The Effect of Load Reductions on Repetition Performance for Commonly Performed Multijoint Resistance Exercises

Abstract

Willardson, JM, Simão, R, and Fontana, FE. The effect of load reductions on repetition performance for commonly performed multijoint resistance exercises. J Strength Cond Res 26(11): 2939–2945, 2012—The purpose of this study was to compare 4 different loading schemes for the free weight bench press, wide grip front lat pull-down, and free weight back squat to determine the extent of progressive load reductions necessary to maintain repetition performance. Thirty-two recreationally trained women (age = 29.34 ± 4.58 years, body mass = 59.61 ± 4.72 kg, height = 162.06 ± 4.04 cm) performed 4 resistance exercise sessions that involved 3 sets of the free weight bench press, wide grip front lat pull-down, and free weight back squat, performed in this exercise order during all 4 sessions. Each of the 4 sessions was conducted under different randomly ordered loading schemes, including (a) a constant 10 repetition maximum (RM) load for all 3 sets and for all 3 exercises, (b) a 5% reduction after the first and second sets for all the 3 exercises, (c) a 10% reduction after the first and second sets for all the 3 exercises, and (d) a 15% reduction after the first and second sets for all the 3 exercises. The results indicated that for the wide grip front lat pull-down and free weight back squat, a 10% load reduction was necessary after the first and second sets to accomplish 10 repetitions on all the 3 sets. For the free weight bench press, a load reduction between 10 and 15% was necessary; specifically, a 10% reduction was insufficient and a 15% reduction was excessive, as evidenced by significantly >10 repetitions on the second and third sets for this exercise (p ≤ 0.05). In conclusion, the results of this study indicate that a resistance training prescription that involves 1-minute rest intervals between multiple 10RM sets does require load reductions to maintain repetition performance. Practitioners might apply these results by considering an approximate 10% load reduction after the first and second sets for the exercises examined, when training women of similar characteristics as in this study.

Introduction

When performing multiple resistance exercise sets, the maintenance of a target number of repetitions has been shown to be a key factor that stimulates the development and expression of different characteristics such as maximal strength, hypertrophy, and localized muscular endurance (^{1–4,7,9,16,22}). Overall, there is an inverse relationship between the load used and the repetition maximum (RM) (³); however, the RM achievable with a given load has been shown to vary between resistance exercises that involve different muscle groups, ranges of motion, and neural recruitment patterns (³). Furthermore, several studies have indicated that when multiple RM sets are performed during a resistance exercise session, significant reductions in repetitions occur between the first set and subsequent sets, a trend demonstrated for resistance exercises that involved upper and lower body muscle groups and even when instituting up to 5-minute rest intervals between consecutive sets (^{8,9,12–14,19–22}).

This reduction in repetitions over consecutive sets has been attributed to factors such as incomplete resynthesis of phosphocreatine and insufficient time to buffer and eliminate hydrogen ions from the muscle cells (^10,15,17,18). From a practical perspective, previous authors have suggested that to maintain repetitions, there could be a need to progressively reduce the load over consecutive sets (^19–22). However, the amount of load reduction may vary based on training history and whether or not sets are being performed for submaximal repetitions or full RMs to voluntary failure, as is often practiced when emphasizing muscular hypertrophy (^{1,3,4,7,11,17,18}).

The extent of load reductions necessary to maintain repetitions has received little direct scientific examination, although previous authors stated that loads were adjusted during the course of training sessions to maintain a specified target number of repetitions per set (^{2,4,7,9,15–17}). To our knowledge, only one study to date (²²) has directly examined load reductions on the maintenance of repetitions per set. Willardson et al. (²²) involved recreationally trained men (e.g., 10RM free weight back squat was reported to be 123.55 ± 24.78 kg) and compared the repetitions per set during 4 lower body resistance exercise sessions. Three sets of the free weight back squat, leg curl, and leg extension were performed and in this exercise order during all 4 sessions. Each of the 4 sessions was conducted under different randomly ordered loading schemes, including (a) a constant 10RM load for all the 3 sets and for all the 3 exercises, (b) a 5% reduction after the first and second sets for all the 3 exercises, (c) a 10% reduction after the first and second sets for all the 3 exercises, and (d) a 15% reduction after the first and second sets for all the 3 exercises. A 1-minute rest interval was instituted between sets, and a 2-minute rest interval was instituted between exercises.

Willardson et al. (²²) reported that for the free weight back squat and leg curl, a 15% load reduction was necessary after the first set and second sets to maintain 10 repetitions; conversely, load reductions were not necessary for the leg extension. These findings were attributed to several factors, including the potentiation vs. fatiguing effects of the preceding exercise (for the leg curl and leg extension) and differences in the fatiguability of multiple muscle groups involved in the kinetic chain (for the free weight back squat).

However, Willardson et al. (²²) did not examine commonly performed multijoint exercises for the upper body such as the free weight bench press or wide grip front lat pull-down. Thus, the research question: “Are load reductions necessary for these upper body exercises when performing RM sets and lifting an absolute intensity of 10RM?” Based on the prior results of Willardson et al. (²²) for the free weight back squat, we hypothesized that load reductions for the free weight bench press and wide grip front lat pull-down would be necessary. The results and knowledge gained from further direct scientific investigation may allow coaches to determine how much of a load reduction might be necessary to maintain the repetitions per set at a specified target and thus maintain a relative 10RM intensity for each succeeding set. The ability to maintain a relative 10RM intensity and repetition performance might be more effective in stimulating adaptations associated with fatigue resistance, especially when practiced in conjunction with a short rest interval between sets (^{1–4,7,9,16,22}). Therefore, the purpose of this study was to compare 4 different loading schemes for the free weight bench press, wide grip front lat pull-down, and free weight back squat to determine the extent of progressive load reductions necessary to maintain repetition performance.

Methods

Experimental Approach to the Problem

This study was conducted over 5 weeks; during the first week, anthropometric measures (e.g., height, body mass) were collected, and 10RM tests were repeated 72 hours apart to verify reliable loads. During each of the succeeding 4 weeks, the subjects performed 1 resistance exercise session that involved performance of the following sequence: the free weight bench press, wide grip front lat pull-down, and free weight back squat. During each session, one of the following randomly ordered loading conditions was applied: (a) a constant 10RM load for all the 3 sets and for all the 3 exercises, (b) a 5% reduction after the first and second sets for all the 3 exercises, (c) a 10% reduction after the first and second sets for all the 3 exercises, and (d) a 15% reduction after the first and second sets for all the 3 exercises (Table 1). Therefore, in this study, the independent variables included the 4 loading conditions and the dependent variable was the number of repetitions completed per set.

Table 1: Example loads free weight back squat for subject with 10RM of 80 kg.*

Subjects

Thirty-two women (age = 29.34 ± 4.58 years, body mass = 59.61 ± 4.72 kg, height = 162.06 ± 4.04 cm) with at least 2 years of recreational resistance training experience participated in this study. All the subjects were characterized by the following training history: consistent participation in a resistance training program during the previous 2 years with a minimum training frequency of 3 sessions per week; 1 hour per session; 3–5 sets per exercise; 1–15 repetitions per set; and 1–2 minutes rest between sets. Furthermore, the subjects had most often used a nonlinear periodized program design and had commonly performed RM sets (to failure) as part of their training program.

The following additional exclusion criteria were adopted: (a) the subjects could not be using drugs or nutritional supplements that could affect repetition performance; (b) the subjects could not exhibit bone, joint, or muscular problems that could limit the effective execution of the exercises; (c) the subjects could not be performing any extraneous structured exercise activity for the duration of the study. All the participants read and signed an informed consent, which thoroughly explained the testing procedures; the experimental procedures were approved by the Ethics Committee of Rio de Janeiro Federal University.

Ten Repetition Maximum Testing

The subjects performed 4 sessions of familiarization; during the last 2 sessions, the 10RM for the free weight bench press, wide grip front lat pull-down, and free weight back squat were repeated 72 hours apart. The highest load achieved on either of the test days was used to structure the 4 resistance exercise sessions. No exercise was allowed in the 72 hours between the 10RM tests, so as not to interfere with the test-retest reliability. Before the 10RM tests, each subject completed 5 minutes of low-intensity aerobic activity (i.e., jogging and walking). Two warm-up sets preceded testing for each exercise at 50 and 75% of the perceived 10RM load for 10 repetitions each. After the warm-up sets, the load was increased, and a 10RM was attempted; if >10 repetitions were completed, then a 5-minute rest interval was instituted, after which another 10RM was attempted with the increased load. The increase in load for subsequent attempts (if necessary) was determined by a subject's perception of effort.

To minimize error during the 10RM tests, the following strategies were instituted: (a) standardized instructions concerning the testing procedure were given before the test; (b) the subjects received standardized instructions on exercise technique (³); (c) the subjects were verbally encouraged to continue performing repetitions during each set until the point of voluntary failure; only repetitions that involved completion of the entire range of motion were counted; and (d) the mass of all weights and bars used were determined using a precision scale. A rest interval of 5 minutes was instituted between 10RM attempts, and 10 minutes was allowed before the start of the warm-up sets for the next exercise test (^6,13).

Experimental Procedures

One week after the second 10RM test and during the succeeding 4 weeks, the subjects performed 1 resistance exercise session that involved performance of the following sequence: free weight bench press, wide grip front lat pull-down, and free weight back squat; 3 sets of each exercise were performed with 1-minute rest intervals between sets and 2-minute rest intervals between exercises. During each session, the following loading conditions were applied in random order, including (a) a constant 10RM load for all the 3 sets and for all the 3 exercises, (b) a 5% reduction after the first and second sets for all the 3 exercises, (c) a 10% reduction after the first and second sets for all the 3 exercises, and (d) a 15% reduction after the first and second sets for all the 3 exercises (Table 1). Each exercise session was performed on a consistent day and time, supervised by an experienced strength and conditioning professional.

Statistical Analyses

Intraclass correlations and paired Student's t-tests were used to assess the reliability of the 10RM tests for each exercise. A 4 (load conditions) × 3 (exercises) × 3 (sets) repeated measures analysis of variance was conducted to compare repetition performance. The Greenhouse-Geisser procedure was applied whenever the sphericity assumption was violated. Eta square effect sizes (η²) and observed power (1 − β) were calculated when appropriate. For the analyses of significant interactions, post hoc comparisons were conducted using the Bonferroni procedure. Significance for all analyses was set at p ≤ 0.05 (⁵). Statistical analyses were conducted using SPSS 16 (SPSS Inc., Chicago, IL, USA).

Results

Intraclass correlation coefficients indicated excellent reliability for the 10RM tests: bench press (r = 0.96), wide grip front lat pull-down (r = 0.96), and free weight back squat (r = 0.92). Additionally, a paired Student's t-test did not indicate significant differences between the 10RM tests for any of the exercises. The 3-way interaction among loading conditions, exercises, and sets was significant (F_12,372 = 52.45, p ≤ 0.01), but the sphericity assumption was violated (Malchly's χ² = 144.12, DF = 77, p ≤ 0.01). The Greenhouse-Geisser correction procedure was performed, and the interaction remained significant (F_6.98,216.48 = 52.45, p ≤ 0.01, η² = 0.63, 1 − β = 1.00). Then, differences among the 2-way interactions for each exercise were analyzed. The sphericity assumption was violated for each of the 2-way interactions (Malchly's χ²_squat = 68.82, DF = 20, p ≤ 0.01; Malchly's χ²_BP = 54.77, DF = 20, p ≤ 0.01; Malchly's χ²_LPD = 49.27, DF = 20, p ≤ 0.01), but they (or all three 2-way interactions) remained significant even after correction by the Greenhouse-Geisser procedure (Squat F_4.01,124.28 = 101.40, p < 0.01, η² = 0.77, 1 − β = 1.00; bench press F_3.54,109.85 = 242.59, p ≤ 0.01, η² = 0.89, 1 − β = 1.00; lat pull-down F_6.98,216.48 = 168.92, p ≤ 0.01, η² = 0.85, 1 − β = 1.00). To further investigate differences across the 2-way interactions for each exercise, post hoc Bonferroni analyses were conducted, and the results were as follows (Tables 2–4).

Table 2: Free weight back squat mean repetitions (±SD).*

Table 3: Free weight bench press mean repetitions (±SD).*

Table 4: Wide grip lat pull-down mean repetitions (±SD).*

Comparing Repetitions for Each Load across Sets

Constant Load

For all the 3 exercises, for the constant load condition, performance for the first set was significantly greater than the performance for the second and third sets; performance for the second set was significantly greater than the performance for the third set.

Five Percent Reduction

For the free weight bench press and wide grip lat pull-down, for 5% reduction condition, the performance for the first set was significantly greater than the performance for the second and third sets; for the free weight back squat, the performance for the first set was significantly greater than the performance for the third set but not significantly different from performance for the second set. For all the 3 exercises, for 5% reduction condition, the performance for the second set was significantly greater than the performance for the third set.

Ten percent Reduction

For the free weight back squat and wide grip lat pull-down, for the 10% reduction condition, the performance was the same across sets. For the free weight bench press, for the 10% reduction condition, the performance was the same between the first and second sets, but there was a significant increase from the first set to the third set and from the second set to the third set.

Fifteen percent Reduction

For all the 3 exercises, for the 15% reduction condition, the performance for the first set was significantly less than the performance for the second and third sets; for the wide grip front lat pull-down, the performance for the second set was significantly less than the performance for the third set; for the free weight back squat and free weight bench press, the performance for the second and third sets was the same.

Comparing Repetitions for Each Set across Loads

Set 1

For the free weight back squat and free weight bench press, for the first set, the performance was the same across conditions (constant, 5, 10, and 15%). For the wide grip lat pull-down, the performance for the constant load condition was significantly less than the performance for the other 3 conditions (5, 10, and 15%).

Set 2

For all the 3 exercises, for the second set, the performance was significantly greater with progressive load reductions (constant load < 5, 10, and 15%; 5 < 10 and 15; 10% < 15%).

Set 3

For all the 3 exercises, for the third set, the performance was significantly greater with progressive load reductions (constant load < 5, 10, and 15%; 5 < 10 and 15%; 10 < 15%); the only exception was for the free weight back squat with the same performance between the 10 and 15% reduction conditions.

Discussion

The key finding from this study was the necessity for load reductions after the first and second sets for all the 3 exercises to maintain 10 repetitions per set in a sample of recreationally trained women. When considering the constant load condition, the total repetitions completed over 3 sets was greatest for the free weight back squat with 25.63 repetitions performed (on average) vs. 22.15 for the free weight bench press and 16.44 for the wide grip front lat pull-down; this indicates greater fatigue resistance for the muscles of the lower body vs. the upper body.

Willardson et al. (^19,20) demonstrated a similar tendency for greater fatigue resistance of the lower body musculature in 2 studies that examined repetition performance for the free weight back squat and free weight bench press with 8RM and 15RM loads, respectively. In the first study (¹⁹), 4 sets were performed with a constant 8RM load and 1-minute rest interval between sets; a total of 22.47 and 17.13 repetitions (on average) were completed for the free weight back squat and free weight bench press, respectively. Similarly, in the second study (²⁰), 5 sets were performed with a constant 15RM load and 1-minute rest interval between sets; a total of 47.20 and 30.33 repetitions (on average) were completed for the free weight back squat and free weight bench press, respectively. In addition to the greater fatigue resistance demonstrated for the lower body musculature, a key point from each of these studies is that significant decreases in repetitions occurred from the first set to the last set for both exercises; this discrepancy may reduce the effectiveness of a resistance training program because the repetitions completed during the latter sets would hinder training volume.

Prior studies that examined the RM continuum indicated that the maintenance of a target number of repetitions is critical to achieve adaptations associated with maximal strength, hypertrophy, and localized muscular endurance (^2,4,16). Previous studies have also indicated that the load was adjusted during the course of training sessions to maintain a specified target number of repetitions per set (^{2,4,7,9,15–17}). Ratamess et al. (⁹) instituted load reductions over 5 sets of the bench press exercise when performed at 2 different intensities (i.e., 10RM and 5RM) and with 5 different rest intervals between sets (i.e., 30 seconds, 1, 2, 3, 5 minutes). Load reductions of 2.3–6.9 kg were instituted when necessary to maintain repetition performance. Ratamess et al. (⁹) demonstrated that irrespective of the intensity, the load significantly decreased with each set in succession when resting 30 seconds or 1 minute between sets. Conversely, the load was maintained over 2 sets for 2 minutes, 3 sets for 3 minutes, and 4 sets for 5 minutes. Consequently, the authors recommended that at least 2 minutes of rest might be needed to minimize load reductions and maintain repetition performance. The methods of Ratamess et al. (⁹) were different from those of this study because of load reductions instituted in absolute terms rather than in relative terms. Relative load reductions might be more appropriate to account for differences in strength levels between individuals.

A key factor that determines the ability to maintain repetitions is the recovery time between sets (^{8,9,12–14,19–22}). Several studies have demonstrated that longer rest intervals (e.g., 2–5 minutes) allowed for significantly greater repetitions and volume vs. shorter rest intervals (e.g., 30 seconds to 2 minutes) when the load was held constant over multiple sets; this was demonstrated for single exercises and multiple exercises as in a typical resistance training session (^{8,9,12–14,19–22}). Because resistance exercise prescriptions designed for hypertrophy and localized muscular endurance commonly involve moderate to high repetitions (e.g., 10–20 repetitions per set) in combination with shorter rest intervals (e.g., 30 seconds to 2 minutes between sets) (^1,3), load reductions might be necessary, especially to maintain target repetitions conducive to these training goals.

Willardson et al. (²²) conducted the only study to date to directly examine load reductions on the maintenance of repetitions. A sample of recreationally trained men performed 4 workouts with the same number of sets and loading conditions as examined in this current study. Each workout involved performance the free weight back squat, leg curl, and leg extension with 1-minute rest between sets and 2 minutes rest between exercises. The results demonstrated that a 15% load reduction after the first set and second set were necessary for the free weight back squat and leg curl to maintain 10 repetitions; conversely, load reductions were not necessary for the leg extension.

Consistent results were demonstrated in this study in that for the free weight back squat and wide grip front lat pull-down; a 10% load reduction was necessary after the first set and second sets to maintain 10 repetitions. For the free weight bench press, the load reduction was between 10 and 15%; specifically, a 10% reduction was insufficient and a 15% reduction was excessive, as evidenced by significantly >10 repetitions performed on the second set and third set for this exercise. It should be noted that progressive load reductions may reduce intensity in absolute terms but maintain intensity in relative terms because all sets were performed to repetition failure and a load reduction of 10% was necessary to maintain a relative intensity of approximately a 10RM.

The greater load reduction necessary for the free weight back squat in the previous study by Willardson et al. (²²) (i.e., 15%) vs. this study (i.e., 10%) might be accounted for because of the different training histories of samples used in each study. A key factor that determines the ability to maintain repetitions are the prescriptive variables most often practiced as part of an individual's resistance training program, with particular emphasis on the load used, the rest interval between sets, and the frequency at which sets are performed with full RMs (e.g., failure training). Kraemer et al. (⁷) demonstrated that long-term training with shorter rest intervals may lessen the need for load reductions. Nine competitive bodybuilders and 8 competitive power lifters were compared on a 10-station resistance exercise circuit. 3 sets of each exercise were performed with a 10RM load and with 10-second rest intervals between sets. A key finding was that the bodybuilders required less load reductions vs. the power lifters to maintain repetition performance for the leg press and bench press.

Kraemer et al. (⁷) concluded that the bodybuilders demonstrated greater fatigue resistance because of adaptations associated with the bodybuilding style of training (e.g., moderate to high repetitions with shorter rest intervals between sets). These adaptations may have included development of the fast glycolytic energy system and greater quantity and activity of anaerobic enzymes (e.g., phosphorylase, phosphofructokinase, and lactate dehydrogenase), thus delaying proton accumulation and metabolic acidosis (^10,15,17,18).

In summary, 10% load reductions were necessary over subsequent sets of the free weight back squat and wide grip front lat pull-down to maintain consistent repetitions; load reductions for the free weight bench press were between 10 and 15%. These results were specific to the exercises and prescription used, that is, 3 sets with an initial load of 10RM and 1-minute rest intervals between sets. Furthermore, the women used in this study could be considered recreationally trained, having performed at least 2 years of consistent resistance training with similar load intensities and rest intervals as used in this procedures. Therefore, the necessity for load reductions depends on factors such as the individual's training history, the load used, and the rest interval between sets. Future research should examine different combinations of each of these factors and whether the need for load reductions changes over time.

Practical Applications

Coaches and Fitness Professionals can readily apply the results of this investigation with women of similar training history and when using a similar resistance exercise prescription (i.e., 3 sets, 10RM load, 1-minute rest intervals between sets) for the free weight back squat, wide grip front lat pull-down, and free weight bench press. When performing multiple RM sets with short rest intervals (e.g., 30 seconds to 1 minute between sets), as is often practiced in hypertrophy or localized muscular endurance training; an advantage can be gained by applying the results of this study. A Coach or Fitness Professional could estimate the loads for each set before the workout that may allow for maintenance of target repetitions and ultimately improve the efficiency and intended outcome of a resistance training program.