groups. There were no significant differences between groups at other muscle thickness sites (Table 1). This may be due, in part, to the difficulty of imaging the posterior upper arm with B-mode ultrasound. The TEST group did not observe any changes in muscle thickness indicating that some training volume is needed to induce muscle growth (Tables 1 and 2).
When observing muscular strength, both the HYPER and TEST group increased 1RM strength equivalently in the knee extension and chest press exercise despite the significant difference in total training volume and muscle growth. The results from our current study and others support that there may be a complete dissociation between muscle size and strength after a resistance training program (11,12). For example, Dankel et al. (12) had trained participants complete 21 straight days of elbow flexion exercise and observed that the daily 1RM testing condition increased strength to a similar extent to a high-volume training condition also performing the 1RM. This increased strength in the daily 1RM testing condition occurred without a change in muscle size whereas the high-volume training condition did increase muscle size. This suggested that the additional volume was necessary for growth but produced no additive effect for strength. Counts et al. (11) provide additional evidence for a potential complete dissociation between muscle hypertrophy and strength. In this study, an increase in muscle size was similar between the high-load (70% 1RM) training condition and the “No Load” (without an external load) training condition. However, the strength gains were greater in the high-load training group despite similar changes in muscle size. This dissociation between muscle size and strength becomes even more evident during a period of detraining (6). A study by Bickel et al. (6) trained individuals for 16 wk and found increases in muscle size, thigh lean mass, and strength. After detraining, skeletal muscle size and thigh lean mass decreased back to baseline levels yet muscle strength was largely maintained throughout 32 wk of detraining in a group of young participants who performed a monthly 1RM. This monthly 1RM was used to track their strength across time, yet our results would suggest that this was in fact training. If muscle growth was playing a large role with increasing strength in a resistance training program, how did a complete loss of muscle growth not meaningfully affect strength? Overall, our results and the aforementioned studies suggest that strength gains are maximized by just practicing the strength test (i.e., specificity) and that neither volume nor a change in muscle size is providing further benefit. Additionally, these findings mechanistically suggest that neurological or adaptations at the muscle level, which do not result in growth, are responsible for the training-induced increases in strength.
The HYPER group was able to perform more repetitions in the dominant leg compared with the TEST group in the lower body muscular endurance test; however, this was not observed in the nondominant leg or chest press. A previous study found that individuals who performed higher repetitions (20–28 RM) with training improved knee extension muscular endurance to a greater extent compared with individuals performing lower repetitions (3RM–5RM). However, the individuals that performed 9RM–11RM in that study did not improve muscular endurance significantly in the knee extension (10). In the current study, we used a protocol consisting of an 8RM–12RM which is a similar repetition scheme previously mentioned (10) and may not have allowed for greater improvements in muscular endurance compared with a higher repetition scheme (20RM–25RM). Also, the TEST group which only performed the 1RM was able to observe a similar change in muscular endurance for the nondominant leg as well as in the chest press exercise.
To determine if a traditional resistance training protocol produced differential strength on a movement that neither had practiced, we employed both isokinetic and isometric tests in the lower body. It has previously been suggested that multiple sets have a greater impact on isometric and isokinetic strength compared with one single set (23,30). For instance, Paulsen et al. (23) observed an increase in isometric strength after three sets of knee extension exercise compared with one single set. The authors hypothesized that the additional volume may be needed in the knee extensor muscles to increase strength based on lower body involvement in daily activities. In this study, the changes in knee extensor isometric and isokinetic strength observed in the HYPER and TEST groups were not different despite the substantial differences in exercise volume between groups. This is similar to other studies which have observed little difference in isometric strength between conditions consisting of drastically different exercise intensities and/or exercise volumes (11,12,20).
Neural adaptations have traditionally been measured through sEMG amplitude which has been found to increase after resistance training (1,15,21). The current study observed similar changes in sEMG amplitude for both training conditions which possibly could indicate that both protocols induced a similar central drive to the muscle after training. However, it should be noted that interpreting neural adaptations through estimates of sEMG amplitude should be made with caution and can be potentially misleading (4,13). Although our control condition did not change significantly over time, the variability of the change was quite large making accurate inferences improbable.
When observing PRS scores, there were no differences between groups except for visits 2 and 6 where the HYPER group displayed lower scores. It can be hypothesized that the difference for the HYPER group, particularly at visit 2, may be attributed to soreness from visit 1 due to the novel exercise stimulus. In general, the PRS scores were similar between both conditions but could hint that practicing the test may allow one to have better recovery/performance for the next bout of training.
It should be noted that there are limitations within this study. First, we used B-mode ultrasound as an assessment of muscle size which is not considered the “gold standard.” Despite this, we have reliability on the tester and previous studies appear to show that ultrasound measurement is a reliable and valid tool to measure muscle cross-sectional area compared with magnetic resonance imaging (28) and to detect change over time compared with dual-energy X-ray absorptiometry (7). Second, we did not include chest muscle thickness. Due to an all-male research team and the mixture of sexes within the study; we chose to forgo the measurement for privacy considerations. Nonetheless, we took measurements of the posterior upper arm which is involved in the chest press exercise. Third, we only examined two exercises (i.e., knee extension and chest press) in previously untrained individuals although similar results have been shown in a resistance-trained population using the bicep curl exercise (12). Fourth, we used sEMG as a rough estimate of central drive to the muscle, which is not the best method for determining this (13). Future studies could investigate this further with more sophisticated methods. Fifth, we were not powered to look at sex differences; however, we co-varied out the baseline value to make a more fair comparison on the change score. Finally, as this study was only 8 wk in duration, it remains unknown if there would be differences between the HYPER and TEST groups over a longer study duration. Notably, 8 wk is the same duration used by Moritani and DeVries (21).
This study was designed to gain a better understanding of the relationship between muscle hypertrophy and strength adaptations after a resistance training program. In summary, the current study found that practicing the 1RM strength test increased strength to an equivalent degree compared with a high-volume training condition while not observing a change in muscle size. These findings along with a previous study (12) that incorporated trained individuals further support the idea that there may be a complete disassociation between changes in muscle size and strength after resistance training. Importantly, it seems that neither volume nor the change in muscle size from training contributed to greater strength gains. If one’s main goal is to increase maximal strength, incorporating a hypertrophy day or phase within a resistance training program would seem to provide no further benefit than just lifting at or close to their 1RM.
The authors wish to express their gratitude to the participants for their dedication to this study. The authors are not aware of any affiliations, memberships, funding, or financial holdings that might be perceived as affecting the objectivity of this article.
The authors declare no conflicts of interest. The results of this study do not constitute endorsement by ACSM. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.
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